An Assessment of Climate 

Change and the Vulnerability of 

Wildlife in the Sky Islands of 

the Southwest

Sharon J. Coe, Deborah M. Finch, Megan M. Friggens

United States Department of Agriculture / Forest Service

Rocky Mountain Research Station

General Technical Report RMRS-GTR-273

April 2012
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Cover photos—top: Chiricahua 

Mountains, © Larry Jones; bottom 

left: elegant trogon (Trogon elegans), 

Dominic Sherony (Wikimedia 

Commons); bottom right: bighorn 

sheep (Ovis canadensis), Terry L. 

Spivey, Terry Spivey Photography, 

Bugwood.org. Photos are authorized 

for this publication only, and any 

further use requires authorization from 

the photographers.

Coe, Sharon J.; Deborah M. Finch; Megan M. Friggens. 2012. An assessment of climate 

change and the vulnerability of wildlife in the Sky Islands of the Southwest. Gen. Tech. 

Rep. RMRS-GTR-273. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, 

Rocky Mountain Research Station. 208 p.

Abstract

We evaluated the historical and projected trends in climate and vegetation relevant to the 

Coronado National Forest in southeast Arizona, USA. We then applied this information 

in an assessment of the vulnerability of 30 species of terrestrial vertebrates on the 

Coronado National Forest to the potential effects of future climate change. We used a 

pilot version of a decision-support tool developed by the U.S. Department of Agriculture, 

Forest Service, Rocky Mountain Research Station that produces scores that represent 

relative measures of vulnerability to climate change as related to habitat, physiology, 

phenology, and biotic interactions. Over the next ~100 years, increased temperature 

and aridity are projected for the region, as well as a reduction in forested areas. All 30 

species were considered vulnerable with respect to at least some criteria comprising 

the decision-support tool. The elegant trogon (Trogon elegans) and Tarahumara frog 

(Rana tarahumarae) were tied for the largest vulnerability score. The Slevin’s bunchgrass 

lizard (Sceloporus slevini) had the smallest vulnerability score. While species varied in 

their expected responses to climate change, most appeared to be vulnerable relative to 

one or more expected negative impacts to their habitat, such as an overall reduction in 

suitable habitat. The assessment results can be used by USFS managers in climate change 

adaptation planning for these species and their habitats by helping to identify goals for 

adaptation planning.

Keywords: climate change, vulnerability assessment, wildlife management, Coronado 

National Forest, decision-support tool

Authors

Sharon J. Coe is a Postdoctoral Researcher with the USFS Rocky Mountain Research 

Station in Albuquerque, New Mexico, in collaboration with the University of Arizona. 

She holds both a Ph.D. and an M.Sc. degree in Biology from the University of California, 

Riverside. She is researching the vulnerability of wildlife to climate change and the effects 

on wildlife from vegetation treatments to reduce fire risk.

Deborah M. Finch is the Program Manager for the Grassland, Shrubland, and Desert 

Ecosystems Program at USFS Rocky Mountain Research Station in Albuquerque, New 

Mexico. She received her B.S. degree in Wildlife Management from Humboldt State 

University, her M.S. degree in Zoology and Physiology from Arizona State University, and 

her Ph.D. in Zoology and Range Science from University of Wyoming, Laramie.

Megan M. Friggens is a Research Ecologist with the USFS Rocky Mountain Research 

Station in Albuquerque, New Mexico, where she has worked on the development 

and application of tools and assessments regarding the vulnerability of species to 

climate change. She obtained a B.S. and M.S. degree in Biology from the University of 

New Mexico and a Ph.D. in Forest Science from Northern Arizona University. She is 

researching disturbance (fire, drought, land conversion, and climate change), impacts on 

wildlife species, and wildlife disease ecology.
Preface

The success and persistence of plants and animals in their natural environments is 

inextricably linked to climate. While species in North America have experienced 

historical variation in climate, a relatively rapid increase in global temperature has the 

potential to create unique environmental conditions for plant and animal species relative 

to their recent evolutionary past. Mean global surface temperature has increased over the 

last 157 years (i.e., over the instrumental record; Trenberth and others 2007). The global 

average temperature increased 0.35 °C from the 1910s to the 1940s and then 0.55 °C 

from the 1970s to the end of 2006. Temperatures are projected to increase in the United 

States, overall, and in the Southwest specifically, according to a variety of climate change 

models. There is substantial support for a projected increase in surface-air temperatures in 

the United States of 2 °C during the next century on an annual-mean basis; some models 

predict temperature increases exceeding 4 °C (Christensen and others 2007).

How to manage for the effects of climate change on plant and animal species has 

become an increasing concern for resource managers and others whose goal it is to 

maintain species viability into the future. The U.S. Forest Service (USFS) has identified 

climate change as an important force that puts ecosystems at risk. USFS (2011a) identifies 

the need for “science-based assessments of the relative vulnerability of key ecosystem 

components” to address risks and vulnerabilities of national resources. It also states the 

need to identify knowledge gaps and management outcomes under climate change. Each 

National Forest and National Grassland is required to meet standards in 11 areas related 

to climate change planning, and each is evaluated annually for achievement using a 

“scorecard” system (USFS 2011b). One criterion is education of all employees on the 

causes and impacts of climate change. Another criterion measures the extent to which 

information about the vulnerability of key resources and ecosystem elements to climate 

change is used in decision-making.

The Coronado National Forest (CNF) is located in southeastern Arizona and includes the 

Peloncillo Mountains that extend into southwestern New Mexico (Fig.1.1). The National 

Forest encompasses large areas of a group of high-elevation mountains called the Sky 

Islands. In this report, we provide information about climate change and a vulnerability 

assessment of 30 species on the CNF based on the possible effects of climate change 

over the next ~100 years. Vulnerability assessments are discussed in more detail in 

Chapter 2, but overall, they can be used to help set management priorities and to develop 

strategies for responding to climate change (“adaptation strategies;” Glick and others 

2011). Assessing vulnerability to climate change requires knowledge of possible changes 

in temperature, precipitation, and vegetation. We review these potential changes in 

Chapter 1, which is used as a basis for the species vulnerability assessment presented 

in Chapter 2. Readers who are interested primarily in a review of climate and potential 

climate-related changes in the Southwest (here, mainly Arizona and New Mexico) will 

find that information within Chapter 1. Readers who are interested primarily in the 

evaluation of species vulnerability, and not specifically the evaluation of climate, can 

proceed directly to Chapter 2. 

References

Bagne, K.E., M.M. Friggens, and D.M. Finch. 2011. A system for assessing vulnerability of 

species (SAVS) to climate change. Gen. Tech. Rep. RMRS-GTR-257. Fort Collins, CO: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Research Station. 28 p.

Christensen, J.H., B. Hewitson, A. Busuioc, [and others]. 2007. Regional climate 

projections. In: Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. 

Averyt, M. Tignor, and H.L. Miller, eds. Climate Change 2007. The Physical Science 

Basis. Contribution of Working Group I to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change. Cambridge, United Kingdom: Cambridge 

University Press.

Glick, P., B.A. Stein, and N.A. Edelson, eds. 2011. Scanning the Conservation Horizon: A 

Guide to Climate Change Vulnerability Assessment. Washington, DC: National Wildlife 

Federation. Available: www.nwf.org/vulnerabilityguide.

Trenberth, K.E., P.D. Jones, P. Ambenje, [and others]. 2007. Observations: Surface 

and atmospheric climate change. In: Solomon, S., D. Qin, M. Manning, Z. Chen, M. 

Marquis, K.B. Averyt, M. Tignor and H.L. Miller, eds. Climate Change 2007: The Physical 

i
Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change. Cambridge, United Kingdom: Cambridge 

University Press.

U.S. Forest Service [USFS]. 2011a. National roadmap for responding to climate change. 

FS-957b. Washington, DC: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/climatechange/pdf/Roadmapfinal.pdf.

U.S. Forest Service [USFS]. 2011b. Navigating the climate change performance scorecard. 

Washington, DC: U.S. Department of Agriculture, Forest Service. Available: http://fsweb.

wo.fs.fed.us/chief/climatechange/scorecard%20guidance%20document%201-21-2011.

pdf.

Acknowledgments

Funding was provided by the USFS Washington Office Research and Development. 

This work was also supported by a Joint Venture Agreement (08-JV 11221632-279) 

between the University of Arizona School of Natural Resources and the Environment 

and the Rocky Mountain Research Station. We thank Larry Jones and Rick Gerhardt on 

the Coronado National Forest for providing information on the local ecology of some 

of the species we assessed, and for helping to locate unpublished reports within USFS 

and at other resource agencies. We also thank the following individuals for providing 

unpublished documents and/or other species information: Jim Heffelfinger (Arizona Game 

and Fish Department), Jim Rorabaugh (United States Fish and Wildlife Service; Tucson, 

Arizona), and Michelle Christman (United States Fish and Wildlife Service; Albuquerque, 

New Mexico). The staff of the National Forest Service Library located numerous 

documents. Dr. Karen Bagne, Dr. Megan Friggens, and Dr. Deborah Finch developed 

the decision-support tool. Dr. Terry Rich (United States Fish and Wildlife Service) and 

Dr. Carolyn Enquist (The Wildlife Conservation Society, USA National Phenology 

Network) provided many helpful suggestions on an earlier draft of this document. David 

Hawksworth, David Trujillo, and the staff of the publishing unit of USFS Rocky Mountain 

Research Station provided helpful editing and graphics assistance.

ii
Contents

Chapter 1: A Review of Historical Trends and Projections for Future 

Change of Climate and Vegetation .....................................................................1

Introduction....................................................................................................................1

Methods..........................................................................................................................1

Results............................................................................................................................2

Temperature, Precipitation, and Hydrology.................................................................2

Extreme Weather Events..............................................................................................6

Vegetation ..................................................................................................................6

Onset of Spring...........................................................................................................8

Conditions for Species That Migrate South of the United States...................................9

Summary ........................................................................................................................9

References......................................................................................................................9

Chapter 2: An Assessment of the Vulnerability of Wildlife to Climate Change.....13

Introduction..................................................................................................................13

Methods........................................................................................................................13

Results..........................................................................................................................15

Overall Scores..........................................................................................................15

Categorical Scores....................................................................................................17

Uncertainty Scores ...................................................................................................18

Discussion ....................................................................................................................19

Management Considerations.........................................................................................24

Identifying Goals for Adaptation Planning.................................................................24

Using Assessment Results in Adaptation Planning.....................................................24

References....................................................................................................................25

Appendix A: Terrestrial Vertebrate Species Assessed............................................27

Appendix B: Species Vulnerability Assessments...................................................30
Arizona

New

Mexico

Mexico

Pima

County

Pinal

County

Cochise

County

Graham

County

Hidalgo

County

Santa

Cruz

County

Greenlee

County

Bowie

Tucson

Oracle

Bisbee

Benson

Sonoita

N Douglas ogales

Arivaca

Willcox

Safford

Tombstone

Sierra Vista

Green Valley

Huachuca

Chiricahua

Pinaleno

Galiuro

Tumacacori

Santa Catalina

Santa Rita

Peloncillo

Dragoon

Whetstone

Santa Teresa

Winchester

Coronado National Forest

Ranger Districts

Ecosystem Management Areas

Arizona New Mexico

Mexico

0 180 360 720

Miles

DISTRICT

Douglas RD

Nogales RD

Safford RD

Santa Catalina RD

Sierra Vista RD

Figure 1.1. The CNF is located in southeastern Arizona and southwestern New Mexico. Twelve EMAs are located across 

five ranger districts (RD) on the CNF.
USDA Forest Service RMRS-GTR-273. 2012. 1

Introduction

The Coronado National Forest (CNF) encompasses portions of multiple mountain ranges that are part of a sky island 

archipelago located where the Rocky Mountains converge 

with the Sierra Madre Occidental of Mexico. Sky islands are 

mountain ranges separated by low-lying valleys that can act 

as barriers to movement by some species. There are roughly 

26 sky island complexes worldwide (Warshall 1995). The 

Madrean sky island region is located in the southwestern United States (southeastern Arizona and southwestern 

New Mexico) and northwestern Mexico. The north-south 

orientation produces climatic variation that is absent in archipelagos that are oriented east-west (e.g., Great Basin; 

Warshall 1995). The Madrean archipelago provides a “stepping stone” between the Rocky Mountains and plateaus to 

the north and the Sierra Madre plateau and its mountains 

to the south (Warshall 1995). Within the United States, the 

Madrean sky islands are noted for their high floral diversity (McLaughlin 1995). It is here that the Holoarctic and 

Neatropic floral provinces meet, as do the Neotropic and 

Nearctic faunal realms (Warshall 1995).

Within the United States it is likely that the southwest 

will experience some of the greatest extremes in temperatures and aridity as a result of climate change. Northern 

regions of North America are expected to experience the 

greatest warming during winter, but in southwestern areas, 

warming is expected to be greatest in summer (Christensen 

and others 2007). Annual mean precipitation is also likely 

to decrease, whereas in Canada and the northeastern United 

States, rainfall is expected to increase. Increased aridity in 

the Madrean sky islands is expected to have negative consequences for its flora and fauna. To address possible impacts 

to vertebrate species (see Chapter 2), we identified expected 

or possible changes in climate and vegetation for the CNF 

through a combination of literature review, online tools, and 

vegetation projections.

Methods

The CNF consists of 720,340 ha divided into twelve 

Environmental Management Areas (EMAs; Fig.1.1) between ~33°3’ and 31°20’ latitude. Elevation on CNF ranges 

from 914 m to 3267 m (3000 ft. to 10,720 ft.). The twelve 

EMAs coincide primarily with the mountain ranges that 

they encompass. The exceptions are the Tumacacori EMA, 

which includes both the Tumacacori Mountains and the 

Pajarito Mountains, and the Huachuca EMA, which includes the Huachuca Mountains, the Canelo Hills, and the 

Patagonia Mountains. Major vegetation community types 

on CNF, from lowest elevation to highest, are Sonoran and 

Chihuahuan desert, semi-desert grassland, interior chaparral, 

Madrean encinal woodland, Madrean pine/oak woodland, 

ponderosa pine, mixed conifer forest, and spruce-fir forest 

(USFS 2009). The two plant communities that comprise the 

greatest area are semi-desert grassland (~26% of total area) 

and Madrean encinal woodland (~42%). Three major riparian plant communities are recognized: cottonwood willow, 

mixed broadleaf deciduous, and montane willow.

We reviewed scientific literature regarding historical 

trends in climate and vegetation that were applicable to 

Arizona and the southwestern United States, and we modeled projections for the Twenty-first Century. We used an 

online tool called “Climate Wizard” for both historical 

climate data, and for projections of temperature and precipitation (http://www.climatewizard.org/; data downloaded 

August 2009). Historical data in Climate Wizard were developed using the PRISM (Parameter-elevation Regressions 

on Independent Slopes Model) climate mapping system. 

Projections in Climate Wizard used the ensemble of three 

General Circulation Models: MIROC3.2 (medres), CSIROMK3.0, and UKMO-HadCM3.

We used projections of vegetation change in the western 

United States that were generated by Rehfeldt and others 

(2006) as predictors of possible change within CNF. This 

approach predicts where suitable climate for various plant 

communities will exist in the future based on current climate associations of plant communities. Rehfeldt and others 

(2006) used multivariate regression tree models to predict changes in total area with suitable climate for Brown 

vegetation communities (Brown 1998) using: (1) plant 

presence-absence data, (2) an algorithm called “Random 

Forests,” and (3) input from a climate model at 1-km resolution. They used climate variables that were related to summer 

and winter temperatures, measures of available moisture, 

length of frost-free season, and the interaction between temperature and precipitation. The IPCC IS92a scenario (1% 

increase in greenhouse gases per year after 1990) was used 

as well as the average of two General Circulation Models 

(HadCM3GGA1 and CGCM2_ghga). We created maps of 

current vegetation (Year 2005) and projected change (Year 

2090) in suitable climate for vegetation for each EMA on 

the CNF in ArcMap 9.3 using raster images produced by 

Rehfeldt and others (2006) (available from http://forest.

moscowfsl.wsu.edu/climate/customData/) and shapefiles 

for each of the ranger districts using boundary data obtained 

from the USFS (“Administrative_ Boundaries” available 

from http://www.fs.fed.us/r3/gis/cor_gis.shtml). For each of 

the eight vegetation communities identified, we calculated 

the percent area of suitable climate for year 2005 and year 

2090.

For information on possible future conditions in Mexico, 

Central America, and South America, where migratory 

Chapter 1: A Review of Historical Trends and Projections for Future Change of 

Climate and Vegetation
2 USDA Forest Service RMRS-GTR-273. 2012.

species spend part of the year, we relied on published literature sources. Obtaining climate change information for areas 

utilized outside of the CNF was complicated by the fact that 

specific over-wintering areas and migratory routes of most 

species are generally not well known. We focused on general 

projections for large geographic areas.

Results

Temperature, Precipitation, and Hydrology

Historical trends

Considering large-scale trends in temperature, global 

mean surface temperatures have risen by almost 1 °C in the 

last 100 years (0.74 ± 0.18 °C over the period 1906-2005 

when estimated by a linear trend; Trenberth and others 2007). 

In the last 50 years, the rate of warming has been roughly 

twice that. The greatest warming over land has occurred in 

winter (December-February) and in spring (March-May) in 

the Northern Hemisphere. In mid-latitude regions, there has 

been a reduction in the number of frost days and daily cold 

extremes and an increase in the number of warm extremes 

(Trenberth and others 2007).

Temperature in Arizona fluctuates seasonally with the 

coldest temperatures occurring in mid-winter and the hottest occurring in mid-summer (Sheppard and others 2002). 

Along the southern portion of the state, mean annual temperatures increase from west to east, as well as from high to 

low elevation. A combination of paleo-climate records and 

modern records (i.e., from weather stations that began recording temperature in the mid- to late-1800s) indicate that 

the recent warming trend in the southwestern United States 

is unprecedented in the last 400 years (Sheppard and others 

2002), with the warmest year in the Twentieth Century being 1934 (Sheppard and others 1999). In the Sonoran Desert, 

between 1960 and 2000, winter and spring temperatures increased, the frequency of freezing temperatures decreased, 

and minimum winter temperatures increased (Weiss and 

Overpeck 2005). Local land use and multi-decadal modes 

(e.g., Pacific Decadal Oscillation, or PDO) did not appear 

to have driven these warming trends. According to Climate 

Wizard, over the latter half of the Twentieth Century, most 

of the CNF experienced an increase in winter temperature 

(December-February; Fig. 1.2).

Precipitation in Arizona and New Mexico falls primarily 

in the summer and winter; spring and fall are often comparatively dry. The North American monsoon is an important 

precipitation phenomenon, bringing as much as 50% of 

the annual rainfall to Arizona and New Mexico from July 

through September (Sheppard and others 2002). Moisture 

from oceanic sources leads to convective storms when conditions in the Southwest cause air masses to rise. The timing 

of precipitation from monsoons varies seasonally, annually, 

and decadally. Inter-annual variation results, in part, from 

the relative location of the Bermuda subtropical ridge; a 

northward shift in the ridge is associated with wet summers 

in Arizona (Sheppard and others 1999). The effect of the 

El Niño-Southern Oscillation (ENSO) on monsoonal patterns is unclear (Sheppard and others 2002). The penetration 

of tropical hurricanes in late summer and fall from farther 

south and west can also bring large amounts of rainfall over 

large areas of the Southwest in a relatively short period. 

In winter, a second peak of precipitation occurs, generally 

between November and March, falling as snow at high elevations. Winter climate variability is influenced by a number of 

phenomena, including the Pacific/North American pattern, 

Southwestern troughing, ENSO, and PDO. See Sheppard 

and others (2002) for a review.

Historical trends in precipitation in the Southwest differ depending on which months of the year, which years, 

and what regions are considered. From 1900 to 2005, in 

the southwestern United States, northwestern Mexico, and 

Baja Peninsula, there was a trend of decreasing annual precipitation (1-2% per decade) based on Global Historical 

Climatology Network data from the National Climatic 

Data Center (Trenbreth and others 2007). This contrasts 

with a general increase in precipitation over much of North 

America over the same period and based on the same data 

source (Trenbreth and others 2007). Using a different data 

set (based on a global network called “CRU TS2.1”) and 

looking at only the latter half of the century (1950-2000), 

Wang and others (2009) reported that in much of Arizona, 

mean precipitation increased in all seasons except for the 

June to August period. Regonda and others (2005) found 

that many recording stations in Arizona showed increases 

in the amount of winter precipitation. Anderson and others 

(2010) reported no trend for changes in summer monsoonal 

precipitation from July to September in Arizona from 1931 

to 2000; increases were observed in areas to the north in 

Utah and Colorado, which are considered outside of the core 

monsoonal region.

Large among-year variation in precipitation has been 

observed in the Southwest. For example, a “seasonal precipitation reversal” occurred in the mid-2000s in Arizona 

(Goodrich and Ellis 2008). The second wettest winter on 

record in Arizona occurred in 2004/2005 and ameliorated 

a drought that had been ongoing in some parts of the state 

since 1996. This very wet year was followed in 2005/2006 

by the driest winter in the instrumental record for most regions in Arizona since 1895. The authors noted a trend for 

increasing variability in inter-annual winter precipitation in 

Arizona, particularly since the 1960s.

Recurrent droughts are common in the mid-latitudes, 

including North America. Globally, droughts have become 

more common since the 1970s, as measured by the Palmer 

Drought Severity Index (Trenbreth and others 2007), which 

uses precipitation, temperature, and local water content 

data to assess soil moisture. Decreased precipitation on 

land and increased temperatures have contributed to more 

areas experiencing drought. Diminished snowpack in the 

western United States also appears to have contributed to 

a reduction in moisture availability. According to McCabe 

and others (2004), over the coterminous United States, 

52% of the spatial and temporal variance in multidecadal 

drought frequency is explained by the PDO and the Atlantic 
USDA Forest Service RMRS-GTR-273. 2012. 3

Multidecadal Oscillation (AMO), with 22% being attributable to a “complex spatial pattern of positive and negative 

trends in drought occurrence possibly related to increasing 

Northern Hemisphere temperatures or some other unidirectional climate trend.” The authors found that droughts in the 

1990s were associated with a North Atlantic warming (positive AMO) and a northeastern and tropical cooling (negative 

PDO).

Drought is considered a normal phenomenon in the 

Southwest (Weiss and others 2009). The effects of ENSO 

modulate drought conditions on inter-annual and decadal 

timeframes (Cook and others 2009). When sea surface 

temperatures in the eastern tropical Pacific are lower than 

normal (also known as “La Niña”), conditions in the southwestern United States are drier than normal. Over the last 

approximately 100 years, the most notable droughts in the 

Southwest occurred in (1) the late 1890s and early 1900s, 

(2) the 1950s, and (3) the early 2000s (Seager and others 

2005; Trenberth and others 2007; Weiss and others 2009). 

La Niña conditions were present in the Southwest drought of 

the 1950s and at the beginning of the Twenty-First Century; 

additional conditions at that time included the cold phase 

of the PDO, the warm phase of the AMO, and the positive 

phase of the Eastern Pacific Oscillation (EPO; Quiring and 

Mean annual change (°C) per year

-0.052 - -0.02

-0.019 - -0.003

-0.002 - 0

0.0005 - 0.0133

0.138 - 0.02

0.020 - 0.027

0.027 -0.036

0.036 - 0.063

Santa Teresa

Pinaleno

Winchester

Chiricahua

Dragoon

Peloncillo

Galiuro

Huachuca

Whetsone

Santa Rita

Santa Catalina

Tumacacori

0 45 90 Kilometers

±

Figure 1.2. Winter temperatures 

(December-February) in southeastern 

Arizona increased over 1951-2006. 

Many areas within the CNF showed 

warming trends. Source: Climate 

Wizard (www.climatewizard.org).
4 USDA Forest Service RMRS-GTR-273. 2012.

Goodrich 2008). Tree ring data in the Upper Colorado River 

Basin (including portions of Wyoming, Utah, Colorado, 

Arizona, and New Mexico) indicated that the more recent 

drought from 1999 to 2004 was the seventh worst for that 

area in approximately 500 years (Piechota 2004).

Changes in flow in rivers and streams also have been 

documented in the western United States, including reduced snowpack in winter (Knowles and others 2006) and 

earlier peak streamflow in spring (Cayan and others 2001). 

Regonda and others (2005) found that many streams in 

snowmelt-dominated river basins in the western United 

States from 1950 to 1999 showed advances in peak spring 

flows, including a site located in central-eastern Arizona. 

The trend for earlier streamflow in the western United States 

(Stewart and others 2005) has been most apparent from 1947 

to 2003 (Hamlet and others 2007). An analysis of changes 

in 14 free-flowing, snowmelt-dominated rivers in the Rocky 

Mountains of Canada and the United States during various periods in the 1900s showed that winter season flows 

(December to March) were often slightly increased, but the 

larger effect was a decrease in summer flows (Rood and others 2008). Spring peak flow was often earlier and larger. In 

the Sierra Nevada of California, April to July streamflow has 

decreased since the 1950s; in contrast, autumn streamflow 

has increased (Aguado and others 1992).

Projected changes

Temperatures are projected to increase in the United 

States overall, and in the Southwest specifically, according 

to a variety of climate change models. There is substantial 

support for a projected increase in U.S. surface-air temperatures of 2 °C during the next century on an annual-mean 

basis; however, some models predict temperature increases 

exceeding 4 °C (Christensen and others 2007). Increases 

in summer temperatures are expected to be the largest in 

the Southwest. Fewer frost days across the United States 

are also predicted, and the lowest winter temperatures are 

likely to increase more than average winter temperatures. 

Dominguez and others (2010) indicated that there is growing 

consensus that the Southwest will become drier and hotter in 

the coming century, and that there will be an amplification 

of aridity during La Niña conditions. Storms may become 

more intense but less frequent, resulting in an overall increase in aridity (Trenberth and others 2005). According to 

Climate Wizard, under the A2 and A1B emission scenarios (IPCC 4th Assessment) and the “ensemble average” of 

models MIROC3.2 (medres), CSIRO-MK3.0, and UKMOHadCM3, temperatures in the region encompassing the CNF 

are projected to rise by a few degrees Celsius relative to 1961 

to 1990 in each of four seasons from 2049 to 2069 (Fig. 1.3). 

This is generally consistent with IPCC projections for the 

Southwest (Christensen and others 2007). Temperature projections under the A1B scenario based on 22 Global Climate 

Models downscaled to the Southern Colorado Plateau (includes northern Arizona) predicted increased mean annual 

temperatures through the year 2100 by as much as 4 °C 

(Garfin and others 2009). The 22-model average projected 

temperatures increasing above the Twentieth Century average by 2.2 °C by 2030.

Reduced annual rainfall in the Southwest is predicted 

(Table 1.1) as well as reduced moisture availability and 

reduced snowpack in areas that typically receive snowfall. 

Climate Wizard (under the A2 and A1B emission scenarios and the “ensemble average” of MIROC3.2 (medres), 

CSIRO-MK3.0, and UKMO-HadCM3) generally projected 

precipitation decreases for the period 2049 to 2069 (relative 

to 1961 to 1990), with the largest decreases projected for 

spring (Fig. 1.4). The 22-model ensemble average by Garfin 

Season

Dec-Feb Mar-May Jun-Aug Sep-Nov

Projected temperature increase (deg C)

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

A2 emissions, ensemble 

A1B emissions, ensemble 

Figure 1.3. Temperature 

increases projected for 

southeastern Arizona for 

the period 2049-2069 

as compared to the 

baseline period 1961-

1990, based on analysis 

by Climate Wizard (www.

climatewizard.org) under 

two IPCC emissions 

scenarios (A2 and A1B) 

and using the ensemble 

average for General 

Circulation Model (models 

used in ensemble average: 

MIROC3.2 [medres], 

CSIRO-MK3.0, and 

UKMO-HadCM3).
USDA Forest Service RMRS-GTR-273. 2012. 5

Condition predicted for future

Region

Source Comments

U.S.

Southwestern 

U.S.

Other

Less precipitation X Christensen and 

others 2007

In the Southwest, less rainfall in winter (DecemberFebruary) and summer (June-August), which contrasts with projections of increased precipitation in 

northeastern North America.

X Seager and others 

2007

Based on a multimodel ensemble mean, climate 

becomes drier and shows a continued drying trend 

beginning in the late 1900s and early 2000s. 

X Garfin and others 

2009

Based on a 22-model ensemble average, precipitation 

expected to decline in the southern Colorado Plateau. 

Greater aridity and 

increased droughts

X Seager and others 

2007

Dryness evaluated in terms of precipitation minus 

evaporation. Predict that “future droughts...will be 

worse than any since Medieval period.”

X Field and others 

2007

Increased evaporation due to higher temperatures.

Reduced snowpack X Christensen and 

others 2007

General decrease in snow depth from delayed autumn 

snowfall and earlier melting in spring. Some models 

may underestimate warming in high altitudes in western U.S. associated with snow-albedo feedback.

Reduced summer 

stream flow

X Field and others 

2007 

Projected for mountain snowmelt-dominated watersheds.

Table 1.1. Projected changes in moisture-related phenomena in the United States.

Season

Dec-Feb Mar-May Jun-Aug Sep-Nov

Projected reuduction in precipitation (%)

0

10

20

30

40

50

A2 emiss.,ensemble 

A1B emiss., ensemble

B1 emiss., ensemble 

Figure 1.4. Precipitation 

changes projected for 

southeastern Arizona 

for the period 2049-

2069 as compared to 

the baseline period 

1961-1990, based on 

analysis by Climate 

Wizard (www.

climatewizard.org) 

under three IPCC 

emissions scenarios 

(A2, A1B, and B1) and 

using the ensemble 

average for General 

Circulation Model 

(models used in 

ensemble average: 

MIROC3.2 [medres], 

CSIRO-MK3.0, and 

UKMO-HadCM3). We 

used values for the 

area encompassing the 

Huachuca EMA, and 

expect that values for 

the other EMAs would 

be similar.
6 USDA Forest Service RMRS-GTR-273. 2012.

and others (2009) projected a 6% decrease in annual precipitation by the end of the 2000s. The authors found that 

agreement among a subset of the 22 Global Climate Models 

was greatest for the May to June period, with rainfall projected to decline by 11 to 45% during the Twenty-First 

Century. Output from individual models varied more than 

for temperature, differing in the magnitude and direction 

of projected precipitation changes. This was possibly due 

to some of the Global Climate Models modeling historical 

climate poorly. Dominquez and others (2010) indicated that 

all of the models used in the IPCC AR4 significantly overestimate winter precipitation and do not simulate well the 

precipitation associated with the North American Monsoon.

Extreme Weather Events

Historical trends

One analysis of temperature patterns in North America 

since the 1960s found that in Arizona, there has been a trend 

for fewer cold days (i.e., the number of days above the 90th

percentile of minimum temperature; Peterson and others 

2008). The authors also found a trend for heavier rainfall 

in some parts of Arizona, and a trend for lighter rainfall in 

other areas.

Tropical cyclones (also known as hurricanes) develop 

mainly in the tropics over large bodies of warm water and 

lose strength as they pass over land, although heavy rains 

can fall inland. In late summer and early fall, rainfall from 

tropical cyclones can reach the Southwest when tropical cyclones in the eastern Pacific Ocean penetrate northeastward 

(Sheppard and others 2002). Most tropical storms that bring 

rainfall to Arizona are from storms in the eastern Pacific 

Ocean. However, the majority of tropical storms in the 

eastern Pacific do not track into the Southwest (Corbosiero 

and others 2009). From 1958 to 2003, one to three tropical cyclones and their remnants affected the Southwest each 

year, typically in September (Corbosiero and others 2009). 

It is estimated that “direct impacts” (which include heavy 

rainfall) from a tropical storm occur, on average, every 4.5 

years in Arizona, but “indirect impacts” occur more frequently (Carter 2002). The western portions of Arizona are 

most likely to be affected. The number of tropical storms 

that impact Arizona does not appear to be greater in El Niño 

years (Carter 2002), although other characteristics of tropical cyclones may be (Carter 2002; Corbosiero and others 

2009). High rainfall from tropical cyclones has been associated with extreme flooding events in Arizona (e.g., Tropical 

Storm Norma in September of 1970) and with much-needed 

rainfall during times of drought (e.g., Tropical Storm Olivia 

in October 2000).

Globally, there has been a trend of longer cyclone storm 

lifetime and greater storm intensity since approximately 

1970 (Trenberth and others 2007), and the North Pacific 

Ocean is one of the top three oceanic areas with the largest increases in cyclone severity. The frequency of cyclones 

in winter (November to March) in mid-latitudes (30-60°N) 

decreased over the period 1959 to 1997, although the intensity of cyclones increased in both mid- and high latitudes 

(McCabe and others 2001). Emanuel (2005) found that since 

the mid-1970s, there has been a trend of longer storm lifetimes and greater storm intensities. A review of data from 

1970 to 2004 for six ocean basins that support tropical cyclones found no clear linear trend in the number of cyclone 

days but observed a decadal oscillation, particularly in the 

number of storm days (Webster and others 2005). The exception was the North Atlantic Ocean, which showed a 

significant increase in frequency and duration commencing 

in 1995, possibly associated with global warming.

Projected changes

Projections by Diffenbaugh and Ashfaq (2010) based on 

a large number of climate model experiments under the A1B 

scenario showed a potential for a significant increase in the 

number of times the historical hottest-season temperature 

threshold will be exceeded over the next 30 years throughout the United States. In the western United States, an 

increase in the frequency and duration of heat waves is expected (Christensen and others 2007). Assuming a doubling 

of CO2 over pre-industrial levels, most hydrologic basins in 

California are predicted to experience an increase in “extremely hot days” (i.e., days in which the daily maximum 

temperature is above the 95th percentile of daily maximum 

temperatures in each year, which corresponds to the 18th

hottest maximum in a year) and an increase in periods of 

prolonged extreme temperature or “hot spells” (i.e., the 

maximum temperature exceeds the long-term 95th percentile 

for seven or more days; Bell and others 2004).

Tebaldi and others (2006) examined the potential for 

increases in precipitation intensity on a global scale under 

the A1B emissions scenario. Globally, the mid-latitudes 

and high-latitudes of the northern hemisphere showed a 

statistically significant increase in precipitation intensity. 

Areas including the Southwest were outside of this range 

and interpretation was less clear. Emanuel (2005) predicted 

that hurricane intensity will increase under global climate 

change, but noted that predictions regarding hurricane frequency are inconsistent. Webster and others (2005) cited six 

studies that modeled cyclone patterns under doubled CO2

levels that gave contradictory results, although most predicted increased hurricane intensity.

Vegetation

Historical trends

Changes in temperature and precipitation can affect 

vegetation communities in a variety of ways, including 

vegetation mortality, changes in phenology, changes in 

competitive ability, and shifts in range. Globally, multi-year 

droughts have been linked to tree mortality (Allen and others 

2010). A rapid increase in tree mortality rates in the western United States in unmanaged forests in recent decades 

could not be attributed solely to aging of large trees, and 

higher ambient temperature was considered a likely contributor (Van Mantgem and others 2009). In northern New 

Mexico in the 1950s, there was a large shift (of 2 km or 

more) in the ecotone between semi-arid ponderosa pine forest and piñon-juniper woodland in less than five years as a 
USDA Forest Service RMRS-GTR-273. 2012. 7

result of ponderosa pine mortality associated with severe 

drought (Allen and Breshears 1998). From 2002 to 2003, 

a regional-scale die-off in woodlands in the Southwest was 

associated with drought and beetle infestations (Breshears 

and others 2005). At one study site, more than 90% of piñon 

pine (Pinus edulis) died following 15 months of depleted 

soil water content. During the drought years of 1942 to 1957 

(considered the most extreme in the Southwest in the past 

400 years), there was wide-ranging mortality of plants in 

shrublands, woodlands, and forests; there also was an increase in the rate at which shrubs encroached into grasslands 

(Swetnam and Betancourt 1998). In contrast, a 20-ha study 

site in Chihuahuan Desert in southeastern Arizona where 

grazing was excluded showed an increase in the density of 

woody shrubs since the 1970s that was attributed to an increase in winter precipitation (Brown and others 1997).

Changes in temperature and precipitation can lead to 

changes in the range of plant species along altitudinal gradients. In the Santa Catalina Mountains of southeastern 

Arizona, Crimmins and others (2009) recorded flowering 

dates of several hundred plant species over the period 1984 

to 2003. Ninety-three species (25.6%) showed a significant 

shift in flowering range between the first half and the latter 

half of the study period. A variety of responses was observed: some species’ flowering range shifted upslope, some 

expanded upslope (increase in range), others contracted 

upslope, and still others expanded downslope. These changes 

coincided with a general warming in most seasons between 

the first half and the latter half of the 20-year study period. 

Plants at higher elevations in the Santa Catalina Mountains 

responded differently to climate variables than species at 

lower elevations (Crimmins and others 2007). From 1984 to 

2003, the diversity of species in bloom at lower elevations 

was strongly related to precipitation, whereas at high elevations, it was heavily influenced by temperature.

Generally, there has been a trend in the United States 

of increased forest fire activity, including on USFS lands 

(Stephens 2005). The recurrence of regionally synchronized 

fires over many centuries in the Southwest demonstrates that 

climate plays an important role in fire patterns, although fuel 

accumulation as a result of fire suppression beginning in the 

early 1900s has also contributed to fire activity (Swetnam 

and Betancourt 1998). There was an increase in the area 

over which stand-replacing fires occurred between 1984 and 

2006 in portions of California and Nevada, and an increase 

in mean and maximum fire size and the area burned annually (Miller and others 2009). The patterns in California and 

Nevada appeared to be related to hotter air temperatures 

and reduced precipitation. The forested area that burned between 1987 and 2003 in the western United States (including 

Arizona) was 6.7 times more than that burned from 1970 

to 1986 (Westerling and others 2006) and the mean length 

of the fire season increased by 78 days in the latter period 

compared to the earlier period (1970-1986). The increase 

in fires was associated with an increase in temperature and 

earlier snowmelt; of the 34 years studied, years with earlier 

snowmelt had five times more wildfires than those with later 

snowmelt. Littell and others (2009) found that in the western 

United States, “wildfire area burned” (WFAB, or total hectares burned) over a variety of vegetation types from 1916 

to 2003 showed strong associations with climate. WFAB in 

mountainous ecoprovinces showed strong relationships with 

low precipitation, low Palmer Drought Severity Index, and 

high temperature, whereas in grass- and shrub-dominated 

ecoprovinces, WFAB showed strong relationships to precipitation levels the preceding winter. The authors indicated 

that although fire suppression and fuel treatments likely had 

an influence on area burned, climate had a significant affect.

On the CNF, fire exclusion has been associated with a 

high density of small-diameter trees in ponderosa pine forest, 

mixed conifer forest, and spruce-fir forest and shrub invasion in semi-desert grasslands (USFS 2009). Furthermore, 

vegetation communities have been altered for long periods 

after fire. Following a severe crown fire in Madrean oakpine woodland in southeast Arizona (i.e., 10-ha Rattlesnake 

Fire) oaks resprouted more and oak seedlings grew faster 

than pine, which the authors expected to cause a shift to a 

more homogenous oak woodland (Barton 2002).

Projected changes

Experiments, including those that increase CO2 levels, 

provide some insight into how plants may respond to changing abiotic conditions. The effects of changes in CO2

 have 

been shown to vary with precipitation. In the Mojave Desert, 

three species of shrubs significantly increased above-ground 

production in response to experimentally elevated CO2 in 

one year with anomalously high rainfall but not in three 

years with below-average rainfall (Housman and others 

2006). New shoot production by a dominant shrub under 

elevated CO2 was not enhanced in a drought year but was 

enhanced in a high rainfall year, and above-ground production was higher for an exotic annual grass than for native 

annuals, which the authors suggested might lead to higher 

dominance of that species (Smith and others 2000).

Increased insect outbreaks that lead to increased tree mortality are projected for forests in North America (Logan and 

others 2003; Field and others 2007; Bentz and others 2010). 

Based on the 2002/2003 regional-scale die-off in Southwest 

woodlands associated with drought and beetle infestations, 

Breshears and others (2005) projected more severe and extensive die-offs should air temperatures continue to rise. 

Insect outbreaks leading to vegetation mortality are already 

considered a threat to multiple vegetation communities on 

CNF (USFS 2009), and this threat is likely to worsen.

Changes in the timing of stream peak flow have the potential to alter conditions for riparian plant species. Based on 

observations of an earlier spring peak flow and reduced summer and autumn flows in 14 rivers in the Rocky Mountains, 

Rood and others (2008) predicted a possible mismatch between seasonal flow and both seedling establishment and 

seed release. A decline in late summer flows was thought to 

be one of the greater, if not greatest, impacts to floodplain 

forests, potentially imposing drought stress along reaches 

in arid and semi-arid regions, with a likely negative impact 

on willows (Salix spp.) and cottonwoods (Populus spp.). 

The effect of earlier peak flow on flooding regimes and 
8 USDA Forest Service RMRS-GTR-273. 2012.

establishment of riparian vegetation is expected to vary by 

site and be difficult to predict (Poff 2002).

Using the Rehfeldt vegetation models, we projected 

for year 2090 a decline in the amount of total area on the 

CNF that would possess suitable climate for Madrean forest 

and woodland and Madrean conifer forest, and an increase 

in area with suitable climate for semi-desert grassland 

(Fig. 1.5). Projected change in area with suitable climate for 

other communities, which occur in much smaller proportion, 

are as follows: a slight increase for Sonoran desert scrub, 

and a slight decrease for Chihuahuan desert scrub, plains 

grassland, interior chaparral, and Rocky Mountain conifer forest (Fig. 1.5). We considered possible explanations 

for why the area for Sonoran desert scrub was projected to 

increase yet Chihuahuan desert scrub was projected to decrease. Similarly, area for plains grassland was expected 

to decrease yet semi-desert grassland was projected to increase. Possible explanations are measurement error relating 

to the large scale of the analysis, and the small scale of the 

units that desert scrub and plains grasslands comprise in this 

study.

Projected changes in vegetation for a portion of the 

Saguaro National Park in Tucson, Arizona, were similar 

qualitatively to those predicted by our analysis with the 

Rehfeldt models, although the vegetation categories were 

somewhat different (Kupfer and others 2005). Assuming a 

temperature rise of 4 °C and either no change in precipitation, a 10% decrease, or a 10% increase, both desert scrub 

and desert savanna/grassland were projected to increase, and 

Madrean woodland and forest and montane conifer forest 

were expected to decrease.

Forest fires are expected to increase under future climate change, and riparian areas are expected to continue to 

be threatened by high intensity fire. Flannigan and others 

(2000) modeled an index of forest fire potential for North 

America under a scenario of doubling of CO2 levels. For two 

different GCMs, Arizona showed an increase in the index of 

fire potential. Vegetation communities on CNF are already 

considered at risk from fire (USFS 2009). High intensity fire 

is a threat to woodlands, forests, and riparian areas, and high 

frequency fires are a concern in chaparral.

Onset of Spring

Changes in the onset of spring in North America are expected (Field and others 2007). In the western United States, 

first blooming dates for common purple lilac (Syringa 

vulgaris f. purpurea Hort. Ex Schelle) and honeysuckle 

(Lonicera tatarica cv., “Arnold Red,” and L. korolkowii 

stopf, var. zebelli) and the spring pulse in snow-fed streamflow have been earlier since the 1970s, coincident with 

warmer-than-average spring temperatures (Cayan and others 

2001). Over the period from 1950 to 1999 there were significant trends for earlier timing of the spring warm spell in the 

western United States (defined as the seven-day period when 

daily maximum temperatures were above 12 °C), including 

at several weather stations in Arizona (Regonda and others 

2005). The flowering dates of shrubs in the northern Sonoran 

Desert advanced from 1894 to 2004 (Bowers 2007).

In the Santa Catalina Mountains of southeastern Arizona, 

over the period 1984 to 2003, the onset of flowering in plant 

species at low elevations was driven most frequently by temperature and precipitation during the prior autumn, whereas 

at high elevations first flowering was more frequently associated with spring temperatures (Crimmins and others 2010). 

Approximately 10% of species showed a significant shift in 

date of first flowering over the study period, with most tending toward a later onset. The authors suggested that some 

species may have shown later onset as a result of decreased 

autumn precipitation, whereas others may have responded to 

a slight decrease in spring temperature.

Reports of earlier phenology in North American fauna 

include earlier dates of calling in several species of frogs 

in New York from 1990 to 1999 compared to 1900 to 1912 

Figure 1.5. Proportion 

of eight vegetation 

communities 

estimated as 

occurring on the CNF 

and the proportion of 

area predicted to have 

suitable climate for 

the eight communities 

by year 2090 using 

models developed by 

Rehfeldt and others 

(2006).

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

current

2090
USDA Forest Service RMRS-GTR-273. 2012. 9

(Gibbs and Breisch 2001); species included gray treefrog 

(Hyla versicolor), spring peeper (Pseudacris crucifer), 

American bullfrog (Rana catesbeiana), and wood frog 

(Rana sylvatica). Blaustein and others (2001) found that 

some species of frogs in North America have shown a trend 

toward earlier breeding while others have not.

Conditions for Species That Migrate South 

of the United States

In general, increased temperatures are projected for 

Central America (Magrin and others 2007: Fig. 13.1 and 

Table 13.4). Observed trends in rainfall for Central America 

vary, with increases in some areas and decreases in others (Magrin and others 2007: Fig. 13.1). In South America 

(Magrin and others 2007), temperature increases are occurring in many areas (and glaciers have retreated in Columbia, 

Peru, and Ecuador). Northern areas are expected to become 

drier and tropical forests are expected to be replaced by savannahs with a general increase in risk of fire; southern areas 

are expected to become more suitable for tropical vegetation. In southern Mexico, between 1960 and 2004, average 

and maximum temperatures increased and were generally 

unrelated to ENSO or PDO (Peralta-Hernandez and others 

2009). In this same study, a slight non-statistically significant decrease in precipitation was observed.

Summary

Overall, we provided support for the likelihood of the following key environmental changes on the CNF: increased 

average annual temperature and temperature extremes; reduced average annual precipitation, including a reduction 

in snowfall and snowpack, changes to the timing of peak 

stream flow, particularly those fed directly by snowmelt; increased wildfire activity; and a reduction in riparian forest 

and woodlands.

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USDA Forest Service RMRS-GTR-273. 2012. 13

Introduction

The process of identifying what types of climate change 

impacts are likely to be experienced by ecosystems, plant 

communities, and/or species can help to focus decisions 

regarding conserving natural resources under a changing 

climate. Rowland and others (2011) summarized some of 

the approaches that have been used to evaluate potential impacts on animal species, including: (1) using observations of 

paleoecological data (past 1000-10,000 years) and/or more 

recent data (Twentieth Century) to evaluate changes in distributions of species as correlated with climate; (2) species 

distribution modeling (e.g., bioclimatic envelope modeling, 

and niche modeling) to predict the future range of a species 

relative to changes in climate and/or distributions of plant 

species on which a species depends; and (3) vulnerability 

indices to identify the relative vulnerability of species. Each 

approach has benefits and limitations. While niche modeling can produce very useful information for how species’ 

distributions may change (Peterson and others 2002; Preston 

and others 2008), the method can be relatively data intensive and requires application of analytical methods that may 

go beyond the time available to resource managers. Field 

experiments that manipulate water, temperature, and/or CO2

levels (Smith and others 2000; Housman and others 2006; 

Mikkelsen and others 2008) provide insight into how vegetation may change but are generally the purview of research 

scientists, not resource managers. Vulnerability indices (of 

the type described by Rowland et al. 2011) tend to rely on 

existing data and can be less quantitatively intensive. They 

can be applied to geographic units, species’ habitats, and 

species themselves, and are set in a framework that explicitly considers sensitivity and exposure to climate change.

The IPCC defines vulnerability (Schneider and others 

2001) as the extent to which a system (or species) is susceptible to sustaining damage from climate change; vulnerability 

is considered to be a function of sensitivity and exposure to 

climate change as well as adaptive capacity. Sensitivity refers to the degree to which a system or species will respond 

to a given change in climate, whereas exposure is the degree to which a species or system is expected to experience 

projected changes in climate. Adaptive capacity refers to the 

degree to which a species or system can reduce or moderate 

the potential impact of climate change. A resilient system or 

population is one that is not sensitive to climate variability 

and change and has the capacity to adapt.

Glick and others (2011) described the results of several 

case studies that used vulnerability indices. Application of 

NatureServe’s Climate Change Vulnerability Index to 216 

species in Nevada identified several relatively common 

species (e.g., American pika [Ochotona princeps], bighorn sheep, and sagebrush vole [Lemmiscus curtatus]) as 

vulnerable to climate change. Another assessment using the 

U.S. Environmental Protection Agency’s Threatened and 

Endangered Species Vulnerability Framework evaluated 

six Federally listed vertebrate species and categorized each 

into one of three different levels of vulnerability to climate 

change.

Our goal was to assess the relative vulnerability of 30 

vertebrate species on CNF to assist wildlife managers in 

on-going efforts to set conservation priorities under climate 

change. However, our results also may be of interest to efforts for species conservation on other public and private 

lands in the region. We used a vulnerability index system 

that was a pilot of a decision-support tool developed by 

USFS Rocky Mountain Research Station. It produced scores 

reflecting relative measures of vulnerability to climate 

change with respect to habitat, physiology, phenology, and 

biotic interactions.

Methods

The 30 vertebrate species we assessed (Appendix A) were 

identified by CNF biologists (R. Gerhardt and L. Jones) as 

being high priority for assessing vulnerability. These species 

had one or more of the following designations: (1) USFS 

Species of Concern, (2) USFS Species of Interest, (3) species 

that are otherwise of concern to USFS, (4) Federally listed 

as Endangered or Threatened species under the Endangered 

Species Act, (5) Federal Species of Concern; (6) federal 

Candidate for Listing, (7) Federal “under review” species. 

By taxonomic grouping, the 30 species consisted of 8 birds, 

13 mammals, 5 reptiles, and 4 amphibians. Twenty-nine of 

the 30 species are known to occur on CNF. The mesquite 

mouse (Peromyscus merriami) potentially occurs on CNF 

based on known nearby locations (Jones, personal communication). We evaluated vulnerability by considering species 

on all relevant EMAs simultaneously (i.e., we did not assess 

vulnerability separately for each EMA). Two species—the 

American bullfrog and the Abert’s squirrel (Sciurus aberti; Fig. 2.1)—are of concern because they are not native to 

CNF and potentially, or are known to, compete with native 

species.

We used a pilot version of a decision-support tool called 

a System for Assessing Vulnerability of Species (SAVS). 

SAVS was developed by the USFS Rocky Mountain 

Research Station to assess the vulnerability of terrestrial 

vertebrates to climate change (Bagne and others 2011). It 

consists of 25 questions based on criteria or factors that are 

expected to predict relative vulnerability to climate change. 

Questions, and their multiple choice options, are grouped 

into four categories as they relate to habitat, physiology, phenology, and biotic interactions (Fig. 2.2; Appendix B). Each 

question addresses one or two of the following aspects of 

Chapter 2: An Assessment of the Vulnerability of Wildlife to Climate Change
14 USDA Forest Service RMRS-GTR-273. 2012.

Figure 2.1. The Abert’s squirrel (Sciurus 

aberti) is native to northern Arizona but 

was introduced to the CNF. The species 

is considered a potential competitor 

of the Mount Graham red squirrel 

(Tamiasciurus hudsonicus grahamensis), 

a Federally listed endangered species. 

Photo: Sally King, National Park Service 

(Wikimedia Commons).

HABITAT

• Breeding habitat area

• Non-breeding habitat area

• Habitat components required for 

breeding season

• Habitat components required for 

non-breeding season

• Habitat quality and reproductive 

success

• Habitat quality and survival

• Ability to colonize new areas

• Use of migratory or transitional 

areas

PHYSIOLOGY

• Impacts to physiological tolerances

• Temperature-dependent sex 

determination

• Exposure to extreme weather

• Limitations to daily active period

• Metabolic energy savings (torpor, 

hibernation)

• Type of metabolism and ability to 

store energy 

• Alternative life history strategies

• Lifespan 

PHENOLOGY

• Use of temperature and moisture 

cues

• Reproduction and survival relative 

to resource availability (event 

timing)

• Separation of cues relative to 

resource availability (mismatch 

potential)

• Number of breeding attempts per 

year

BIOTIC INTERACTIONS

• Impacts on primary food resources 

if not a diet generalist

• Changes to predation levels if 

limited diversity of predators

• Changes in symbiotic relationships

• Potential for change in disease

incidence causing widespread 

mortality

• Changes to influence of competitors

Figure 2.2. A summary of 

the factors (and their 

grouping into four 

categories) used in the 

vulnerability assessment.
USDA Forest Service RMRS-GTR-273. 2012. 15

vulnerability: exposure, sensitivity, and/or adaptive capacity. For each question, one multiple-choice option is selected 

by the user, with each option having a different point value. 

Responses that are considered to reflect vulnerability to climate change have a positive point value; those considered 

to reflect resilience to climate change have a negative point 

value. Responses considered to reflect “no affect” (or neither 

a benefit nor a cost) from climate change have a point value 

of zero. For our study, a single biologist (S. Coe) assessed 

all 30 species.

For each species, we calculated a score using responses 

from all questions (called an “overall score”) and a separate 

sub-score for each of the four categories (called a “categorical score”). Possible overall scores ranged from -20 to 

+20, and possible categorical scores ranged from -5 to +5. 

Formulas that we used to calculate these scores adjusted for 

different numbers of questions within each category. For a 

given species, a positive overall score (and a positive categorical score) resulted when more multiple-choice responses 

were chosen that had positive values than negative values. 

A score of zero was obtained either when all questions were 

scored a zero or when the positive point totals offset the 

negative point totals.

An uncertainty score accounted for variation in the 

amount of data used (i.e., available data) to answer each 

question. We scored uncertainty for each category in the following way: zero points when information was available for 

most questions in the respective category; one point when 

information was available for some questions or when most 

of the information used was from similar species; and two 

points if there was little information for the species or similar species beyond broad generalizations. We summed the 

uncertainty scores in each category to create an overall uncertainty score. The uncertainty values are distinct from the 

vulnerability scores.

For species-specific biological information, we used published literature sources obtained by searching the Web of 

Science® database of primary literature using the name of 

each species and/or sub-species. We also used unpublished 

agency documents and conference proceedings, as these 

sources often contained important information specific to 

populations in Arizona and/or the Southwest.

We assessed vulnerability of species on the CNF assuming that the following changes are likely to occur, based on 

the results of our climate change review (see Chapter 1):

• An increase in average temperature, including an 

increase in winter minimum temperatures;

• An increase in the frequency of temperature extremes 

(although the precise frequency, intensity, and duration 

of such events remains unclear);

• A reduction in snowpack (greater fraction of winter 

precipitation falling as snow);

• An increase in aridity and drought as a result of reduced 

average precipitation, altered precipitation regimes, and/

or an increase in evaporation relative to precipitation;

• Alterations to the timing of peak stream flows in spring, 

particularly in streams that occur in snowmelt drainages, 

and reduced average stream flow during other times of 

year;

• An increase in the frequency and intensity of wildfire;

• A reduction in riparian, forest, and woodland 

communities; a possible increase in semi-desert 

grassland.

With respect to impacts from wildfire, we considered direct loss of habitat and did not include direct mortality of 

species from fire or smoke. Given the uncertainty in projections for precipitation intensity by Meehl and others (2005; 

see Chapter 1), we did not assume increases in precipitation 

intensity. For each long-distance migratory species, we present in Appendix B the information used to evaluate potential 

impacts to non-breeding habitats. Our assessment focused 

on the direct impacts of climate change on species; we did 

not incorporate potential impacts from anthropogenic responses that may occur in response to planning for climate 

change (e.g., increases in wind turbines for wind energy to 

reduce greenhouse gas emissions).

Results

Overall Scores

We calculated overall scores using all 25 questions; possible scores ranged from -20 to +20. Actual overall scores 

ranged from +9.9 to -0.4 (Fig. 2.3 and Table 2.1). Twentynine of the 30 species assessed received overall scores >0. 

More than half of the species (67%) had a score >+5.0, which 

is roughly the mid-point in the range of scores received. The 

two species with the largest scores were the elegant trogon 

(Fig. 2.4) and Tarahumara frog (Fig. 2.5)—both received 

an overall score of +9.9. They both received positive scores 

(“vulnerable”) on 13 questions, a score of zero (“neutral”) 

on 10 questions, and negative scores (“resilient”) on 2 questions, but they differed on which questions they were scored 

vulnerable.

The lowest-scoring species were the mesquite mouse and 

desert bighorn sheep (Ovis canadensis mexicana), which 

both received +1.3, and Slevin’s bunchgrass lizard (-0.4). 

Slevin’s bunchgrass lizard received negative scores (“resilient”) on 7 questions, positive scores (“vulnerable”) on 

7 questions, and a score of zero (“neutral”) on 11 questions.

The highest scores were not limited to a single taxonomic 

category. Species with the highest ~30% of the scores (i.e., 

≥+7.0) consisted of one or more species in each of the four 

taxonomic categories—birds, mammals, reptiles, and amphibians. The taxonomic group with the highest average 

overall score was birds (+7.4), followed by amphibians 

(+6.9), mammals (+5.0), and reptiles (+3.9).

The five species with the largest overall scores (Fig. 2.3) 

are associated with riparian habitat. However, additional 

species use riparian habitat, such as the Sonoran tiger salamander (Ambystoma tigrinum stebbinsi) and the American 

bullfrog, and received lower scores (+4.4 and +3.7, 

respectively).
16 USDA Forest Service RMRS-GTR-273. 2012.

Slevin’s bunchgrass lizard

Elegant trogon

Tarahumara frog

Northern gray hawk

Chiricahua leopard frog

Western yellow-billed cuckoo

Northern buff-breasted flycatcher

Northern Mexican gartersnake

Gould’s wild turkey

Chiricahua fox squirrel

Northern goshawk

Coues’ white-tailed deer

Abert’s squirrel

Arizona gray squirrel

Montezuma quail

Townsend’s big-eared bat

White-bellied long-tailed vole

Mexican long-tongued bat

Western red bat

Arizona ridge-nosed rattlesnake

Mount Graham red squirrel

Allen’s lappet-browed bat

Sonoran tiger salamander

American bullfrog

Giant spotted whiptail

Western yellow bat

American peregrine falcon

Desert tortoise (Sonoran)

Desert bighorn sheep

Mesquite mouse

-5 0 5 10 15

Figure 2.3. Vulnerability scores 

(“overall scores”) for the 30 

species assessed on the CNF. 

Colors indicate taxonomic 

category (birds = red, 

mammals = black, reptiles 

= purple, and amphibians = 

green).

Figure 2.4. The elegant trogon (Trogon elegans) had the 

largest vulnerability score of the bird species assessed and 

was tied with Tarahumara frog (Rana tarahumarae) for 

the largest vulnerability score of the 30 species. Photo: 

Dominic Sherony (Wikimedia Commons).

Figure 2.5. The Tarahumara frog (Rana tarahumarae) had 

the largest vulnerability score of the amphibian species 

assessed and was tied with the elegant trogon for the 

largest vulnerability score of the 30 species. Photo: Jim 

Rorabaugh, U.S. Fish and Wildlife Service (Wikimedia 

Commons).
USDA Forest Service RMRS-GTR-273. 2012. 17

Categorical Scores

We calculated categorical scores for each of the four categories; possible scores ranged +5 to -5. The average score 

and range in the first three categories across all species were 

as follows:

• habitat = +2.3; +4.0 to -2.3 (Fig. 2.6; Table 2.1);

• physiology = +0.9; +2.9 to -0.8 (Fig. 2.7; Table 2.1);

• phenology = +1.4; +5.0 to -3.0 (Fig. 2.8; Table 2.1).

In the biotic interactions category, only three values 

were obtained: +1.0, 0.0, and -1.0 with an average of +0.2. 

Within the habitat, physiology, and phenology categories, 

the majority of species received scores >0 (27 species, 21 

species, and 23 species, respectively).

In the habitat category, which had the highest average 

score, the Chiricahua leopard frog (Rana chiricahuensis) 

received the highest score (Figs. 2.6 and 2.9). The species 

with the lowest score was Slevin’s bunchgrass lizard (-2.3). 

The highest average score by taxonomic group was for amphibians (+2.9), followed by mammals (+2.7), birds (+2.1), 

and reptiles (+1.3). All bird and mammal species had scores 

>0 except for the American peregrine falcon (Falco peregrinus anatum; Fig. 2.10) and desert bighorn sheep (Fig. 2.11). 

Three of the four reptiles also scored >0 (Fig. 2.12A), as did 

all amphibians (Fig. 2.12B).

Species Overall Score

Categorical Scores

Habitat Physiology Phenology

Biotic interactions

Elegant trogon 9.9 2.9 2.1 5.0 0.0

Tarahumara frog 9.9 3.5 2.9 2.1 0.0

Northern gray hawk 9.2 2.4 2.1 3.8 1.0

Chiricahua leopard frog 9.0 4.0 2.9 -0.8 0.0

Western yellow-billed cuckoo 8.4 2.4 2.1 3.8 0.0

Northern buff-breasted flycatcher 8.4 2.4 2.1 3.8 0.0

Northern Mexican gartnersnake 8.3 3.5 1.4 2.1 0.0

Gould’s wild turkey 7.6 2.9 2.1 -0.4 1.0

Chiricahua fox squirrel 7.5 3.4 0.7 0.8 1.0

Coues’ white-tailed deer 6.8 3.4 0.7 1.3 0.0

Northern goshawk 6.8 2.4 2.1 0.8 0.0

Arizona gray squirrel 6.7 3.4 0.7 0.8 0.0

Abert’s squirrel 6.7 3.4 0.7 0.8 0.0

Montezuma quail 6.0 0.9 2.1 2.1 1.0

Townsend’s big-eared bat 5.4 2.4 -0.8 2.1 1.0

White-bellied long-tailed vole 5.3 2.5 0.7 -0.4 1.0

Western red bat 5.2 2.9 -0.7 2.5 0.0

Mexican long-tongued bat 5.2 1.9 -0.7 3.8 1.0

Arizona ridge-nosed rattlesnake 5.2 2.5 0.0 2.1 0.0

Mount Graham red squirrel 5.1 3.4 -0.7 0.8 0.0

Sonoran tiger salamander 4.4 1.5 0.7 2.1 0.0

Allen’s lappet-browed bat 4.4 2.9 -0.7 0.8 0.0

American bullfrog 4.3 2.4 0.7 -0.8 0.0

Giant spotted whiptail 3.7 2.5 0.0 -0.8 0.0

Western yellow bat 3.6 2.4 -0.7 0.8 0.0

Desert tortoise (Sonoran) 2.9 0.5 0.7 2.1 0.0

American peregrine falcon 2.9 -0.1 2.1 2.5 -1.0

Mesquite mouse 1.3 2.5 -0.7 -3.3 0.0

Desert bighorn sheep 1.3 -0.1 1.4 -0.4 0.0

Slevin’s bunchgrass lizard -0.4 -2.3 1.4 2.1 0.0

Table 2.1. Vulnerability scores (overall and categorical) for species assessed on CNF (n = 30). Possible overall scores range 

-20 to 20. Possible scores in four categories (habitat, physiology, phenology, and biotic interactions) range -5 to 5. 
18 USDA Forest Service RMRS-GTR-273. 2012.

In the physiology category, the Tarahumara frog and the 

Chiricahua leopard frog were tied for the highest score (+2.9; 

Fig. 2.7). Both of these species were scored as “vulnerable” 

for five of the eight criteria, “neutral” for two criteria, and 

“resilient” on one criterion (see respective species accounts, 

Appendix B). The pattern of scores was notably different 

from those in the habitat category, with eight of the 21 species having a very small positive score (+0.71; Fig. 2.7 and 

Table 2.1). The highest average score by taxonomic group 

was for birds (+2.1), followed by amphibians (+1.8), reptiles 

(+0.7), and mammals (0.0). All bird and amphibian species 

had scores >0 (Figs. 2.10 and 2.12B, respectively), whereas 

roughly half of the mammals had scores <0 (Fig. 2.11), and 

two of the five reptiles received a score of 0 (Fig. 2.12A).

The phenology category had the second-highest average 

score after the habitat category. The elegant trogon received 

the largest score (+5.0; Fig. 2.8), and the mesquite mouse 

received the smallest score (-3.3). The highest average score 

by taxonomic group was received by birds (+2.3), followed 

by reptiles (+1.5), mammals (+0.8), and amphibians (+0.6). 

All but 1 bird species received a score >0, as did 10 of 13 

mammals, 4 of 5 reptiles, and 2 of 4 amphibians.

In the biotic interactions category, most species (n = 22) 

obtained a score of 0.0, seven species scored 1.0, and one 

scored -1.0 (American peregrine falcon). Birds and mammals had an average score of 0.3, and amphibians and 

reptiles had an average score of 0.0.

Uncertainty Scores

Uncertainty scores were not incorporated into vulnerability scores, but rather, helped to identify the relative 

amount of information used to select responses in each 

category, which, in turn, identified where further information or research could prove beneficial. Possible scores for 

uncertainty ranged from 0 to 8, with higher scores indicating greater uncertainty. In our study, scores for uncertainty 

for each species ranged from 0 to 7 (Table 2.2). Desert bighorn sheep was scored a 0 and Mexican long-tongued bat 

(Choeronycteris mexicana) was scored a 7. The mean uncertainty score was 2.6.

For most species, uncertainty was lowest in the habitat 

category. Within this category, one criterion for which there 

was often no information was “habitat quality” (relating 

variation in habitat quality to variation in reproductive success and survival). Also, there was uncertainty for questions 

Slevin’s bunchgrass lizard

Elegant trogon

Tarahumara frog

Northern gray hawk

Chiricahua leopard frog

Western yellow-billed cuckoo

Northern buff-breasted flycatcher

Northern Mexican gartersnake

Gould’s wild turkey

Chiricahua fox squirrel

Northern goshawk

Coues’ white-tailed deer

Abert’s squirrel

Arizona gray squirrel

Montezuma quail

Townsend’s big-eared bat

White-bellied long-tailed vole

Mexican long-tongued bat

Western red bat

Arizona ridge-nosed rattlesnake

Mount Graham red squirrel

Allen’s lappet-browed bat

Sonoran tiger salamander

American bullfrog

Giant spotted whiptail

Western yellow bat

American peregrine falcon

Desert tortoise (Sonoran)

Desert bighorn sheep

Mesquite mouse

-5.0 -3.0 -1.0 1.0 3.0 5.0

Figure 2.6. Vulnerability scores in the habitat category for the 

30 species assessed on the CNF.

Slevin’s bunchgrass lizard

Elegant trogon

Tarahumara frog

Northern gray hawk

Chiricahua leopard frog

Western yellow-billed cuckoo

Northern buff-breasted flycatcher

Northern Mexican gartersnake

Gould’s wild turkey

Chiricahua fox squirrel

Northern goshawk

Coues’ white-tailed deer

Abert’s squirrel

Arizona gray squirrel

Montezuma quail

Townsend’s big-eared bat

White-bellied long-tailed vole

Mexican long-tongued bat

Western red bat

Arizona ridge-nosed rattlesnake

Mount Graham red squirrel

Allen’s lappet-browed bat

Sonoran tiger salamander

American bullfrog

Giant spotted whiptail

Western yellow bat

American peregrine falcon

Desert tortoise (Sonoran)

Desert bighorn sheep

Mesquite mouse

-5.0 -3.0 -1.0 1.0 3.0 5.0

Figure 2.7. Vulnerability scores in the physiology category for the 

30 species assessed on the CNF.
USDA Forest Service RMRS-GTR-273. 2012. 19

Slevin’s bunchgrass lizard

Elegant trogon

Tarahumara frog

Northern gray hawk

Chiricahua leopard frog

Western yellow-billed cuckoo

Northern buff-breasted flycatcher

Northern Mexican gartersnake

Gould’s wild turkey

Chiricahua fox squirrel

Northern goshawk

Coues’ white-tailed deer

Abert’s squirrel

Arizona gray squirrel

Montezuma quail

Townsend’s big-eared bat

White-bellied long-tailed vole

Mexican long-tongued bat

Western red bat

Arizona ridge-nosed rattlesnake

Mount Graham red squirrel

Allen’s lappet-browed bat

Sonoran tiger salamander

American bullfrog

Giant spotted whiptail

Western yellow bat

American peregrine falcon

Desert tortoise (Sonoran)

Desert bighorn sheep

Mesquite mouse

-5.0 -3.0 -1.0 1.0 3.0 5.0

Figure 2.8. Vulnerability scores in the phenology category for the 30 

species assessed on the CNF.

Figure 2.9. The Chiricahua leopard frog received 

the highest score for vulnerability in the 

habitat category. Photo: Jim Rorabaugh, 

U.S. Fish and Wildlife Service (Wikimedia 

Commons).

related to non-breeding habitat for migratory species because 

the wintering locations of migratory species are typically not 

well known, and climate projections for Mexico, Central, 

and South America were broad-scale in scope.

For most species, there was also a lack of information for 

questions in the physiology category. For example, we found 

little information in the published literature on the ability of 

species to deal with heat extremes and drought in natural settings. For the criteria in the category of biotic interactions, 

there was little information on competitors of individual species. Also, for most species, the literature suggested that a 

suite of predators existed. Many, if not most, species were 

identified as susceptible to a variety of diseases, but we 

found few reports of widespread mortality from the many 

diseases that species potentially experience, and there was 

relatively little information projecting how climate change 

might alter the prevalence of the diseases identified.

Discussion

Our assessment of 30 species showed that most species have vulnerability according to the multiple criteria 

comprising the assessment system we used, and all species 

had vulnerability in some areas. Even the species with a 

negative overall score (<0)—the Slevin’s bunchgrass lizard—was scored as vulnerable for seven criteria. In general, 

species with the largest overall scores were associated with 

riparian habitat, which is expected to decline with increasing 

temperatures. However, not all species associated with riparian habitat had the largest overall scores.

It is difficult to predict what the relative importance of 

different traits to a species’ survival will be under climate 

change. Criteria in the questionnaire each had equal, or 

roughly equal, weight. However, in reality, one or more criteria may exert a disproportionate influence on a species’ 

survival relative to other criteria. Furthermore, additional 

factors that influence species’ vulnerability under climate 

change likely exist. Thus, small differences in scores may 

or may not reflect large differences in actual vulnerability. The ranking of species by scores (as we presented in 

graphical and tabular format) can be used to guide further 

investigations regarding the specific areas of vulnerability 

of a species or set of species. Ranks should not, however, 

be assumed to predict the relative probability of population decline. Rather, scores on individual questions should 
20 USDA Forest Service RMRS-GTR-273. 2012.

interactions

phenology

physiology

habitat

Elegant trogon

Northern gray hawk

Western yellow-billed cuckoo

Northern buff-breasted flycatcher

Gould’s wild turkey

Northern goshawk

Montezuma quail

American peregrine falcon

-5 -3 -1 1 3 5

Figure 2.10. Vulnerability scores within each category for species of birds assessed on the CNF.

Chiricahua fox squirrel

Coues’ white-tailed deer

Abert’s squirrel

Arizona gray squirrel

Townsend’s big-eared bat

White-bellied long-tailed vole

Mexican long-tongued bat

Western red bat

Mount Graham red squirrel

Allen’s lappet-browed bat

Western yellow bat

Desert bighorn sheep

Mesquite mouse

-5 -3 -1 1 3 5

interactions

phenology

physiology

habitat

Figure 2.11. Vulnerability scores within each category for species of mammals assessed on the CNF.
USDA Forest Service RMRS-GTR-273. 2012. 21

Figure 2.12. Vulnerability scores within each category for species of (A) reptiles and (B) amphibians 

assessed on the CNF.

interactions

phenology

physiology

Slevin’s bunchgrass lizard habitat

Northern Mexican gartersnake

Arizona ridge-nosed rattlesnake

Giant spotted whiptail

Desert tortoise (Sonoran)

-5 -3 -1 1 3 5

interactions

phenology

physiology

habitat

Tarahumara frog

Chiricahua leopard frog

Sonoran tiger salamander

American bullfrog

-5 -3 -1 1 3 5

(A)

(B)
22 USDA Forest Service RMRS-GTR-273. 2012.

be examined and considered in terms of how each criterion 

potentially contributes to vulnerability or resilience. For example, the elegant trogon and Tarahumara frog both had the 

same overall score and the same number of questions for 

which they were scored as vulnerable, but their categorical 

scores differed, thus reflecting differences in the criteria for 

which they were considered vulnerable.

The fact that the largest overall scores were not limited to 

a single taxonomic category suggests that traits of individual 

species, not just of major taxonomic groups, were important 

contributors to vulnerability scores. For example, the two 

species with the largest overall scores were from different 

taxonomic groups. Also, the two reptiles with the largest 

overall scores—northern Mexican gartersnake [Thamnophis 

eques megalops] and Arizona ridge-nosed rattlesnake 

[Crotalus willardi willardi])—each had overall scores closer 

to species of mammals and birds than to each other or to 

other reptiles.

Within the habitat category, the Chiricahua leopard frog 

received the highest score in part due to its dependence 

on standing water during the breeding season and its low 

dispersal tendency. Low dispersal ability was a trait common to all of the amphibians and contributed to that group 

having the highest average score, as did the expectation 

that habitat for three of the four species will decline. The 

fourth amphibian—Sonoran tiger salamander—was projected to experience some habitat loss (a decline in Madrean 

oak woodland) and some increase in habitat (expansion of 

Species Overall Uncertainty 

Score

Uncertainty Score Within Category

Habitat Physiology Phenology Biotic interactions

Elegant trogon 3 0 2 0 1

Tarahumara frog 2 0 2 0 0

Northern gray hawk 4 0 2 0 2

Chiricahua leopard frog 4 0 2 1 1

Western yellow-billed cuckoo 2 0 1 0 1

Northern buff-breasted flycatcher 5 1 2 1 1

Northern Mexican gartnersnake 3 0 1 1 1

Gould’s wild turkey 1 0 1 0 0

Chiricahua fox squirrel 4 0 1 2 1

Coues’ white-tailed deer 2 0 1 1 0

Northern goshawk 1 0 1 0 0

Arizona gray squirrel 2 0 1 0 1

Abert’s squirrel 1 0 1 0 0

Montezuma quail 3 0 2 0 1

Townsend’s big-eared bat 3 0 1 1 1

White-bellied long-tailed vole 4 1 1 1 1

Western red bat 4 1 1 1 1

Mexican long-tongued bat 7 2 2 1 2

Arizona ridge-nosed rattlesnake 4 0 1 1 2

Mount Graham red squirrel 3 0 1 1 1

Sonoran tiger salamander 1 0 1 0 0

Allen’s lappet-browed bat 4 1 1 1 1

American bullfrog 1 0 1 0 0

Giant spotted whiptail 5 1 1 1 2

Western yellow bat 4 1 1 1 1

Desert tortoise (Sonoran) 1 0 1 0 0

American peregrine falcon 2 0 1 1 0

Mesquite mouse 5 2 1 1 1

Desert bighorn sheep 0 0 0 0 0

Slevin’s bunchgrass lizard 4 0 1 1 2

Table 2.2. Uncertainty scores for species assessed on CNF (n=30). Possible scores within a category are 0, 1, or 2, for a possible total 

uncertainty score ranging from 0 to 8
USDA Forest Service RMRS-GTR-273. 2012. 23

grasslands). Similarly, a high average score for mammals 

was influenced by a predicted decline in habitat for 12 of the 

13 species (the exception being the desert bighorn sheep). 

In contrast to the amphibians, the mammals were considered to be good dispersers and, thus, able to move to new 

areas in response to changes in habitat, with the exception of mesquite mouse and white-bellied long-tailed vole 

(Microtus longicaudus leucophaeus). Among birds, the only 

species for which habitat was projected not to decrease was 

the American peregrine falcon, a species that occupies a 

variety of habitat types. The only bird species that was considered vulnerable due to low dispersal was the Montezuma 

quail (Cyrtonyx montezumae). All five reptiles were considered poor dispersers, and habitat for three was projected 

to decrease. Projected increases in grasslands are expected 

to provide some benefit to the Slevin’s bunchgrass lizard. 

The Sonoran desert tortoise (Gopherus agassizii, Sonoran 

population) was scored as “neutral” with respect to habitat 

changes given the potential for an increase in desert scrub.

In the physiology category, the Tarahumara frog and the 

Chiricahua leopard frog had the largest scores and were considered vulnerable on the same criteria. Factors contributing 

to their vulnerability were the potential for: (1) a drier environment to lead to reduced over-wintering survival and 

reduced activity periods, (2) mortality from an increase in 

spring flooding, and (3) multi-year droughts to reduce the 

success and/or number of breeding events across years. The 

existence of terrestrial and aquatic adult forms in the Sonoran 

tiger salamander was considered a life history strategy that 

might confer an advantage when resources and climate conditions are variable. The bird species also showed many 

areas of vulnerability in the physiology category, and all 

were considered vulnerable on the same criteria, including 

the inability of these species to conserve energetic resources 

by undergoing torpor, their relatively short lifespan, and their 

endothermic physiology. The lack of alternative life history 

strategies had a neutral effect on their scores. Uncertainty 

regarding potential behavioral responses to increases in 

temperature reduced our capacity to predict physiological 

thresholds and effects on activity periods. Also, had there 

been more certainty with respect to predictions related to an 

increase in hurricane frequency, we would have considered 

this potential extreme weather pattern a threat to the bird 

species that migrate long distances to the south.

As with birds, the uncertainty regarding possible behavioral coping responses to high temperature led us to assign 

neutral scores for the squirrels, bats, and rodents for questions regarding physiological thresholds and changes in 

activity periods. Heat stress in summer has been documented 

as an important issue for desert bighorn sheep. It is possible that Coues’ white-tailed deer (Odocoileus virginianus 

couesi), another large ungulate, would have similar physiological issues, although their use of more wooded habitats 

may help to reduce their exposure. The ability of the bat and 

squirrel species to reduce metabolic demands through torpor 

or other means of inhibiting metabolism was considered an 

advantage. The Mount Graham red squirrel (Tamiasciurus 

hudsonicus grahamensis) is reported as able to store food 

in the long term, which may reduce its vulnerability to energetic issues associated with climate-related reductions in 

food resources; it is the only genus of tree squirrel in North 

America that stores substantial quantities of food. Lastly, 

scores for the five reptile species varied considerably due, 

in part, to variation in life history, and we refer the reader to 

individual species accounts for the sources of that variation 

(Appendix B).

Birds, on average, had the largest scores in the phenology 

category. Although only two species were scored as vulnerable to potential changes in temperature and moisture cues 

(elegant trogon and Montezuma quail), all but two species 

(Gould’s wild turkey [Meleagris gallopavo mexicana] and 

American peregrine falcon) were considered to be vulnerable with respect to “event timing” (association between 

fecundity and survival relative to potential changes in the 

timing of environmental factors that influence both). The 

geographic separation of breeding and wintering grounds 

for several of the bird species increased the mean score of 

the birds. Lastly, all species were considered to have a temporally limited breeding period.

Mammals, on average, scored low in the phenology category. Only one species (Towsend’s big-eared bat, 

Corynorhinus townsendii) was scored as vulnerable with respect to temperature and moisture cues. All but three species 

(Coues’ white-tailed deer, desert bighorn sheep, and mesquite mouse) were considered vulnerable to “event timing” 

(Question 2 in Phenology; Appendix B). As with the migratory birds, migratory bats have the potential for mismatched 

phenology in breeding. Only the mesquite mouse and whitebellied long-tailed vole were documented as having multiple 

breeding attempts in a single year. The amphibian and reptile species were considered vulnerable to changes in cues 

used for breeding and event timing, and resilient relative to 

the separation in time and space between cues that initiate 

breeding and resources for breeding. Two of the amphibians 

(Tarahumara frog and Sonoran tiger salamander) and one of 

the reptiles (giant spotted whiptail, Aspidoscelis burti stictogrammus) were scored as vulnerable due to a relatively short 

breeding period.

The preponderance of scores of zero in the biotic interactions category reflects the fact that many species were 

considered neither vulnerable nor resilient (i.e., score of 0) 

for many or all criteria. Most species in this assessment were 

considered to be diet generalists, to be preyed upon by a 

variety of predators, and to have a variety of competitive relationships, all of which led to “neutral” scores. The elegant 

trogon was the only species scored as having a symbiotic 

relationship because it depends on other species to excavate 

nesting cavities in trees. However, it is likely that climate 

change will indeed influence relationships many species 

have with food, interactions with predators and competitors, 

and susceptibility to disease. These relationships are complex due to the number of variables involved and how they 

interact. Predicting what and how changes may occur is difficult. Additional information and more complex analyses 

are needed to identify the specific impacts of climate change 

on species interactions.
24 USDA Forest Service RMRS-GTR-273. 2012.

In considering the results of assessments of potential 

future impacts from climate change, it is important to recognize that uncertainty exists. Predictions for how temperature, 

precipitation, and vegetation may change in the future are 

inherently uncertain. These uncertainties include (but are 

not limited to) “the natural internal variability of the climate 

system, the trajectories of future emissions of greenhouse 

gases and aerosols, and the response of the global climate 

system to any given set of future emissions/concentrations 

(Mearns 2010, adapted from Cox and Stephenson 2007).” 

The method we used to estimate change in plant communities was based upon where suitable climate for vegetation 

communities might exist in the future. However, additional factors are expected to influence shifts in plant species 

distributions, such as carbon dioxide levels, nutrients, soil 

conditions, competitive interactions among species, differential rates of dispersal and survival (McKenney and others 

2007), and the interactions of these variables. Also, it is unclear how climate change may alter the relationship between 

native and invasive species (e.g., buffel grass invasion into 

desert scrub on CNF).

With respect to application of the questionnaire, one biologist assessed all species, which eliminated between-user 

variability in applying information from literature sources 

and subsequently selecting among multiple-choice responses. Having multiple biologists score the same species would 

have been more labor intensive and was beyond the scope 

of our project. However, doing so would have allowed us 

to evaluate whether differential expertise among biologists 

would have resulted in different scores. Lastly, because we 

used a pilot version of SAVS, our scores are not directly 

comparable to SAVS assessments (Bagne and others 2011).

Management Considerations

Identifying Goals for Adaptation Planning

Adaptation planning involves management focused on 

reducing the negative impacts of climate change (Blate and 

others 2009). Climate change creates additional considerations for managers who are already addressing a variety 

of threats such as invasive species, urban and suburban 

encroachment, disease, and the like. A crucial step for managers is to identify goals under climate change in a broad 

sense. For example, some concepts that might be addressed 

are the extent to which management should aim at maintaining threatened and endangered species versus biodiversity 

in general, or whether efforts should be focused on trying 

to resist changes to the distribution and species composition 

of plant communities. Identifying these kinds of goals will 

help to set the context under which subsequent decisions are 

made.

One approach in climate change adaptation planning is 

to consider long-term versus short-term options. Blate and 

others (2009) recommended managing for change as resilience thresholds are crossed in the long term, and building 

resistance and resilience to climate change in the short term 

so that natural resources are better able to withstand change. 

Glick and others (2011) identified the following possible approaches “(1) building resistance to climate-related stressors 

as a way of maintaining high-priority species or systems; (2) 

enhancing resilience in order to provide species and systems 

with a better chance for accommodating and weathering 

changes; and (3) anticipating and facilitating ecological transitions that reflect the changing environmental conditions.”

A variety of planning processes are underway to help 

wildlife managers identify conservation goals and develop 

management strategies. Governmental organizations such 

as the USFS, U.S. Fish and Wildlife Service, and the U.S. 

Geological Survey have assigned staff to climate change 

issues and have offered webinars and workshops. Video 

lectures, case studies of adaptation planning on National 

Forests, and other sources of information such as announcements for workshops can be found on the website of USFS 

Climate Change Resource Center (http://www.fs.fed.us/

ccrc/). The U.S. Department of Interior (DOI) has established Landscape Conservation Cooperatives that consist 

of partnerships between public and private entities to develop large-scale conservation efforts that address a variety 

of impacts, including those of climate change. U.S. DOI is 

also establishing eight regional Climate Science Centers 

to address issues related to climate change. Non-profit organizations such as the Sky Island Alliance (http://www.

skyislandalliance.org/), The Nature Conservancy, and the 

Wildlife Conservation Society have sponsored climate 

change planning workshops for lands in the western and 

southwestern United States. The Nature Conservancy established the Southwest Climate Change Initiative, which 

brought together state, Federal, and non-Governmental 

entities in Colorado, New Mexico, Utah, and Arizona to 

develop strategies to address climate change. Managers can 

seek more information through this wide array of entities for 

more guidance in setting goals for climate change adaptation 

planning.

Using Assessment Results in 

Adaptation Planning

The results of our vulnerability assessment can assist 

wildlife managers in making decisions regarding conservation under climate change. Incorporating the results into 

decision-making by USFS personnel helps to meet the objectives of the USFS Climate Change Performance Scorecard 

(USFS 2011).

In terms of the types of conservation techniques that 

might be considered, Heller and Zevaleta (2009) provided 

an extensive review of strategies identified in the scientific literature for managing for biodiversity under climate 

change. These include (but are not limited to):

(1) increasing connectivity;

(2) integrating climate change planning into planning 

exercises;

(3) mitigating non-climate change threats;

(4) studying responses of species to climate change;

(5) translocating species;
USDA Forest Service RMRS-GTR-273. 2012. 25

(6) increasing the number of reserves;

(7) increasing and maintaining basic monitoring programs.

The range in elevation on the CNF means that some species may be able to move upslope in the face of increasing 

temperatures. Thus, maintaining corridors that allow connectivity across altitude may assist some species on the 

CNF to locate more suitable conditions as the environment 

changes. Reducing non-climate threats might involve reducing bufflegrass invasion, reducing populations of non-native 

amphibians and fish, etc. Examples of various management 

techniques are also outlined in Bagne and others (2011, Table 

5); these examples may help managers to develop appropriate approaches for reducing the vulnerability of species of 

interest. We also encourage managers to consider how ongoing management activities may apply.

Managers can use our assessment in a variety of ways to 

consider management strategies. First, we encourage managers to keep in mind the assumptions and uncertainties 

inherent to assessments during the decision-making process. 

Also, the results should be used in conjunction with additional information on species (e.g., known range size and 

population size).

Managers who want to focus on activities that could 

reduce the vulnerability of many species can examine categorical scores for all taxonomic groups combined and see 

that the majority of species on the CNF showed some vulnerability to criteria that fell within the habitat category. 

However, before actions are undertaken, managers should 

evaluate to what extent activities that are geared toward 

highly vulnerable species might act as additional stressors 

on these species during implementation. For example, forest thinning and prescribed fire to reduce fire risk in areas 

occupied by highly vulnerable species may have immediate 

consequences for survival of those species. One alternative 

might be to thin and prescribe burn in adjacent locations, 

thus avoiding direct negative effects. Ultimately, activities 

that reduce the potential for catastrophic wildfire may help 

to reduce the vulnerability of the species that depend on 

Madrean forest and woodland.

Efforts to maintain and/or increase dispersal into more 

suitable areas as environmental conditions change, or translocation of individuals, might be considered for species that 

were considered vulnerable due to low dispersal. Some management actions can increase resilience for criteria in more 

than one category. For instance, a number of the criteria 

that fall under the physiology category are related to impacts from possible alterations to habitat condition and use 

(e.g., physiological impacts on amphibians from the drying 

of ponds for breeding, or the potential for spring flooding). 

Thus, modifications to habitat conditions might be effective 

management strategies.

Managers may also want to use information on species 

distribution or population size and stability in applying the 

assessment results. For example, the elegant trogon was 

considered vulnerable on more criteria than any of the bird 

species. Within the United States, this species has a very 

small distribution (southern Arizona and New Mexico). 

Depending on other management goals for this species on 

CNF, its limited distribution could be sufficient to prioritize 

its conservation on CNF lands. On the other hand, a highly vulnerable species with a small population size may be 

more difficult or costly to manage under changing conditions than a species that is more abundant and considered 

less vulnerable.

Vulnerability scores can be placed in a geographic context to visualize landscape-scale patterns of vulnerability. 

Davison and others (2012) combined species vulnerability 

scores with models of species’ distributions for 15 species 

on CNF. A “cross-species vulnerability index” was created 

by: (1) summing the vulnerability scores for species with 

potential or known habitat in each 30-m map pixel on the 

CNF, and (2) dividing it by the associated number of species. Cross-species vulnerability was greater in woodlands 

and lower in desert scrub areas.

For examples of how results of other assessments have 

been applied, readers should review the seven case studies 

in Glick and others (2011). For example, the Nevada Natural 

Heritage Program plans to use the results to identify what 

species they will monitor (pp. 85-95). An assessment of vulnerability of Chesapeake Bay to sea-level rise identified the 

need to protect remaining marsh patches (pp. 114-121).

Uncertainty scores for each category, and summed for 

each species, helped to identify general areas where information is lacking. Filling data gaps (e.g., through new research) 

would reduce uncertainty associated with assessing species 

vulnerability and would improve managers’ capacity to predict the outcomes of management activities.

References

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USDA Forest Service RMRS-GTR-273. 2012. 27

Appendix A: Terrestrial Vertebrate Species Assessed
28 USDA Forest Service RMRS-GTR-273. 2012.

Environmental Management Area

Common name

Status1

Peloncillo

Chiricahua

Dragoon

Tumacacori

Santa Rita

Huachuca

Whetstone

Pinaleño

Winchester

Galiuro

Santa Teresa

Santa Catalina

BIRDS

Northern goshawk USFS-2 X X X X X X X X X X X X

Northern gray hawk* USFS Sensitive, 

FSOC X X X X X

American peregrine 

falcon USFS-1 X X X X X X X X X X X X

Gould's wild turkey USFS-2 X X X X X X X X

Montezuma quail USFS-2 X X X X

Western yellow-billed 

cuckoo

USFS-1,

FCL X X

Elegant trogon USFS-2 X X X X X

Northern buff-breasted 

flycatcher

USFS-2,

FUR X X X X X

MAMMALS

Mexican long-tongued 

bat

USFS-2,

FSOC X X X X X X X X

Western yellow bat USFS-2 X X X X X X X X X X X X

Western red bat USFS-2,

FSOC X X X X X X X X X

Allen's lappet-browed 

bat USFS Sensitive X X X

Townsend's big-eared 

bat*

USFS Sensitive, 

FSOC X X X X X X X X X X X X

Abert's squirrel* USFS-2

(non-native) X X

Arizona gray squirrel USFS-2 X X X X

Chiricahua fox squirrel USFS-1 X

Mount Graham red 

squirrel

Federally 

Endangered X

Mesquite mouse*

(aka Merriam's mouse) USFS Sensitive X X X X

White-bellied longtailed vole USFS-1 X

Coues’ white-tailed deer USFS-2 X X X X X X X X X X X X

Desert bighorn sheep USFS-2 X X X

REPTILES

Sonoran desert tortoise USFS-2,

FCL X X X

Species on the Coronado National Forest (CNF) that were assessed for their vulnerability to climate change (n=30). An 

“x” indicates an Environmental Management Area (EMA) with actual or potential habitat according to: (1) the CNF Draft 

Ecological Sustainability Report (USFS 2009), or (2) personal communications. Personal communications indicated with 

an asterisk (see respective species account in Appendix B for citations)
USDA Forest Service RMRS-GTR-273. 2012. 29

Environmental Management Area

Common name

Status1

Peloncillo

Chiricahua

Dragoon

Tumacacori

Santa Rita

Huachuca

Whetstone

Pinaleño

Winchester

Galiuro

Santa Teresa

Santa Catalina

Slevin’s bunchgrass 

lizard USFS-2 X X X X X X

Giant spotted whiptail USFS-2 X X X X X X X X X

Northern Mexican 

gartersnake

USFS-2, 

FCL X X X

Arizona ridge-nosed 

rattlesnake USFS-2 X X X

AMPHIBIANS

Sonoran tiger 

salamander

Federally 

Endangered X

American bullfrog* USFS-2

(non-native) X X X X X X X X X X X X

Chiricahua leopard frog Federally 

Threatened X X X X X X X

Tarahumara frog

USFS-1, 

FSOC X

1

Status designations are as follows: (1) USFS-1 for USFS Species of Concern; (2) USFS-2 for USFS Species of Interest; (3) USFS 

Sensitive = additional species of interest; (4) FSOC= Federal Species of Concern (U.S. Fish and Wildlife Service); (5) FCL = Federal 

Candidate for Listing (USFWS); (6) FUR = Federal “Under Review” (USFWS). Species may have additional designations assigned

by Arizona Game and Fish Department or by other entities. Sources: USFS (2009), USFWS website

(http://www.fws.gov/endangered/species/).
30 USDA Forest Service RMRS-GTR-273. 2012.

Appendix B: Species Vulnerability Assessments

Birds

Northern goshawk ........................................................................................31

Northern gray hawk......................................................................................36

American peregrine falcon...........................................................................42

Gould’s wild turkey......................................................................................47

Montezuma quail..........................................................................................53

Western yellow-billed cuckoo......................................................................58

Elegant trogon ..............................................................................................63

Northern buff-breasted flycatcher ................................................................69

Mammals

Mexican long-tongued bat............................................................................74

Western yellow bat.......................................................................................80

Western red bat.............................................................................................86

Allen’s lappet-browed bat ............................................................................93

Townsend’s big-eared bat.............................................................................99

Abert’s squirrel...........................................................................................106

Arizona gray squirrel..................................................................................112

Chiricahua fox squirrel...............................................................................119

Mount Graham red squirrel........................................................................125

Mesquite mouse .........................................................................................133

White-bellied long-tailed vole....................................................................138

Coues’ white-tailed deer.............................................................................144

Desert bighorn sheep..................................................................................150

Reptiles

Sonoran desert tortoise...............................................................................158

Slevin’s bunchgrass lizard..........................................................................165

Giant spotted whiptail ................................................................................171

Northern Mexican gartersnake...................................................................176

Arizona ridge-nosed rattlesnake.................................................................181

Amphibians

Sonoran tiger salamander...........................................................................186

American bullfrog ......................................................................................193

Chiricahua leopard frog..............................................................................198

Tarahumara frog.........................................................................................203
USDA Forest Service RMRS-GTR-273. 2012. 31

69

Habitat: Northern goshawk (Accipiter gentilis)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected 

to change?

From Squires and Reynolds (1997): In the western hemisphere, this 

species breeds across Canada and much of Alaska, the western half of the 

United States, and portions of western Mexico. Much of its range is yearround, although additional wintering areas are identified in areas outside 

its year-round range. Southeast Arizona is identified as including yearround areas and wintering portions of this species’ range.

Northern goshawks nest in most forest types across their geographic range

from as low as sea level to as high as alpine (Squires and Reynolds 1997). 

On the Kaibab Plateau in northern Arizona, this species nests in 

ponderosa pine forests and in mixed conifer; some nests were found in 

spruce-fir (Reynolds and others 1994). Other goshawk populations in the 

western United States use forests that include Douglas-fir, various pine 

species, and aspen (see references in Squires and Reynolds 1997). The 

Arizona Breeding Bird Atlas (Corman and Wise-Gervais 2005) reports 

that for the state overall, 41% of observations of this species during the 

breeding season were in pure ponderosa pine forest and 26% were in 

mixed conifer (Douglas-fir, white fir, ponderosa pine, and aspen). In the 

mountains of southeastern Arizona, specifically, observers noted this 

species most often in “Madrean pine-oak woodlands dominated by 

Chihuahuan, Apache, and ponderosa pine forests with a scattered 

evergreen oak and juniper understory” and fewer observations in sprucefir or areas dominated by ponderosa or pinyon pine.

Mature to old-growth forests with mostly large trees are typically used for 

nesting (references in Squires and Reynolds 1997). High canopy closure 

(60-90%) is also typical (references in Squires and Reynolds 1997) and 

was observed to be one of the most uniform characteristics of nesting 

areas (Hayward and Escaño 1989 as cited in Squires and Reynolds 1997).

Water, ranging from a pond or small stream to a large river or lake, is 

often present near nests (references in Squires and Reynolds 1997), 

although it is not considered a habitat requirement (references in Squires

and Reynolds 1997).

Across its range, this species hunts in diverse habitats (open-sage steppes 

and dense forests, including riparian areas). In northern Arizona, this 

species has been observed to forage in forests with greater canopy closure 

and greater density of trees relative to contrast plots (Beier and Drennan

1997 as cited in Squires and Reynolds 1997).

This species, or its potential habitat, occurs on all 12 of the EMAs on 

CNF (USFS 2009). Projections of suitable climate for vegetation 

communities forest-wide (Chapter 1) predicted declines in suitable 

climate for all plant community types, with the exception of increased 

suitable climate for semi-desert grassland and small increases in Sonoran 

desert scrub (present in small amounts on the CNF).

Projected reductions in forested habitats will reduce breeding habitat for 

this species.

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to 

change?

Use of areas in winter is not well understood, and most data are from 

Europe (Squires and Reynolds 1997). Wintering goshawks in the Rocky 

Mountains were observed using cottonwood riparian areas (Squires and

Ruggiero 1995 as cited in Squires and Reynolds 1997), aspen, spruce/fir, 

lodgepole pine, ponderosa pine, and open habitats (Squires and Reynolds 

1997).

The northern goshawks that breed in Arizona are considered year-round 

residents (see Habitat, Question 8), so we assumed that in Arizona nonbreeding habitat is similar, or the same as, breeding habitat.

2

3. Habitat 

components: 

Are specific 

habitat 

components 

Populations in the western United States typically nest in conifers 

(references in Squires and Reynolds 1997). This includes ponderosa pine, 

Douglas-fir, white fir, California red fir, western larch, western hemlock, 

1
32 USDA Forest Service RMRS-GTR-273. 2012.

70

Habitat: Northern goshawk (Accipiter gentilis)

Trait/Quality Question Background info. & explanation of score Points

breeding required for 

breeding expected 

to change?

and lodgepole pine. In the Southwest, ponderosa pine is used frequently 

(references in Squires and Reynolds 1997), and nests are usually in the 

largest trees of the stand (references in Squires and Reynolds 1997).

Increased tree mortality from reduced annual precipitation, increased 

fires, and increased insect infestations is expected to reduce the 

abundance of large trees capable of supporting raptor nests and perches.

4. Habitat 

components: 

non-breeding

Are specific 

habitat 

components 

required for 

survival during 

non-breeding 

periods expected 

to change?

Winter habitat use is poorly understood and roosting habitat is not 

described (Squires and Reynolds 1997). However, this species is 

presumed to use trees for roosting and perching.

1

5. Habitat 

quality and 

reproduction

Are features of 

the habitat 

associated with 

better 

reproductive 

success expected 

to change? 

Found no information in Squires and Reynolds (1997) on whether there 

are known habitat features associated with variation in reproductive 

success. Variation among sites has been observed; in a 2-year study on 3 

National Forests in eastern Oregon, productivity varied between years and 

among landscapes on the same study areas (DeStefano and others 1994). 

Although not pertaining to reproductive success, Squires and Reynolds 

(1997) indicated that the relationship between environmental conditions 

such as vegetative type and landscape characteristics and how they affect 

breeding densities is not well understood; the authors also indicated that 

yearly occupancy rates are highly variable and may be related fluctuations 

in prey densities and severe (cold) weather conditions.

0

6. Habitat 

quality and 

survival

Are features of 

the habitat 

associated with 

better survival 

expected to 

change? 

Winter habitat use is poorly understood (Squires and Reynolds 1997). 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

We considered birds to be very mobile due to their capacity for flight and, 

thus, overall able to colonize new areas.

-1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

This species is considered primarily a year-round resident in Arizona 

(Corman and Wise-Gervais 2005). Individuals nesting at high elevations 

have been observed moving to lower elevations in winter (Millsap 1981 

as cited in Corman and Wise-Gervais 2005). However, such movements 

not considered to require significantly different types of habitat.

0

Physiology: Northern goshawk (Accipiter gentilis)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are physiological 

thresholds related 

to temperature or 

moisture expected 

to change?

In the western hemisphere, the range of northern goshawk is the United 

States, Canada and portions of western Mexico. The CNF is in the 

southern portion of the species’ latitudinal range.

Use of water for drinking is unknown (Squires and Reynolds 1997). We 

found no information on tolerance of extreme heat in Web of Science 

database search on species and “tolerance.” With the exception of cases of 

extreme heat rises, presumably could tolerate increases of several degrees 

C. Shaded habitat might reduce effects of solar radiation on rise in body 

temperature, although shade from trees expected to decline with time.

0
USDA Forest Service RMRS-GTR-273. 2012. 33

71

Physiology: Northern goshawk (Accipiter gentilis)

Trait/Quality Question Background info. & explanation of score Points

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to 

change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality for this 

species. Individuals that breed in CNF are believed to winter there as 

well, so they would not be exposed to potential changes in storms along 

a migratory route.

Exposure to cold and rain has been attributed to egg and chick mortality 

(see references in Squires and Reynolds 1997). Not expected that cold 

or rain will increase during breeding season under climate change.

See also Physiology, Question 1.

0

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to 

change?

This species is a diurnal forager but does not show diurnal rhythms of 

foraging activity; timing of hunting depends on activity patterns of the 

prey (Squires and Reynolds 1997). No information found in Squires and 

Reynolds (1997) indicating limits on activity period relative to high 

temperatures.

With the exception of cases of extreme heat rises, seems unlikely for 

seasonal or daily active periods to be directly restricted to the point of 

significantly reducing survival. Unclear to what extent prey activity 

might be reduced due to temperature increases and how that might 

indirectly affect this species.

See also Physiology, Question 1.

0

5. Metabolic 

inhibition

Does this species 

possess an ability 

to reduce metabolic 

energy or water 

requirements?

No reports of torpor in Squires and Reynolds (1997). No citations of 

torpor found in Web of Science database. Based on this information, we 

assumed that the species does not use torpor.

1

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the 

capacity to store 

energy or water in 

the long term?

This species caches prey, primarily when nestlings are small; most 

cached items are retrieved the same day (Schnell 1958 as cited in 

Squires and Reynolds 1997), so not considered a long-term food storage 

behavior.

1

7. Variable life 

history

Does this species 

have alternative 

life history 

strategies to cope 

with variable 

resources or 

climate conditions?

No variable life history strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Longevity record (i.e., longest-lived individual recorded) of a wild bird 

is at least 11 years (Fowler 1985 as cited in Squires and Reynolds 

1997). A 6-year mark-recapture study in northern Arizona estimated 

annual survival of birds greater than 1 year old to be 69% for males and 

87% for females (unpublished data cited in Squires and Reynolds 1997).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that birds have insufficient 

food for breeding, most of the population would not survive longer than 

the periods of limited reproduction. 

1
34 72 USDA Forest Service RMRS-GTR-273. 2012.

Phenology: Northern goshawk (Accipiter gentilis)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival?

This species is a “predictable breeder,” meaning its breeding season 

occurs at the same time each year (i.e., spring). In predictable breeders, 

photoperiod is the predominant proximate factor leading to gonadal 

changes required for reproduction (Dawson and others 2001). It should 

be noted that, in general, birds also use local predictive information, 

including temperature, availability of food, and rainfall, to make shortterm adjustments to reproductive timing, (Wingfield 2008), although 

this short-term adjustment is not addressed by this question (see Bagne 

and others 2011).

0

2. Event 

timing

Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

Food availability is believed to strongly affect population dynamics in 

the northern goshawk (Squires and Reynolds 1997). Many raptor 

species that consume rodents show large variation in annual production 

of young in relation to fluctuations in levels of their prey (see references 

in Durant and others 2000; Newton 1998; and Steenhof and others 

1997).

A food supplementation study in New Mexico showed that in one year 

(but not another), supplemented nests had a substantially higher nestling 

survival rate relative to control nests; however, the authors indicated 

that the mechanism was lower predation of treatment birds, probably 

due to increased time spent guarding nests by the female (Ward and 

Kennedy 1996).

Changes in the timing of precipitation and increases in temperature have 

the potential to alter the timing of prey availability and abundance and, 

hence, fecundity.

1

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

This species is a year-round resident in Arizona. Typically, increases in 

prey abundance (a critical resource) occur in spring, so there is little 

temporal separation. There is no spatial separation since the species is a 

year-round resident.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

This species has only one brood per year; laying replacement clutches 

has been observed but is considered rare (Squires and Reynolds 1997).

1

Biotic interactions: Northern goshawk (Accipiter gentilis)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

This species consumes a variety of relatively large-bodied birds and 

mammals, with main foods consisting of ground and tree squirrels, 

rabbits and hares, large passerines, woodpeckers, game birds, and 

corvids (Squires and Reynolds 1997). In Arizona, this species was 

observed preying on Abert’s squirrels (Westcott 1964 as cited in 

Squires and Reynolds 1997). Therefore, it has generalist prey habits.

0

2. Predators Are important 

predator 

Northern goshawks have relatively few natural predators (Squires and 

Reynolds 1997). Documented nestling predators include mammals and 

0
USDA Forest Service RMRS-GTR-273. 2012. 35

73

Biotic interactions: Northern goshawk (Accipiter gentilis)

Trait/Quality Question Background info. & explanation of score Points

populations 

expected to 

change?

great horned owls; adult predators include eagles, marten, and great 

horned owls. Limited information on how predation affects goshawk 

populations (Squires and Reynolds 1997).

3. Symbionts Are populations of 

symbiotic species 

expected to 

change?

None known. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to 

change?

A variety of diseases and parasites (both ecto- and internal) are reported 

for the northern goshawk (Squires and Reynolds 1997). Trichomoniasis, a 

disease caused by the protozoan parasite Trichomonas gallinae, can be 

acquired by goshawks and other raptors by consuming infected 

columbids (doves and pigeons). The parasite causes significant mortality 

in nestlings and fledglings in urban-nesting Cooper’s hawks in Arizona 

(Boal and others 1998 as cited in Rosenfield and others 2002). However, 

in 48 nests in non-urban areas of Wisconsin, North Dakota, and British 

Columbia, the parasite prevalence was very low with no attributable 

nestling mortality. It appears that the disease may be more of a concern to 

urban populations of raptors where columbids are more abundant. For 

example, Krone and others (2005) investigated the prevalence of the 

parasite in northern goshawks that had colonized urban and suburban 

areas of Berlin, Germany.

0

5. Competitors Are populations of 

important 

competing species 

expected to 

change?

No information was found in Squires and Reynolds (1997) 

documenting inter-specific competitive interactions.

0

Literature Cited

Bagne, K.E., M.M. Friggens, and D.M. Finch. 2011. A system for assessing vulnerability of species 

(SAVS) to climate change. Gen. Tech. Rep. RMRS-GTR-257. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station. 28 p.

Corman, T.E., and C. Wise-Gervais, eds. 2005. Arizona breeding bird atlas. Albuquerque, NM: 

University of New Mexico Press.

Dawson, A., V.M. King, G.E. Bentley, and G.F. Ball. 2001. Photoperiodic control of seasonality in birds. 

Journal of Biological Rhythms 16:365-380.

DeStefano, S., S.K. Daw, S.M. Desimone, and E.C. Meslow. 1994. Density and productivity of northern

goshawks: implications for monitoring and management. Studies in Avian Biology 16:88-91.

Durant, J.M., S. Massemin, C. Thouzeau, and Y. Handrich. 2000. Body reserves and nutritional needs 

during laying preparation in barn owls. Journal of Comparative Physiology B 170:253-260.

Krone, O., R. Altenkamp, and N. Kenntner. 2005. Prevalence of Trichomonas gallinae in northern 

goshawks from the Berlin area of northeastern Germany. Journal of Wildlife Diseases 41:304-309.

Newton, I. 1998. Population limitation in birds. New York: Academic Press. 597 p.

Reynolds, R.T., S.M. Joy, and D.G. Leslie. 1994. Nest productivity, fidelity, and spacing of northern

goshawks in northern Arizona. Studies in Avian Biology 16:106-113.

Rosenfield, R.N., J. Bielefeldt, L.J. Rosenfield, S.J. Taft, R.K. Murphy, and A.C. Stewart. 2002. 

Prevalence of Trichomonas gallinae in nestling Cooper’s hawks among three North American 

populations. Wilson Bulletin 114:145-147.

Squires, J.R. and R.T. Reynolds. 1997. Northern Goshawk (Accipiter gentilis) In: Poole, A., ed. The birds 

of North America online. Ithaca, NY: Cornell Lab of Ornithology. Available: 

http://bna.birds.cornell.edu/bna/species/298doi:10.2173/bna.298.
36 USDA Forest Service RMRS-GTR-273. 2012.

74

Steenhof, K., M.N. Kochert, and T.L. McDonald. 1997. Interactive effects of prey and weather on golden 

eagle reproduction. Journal of Animal Ecology 66:350-362.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Ward, J.M., and P.L. Kennedy. 1996. Effects of supplemental food on size and survival of juvenile

northern goshawks. Auk 113:200-208.

Wingfield, J.C. 2008. Comparative endocrinology, environment, and global change. General and 

Comparative Endocrinology 157:207-216.

Habitat: Northern gray hawk (Buteo nitidus plagiata)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or location 

of the associated 

vegetation type used 

for breeding activities 

by this species 

expected to change?

Taxonomic note: The 47th Supplement to the American 

Ornithologists’ Union Checklist of North American Birds 

recognizes Asturina nitida as Buteo nitida (Bibles and others 

2002). Also, Bibles and others (2002) indicated that the subspecies plagiata occurs in Arizona (now, Buteo nitidus plagiata; 

some authors use maxima).

In the United States northern gray hawks breed in a very limited 

range (Arizona and Texas, sporadically in New Mexico) and is 

considered uncommon in the United States, with likely fewer than 

100 nesting pairs (Bibles and others 2002). Most nesting records 

in Arizona are in the south-central part of the state (in the counties 

of Cochise, Pima, Pinal, and Santa Cruz), particularly along San 

Pedro River and its tributaries, Sonoita and Arivaca Creeks, and 

the southernmost reaches of the Santa Cruz River and its 

tributaries. Based on observations by Arizona Breeding Bird Atlas 

(ABBA) observers (Corman 2005), this raptor was considered to 

be locally common on portions of the San Pedro River with 

perennial flow and on parts of the Cienega Creek and Sonoita 

Creek; observations also documented on the Santa Cruz River.

In the United States and northern Mexico, gray hawks forage 

mostly in mesquite woodlands and nests in adjacent forests of 

cottonwood and willow that occur along streams and rivers 

(Bibles and others 2002). Approximately 73% of the observations 

during the ABBA surveys (n=55) were reported from areas with 

perennial or intermittent streams dominated by tall Fremont 

cottonwood and Goodding willow, typically with stands of velvet 

mesquite (Corman 2005). Most of the remaining observations 

were made in riparian woodlands containing Arizona sycamore, 

often with cottonwoods and willows; and in some cases,

individuals were observed nesting in drier drainages containing 

Madrean evergreen oaks, Arizona walnut, velvet ash, and netleaf 

hackberry. Observations of nesting birds by ABBA recorders 

were at elevations ranging 594-1524 m. (1950-5000 ft).

Mesquite is considered important for breeding; nesting is often in 

lone cottonwood trees surrounded by mesquite woodland (Glinski

1988; Bibles 1999). Historically, gray hawks used mesquite 12-15 

m tall, but mesquite this tall has become rare in Arizona. Corman 

(2005) indicated that some nesting territories had been lost due to 

wildfires and depletion of groundwater from drought and 

pumping.

2
USDA Forest Service RMRS-GTR-273. 2012. 37

75

Habitat: Northern gray hawk (Buteo nitidus plagiata)

Trait/Quality Question Background info. & explanation of score Points

Northern gray hawks are known, or have the potential, to occur on 

the following EMAs: Peloncillo, Tumacacori, Santa Rita, 

Huachuca, and Galiuro (Jones, personal communication). 

Projections of suitable climate for vegetation communities on 

these five EMAs (Chapter 1) predicted a decline in the total areas 

that would have suitable climate for Madrean forest and woodland 

and Madrean conifer forest and an increase in areas that would 

have suitable climate for semi-desert grassland.

Riparian habitats are predicted to decline due to decreased stream 

flows (on average), increased aridity, and an increased risk of 

fires.

2. Area and 

distribution: nonbreeding

Is the area or location 

of the associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Bibles and others (2002) indicated that the plagiata subspecies

occurs in Arizona, New Mexico, Texas, and south to northwest 

Costa Rica, so we assumed that breeders in the United States are 

not likely to migrate farther south than Costa Rica, where other 

sub-species occur. According to Bibles and others (2002), little 

information exists on winter habitat. In Sonora, Mexico, gray 

hawks occupy Sinaloan deciduous forest and Sinaloan thorn scrub 

(Monson 1986 as cited in Bibles and others 2002), the latter being 

similar to mesquite forests used for foraging in Arizona. Glinski 

(1998) indicated that gray hawks in the tropics prefer xeric 

second-growth and thorn forests.

Overall, expected that drier conditions will occur in wintering 

range for this species, leading to reduction in trees.

2

3. Habitat 

components: 

breeding

Are specific habitat 

components required 

for breeding expected 

to change?

No information found in Bibles and others (2002) to indicate 

presence of habitat components for breeding. Bibles and others 

(2002) indicated no information on drinking behavior, and we 

found no other indication that gray hawks require standing water. 

Glinski (1988) indicated that they tend not to occupy forests 

without tropical-subtropical thorn scrub and woodland elements, 

so this was considered under Habitat, Question 1.

0

4. Habitat 

components: 

non-breeding

Are specific habitat 

components required 

for survival during 

non-breeding periods 

expected to change?

No information found in Bibles and others (2002) to indicate 

presence of habitat components for survival on non-breeding 

periods.

0

5. Habitat quality 

and reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

In Arizona, habitat quality determined by the amount of mesquite 

within the home range (Bibles 1999). We considered mesquite 

likely to decline under climate change.

1

6. Habitat quality 

and survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information was found in Bibles and others (2002); given the 

gaps in knowledge on gray hawks, it is likely that if there are any 

such features, they have not been quantified.

0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and tendency 

to disperse?

We considered birds to be very mobile due to their capacity for 

flight and, thus, overall able to colonize new areas.

-1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonBibles and others (2002) indicated that populations in the United 

States and northern Mexico are migratory. In Arizona, individuals 

have been observed in December (Glinski 1988), and there are 

unverified reports throughout winter months. Most individuals 

depart from Arizona by late September or early October (Corman 

2005). However, Bibles and others (2002) indicated that it is 

1
38 USDA Forest Service RMRS-GTR-273. 2012.

76

Habitat: Northern gray hawk (Buteo nitidus plagiata)

Trait/Quality Question Background info. & explanation of score Points

breeding habitats? unknown whether individuals observed in areas of year-round 

residency are migrants or are remaining in the breeding area yearround.

Overall, while some may over-winter in Arizona, the majority of 

those that breed in Arizona are expected to migrate south of the 

United States for winter. 

Physiology: Northern gray hawk (Buteo nitidus plagiata)

Trait/Quality Question Background info. & explanation of score Points

1. Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Bibles and others (2002) indicated no information on drinking 

behavior or temperature regulation for this species. Redshouldered hawk (Buteo lineatus) is likely the most closely related 

North American species based on morphology and ecology, but 

there is no information on temperature regulation in the Birds of 

North America species account for that species. We assumed that 

the northern gray hawk is capable of behavioral thermoregulation.

With the exception of rare cases of extreme heat rises, presumably 

could tolerate increases of several degrees C.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed 

in reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme weather 

conditions

Are extreme weather 

or disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for the 

southwestern United States. Overall, not clear to what extent 

timing and intensity of heat waves will affect survival and 

reproduction. We considered it unlikely that heat waves would 

cause widespread mortality.

Not clear where Arizona breeders over-winter or whether they 

would be exposed to hurricanes. Hurricane intensity is expected to 

increase under global climate change, but frequency predictions

are inconsistent (Emanuel 2005); frequency increase likely more 

detrimental overall to migrating populations than intensity since 

hurricane-level winds already detrimental to migrants.

0

4. Limitations to 

active period

Are projected 

temperature or 

precipitation regimes 

that influence 

activity period of 

species expected to 

change?

Gray hawks forage diurnally. In Arizona, foraging activity peaks 

during mid-morning and early evening, with the least amount of 

foraging at mid-day, presumably related to activity patterns of 

prey species (Bibles and others 2002). No information was found 

in Bibles and others (2002) that indicated limits on activity period 

relative to high temperatures.

With the exception of cases of extreme heat rises, we considered it 

unlikely that seasonal or daily active periods would be directly 

restricted to the point of significantly reducing survival. 

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

No information on energetics and metabolism was reported in 

Bibles and others (2002), but we assumed that gray hawks do not 

undergo torpor based on the lack of documentation of torpor in 

numerous other raptor species.

1

6. Survival 

during resource 

Does this species 

have lower energy 

Gray hawks have been observed to cache prey (e.g., gartersnakes, 

partly eaten birds, and cottontail rabbits) on large horizontal limbs 

1
USDA Forest Service RMRS-GTR-273. 2012. 39

77

Physiology: Northern gray hawk (Buteo nitidus plagiata)

Trait/Quality Question Background info. & explanation of score Points

limitation requirements or 

possess the capacity 

to store energy or 

water in the long

term?

(Bibles and others 2002). Cached food is available for a few days 

at most, so we did not consider this long-term food storage.

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No variable life history strategies. 0

8. Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

First breeding typically in at least the third calendar year, but 

occasionally in the second calendar year (Bibles and others 2002). 

There is no information on lifespan (Bibles and others 2002). In 

the red-shouldered hawk, a similar species, mean survival in one 

study was ~2 years; another study found 95% mortality of 

nestlings within 5.2 years (references in Dykstra and others 2008).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that birds have 

insufficient food for breeding, we considered it possible that much 

of the population would not survive longer than periods of limited 

reproduction.

1

Phenology: Northern gray hawk (Buteo nitidus plagiata)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Individuals arrive in Arizona generally in mid-March, and egg laying 

typically occurs in early May (Glinski 1998). Nest building or nest 

repairing has been observed in April and early May by ABBA 

recorders (Corman 2005).

Northern gray hawks are a predictable breeder, meaning the breeding 

season occurs at the same time each year (i.e., spring). In predictable 

breeders, photoperiod is the predominant proximate factor leading to 

gonadal changes required for reproduction (Dawson and others 

2001). It should be noted that, in general, birds also use local 

predictive information such as temperature, food availability, and 

rainfall to make short-term adjustments to reproductive timing 

(Wingfield 2008), although this short-term adjustment is not 

addressed by this question (see Bagne and others 2011).

0

2. Event timing Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Changes in the timing of precipitation and increases in temperature 

have the potential to alter the timing of prey (reptiles, particularly 

lizards) availability and abundance, which, in turn, could influence 

fecundity of gray hawks.

1

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

Given that northern gray hawks are migratory, critical resources for 

breeding (such as food) occur far from where individuals overwinter; thus, individuals have no direct information about resource 

abundance on the breeding grounds in a given year when they 

initiate migration from their wintering grounds. 

1
40 USDA Forest Service RMRS-GTR-273. 2012.

78

Phenology: Northern gray hawk (Buteo nitidus plagiata)

Trait/Quality Question Background info. & explanation of score Points

4. Resilience to 

timing 

mismatches 

during breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Considered to rear only one brood per season, although individuals 

may re-nest if original clutch fails prior to hatching (Bibles and 

others 2002).

1

Biotic interactions: Northern gray hawk (Buteo nitidus plagiata)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Gray hawks appear to eat mostly reptiles throughout its range, 

although studies of diet mostly have been on individuals in northern 

part of the species’ range (Bibles and others 2002). Glinski (1988) 

observed that 74% of prey that were delivered to nestlings were 

lizards, 5% were gartersnakes, 11% were nestling and adult birds, 

and 10% were mammals. Gray hawks are able to hunt terrestrial and 

arboreal lizards due to their ability to maneuver well in flight 

(Glinski 1998).

Bibles and others (2002) indicated that the gray hawk diet (ostensibly 

in United States) is dominated by whiptail lizards (Cnemidophorus

spp.) and spiny lizards (Sceloporus spp.). Amadon and Phillips

(1939) considered it possible that the distribution of the gray hawk 

might be determined by the occurrence of a few reptile species.

Overall, it appears that gray hawks may depend mostly on just a few 

species of lizards which will probably be negatively impacted by 

climate change (particularly in the habitat shared by the gray hawk).

1

2. Predators Are important 

predator 

populations 

expected to 

change?

Bibles and others (2002) indicated that there is little information on 

predation in gray hawks. The great horned owl is a documented 

nestling predator and the red-tailed hawk is a potential predator; the 

amount of nest predation by mammals is not known. Bibles and 

others (2002) considered that owl predation may be a significant 

source of mortality for both gray hawk adults and nestlings. We 

considered it likely that there is a suite of predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to 

change?

No indication of symbiotic relationships in Bibles and others (2002). 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to 

change? 

Bibles and others (2002) indicated that there is little information on 

diseases and body parasites. Nestling mortality has been attributed to 

trichomoniasis (caused by Trichomonas gallinae; Stensrude 1965 as 

cited in Bibles and others 2002).

0

5. Competitors Are populations of 

important 

competing species 

expected to 

change?

Bibles and others (2002) indicated a lack of information on 

competition. Glinski (1998) listed eight species of raptors found 

nesting within ~1 km of nesting gray hawks. Successful nesting 

documented within 50 m of nests of Cooper’s hawk, red-tailed hawk, 

and zone-tailed hawks (Glinski and Millsap 1987 as cited in Bibles 

and others 2002).

0
USDA Forest Service RMRS-GTR-273. 2012. 41

79

Literature Cited

Amadon, D., and A.R. Phillips. 1939. Notes on the Mexican goshawk. Auk 56:183-184.

Bagne, K.E., M.M. Friggens, and D.M. Finch. 2011. A system for assessing vulnerability of species 

(SAVS) to climate change. Gen. Tech. Rep. RMRS-GTR-257. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station. 28 p.

Bibles, B.D., R.L. Glinski, and R.R. Johnson. 2002. Gray Hawk (Asturina nitida). In: Poole, A., ed. The 

birds of North America online. Ithaca, NY: Cornell Lab of Ornithology. Available: 

http://bna.birds.cornell.edu/bna/species/652; doi:10.2173/bna.652.

Bibles, B.D. 1999. The relationship between productivity and habitat quality in gray hawks. Dissertation. 

University of Arizona, Tucson.

Corman, T.E. 2005. Gray Hawk. In: Corman, T.E., and C. Wise-Gervais, eds. The Arizona Breeding Bird 

Atlas. Albuquerque, NM: University of New Mexico Press: 136-137.

Dawson, A., V.M. King, G.E. Bentley, and G.F. Ball. 2001. Photoperiodic control of seasonality in birds. 

Journal of Biological Rhythms 16:365-380.

Dykstra, C.R., J.L. Hays, and S.T. Crocoll. 2008. Red-shouldered Hawk (Buteo lineatus). In: Poole, A., 

ed. The birds of North America online. Ithaca, NY: Cornell Lab of Ornithology. Available: 

http://bna.birds.cornell.edu/bna/species/107; doi:10.2173/bna.107.

Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 

436:686-688.

Glinski, R.L. 1988. Gray Hawk. In: Glinski R.L., and others, eds. Proceedings of the Southwest Raptor 

Management Symposium and Workshop. Washington, DC: National Wildlife Federation: 83-86.

Glinski, R.L. 1998. Gray Hawk (Buteo nitidus). In: The Raptors of Arizona. Tucson: University of 

Arizona Press, and Phoenix: Arizona Game and Fish Department: 82-85.

Jones, Larry. 2010. [Personal communication]. February 17, 2010. Tucson, AZ: U.S. Department of 

Agriculture, Forest Service, Coronado National Forest, Assistant Program Manager for Wildlife, Fish, 

and Rare Plants.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: a comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Wingfield, J.C. 2008. Comparative endocrinology, environment, and global change. General and 

Comparative Endocrinology 157:207-216.
42 USDA Forest Service RMRS-GTR-273. 2012.

80

Habitat: American peregrine falcon (Falco peregrinus anatum)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change?

Taxonomic note: This is one of three sub-species that occur in the 

United States (White and others 2002), and it occurs in North 

America, from south of the tundra in Canada to northern Mexico, 

except for the Pacific Northwest.

Peregrine falcons occupy numerous terrestrial biomes in North 

America with no clear preference for one type, although there may be 

higher densities in tundra and on the coasts. Burger (2005) indicated 

that topographic relief and prey base is more important than 

vegetation in terms of where this species occurs. ABBA observers 

recorded peregrine falcons in 22 habitat types, ranging from forest to 

desert to wetland. Almost 48% of observations were in forested areas 

(pinyon pine-juniper, evergreen oaks, ponderosa pine, and mixed 

conifer), and 33% were in desert scrub containing sagebrush and 

other shrubs, and Sonoran desert scrub near water. Hunts in the open 

sky above treetops and rarely nests in desert mountain ranges in areas 

that are not near large bodies of water (Burger 2005). In New Mexico 

in the breeding season, most likely to be seen in areas with cliffs and 

canyons with open areas for pursuing prey (Stahlecker 2010). Glinski 

(1998) estimated that more than 200 pairs nest in Arizona.

American peregrine falcons occur, or potential habitat exists, on all 12 

of the EMAs on CNF (USFS 2009). Projections of suitable climate 

for vegetation communities forest-wide (Chapter 1) predicted declines 

in suitable climate for all plant community types with the exception of 

increases of suitable climate for semi-desert grassland and small 

increases in Sonoran desert scrub (present in small amounts on the 

CNF).

Overall, we assumed that loss of forest and woodlands will not 

significantly reduce breeding habitat on CNF.

0

2. Area and 

distribution: nonbreeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to 

change?

Peregrine falcons occupy a wide range of habitats as a result of their

large geographical range (White and others 2002). In New Mexico in 

the non-breeding season, they are most likely to be seen along bodies 

of water or other areas where there are large concentrations of prey 

(Stahlecker 2010).

See also Habitat, Question 8.

Overall, because peregrine falcons occupy a variety of habitats we

considered it likely that individuals would be able to respond to 

changes reductions in forests and woodlands.

0

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change?

Cliffs and other structures for nesting are important for this species. 

Most commonly occupied habitats contain cliffs, and eggs are laid in 

a scrape (White and others 2002). Nesting in human-based structures 

(buildings and bridges) is often aided by an artificial nestbox. Reports 

of using abandoned osprey or raven nests on towers and eagle nests in 

trees in Alaska (references in White and others 2002). In Arizona, all 

peregrine falcon eyries have been on cliff faces, canyon walls, spires, 

and, in some cases, on rocky ridges and outcrops (Burger 2005). Most 

commonly individuals search for prey from a perched position, but 

also while flying (White and others 2002). Often perches on cliffs, 

especially in breeding season.

No change expected in the number of suitable cliff sites under 

projected climate change.

0

4. Habitat 

components: 

Are specific habitat 

components 

required for 

In fall and winter, peregrine falcons often hunt from lower perches 

than in the breeding season (including trees, utility poles, fence posts, 

banks, mounds, driftwood (Dekker 1980, 1999 as cited in White and 

0
USDA Forest Service RMRS-GTR-273. 2012. 43

81

Habitat: American peregrine falcon (Falco peregrinus anatum)

Trait/Quality Question Background info. & explanation of score Points

non-breeding survival during 

non-breeding 

periods expected to 

change?

others 2002). Unclear whether reduction in number of trees, if used in 

wintering areas, could reduce number of non-cliff perches.

5. Habitat quality 

and reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change?

No information found in White and others (2002) tying specific 

habitat features to greater reproductive success. Kauffman and others 

(2003) found that American peregrine falcons in urban areas in 

California had higher fecundity rates than those in rural habitats. 

Differential productivity among years and among regions in the 

United States is documented and thought to be related to differences 

in prey availability (see White and others 2003), but no clear ties to 

specific habitat features have been identified, particularly to features 

that are likely to be altered under climate change.

0

6. Habitat quality 

and survival

Are features of the 

habitat associated 

with better survival 

expected to 

change? 

No information found (see Habitat, Question 5). 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

We considered birds to be very mobile due to their capacity for flight 

and, thus, overall able to colonize new areas. Some peregrine falcons 

migrate very long distances.

-1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Populations across this species’ breeding range in the United States 

vary in whether they over-winter or migrate long distances to 

wintering grounds; birds breeding in northernmost areas of the 

continent in tundra typically migrate the farthest south (central 

Argentina and Chile), and those that breed farther south travel shorter 

distances (White and others 2002). Burger (2005) indicated that some 

individuals in Arizona remain near nesting areas year-round, whereas 

others move to lowlands or migrate south. Stahlecker (2010) indicated 

that it is likely that most individuals breeding in Arizona over-winter 

south of New Mexico, although there are consistent winter 

observations of the species in southern New Mexico. Overall, some 

individuals appear to leave Arizona in winter.

1

Physiology: American peregrine falcon (Falco peregrinus anatum)

Trait/Quality Question Background info. & explanation of score Points

1. Physiological 

thresholds

Are limiting 

physiological 

conditions 

expected to 

change?

Most peregrine falcons can maintain a relatively constant cloacal 

temperature over a span of air temperature ranging 20-50 °C (White 

and others 2002). They thermoregulate primarily through behavioral 

adjustments (such as seeking favorable microclimates, drooping legs 

or wings, orienting body differently relative to sun, panting, erecting 

feathers), evaporative cooling, and adjusting body insulation to 

decrease the amount of heat lost (White and others 2002).

Reported to drink frequently but it is not clear whether water is 

required. Adults and juveniles also bathe.

Female peregrine falcons nesting on south slopes and where there is 

little vegetation screening (e.g., in the Arctic) often shade eggs/small 

young from heat and sun rather than incubating, and heat stress of 

both adults and young can occur (White and others 2002).

With the exception of rare cases of extreme heat rises, presumably 

could tolerate increases of several degrees C. 

0
44 USDA Forest Service RMRS-GTR-273. 2012.

82

Physiology: American peregrine falcon (Falco peregrinus anatum)

Trait/Quality Question Background info. & explanation of score Points

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme weather 

conditions

Are extreme

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to 

change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, it is not clear to what extent timing and 

intensity of heat waves will have on survival and reproduction. We 

considered it unlikely that heat waves would cause widespread 

mortality for this species. See also Physiology, Question 1.

Not clear where individuals who breed in Arizona over-winter or 

whether they would be exposed to hurricanes. Hurricane intensity is 

expected to increase under global climate change, but frequency

predictions are inconsistent (Emanuel 2005); frequency increase would 

likely be more detrimental overall to migrating populations than 

intensity since hurricane-level winds already detrimental to migrants.

0

4. Limitations to 

active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to 

change?

Peregrine falcons are diurnal foragers. No information found in White 

and others (2002) indicating limits on activity period relative to high 

temperatures. See also Physiology, Question 1.

With the exception of cases of extreme heat rises, it seems unlikely 

that seasonal or daily active periods would be directly restricted to the 

point of significantly reduced survival.

0

5. Metabolic 

inhibition

Does this species 

possess an ability 

to reduce metabolic 

energy or water 

requirements?

No reports of torpor in White and others (2002). 1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the 

capacity to store 

energy or water in 

the long term?

Peregrine falcons cache surplus prey, particularly during the breeding 

season, in apparent response to short periods when prey is unavailable 

(e.g., daily or multiple-day periods, including during stormy 

conditions) (White and others 2002). Cached food would be available 

for a few days at most, so we did not consider this long-term food 

storage.

1

7. Variable life 

history

Does this species 

have alternative 

life history 

strategies to cope 

with variable 

resources or 

climate conditions?

No variable life history strategies. 0

8. Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Longevity records for banded birds (i.e., longest-lived birds recorded) 

range 16-20 years (White and others 2002). White and others (1992) 

cited studies with values of adult survival rates of ranging from 63-

100%. White and others (2002) estimated that for a population where 

adult survival rate is 70% per year, the median adult life (after second 

year) is about 2 years (mean 2.8 years), assuming that rate does not 

change with age. This translates into at 10 years, 3% of cohort would 

still be alive.

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that birds have 

insufficient food for breeding, it is possible that much of the 

population would not survive longer than the period of limited 

reproduction, particularly if drought conditions reduced annual 

survival rates below 70%.

1
USDA Forest Service RMRS-GTR-273. 2012. 45

83

Phenology: American peregrine falcon (Falco peregrinus anatum)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Burger (2005) indicated that ABBA observers documented courtship 

displays and pair formation beginning in March. In Arizona, eggs are 

typically laid between mid-March and mid-May (Glinski 1998).

This species is a predictable breeder, meaning its breeding season 

occurs at the same time each year (i.e., spring). In predictable 

breeders, photoperiod is the predominant proximate factor leading to 

gonadal changes required for reproduction (Dawson and others 2001). 

It should be noted that, in general, birds also use local predictive 

information such as temperature, availability of food, and rainfall to 

make short-term adjustments to reproductive timing(Wingfield 2008), 

although this short-term adjustment is not addressed by this question 

(see Bagne and others 2011).

0

2. Event timing Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

Given the diversity of prey consumed, it is not clear that changes in 

the timing of precipitation and increases in temperature would alter 

the timing of prey availability and abundance, and, hence, fecundity.

0

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

We assumed that at least some individuals that breed on the CNF 

migrate south for winter. For those individuals that do, critical 

resources for breeding (such as food) occur far from where individuals 

over-winter; thus, individuals have no direct information about 

resource abundance on the breeding grounds when they initiate 

migration. 

1

4. Resilience to 

timing 

mismatches 

during breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Peregrine falcons have not been known to rear more than one brood 

per year, but they can lay a second clutch if the first one fails 

relatively early in nesting (White and others 2002).

1

Biotic interactions: American peregrine falcon (Falco peregrinus anatum)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Peregrine falcons consume mostly birds (estimated at 77-99% based 

on frequency) ranging in size from songbirds to small geese, 

occasionally mammals (most frequently bats, microtines, squirrels, 

and rats), and rarely amphibians, fish, and insects (references in 

White and others 2002). They search for prey from a perch or while 

in the air, the majority of which is caught in the air during flight but 

some prey is taken from the water surface or ground (references in 

White and others 2002).

Overall, individuals consume a variety of prey.

0

2. Predators Are important 

predator populations 

expected to change?

Large birds (e.g., eagles and great horned owls) are generally the only 

predators of adult peregrine falcons. Mammals (e.g., bears, fox, and 

cats) and predatory birds (e.g., great horned owls and golden eagles) 

predate nestlings and juveniles (White and others 2002). In the 

-1
46 USDA Forest Service RMRS-GTR-273. 2012.

84

Biotic interactions: American peregrine falcon (Falco peregrinus anatum)

Trait/Quality Question Background info. & explanation of score Points

northeastern United States, owls are responsible for >25% of 

peregrine falcon mortality.

Owls and eagles are expected to be negatively impacted by climate 

change.

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No indication of symbiotic relationship was found in White and 

others (1992).

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change?

Peregrine falcons are known to be hosts to a variety of parasites, 

bacteria, viruses, etc., as reviewed in White and others (2002), 

including avian pox, Newcastle disease, parasitic worms, various 

mites, lice, and flies. Mortality from Clostridium botulinum Type C 

and Trichomonas gallinae acquired from prey (references in White 

and others 2002). No large-scale die-offs from diseases were 

indicated by White and others (2002). Mortality from collisions with 

buildings and vehicles was more substantial than from starvation and 

disease in one study (see White and others 2002).

0

5. Competitors Are populations of 

important 

competing species 

expected to change?

“...relations with great horned owl (Bubo virginianus) are 

inconsistent and puzzling: Some pairs nest close to owls with little 

conflict; others harass owls at every opportunity and occasionally kill 

them; but many pairs of owls dominate and drive off or kill 

neighboring peregrines, adults and young” (White and others 2002). 

No clear pattern of competition with other raptor species, and, as 

indicated by White and others (2002), not easy to categorize 

interactions with other raptors as predator defense versus competitive 

interactions. White and others (2002) reviewed multiple studies for 

interference of other raptor species on peregrine falcons and 

concluded that the studies “indicate little effect on territorial spacing 

per se or direct competition for food; but, depending on structure and 

availability of nest sites (cliffs), individuals of one species can 

influence choice of nest site by other, heterospecific individuals.”

0

Literature Cited

Bagne, K.E., M.M. Friggens, and D.M. Finch. 2011. A system for assessing vulnerability of species 

(SAVS) to climate change. Gen. Tech. Rep. RMRS-GTR-257. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station. 28 p.

Burger, B. 2005. Peregrine Falcon. In: Corman, T.E., and C. Wise-Gervais, eds. The Arizona Breeding 

Bird Atlas. Albuquerque, NM: University of New Mexico Press: 156-157.

Dawson, A., V.M. King, G.E. Bentley, G.F. Ball. 2001. Photoperiodic control of seasonality in birds. 

Journal of Biological Rhythms 16:365-380.

Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 

436:686-688.

Glinski, R.L. 1998. Peregrine Falcon (Falco peregrinus). In: Glinski, R.L., ed. The Raptors of Arizona. 

Tucson: University of Arizona Press.

Kauffman, M.J., W.F. Frick, and J. Linthicum. 2003. Estimation of habitat-specific demography and 

population growth for Peregrine Falcons in California. Ecological Applications 13:1802-1816.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: a comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Stahlecker, D.W. 2010. Peregrine falcon (Falco peregrinus). In: Cartron, J-L.E. Raptors of New Mexico. 

Albuquerque, NM: University of New Mexico Press: 445-459.
USDA Forest Service RMRS-GTR-273. 2012. 47

85

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest Ecological Sustainability Report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

White, C.M., N.J. Clum, T.J. Cade, and W.G. Hunt. 2002. Peregrine Falcon (Falco peregrinus). In: 

Poole, A., ed. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology. Available: 

http://bna.birds.cornell.edu/bna/species/660; doi:10.2173/bna.660.

Wingfield, J.C. 2008. Comparative endocrinology, environment, and global change. General and 

Comparative Endocrinology 157:207-216.

Habitat: Gould’s wild turkey (Meleagris gallopavo mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change?

This sub-species occurs in only a few areas in southwestern United 

States:

— Huachuca Mountains (Arizona);

— Peloncillo Mountains (Arizona and New Mexico);

— Galiuro Mountains; and

— some riparian areas of southeastern Arizona (e.g., Bonita Creek, 

San Pedro River, and San Bernardino Valley; Heffelfinger and 

others 2000).

See Mock and others (2001) and Heffelfinger and others (2000) for a 

review of historical information regarding turkey sub-species in 

Arizona, including introduction and later removal of Merriam’s subspecies in the Huachuca Mountains. Gould’s wild turkeys were reestablished into the Huachuca Mountains in 1983 and 1987 (Mock 

and others 2001) and into the Galiuro Mountains in 1994 and 1997 

(Heffelfinger and others 2000). Mock and others (2001) stated that 

the population at that time was estimated to be around 70-150 

individuals.

In the Sierra Madre Occidental in Mexico, Gould’s wild turkey was 

reported to occur in mountainous pine forest and pine-oak 

woodlands (Aldrich 1967 as cited in York and Schemnitz 2003). In 

western Chihuahua in Mexico, this sub-species reported in evergreen 

woodland and forest communities (Lafon-Terrazas 1997 as cited in 

York and Schemnitz 2003).

In southeastern Arizona, ABBA surveyors reported wild turkeys in 

evergreen oak woodlands, Madrean pine-oak forests, and sycamoredominated drainages (Moors 2005). In the Peloncillo Mountains in 

New Mexico (York and Schemnitz 2003), hens used three types of 

pinyon-juniper woodland in winter: riparian type, savannah type, and 

open woodland where tree species included Chihuahuan pine, 

silverleaf oak, Toumey oak, and Emory oak. In spring, individuals 

used similar areas. Riparian habitats were used heavily in spring and 

summer and were considered to be critical to continued survival of 

this population. Madrean oak woodland was the habitat occupied in 

the Peloncillo Mountains (Potter 1984).

Open grasslands are an important foraging habitat across the range 

of the wild turkey (Gardner 2004). Grassy meadows or forest 

openings with herbaceous vegetation are important for rearing 

broods (Heffelfinger and others 2000).

Gould’s wild turkeys occur, or potential habitat exists, on the 

following EMAs: Peloncillo, Chiricahua, Tumacacori, Santa Rita, 

Huachuca, Pinaleño, Galiuro, and Santa Catalina (USFS 2009). 

Projections of suitable climate for vegetation communities 

2
48 USDA Forest Service RMRS-GTR-273. 2012.

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Habitat: Gould’s wild turkey (Meleagris gallopavo mexicana)

Trait/Quality Question Background info. & explanation of score Points

(Chapter 1) on Coronado NF predicted declines in suitable 

conditions for Madrean forest and woodland, Madrean conifer forest, 

and Rocky Mountain conifer forest, and increases in suitable 

conditions for semi-desert grassland and, to a lesser extent, Sonoran

desert scrub.

Overall, we expected that projected reductions in forest and 

woodland habitats (from drought, pest infestation, and high intensity 

fires) will reduce breeding habitat.

2. Area and 

distribution: nonbreeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

See Habitat, Question 1 above and Habitat, Question 8 below. 2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected to 

change?

Wild turkeys nest on the ground (hen scratches shallow depression; 

Eaton 1992). Trees are important for roosting; in the Peloncillo 

Mountains, Chihuahuan pines were used almost exclusively at 15 

known roost sites (Potter 1984). Wild turkeys, regardless of species, 

select trees with large lateral branches (Schorger 1966 as cited in 

Eaton 1992). Downed logs are important as loafing sites 

(Heffelfinger and others 2000). We considered large trees and 

downed logs to be important to individuals during the breeding 

season (as well as during the non-breeding season), although they 

may not be specifically required to breed successfully.

Eaton (1992) indicated that wild turkeys will drink water where 

available, but did not indicate that this is a requirement; therefore, 

we did not consider standing water a requirement.

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

See Habitat, Question 3 above. 1

5. Habitat quality 

and reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

Little information found. Eaton (1992) indicated a need to synthesize 

the considerable amount of data that exist on wild turkey habitat, 

home range, and movements into a generalized theory of habitat use.

0

6. Habitat quality 

and survival

Are features of the 

habitat associated 

with better survival 

expected to change?

Little information for this sub-species. Mast-producing trees are 

crucial to over-winter survival; a lack of mast results in reduced overwinter survival (Heffelfinger and others 2000). Increased aridity has 

the potential to reduce the number of mast-producing trees.

1

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Several hens of this sub-species in New Mexico had mean annual 

home ranges of 4385 ha based on radio-telemetry observations 

(York and Schemnitz 2003). Movements were greatest in summer; 

the mean maximum distance moved over the course of the study 

(n=3) was 10.9 km. This study was conducted during a drought 

period, and the authors indicated that they expected home ranges 

would be smaller in non-drought periods when food would be more 

available and individuals would not need to travel as far to meet their 

nutritional needs. Juveniles disperse in their first spring, at ~8 

months post-hatch; in Pennsylvania, wild turkeys dispersed at a rate 

of about 8 km per year (references in Eaton 1992).

-1
USDA Forest Service RMRS-GTR-273. 2012. 49

87

Habitat: Gould’s wild turkey (Meleagris gallopavo mexicana)

Trait/Quality Question Background info. & explanation of score Points

We considered Gould’s wild turkey to be highly mobile and able to 

colonize new areas.

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Wild turkeys are non-migratory (Eaton 1992). Potter (1984) did not 

observe separate summer and winter ranges in the Peloncillo 

Mountains. However, in one year, three radio-equipped hens in the 

Peloncillo Mountains moved south approximately 6 km from their

winter home range to an area where they bred (York and Schemnitz 

2003).

0

Physiology: Gould’s wild turkey (Meleagris gallopavo mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Eaton (1992) indicated that wild turkeys will drink water where 

available, but did not indicate that this is a requirement. Feeds for 2-3 

hours after leaving roost at dawn, depending on how abundant food is, 

and again for 2-3 hours before roosting at the end of the day (Eaton 

1992), therefore, not actively foraging during hottest part of day.

No information found on tolerance of extreme heat in Eaton (1992) 

or via a Web of Science database search. With the exception of rare 

cases of extreme heat rises, presumably could tolerate increases of 

several degrees C. Shaded habitat might reduce effects of solar 

radiation on rise in body temperature in the short term, but shade 

from trees expected to decline with time.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather 

or disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity 

of heat waves will effect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality. See also 

Physiology, Question 1.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation regimes 

that influence activity 

period of species 

expected to change?

Feeds for 2-3 hours after leaving roost at dawn, depending on how 

abundant food is, and again for 2-3 hours before roosting at the end 

of the day (Eaton 1992).

No information was found in Eaton (1992) indicating limits on 

activity period relative to high temperatures. With the exception of 

cases of extreme heat rises, it seems unlikely that seasonal or daily 

active periods would be directly and significantly restricted.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

No information in Eaton (1992) to suggest that wild turkeys use 

torpor.

1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

No information in Eaton (1992) to indicate that wild turkeys store 

food.

1
50 USDA Forest Service RMRS-GTR-273. 2012.

88

Physiology: Gould’s wild turkey (Meleagris gallopavo mexicana)

Trait/Quality Question Background info. & explanation of score Points

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No variable life history strategies. 0

8. Reproduction 

in variable 

environments

Can this species 

outlive periods where 

reproduction is 

limited?

While longevity records (i.e., longest-lived birds recorded) for wild 

turkeys include at least two individuals known to have lived in the 

wild at least 10 years, band recoveries of juveniles in West Virginia 

and Florida estimated mean life expectancy as a little more than 1 

year of age, with mean mortality rates per year of 76% and 60% 

(Mosby 1967 as cited in Eaton 1992).

Periods of extreme reductions in rainfall may last 5 years. If this 

condition reduces food resources to the point that birds have 

insufficient food for breeding, most of the population would not 

survive longer than the period of limited reproduction.

1

Phenology: Gould’s wild turkey (Meleagris gallopavo mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Gardner (2004) indicated that wild turkeys are polygamous and that 

breeding behavior begins in late winter as daylight increases. In 

southeastern Arizona, wild turkeys begin breeding in late February 

when males begin displaying to females and it continues into late 

March and early April, at which time hens begin to lay (Moors 2005).

In general, bird species use local predictive information, including 

temperature, availability of food, and rainfall, to make short-term 

adjustments to reproductive timing (Wingfield 2008), although this 

behavior is not addressed by this question (see Bagne and others

2011).

0

2. Event timing Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Reductions in precipitation and increases in temperature may alter 

the abundance of plant food, though it is not clear that timing would 

be altered. Food abundance is covered in Biotic Interactions, 

Question 1.

0

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

Gould’s wild turkeys are year-round residents. Typically, increases 

in food occur in spring, so there is little temporal separation. There 

is no spatial separation since they are year-round residents.

-1

4. Resilience to 

timing 

mismatches 

during breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Wild turkeys generally have just one clutch per season (Eaton 1992). 

Re-nesting after predation is considered common if predation occurs 

during laying or at the beginning of incubation. It is rare that a 

second brood will be initiated after loss of a first brood. 

1
USDA Forest Service RMRS-GTR-273. 2012. 89 51

Biotic interactions: Gould’s wild turkey (Meleagris gallopavo mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important 

food resources 

for this species 

expected to 

change?

Eaton (1992) referred to wild turkeys as “extremely adaptable and catholic in 

feeding.” A literature review indicated that wild turkeys throughout the United 

States and Mexico eat the same general types of food: hard and soft mast, green 

forage, seeds, agricultural crops, and animal matter (Hurst 1992 as cited in

Gardner 2004).

In New Mexico, this sub-species was reported to consume a variety of foods 

across the year (York and Schemnitz 2003). Juniper and manzanita fruits were 

common and, overall, were considered important to this sub-species. In spring, 

this sub-species consumed pinyon nuts and acorns, mustard forbs (early spring), 

and a variety of grass seeds (e.g., pinyon ricegrass and sideoats grama). After 

summer rains, consumption of grass seeds (e.g., barnyard grass) and insects 

increased. Potter (1984) indicated that late monsoonal rains could reduce insects 

and succulent vegetation for young poults.

Although this sub-species eats a variety of foods across the year, the score for 

this question reflects potential reduction in fruit and seed crops. For example, 

reduced crops of acorns are expected as a result of reduced precipitation in the 

short term (Zlotin and Parmenter 2008); and in the long term, less food from 

these sources is expected as a result of reduced tree cover.

1

2. Predators Are important 

predator 

populations 

expected to 

change?

Humans are the most common predator of wild turkeys (Eaton 1992). Potter 

(1984) considered potential predators in the Peloncillo Mountains to be coyote, 

bobcat, mountain lion, golden eagle, and great horned owl. However, inspection 

of coyote scat did not result in any recognizable wild turkey remains. Fox, 

skunk, crow, coati, and feral hog were considered potential nest predators. 

Schemnitz and Zeedyk (1992) noted that no Gould’s wild turkey remains were 

observed in 239 coyote droppings and 83 great horned owl pellets.

Overall, this species has a variety of predators.

0

3. Symbionts Are 

populations of 

symbiotic 

species 

expected to 

change?

No indication of symbiotic relationships was found in Eaton (1992). 0

4. Disease Is prevalence 

of diseases 

known to 

cause 

widespread 

mortality or 

reproductive 

failure in this 

species 

expected to 

change?

Heffelfinger and others (2000) indicated that no diseases had been identified 

in recent work with Gould’s wild turkey populations and translocations from 

Mexico. A variety of viral and bacterial diseases may infect wild turkeys 

(Hopkins and others 1990). Seemingly healthy individuals may be carrying 

pathogenic mycoplasmas (Fritz and others1992). Schemnitz and Zeedyk 

(1992) noted that relatively little is known about diseases and parasites in 

Gould’s wild turkey.

According to references in Eaton (1992), significant diseases for wild turkeys, in 

general, are blackhead (histomoniasis, caused by protozoan Histomonas 

meleagradis), coli-granuloma, fowl pox (caused by a strain of avian pox virus), 

and fowl cholera (caused by bacterium Pasteurella multocida). Approximately 

25% of the wild turkeys found sick or dead in 8 southeastern states were 

diagnosed with avian pox, and ~12% were diagnosed with blackhead disease 

(Davidson and others 1985 as cited in Davidson and Wentworth 1992). It 

appears that it avian pox may be more prevalent in the southeastern United 

States (Davidson and Wentworth 1992).

There is little information to suggest that large outbreaks of these diseases 

have occurred in Gould’s wild turkey. Unclear whether prevalence of the 

diseases might be influenced by climate change.

0
52 USDA Forest Service RMRS-GTR-273. 2012.

90

Biotic interactions: Gould’s wild turkey (Meleagris gallopavo mexicana)

Trait/Quality Question Background info. & explanation of score Points

5. Competitors Are 

populations of 

important 

competing 

species 

expected to 

change?

Potter (1984) indicated that deer are probably strong competitors for food 

only when herds are over populated and the understory becomes 

significantly depleted. Feral hogs are considered potentially strong 

competitors during times of food shortage. Potter (1984) speculated that, in 

the Peloncillo Mountains, wild turkeys might compete with raptors such as 

goshawks and red-tailed hawks for large trees that turkeys need for roosting 

and goshawks need for nesting.

Hurt (1992) stated that while competition for food among turkeys, deer, 

hogs, and many other species occurs, the extent to which it limits wild 

turkey populations is unclear. In one area in Florida, deer and hog 

populations were large and grazing was intensive, but wild turkey 

populations were large as well (Williams 1981 as cited in Hurst 1992).

Overall, species has a variety of competitors.

0

Literature Cited

Bagne, K.E., M.M. Friggens, and D.M. Finch. 2011. A system for assessing vulnerability of species 

(SAVS) to climate change. Gen. Tech. Rep. RMRS-GTR-257. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station. 28 p.

Davidson, W.R., and E.J. Wentworth. 1992. Population influences: diseases and parasites. In: Dickson, 

J.G., ed. The Wild Turkey: Biology and Management. Harrisburg, PA: Stackpole Books: 101-118.

Eaton, S.W. 1992. Wild Turkey (Meleagris gallopavo). In: Poole, A., ed. The birds of North America 

online. Ithaca, NY: Cornell Lab of Ornithology. Available: http://bna.birds.cornell.edu/bna/species/022. 

doi: 10.2173/bna.22.

Fritz, B.A., C.B. Thomas, and T.M. Yull. 1992. Serological and microbial survey of Mycoplasma 

gallisepticum in wild turkeys (Meleagris gallopavo) from six western states. Journal of Wildlife 

Diseases 28:10-20.

Gardner, S. 2004. Strategic plan for Wild Turkey management. Sacramento, CA: California Department 

of Fish and Game. Available: 

http://www.dfg.ca.gov/wildlife/hunting/uplandgame/docs/turkplan_04.pdf.

Heffelfinger, J., B. Wakeling, J. Millican, S. Stone, T. Skiner, M. Fredlake, and M. Adkins. 2000. 

Southeastern Arizona wild turkey management plan. Available: 

http://www.azgfd.gov/pdfs/h_f/management/SoutheasternArizonaWildTurke%20ManagementPlan.pdf.

Hopkins, B.A., J.K. Skeeles, G.E. Houghten, D. Siagle, and K. Gardner. 1990. A survey of infectious 

diseases in wild turkeys (Meleagris gallopavo silvestris) from Arkansas. Journal of Wildlife Diseases 

26:468-472.

Hurst, G.A.1992. Foods and feeding In: Dickson, J.G., ed. The Wild Turkey: Biology and Management. 

Harrisburg, PA: Stackpole Books: 66-83.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: a comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Mock, K.E., T.C. Theimer, B.F. Wakeling, O.E. Rhodes, D.L. Greenberg, and P. Keim. 2001. Verifying 

the origins of a reintroduced population of Gould’s wild turkey. Journal of Wildlife Management 

65:871-879.

Moors, A. 2005. Wild Turkey In: Corman, T.E., and C. Wise-Gervais, ed. The Arizona Breeding Bird 

Atlas. Albuquerque, NM: University of New Mexico Press: 80-81.

Potter, T.D. 1984. Status and ecology of Gould’s turkey. Thesis. New Mexico State University, Las 

Cruces.

Schemnitz, S.D., and W.D. Zeedyk. 1992. Gould’s Turkey In: Dickson, J.G., ed. The Wild Turkey: 

Biology and Management. Harrisburg, PA: Stackpole Books: 350-360.
USDA Forest Service RMRS-GTR-273. 2012. 53

91

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Wingfield, J.C. 2008. Comparative endocrinology, environment, and global change. General and 

Comparative Endocrinology 157:207-216.

York, D.L., and S.D. Schemnitz. 2003. Home range, habitat use, and diet of Gould’s turkeys, Peloncillo 

Mountains, New Mexico. Southwestern Naturalist 48:231-240.

Zlotin, R.I., and R.R. Parmenter. 2008. Patterns of mast production in pinyon and juniper woodlands 

along a precipitation gradient in central New Mexico (Sevilleta National Wildlife Refuge). Journal of 

Arid Environments 72:1562-1572.

Habitat: Montezuma quail (Cyrtonyx montezumae)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change?

The Montezuma quail occurs year-round in the United States in limited 

areas in Arizona, New Mexico, and Texas. Its distribution extends into 

Mexico, where it also occurs year-round. In Arizona, this species is 

found in south and central mountain ranges and has been reported in: 

Baboquivari, San Luis, Pajarito, Atascosa, Canelo Hills, Tumacacori, 

Santa Rita, Patagonia, Huachuca, and Chiricahua Mountains, with 

smaller populations in Catalina, Rincon, Galiuro, Dragoon, Pinaleño, 

and Whetstone Mountains and in the forested Mogollon Rim north of 

Gila River Mountains (references in Stromberg 2000). ABBA 

observers recently confirmed this species presence in the Peloncillo, 

Chiricahua, Baboquivari, Rincon, and Pinaleño Mountains; it was not 

observed in the Santa Catalina, Galiuro, or Pinal Mountains, but this 

species often goes undetected when present (Corman and Wise-Gervais 

2005).

Closely associated with oak woodlands. In Arizona, individuals chose 

areas with higher grass cover and more trees than randomly available 

(Bristow and Ockenfels 2004). Species occurs in a variety of open 

woodlands but depends on an understory of grasses and forbs 

(Corman and Wise-Gervais 2005). During ABBA surveys (Corman 

and Wise-Gervais 2005), 43% of observations were in Madrean 

evergreen oak woodlands containing alligator juniper and several 

species of oak (Arizona white, Emory, Mexican blue, and netleaf). 

The second most observations (13%) were in adjacent semi-arid 

grassland. Also detected in Madrean pine-oak woodlands (understory 

of evergreen oaks, juniper, pinyon, and Arizona madrone) and in 

canyons containing cottonwood, willow, Arizona sycamore, Douglasfir, maple, and pines.

Nests on the ground. Nests found in cool canyons as well as drier 

grassy and chaparral slopes (Corman and Wise-Gervais 2005). First 

broods usually seen mid-July (Wallmo 1954) but, in some years, not 

until August (Stromberg 2000). Brood production varies among years, 

in part as a function of summer rains (Brown 1979).

This species occurs, or potential habitat exists, on 4 of the EMAs on 

CNF: Peloncillo, Chiricahua, Tumacacori, and Santa Rita (USFS 2009).

Projections of suitable climate for vegetation communities forest wide 

(Chapter 1) predicted declines in suitable climate for all plant 

community types, with the exception of increases of suitable climate 

for semi-desert grassland and small increases in Sonoran desert scrub 

(present in small amounts on the CNF).

Given the projected decline in woodland habitats, we predicted that 

habitat for this species will decrease.

2
54 USDA Forest Service RMRS-GTR-273. 2012.

92

Habitat: Montezuma quail (Cyrtonyx montezumae)

Trait/Quality Question Background info. & explanation of score Points

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Same as breeding habitat (see Habitat, Question 1 above). 2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected to 

change? 

According to Brown (1979), this species requires perennial bunch 

grasses for nest construction and concealment. Grasslands are 

expected to increase over time. However, we considered it unlikely 

that the species would find open grasslands suitable for nesting 

without the woodland environment. 

-1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

Grass cover is also important in the non-breeding season. According 

to Stromberg (1990), this species roosts at night on the ground in 

shallow cups; 20-night roosts were located in patches of tall grass 

(tanglehead [Heteropogon contortus]) and typically near rocks where 

tall grass created a roof. 

-1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

No information in Stromberg (2000) on habitat factors associated 

with differential reproductive success.

0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information in Stromberg (2000) on habitat factors associated 

with differential survival.

0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Although little is known about its dispersal, this species appears to 

undergo fewer movements than many other species of birds. 

Stromberg (1990) indicated that initial dispersal distance is probably 

very limited given that covey home ranges after breeding are small 

(1-2 ha). Pairs are often found in the same small areas (50 m2

) for 

several years (Bishop 1964 as cited in Stromberg 2000). Also, this 

species mostly walks and runs as opposed to flying.

We scored as “0” because we considered this species “moderately 

mobile” (expected lower mobility than bird species that migrate long 

distances or fly more frequently).

0

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

No elevational seasonal migrations are documented (Stromberg 2000). 0

Physiology: Montezuma quail (Cyrtonyx montezumae)

Trait/Quality Question Background info. & explanation of score Points

1. Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Occupies arid habitats and Arizona and New Mexico are the 

northern limits of this species’ distribution. It appears that this 

species does not need to drink free water to survive (Leopold and

McCabe 1957 as cited in Stromberg 2000). Not known to bathe in 

0
USDA Forest Service RMRS-GTR-273. 2012. 55

93

Physiology: Montezuma quail (Cyrtonyx montezumae)

Trait/Quality Question Background info. & explanation of score Points

water even when shallow water is available (Stromberg 2000).

No information found on tolerance of extreme heat in Web of 

Science database, although relatively little is known about this 

species overall. With the exception of cases of extreme heat rises, 

presumably could tolerate increases of several degrees C. Shaded 

habitat (oaks) might reduce effects of solar radiation on rise in body 

temperature in the short term, but shade from trees expected to 

decline with time.

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed 

in reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather 

or disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increased frequency of heat waves is predicted for the southwestern 

United States. Overall, it is not clear to what extent timing and 

intensity of heat waves will effect survival and reproduction. We 

considered it unlikely that heat waves would cause widespread 

mortality for this species. See also Physiology, Question 1.

This species is a year-round resident, so not exposed to potential 

changes in storms along a migratory route. 

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation regimes 

that influence activity 

period of species 

expected to change?

Individuals forage more in morning and evening; during the middle 

of the day, they rest, dust, preen, and occasionally dig for food 

(Stromberg 2000).

No information found in Stromberg (2000) indicating limits on 

activity period relative to high temperatures. With the exception of 

cases of extreme heat rises, it seems unlikely that seasonal or daily 

active periods will be directly restricted to the point of significantly 

reducing survival.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

No information found to indicate that this species uses torpor. 1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

No information found in Stromberg (2000) to indicate that this 

species stores food.

1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No variable life history strategies. 0

8. Reproduction 

in variable 

environments

Can this species 

outlive periods where 

reproduction is 

limited?

Very little information about longevity in the wild; in captivity, can 

live as long as 6-7 years (Stromberg 2000) and we assumed that in 

the wild, mean lifespan is much shorter.

Periods of extreme reductions in rainfall may last 5 years. If this 

condition reduced food resources to the point that birds have 

insufficient food for breeding, it is expected that most of the 

population would not survive longer than the period of limited 

reproduction.

1
56 USDA Forest Service RMRS-GTR-273. 2012. 94

Phenology: Montezuma quail (Cyrtonyx montezumae)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species use 

temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Nesting coincides with summer rains and is reported to be delayed 

until as late as August if there is little monsoonal rain (Corman and 

Wise-Gervais 2005). Breeding appears to be triggered by increased 

humidity and availability of newly emergent vegetation and insects 

consumed by adults.

1

2. Event timing Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

See also Phenology, Question 1. Fall covey sizes were positively 

correlated with summer monsoon rainfall (Stromberg 2000) 

suggesting a possible association between precipitation and food 

abundance.

It is unclear whether the timing and amount of monsoonal rains will 

change, but change is considered a potential threat given that 

reproduction in this species appears to be tied to monsoonal rains. 

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate activities 

and discrete events 

that provide critical 

resources?

This species is a year-round resident in Arizona. Typically, 

increases in food abundance (a critical resource) occur in spring, so 

there is little temporal separation. There is no spatial separation 

since the species is a year-round resident.

-1

4. Resilience to 

timing 

mismatches 

during breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

In the wild, no second broods were documented by Leopold and

McCabe (1957 as cited in Stromberg 2000).

1

Biotic interactions: Montezuma quail (Cyrtonyx montezumae)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

This species feeds on the ground by digging with its feet 

(Stromberg 2000). During winter, roots of wood sorrel [Oxalis

spp.] and underground tubers of sedges (Cyperus spp.) are a large 

proportion of the diet (Stromberg 2000). Adds acorns to the diet in 

spring and summer; in some areas, may eat acorns year-round. In 

fall and winter, also eats seeds of a variety of species (e.g., panic 

grass [Panicum spp.], morning glory [Ipomoea spp.], nightshade 

[Solanum spp.], brodiaea [Brodiaea spp.], yucca, and lupine

[Lupinus spp.]). Acorns, Oxalis spp., and Cyperus spp. constitute 

nearly 80% of year-round diet based on crop analysis (Stromberg 

2000).

Insects are important in summer, particularly grasshoppers, ants, 

and beetles (Coleoptera); (references in Stromberg 2000). 

Stromberg (2000) summarized diet information and indicated that 

diet differences between individuals in the Huachuca Mountains 

and in the Santa Rita Mountains reflect differences in plant species 

composition. Individuals dig for food most commonly in duff and 

leaves under bushes or trees (Bishop 1964).

Overall, unclear whether Oxalis spp. and Cyperus spp. would 

decrease in the future. This score reflects the potential reduction in 

1
USDA Forest Service RMRS-GTR-273. 2012. 57

95

Biotic interactions: Montezuma quail (Cyrtonyx montezumae)

Trait/Quality Question Background info. & explanation of score Points

acorn crops; reduced acorn crops are expected in the short term as a 

result of reduced precipitation (Zlotin and Parmenter 2008), and 

fewer acorns are expected in the long term as a result of reduced 

tree cover. 

2. Predators Are important 

predator populations 

expected to change?

A variety of predators are known and/or expected. Documented 

predation by Cooper’s hawks, northern goshawks, and coyotes (egg 

predation) and probable egg predation by various skunk species 

(Stromberg 2000). 

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No indication of symbiotic relationships found in Stromberg 

(2000).

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

No information on diseases and parasites for wild birds; captive 

birds show ability to contract diseases seen in captive quail 

(Stromberg 2000).

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Stromberg (2000) found no information on inter-specific 

competition. 

0

Literature Cited

Bristow, K.D., and R.A. Ockenfels. 2004. Pairing season habitat selection by Montezuma quail in 

southeastern Arizona. Journal of Range Management 57:532-538.

Brown, D.E. 1979. Factors influencing reproductive success and population densities in Montezuma 

quail. Journal of Wildlife Management 43:522-526.

Corman, T.E., and C. Wise-Gervais, eds. 2005. Arizona Breeding Bird Atlas. Albuquerque, NM: 

University of New Mexico Press.

Stromberg, M.R. 2000. Montezuma Quail (Cyrtonyx montezumae). In: Poole, A., ed. The birds of North 

America online. Ithaca, NY: Cornell Lab of Ornithology. Available: 

http://bna.birds.cornell.edu/bna/species/524 doi:10.2173/bna.524.

Stromberg, M.R. 1990. Habitat, movements and roost characteristics of Montezuma Quail in southeastern

Arizona. Condor 92:229-236.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Wallmo, O.C. 1954. Nesting of Mearns quail in southeastern Arizona. Condor 56:125-128.

Zlotin, R.I., and Parmenter, R.R. 2008. Patterns of mast production in pinyon and juniper woodlands 

along a precipitation gradient in central New Mexico (Sevilleta National Wildlife Refuge). Journal of 

Arid Environments 72:1562-1572.
58 USDA Forest Service RMRS-GTR-273. 2012.

96

Habitat: Western yellow-billed cuckoo (Coccyzus americanus occidentalis)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or location 

of the associated 

vegetation type used 

for breeding activities 

by this species 

expected to change?

Taxonomic note: There has been some disagreement over whether 

there are valid eastern and western sub-species. The U.S. Fish and 

Wildlife Service (2001) cited the results of Franzreb and Laymon 

(1993) and recognized a western sub-species (C. a. occidentalis) 

whose listing under the Endangered Species Act was “warranted 

but precluded by higher priority listing actions.” Birds in the north 

and extreme western portions of Texas to the Pacific Coast were 

assigned as C. a. occidentalis, and other cuckoos in North America 

as C. a. americanus by Ridgeway (1887 as cited in USFWS 2001).

Yellow-billed cuckoos prefer “open woodland with clearings and 

low, dense shrubby vegetation” (Hughes 1999). In Arizona (and 

elsewhere in the Southwest), they prefer “desert riparian woodlands 

(Sonoran Zones) comprised of willow, Fremont cottonwood, and 

dense mesquite” (Hughes 1999) using cottonwoods extensively for 

foraging and often placing their nests in willows. Nests have also 

been found in orchards next to river bottoms in Arizona (Hughes 

1999). In western United States, nests are also located in Fremont 

cottonwood, mesquite, hackberry, soapberry, alder, and cultivated 

fruit trees. For 2-3 weeks before breeding, yellow-billed cuckoos 

may occupy upland vegetation, including pinyon, oak, juniper, and 

manzanita (Hamilton and Hamilton 1965; Hughes 1999). In arid 

regions, individuals are restricted to breeding in “river bottoms, 

ponds, swampy areas, and damp thickets with relatively high 

humidity” (Hughes 1999).

This species occurs, or potential habitat exists, on two of the EMAs 

on CNF: Santa Rita and Huachuca (USFS 2009). Projections of 

suitable climate for vegetation communities forest-wide (Chapter 1) 

predicted declines in suitable climate for all plant community types, 

with the exception of increases of suitable climate for semi-desert 

grassland and small increases in Sonoran desert scrub (present in 

small amounts on the CNF).

Riparian habitats are predicted to decline due to decreased stream 

flows on average (increased aridity and decreased snowpack), 

increased fire frequency, and possible changes to the flood regime 

(earlier peak flows).

2

2. Area and 

distribution: 

non-breeding

Is the area or location 

of the associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Yellow-billed cuckoos winter primarily in South America. The 

wintering range of individuals nesting in the western United States 

is not as well known as that of eastern sub-species, but it is likely 

that they travel to northwestern South America (Hughes 1999). For 

the species overall, wintering birds occupy a wide variety of 

forests, woodlands, and scrubby areas, preferring “woody 

vegetation bordering fresh water” (Rappole and others 1983 and 

Stotz and others 1996 as cited in Hughes 1999). Winter habitat for 

the species is reported as mangroves and riparian habitats in 

Surinam and Guyana (references in Hughes 1999). In Venezuela, 

observed in “open woodland, second growth, xerophytic areas, 

thickets, and páramo” (Meyer de Schauensee and Phelps 1978 as 

cited in Hughes 1999). Assuming that this sub-species winters in 

northwestern South America, this would be some of the expected 

areas occupied. Also found in sub-humid and scrub forest, 

xerophytic and mesophytic forest edges in other South American 

locations (Hayes 1995 as cited in Hughes 1999).

Overall, future trends in temperature and precipitation in many 

areas in South America are not clear. Magrin and others (2007) 

noted some of the observed and possible changes: (1) temperature 

increases are occurring in many areas (glacier retreat in Columbia, 

Peru, and Ecuador); (2) climate projected to become more suitable 

2
USDA Forest Service RMRS-GTR-273. 2012. 59

97

Habitat: Western yellow-billed cuckoo (Coccyzus americanus occidentalis)

Trait/Quality Question Background info. & explanation of score Points

for tropical vegetation toward the south, and the northern portions 

of South America drier; (3) tropical forests will be replaced by 

savannahs and a experience an increased risk of fire; (4) mangroves 

are threatened by sea level rise; and (4) extreme weather events 

have been reported, including intense rainfall events in Venezuela 

(1999 and 2005), flooding in the Argentinean Pampas (2000, 2002), 

and drought in the Amazon (2005), among others.

Overall, preferred wintering habitat for yellow-billed cuckoos

(woody vegetation near water) in northern South America is likely 

to decline due to drying conditions and expected decrease of 

mangroves. 

3. Habitat 

components: 

breeding

Are specific habitat 

components required 

for breeding expected 

to change? 

Water appears to be important, directly or indirectly. In California, 

this sub-species was reported to not breed where water is not within 

100 m (Gaines 1974 as cited in Hughes 1999). For nesting, suitably 

sized trees with horizontal branches are required (Laymon 1980 as 

cited in Hughes 1999). The majority of nests found by ABBA 

observers (Corman and Wise-Gervais 2005) were along perennial 

drainages. Hamilton and Hamilton (1965) indicated that 

“permanent water or some environmental factor closely correlated 

with it is a basic requirement.”

Decrease in average annual stream flows (from reduced 

precipitation) likely to increase distance to water and reduce 

suitably sized trees.

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components required 

for survival during 

non-breeding periods 

expected to change?

None reported in Hughes (1999). 0

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

No information in Hughes (1999). 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information in Hughes (1999). 0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to disperse?

Both sexes are highly mobile (populations that breed in Arizona are 

migratory). We considered birds to be very mobile due to their 

capacity for flight and, thus, overall able to colonize new areas.

-1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Yellow-billed cuckoos are long-distance migrants (winter in South 

America). Migratory routes of western birds are not as well known 

as for eastern populations. Yellow-billed cuckoos are fairly 

common spring and fall migrants in Oaxaca, Mexico (Hughes 

1999).

1
60 USDA Forest Service RMRS-GTR-273. 2012.

98

Physiology: Western yellow-billed cuckoo (Coccyzus americanus occidentalis)

Trait/Quality Question Background info. & explanation of score Points

1. Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

In terms of latitude, southern Arizona is in the southeastern portion 

of the sub-species’ range in the United States, and is roughly the 

southern one-third of the species’ breeding range. Yellow-billed 

cuckoos formerly bred throughout most of North American from 

southern Canada to northern Mexico (USFWS 2001).

In Arizona, Hamilton and Hamilton (1965) observed an adult 

shading nestlings in the nest at midday. An incubating adult has 

been observed panting on hot days (Hughes 1999). Hughes (1999) 

found no information on water drinking for this species.

With the exception of cases of extreme heat rises, presumably could 

tolerate increases of several degrees C. Shaded habitat might reduce 

effects of solar radiation on rise in body temperature, although 

shade from trees expected to decline with time.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed 

in reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather 

or disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Hughes (1999) reported that migrants may be affected by adverse 

weather. Veit and Petersen (1993 as cited in Hughes 1999) reported 

that in 1954, many weakened and starving yellow-billed cuckoos 

were observed in northeastern states following 3 hurricanes. 

Hurricane intensity is expected to increase, but frequency

predictions are inconsistent (Emanuel 2005); frequency increase 

would likely be more detrimental overall for migrating birds since 

hurricane-level winds already are a concern for migrants.

See also Physiology, Question 1.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation regimes 

that influence activity 

period of species 

expected to change?

See Physiology, Question 1. With the exception of cases of extreme 

heat rises, seems unlikely for seasonal or daily active periods to be 

restricted to the point of significantly reducing survival.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

No reports of torpor in Hughes (1999), which reported that 

metabolism and temperature regulation were poorly known. No 

citations of torpor in Web of Science database. We assumed that 

yellow-billed cuckoos do not use torpor.

1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Feeds most often on insects (Hughes 1999). Hughes (1999) 

reported no food storage.

1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No variable life history strategies. 0

8. Reproduction 

in variable 

environments

Can this species 

outlive periods where 

reproduction is 

limited?

Little information on longevity; rate of recapture of banded 

individuals is very low (Hughes 1999). Records from Canadian 

Wildlife Service indicated a few banded birds at least 4 years old 

(Hughes 1999). 

1
USDA Forest Service RMRS-GTR-273. 2012. 61

99

Phenology: Western yellow-billed cuckoo (Coccyzus americanus occidentalis)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species use 

temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Western yellow-billed cuckoos are predictable breeders, meaning 

the breeding season occurs at the same time each year (i.e., spring). 

In predictable breeders, photoperiod is the predominant proximate 

factor leading to gonadal changes required for reproduction 

(Dawson and others 2001). Birds, in general, use local predictive 

information, such as temperature, availability of food, and rainfall, 

to make short-term adjustments to reproductive timing (Wingfield 

2008), although this short-term adjustment is not addressed by this 

question (see Bagne and others 2011). No information in Hughes 

(1999) on direct influence of temperature and moisture on cues for 

this species. 

0

2. Event timing Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Food abundance in spring is an important factor driving fecundity in 

bird species breeding in temperate regions (review by Martin 1987). 

Typically, increases in insect abundance (a critical resource) occur 

in spring; changes in the timing of precipitation and increases in 

temperature have the potential to alter the timing of insect 

availability and abundance and, hence, fecundity.

In Indiana, more yellow-billed cuckoo nests were found and the 

peak of egg-laying was earlier in years when eastern tent caterpillars 

and cicadas (either periodical or annual species) were abundant 

(Nolan and Thompson 1975). Unclear whether a similar pattern 

exists in Arizona.

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate activities 

and discrete events 

that provide critical 

resources?

The yellow-billed cuckoo is a migrant that occurs in the CNF in the 

breeding season. Critical resources for breeding occur far from 

where individuals over-winter; thus, individuals have no direct 

information about resource abundance on the breeding grounds 

when they initiate migration from their wintering grounds. Anders 

and Post (2006) suggested that warmer winters may lead to earlier 

spring peaks in the abundance of Lepidoptera species that the 

yellow-billed cuckoos feed on which could lead to it missing the 

peak in food abundance since individuals arrive fairly late to the 

breeding grounds.

1

4. Resilience to 

timing 

mismatches 

during breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Populations in the western United States are believed to raise only 

one brood per season; breeding season in the west is 1-3 months 

shorter than in the east (Hughes 1999).

1

Biotic interactions: Western yellow-billed cuckoo (Coccyzus americanus occidentalis)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Yellow-billed cuckoos feed primarily on large insects such as 

caterpillars, grasshoppers, crickets, katydids, and cicadas; also feed 

on small lizards, frogs, eggs, and nestlings (Hughes 1999). On 

wintering grounds, they also feed on fruits and seeds, as well as 

insects (Hughes 1999). In Arizona, Hamilton and Hamilton (1965) 

observed consumption of what appeared to be large moth larvae and 

katydids; the authors stated “the caterpillar of the Condalia bush...is 

the main item taken to the young.”

Local influxes of yellow-billed cuckoos have been observed in the 

eastern United States when insect abundance has been high (Veit 

0
62 USDA Forest Service RMRS-GTR-273. 2012.

100

Biotic interactions: Western yellow-billed cuckoo (Coccyzus americanus occidentalis)

Trait/Quality Question Background info. & explanation of score Points

and Peterson 1993 as cited in Hughes 1999). Peak numbers of 

yellow-billed cuckoos have been observed following forest tent 

caterpillar irruptions and gypsy moth outbreaks in Michigan and 

cicadas in Indiana and Kansas (various citations in Hughes 1999). In 

eastern populations, Veit and Petersen (1993 in Hughes 1999) 

considered it likely that more young are raised successfully during 

years of high caterpillar abundance. However, Hamilton and 

Hamilton (1965) made no reference to such phenomena related to 

peaks in insect abundance in Arizona and provided little information 

on tent caterpillar outbreaks.

Yellow-billed cuckoo populations in the eastern United States were 

found to be lower after warmer years, but the relationship with food 

is unclear (Anders and Post 2006).

2. Predators Are important 

predator populations 

expected to change?

Overall, there is a suite of predators. Raptors may be an important 

predator during migration and upon arrival on wintering grounds 

(Hector 1985 as cited in Hughes 1999). Snakes, mammals, and avian 

predators are considered to be egg and nestling predators (Hughes 

1999).

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

Hughes (1999) did not identify important symbiotic relationships. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Numerous diseases and parasites have been documented (see 

Hughes 1999), but we found no information that indicates significant 

negative effects on populations.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Nests are occasionally parasitized by brown-headed cowbird 

(Molothrus ater) and, in south Texas, rarely by bronzed cowbirds 

(Molothrus aeneus; citations in Hughes 1999). Hughes (1999) 

indicated it is unlikely that a cowbird chick would fledge 

successfully and that cowbirds usually select hosts with a longer 

nestling period than its own nestlings and cuckoos have a shorter 

nestling period (7-9 days).

Overall, cowbird parasitism is probably not a significant issue for 

this species.

Note: The yellow-billed cuckoo is an intraspecific brood parasite, 

occasionally laying eggs in nests of conspecifics (Hughes 1999).

0

Literature Cited

Anders, A.D., and E. Post. 2006. Distribution-wide effects of climate on population densities of a 

declining migratory bird. Journal of Animal Ecology 75:221-227.

Bagne, K. E., M.M. Friggens, and D.M. Finch. 2011. A system for assessing vulnerability of species 

(SAVS) to climate change. Gen. Tech. Rep. RMRS-GTR-257. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station. 28 p.

Corman, T.E., and C. Wise-Gervais, eds. 2005. The Arizona Breeding Bird Atlas. Albuquerque, NM: 

University of New Mexico Press.

Dawson, A., V.M. King, G.E. Bentley, and G.F. Ball. 2001. Photoperiodic control of seasonality in birds. 

Journal of Biological Rhythms 16:365-380.

Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 

436:686-688.
USDA Forest Service RMRS-GTR-273. 2012. 63

101

Franzreb, K.E., and S.A. Laymon. 1993. A reassessment of the taxonomic status of the yellow-billed 

cuckoo. Western Birds 24:17-28.

Hamilton III, W. J. and M. E. Hamilton. 1965. Breeding characteristics of yellow-billed cuckoos in 

Arizona. Proceedings of the California Academy of Sciences 32:405-432.

Hughes, J.M. 1999. Yellow-billed Cuckoo (Coccyzus americanus). In: Poole, A., ed. The birds of North 

America online. Ithaca, NY: Cornell Lab of Ornithology. Available: 

http://bna.birds.cornell.edu/bna/species/418.

Magrin, G., C. Gay García, D. Cruz Choque, J.C. Giménez, A.R. Moreno, G.J. Nagy, C. Nobre, and A. 

Villamizar. 2007: Latin America. In: Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden, 

and C.E. Hanson, Eds. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of 

Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.

Cambridge, United Kingdom: Cambridge University Press: 581-615.

Martin, T.E. 1987. Food as a limit on breeding birds: a life-history perspective. Annual Review of 

Ecology and Systematics 18:453-487.

Nolan, V., and C.F. Thompson. 1975. The occurrence and significance of anomalous reproductive 

activities in two North American non-parasitic cuckoos Coccyzus sp. Ibis 117:496-503.

U.S. Fish and Wildlife Service [USFWS]. 2001. 12-month finding for a petition to list the yellow-billed 

cuckoo (Coccyzus americanus) in the western continental United States. Federal Register 66:38611-

38626.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Wingfield, J.C. 2008. Comparative endocrinology, environment, and global change. General and 

Comparative Endocrinology 157:207-216.

Habitat: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change?

U.S. breeding distribution is limited to small areas in southern 

Arizona and New Mexico (observations in Texas thought to be nonbreeding or post-breeding birds; Kunzmann and others 1998). Most 

or all of the U.S. population is migratory (Kunzmann and others 

1998). In Arizona, reported to breed regularly in Atascosa, 

Chiricahua, Huachuca, and Santa Rita Mountain ranges (Taylor 1994

as cited in Kunzmann and others 1998). In United States, breeding 

habitat includes high-elevation pine and pine-oak forests and 

Arizona sycamore riparian woodland (Hall 1996 as cited in 

Kunzmann and others 1998). At the home range level, “trogons 

acted as a pine-oak woodland upland species, and used riparian areas 

with sycamore” while nesting primarily in large sycamores and, to a 

lesser extent, in oak trees (Kunzmann and others 1998). In Arizona, 

abundance is greatest in canyons with the greatest cover of 

“sycamore riparian and edge vegetation, pinyon pine riparian and 

edge vegetation, juniper riparian, pine riparian, and juniper upland 

vegetation” (Hall 1996 as cited in Kunzmann and others 1998). 

Canyons occupied by trogons in Arizona have water flow substantial 

enough to support sycamore trees; prior work by Taylor (multiple 

references in Kunzmann and others 1998) suggested that canyons 

with perennial water are used preferentially, although Hall (1996) 

found no relationship between abundance and type of water flow 

(perennial, intermittent, and ephemeral). In southwestern Arizona 

mountains, most nests are within 300 m of perennial water (multiple 

references in Kunzmann and others 1998).

This species occurs, or potential habitat exists, on 5 of the EMAs on 

CNF: Peloncillo, Chiricahua, Tumacacori, Santa Rita, and Huachuca 

2
64 USDA Forest Service RMRS-GTR-273. 2012.

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Habitat: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

(USFS 2009). Projections of suitable climate for vegetation 

communities forest-wide (Chapter 1) predicted declines in suitable 

climate for all plant community types, with the exception of increases 

of suitable climate for semi-desert grassland and small increases in 

Sonoran desert scrub (present in small amounts on the CNF).

Riparian habitats predicted to decline due to decreased stream flows, 

on average, and increased aridity. Increased risk of fire is also 

predicted, which is expected to reduce riparian habitats.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Some winter observations of this species in Arizona (Kunzmann and 

others 1998), but generally, winter range (of migrants and yearround residents) is in Mexico and Central America (including 

Guatemala, Honduras, and El Salvador), where year-round residents 

occupy the same kinds of habitats in winter as for breeding. 

Therefore, we assumed that wintering habitats for migrants that 

breed in the United States are the same as winter habitats for yearround residents. In Mexico, this habitat ranges from lowlands, 

foothills, and mountains; more specifically, this includes arid to 

semi-arid woodland and thorn forest to high-elevation pine and pineoak forests (Howell and Webb 1995 as cited in Kunzmann and 

others 1998).

Specific projections for change in vegetation in Mexico and Central 

America were not found. Increases in temperature have been 

projected for Central America (Magrin and others 2007: Fig. 13.1, 

Table 13.4). Observed trends in rainfall for Central America vary 

from increases in some areas to decreases in other areas (Magrin and 

others 2007: Fig. 13.1)

Given the broad geographic scale over which this species potentially 

occurs in winter (Mexico and Central America) and the absence of 

specific vegetation projections for those areas, it is difficult to 

predict how habitat will respond. We took the conservative approach 

by assuming that increases in temperature will lead to conversion of 

semi-arid regions to arid, and that reduced high-elevation pine and 

pine-oak forests will reduce wintering habitat for this species. 

2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected to 

change?

Commonly nests in abandoned woodpecker (e.g., northern flicker) 

cavities (Kunzmann and others 1998). Does not excavate its own 

cavities so it depends on those created by other species. Old reports 

of this species nesting in banks but Kunzmann and others (1998) 

found no reliable evidence to support this. Elegant trogon pairs try 

out different cavities at start of season (Kunzmann and others 1998), 

indicating that pairs are discriminating (criteria for discrimination 

unreported). In Arizona, nests may be found in silverleaf oak, 

Arizona white oak, Apache pine, Chihuahuan pine, and sycamore. 

Hakes (1983 as cited in Kunzmann and others 1998) showed that 

this species did not use any of 30 nest boxes placed in the Huachuca 

Mountains over 4 years.

Riparian trees suitable for cavities are expected to decline (see 

Habitat, Question 1 above) due to projected increase in wildfires. 

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

No habitat components for non-breeding season identified in 

Kunzmann and others (1998).

0

5. Habitat 

quality and 

Are features of the 

habitat associated 

Higher nest success was observed in larger-diameter trees and in 

trees with taller vegetation south of the nest tree (Hall 1996 as cited 

1
USDA Forest Service RMRS-GTR-273. 2012. 65

103

Habitat: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

reproduction with better 

reproductive success 

expected to change?

in Kunzmann and others 1998); no relationship was found between 

nest success and plant species surrounding the nest, nor the average 

distance to campgrounds, buildings, trails, and water, nor the density 

of trogons in the area.

Large trees are expected to be less abundant in the future due to 

reduced precipitation and increased fires.

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information in Kunzmann and others (1998). 0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Kunzmann and others (1998) found no data on initial dispersal from 

natal site. Both sexes are highly mobile given that populations in 

Arizona are migratory.

We considered birds to be very mobile due to their capacity for flight 

and, thus, overall able to colonize new areas.

-1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

This species migrates long distances. Individuals breeding in 

Arizona winter in Mexico and Central America.

1

Physiology: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are physiological 

thresholds related to 

temperature or 

moisture expected to 

change?

Unknown whether this species needs drinking water; has been 

observed drinking, but paucity of observations suggests that water is 

not a requirement (Kunzmann and others 1998). Need for bathing 

unknown.

Arizona is the northern limit of this species’ range. The Trogonidae 

family is not tolerant of cold temperatures (Kunzmann and others 

1998). When migrant individuals arrive in Arizona to breed, 

mountain ranges used by this species are nearly free of snow 

(Kunzmann and others 1998). The elegant trogon’s northern 

distribution may be limited due to its sensitivity to cold temperatures 

(Marshall 1957 as cited in Kunzmann and others 1998). Low resting 

metabolic rate of a related species (Trogon rufus; black-throated 

trogon) relative to other bird families may reflect low ability to 

generate heat (Bennett and Harvey 1987 as cited in Kunzmann and 

others 1998); elegant trogon may have similar physiology.

With the exception of cases of extreme heat rises, presumably could 

tolerate increases of several degrees C. Shaded habitat might reduce 

effects of solar radiation on rise in body temperature, although shade 

from trees expected to decline with time.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather 

or disturbance events 

that result in direct 

mortality or 

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity 

of heat waves will effect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality for this 

0
66 USDA Forest Service RMRS-GTR-273. 2012.

104

Physiology: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

reproductive failure 

expected to change?

species. Hurricane intensity is expected to increase under global 

climate change, but frequency predictions are inconsistent (Emanuel 

2005); frequency increase likely more detrimental overall to 

migrating populations than intensity since hurricane-level winds 

already detrimental to migrants. See also Physiology, Question 1.

No information in Kunzmann and others (1998) on significant 

mortality or failed reproduction due to weather.

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation regimes 

that influence activity 

period of species 

expected to change?

See Physiology, Question 1. With the exception of cases of extreme 

heat rises, seems unlikely for seasonal or daily active periods to be 

restricted to the point of significantly reducing survival.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

No reports of torpor in Kunzmann and others (1998). No citations of 

torpor for elegant trogon in Web of Science database. We assumed 

that this species does not use torpor.

1

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Food storage not known to occur (Kunzmann and others (1998). 1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No variable life history strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods where 

reproduction is 

limited?

Kunzmann and others (1998) found no data on longevity. Based on 

data for other bird species of this size, not expected to be longer than 

a few years.

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that birds have 

insufficient food for breeding, most of the population would not 

survive longer than the period(s) of limited reproduction.

1

Phenology: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species use 

temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival?

This species is a predictable breeder, meaning its breeding season 

occurs at the same time each year (i.e., spring). In predictable 

breeders, photoperiod is the predominant proximate factor leading to 

gonadal changes required for reproduction (Dawson and others 

2001). On the other hand, nesting in individuals of this species in 

Alamos, Mexico, reported to be timed with summer rainy season 

(Short 1974 as cited in Kunzmann and others 1998), so it is possible 

that this species uses moisture as a cue.

1

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

Food abundance in spring is an important factor driving fecundity in 

bird species breeding in temperate regions (review by Martin 1987). 

Typically, increases in insect abundance (a critical resource) occur in 

1
USDA Forest Service RMRS-GTR-273. 2012. 67

105

Phenology: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

discrete events that 

are expected to 

change? 

spring; changes in the timing of precipitation and increases in 

temperature have the potential to alter the timing of insect 

availability and abundance and, hence, fecundity. In Arizona, 

breeding initiation dates reported variable among pairs in a 2-year 

study, with nests begun in May, June, and July (Kunzmann and 

others 1998).

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate activities 

and discrete events 

that provide critical 

resources?

Migrant species that occurs in the CNF in the breeding season. 

Critical resources for breeding occur far from where individuals 

over-winter; thus, individuals have no direct information about 

resource abundance on the breeding grounds when they initiate 

migration from their wintering grounds. 

1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

In Arizona, most pairs rear one brood per season (Kunzmann and 

others 1998).

1

Biotic interactions: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Main foods are fruit, grasshoppers, and other insects (Kunzmann and 

others 1998). Fruits include cherries (in orchards), canyon grapes, 

tropical figs, southwestern chokecherry, and birchleaf buckthorn. 

Insects include caterpillars, adult and larval butterflies and moths, and 

species of various other adult and larval insect families (Kunzmann 

and others 1998). In Arizona, this species mainly forages in oak trees 

and fruit-bearing plants, when available (Taylor 1994 as cited in 

Kunzmann and others 1998).

0

2. Predators Are important 

predator populations 

expected to change?

Few data are available on predation (Kunzmann and others 1998). 

The following observations of predation on elegant trogons were 

reported by Taylor (1994 as cited in Kunzmann and others 1998): 

Cooper’s Hawk attack on breeding adults, Mexican jay attack on 

fledglings, and sulphur-bellied flycatchers attack on nestlings. Adult 

trogons have been observed mobbing great horned owls, and a 

Sonoran gopher snake moving toward a nest. Breeding adults 

attacked Mexican fox squirrels and Arizona gray squirrels in Arizona 

(Taylor 1994 as cited in Kunzmann and others 1998), which may 

suggest these species are predators (as well as nest cavity predators).

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

Elegant trogons are obligate secondary cavity nesters, meaning that 

they do not excavate cavities in trees. We considered this species 

vulnerable to climate change due to the potential for reduced 

availability of nest cavities. This species is large enough that natural 

cavities with large openings must be located or it must use cavities 

created by woodpeckers (which are expected to be vulnerable to 

climate change).

1

4. Disease Is prevalence of 

diseases known to 

cause widespread 

Kunzmann and others (1998) found no data on diseases, although the 

authors cited reports on the species carrying a biting lice parasite 

(Trogonirmus elegans; Malcomson 1960). Unidentified nestling 

0
68 USDA Forest Service RMRS-GTR-273. 2012.

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Biotic interactions: Elegant trogon (Trogon elegans)

Trait/Quality Question Background info. & explanation of score Points

mortality or 

reproductive failure 

in this species 

expected to change? 

parasites were reported by Taylor (1994 as cited in Kunzmamm and 

others 1998).

5. Competitors Are populations of 

important competing 

species expected to 

change?

Intra-specific competition observed in apparent competition for nest 

cavities (Kunzmann and others 1998). Both males and females defend 

nest cavities against other species of primary and secondary cavity 

nesters (e.g., sulphur-bellied flycatcher, northern flicker, eared 

quetzal, screech-owls). Northern flickers typically win control of 

contested trogon cavities, and whiskered screech-owls win about 10% 

of trogon cavities (Taylor 1994 as cited in Kunzmann and others 

1998). Breeding adults attacked Mexican fox squirrels and Arizona 

gray squirrels in Arizona. At least some of these competitor species 

are expected to be vulnerable to climate change.

Note: Contrast with Biotic Interactions, Question 3 above, however, 

where reduction in symbionts results in vulnerability.

Brood parasitism not documented (Kunzmann and others 1998).

-1

Literature Cited

Dawson, A., V.M. King, G.E. Bentley, G.F. Ball. 2001. Photoperiodic control of seasonality in birds. 

Journal of Biological Rhythms 16:365-380.

Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 

436:686-688.

Kunzmann, M.R., L.S. Hall, and R.R. Johnson. 1998. Elegant Trogon (Trogon elegans). In: Poole, A., 

and F. Gill, Eds. The Birds of North America, No. 357. Philadelphia, PA: The Birds of North America, 

Inc.

Magrin, G., C. Gay García, D. Cruz Choque, J.C. Giménez, A.R. Moreno, G.J. Nagy, C. Nobre, and A. 

Villamizar. 2007. Latin America. In: Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and 

C.E. Hanson, Eds. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of 

Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change,

Cambridge, United Kingdom: Cambridge University Press: 581-615.

Martin, T.E. 1987. Food as a limit on breeding birds: a life-history perspective. Annual Review of 

Ecology and Systematics 18:453-487.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.
USDA Forest Service RMRS-GTR-273. 2012. 69 107

Habitat: Northern buff-breasted flycatcher (Empidonax fulvifrons pygmaeus)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change?

Distribution in the United States is southeast Arizona during the 

breeding season. Outside of the United States, occurs in Mexico and 

Central America. Very rare in the United States; only 20-40 

individuals known annually in the 1980s (Bowers and Dunning 1994). 

A range-wide survey in 2000 in Arizona estimated the population at 

74 individuals (Conway and Kirkpatrick 2007). Two possible records 

from 1970s in New Mexico (Witzeman and others 1976 as cited in 

Bowers and Dunning 1994). This is the only sub-species of buffbreasted flycatcher reported to occur in the United States (Bowers and 

Dunning 1994).

Throughout its range, prefers open pine-oak woodlands and montane 

riparian forests (Bowers and Dunning 1994). Occurs in wide 

mountain canyons with open growth of pines and/or oaks usually with 

understory of grasses and small trees. Also uses burned forest with 

clusters of live pines. Often occurs near riparian areas (Bowers and 

Dunning 1994). Elevations of breeding sites in Arizona range 1950-

2850 m (Bent 1942 as cited in Bowers and Dunning 1994). In 

Arizona, usually nests in conifer (Bowers and Dunning 1994).

Bowers and Dunning (1994) reported the range in the United States as 

“higher elevations of Huachuca, Chiricahua, Santa Rita, and Santa 

Catalina Mountains...in past, also known from Rincon, Patagonia, 

and Pajarito Mountains.” During ABBA surveys, found to nest 

commonly only in specific drainages of the Chiricahua and Huachuca 

Mountains; some observations were also made in Santa Rita, Rincon, 

and Santa Catalina Mountains where northern buff-breasted 

flycatchers may breed on occasion (Corman and Wise-Gervais 2005). 

Kirkpatrick and others (2007) observed northern buff-breasted 

flycatchers in the Rincon Mountains in 2000, which was the first 

documented record there since 1911.

Northern buff-breasted flycatchers, or its potential habitat, occur on 

the following 5 EMAs: Peloncillo, Chiricahua, Santa Rita, Huachuca, 

Santa Catalina (USFS 2009). Projections of suitable climate for 

vegetation communities (Chapter 1) predicted declines in suitable 

conditions for Madrean forest and woodland and Madrean conifer 

forest and increases in suitable conditions for semi-desert grassland 

and, to a lesser extent, Sonoran desert scrub.

Bowers and Dunning (1994) reported that fire may open new habitat 

by clearing dense undergrowth that inhibits foraging. They cited a 

case of a fire in 1976 in the Huachuca Mountains (Carr Canyon) that 

cleared several hundred acres but left intact small pockets of live 

trees. Prior to the burn, 1-2 pairs of northern buff-breasted flycatcher 

were known in this area; by 1980, at least 5 adults were recorded and 

9 adults by 1983. Martin and Morrison (1999) indicated that 

prescribed burning may improve habitat suitability by reducing oak 

understory, but also indicated that changes in vegetation from fire 

suppression and grazing may not be completely responsible for the 

rarity of this species in Arizona, as some apparently suitable habitat 

remains unoccupied. Conway and Kirkpatrick (2007) found presence 

of individuals was especially associated with areas containing 

evidence of high-severity surface fire. At the same time, the authors 

noted the absence of detections in 5 canyons that had recently burned.

Fires that are not stand-replacing but that reduce shrubs may increase 

habitat for this species. However, fires in the future are likely to be 

larger and of greater intensity. There was an increase in the area over 

which stand-replacing fires occurred between 1984 and 2006 in 

2
70 USDA Forest Service RMRS-GTR-273. 2012.

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Habitat: Northern buff-breasted flycatcher (Empidonax fulvifrons pygmaeus)

Trait/Quality Question Background info. & explanation of score Points

portions of California and Nevada, as well as an increase in mean and

maximum fire size and the area burned annually (Miller et. al. 2009). 

The authors indicated that the patterns appeared to be related to hotter 

air temperatures and reduced precipitation and were not limited by 

forest fuels.

Overall, we expected that projected reductions in forested habitats 

(e.g., increased aridity, drought, and high intensity fires) will reduce 

breeding habitat.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Little is known about the wintering ecology (Bowers and Dunning 

1994). Reported to occur at elevations lower than breeding habitat in 

winter; some individuals in Sonora move from pine-oak woodland to 

low-elevation canyons in thorn scrub near riparian areas (Bowers and 

Dunning 1994). During migration, has been reported in lowland 

communities, especially sycamore, cottonwood, and willow riparian 

forests (see references in Bowers and Dunning 1994).

Specific projections for change in vegetation in Mexico and Central 

America were not found. Increases in temperature have been 

projected for Central America (Magrin and others 2007: Fig. 13.1, 

Table 13.4). In southern Mexico from 1960-2004, average and 

maximum temperatures increased and were generally unrelated to 

ENSO or PDO (Peralta-Hernandez and others 2009). In this same 

study, a slight non-statistically significant decrease in precipitation 

was observed. Observed trends in rainfall for Central America vary 

from increases in some areas to decreases in other areas (Magrin and 

others 2007: Fig. 13.1)

Given the broad geographic scale over which northern buff-breasted 

flycatchers potentially occurs in winter (Mexico and Central America) 

and the absence of specific vegetation projections for those areas, it is 

difficult to predict how habitat will respond. We assumed that 

projected increases in temperature and possible reductions in 

precipitation would lead to conversion of semi-arid regions to arid and 

that reduced riparian areas would lead to reduced wintering habitat. 

2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

In Arizona, observed nesting in Chihuahuan pine, ponderosa pine, 

Arizona sycamore, Arizona white oak, and Douglas-fir; a few nests 

found in Arizona walnut, big-toothed maple, and alligator juniper 

(Bowers and Dunning 1994). Percent cover of Chihuahuan pine and 

Apache pine >10 m tall was the most important variable 

distinguishing occupied areas from unoccupied areas (Martin and 

Morrison 1999). Trees expected to decline in abundance.

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

No information about possible habitat components on wintering 

range.

0

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

No information in Bowers and Dunning (1994). Martin and Morrison 

(1999) indicate that differences in habitat variables between 

successful and unsuccessful nests were not significant biologically.

0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information in Bowers and Dunning (1994). 0
USDA Forest Service RMRS-GTR-273. 2012. 71

109

Habitat: Northern buff-breasted flycatcher (Empidonax fulvifrons pygmaeus)

Trait/Quality Question Background info. & explanation of score Points

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Both sexes are highly mobile given that populations in Arizona are 

migratory. We consider birds to be very mobile due to their capacity 

for flight and, thus, overall able to colonize new areas.

-1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Breeds in Arizona but winters in Mexico; little is known about 

wintering ecology (Bowers and Dunning 1994). Arrives in breeding 

areas in Arizona between late March and early April (Bowers and 

Dunning 1994). Individuals that breed in Arizona and northern 

Sonora, Mexico, move south at least as far as central or southern 

Sonora in winter (Bowers and Dunning 1994).

1

Physiology: Northern buff-breasted flycatcher (Empidonax fulvifrons pygmaeus)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

No observations of drinking reported (Bowers and Dunning 1994).

Metabolism and temperature regulation have not been examined 

(Bowers and Dunning 1994).

Arizona is the northern range limit; considered to be more common in 

Mexico (Bowers and Dunning 1994). This may suggest that 

individuals are more tolerant of warm temperatures compared to 

species whose southern range limit is Arizona.

With the exception of cases of extreme heat rises, presumably could 

tolerate increases of a few degrees C. Shaded habitat would allow 

escape of direct effects of solar radiation on rise in body temperature, 

although shade from trees expected to decline with time.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather 

or disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will effect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality.

Hurricane intensity is expected to increase under global climate 

change, but hurricane frequency predictions are inconsistent (Emanuel 

2005); frequency increase likely more detrimental overall to migrating 

populations than intensity since hurricane-level winds already 

detrimental to migrants. See also Physiology, Question 1.

No information in Bowers and Dunning (1994) on significant 

mortality or failed reproduction due to weather, although authors 

indicated little information on causes of mortality.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation regimes 

that influence activity 

period of species 

expected to change?

See Physiology, Question 1. With the exception of cases of extreme 

heat rises, seems unlikely for seasonal or daily active periods to be 

restricted to the point of significantly reduced survival. 

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Little information on temperature regulation or metabolism (Bowers 

and Dunning 1994). No information to suggest that torpor is used (no 

citations in Web of Science database).

1
72 USDA Forest Service RMRS-GTR-273. 2012.

110

Physiology: Northern buff-breasted flycatcher (Empidonax fulvifrons pygmaeus)

Trait/Quality Question Background info. & explanation of score Points

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Not known to store food (Bowers and Dunning 1994). 1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No variable life history strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

No information on lifespan or survivorship; only 25 birds banded 

according to U.S. Bird Banding Laboratory (Bowers and Dunning 

1994). In Arizona, 5 individuals re-sighted after banding, making them 

a minimum of 2 years old; none re-sighted in subsequent years 

(Bowers and Dunning 1994).

Another flycatcher species, the willow flycatcher (Empidonax trailii), 

has an average life span of 1 year (Sedgwick 2000). Longevity record 

(i.e., longest-lived bird recorded) for the western flycatcher (E. 

difficilis) is 6 years based on 30 recoveries from birds banded through 

1981 (Clapp and others 1983 as cited in Lowther 2000).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that birds have 

insufficient food for breeding, most of the population would not 

survive longer than the periods of limited reproduction.

1

Phenology: Northern buff-breasted flycatcher (Empidonax fulvifrons pygmaeus)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Northern buff-breasted flycatchers are predictable breeders, meaning 

the breeding season occurs at the same time each year (i.e., spring). In 

predictable breeders, photoperiod is the predominant proximate factor 

leading to gonadal changes required for reproduction (Dawson and 

others 2001). It should be noted that, in general, birds also use local 

predictive information, such as temperature, availability of food, and 

rainfall, to make short-term adjustments to reproductive timing 

(Wingfield 2008), although this short-term adjustment is not addressed 

by this question (see Bagne and others 2011).

0

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Food abundance in spring is an important factor driving fecundity in 

bird species breeding in temperate regions (review by Martin 1987). 

Typically, increases in insect abundance (a critical resource) occur in 

spring; changes in the timing of precipitation and increases in 

temperature have the potential to alter the timing of insect availability 

and abundance and, hence, fecundity. In Arizona, most females lay 

eggs between early May and early August, but in some years, females 

have laid as early as late April (Corman and Wise-Gervais 2005).

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate activities 

and discrete events 

that provide critical 

resources?

Northern buff-breasted flycatchers are migrants that occur in the CNF 

in the breeding season. Critical resources for breeding occur far from 

where individuals over-winter; thus, individuals have no direct 

information about resource abundance on the breeding grounds when 

they initiate migration from their wintering grounds. 

1
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111

Phenology: Northern buff-breasted flycatcher (Empidonax fulvifrons pygmaeus)

Trait/Quality Question Background info. & explanation of score Points

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Buff-breasted flycatchers typically rears a single brood (although will 

re-nest after nest failure; Bowers and Dunning 1994). Martin and 

Morrison (1999) observed 3 cases of second nesting attempts after pairs 

successfully reared a brood, although unclear if this is typical. 

1

Biotic interactions: Northern buff-breasted flycatcher (Empidonax fulvifrons pygmaeus)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Consumes insects, mostly by sallying from a perch; also flies to ground 

to consume ants and other prey (Bowers and Dunning 1994).Contents 

of stomach of one individual from Arizona contained ants, wasps, true 

bugs (Hemiptera), beetles (Coleoptera), and grasshoppers (Cottam and

Knappen 1939 as cited in Bowers and Dunning 1994). Large prey 

identified in bills of breeding Arizona adults: moth, damselfly, spider, 

cranefly, grasshopper, other insects (Bowers and Dunning 1994). 

Overall, consumes a variety of insect prey.

0

2. Predators Are important 

predator populations 

expected to change?

Martin and Morrison (1999) found likely predation by jays (Steller’s 

jay and/or Mexican jay) at 20 of 36 failed nests; authors indicated that 

100% nest failure (15 nests) in Carr Canyon in 1995 might have been 

related to high numbers of jays from supplemental feeding at two 

nearby campgrounds. A variety of other predators is likely. 

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found to suggest that important symbiotic relationships 

exist.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

No information (Bowers and Dunning 1994). 0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Bowers and Dunning (1994) indicated one report of nest parasitism by 

a brown-headed cowbird followed by the buff-breasted flycatcher 

abandoning the nest (Bowers and Dunning 1984). Bowers and 

Dunning (1994) found no reports of this species feeding nestling or 

fledged cowbirds. Martin and Morrison (1999) found no cowbird eggs 

or nestlings in the 10 nests that they examined, nor did they find 

cowbird fledglings among 21 other broods, despite the two species of 

cowbirds being common in the study areas. Appears that the buffbreasted flycatcher may be an infrequent cowbird host.

0

Literature Cited

Bagne, K.E., M.M. Friggens, and D.M. Finch. 2011. A system for assessing vulnerability of species 

(SAVS) to climate change. Gen. Tech. Rep. RMRS-GTR-257. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station. 28 p.

Bowers, R.K., Jr., and J.B. Dunning, Jr. 1994. Buff-breasted Flycatcher (Empidonax fulvifrons). In: 

Poole, A., ed. The birds of North America online. Ithaca, NY: Cornell Lab of Ornithology. Available: 

http://bna.birds.cornell.edu/bna/species/125.
74 USDA Forest Service RMRS-GTR-273. 2012.

112

Bowers, R.K., Jr., and J.B. Dunning, Jr. 1984. Nest parasitism by cowbirds on buff-breasted flycatchers,

with comments on nest-site selection. Wilson Bulletin 96:718-719.

Conway, C.J., and C. Kirkpatrick. 2007. Effects of forest fire suppression on buff-breasted flycatchers. 

Journal of Wildlife Management 71:445-457.

Corman, T.E., and C. Wise-Gervais, ed. 2005. The Arizona Breeding Bird Atlas. Albuquerque, NM:

University of New Mexico Press.

Dawson, A., V.M. King, G.E. Bentley, G.F. Ball. 2001. Photoperiodic control of seasonality in birds. 

Journal of Biological Rhythms 16:365-380.

Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 

436:686-688.

Kirkpatrick, C., C.J. Conway, and D. LaRoche. 2007. Range expansion of the buff-breasted flycatcher 

(Empidonax fulvifrons) into the Rincon Mountains, Arizona. Southwestern Naturalist 52:149-152.

Lowther, P.E. 2000. Pacific-slope Flycatcher (Empidonax difficilis). In: Poole, A., ed. The birds of 

North America online. Ithaca, NY: Cornell Lab of Ornithology. Available: 

http://bna.birds.cornell.edu/bna/species/556a.

Magrin, G., C. Gay García, D. Cruz Choque, J.C. Giménez, A.R. Moreno, G.J. Nagy, C. Nobre and A. 

Villamizar. 2007. Latin America. In: Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and 

C.E. Hanson, eds. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of 

Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. 

Cambridge, United Kingdom: Cambridge University Press: 581-615.

Martin, T.E. 1987. Food as a limit on breeding birds: A life-history perspective. Annual Review of 

Ecology and Systematics 18:453-487.

Martin, J.A., and M.L. Morrison. 1999. Distribution, abundance, and habitat characteristics of the buffbreasted flycatcher in Arizona. Condor 101:272-281.

Miller, J.D., H.D. Safford, M. Crimmins, and A.E. Thode. 2009. Quantitative evidence for increasing 

forest fire severity in the Sierra Nevada and southern Cascade Mountains, California and Nevada, USA. 

Ecosystems 12:16-32.

Peralta-Hernandez, A., R.C. Balling, Jr., and L.R. Barba-Martinez. 2009. Analysis of near-surface diurnal 

temperature variations and trends in southern Mexico. International Journal of Climatology 29:205-209.

Sedgwick, J.A. 2000. Willow Flycatcher (Empidonax trailii). In: Poole, A., and F. Gill, eds. The birds of 

North America, No. 533. Philadelphia, PA: The Birds of North America, Inc.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Wingfield, J.C. 2008. Comparative endocrinology, environment, and global change. General and 

Comparative Endocrinology 157:207-216.

Habitat: Mexican long-tongued bat (Choeronycteris mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change?

Distribution of this species is from the southern portion of the 

Southwest (southern California, southern Arizona, and southwestern 

New Mexico) through Mexico (northern and central, including Baja) to 

Honduras and Guatemala (Jones and Carter 1976 as cited in Nowak 

1994; Hall 1991 as cited in Arroyo-Cabrales and others 1987).

Roosting and habitat needs of this species are poorly understood; fewer 

than 1500 individuals have been documented (Cryan and Bogan 2003). 

Observed mostly in arid habitats at 600-2400 m in elevation (Nowak 

1994). Hoffmeister (1986) indicated that the species is found “in 

appropriate shelters in the foothills and above, on mountains that have 

trees in southeastern Arizona... from the lower edge of the oak zone 

through the pine-oak woodland to the pine-fir belt.” Cryan and Bogan 

(2003) found this species in New Mexico and Arizona in Madrean

2
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113

Habitat: Mexican long-tongued bat (Choeronycteris mexicana)

Trait/Quality Question Background info. & explanation of score Points

evergreen woodlands and semi-desert grasslands where species of 

Agave were present; occupied sites were within 1 km of streams.

Roosts in caves, mine tunnels, and buildings (Nowak 1994; ArroyoCabrales 1987). Hoffmeister (1986) reported that they are found in 

mine tunnels, caves, rock fissures, and, rarely, in buildings. Females 

and males roost together, although when young are born, the two sexes 

may separate (Hoffmeister 1986).

This species occurs, or potential habitat exists, on 8 of the 12 EMAs on 

CNF: Peloncillo, Chiricahua, Dragoon, Tumacacori, Santa Rita, 

Huachuca, Whetstone, and Santa Catalina (USFS 2009). Projections of 

suitable climate for vegetation communities forest wide (Chapter 1) 

predicted declines in suitable climate for all plant community types, 

with the exception of increases of suitable climate for semi-desert 

grassland and small increases in Sonoran desert scrub (present in small 

amounts on the CNF).

Projected reductions in woodlands and forested habitats are expected to 

reduce breeding habitat for this species.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to change?

Colonies in southern Arizona thought to migrate to Mexico in winter 

based on indirect evidence (Nowak 1994). In Mexico, has been 

collected in a variety of habits, including arid thorn scrub, tropical 

deciduous forest, and mixed oak-conifer forest (see references in 

Arroyo-Cabrales and others 1987).

We assumed that projected reductions in woodlands and forested 

habitats for the Southwest likely hold true for Mexico as well, which 

would mean reduced wintering habitat for this species.

2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change?

Given where this species roosts (Hoffmeister 1986), it does not face the 

loss of roost sites from vegetation mortality that threatens other bat 

species.

Nectarivorous and frugivorous bats (as is this species) obtain much of 

their water from food (Hayes and Loeb 2007), so unclear if this species 

depends on drinking water.

0

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

non-breeding 

periods expected to 

change?

See Habitat Question 3. 0

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

No information found. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information found. 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

We considered bats to be very mobile due to their capacity for flight 

and, thus, overall able to colonize new areas. Furthermore, individuals 

that breed in Arizona are believed to migrate.

-1
76 USDA Forest Service RMRS-GTR-273. 2012.

114

Habitat: Mexican long-tongued bat (Choeronycteris mexicana)

Trait/Quality Question Background info. & explanation of score Points

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Colonies in southern Arizona are thought to migrate to Mexico in 

winter based on indirect evidence (Nowak 1994).

1

Physiology: Mexican long-tongued bat (Choeronycteris mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Nocturnal forager, so not active during hottest part of day.

In a review of the upper critical temperatures for 50 species of bats, the 

maximum was 41.0 °C and mean was 36.26 °C (Speakman and Thomas 

2003); upper critical temperature is the ambient temperature above 

which an animal’s body temperature will increase unless it pants or 

sweats. In the case of three species of bats roosting in a California barn 

in summer (Myotis yumanensis, Antrozous pallidus, and Tadarida 

brasiliensis), when ambient temperature approached 40 °C (104 °F), 

spacing between individuals tended to increase and most individuals 

moved to cooler parts of the loft though some did not (Licht and Leitner 

1967).

Overall, we assumed that temperature would not exceed thresholds. 

Standing water is expected to become less available, but this is covered 

in Habitat section.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will effect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality for this 

species.

Hurricane intensity is expected to increase under global climate change, 

but hurricane frequency predictions are inconsistent (Emanuel 2005); 

frequency increase likely more detrimental overall to migrating 

populations than intensity (since hurricane-level winds are already 

detrimental to migrants).

See also Physiology, Question 1. 

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Nighttime forager, so avoids being active in hottest part of day; increase 

in temperatures not likely to reduce foraging time significantly.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Little information on this species. According to Fleming (1988), no 

plant-visiting bat is known to hibernate. Another phyllostomid bat 

(Carollia perspicillata) studied in Costa Rica was observed to exhibit 

daily depression of body temperature (Audet and Thomas 1997); the 

authors concluded that “hypothermia is a thermoregulatory strategy that 

allows phyllostomid bats to adjust metabolic rate to feeding success and 

the level of fat stores”. There is some thought that frugivorous bats 

-1
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115

Physiology: Mexican long-tongued bat (Choeronycteris mexicana)

Trait/Quality Question Background info. & explanation of score Points

would not normally use torpor due to the relatively constant food 

supply in the tropics (McNab 1969 as cited in Audet and Thomas 

1997), but depressed body temperature has been observed in some 

species (Studier and Wilson 1970 as cited in Audet and Thomas 1997).

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

See Physiology, Question 5. We assumed that this species can utilize 

torpor (daily).

1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No alternative strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Bats have been recognized as having an unusual life history; although 

they are small, they are considered to live long lives (Barclay and 

Harder 2003). Mean lifespan for species of Family Phyllostomatidae (to 

which this species belongs) was calculated as 10.9 years (range 7-18), 

but little information indicating what species were included in this 

calculation (Barclay and Harder 2003). Litter size is one (Barbour and 

Davis 1969 as cited in Nowak 1994).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce resources to the point that bats have insufficient 

resources for breeding, but conditions recover after the 5 years, we 

considered it likely that sufficient numbers of individuals would survive 

long enough to breed once conditions improve.

-1

Phenology: Mexican long-tongued bat (Choeronycteris mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Females are said to become pregnant in Mexico in early spring, and 

individuals who migrate give birth in June or July (Adams 2003).

Temperature and moisture influence flowering, which is important to 

this species due to its use of nectar and fruit; but since the relationship 

to parturition would be indirect, this question was scored as “0.”

0

2. Event timing Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

Pregnant females have been collected in the Southwest and Mexico in 

February, March, June, and September (Wilson 1979 as cited in 

Nowak 1994).

Temperature and moisture influence flowering, which is important to 

this species due to its use of nectar and fruit. Other species of 

migratory glossophagine bats (e.g., Leptonycteris) are said to require a 

“nectar trail” (a continual supply of blooming plants), and local 

changes in environmental factors that affect flowering process could 

disrupt this process (Arita and Santos-del-Prado 1999).

1

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

Individuals giving birth in southern Arizona are thought to migrate to 

Mexico in winter based on indirect evidence (Nowak 1994). Food 

resources in Arizona where parturition occurs are thus located at a 

distant location from where the species initiates migration.

1
78 USDA Forest Service RMRS-GTR-273. 2012.

116

Phenology: Mexican long-tongued bat (Choeronycteris mexicana)

Trait/Quality Question Background info. & explanation of score Points

discrete events that 

provide critical 

resources?

4. Resilience to 

timing 

mismatches 

during breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

It appears that this species typically rears only one young per season in 

a single breeding cycle. Watkins and others (1971 as cited in ArroyoCabrales and others 1987) indicated the possibility of a second period 

of birth (based on a pregnant female being observed in Jalisco in 

September, but no other information in Arroyo-Cabrales and others 

(1987) to support this being a common occurrence. Hoffmeister (1986) 

indicated that young are born in the second half of June or early July. 

Females are said to become pregnant in Mexico in early spring (Adams 

2003).

1

Biotic interactions: Mexican long-tongued bat (Choeronycteris mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Some authors have regarded this species as an obligate pollen feeder 

(Alvarez and Gonzalez 1970 as cited in Arroyo-Cabrales and others 

1987), but other evidence suggests this is not the case. Consumes 

fruit, pollen, nectar, and probably insects; thought to pollinate some 

plants (Gardner 1977a as cited in Arroyo-Cabrales and others 1987). 

Hoffmeister (1986) indicated that the food habits of this species are 

not well known and speculated that individuals may feed primarily on 

nectar and pollen in Arizona—primarily from Agave and Fouquieria 

spp. and other succulents. In central Mexico, forages on cactus 

(Stenocereus stellatus; Arias-Coyotl and others 2006).

Less precipitation and increases in higher temperatures (and/or heat 

waves) may shorten the length of flowering season, which could 

negatively affect this species due to its apparent strong dependence on 

what appears to be relatively few species of plants.

1

2. Predators Are important 

predator populations 

expected to change?

Little information. Known to be preyed upon by owls (Mones 1968 as 

cited in Arroyo-Cabrales and others 1987). 

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

Mutualistic relationships likely exist between this species and its food 

plants, but little is known about its role as a pollinator or seed 

disperser (Cryan and Bogan 2003). This species is reported to be one 

of three bats species that pollinates agaves (although other pollinators 

may exist; Arizaga and others 2000).

The role of the food resources for this species is covered in Biotic 

Interactions, Question 1.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

A host to mites (Webb and Loomis 1977 as cited in Arroyo-Cabrales 

and others 1987) and ticks (Mumford and Zimmerman 1962 as cited 

in Arroyo-Cabrales and others 1987). No information indicating 

significant mortality from disease.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Some species of bats roost with other species but this species 

generally does not (Goodwin 1946 as cited in Arroyo-Cabrales and 

others 1987). Little information available regarding competitors of 

this species or of competitive interactions affecting bats in general. 

An aggressive interaction was observed with a Leptonycteris species 

while foraging on cactus (Stenocereus stellatus; Arias-Coyotl and 

others 2006).

0
USDA Forest Service RMRS-GTR-273. 2012. 79

117

Literature Cited

Adams, R.A. 2003. Bats of the Rocky Mountain West. Boulder, CO: University of Colorado Press. 289 p.

Arita, H.T., and K. Santos-del-Prado. 1999. Conservation biology of nectar-feeding bats in Mexico. 

Journal of Mammalogy 80:31-41.

Arias-Coyotl, E., K.E. Stoner, and A. Casas. 2006. Effectiveness of bats as pollinators of Stenocereus 

stellatus (Cactaceae) in wild, managed in situ, and cultivated populations in La Mixteca Baja, central 

Mexico. American Journal of Botany 93:1675-1683.

Arizaga, S., E. Excurra, E. Peters, F. Ramirez de Arrellano, and E. Vega. 2000. Pollination ecology of 

Agave macroacantha (Agavaceae) in a Mexican tropical desert. II. The role of pollinators. American 

Journal of Botany 87:1011-1017.

Arroyo-Cabrales, J., R.R. Hollander, and J.K. Jones, Jr. 1987. Choeronycteris mexicana. Mammalian 

Species 291:1-5. American Society of Mammalogists.

Audet, D., and D.W. Thomas. 1997. Facultative hypothermia as a thermoregulatory strategy in the 

phyllostomid bats, Carollia perspicillata and Sturnira lilium. Journal of Comparative Physiology B 

167:146-152.

Barclay, M.R., and L.D. Harder. 2003. Life histories of bats: Life in the slow lane. In: Kunz, T.H., and 

M.B. Fenton, eds. Bat Ecology. Chicago: University of Chicago Press: 209-253.

Cryan, P.M., and M.A. Bogan. 2003. Recurrence of Mexican long-tongued bats (Choeronycteris 

mexicana) at historical sites in Arizona and New Mexico. Western North American Naturalist 

63:314-319.

Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 

436:686-688.

Fleming, T.H. 1988. The Short-tailed Fruit Bat: A Study in Plant-Animal Interactions. Chicago: The 

University of Chicago Press.

Hayes, J.P., and S.C. Loeb. 2007. The influences of forest management on bats in North America. In:

Lacki, M.J., J.P. Hayes, and A. Kurta., eds. Bats in Forests: Conservation and Management. Baltimore, 

MD: Johns Hopkins University Press: 207-235.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press, and Arizona Game and Fish 

Department. 602 p.

Licht, P., and P. Leitner. 1967. Behavioral responses to high temperatures in three species of California 

bats. Journal of Mammalogy 48:52-61.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Nowak, R.M. 1994. Walker’s Bats of the World. Baltimore, MD: The John Hopkins University Press. 

287 p.

Speakman, J.R., and D.W. Thomas. 2003. Physiol

ogical ecology and energetic of bats. In: Kunz, T.H., and M.B. Fenton, eds. Bat Ecology. Chicago: 

University of Chicago Press: 430-490.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture. Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.
80 USDA Forest Service RMRS-GTR-273. 2012. 118

Habitat: Western yellow bat (Lasiurus xanthinus)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change?

Taxonomic note: The genus Lasiurus comprises the hairy-tailed bats. 

Until changes began to be considered in the late 1980s, L. xanthinus

was considered a sub-species of Lasiurus ega (specifically, L. ega 

xanthinus), the southern yellow bat. Baker and others (1988) 

recommended consideration of L. xanthinus as a distinct species from 

L. ega. Jones and others (1992) recognized two distinct species—the 

southern yellow bat (L. ega) and the western yellow bat (L. xanthinus). 

Morales and Bickham (1995) also supported recognition of L. 

xanthinus. Some of the information cited here is for L. ega since little 

published information exists for L. xanthinus (three references in Web 

of Science database).

Nowak (1994) reported L. xanthinus occurring in the southwestern 

United States, central and western Mexico, and Baja California. In 

contrast, L. ega was indicated as occurring in southern Texas, eastern 

Mexico to northeastern Argentina (Nowak 1994). In Arizona, 

Hoffmeister (1986) reported the range as southern Arizona, as far 

north as Phoenix. L. xanthinus has been reported in Nevada, where 

several hundred captures were made over 2 years; both sexes were 

captured in all seasons (O’Farrell and others 2004). Recorded in 

western Texas (Higginbotham and others 2000). NatureServe (2010) 

indicated that L. xanthinus occurs in southern California, southern 

Arizona, extreme southwestern New Mexico, and Mexico, and is a 

year-round resident.

Species of Lasiurus generally occur in wooded areas and roost in 

foliage and occasionally in tree holes or buildings (Nowak 1994). L. 

ega is reported to live in a variety of habitats (Kurta and Lehr 1995). 

Use of “palm skirts” in palm trees for roosting in the Southwest 

appears to be related to recent range extensions of L. xanthinus 

(Constantine 1998). One adult bat in Texas observed to roost in a giant 

dagger (Yucca carnerosana; Higginbotham and others 2000). In 

southern Nevada (northern-most documented records for the species), 

occupied extensive California fan palm groves for roosting and 

foraging and spend more time in riparian woodland than in other 

vegetation types (O’Farrell and others 2004). Little information on 

other species of trees used for roosting by this species. Also reported to 

roost in hackberry and sycamore (Adams 2003).

Lasiurus xanthinus is reported to occur on all 12 of the EMAs on CNF. 

Projections of suitable climate for vegetation communities forest wide 

(Chapter 1) predicted declines in suitable climate for all plant 

community types, with the exception of increases of suitable climate 

for semi-desert grassland and small increases in Sonoran desert scrub 

(present in small amounts on the CNF).

Habitat for this species is expected to decline due to increased aridity 

and increased wildfires (even if limited to naturally occurring palm 

trees).

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to 

change?

Little information on wintering in this species (as is true for many 

foliage-roosting bats). Hoffmeister (1986) indicated this species 

“probably present year-round” in Arizona; live specimens have been 

collected in southern Arizona in January, February, April, May, 

September, and October.

Score for this question reflects consideration of potential changes to 

non-breeding habitat in Arizona with the assumption that the same 

types of areas are used in winter as in summer.

2
USDA Forest Service RMRS-GTR-273. 2012. 81

119

Habitat: Western yellow bat (Lasiurus xanthinus)

Trait/Quality Question Background info. & explanation of score Points

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change?

L. xanthinus is one of many species of bats referred to as “tree bats” as 

it is believed to rely on trees for roosting throughout the year (Cryan 

and Veilleux 2007). Lasiurine bats typically do not roost in caves 

(Kurta and Lehr 1995). In general, lasiurines roost alone or in small 

family groups (Cryan and Veilleux 2007).

Standing water is assumed to be important to this species. In arid 

environments, water can be a resource that limits the presence of bats 

(Hayes and Loeb 2007). Insectivorous bats must obtain much of their 

water intake from free-standing water unlike frugivorous and 

nectarivorous bats, which obtain much of their water from food 

(Neuweiler 2000 as cited in Hayes and Loeb 2007). Water availability 

is expected to be important to successful reproduction since bats lose a 

large of water to evaporation across their wing membranes (Adams 

2003) and because they lactate. Lactating female fringed myotis were 

found to make significantly more drinking passes over a water source 

than non-lactating females (Adams and Hayes 2008). 

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

non-breeding 

periods expected to 

change?

See Habitat, Question 3. 1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

No information found. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to 

change?

No information found. 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

We considered bats to be very mobile due to their capacity for flight 

and, thus, overall able to colonize new areas. Bats are capable of 

moving to more favorable areas (more than 100 km) when seasonal 

conditions are harsh (Cryan 2003).

-1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

See Habitat, Question 2. O’Farrell et. al. (2004) considered it likely 

that part of the population in southern Nevada migrates southward in 

winter. Cryan (2003) concluded that movements in several species of 

tree bats, including this one, appear to be restricted to movements 

within the North American continent.

Overall, in scoring this question, we assumed that individuals breeding 

in Arizona do not make long-distance migrations southward. 

0
82 USDA Forest Service RMRS-GTR-273. 2012.

120

Physiology: Western yellow bat (Lasiurus xanthinus)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Little information available for L. xanthinus. Nocturnal forager, so not 

active during hottest part of day.

In a review of the upper critical temperatures for 50 species of bats, the 

maximum was 41.0 °C and mean was 36.26 °C (Speakman and 

Thomas 2003); upper critical temperature is the ambient temperature 

above which an animal’s body temperature will increase unless it pants 

or sweats. In the case of three species of bats roosting in a California 

barn in summer (Myotis yumanensis, Antrozous pallidus, and Tadarida 

brasiliensis), when ambient temperature approached 40 °C (104 °F), 

spacing between individuals tended to increase and most individuals 

moved to cooler parts of the loft though some did not (Licht and 

Leitner 1967).

The following applies to red bats: One study found that red bats 

(Lasiurus spp.) in Arizona and New Mexico became active when

temperatures reached about 20 °C (Jones 1965 as cited in Shump and 

Shump 1982); other studies have recorded them flying at temperatures 

of 13 °C and 19 °C (see references in Shump and Shump 1982). 

Shump and Shump (1982) indicated that the species seems capable of 

tolerating drastic temperature fluctuations and observed adaptations to 

low temperatures, including more insulation than two genera of caveroosting bats (Myotis and Eptesicus).

Overall, temperature not expected to exceed thresholds.

Standing water is expected to become less available, but this is 

covered in Habitat section.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern United 

States. Overall, not clear to what extent timing and intensity of heat 

waves will effect survival and reproduction. We considered it unlikely 

that heat waves would cause widespread mortality for this species.

See also Physiology, Question 1.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Active in early evening and at night for foraging, so increase in 

temperatures not likely to reduce foraging time significantly. Warmer 

winter temperatures may reduce time spent undertaking torpor, but not 

clear that this will significantly increase active periods.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

According to Cryan and Veilleux (2007), tree bats use torpor to limit 

energy expenditure during unfavorable conditions, and they cite 4 

species of tree bats in which torpor has been documented (silver-haired 

bat [Lasionycteris noctivagans], eastern red bat [L. borealis], hoary bat 

[L. cinereus], and evening bat [Nycticeius humeralis]). The authors 

observed no demonstration that torpor can be used for long periods (e.g., 

>1 week) and indicated that tree bats may use hibernation (a form of 

torpor in which daily arousal process is inhibited) in some situations but 

such behavior has not yet been discovered. Cryan and Veilleux (2007) 

also state that there is “little doubt that lasiurines are capable of 

withstanding subfreezing temperatures for short periods (<1 month).

O’Farrell and others (2004) speculated that reduced period of activity by 

this species in winter in southern Nevada suggested period of torpor. 

-1
USDA Forest Service RMRS-GTR-273. 2012. 83

121

Physiology: Western yellow bat (Lasiurus xanthinus)

Trait/Quality Question Background info. & explanation of score Points

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

See Physiology, Question 5. 1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No alternative strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Little species-level information. Bats have been recognized as having 

an unusual life history; although they are small, they are considered to 

live long lives (Barclay and Harder 2003). Mean lifespan for species of 

Family Vespertilionidae (to which Lasiurus xanthinus belongs) was 

calculated as 14.9 years (range 5-34), but little information indicating 

what species were included in this calculation (Barclay and Harder 

2003).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce resources to the point that bats have insufficient 

resources for breeding, but conditions recover after the 5 years, we 

assumed it is likely that sufficient numbers of individuals would 

survive long enough to breed once conditions improve.

-1

Phenology: Western yellow bat (Lasiurus xanthinus)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

In temperate regions, Lasiurus spp. mating takes place in late summer 

or fall (Nowak 1994); sperm is stored over winter, ovulation and 

fertilization occurring in the spring, and young are born from late May 

to July. Bats in the temperate zones give birth in spring, which 

coincides with insect prey abundance (Arlettaz and others 2001; Frick 

and others 2010). Since Lasiurus spp. are not thought to undergo 

hibernation (although they appear to use shorter periods of torpor), not 

clear whether temperature is used as a significant cue for parturition.

Temperature and moisture influence insect abundance, but since the 

relationship to the timing of parturition would be indirect, this question 

was scored as “0.”

0

2. Event timing Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

Changes in the timing of precipitation and increases in temperature 

can alter the timing of insect availability and abundance. Warmer 

temperatures in spring may lead to earlier insect prey availability and 

possibly earlier parturition (see also Phenology, Question 3).

1

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

Based on the assumption that females giving birth in Arizona spend 

the winter there as well, individuals would have local indication of 

critical resources (e.g., insect prey abundance).

-1
84 USDA Forest Service RMRS-GTR-273. 2012.

122

Phenology: Western yellow bat (Lasiurus xanthinus)

Trait/Quality Question Background info. & explanation of score Points

4. Resilience to 

timing 

mismatches 

during breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Temperate-breeding bats tend to have only one litter per year (Barclay 

and Harder 2003). This characteristic increases its vulnerability to a 

mismatch between resource availability and the breeding period.

1

Biotic interactions: Western yellow bat (Lasiurus xanthinus)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Lasiurine bats begin flying in early evening and capture insects in 

flight ~6-15 m above the ground (one species will land on vegetation) 

(Nowak (1994). Fecal analysis of individuals of L. xanthinus caught 

in Nevada indicated consumption of the following insect orders: 

Coleoptera, Diptera, Hemiptera, Homoptera, Lepidoptera, and 

Orthoptera (O’Farrell and others 2004). Thus, this species appears to 

consume a variety of prey.

0

2. Predators Are important 

predator 

populations 

expected to 

change?

Barn owls are documented predators of L. ega (references in Kurta 

and Lehr 1995). Birds document as predators of other Lasiurus

species. For example, apparent predation on a western red bat by a 

scrub jay in northern California orchard (Constantine 1959); 

observation of a blue jay in Iowa removing a young red bat (L. 

borealis) from breast of its mother and pecking the young bat 

(presumably predation; Elwell 1962). 

0

3. Symbionts Are populations of 

symbiotic species 

expected to 

change?

No information found to suggest existence of important symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to 

change? 

L. ega is susceptible to rabies; infection rate is probably less than 1% 

in wild populations (Constantine and others 1979 as cited in Kurta 

and Lehr 1995). Other parasites observed, including an intestinal 

trematode and a cestode (Kurta and Lehr 1995). Others probably

exist. However, we found no information indicating significant levels 

of mortality from disease.

0

5. Competitors Are populations of 

important 

competing species 

expected to 

change?

Little information available regarding competitors of this species or of 

competitive interactions affecting bats in general. Potential 

competitors are most likely other bat species and/or birds that forage 

aerially at dusk and dawn (e.g., poorwills, nighthawks; Adams 2003); 

competition would be for insect prey and/or access to water sources 

for drinking. Adams (2003) cited work by researchers in Colorado 

that bat species typically differed in the time of night they visited 

small water holes. Competition for roosting sites in this species may 

be mostly intra-specific.

0
USDA Forest Service RMRS-GTR-273. 2012. 85

123

Literature Cited

Adams, R.A. 2003. Bats of the Rocky Mountain West. Boulder, Colorado: University of Colorado Press. 

289 p.

Adams, R.A., and M.A. Hayes. 2008. Water availability and successful lactation by bats as related to 

climate change in arid regions of western North America. Journal of Animal Ecology 77:1115:1121.

Arlettaz, R., P. Christe, A. Lugon, N. Perrin, and P. Vogel. 2001. Food availability dictates the timing of 

parturition in insectivorous mouse-eared bats. Oikos 95:105-111.

Barclay, M.R., and L.D. Harder. 2003. Life histories of bats: Life in the slow lane. In: Kunz, T.H., and 

M.B. Fenton, eds. Bat Ecology. Chicago: University of Chicago Press: 209-253.

Baker, R.J., J.C Patton, H.H. Genoways, and J.W. Bickham. 1988. Genetic studies of Lasiurus

(Chiroptera:Vespertilionidae). Occasional Papers of the Museum of Texas Tech University, Number 

117.

Constantine, D.G. 1959. Ecological observations on lasiurine bats in the North Bay area of California. 

Journal of Mammalogy 40:13-15.

Constantine, D.G. 1998. Range extensions of ten species of bats in California. Bulletin of the Southern 

California Academy of Sciences 97:49-75.

Cryan, P.M. 2003. Seasonal distribution of migratory tree bats (Lasiurus and Lasionycteris) in North 

America. Journal of Mammalogy 84:579-593.

Cryan, P.M., and J.P. Veilleux. 2007. Migration and use of autumn, winter, and spring roosts by tree bats. 

In: Lacki, M.J., J.P. Hayes, and A. Kurta., eds. Bats in Forests: Conservation and Management. 

Baltimore, MD: Johns Hopkins University Press: 153-175.

Elwell, A.S. 1962. Blue Jay preys on young bats. Journal of Mammalogy 43:434.

Frick, W.F., D.S. Reynolds, and T.H. Kunz. 2010. Influence of climate and reproductive timing on 

demography of little brown myotis Myotis lucifigans. Journal of Animal Ecology 79:128-136.

Hayes, J.P., and S.C. Loeb. 2007. The influences of forest management on bats in North America. In:

Lacki, M.J., J.P. Hayes, and A. Kurta., eds. Bats in Forests: Conservation and Management. Baltimore, 

MD: Johns Hopkins University Press: 207-235.

Higgenbotham, J.L., M.T. Dixon, and L.K. Ammerman. 2000. Yucca provides roost for Lasiurus 

xanthinus (Chiroptera: Vespertilionidae) in Texas. Southwestern Naturalist 45:338-340.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press, and Arizona Game and Fish 

Department. 602 p.

Jones, J.K., Jr., R.S. Hoffmann, D.W. Rice, C. Jones, R.J. Baker, and M.D. Engstrom. 1992. Revised 

checklist of North American mammals north of Mexico, 1991. Occasional Papers of the Museum of 

Texas Tech University, Number 146.

Kurta, A., and G.C. Lehr. 1995. Lasiurus ega. American Society of Mammalogists. Mammalian Species 

No. 515:1-7.

Licht, P., and P. Leitner. 1967. Behavioral responses to high temperatures in three species of California 

bats. Journal of Mammalogy 48:52-61.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Morales, J.C., and J.W. Bickham. 1995. Molecular systematic of the genus Lasiurus (Chiroptera: 

Vespertilionidae) based on restriction-site maps of the mitochondrial ribosomal genes. Journal of 

Mammalogy 76:730-749.

NatureServe. 2010. Comprehensive report for Lasiurus xanthinus (Western Yellow Bat). Available: 

http://www.natureserve.org/explorer/. Accessed March 26, 2010.

Nowak, R.M. 1994. Walker’s Bats of the World. Baltimore, MD: The John Hopkins University Press.

O’Farrell, M.J., J.A. Williams, and B. Lund. 2004. Western yellow bat (Lasiurus xanthinus) in southern 

Nevada. Southwestern Naturalist 49:514-518.

Shump, K.A., and A.U. Shump. 1982. Lasiurus borealis. American Society of Mammalogists. 

Mammalian Species No. 183:1-6.
86 USDA Forest Service RMRS-GTR-273. 2012.

124

Speakman, J.R., and D.W. Thomas. 2003. Physiological ecology and energetic of bats. In: Kunz, T.H., 

and M.B. Fenton, eds. Bat Ecology. Chicago: University of Chicago Press.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Habitat: Western red bat (Lasiurus blossevillii)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change?

Taxonomic note: This species was formerly considered under two 

sub-species of Lasiusus borealis (L. borealis teliotus and L. borealis 

frantzii) but Baker and others (1988) divided Lasiusus borealis into 

several species; Adams (2003) also considered the two to be separate. 

Fossil evidence suggests that L. blossevillii may have been distinct 

from L. borealis since 3.5 million years before present; Czaplewski 

1993).

In the United States, occurs in the southwest and west (California, 

Nevada, Utah, Arizona, and parts of New Mexico, with some rare 

documentation in western Texas). Range extends to Mexico, Central 

America, and South America; some records from southern British 

Columbia (Carter and Menzel 2007; NatureServe 2010).

Lasiurine bats generally occur in wooded areas and roost in foliage; 

occasionally in tree holes or buildings (Nowak 1994). They begin 

flying in early evening and capture insects in flight ~6-15 m above the 

ground (one species will land on vegetation). L. borealis occurs in 

deciduous and coniferous forest (Shump and Shump 1982). Solitary 

and roost mostly in trees or shrubs, sometimes near or on the ground 

(Hall and Kelson 1959 as cited in Shump and Shump 1982). Some 

individuals of one lasiurine (L. borealis borealis ) in Iowa observed to 

change roost sites on different days in summer (Constantine 1966).

Red bats commonly roost in habitats adjacent to streams and open 

fields and in urban areas (references in Shump and Shump 1982). 

Roosts of L. borealis typically have dense shade and cover; no 

indication to what degree this might be for protection from predators 

versus exposure to high temperatures.

In Arizona, L. borealis has been captured over ponds and in riparian 

areas with cottonwoods, sycamores, and walnut trees in the Huachuca 

and Graham Mountains (Hoffmeister 1986). Absent from most desert 

areas (Hoffmeister 1986). Findley and others (1975) noted L. borealis

teliotus in New Mexico is associated with riparian habitats with 

deciduous trees and encinal and riparian sycamores and cottonwoods 

in Hidalgo County. In northern California, reported to roost in fruit 

trees, including fig, apricot, and orange; apricot trees found to contain 

this species tended to be 15-20 ft tall and have dark, dense foliage 

(Constantine 1959).

This species occurs, or potential habitat exists, on 9 of the 12 EMAs on 

CNF (the three exceptions are Winchester, Santa Teresa, and Santa 

Catalina EMAs; USFS 2009). Projections of suitable climate for 

vegetation communities forest wide (Chapter 1) predicted declines in 

suitable climate for all plant community types, with the exception of 

increases of suitable climate for semi-desert grassland and small 

increases in Sonoran desert scrub (present in small amounts on the 

CNF).

Projected reductions in riparian habitats would reduce breeding habitat 

for this species.

2
USDA Forest Service RMRS-GTR-273. 2012. 87

125

Habitat: Western red bat (Lasiurus blossevillii)

Trait/Quality Question Background info. & explanation of score Points

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to change?

Little known about migration and winter locations. Seasonal 

movements may occur in California (Grinnell 1918 as cited in Cryan 

2003). Based on a review of museum records, Cryan (2003) indicated 

that seasonal dispersal of L. blossevillii from California is apparently 

limited. Hoffmeister (1986) stated that L. borealis may be present in 

winter in Arizona.

In California, both males and females occur together at low elevations 

during winter (Grinnell 1918 and Orr 1950 as cited in Cryan 2003). 

The patterns of records in Arizona and New Mexico suggest that at 

least some individuals are moving into the area in spring from 

elsewhere (Cryan 2003).

Findley and others (1975) reported that individuals that breed in New 

Mexico probably move south in winter. Shump and Shump (1982) 

indicated that wintering sites for red bats (L. borealis) are not well 

documented but are “probably in southern states” given that their 

numbers there increase between December and March. (Note that this 

citation was written prior to the acceptance of L. blossevillii as a 

separate species, which complicates the understanding of wintering 

sites.) Considered likely that red bats hibernate in trees in winter 

(Shump and Shump 1982).

Cryan (2003) concluded, based on patterns in museum records, that 

there was little evidence for “major movement” between North 

America and South America by any of the Lasiurus species examined 

(L. borealis, L. blossevillii, L. cinereus, and L. noctivagans).

Migration of more than a few hundred kilometers is rare in bats 

(Fleming and Eby 2003) but is important in those bat species that live 

in highly seasonal environments. L. borealis has been reported to have 

migrated more than 1000 km between summer and winter roosts 

(Fleming and Eby 2003), but not clear whether this applies to L. 

blossevillii.

Score for this question reflects consideration of potential changes to 

non-breeding habitat with the assumption that riparian areas are also 

important in winter and that this species is likely to decline in Mexico 

if that is where some breeding individuals over-winter.

2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change?

L. blossevillii is one of many species of bats referred to as “tree bats.” 

Tree bats are believed to rely on trees for roosting throughout the year 

(Cryan and Veilleux 2007). The western red bat primarily roosts in 

foliage (Hayes 2003). Lasiurine bats typically do not roost in caves 

(Kurta and Lehr 1995). In general, lasiurines roost alone or in small 

family groups (Cryan and Veilleux 2007).

Standing water is considered an important feature for insectivorous 

bats in the Southwest (Hayes and Loeb 2007). Jones (2009) found 

stock tanks and wildlife waterers to be important to bats on the CNF.

Some physiological studies of insectivorous bats during pregnancy and 

lactation have found that individuals consume water from drinking in 

addition to that in their insect prey (free-ranging big brown bats

[Eptesicus fuscus], Kurta and others 1990; and little brown bats

[Myotis lucifugus], Kurta and others 1989). Female fringed myotis 

(Myotis thysanodes) who were lactating visited an artificial water 

source in Colorado 13 times more often than non-lactating females 

(Adams and Hayes 2008).

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

See Habitat, Question 3. 1
88 USDA Forest Service RMRS-GTR-273. 2012.

126

Habitat: Western red bat (Lasiurus blossevillii)

Trait/Quality Question Background info. & explanation of score Points

non-breeding 

periods expected to 

change?

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

No information found. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information found. 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

We considered bats to be very mobile due to their capacity for flight 

and, thus, overall able to colonize new areas. Bats are capable of 

moving more than 100 km to more favorable areas when seasonal 

conditions are harsh (Cryan 2003).

-1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Unclear whether Arizona populations of L. blossevillii move south. 

See Habitat, Question 2 for discussion. Scored this question to account 

for the possibility that this species migrates south for winter.

Additional information: Male and female L. borealis seem to migrate 

at different times and have different summer ranges (references in 

Shump and Shump 1982); in California, males and females winter 

together, but it is considered possible that they used different areas in 

summer (Williams and Findley 1979 as cited in Shump and Shump 

1982).

1

Physiology: Western red bat (Lasiurus blossevillii)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

In a review of the upper critical temperatures for 50 species of bats, the 

maximum was 41.0 °C and mean was 36.26 °C (Speakman and 

Thomas 2003); upper critical temperature is the ambient temperature 

above which an animal’s body temperature will increase unless it pants 

or sweats. In the case of three species of bats roosting in a California 

barn in summer (Myotis yumanensis, Antrozous pallidus, and Tadarida 

brasiliensis), when ambient temperature approached 40 °C (104 °F), 

spacing between individuals tended to increase and most individuals 

moved to cooler parts of the loft though some did not (Licht and 

Leitner 1967).

One study found that red bats in Arizona and New Mexico became 

active when temperatures reached about 20 °C (Jones 1965 as cited in 

Shump and Shump 1982); other studies have found them flying at 

temperatures of 13 °C and 19 °C (see references in Shump and Shump 

1982). Shump and Shump (1982) indicated that the species seems 

capable of tolerating drastic temperature fluctuations and observed 

adaptations to low temperatures, including more insulation than two 

genera of cave-roosting bats (Myotis and Eptesicus). Nocturnal forager 

(begins foraging 1-2 hours after sunset; Kunz 1973 as cited in Shump 

and Shump 1982), so not foraging during hottest part of day.

Standing water is expected to become less available, but this is 

covered in Habitat section.

0
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127

Physiology: Western red bat (Lasiurus blossevillii)

Trait/Quality Question Background info. & explanation of score Points

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality for this 

species.

See also Physiology, Question 1.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Active in early evening and at night for foraging, so increase in 

temperatures not likely to reduce foraging time significantly. Warmer 

winter temperatures may reduce time spent undertaking torpor, but not 

clear if this will significantly increase active periods.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Cryan and Veilleux (2007) indicated that tree bats use torpor to limit 

energy expenditure during unfavorable conditions, citing 4 species of 

tree bats in which torpor has been documented (silver-haired bat, 

eastern red bat, hoary bat, and evening bat). The authors found no 

indication that torpor can be used for long periods (e.g., >1 week).

Cryan and Veilleux (2007) indicated that tree bats may use hibernation 

(a form of torpor in which daily arousal process is inhibited) in some 

situations but that such behavior has not yet been discovered. 

-1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

See Physiology, Question 5. 1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No alternative strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Little species-level information. Bats have been recognized as having 

an unusual life history; although they are small, they are considered to 

live long lives (Barclay and Harder 2003). Mean lifespan for species of 

Family Vespertilionidae (to which L. xanthinus belongs) was 

calculated as 14.9 years (range 5-34), but little information indicating 

what species were included in this calculation (Barclay and Harder 

2003).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce resources to the point that bats have insufficient 

resources for breeding, but conditions recover after, we considered it 

likely that sufficient numbers of individuals would survive long 

enough to breed once conditions improve.

-1
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128

Phenology: Western red bat (Lasiurus blossevillii)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

In temperate regions, Lasiurus spp. mating takes place in late summer 

or fall (Nowak 1994); sperm is stored over winter, ovulation and 

fertilization occur in the spring, and young are born from late May to 

July. Bats in the temperate zones give birth in spring, which coincides 

with insect prey abundance (Arlettaz and others 2001; Frick and others 

2010). Since Lasiurus spp. are not thought to undergo hibernation 

(although they appear to use shorter periods of torpor), not clear 

whether temperature is used as a significant cue for parturition.

Temperature and moisture influence insect abundance, but since the 

relationship to the timing of parturition would be indirect, this question 

was scored as “0.”

0

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Changes in the timing of precipitation and increases in temperature 

can alter the timing of insect availability and abundance. Warmer 

temperatures in spring may lead to earlier insect prey availability and 

possibly earlier parturition (see also Phenology, Question 3).

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

Uncertain to what extent individuals of this species that summer in 

Arizona also winter in Arizona (see Habitat, Question 8). We scored 

this question “0” to account for the uncertainty about whether critical 

resources for parturition are occurring nearby or distant from wintering 

areas. Potential for this species to be migratory was accounted for in 

Habitat, Question 8 by us assigning it a “vulnerable” score.

0

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Breeds in late summer; fertilization occurs in spring; gestation is 80-90 

days (references in Shump and Shump 1982). Temperate-breeding bats 

tend to have only one litter per year (Barclay and Harder 2003).

1

Biotic interactions: Western red bat (Lasiurus blossevillii)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Lasiurine bats begin flying in early evening and capture insects in 

flight ~6-15 m above the ground (one species will land on vegetation) 

(Nowak 1994).

Consumes insects. One study in Indiana (Whitaker 1972 as cited in 

Shump and Shump 1982) found that 26% of stomach contents by 

volume were moths. Other studies indicated that Homoptera, 

Coleoptera, Hymenoptera, Diptera, and Lepidoptera have been found 

in stomachs of red bats (see references in Shump and Shump 1982). 

Also reported to feed on ground-dwelling crickets, flies, bugs, beetles, 

cicadas, grain moths, and other insects (references in Shump and 

Shump 1982).

Thus, this species appears to consume a variety of prey species. 

0

2. Predators Are important 

predator populations 

expected to change?

Barn owls are documented predators of Lasiurus ega (references in 

Kurta and Lehr 1995). Apparent predation on a western red bat by a 

scrub jay in northern California orchard (Constantine 1959). 

Observation of a blue jay in Iowa removing a young red bat (L. 

0
USDA Forest Service RMRS-GTR-273. 2012. 91

129

Biotic interactions: Western red bat (Lasiurus blossevillii)

Trait/Quality Question Background info. & explanation of score Points

borealis) from breast of its mother and pecking the young bat 

(presumably predation; Elwell 1962). Mother generally leaves young 

at the roost site while she forages for food (Shump and Shump 1982), 

so this can leave young vulnerable to predation, as is the case in other 

taxa (e.g., birds).

Other predators are opossums, house cats, sharp-shinned hawks, 

American kestrels, merlins, great horned owls, and roadrunners 

(Shump and Shump 1982).

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found to suggest existence of important symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

L. ega is susceptible to rabies; infection rate is probably less than 1% 

in wild populations (Constantine and others 1979 as cited in Kurta 

and Lehr 1995). Other parasites are an intestinal trematode and a 

cestode (Kurta and Lehr 1995). Others probably exist. No information 

indicating significant levels of mortality.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Little information available regarding competitors of this species or of 

competitive interactions affecting bats in general. Potential 

competitors are most likely other bat species and/or birds that forage 

aerially at dusk and dawn (e.g., poorwills and nighthawks; Adams 

2003); competition would be for insect prey and/or access to water 

sources for drinking. Adams (2003) cited work by researchers in 

Colorado who found that bat species typically differed in the time of 

night they visited small water holes. Competition for roosting sites in 

this species may be mostly intra-specific.

0

Literature Cited

Adams, R.A. 2003. Bats of the Rocky Mountain West. Boulder, CO: University of Colorado Press. 289 p.

Adams, R.A., and M.A. Hayes. 2008. Water availability and successful lactation by bats as related to 

climate change in arid regions of western North America. Journal of Animal Ecology 77:1115-1121.

Arlettaz, R., P. Christe, A. Lugon, N. Perrin, and P. Vogel. 2001. Food availability dictates the timing of 

parturition in insectivorous mouse-eared bats. Oikos 95:105-111.

Baker, R.J., J.C Patton, H.H. Genoways, and J.W. Bickham. 1988. Genetic studies of Lasiurus

(Chiroptera:Vespertilionidae). Occasional Papers of the Museum of Texas Tech University, Number 

117.

Barclay, M.R., and L.D. Harder. 2003. Life histories of bats: Life in the slow lane. In: Kunz, T.H., and 

M.B. Fenton, eds. Bat Ecology. Chicago: University of Chicago Press: 209-253.

Carter, T.C., and J.M Menzel. 2007. Behavior and day-roosting ecology of North American foliageroosting bats. In: Lacki, M.J., J.P. Hayes, and A. Kurta., eds. Bats in Forests: Conservation and 

Management. Baltimore, MD: Johns Hopkins University Press: 61-81.

Constantine, D.G. 1966. Ecological observations on lasiurine bats in Iowa. Journal of Mammalogy 

47:34-41.

Constantine, D.G. 1959. Ecological observations on lasiurine bats in the North Bay area of California. 

Journal of Mammalogy 40:13-15.

Cryan, P.M. 2003. Seasonal distribution of migratory tree bats (Lasiurus and Lasionycteris) in North 

America. Journal of Mammalogy 84:579-593.

Cryan, P.M., and J.P. Veilleux. 2007. Migration and use of autumn, winter, and spring roosts by tree bats. 

In: Lacki, M.J., J.P. Hayes, and A. Kurta., eds. Bats in Forests: Conservation and Management. 

Baltimore, MD: Johns Hopkins University Press: 153-175.
92 USDA Forest Service RMRS-GTR-273. 2012.

130

Czaplewski, N.J. 1993. Late tertiary bats (Mammalia, Chiroptera) from the southwestern United States. 

Southwestern Naturalist 38:111-118.

Elwell, A.S. 1962. Blue jay preys on young bats. Journal of Mammalogy 43:434.

Findley, J.S., A.H. Harris, D.E. Wilson, and C. Jones. 1975. Mammals of New Mexico. Albuquerque: 

University of New Mexico Press.

Fleming, T.H., and P. Eby. 2003. Ecology of bat migration. In: Kunz, T.H., and M.B. Fenton, eds. Bat 

Ecology. Chicago: University of Chicago Press. 779 p.

Frick, W.F., D.S. Reynolds, and T.H. Kunz. 2010. Influence of climate and reproductive timing on 

demography of little brown myotis Myotis lucifigans. Journal of Animal Ecology 79:128-136.

Hayes, J.P. 2003. Habitat ecology and conservation of bats in western coniferous forests. In: Zabel, C.J., 

and R.G. Anthony, eds. Mammal Community Dynamics: Management and Conservation in the 

Coniferous Forests of Western North America. Cambridge, United Kingdom: Cambridge University 

Press: 81-119.

Hayes, J.P., and S.C. Loeb. 2007. The influences of forest management on bats in North America. In:

Lacki, M.J., J.P. Hayes, and A. Kurta., eds. Bats in Forests: Conservation and Management. Baltimore, 

MD: Johns Hopkins University Press: 207-235.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Jones, L. 2009. Distribution of bats across the Huachuca ecosystem management area: A preliminary 

assessment for a landscape-level habitat restoration project. 2009 Arizona Bat Conservation Partnership 

Grant Final Report; December 23, 2009; Submitted to Arizona Game and Fish Department, Phoenix, 

and U.S. Department of Agriculture, Forest Service, Coronado National Forest, Tucson, AZ. Forest 

Service Agreement Number 09-CO-11030515-038. Arizona Game and Fish Department Project 

Number FY-09-06.

Kurta, A., G.P. Bell, K.A. Nagy, T.H. Kunz. 1989. Water balance of free-ranging little brown bats 

(Myotis lucifigus) during pregnancy and lactation. Canadian Journal of Zoology 67:2468-2472.

Kurta, A., T.H. Kunz, K.A. Nagy. 1990. Energetics and water flux of free-ranging big brown bats 

(Eptesicus fuscus) during pregnancy and lactation. Journal of Mammalogy 71:59-65.

Kurta, A., and G.C. Lehr. 1995. Lasiurus ega. American Society of Mammalogists. Mammalian Species 

No. 515:1-7.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

NatureServe. 2010. Comprehensive report for Lasiurus blossevillii (Western Red Bat). Available: 

http://www.natureserve.org/explorer/. Accessed: March 26, 2010.

Nowak, R.M. 1994. Walker’s Bats of the World. Baltimore, MD: The Johns Hopkins University Press.

Shump, K.A., and A.U. Shump. 1982. Lasiurus borealis. American Society of Mammalogists. 

Mammalian Species No. 183:1-6.

Speakman, J.R., and D.W. Thomas. 2003. Physiological ecology and energetics of bats. In: Kunz, T.H., 

and M. Brock Fenton, eds. Bat Ecology. Chicago: University of Chicago Press: 430-490.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.
USDA Forest Service RMRS-GTR-273. 2012. 93 131

Habitat: Allen’s lappet-browed bat (Idionycteris phyllotis)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change?

Taxonomic note: This species also known under the common name 

Mexican big-eared bat. Much of the literature refers to this bat as 

Plecotus phyllotis (Czaplewski 1983). It is in the Family 

Vespertilionidae.

Distribution ranges from the southwestern United States (Arizona and 

portions of California, Nevada, Utah, Colorado, and New Mexico) 

into Mexico (Czaplewski 1983). In Arizona, reported to occur from 

the northwest corner of the state to the southeast corner but not 

reported in the southwestern deserts (Hoffmeister 1986).

Most specimens of this species have been collected from altitudes 

between 1100 m and 2500 m, but specimens range as low as 855 m 

and as high as 3225 m (Genoways and Jones 1967 as cited in 

Czaplewski 1983). According to Hoffmeister (1986), this species has 

been collected most often in ponderosa pine, pinyon juniper, and 

Mexican woodland; collection locales include elevations as high as 

white fir and as low as Mohave desert scrub (where Opuntia spp.,

catclaw, yucca, and Joshua trees occur). This species is associated 

with conifers and often with rocky slopes and nearby cliffs (potential 

roosting sites) in the eastern portion of Arizona (Hoffmeister 1986). 

Czaplewski (1983; see references contained therein) indicated that

this species primarily occupies forested mountainous regions from 

pine, fir, and oak forest into riparian woodlands of sycamore, 

cottonwood, willow, and walnut, with occasional trapping in more 

arid habitats. Czaplewski (1983) reported that this species occurs from 

Mojave Desert scrub to fir forest where rocks are near; rocks are 

assumed to be used as roosting sites.

Individuals have often been netted along streams or over ponds 

(Hoffmeister 1986; Rabe and others 1998) where they may be 

foraging for insects, drinking water, or both (Hoffmeister 1986). 

Where this species has been netted in areas below coniferous 

woodland and coniferous forest, Hoffmeister (1986) indicated that 

this may be a result of this species seeking drinking water rather than 

a reflection of preferred habitat.

Females separate from males in summer to form maternity colonies 

(Williams and Findley 1979 as cited in Czaplewski 1983). This 

species has been observed in nursery (maternity) colonies in caves 

and collapsed tunnels in Arizona (Hoffmeister 1986). Locations used 

by individuals for 1-2 years may be abandoned (Hoffmeister 1986). 

Rabe and others (1998) documented reproductive females of this 

species using ponderosa pine snags in northern Arizona (Coconino 

NF) during June and July.

This species was not detected during surveys of the Huachuca EMA 

by Jones (2009). This species occurs, or potential habitat exists, on 3 

of the 12 EMAs on CNF: Chiricahua, Pinaleño, and Galiuro (USFS 

2009). Projections of suitable climate for vegetation communities 

(Chapter 1) were for declines in suitable climate for forest, woodland, 

and Chihuahuan desert scrub and increases in suitable climate for 

semi-desert grassland and small increases in Sonoran desert scrub 

(present in small amounts on the CNF).

Projected reductions in riparian and forested habitats are expected to 

reduce breeding habitat for this species.

2
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132

Habitat: Allen’s lappet-browed bat (Idionycteris phyllotis)

Trait/Quality Question Background info. & explanation of score Points

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Tumlison (1993) indicated that migration in this species is not 

currently known to occur (see also Habitat, Question 8). We assumed

that habitat used in winter is similar, or the same as, that used in 

summer. Little information on winter behavior. Not clear to what 

extent this species uses torpor in winter.

Scored this question on the assumption that the population does not 

spend a large proportion of winter time hibernating in southern 

Arizona and that individuals occurring in Arizona in winter would 

require foraging habitat.

2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change?

This species is reported to roost in mine tunnels and rocks 

(Czaplewski 1983), but observations of tree use by reproductive 

females has also been documented. Rabe and others (1998) 

documented reproductive females of this species using ponderosa pine 

snags in northern Arizona (Coconino NF) during June and July. 

Solvesky and Chambers (2009) indicated that this species forms 

maternity colonies in ponderosa pine snags in Arizona; most were 

observed in large-diameter snags under sloughing bark, with an 

average of 11 bats per roost. Bachelor roosts were in vertical 

sandstone cliff faces in pinyon-juniper woodlands (Solvesky and 

Chambers 2009). Siders and Jolley (2009) found a maternity roost in 

Utah in a cliff face.

Given that this species can use snags during the breeding season, and 

snags are expected to decline, we expected that potential maternity 

roost sites for this species are likely to decline.

Standing water appears to be important to this species. Czaplewski 

(1983) indicated that most specimens were captured over water holes 

when bats came to drink. In arid environments, water can be a 

resource limiting the presence of bats (Hayes and Loeb 2007). 

Insectivorous bats must obtain much of their water intake from freestanding water, unlike frugivorous and nectarivorous bats, which 

obtain much of their water from food (Neuweiler 2000 as cited in 

Hayes and Loeb 2007). Water availability is expected to be important 

to successful reproduction since bats lose a large of water to 

evaporation across their wing membranes (Adams 2003) and because 

they lactate. Lactating female fringed myotis were found to make 

significantly more drinking passes over a water source than nonlactating females (Adams and Hayes 2008).

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

Little information on winter behavior (see also Habitat, Question 2 

and Habitat, Question 8). Based on the assumption that this species 

exhibits some activity in winter, considered likely that it requires 

standing water during winter. Standing water expected to become less 

available.

1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change?

No information found. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information found. 0
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133

Habitat: Allen’s lappet-browed bat (Idionycteris phyllotis)

Trait/Quality Question Background info. & explanation of score Points

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

We considered bats to be very mobile due to their capacity for flight 

and, thus, overall able to colonize new areas. Bats are capable of 

moving more than 100 km to more favorable areas when seasonal 

conditions are harsh (Cryan 2003). During June and July, females of 

this species were captured on average 1.6 km from maternity roosts, 

and males were captured 12 km from roosts (Solvesky and Chambers 

2009), suggesting that these were distances individuals moved in one 

evening.

-1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Captured infrequently in surveys during November-March in New 

Mexico, which suggested that individuals were hibernating there in 

winter and not regularly active (Geluso 2007). Czaplewski (1983) 

reported that “seasonal movements and cold-season whereabouts and 

activities of the species are unknown. All Mexico specimens were 

collected in summer months...except for the type specimen which 

was taken on 24 March.”

Tumlison (1993) indicated that migration in this species is not 

currently known to occur.

1

Physiology: Allen’s lappet-browed bat (Idionycteris phyllotis)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Little information available for this species. Nocturnal forager, so not 

active during hottest part of day.

In a review of the upper critical temperatures for 50 species of bats, the 

maximum was 41.00 °C and mean was 36.26 °C (Speakman and 

Thomas 2003); upper critical temperature is the ambient temperature 

above which an animal’s body temperature will increase unless it pants 

or sweats. In the case of three species of bats roosting in a California 

barn in summer (Myotis yumanensis, Antrozous pallidus, and Tadarida 

brasiliensis), when ambient temperature approached 40 °C (104 °F), 

spacing between individuals tended to increase and most individuals 

moved to cooler parts of the loft though some did not (Licht and Leitner 

1967).

Overall, we assumed that temperature would not exceed thresholds. 

Standing water is expected to become less available, but this is covered 

in Habitat section.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality for this 

species.

See also Physiology, Question 1.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Active in late evening and at night for foraging, so increase in 

temperatures not likely to reduce foraging time significantly. Warmer 

winter temperatures may reduce time spent undertaking torpor 

(assuming this species uses torpor; see Physiology, Question 5), but not 

clear if this would significantly increase active periods.

0
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134

Physiology: Allen’s lappet-browed bat (Idionycteris phyllotis)

Trait/Quality Question Background info. & explanation of score Points

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Little information on this species. Speakman and Thomas (2003) 

indicated that “probably all temperate-zones species....are capable of 

entering regulated torpor on a regular basis.” Not clear whether this 

species is an obligatory hibernator, or whether it would be in this part of 

its range (Arizona).

-1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

See Physiology, Question 5. We assumed that this species can utilize 

torpor.

1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No alternative strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

The longevity record (i.e., longest-lived individuals recorded) for this 

species is a minimum of 3 years and 2 months (Cockrum 1973 as cited 

in Czaplewski 1983). Bats have been recognized as having an unusual 

life history; although they are small, they are considered to live long 

lives (Barclay and Harder 2003). Mean lifespan for species of Family 

Vespertilionidae (to which Idionycteris phyllotis belongs) was 

calculated as 14.9 years (range 5-34), but little information indicating 

what species included in this calculation (Barclay and Harder 2003).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce resources to the point that bats have insufficient 

resources for breeding, but conditions recover after, we assumed it is 

likely that sufficient numbers of individuals would survive long enough 

to breed once conditions improve.

-1

Phenology: Allen’s lappet-browed bat (Idionycteris phyllotis)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Little information on this species regarding mating and parturition. 

Pregnant females have been collected in June in New Mexico, Arizona, 

and Durango, Mexico (references in Czaplewski 1983).

Bats in the temperate zones give birth in spring, which coincides with 

insect prey abundance (Arlettaz and others 2001; Frick and others 

2010). Temperature and moisture influence insect abundance, but since 

the relationship to the timing of parturition would be indirect, this 

question was scored as “0.”

0

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Changes in the timing of precipitation and increases in temperature can 

alter the timing of insect availability and abundance. Warmer 

temperatures in spring may lead to earlier insect prey availability and 

possibly earlier parturition (see also Phenology, Question 3).

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

Based on the assumption that females giving birth in Arizona spend the 

winter there as well, individuals would have local indication of critical 

resources (e.g., insect prey abundance).

-1
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135

Phenology: Allen’s lappet-browed bat (Idionycteris phyllotis)

Trait/Quality Question Background info. & explanation of score Points

activities and 

discrete events that 

provide critical 

resources?

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Pregnant females collected in June in New Mexico, Arizona, and 

Durango, Mexico (references in Czaplewski 1983). Temperatebreeding bats tend to have only one litter per year (Barclay and Harder 

2003).

1

Biotic interactions: Allen’s lappet-browed bat (Idionycteris phyllotis)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Hoffmeister (1986) indicated that this species of bat flies later in the 

evening than some other species—most often individuals have been 

caught in nets after 9 p.m. Appears that insects are gleaned from 

vegetation or other surfaces or are consumed in flight (Czaplewski 

1983). This species is insectivorous and feeds primarily on moths but 

also on soldier beetles, dung beetles, leaf beetles, roaches, and flying 

ants (see references in Czaplewski 1983). Flying ants suggested as 

opportunistic feeding (Ross 1967 as cited in Czaplewski 1983).

Overall, appears to feed on a variety of food resources.

0

2. Predators Are important 

predator populations 

expected to change?

According to Czaplewski (1983), no predators of I. phylottis are 

known. 

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found to suggest existence of important symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change?

No blood parasites or other endoparasites have been found in this 

species (Cain and Studier 1974 as cited in Czaplewski 1983). No 

ectoparasites were reported according to Czaplewski (1983), although 

it is likely that some exist. No information indicating significant levels 

of mortality from diseases or parasites.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

This species was observed in the same maternity colony in the Galiuro 

Mountains in a collapsed cave along with Townsend’s big-eared bats, 

California myotis, and fringed myotis (Hoffmeister 1986).

Little information available regarding competitors of this species or of 

competitive interactions affecting bats in general. Potential 

competitors are most likely other bat species and/or birds that forage 

aerially at dusk and dawn (e.g., poorwills and nighthawks; Adams 

2003); competition would be for insect prey and/or access to water 

sources for drinking. Adams (2003) cited work by researchers in 

Colorado that found that bat species typically differed in the time of 

night they visited small water holes. Competition for roosting sites in 

this species may be mostly intra-specific.

0
98 USDA Forest Service RMRS-GTR-273. 2012.

136

Literature Cited

Adams, R.A. 2003. Bats of the Rocky Mountain West. Boulder, CO: University of Colorado Press. 289 p.

Adams, R.A., and M.A. Hayes. 2008. Water availability and successful lactation by bats as related to 

climate change in arid regions of western North America. Journal of Animal Ecology 77:1115:1121.

Arlettaz, R., P. Christe, A. Lugon, N. Perrin, and P. Vogel. 2001. Food availability dictates the timing of 

parturition in insectivorous mouse-eared bats. Oikos 95:105-111.

Barclay, M.R., and L.D. Harder. 2003. Life histories of bats: Life in the slow lane. In: Kunz, T.H., and 

M.B. Fenton, eds. Bat Ecology. Chicago: University of Chicago Press: 209-253.

Cryan, P.M. 2003. Seasonal distribution of migratory tree bats (Lasiurus and Lasionycteris) in North 

America. Journal of Mammalogy 84:579-593.

Czaplewski, N.J. 1983. Idionycteris phyllotis. American Society of Mammalogists. Mammalian Species 

No. 208:1-4.

Frick, W.F., D.S. Reynolds, and T.H. Kunz. 2010. Influence of climate and reproductive timing on 

demography of little brown myotis Myotis lucifigans. Journal of Animal Ecology 79:128-136.

Geluso, K. 2007. Winter activity of bats over water and along flyways in New Mexico. Southwestern 

Naturalist 52:482-492.

Hayes, J.P., and S.C. Loeb. 2007. The influences of forest management on bats in North America. In:

Lacki, M.J., J.P. Hayes, and A. Kurta., eds. Bats in Forests: Conservation and Management. Baltimore, 

MD: Johns Hopkins University Press: 207-235.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Jones, L. 2009. Distribution of bats across the Huachuca Ecosystem Management Area: A preliminary 

assessment for a landscape-level habitat restoration project. 2009 Arizona Bat Conservation Partnership 

Grant Final Report; December 23, 2009; Submitted to Arizona Game and Fish Department, Phoenix, 

and USDA Forest Service, Coronado National Forest, Tucson, Arizona. Forest Service Agreement 

Number 09-CO-11030515-038. Arizona Game and Fish Department Project Number FY-09-06.

Licht, P., and P. Leitner. 1967. Behavioral responses to high temperatures in three species of California 

bats. Journal of Mammalogy 48:52-61.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: a comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Rabe, M.J., T.E. Morrell, H. Green, J. deVos Jr., and C.R. Miller. 1998. Characteristics of ponderosa pine 

snag roosts used by reproductive bats in northern Arizona. Journal of Wildlife Management 

62:612-621.

Siders, M.S., and W. Jolley. 2009. Roost sites of Allen’s lappet-browed bats (Idionycteris phyllotis). 

Southwestern Naturalist 54:201-203.

Solvesky, B.G., and C.L. Chambers. 2009. Roosts of Allen’s lappet-browed bat in Northern Arizona. 

Journal of Wildlife Management 73:677-682.

Speakman, J.R., and D.W. Thomas. 2003. Physiological ecology and energetic of bats. In: Kunz, T.H., 

and M.B. Fenton, eds. Bat Ecology. Chicago: University of Chicago Press: 430-490.

Tumlison, R. 1993. Geographic variation in the lappet-eared bat, Idionycteris phyllotis, with descriptions 

of subspecies. Journal of Mammalogy 74:412-421.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.
USDA Forest Service RMRS-GTR-273. 2012. 99 137

Habitat: Townsend’s big-eared bat (Corynorhinus townsendii)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change? 

Taxonomic note: Family Vespertilionidae. Formerly designated as 

Plecotus townsendii. Subsequently, sub-genus Corynorhinus was 

given status of genus and Plecotus townsendii (along with 2 other 

Plecotus species in North America) were moved into this genus 

(reviewed in Tumlison and Douglas 1992). Various common names 

have been used for the species, including western long-nosed bat and 

western lump-nosed bat, and “pale lump-nosed bat” for this subspecies. Using genetic analysis, Piaggio and Perkins (2005) concluded 

that Corynorhinus townsendii townsendii is the sub-species that occurs 

in Arizona and C. townsendii pallescens occurs in New Mexico and 

Colorado, which differed from prior work by Handley (1959) who 

assigned C. townsendii pallescens to large areas of the western United 

States, including Arizona.

This species occurs only infrequently in desert mountains in Arizona 

(Hoffmeister 1986). In summer, occurs across the state in desert scrub, 

shelters in desert mountains, oak woodlands, pinyon-juniper, and 

coniferous forests (Hoffmeister 1986). Handley (1959) reported that 

this species occurs mainly in Upper Sonoran and Transition life zones, 

in some places ranging into Lower Sonoran Zone, indicating that it is 

uncommon in prairie or extreme desert habitats. Occurs in coniferous 

and deciduous forest throughout much of its range (Kunz and Martin 

1982). In California and Washington, reported in coastal areas and 

hills with mixed vegetation (references in Kunz and Martin 1982). In 

western coniferous forests, reported in coastal humid forest, pinyonjuniper, montane woodland forest, subalpine forest, forest meadow, 

and riparian areas (Hayes 2003).

Found during the day mostly in caves or mine tunnels; may use 

abandoned buildings at night to rest (Hoffmeister 1986). Pregnant 

females occur in maternity colonies; males generally occur in separate 

groups from females during the summer (Hoffmeister 1986). Summer 

colonies in Arizona are generally not large; the largest noted by 

Hoffmeister (1986) was 100 individuals in the Baboquivari Mountains.

This species occurs, or potential habitat exists, on all 12 of the EMAs 

on CNF (Jones, personal communication). Surveys by Jones (2009) on 

Huachuca EMA resulted in no detections of this species. Projections of 

suitable climate for vegetation communities forest wide (Chapter 1) 

predicted declines in suitable climate for all plant community types, 

with the exception of increases of suitable climate for semi-desert 

grassland and a slight increase in Sonoran desert scrub (present in 

small amounts on the CNF).

Not clear to what extent this species uses semi-desert grassland on the 

CNF, which is the plant community that is expected to increase 

(Chapter 1). Humphrey and Kunz (1976) reported this species in 

portions of northwestern Oklahoma and south-central Kansas 

containing mid-grass prairie vegetation invaded by mesquite and sage, 

as well as riparian vegetation where gypsum hills provide topographic 

variation that provided roost sites. Fellers and Pierson (2002) found 

that this species in northern coastal California spent the majority of 

time near riparian trees and shrubs, occasionally spending time in open 

habitats (where trees and shrubs occurred), but individuals generally 

avoided open grassland, both when foraging and traveling between 

roosting and foraging areas.

Given that this species is rare in prairies (Handley 1959) and the 

observation that individuals avoided open grassland (Fellers and 

Pierson 2002), we did not assume that grasslands would substitute for 

2
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Habitat: Townsend’s big-eared bat (Corynorhinus townsendii)

Trait/Quality Question Background info. & explanation of score Points

predicted losses of oak-woodland, pinyon-juniper, and coniferous 

forest habitats that Hoffmeister (1986) indicated are used by this 

species.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Believed to occur in southern Arizona year-round (See Habitat, 

Question 8). See Habitat, Question 1 for discussion of habitat and 

scoring.

Hoffmeister (1986) found bats both hibernating and active within the 

same mine in winter (February 1958); he posed the question of 

whether individuals might need to feed in winter. Three individuals 

were captured while away from roosts in New Mexico in November 

and January (Geluso 2007).

2

3. Habitat

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

Females form maternity colonies in the warm parts of caves, mines, 

and buildings (references in Kunz and Martin 1982). Maternity 

colonies for this species as large as 1000 females have been reported 

(Barbour and Davis 1969 as cited in Nowak 1994); in Oklahoma and 

Kansas, nursery colonies contained 17-40 females (Humphreys and 

Kunz 1976 as cited in Nowak 1994). Hoffmeister (1986) indicated that 

summer colonies in Arizona are not large, with the largest being ~100 

individuals in the Baboquivari Mountains; in winter, this colony had 

~50 individuals, with many hibernacula having fewer. In the Great 

Basin, Sherwin and others (2003) observed some maternity colonies in 

mines to move, often multiple times, during the maternity period, some 

of which was predictable when examined across years, whereas 

maternity colonies in caves typically used the cave for the entire period 

as well as among years; however, the authors warned against 

extrapolating locally derived roosting pattern information to other 

geographic regions. During the spring, males are reported to typically 

occupy areas separate from maternity colonies (references in Kunz and 

Martin 1982), although Sherwin and others (2003) indicated that some 

roosts sites were observed as both maternity and bachelor colonies (not 

clear if use for both purposes was simultaneous). Bachelor colonies in 

the Great Basin were observed to move among a predictable group of 

mines during each year (Sherwin and others 2003).

After an initial bout of feeding at night, individuals use night roosts 

that are often shared by other species (references in Kunz and Martin 

1982).

The abundance of caves, mines, and buildings not expected to change 

as a result of climate change.

Standing water is assumed to be important to this species. In arid 

environments, water can be a resource that limits the presence of bats 

(Hayes and Loeb 2007). Insectivorous bats must obtain much of their 

water intake from free-standing water, unlike frugivorous and 

nectarivorous bats, which obtain much of their water from food 

(Neuweiler 2000 as cited in Hayes and Loeb 2007). Water availability 

is expected to be important to successful reproduction since bats lose a 

large of water to evaporation across their wing membranes (Adams 

2003) and because they lactate. 

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

Uses hibernacula (caves, mines, or buildings) in winter (Kunz and 

Martin 1982). This species prefers relatively cold places for 

hibernation; rarely observed in the warmer parts of winter hibernacula 

(Humphrey and Kunz 1976; references in Kunz and Martin 1982). 

Most limestone caves in California are too warm for successful 

hibernation (Graham 1966 as cited in Kunz and Martin 1982). Sherwin 

and others (2003) observed that in the Great Basin in winter, colonies 

often moved among different roosts within a hibernation season.

1
USDA Forest Service RMRS-GTR-273. 2012. 101

139

Habitat: Townsend’s big-eared bat (Corynorhinus townsendii)

Trait/Quality Question Background info. & explanation of score Points

The abundance of caves, mines, and buildings not expected to be 

altered as a result of climate change.

See Habitat, Question 3 regarding standing water, which is expected to 

decrease.

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

No information found. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

No information found. 0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

While females have shown high site fidelity to maternity roosts 

(Pearson and others 1952; references in Fellers and Pierson 2002), we 

considered bats capable of colonizing new areas due to their capacity 

for flight. The longest movement record in California was 32.2 km 

(Pearson and others 1952), whereas movements of 64 km have been 

reported in Kentucky and West Virginia (Barbour and Davis 1969 as 

cited in Kunz and Martin 1982). Three females were observed to move 

an average of 11.6 km between hibernacula and maternity roosts 

(Humphrey and Kunz 1976).

-1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Hoffmeister (1986) indicated that this species occurs in winter south of 

Mogollon Plateau “but northwest to Ash Fork and Hackberry,” which 

suggests that individuals breeding in northern Arizona may move 

south in winter. Regardless, it appears that individuals breeding in 

southeastern Arizona occur there year-round. Kunz and Martin (1982) 

indicated that the species appears to be relatively sedentary (see 

references therein) and that no long-distance migrations have been 

reported. 

0

Physiology: Townsend’s big-eared bat (Corynorhinus townsendii)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Nocturnal forager, so not active during the hottest parts of the day.

In Oklahoma and Kansas, individuals in small nursery colonies 

showed the ability to maintain thermal exchange during pregnancy 

and lactation, which was facilitated by roosting in dense clusters and 

was considered to be important to reproductive success (Humphrey 

and Kunz 1976). Warmer temperatures might reduce physiological 

demands associated with cold during pregnancy and rearing of young, 

although there may be no effect if phenology of breeding shifts to 

earlier in spring.

In a review of the upper critical temperatures for 50 species of bats, 

the maximum was 41.00 °C and mean was 36.26 °C (Speakman and 

Thomas 2003); upper critical temperature is the ambient temperature 

above which an animal’s body temperature will increase unless it 

pants or sweats. In the case of three species of bats roosting in a barn 

in California in summer (Myotis yumanensis, Antrozous pallidus, and 

Tadarida brasiliensis), when ambient temperature approached 40 °C 

(104 °F), spacing between individuals tended to increase and most 

individuals moved to cooler parts of the loft though some did not 

(Licht and Leitner 1967).

0
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140

Physiology: Townsend’s big-eared bat (Corynorhinus townsendii)

Trait/Quality Question Background info. & explanation of score Points

Overall, we assumed that temperatures are not likely to exceed high 

temperature thresholds. Standing water is expected to become less 

available, but this is covered in Habitat section.

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather

or disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We assumed it 

unlikely that heat waves would cause widespread mortality for this 

species.

See also Physiology, Question 1 above.

0

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation regimes 

that influence activity 

period of species 

expected to change?

Active at night for foraging; are considered late flyers (Hoffmeister 

1986). Given nocturnal foraging activity, increase in temperatures not 

likely to reduce foraging time significantly. Warmer winter 

temperatures may reduce time spent in torpor, but not clear whether 

this will significantly increase activity periods. Furthermore, unclear 

whether increased activity in winter would have a neutral effect or 

negative effect on overall energy balance.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

This species is reported to undergo hibernation in winter though some 

winter activity has been documented. Hibernacula include caves, 

mines, or buildings (Kunz and Martin 1982). Hoffmeister (1986) 

found bats both hibernating and active within the same mine in winter 

(February 1958); Pearson and others (1952) indicated that this species 

has been observed flying in winter months in northern California.

This species appears to arouse from torpor frequently and move its 

position within the hibernaculum or move to a nearby cave or mine; 

this behavior contributes to mass loss (Kunz and Martin 1982). 

Changes in air temperature or humidity can stimulate arousals from 

torpor. Most roost singly in winter although may form clusters from a 

few individuals to several dozen (references in Kunz and Martin 

1982). Use postures that appear to buffer from environmental 

extremes but still can lose body mass during hibernation (up to half of 

the autumn body mass; Humphrey and Kunz 1976).

In maternity colonies, females generally are active but may undergo 

torpor when roost temperatures are low (references in Kunz and 

Martin 1982). Pearson and others (1952) noted that bats in this genus 

may undergo periods of torpor in summer in addition to winter.

Unclear whether increased winter temperatures would reduce 

temperatures appropriate for torpor, resulting in inability of 

individuals to achieve energy savings in winter.

0

6. Survival 

during 

resource 

limitation

Does this species have 

lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

See Physiology ,Question 5. none

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No alternative strategies. 0
USDA Forest Service RMRS-GTR-273. 2012. 103

141

Physiology: Townsend’s big-eared bat (Corynorhinus townsendii)

Trait/Quality Question Background info. & explanation of score Points

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods where 

reproduction is 

limited?

Pearson and others (1952) estimated for sites in California, median 

age estimate of 3.1 years and average age of 5.0 years. One lifespan 

reported by Paradiso and Greenhall (1967) was 16 years 5 months.

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce resources to the point that bats have insufficient 

resources for breeding, but conditions recover after, it is likely that 

sufficient numbers of individuals would survive long enough to breed 

once conditions improve.

-1

Phenology: Townsend’s big-eared bat (Corynorhinus townsendii)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

This species reported to undergo hibernation, which is associated with 

temperature. Rises in spring temperature result in reductions in torpid 

behavior and are likely one trigger for females with respect to 

ovulation (copulation occurs in fall and winter, with ovulation 

occurring in late winter or early spring; Hoffmeister 1986). Pearson 

and others (1952) reported that in California, gestation in this species 

lasts from 56-100 days, depending on spring temperatures and the 

extent of torpor among individuals. On the other hand, the author 

found that in California, there was no clear support that individuals in 

colder regions gave birth later than those in warmer regions.

Temperature and moisture influence insect abundance (this species is 

an insectivore). But any relationship to the timing of parturition would 

be indirect.

1

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Changes in the timing of precipitation and increases in temperature 

can alter the timing of insect availability and abundance; insect prey 

assumed to be important to survival of young.

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

Critical resources are assumed to be insect prey. Since this species 

does not undergo long-distance movements, resources and timing of 

breeding are closely timed (individuals would have local indication of 

resource abundance).

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Breed in fall and winter; sperm is stored and female ovulates in late 

winter or early spring (Hoffmeister 1986). Ovulation may occur either 

before or after females leave hibernacula (Kunz and Martin 1982). A 

single young is produced.

1
104 USDA Forest Service RMRS-GTR-273. 2012.

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Biotic interactions: Townsend’s big-eared bat (Corynorhinus townsendii)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Feed mostly on small moths averaging 6 mm long; may take other 

insects of the Orders Neuroptera, Coleoptera, Diptera, and 

Hymenoptera (references in Kunz and Martin 1982). Members of this 

genus capture insects in flight as well as pick insects from foliage 

while hovering (Nowak 1994). Eastern sub-species said to be 

Lepidopteran specialists.

Given that this species is said to feed primarily on 

microlepidopterans, we scored this question “1” because there may be 

limited alternative prey opportunities if microlepidopterans are 

negatively impacted by climate change.

1

2. Predators Are important 

predator populations 

expected to change?

Pearson and others (1952) considered it unlikely that predation was 

very high; considered the overall number of suitable winter roosting 

sites and the number of summer roosting sites surrounded by suitable 

feeding areas to be the main limits on population size for this species. 

Fellers (2002) presented evidence suggesting that predation by rats 

was the primary cause of reproductive failure of a large maternity 

colony in California located in an abandoned house built in the 1880s.

No information found to suggest that predation levels would change 

as a result of climate change.

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found to suggest existence of important symbiotic 

relationships.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Rabies virus was found in less than 1% of asymptomatic individuals 

sampled in New Mexico (Constantine 1967 as cited in Kunz and 

Martin 1982). Endoparasites reported include 2 nematodes and a 

cestode; ectoparasites include winged bat flies (Streblidae family), 

wingless bat flies (Nycteribiidae), macronyssid mites, ticks, a species 

of chigger, and sarcoptid mites (references in Kunz and Martin 1982; 

Ritzi and others 2001), but no indication that these cause significant 

mortality for the species.

Pearson and others (1952) considered it unlikely that disease had a 

substantial role in population control given how rare unhealthy 

individuals were encountered; the author considered the overall 

number of suitable winter roosting sites and the number of summer 

roosting sites surrounded by suitable feeding areas as the main limits 

on population size for this species.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Little information available regarding competitors of this species or of 

competitive interactions affecting bats in general. Potential 

competitors are most likely other bat species and/or birds that forage 

aerially at dusk and dawn (e.g., poorwills and nighthawks; Adams

2003); competition would be for insect prey and/or access to water 

sources for drinking. Adams (2003) cited work by researchers in 

Colorado that found that bat species typically differed in the time of 

night they visited small water holes.

0

Literature Cited

Adams, R.A. 2003. Bats of the Rocky Mountain West. Boulder, CO: University of Colorado Press. 289 p.

Fellers, G.M. 2002. Predation on Corynorhinus townsendii by Rattus rattus. Southwestern Naturalist 

45:524-527.

Fellers, G.M., and E.D. Pierson. 2002. Habitat use and foraging behavior or Townsend’s big-eared bat 

(Corynorhinus townsendii) in coastal California. Journal of Mammalogy 83:167-177.
USDA Forest Service RMRS-GTR-273. 2012. 105

143

Geluso, K. 2007. Winter activity of bats over water and along flyways in New Mexico. Southwestern 

Naturalist 52:482-492.

Handley, C.O., Jr. 1959. A revision of American bats of the Genera Euderma and Plecotus. Proceedings 

of the United States National Museum 110:95-246.

Hayes, J.P. 2003. Habitat ecology and conservation of bats in western coniferous forests. In: Zabel, C.J., 

and R.G. Anthony, eds. Mammal Community Dynamics: Management and Conservation in the 

Coniferous Forests of Western North America. Cambridge, United Kingdom: Cambridge University 

Press: 81-119.

Hayes, J.P., and S.C. Loeb. 2007. The influences of forest management on bats in North America. In:

Lacki, M.J., J.P. Hayes, and A. Kurta., eds. Bats in Forests: Conservation and Management. Baltimore, 

MD: Johns Hopkins University Press: 207-235.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Humphrey, S.R., and T.H. Kunz. 1976. Ecology of a Pleistocene relict, the Western big-eared bat 

(Plecotus townsendii), in the southern Great Plains. Journal of Mammalogy 57:470-494.

Jones, L. 2009. Distribution of bats across the Huachuca Ecosystem Management Area: A preliminary 

assessment for a landscape-level habitat restoration project. 2009 Arizona Bat Conservation Partnership 

Grant Final Report; December 23, 2009; Submitted to Arizona Game and Fish Department, Phoenix, 

and USDA Forest Service, Coronado National Forest, Tucson, Arizona. Forest Service Agreement 

Number 09-CO-11030515-038. Arizona Game and Fish Department Project Number FY-09-06.

Jones, Larry. 2010. [Personal communication]. February 17, 2010. Tucson, AZ: U.S. Department of 

Agriculture, Forest Service, Coronado National Forest, Assistant Program Manager for Wildlife, Fish, 

and Rare Plants.

Kunz, T.H., and R.A. Martin. 1982. Plecotus townsendii. American Society of Mammalogists. 

Mammalian Species No. 175: 1-6.

Licht, P., and P. Leitner. 1967. Behavioral responses to high temperatures in three species of California 

bats. Journal of Mammalogy 48:52-61.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Nowak, R.M. 1994. Walker’s Bats of the World. Baltimore, MD: Johns Hopkins University Press.

Paradiso, J.L., and A.M. Greenhall. 1967. Longevity records for American bats. American Midland 

Naturalist 78:251-252.

Pearson, O.P., M.R Koford, and A.K. Pearson. 1952. Reproduction of the lump-nosed bat (Corynorhinus 

rafinesquei) in California. Journal of Mammalogy 33:272-320.

Piaggio, A.J., and S.L. Perkins. 2005. Molecular phylogeny of North American long-eared bats 

(Vespertilionidae: Corynorhinus); inter- and intraspecific relationships inferred from mitochondrial and 

nuclear DNA sequences. Molecular Phylogenetics and Evolution 37:762-775.

Ritzi, C.M., L.K. Ammerman, M.T. Dixon, and J.V. Richerson. 2001. Bat ectoparasites from the TransPecos region of Texas, including notes from Big Bend National Park. Journal of Medical Entomology 

38:400-404.

Sherwin, R.E., W.L. Gannon, and J.S. Altenbach. 2003. Managing complex systems simply: 

understanding inherent variation in the use of roosts by Townsend’s big-eared bat. Wildlife Society 

Bulletin 31:62-72.

Speakman, J.R., and D.W. Thomas. 2003. Physiological ecology and energetic of bats. In: Kunz, T.H., 

and M.B. Fenton, eds. Bat Ecology. Chicago: University of Chicago Press: 430-490.

Tumlison, R., and M.E. Douglas. 1992. Parsimony analysis and phylogeny of the plecotine bats 

(Chiroptera: Vespertilionidae). Journal of Mammalogy 73:276-285.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.
106 USDA Forest Service RMRS-GTR-273. 2012. 144

Habitat: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change? 

Range in the Unites States is Wyoming, Colorado, Utah, New 

Mexico, and Arizona; also occurs in portions of Mexico (from 

northern Sonora to southern Durango; Nash and Seaman 1977). While 

typically considered dependent on ponderosa pine for food, cover, and 

nest sites, this species has been reported in pinyon pine, Douglas-fir, 

and spruce fir (see review in Hutton and others 2003). On Mount 

Graham, Hutton and others (2003) documented this species in mixed 

conifer and spruce-fir between 1989 and 2003.

This species is considered invasive on the CNF although native 

populations occur in northern Arizona. It was introduced into the 

Pinaleño and Santa Catalina EMAs (Jones, personal communication). 

Introduction to Mount Graham in the Pinaleño Mountains occurred in 

the 1940s (Hutton and others 2003). Projections of suitable climate 

for vegetation communities (Chapter 1) predicted declines in suitable 

conditions for Madrean forest and woodland, Madrean conifer forest 

and increases of suitable conditions for semi-desert grassland, and, to 

a lesser extent, Sonoran desert scrub.

Expect that habitat for this species will decrease as a result of climate 

change.

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Same as breeding habitat (See Habitat, Question 1). 2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

Tree squirrels (Sciurus and Tamiasciurus) use nests for rearing young, 

rest, predator avoidance, and cover during inclement weather (Steel 

and Koprowski 2001). Abert’s squirrels use tree dreys (spherical twig 

nests they build) and, to a lesser extent, tree cavities (Edelman and 

Koprowski 2007). Dreys were more often in trees that were larger and 

taller than random trees in a study in the Pinaleño Mountains; some 

individuals used cavities for nests (Edelman and Koprowski 2005a). 

Cavity nests accounted for ~10% of the nests, and aspen was the most 

common tree species used for cavity nests (Edelman and Koprowski 

2006).

Trees, overall, are expected to decline in abundance.

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

Uses nests and cavities in winter (see Habitat, Question 3). 1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change?

“Survivorship and reproduction of tree squirrels often are positively 

correlated with tree seed production. This dependence on mature, 

seed-producing forests is likely one reason that several species of tree 

squirrels are considered to be threatened or endangered in all or part 

of their ranges...” (Koprowski and Corse 2001). Recruitment in 

Abert’s Squirrels in north-central Arizona was positively related to 

the number of interlocking canopy trees (Dodd and others 2003).

Mature trees with high mast yields are expected to decline due to fire 

and increased aridity. 

1
USDA Forest Service RMRS-GTR-273. 2012. 107

145

Habitat: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change?

See Habitat, Question 5.

Density of this species was positively related to fecal fungal diversity; 

winter survival was negatively related to snow cover duration and 

positively related to dietary fungal diversity (Dodd and others 2003); 

fecal fungal content in August was, in turn, positively related to basal 

area for all tree species.

Logging has been associated with loss of high-quality foods, which 

has led to increased mortality (references in Keith 2003), indicating 

the importance of trees for food.

1

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Tree squirrels are reported to “routinely move distances of 1 km” 

(references in Koprowski 2005). Little other information found on 

dispersal. We assumed that both sexes are mobile.

-1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

This species is a year-round resident. 0

Physiology: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Abert’s squirrels are strictly diurnally active (Nash and Seaman 

1977). Activity usually begins in the morning with the first light and 

continues until dusk, with rest periods during the day (Brown 1984). 

Generally spends the afternoon in a nest or on a foliage-shaded limb 

(or when cold, may bask in the sun on a limb) (Brown 1984).

Squirrels may become inactive outside of the nest when temperatures 

are high (Gurnell 1987). Rainfall does not typically reduce activity 

unless it is heavy (references in Gurnell 1987). Squirrels spend most 

time foraging in trees in summer. Tree squirrels are reported to use 

evaporative cooling following periods of activity when temperatures 

are high (may lose heat from sweat glands in feet; Gurnell 1987). We 

assumed that temperatures will remain below physiological 

thresholds most of the time.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather 

or disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity 

of heat waves will affect survival and reproduction. We assumed it is 

not likely that heat waves would cause widespread mortality for this 

species.

See also Physiology, Question 1.

0

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation regimes 

that influence activity 

period of species 

expected to change?

This species is diurnally active. During summer, squirrels tend to 

have 2 periods of activity—morning and later afternoon (Gurnell 

1987). We assumed that rise in temperatures would not significantly 

impact morning and evening activity periods.

See also Physiology, Question 1.

0
108 USDA Forest Service RMRS-GTR-273. 2012.

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Physiology: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Active year-round, even during inclement winter weather (Golightly 

and Ohmart 1978). Abert’s squirrels will co-occupy nests in winter; 

the proportion of individuals that nest communally in winter 

increased with decreasing temperature in a population studied in the 

Pinaleño Mountains (Edelman and Koprowski 2007).

Golightly and Ohmart (1978) studied heterothermy in Abert’s 

squirrels in the wild and in the lab. Body temperature rose in 

association with periods of intense activity in both winter and 

summer; this species often sought shade after these periods. In the 

laboratory, body temperature decreased as ambient temperatures 

decreased; metabolic expenditures also declined.

Although there is not strong evidence that this species uses torpor on 

a daily basis when temperatures are cold, the fact that squirrels are 

known to lower body temperature at night and when at rest suggests 

some ability to reduce energy requirements. This led to the choice of 

“-1” for this question.

-1

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Brown (1984) indicated that Abert’s squirrels generally do not seem 

to cache many cones. Keith (2003) indicated that this species does 

not cache food.

Appears that squirrels do not deposit large amounts of subcutaneous 

fat for insulation, although they may increase fat reserves in other 

parts of the body (Gurnell 1987). This species molts twice a year, 

with thicker coat in winter.

1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to

cope with variable 

resources or climate 

conditions?

None reported. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods where 

reproduction is 

limited?

Barkalow and Soots (1975) cited references that indicate that gray 

squirrels rarely live longer than 6 years in the wild. In their own 

study, of 10 wild eastern gray squirrels (Sciurus carolinensis), the 

shortest survival was 6 years and the longest was 12.5 years 

(Barkalow and Soots 1975). A study of red squirrels (Tamiasciurus 

hudsonicus) in Montana found that 67% of individuals died before 12 

months, with a plateau in survivorship occurring at about 36 months 

and very few individuals surviving past 7 years (Halvorson and 

Engeman 1983).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that squirrels have 

insufficient food for breeding, most of the population would not 

survive longer than the periods of limited reproduction.

1

Phenology: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

The onset of breeding season in this species is reported to coincide 

with the production of male flowers of the ponderosa pine, reportedly 

leading to individuals coming into breeding condition (see references 

in Brown 1984: 26). Keith (2003) questioned this because staminate 

flower opening is controlled by temperature that generally does not 

occur until late May or early June (various authors have reported range 

of mating dates as early as mid-February through June).

0
USDA Forest Service RMRS-GTR-273. 2012. 109

147

Phenology: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

It is likely that food availability of some kind is important and that 

temperature and moisture influence the availability, but since the 

relationship to squirrel breeding is indirect, this question was scored as 

“0.” Also note that ponderosa pine is not the only tree species 

consumed by this species (see Biotic Interactions, Question 1), so 

likely that flowers of other tree species could be important. 

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

According to Brown (1984), a female is receptive to breeding for only 

about 18 hours once each year and that not all females come into 

estrus each year. Males are in reproductive condition from 

approximately the end of April to the end of June (although amongindividual and among-year variation exists; Brown 1984). If the onset 

of breeding activity is correlated with flower emergence and 

consumption of flower parts (Brown 1984; see Phenology, Question 

1), warmer temperatures may lead to earlier flowering or to alterations 

to the availability of other types of food.

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

We considered food a critical resource and assumed a relatively short 

period of time between food availability and breeding. See Phenology, 

Question 2.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

According to Brown (1984), a female is receptive to breeding for only 

about 18 hours once each year and not all females come into estrus 

each year. This characteristic increases its vulnerability to a mismatch 

between resource availability and the breeding period.

1

Biotic interactions: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

This species does not cache food regularly (references in Keith 2003). 

Overall, the diet of this species varies by location and season (Keith 

2003), presumably based on availability of various foods. Some 

records indicate that this species is dependent on ponderosa pine for 

food (including seeds, apical buds, staminate cones, inner bark, and 

hypogeous [subterranean] fungi associated with ponderosa pine; see 

references in Edelman and Koprowski 2005b).

However, other reports (Edelman and Koprowski 2005b) observed 

consumption of other species of tree. In the Pinaleño Mountains, 

seeds of Southwestern white pine and Douglas-fir were most 

commonly consumed; ponderosa pine seeds were consumed in lesser 

amounts; and corkbark fir and Englemann spruce seeds were never 

eaten. Other parts (e.g., apical buds, inner bark, and staminate

flowers) of these tree species were consumed, with the preference 

varying by tree species. In one study, the availability of food (truffles, 

acorns, cones, and mushrooms) varied annually over a 5-year period 

(States and others 1988 as cited in Keith 2003)

1
110 USDA Forest Service RMRS-GTR-273. 2012.

148

Biotic interactions: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

In central Arizona, pine seeds were estimated to comprise more than 

50% of the diet between June and October, and inner bark was 

estimated to comprise 50% of the diet between December and May 

(Keith 1965). Gurnell (1987) indicated that the species in southern 

United States consumes mostly fungi in summer and autumn and a 

large proportion of bark in winter; other consumed components are 

staminate flowers (winter and spring), seeds (all seasons), and buds 

(spring). Brown (1984) indicated that truffles of the genera 

Gautierea, Rhizopogon, and Morchella are “probably the most 

consistent important dietary items.” Hoffmeister (1986) indicated that 

in the Flagstaff, Arizona, area, nearly all cone-producing ponderosa 

pines are at least 60 years old. On the other hand, over-mature trees 

are said to produce low-quality cones and the inner bark is reduced in 

nutritive value.

This species appears to be able to vary its diet species, but depends 

heavily on trees for food, including seeds, and trees are expected to 

decline. 

2. Predators Are important 

predator populations 

expected to change?

Goshawks have been documented as preying on Abert’s squirrels 

(Reynolds 1963). Gurnell (1987) indicated that red-tailed hawks, redshouldered hawks, goshawks, and martens hunt squirrels more 

frequently than other predatory species; however, no species of 

Martes occurs in Arizona. Gurnell (1987) indicated “there is little 

evidence that predators have any impact on squirrel populations.”

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

Relationship between squirrels and seed crop considered under Biotic 

Interactions, Question 1.

Given that this species not considered to cache large numbers of 

acorns/seeds, not clear to what extent it acts as a seed disperser for 

tree species.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Squirrels are host to a variety of parasites and diseases (Gurnell 

1987). Diseases include distemper, diphtheria, scab disease, 

myxomatosis (myxoma viral infection), and parapoxvirus infection. 

Gray squirrels in the Midwest have acquired California encephalitis. 

Little is known about pathogenicity of most parasite and disease 

organisms in squirrels. Coccidiosis (infection by protozoan, coccidian 

in intestinal wall) can cause serious infections that weaken squirrels. 

Ectoparasites, including fleas, are common in squirrels (Gurnell 

1987). Mortality from plague appears to be uncommon in tree 

squirrels.

A search on Web of Science for “plague” and “Sciurus” yielded no 

results. A search of “plague” and “tree squirrels” yielded only 

Hudson and others (1971), which mentioned a case of eastern fox

squirrels (Sciurus niger) dying in urban Denver in 1968, some of 

which were positive for antigens to plague and/or had fleas that were 

host to Yersinia pestis (bacterium that causes plague). A Web of 

Science search on “Tamiasciurus” and “plague” returned Smith and 

others (2010), who reported that seroprevalence for Yersinia pestis

was high in Allen’s and long-eared chipmunks (Tamias senex and T. 

quadrimaculatus) and in the pine squirrel (Tamiasciurus douglasii) in 

northern California over 28 years of monitoring, but that all 3 were 

moderately resistant to plague and survived infection.

Bot flies (Cterebra spp.) lay eggs in nests of several types of squirrels 

including gray squirrels; the larvae then burrow into the skin of 

squirrels, eventually re-emerging and dropping off to pupate.

West Nile Virus (WNV) was first reported in eastern fox squirrels 

(Sciurus niger) in 2003 (Kiupul and others 2003). Most mammalian 

0
USDA Forest Service RMRS-GTR-273. 2012. 111

149

Biotic interactions: Abert’s squirrel (Sciurus aberti)

Trait/Quality Question Background info. & explanation of score Points

WNV infections cause no or low morbidity or mortality, although 

tree squirrels are susceptible to a neurologic disease associated with 

infection (Padgett and others 2008).

Gurnell (1987) indicated that squirrels that are weakened by food 

shortage may develop a parasite or disease load heavy enough to 

cause mortality. Large squirrel mortality events were reported in 

Europe in the early 1900s; coccidiosis was reported to have killed one 

million Eurasian red squirrels in Finland from 1943-1944 (Lampio 

1967 as cited in Gurnell 1987). 

5. Competitors Are populations of 

important competing 

species expected to 

change?

Mount Graham red squirrel is likely impacted by Abert’s squirrel. It 

has been suggested that red squirrels declined in abundance following 

the introduction of Abert’s squirrel (Hoffmeister 1956 as cited in 

Hutton and others 2003). Abert’s squirrels observed in red squirrel 

middens on Mount Graham, including being chased from middens by 

red squirrels (Hutton and others 2003). Possible that the two species 

may compete for food on Mount Graham (Hutton and others 2003). 

Mount Graham red squirrel expected to be vulnerable to climate 

change.

-1

Literature Cited

Barkalow, F.S., Jr., and R.F. Soots, Jr. 1975. Life span and reproductive longevity of the gray squirrel, 

Sciurus c. carolinensis Gmelin. Journal of Mammalogy 56:522-524.

Brown, D.E. 1984. Arizona’s Tree Squirrels. Phoenix: Arizona Game and Fish Department. 114 p.

Dodd, N.L., J.S. States, and S.S. Rosenstock. 2003. Tassel-eared squirrel population, habitat condition, 

and dietary relationships in north-central Arizona. Journal of Wildlife Management 67:622-633.

Edelman, A.J., and J.L. Koprowski. 2007. Communal nesting in asocial Abert’s squirrels: The role of 

social thermoregulation and breeding strategy. Ethology 113:147-154.

Edelman, A.J., and J.L. Koprowski. 2006. Characteristics of Abert’s squirrel (Sciurus aberti) cavity nests. 

Southwestern Naturalist 51:64-70.

Edelman, A.J., and J.L. Koprowski. 2005a. Selection of drey sites by Abert’s squirrels in an introduced 

population. Journal of Mammalogy 86: 1220-1226.

Edelman, A.J., and J.L. Koprowski. 2005b. Diet and tree use of Abert’s squirrels (Sciurus aberti) in a 

mixed-conifer forest. Southwestern Naturalist 50:461-465.

Edelman, A.J., and J.L. Koprowski. 2001. North American Tree Squirrels. Washington, DC: Smithsonian 

Institution Press.

Golightly, R.T., Jr., and R.D. Ohmart. 1978. Heterothermy in free-ranging Abert’s squirrels (Sciurus 

aberti). Ecology 59:897-909.

Gurnell, J. 1987. The Natural History of Squirrels. New York: Facts on File Publications. 201 p.

Halvorson, C.H., and R.M. Engeman. 1983. Survival analysis for a Red squirrel population. Journal of 

Mammalogy 64:332-336.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Hudson, B.W., M.I. Goldenberg, J.D. McCluskie, H.E. Larson, C.D. McGuire, A.M. Barnes, and J.D. 

Poland. 1971. Serological and bacteriological investigations of an outbreak of plague in an urban tree 

squirrel population. American Journal of Tropical Medicine and Hygiene 20:255-263.

Hutton, K.A., J.L. Koprowski, V.L. Greer, M.I. Alanen, C.A. Schauffert, and P. J. Young. 2003. Use of 

mixed-conifer and spruce-fir forests by an introduced population of Abert’s squirrels (Sciurus aberti). 

Southwestern Naturalist 48:257-260.
112 USDA Forest Service RMRS-GTR-273. 2012.

150

Jones, Larry. 2010. [Personal communication]. February 18, 2010. Tucson, AZ: U.S. Department of 

Agriculture, Forest Service, Coronado National Forest, Assistant Program Manager for Wildlife, Fish, 

and Rare Plants.

Keith, J.O. 2003. Abert’s Squirrel (Sciurus aberti): A technical assessment. Online. U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Region. Available: 

http://www.fs.fed.us/r2/projects/scp/assessments/abertsquirrel.pdf. Accessed: March 26, 2010.

Keith, J.O. 1965. The Abert Squirrel and its dependence on ponderosa pine. Ecology 46:150-163.

Koprowski, J.L., and M.C. Corse. 2001. Food habits of the Chiricahua fox squirrel (Sciurus nayaritensis 

chiricahuae). Southwestern Naturalist 46:62-65.

Koprowski, J.L. 2005. Management and conservation of Tree Squirrels: The importance of endemism, 

species richness, and forest condition. In: Gottfried, G.J., S. Brooke, L.G. Eskew, C.B. Carleton, comps. 

Connecting mountain islands and desert seas: Biodiversity and management of the Madrean 

Archipelago II. 2004 May 11-15; Tucson, AZ. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station: 245-250.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Nash, D.J., and R.N. Seaman.1977. Sciurus aberti. American Society of Mammalogists. Mammalian 

Species No. 80.

Padgett, K.A., W.K. Riesen, N. Kahl-Purcell, Y. Fang, B. Cahoon-Young, R. Carney, N. Anderson, L. 

Zucca, L. Woods, S. Husted, and V.L. Kramer. 2008. West Nile Virus infection in tree squirrels 

(Rodentia: Sciuridae) in California, 2004-2005. Journal of Wildlife Rehabilitation 29:35-39.

Reynolds, H.G. 1963. Western goshawk takes Abert squirrel in Arizona. Journal of Forestry 61:839.

Smith, C.R., J.R. Tucker, B.A. Wilson, and J.R. Clover. 2010. Plague studies in California: A review of 

long-term disease activity, flea-host relationships and plague ecology in the coniferous forests of the 

southern Cascades and northern Sierra Nevada Mountains. Journal of Vector Ecology 35:1-12.

Steele, M.A., and J.L. Koprowski. 2001. North American Tree Squirrels. Washington, DC: Smithsonian Institution Press. 

225 p.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. Tucson, AZ: U.S. 

Department of Agriculture, Forest Service. Available: http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnfecological-sustainability-report-final-022009.pdf.

Habitat: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change? 

Summarized from Best and Reidel (1995):

This species occurs at elevations of 1100 m to greater than 2700 m in 

Arizona, New Mexico, and Sonora, Mexico. In Arizona, it occurs on 

the Mogollon Plateau and in many isolated mountain ranges. In 

Arizona, occurs in “dense, mixed broadleaf communities of ripariandeciduous forest,” although in southern parts of the state, it may occur 

away from deciduous trees where there are tall oaks in uplands. Many 

populations occur along streams that extend to elevations as low as 

semi-desert grassland and chaparral but only where the “riparian 

forest has high species diversity and tall, interlocking canopies.” 

Reported not to occupy more open woodlands that are flood-prone or 

cottonwood-willow communities at lower elevations (Brown 1984), 

although in New Mexico, has been reported in floodplains (Frey and 

others 2008). Occurs in mature forest with tall trees and prefers 

groves of old sycamore and other large deciduous trees (cottonwood, 

box elder, Arizona elder, big-tooth maple, ash, willows, and Gambel 

oak) where cavities are apt to develop. Large evergreen oaks appear 

to be present throughout their range, even if not readily visible. 

Arizona walnut, Arizona oak, and Gambel oak are important sources 

2
USDA Forest Service RMRS-GTR-273. 2012. 113

151

Habitat: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

of mast, cavities, and nest platforms. No records of this species in 

coniferous riparian forests such as blue spruce alliance (Muldavin and 

others 2000 as cited in Frey and others 2008).

In Arizona, uses hollows in deciduous trees. Builds conspicuous leaf 

nests; uses nest even during winter. An individual may have multiple 

leaf nests. Platform nests are used in summer for resting; a larger, 

covered nest is used for a nursery and living, apparently when dens 

are not available.

This species occurs, or potential habitat exists, on the following 

EMAs: Tumacacori, Santa Rita, Huachuca, and Santa Catalina (USFS 

2009). Projections of suitable climate for vegetation communities 

(Chapter 1) predicted declines in suitable conditions for Madrean 

forest and woodland and Madrean conifer forest, and increases in 

suitable conditions for semi-desert grassland and, to a lesser extent, 

Sonoran desert scrub.

We expected that habitat for this species will decrease as a result of 

climate change.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to change?

Same as breeding habitat. 2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

Requires tall trees for breeding in dens (hollows in trees) or in leaf 

nests constructed on branches. Nest trees are greater than 12 m tall 

and nests are frequently located 11-18 m above the ground (Best and 

Reidel 1995). Occupies hollows in deciduous trees, including ash, 

sycamore, and cottonwood (references in Best and Reidel 1995). 

Nests are most commonly built in different species of oaks, but this 

species also uses sycamores, walnut trees, alders, maples, 

cottonwoods, ash trees, and Apache pines (Best and Reidel 1995). 

Also reported to use flat platform nests in summer for resting.

Trees, overall, are expected to decline in abundance.

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

non-breeding 

periods expected to 

change?

Appears to use hollows and leaf nests in winter as well as in summer; 

see above Habitat, Question 3.

1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change?

“Survivorship and reproduction of tree squirrels often are positively 

correlated with tree seed production. This dependence on mature, 

seed-producing forests is likely one reason that several species of tree 

squirrels are considered to be threatened or endangered in all or part 

of their range (Koprowski and Corse 2001).”

Mature trees with high mast yields are expected to decline.

1

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

See Habitat, Question 5. 1
114 USDA Forest Service RMRS-GTR-273. 2012.

152

Habitat: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Although Sciurus and Tamiasciurus spp. generally remain in the same 

area once they are established residents (unless there is a food 

shortage) (Gurnell 1987), squirrels, in general, are very mobile. 

Gurnell (1987) cited several studies on movement of gray squirrel in 

Minnesota, including juveniles moving more than 1 km from their 

natal area (Gull 1977 as cited in Gurnell 1987).

-1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

An old record indicated that this species may move from high 

elevations into areas with oaks at lower elevations in summer (Dice 

and Blossom 1937 as cited in Best and Reidel 1995). However, not 

clear that this behavior is exhibited regularly or by many populations 

or that it is a requirement. 

0

Physiology: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

This species is diurnally active. Squirrels may become inactive 

outside of the nest when temperatures are high (Gurnell 1987). 

Rainfall does not typically reduce activity unless it is heavy 

(references in Gurnell 1987). Squirrels spend most time foraging in 

trees in summer. Tree squirrels are reported to use evaporative 

cooling following periods of activity when temperatures are high 

(may lose heat from sweat glands in feet; Gurnell 1987).

We assumed temperatures will remain below physiological thresholds 

most of the time.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality for this 

species.

See also Physiology, Question 1.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

This species is diurnally active. During summer, squirrels tend to 

have two periods of activity—morning and later afternoon; Gurnell 

1987). We assumed that rise in temperatures will not significantly 

impact morning and evening activity periods.

See also Physiology, Question 1.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Squirrels are active year-round, and in winter tend to have one main 

active period each day; in northern areas, activity period may occur 

closer to the middle of the day than in southern regions (Gurnell 

1987). Spend time in nests in winter to conserve body heat. In severe 

weather conditions, squirrels may remain in nests for several days 

(references in Gurnell 1987: 55).

When at rest, this species’ body temperature declines a few degrees, 

particularly at night when in the nest; this phenomenon has sometimes 

been referred to as heterothermy (Gurnell 1987). Some evidence to 

suggest that squirrels are able to employ a form of adaptive 

hypothermia (see Gurnell 1987: 66).

-1
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153

Physiology: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

Although there is not strong evidence that this species uses torpor on 

a daily basis when temperatures are cold, the fact that squirrels are 

known to lower body temperature at night and when at rest suggests 

some ability to reduce energy requirements. This led to the score of 

“-1” for this question.

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Best and Reidel (1995) reported that this species does not cache food 

and usually does not bury nuts but may bury acorns in leaf litter. 

Brown (1984) also indicated this species is a forager and does not 

cache food nor regularly bury nuts, although there are some 

observations of individuals hiding nuts under leaf litter. No 

information on whether retrieval of buried acorns is a common 

behavior.

Note: Brown (1984) noted that eastern species that are closely related 

do cache; further support for this from Steele and others (2008) for 

eastern gray squirrel(Sciurus carolinensis).

Appears that squirrels do not deposit large amounts of subcutaneous 

fat for insulation, although they may increase fat reserves in other 

parts of the body (Gurnell 1987). This species molts twice a year, 

with thicker coat in winter.

1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

None reported. 0

8. 

Reproduction 

in variable 

environments

Can this species

outlive periods 

where reproduction 

is limited?

Gurnell (1987) indicated that gray squirrels may survive in the wild as 

long as 8-10 years (the longevity record for western gray squirrels in 

captivity is 11 years) but that perhaps only 1% of individuals survive 

that long. Of 10 wild eastern gray squirrels (Sciurus carolinensis), the 

shortest survival was 6 years and the longest was 12.5 years 

(Barkalow and Soots 1975); the authors cited references indicating 

that this species rarely lives longer than 6 years. A study of red 

squirrels (Tamiasciurus hudsonicus) in Montana found that 67% of 

individuals die before 12 months, with a plateau in survivorship 

occurring at about 36 months and very few individuals surviving past 

7 years (Halvorson and Engeman 1983).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that squirrels have 

insufficient food for breeding, most of the population would not 

survive longer than the periods of limited reproduction. 

1

Phenology: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species use 

temperature or 

moisture cues to 

initiate activities 

related to fecundity or 

survival? 

Onset of breeding activity is correlated with flower emergence and 

consumption of flower parts (Best and Reidel 1995). Temperature 

and moisture influence flowering, but since the relationship to 

squirrel breeding is indirect, this question was scored as “0.”

0

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

Estrus for most individuals appears to be in April and early May, 

but breeding can occur as early as January or February (Brown 

1984). It appears that not all females breed each year (Brown 1984). 

1
116 USDA Forest Service RMRS-GTR-273. 2012.

154

Phenology: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

discrete events that 

are expected to 

change? 

The onset of breeding activity is correlated with flower emergence 

and consumption of flower parts (Best and Reidel 1995); warmer 

temperatures may lead to earlier flowering (see also Phenology, 

Question 3).

3. Mismatch 

potential

What is the separation 

in time or space 

between cues that 

initiate activities and 

discrete events that 

provide critical 

resources?

Onset of breeding activity is correlated with flower emergence and 

consumption of flower parts (Best and Reidel 1995). However, 

given the range of months over which potential species are 

flowering (i.e., some begin flower as early as January) and the fact 

that estrus for most individuals appears to be in April and early May 

(breeding can occur as early as January or February; Brown 1984), 

unclear how squirrels are timing breeding with respect to 

consumption of flower parts.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

No information that females rear more than one litter per year (Best 

and Reidel 1995). No evidence that this species has a litter in fall as 

is the case with fox squirrels and gray squirrels in the eastern United 

States (Brown 1984). Not all females breed in each year based on 

the absence of placental scars (Brown 1984). Hoffmeister (1986) 

cited that Theobald and Brown (1982) also found no evidence of a 

second litter.

1

Biotic interactions: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Squirrels eat tree buds in spring as an important food source when 

seeds are scarce or in autumn if a seed crop fails (Gurnell 1987). The 

Arizona gray squirrel consumes mostly tree seeds and fruits, but also 

fungi, buds, and miscellaneous items; the proportions in the diet vary 

by season (Gurnell 1987). Consumption of flower parts in breeding 

season may be related to vitamin content and potential to stimulate 

breeding (Brown 1984).

This species is a forager and does not cache food or regularly bury 

nuts; mast said to be 67% of the annual diet, including walnuts, 

acorns, juniper berries, hackberries, and pine seeds (Brown 1984). 

When all riparian trees and other flowing species are considered in 

total, there is a relatively long flowering period (Brown 1984). 

Occasionally, squirrels eat bird eggs and nestlings and invertebrates 

(Brown 1984). Hoffmeister (1986) indicated that this species feeds 

extensively on walnuts.

The score reflects the potential for reduction in nut/seed/acorn crops. 

Reduced crops expected as a result of reduced precipitation in the 

short term (Zlotin and Parmenter 2008); in the long term, fewer 

seeds expected as a result of reduced tree abundance.

1

2. Predators Are important 

predator 

populations 

expected to 

change?

Predators include goshawks (Hobbs 1980 as cited in Brown 1984), 

red-tailed hawks, and bobcats (Brown 1984). Gurnell (1987) 

indicated that red-tailed hawks, red-shouldered hawks, goshawks, 

and martens hunt squirrels more frequently than other predatory 

species; however, no species of Martes occurs in Arizona and redshouldered hawks are rare in southeast Arizona. Overall, we 

considered this species to have a “suite of predators.” Gurnell (1987) 

indicated “there is little evidence that predators have any significant 

impact on squirrel populations.”

0
USDA Forest Service RMRS-GTR-273. 2012. 117

155

Biotic interactions: Arizona gray squirrel (Sciurus arizonensis)

Trait/Quality Question Background info. & explanation of score Points

3. Symbionts Are populations of 

symbiotic species 

expected to 

change?

Relationship between squirrels and seed crop considered under 

Biotic Interactions, Question 1. Given that this species is not 

considered to cache large numbers of acorns/seeds, not clear to what 

extent it acts as a seed disperser for tree species.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to 

change? 

Squirrels are host to a variety of parasites and diseases (Gurnell 

1987). Diseases include distemper, diphtheria, scab disease, 

myxomatosis (myxoma viral infection), and parapoxvirus infection. 

Gray squirrels in the Midwest have acquired California encephalitis. 

Little known about pathogenicity of most parasite and disease 

organisms in squirrels. Coccidiosis (infection by protozoan 

coccidian in intestinal wall) can cause serious infections that weaken 

squirrels. Ectoparasites, including fleas, are common in squirrels 

(Gurnell 1987). Mortality from plague appears to be uncommon in 

tree squirrels. A Web of Science search for “plague” and “Sciurus” 

yielded no results. A search of “plague” and “tree squirrels” yielded 

only Hudson and others (1971) who mention a case of eastern fox 

squirrels (Sciurus niger) dying in urban Denver in 1968, some of 

which were positive for antigens to plague and/or had fleas that were 

host to Yersinia pestis (bacterium that causes plague). A search on 

“Tamiasciurus” and “plague” returned Smith and others (2010), who 

reported that seroprevalence for Yersinia pestis was high in Allen’s 

and long-eared chipmunks (Tamias senex and T. quadrimaculatus) 

and in pine squirrels (Tamiasciurus douglasii) in northern California 

over 28 years of monitoring, but that all 3 were moderately resistant 

to plague and survived infection.

Bot flies (Cterebra spp.) lay eggs in nests of several types of 

squirrels including Gray Squirrels; the larvae then burrow into skin 

of squirrel, eventually re-emerging and dropping off to pupate.

WNV was first reported in eastern fox squirrels (Sciurus niger) in 

2003 (Kiupul and others 2003). Most mammalian WNV infections 

cause no or low morbidity or mortality, although tree squirrels are 

susceptible to a neurologic disease associated with infection (Padgett 

and others 2008).

Gurnell (1987) indicated that squirrels that are weakened by food 

shortage may develop a parasite or disease load heavy enough to 

cause mortality. Large squirrel mortality events were reported in 

Europe in the early 1900s; coccidiosis was reported to have killed 

one million Eurasian red squirrels in Finland from 1943-1944 

(Lampio 1967 as cited in Gurnell 1987). 

0

5. Competitors Are populations of 

important 

competing species 

expected to 

change?

It has been suggested that the introduction of Abert’s squirrels was 

the cause of the decline of the Arizona gray squirrel in the Santa 

Catalina Mountains (Lange 1960) where the two species co-occur. 

The two do not co-occur in other parts of the CNF (Jones, personal 

communication). Abert’s squirrel expected to be vulnerable to 

climate change, although this would only affect Arizona gray 

squirrel where the two co-occur (Santa Catalina Mountains).

A closely related species to Arizona gray squirrel (and thus a 

potential competitor) is the Chiricahua fox squirrel (S. nayaritensis 

chiricahuae), but it is restricted to the Chiricahua Mountains; 

Arizona gray squirrel not reported to occur in Chiricahua Mountains 

(USFS 2009).

-1
118 USDA Forest Service RMRS-GTR-273. 2012.

156

Literature Cited

Barkalow, F.S., Jr., and R.F. Soots, Jr. 1975. Life span and reproductive longevity of the gray squirrel, 

Sciurus c. carolinensis Gmelin. Journal of Mammalogy 56:522-524.

Best, T.L., and S. Riedel. 1995. Sciurus arizonensis. American Society of Mammalogists. Mammalian 

Species No. 496.

Brown, D.E. 1984. Arizona’s Tree Squirrels. Phoenix: Arizona Game and Fish Department. 114 p.

Frey, J.K., M.T. Hill, B.L. Christman, J.C. Truett, and S.O. MacDonald. 2008. Distribution and habitat of 

the Arizona Gray Squirrel (Sciurus arizonensis) in New Mexico. Southwestern Naturalist 53:248-255.

Gurnell, J. 1987. The Natural History of Squirrels. New York: Facts on File Publications. 201 p.

Halvorson, C.H., and R.M. Engeman. 1983. Survival analysis for a red squirrel population. Journal of 

Mammalogy 64:332-336.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish . 

602 p.

Hudson, B.W., M.I. Goldenberg, J.D.McCluskie, H.E. Larson, C.D. McGuire, A.M. Barnes, and J.D. 

Poland. 1971. Serological and bacteriological investigations of an outbreak of plague in an urban tree 

squirrel population. American Journal of Tropical Medicine and Hygiene 20:255-263.

Jones, Larry. 2010. [Personal communication]. February 17, 2010. Tucson, AZ: U.S. Department of 

Agriculture, Forest Service, Coronado National Forest, Assistant Program Manager for Wildlife, Fish, 

and Rare Plants.

Kiupul, M., H.A. Simmons, S.D. Fitzgerald, A. Wise, J.G. Sikarskie, T.M. Cooley, S.R. Hollamby, and 

R. Maes. 2003. West Nile Virus infection in eastern fox squirrels (Sciurus niger). Veterinary Pathology 

40:703-707.

Koprowski, J.L., and M.C. Corse. 2001. Food habits of the Chiricahua fox squirrel (Sciurus nayaritensis 

chiricahuae). Southwestern Naturalist 46:62-65.

Lange, K.I. 1960. Mammals of the Santa Catalina Mountains, Arizona. American Midland Naturalist 

64:436-458.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Padgett, K.A., W.K. Riesen, N. Kahl-Purcell, Y. Fang, B. Cahoon-Young, R. Carney, N. Anderson, L. 

Zucca, L. Woods, S. Husted, and V.L. Kramer. 2008. West Nile Virus infection in tree squirrels 

(Rodentia: Sciuridae) in California, 2004-2005. Journal of Wildlife Rehabilitation 29:35-39.

Smith, C.R., J.R. Tucker, B.A. Wilson, and J.R. Clover. 2010. Plague studies in California: A review of 

long-term disease activity, flea-host relationships and plague ecology in the coniferous forests of the 

southern Cascades and northern Sierra Nevada mountains. Journal of Vector Ecology 35:1-12.

Steele, M.A., S.L. Halkin, P.D. Smallwood, T.J. McKenna, K. Mitsopoulos, and M. Beam. 2008. Cache 

protection strategies of a scatter-hoarding rodent: Do tree squirrels engage in behavioural deception? 

Animal Behavior 75:705-714.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Zlotin, R.I., and Parmenter, R.R. 2008. Patterns of mast production in pinyon and juniper woodlands 

along a precipitation gradient in central New Mexico (Sevilleta National Wildlife Refuge). Journal of 

Arid Environments 72:1562-1572.
USDA Forest Service RMRS-GTR-273. 2012. 119

157

Habitat: Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change? 

Taxonomic note: The Chiricahua fox squirrel is a sub-species of the 

Mexican fox squirrel (Sciurus nayaritensis) and was considered a 

separate species for a few years (Hoffmeister 1986). This sub-species 

occurs only in the Chiricahua Mountains where it generally occurs at 

elevations of ~5500-6500 ft (Hoffmeister 1986).

Mexican fox squirrels (Sciurus nayaritensis) occur in mixed pine-oak 

forests of the Upper Sonoran and Transition life zones and occupy 

Apache pine-oak forest that is somewhat open (not found in areas 

where trees are very dense); their range includes the Sierra Madre 

Occidental, Mexico, and south as far as southern Jalisco (Best 1995). 

They occur in riparian areas with sycamores, ashes, and walnuts, and 

large evergreen oaks and appear to avoid oak-covered slopes, except 

possibly where acorns are numerous (Best 1995).

High intensity forest fires have been identified as a threat because the 

fires destroy leaf nests and kill young (Kirkpatrick and Mosby 1981 

as cited in Pasch and Koprowski 2005).

Projections of suitable climate for vegetation communities forest wide 

(Chapter 1) predicted declines in suitable climate for all plant 

community types, with the exception of increases of suitable climate 

for semi-desert grassland and small increases in Sonoran desert scrub 

(present in small amounts on the CNF).

We expected that habitat for the Chiricahua fox squirrel will decrease 

as a result of climate change.

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Same as breeding habitat. 2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

Tree squirrels (Sciurus and Tamiasciurus) use nests for rearing young, 

rest, predator avoidance, and cover during inclement weather (Steele 

and Koprowski 2001). Hoffmeister (1986) indicated that “nests are 

said to be much like those of Arizona gray squirrels” and mentioned 

that nests in Pinery Canyon were in oaks and pines, either in leaf nests 

on branches or in holes in trees. Pasch and Koprowski (2005) 

indicated that >95% of Chiricahua fox squirrels use dreys (leaf nests) 

as nest sites and on average used 4.32 ± 3.33 SD dreys (n=20). The 

authors also mentioned that lactating females use tree cavities to rear 

young, then return to dreys following juvenile dispersal. Kneeland 

and others (2005) report nests in Coronado National Monument in 

Emory oaks.

Pasch and Koprowski (2005) stated that maintaining mature trees in 

canyon bottoms (at Coronado National Monument, where the study 

was conducted) is important to prevent low squirrel densities from 

declining, given that the low numbers of young produced per year 

limits the ability to recover quickly from environmental disturbances.

Trees, overall, are expected to decline in abundance.

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

Individuals use nests in trees in winter (Koprowski and Corse 2005). 

See Habitat, Question 3.

1
120 USDA Forest Service RMRS-GTR-273. 2012.

158

Habitat: Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae)

Trait/Quality Question Background info. & explanation of score Points

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

“Survivorship and reproduction of tree squirrels often are positively 

correlated with tree seed production. This dependence on mature, 

seed-producing forests is likely one reason that several species of tree 

squirrels are considered to be threatened or endangered in all or part 

of their ranges...” (Koprowski and Corse 2001).

Pasch and Koprowski (2006b) observed a large increase in homerange size in 2003, the same year of record-low precipitation and 

attributed this correlation to low food availability in the dry year.

Mature trees with high mast yields are expected to decline.

1

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

See Habitat, Question 5. 1

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Although Sciurus and Tamiasciurus spp. generally remain in the same 

area once they are established residents unless there is a food shortage 

(Gurnell 1987), squirrels, in general, are very mobile. Pasch and 

Koprowski (2006b) observed a female Chiricahua fox squirrel that 

regularly traveled >1 km to feed on Arizona walnuts.

-1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Pasch and Koprowski (2006b) indicated that male and female homerange and core-area size varied little from the non-mating season to 

the mating season. However, males move longer distances during the 

mating season, presumably due to searching for receptive females.

0

Physiology: Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Chiricahua fox squirrels are diurnally active. Squirrels may become 

inactive outside of the nest when temperatures are high (Gurnell 

1987). Rainfall does not typically reduce activity unless it is heavy 

(references in Gurnell 1987). Squirrels spend most time foraging in 

trees in summer. Koprowski and Corse (2005) confirmed bimodal 

daily activity periods in summer in Mexican fox squirrels (becoming 

active at sunrise with activity peaking during early morning, followed 

by a lull for 2-3 hours, then another activity peak in late afternoon). In 

winter, high levels of activity occur throughout the day.

Tree squirrels are reported to use evaporative cooling following 

periods of activity when temperatures are high (may lose heat from 

sweat glands in feet; Gurnell 1987). Mexican fox squirrel observed in 

summer resting on a shaded branch with its tail raised, which is 

assumed to be a method of heat dissipation (Koprowski and Corse 

2005).

We assumed that temperatures will remain below physiological 

thresholds most of the time.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou et al. 2006).

0
USDA Forest Service RMRS-GTR-273. 2012. 121

159

Physiology: Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae)

Trait/Quality Question Background info. & explanation of score Points

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality.

See also Physiology, Question 1.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Diurnally active. During summer, tend to have 2 periods of activity—

morning and later afternoon; Gurnell 1987; see confirmation of this 

pattern for this sub-species by Koprowski and Corse [2005] in 

Physiology, Question 1).

We assumed that rise in temperatures will not significantly impact 

morning and evening activity periods.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Squirrels are active year-round; tend to have one main active period 

each day in winter; in northern areas, activity period may be closer to 

the middle of the day than in southern regions (Gurnell 1987). Spend 

time in nests in winter to conserve body heat. In severe weather 

conditions, squirrels may remain in nests for several days (references 

in Gurnell 1987: 55).

When at rest, body temperature declines a few degrees, particularly at 

night when in the nest; this phenomenon has sometimes been referred 

to as heterothermy (Gurnell 1987). Some evidence to suggest that 

squirrels are able to employ a form of adaptive hypothermia (see 

reference in Gurnell 1987: 66).

Chiricahua fox squirrels, like other Holarctic tree squirrels, show 

higher body mass in winter than in summer (Pasch and Koprowski 

2006a).

Although there is not strong evidence that this Chiricahua fox 

squirrels use torpor on a daily basis when temperatures are cold, the 

fact that diurnal squirrels are known to lower body temperature at 

night and when at rest suggests some ability to reduce energy 

requirements. This led to the score of “-1” for this question.

-1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Brown (1984) indicated that the Chiricahua fox squirrel is a forager 

and does not cache food or regularly bury nuts.

Note: Brown (1984) noted that eastern species that are closely related 

do cache; further support for this from Steele and others (2008) for 

eastern gray squirrel (Sciurus carolinensis).

Appears that squirrels do not deposit large amounts of subcutaneous 

fat for insulation, although they may increase fat reserves in other 

parts of the body (Gurnell 1987). Individuals molt twice a year, with 

thicker coat in winter.

1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

None reported. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Gurnell (1987) indicated that gray squirrels may survive in the wild as 

long as 8-10 years (the longevity record for western gray squirrels in 

captivity is 11 years), but that perhaps only 1% of individuals survive 

that long. Of 10 wild eastern gray squirrels (Sciurus carolinensis), the 

shortest survival was 6 years and the longest was 12.5 years 

(Barkalow and Soots 1975); the authors cited references indicating 

1
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Physiology: Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae)

Trait/Quality Question Background info. & explanation of score Points

that this species rarely lives longer than 6 years. A study of red 

squirrels (Tamiasciurus hudsonicus) in Montana found that 67% of 

individuals die before 12 months, with a plateau in survivorship 

occurring at about 36 months and very few individuals surviving past 

7 years (Halvorson and Engeman 1983).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that squirrels have 

insufficient food for breeding, most of the population would not 

survive longer than the periods of limited reproduction.

Phenology: Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

No information found on cues used by Chiricahua fox squirrels. In a 

similar species, the Arizona gray squirrel, (Sciurus arizonensis), onset 

of breeding activity is correlated with flower emergence and 

consumption of flower parts (Best and Reidel 1995). Not clear 

whether Chiricahua fox squirrels follow the same pattern. It is likely 

that food availability of some kind is important and that temperature 

and moisture influence the availability, but since the relationship to 

squirrel breeding is indirect, this question was scored as “0.”

0

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

In this sub-species, males typically became reproductively active in 

January and remained scrotal until May (Pasch and Koprowski 

2006a). Females come into estrus for only 1 day (Pasch and 

Koprowski 2006b). Cahalane (1939) indicated that it is likely that 

parturition occurs in April. Both pregnant and lactating females have 

been observed in different parts of the range of the Mexican fox 

squirrel in July (Best 1995).

As mentioned above (Phenology, Question 1), not clear what cues are 

used for breeding. However, we assumed that changes to the timing 

of precipitation and increases in temperature have the potential to 

alter the timing of food availability, which, in turn, could alter the 

timing of breeding and parturition.

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

We considered food a critical resource and assumed that there is a 

relatively short period of time between food availability and breeding. 

See Phenology, Questions 1 and 2.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

A study by Pasch and Koprowski (2005) from 1994-2003 found that 

young emerged from nests during May-August, “indicating that a 

second reproductive bout did not occur during the late summer or 

early winter season”. Females average 1.62 ± 0.51 SD (range 1-2, 

n=13) offspring per litter. Females come into estrus for only 1 day 

(Pasch and Koprowski 2006b).

1
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Biotic interactions: Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Feeds heavily on tree seeds, mistletoe berries, and hypogeous fungi 

and appears to be dependent on mature trees for food (Koprowski and 

Corse 2001). Chiricahua fox squirrels spent 56% and 72% of its time 

foraging on Arizona cypress nuts in summer and winter, respectively, 

in a study in Chiricahua National Monument (Koprowski and Corse 

2001). Hoffmeister (1986) indicated Mexican fox squirrels are

thought to feed on seeds of pines, Douglas-fir, acorns, and walnuts. 

Reported to consume roots, bulbs, and buds when oak mast or other 

tree seeds are not available (Cahalane 1939).

On the one hand, individuals appear to be able to vary their diets; 

Koprowski and Corse (2001) indicated that the diverse diet is “likely 

a response to spatial and temporal variation in seed crops of trees, 

especially in the drought-prone mountains” in which this species 

occurs. Pasch and Koprowski (2006b) observed a female that 

regularly traveled >1 km to feed on Arizona walnuts. On the other 

hand, individuals depend heavily on trees for food, including seeds, 

and trees are expected to decline.

The score here reflects potential reduction in nut/seed/acorn crops. 

Reduced crops expected as a result of reduced precipitation in the 

short term (Zlotin and Parmenter 2008); in the long term, fewer seeds 

expected as a result of reduced tree abundance. 

1

2. Predators Are important 

predator populations 

expected to change?

According to Pasch and Koprowski (2005), although Chiricahua fox 

squirrels are considered sensitive by the USFS, this status does not 

prohibit hunting of the species. Thus, human hunting can be 

considered a form of predation, although climate change is not 

expected to cause direct increases in human populations.

In Coronado National Monument, Kneeland and others (1995) 

observed interactions between predators and Chiricahua fox squirrels: 

two instances of a gray fox chasing a squirrel, a gray hawk (Buteo 

nitidus) stooping on a squirrel, and 3 Mexican jays (Aphelocoma 

ultramarina) investigating two different squirrel leaf nests in Emory 

oaks (an adult squirrel chased the jays). The authors concluded that 

predation appears to be infrequent. Overall, has a suite of predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

Relationship between squirrels and seed crop considered under Biotic 

Interactions, Question 1. Given that Chiricahua fox squirrels are not 

considered to cache large numbers of acorns/seeds, not clear to what 

extent they act as seed dispersers for tree species.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Squirrels are host to a variety of parasites and diseases (Gurnell 

1987). Diseases include distemper, diphtheria, scab disease,

myxomatosis (myxoma viral infection), and parapoxvirus infection. 

Gray squirrels in the Midwest have acquired California encephalitis. 

Little known about pathogenicity of most parasite and disease 

organisms in squirrels. Coccidiosis (infection by protozoan coccidian 

in intestinal wall) can cause serious infections that weaken squirrels. 

Ectoparasites, including fleas, are common in squirrels (Gurnell 

1987).

Bot flies (Cterebra spp.) lay eggs in nests of several types of 

squirrels, including Gray Squirrels; larvae then burrow into skin of 

squirrel, eventually re-emerging and dropping off to pupate.

Several species of lice and one species of flea identified for the 

Chiricahua fox squirrel (Traum and others 1983 as cited in Best 

1995). Mortality from plague appears to be uncommon in Tree 

Squirrels. A search on Web of Science for “plague” and “Sciurus” 

yielded no results. A search of “plague” and “tree squirrels” yielded 

only Hudson and others (1971), who mentioned a case of eastern fox 

0
124 USDA Forest Service RMRS-GTR-273. 2012.

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Biotic interactions: Chiricahua fox squirrel (Sciurus nayaritensis chiricahuae)

Trait/Quality Question Background info. & explanation of score Points

squirrels (Sciurus niger) dying in urban Denver in 1968, some of 

which tested positive for antigens to plague and/or had fleas that were 

host to Yersinia pestis (bacterium that causes plague). A search on 

“Tamiasciurus” and “plague” returned Smith and others (2010), who 

reported that seroprevalence for Yersinia pestis was high in Allen’s 

and long-eared chipmunks (Tamias senex and T. quadrimaculatus) 

and in pine squirrels (Tamiasciurus douglasii) in northern California 

over 28 years of monitoring, but that all 3 were moderately resistant 

to plague and survived infection.

WNV was first reported in eastern fox squirrels (Sciurus niger) in 

2003 (Kiupul and others 2003). Most mammalian WNV infections 

cause no or low morbidity or mortality, although tree squirrels are 

susceptible to a neurologic disease associated with infection (Padgett 

and others 2008).

Squirrels that are weakened by food shortage may develop a parasite 

or disease load heavy enough to cause mortality (Gurnell 1987). 

Large squirrel mortality events were reported in Europe in the early 

1900s; coccidiosis was reported to have killed one million Eurasian 

red squirrels in Finland in 1943-1944 (Lampio 1967 as cited in 

Gurnell 1987).

Overall, not clear whether there would be significant increase in 

disease mortality in association with climate change.

5. Competitors Are populations of 

important competing 

species expected to 

change?

Neither the Arizona gray squirrel nor the Abert’s squirrel (potential 

competitors) occurs in the Chiricahua Mountains (USFS 2009). No 

information found regarding important competitors.

0

Literature Cited

Barkalow, F.S., Jr., and R.F. Soots, Jr. 1975. Life span and reproductive longevity of the gray squirrel, 

Sciurus c. carolinensis Gmelin. Journal of Mammalogy 56:522-524.

Best, T.L. 1995. Sciurus nayaritensis. American Society of Mammalogists. Mammalian Species 

No. 492: 1-5.

Best, T.L., and S. Riedel. 1995. Sciurus arizonensis. American Society of Mammalogists. Mammalian 

Species No. 496.

Brown, D.E. 1984. Arizona’s Tree Squirrels. Phoenix: Arizona Game and Fish Department. 114 p.

Cahalane, V.H. 1939. Mammals of the Chiricahua Mountains, Cochise County, Arizona. Journal of 

Mammalogy 20:418-440.

Gurnell, J. 1987. The Natural History of Squirrels. New York: Facts on File Publications. 201 p.

Halvorson, C.H., and R.M. Engeman. 1983. Survival analysis for a red squirrel population. Journal of 

Mammalogy 64:332-336.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Hudson, B.W., M.I. Goldenberg, J.D.McCluskie, H.E. Larson, C.D. McGuire, A.M. Barnes, and J.D. 

Poland. 1971. Serological and bacteriological investigations of an outbreak of plague in an urban tree 

squirrel population. American Journal of Tropical Medicine and Hygiene 20:255-263.

Kiupul, M., H.A. Simmons, S.D. Fitzgerald, A. Wise, J.G. Sikarskie, T.M. Cooley, S.R. Hollamby, and 

R. Maes. 2003. West Nile Virus infection in eastern fox squirrels (Sciurus niger). Veterinary Pathology 

40:703-707.

Kneeland, M.C., J.L. Koprowski, and M.C. Corse. 1995. Potential predators of Chiricahua fox squirrels 

(Sciurus nayaritensis chiricahuae). Southwestern Naturalist 40:340-342.
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Koprowski, J.L. 2005. Management and conservation of tree squirrels: The importance of endemism, 

species richness, and forest condition. In: Gottfried, G.J., S. Brooke, L.G. Eskew, C.B. Carleton, comps. 

Connecting mountain islands and desert seas: Biodiversity and management of the Madrean 

Archipelago II. 2004 May 11-15; Tucson, AZ. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station: 245-250.

Koprowski, J.L., and M.C. Corse. 2001. Food habits of the Chiricahua fox squirrel (Sciurus nayaritensis 

chiricahuae). Southwestern Naturalist 46:62-65.

Koprowski, J.L., and M.C. Corse. 2005. Time budgets, activity periods, and behavior of Mexican fox 

squirrels. Journal of Mammalogy 86:947-952.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Padgett, K.A., W.K. Riesen, N. Kahl-Purcell, Y. Fang, B. Cahoon-Young, R. Carney, N. Anderson, L. 

Zucca, L. Woods, S. Husted, and V.L. Kramer. 2008. West Nile Virus infection in tree squirrels 

(Rodentia: Sciuridae) in California, 2004-2005. Journal of Wildlife Rehabilitation 29:35-39.

Pasch, B.S., and J.L. Koprowski. 2005. Correlates of vulnerability in Chiricahua fox squirrels. In:

Gottfried, G.J., B.S. Brooke, L.G. Eskew, C.B. Edminster, comps. Connecting mountain islands and 

desert seas: Biodiversity and management of the Madrean Archipelago II. 2004 May 11-15; Tucson, 

AZ. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky 

Mountain Research Station: 426-428.

Pasch, B.S., and J.L. Koprowski. 2006a. Annual cycles of body mass and reproduction of Chiricahua fox 

squirrels (Sciurus nayaritensis chiricahuae). Southwestern Naturalist 51:531-535.

Pasch, B.S., and J.L. Koprowski. 2006b. Sex differences in space use of Chiricahua fox squirrels. Journal 

of Mammalogy 87:380-386.

Smith, C.R., J.R. Tucker, B.A. Wilson, and J.R. Clover. 2010. Plague studies in California: A review of 

long-term disease activity, flea-host relationships and plague ecology in the coniferous forests of the 

southern Cascades and northern Sierra Nevada mountains. Journal of Vector Ecology 35:1-12.

Steele, M.A., S.L. Halkin, P.D. Smallwood, T.J. McKenna, K. Mitsopoulos, and M. Beam. 2008. Cache 

protection strategies of a scatter-hoarding rodent: Do tree squirrels engage in behavioural deception? 

Animal Behavior 75:705-714.

Steele, M.A., and J.L. Koprowski. 2001. North American Tree Squirrels. Washington, DC: Smithsonian 

Institution Press. 225 p.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Zlotin, R.I., and Parmenter, R.R. 2008. Patterns of mast production in pinyon and juniper woodlands 

along a precipitation gradient in central New Mexico (Sevilleta National Wildlife Refuge). Journal of 

Arid Environments 72:1562-1572.

Habitat: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected 

to change? 

This sub-species occurs only in the Pinaleño Mountains; another subspecies (Tamiasciurus hudsonicus mogollonensis) occurs elsewhere in 

Arizona (Hoffmeister 1986). Mount Graham red squirrels occur only in 

the highest peaks of the Pinaleño Mountains, generally above 9500 ft 

(Brown 1984). One estimate of potential habitat is 9083 ha (based on 

forested area above 2425 m; references in Merrick and others 2007). 

Estimate of population size is <300 (Koprowski and others 2005).

Tamiasciurus is a genus of cold climates; thus, in the Southwest, it 

occurs at high elevations (Brown 1984). Red squirrels in Arizona occur 

in the larger mountain ranges that contain subalpine conifer forests of 

spruce and fir; they are rarely found very far below 7500 ft and more 

2
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Habitat: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

often are above 2530 m (8300 ft; Brown 1984). Hoffmeister (1986) 

indicated that red squirrels occur where spruce or mixture of spruce and 

Douglas-fir exist and are rarely found in ponderosa pine or Douglas-fir 

forests. In the Pinaleño Mountains, Mount Graham red squirrels

formerly lived in the fir zone; no large stands of spruce exist in this 

mountain range (Hoffmeister 1986). Brown (1984) noted that red 

squirrels in Arizona range from sub-alpine forest to as low as mixedconifer forest (occasionally in ponderosa pine forest) and that they 

require cold, moist, shaded conditions. Areas that are most often used 

are subalpine forests of Englemann spruce and subalpine fir, as well as 

Douglas-fir and other species (e.g., white fir, southwestern white pine, 

and ponderosa pine). Stands of blue spruce and southwestern white pine 

are also frequented by red squirrels.

Corkbark fir is an important component of nesting habitat in the mixed 

conifer transition zone on Mount Graham (Merrick and others 2007).

Koprowski and others (2005) documented a significant decline in this 

sub-species over 1994-2002 in spruce fir forest, with less of a decline in 

mixed-conifer forest. Over the same time period, significant outbreaks 

of several conifer pests resulted in significant damage to trees, more so 

in spruce-fir than in mixed conifer. Pests included a geometrid moth 

(Nepytia janetae; consumes spruce and corkbark fir), a spruce beetle 

(Dendroctonus rufipennis Kirby; attacks spruce), western balsam bark 

beetle (Dryocoetes confusus Swaine; consumes corkbark fir), and a 

spruce aphid (Elatobium abietinum Walker; attacks Englemann spruce).

Forest fires (e.g., Clark Peak Fire and Nuttall Complex Fire) and 

vegetation mortality from bark beetles and spruce aphids have resulted 

in habitat area reductions (references in Merrick and others 2007). 

Koprowski and others (2006) documented that survival of radiocollared individuals was lower in areas that burned in the Nuttall 

Complex Fire (in 2004) relative to unburned areas.

Projections of suitable climate for vegetation communities forest wide 

(Chapter 1) predicted declines in suitable climate for all plant

community types, with the exception of increases of suitable climate for 

semi-desert grassland and small increases in Sonoran desert scrub 

(present in small amounts on the CNF).

We expected that habitat will decrease as a result of climate change.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to 

change?

Same as breeding habitat. 2

3. Habitat 

components: 

breeding

Are specific 

habitat 

components 

required for 

breeding expected 

to change? 

Tree squirrels (Sciurus and Tamiasciurus spp.) use nests for rearing 

young, rest, predator avoidance, and cover during inclement weather 

(Steel and Koprowski 2001). Red squirrel nests are made by both sexes 

in tree cavities, or bolus nests are constructed from conifer twigs, grass, 

leaves, and moss (Brown 1984). Most squirrels have more than one nest 

(Vahle 1978 as cited in Brown 1984).

Brown (1984) indicated that red squirrels (like all tree squirrels) prefer 

areas with large, old trees that offer squirrels the best cone crops and 

easy movement through the connected canopy. Even-aged and open 

forests with widely spaced trees are low-quality habitat.

1
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165

Habitat: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

Merrick and others (2007) found that 3 types of nests were used in the 

~100-ha study area: cavity nests, dreys, and occasionally log or ground 

nests. Nest sites were strongly influenced by stand composition; in 

particular, important components were: density of corkbark fir, large 

trees, and decaying logs. Cavity-containing trees and large snags were 

also important. Cavities were used twice as much as dreys in this study 

area. Dreys were primarily in Englemann spruce and corkbark fir; 

cavity nests were primarily in aspen and corkbark fir. Mount Graham 

red squirrels chose nest sites that had a higher canopy cover and more 

corkbark fir, decayed logs, and living trees compared to random sites. 

Cavity trees were on average 1.6 times larger than drey trees or random 

focal trees. Drey nest trees had almost twice the area of living crown 

relative to cavity nest trees.

A cool microclimate at middens, typically provided by forest structure, 

is required for cone preservation (Leonard and Koprowski 2009).

Trees, overall, are expected to decline in abundance.

4. Habitat 

components: 

non-breeding

Are specific 

habitat 

components 

required for 

survival during 

non-breeding 

periods expected 

to change?

Uses nests in trees winter (Brown 1984). See Habitat, Question 3. 1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated

with better 

reproductive 

success expected 

to change? 

“Survivorship and reproduction of tree squirrels often are positively 

correlated with tree seed production. This dependence on mature, seedproducing forests is likely one reason that several species of tree 

squirrels are considered to be threatened or endangered in all or part of 

their ranges....” (Koprowski and Corse 2001). In various habitat types, 

mature forest stands are considered to have the highest densities of red 

squirrels and are thus considered the highest-quality habitat (Layne 

1954 as cited in Kemp and Kemp 1970). Even-aged and open forests 

with widely-spaced trees are low-quality habitat (Brown 1984).

Mature trees with high mast yields are expected to decline.

1

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better 

survival expected 

to change? 

See Habitat, Question 6. 1

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Although Sciurus and Tamiasciurus spp. generally remain in the same 

area, once they are established residents (unless there is a food shortage) 

(Gurnell 1987), their dependence on middens makes them site faithful. 

However, squirrels in general are very mobile. Juvenile red squirrels in 

Canada dispersed up to ~1.6 km from the natal area (Kemp and Keith 

1970), although some offspring may establish territories closer to their 

natal area (Brown 1984). Therefore, we considered the Mount Graham 

red squirrel as capable of colonizing new areas where appropriate 

habitat exists.

-1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Red squirrels defend territories year-around (Brown 1984). Movement 

out of year-round areas appears to be rare. For example, on the North 

Kaibab Plateau in 1971, red squirrel populations at high elevations 

moved into an area where there was a large cone crop of ponderosa pine 

seeds; squirrels from higher elevations descended to the bumper crop 

area, established territories, and collected and stored seeds. They moved 

back upslope after being forced to use other food sources.

0
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Physiology: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Red squirrels are diurnally active (Gurnell 1987), although 

occasionally they may be active at night (Layne 1954 as cited in 

Steele 1998). In spring and summer, activity peaks occur in morning 

and afternoon; in fall, active throughout the day; and in winter, 

usually one activity peak in the middle of the day (references in 

Steele 1998). Red squirrels may become less active during periods of 

heavy rains, snow, and high winds (references in Steele 1998).

Squirrels may become inactive outside of the nest when temperatures 

are high (Gurnell 1987). Clarkson and Ferguson (1969) reported a 

negative relationship between activity and temperature between 

10-35 °C in laboratory conditions. Tree squirrels are reported to use 

evaporative cooling following periods of activity when temperatures 

are high (may lose heat from sweat glands in feet; Gurnell 1987).

We assumed that temperatures will remain below physiological 

thresholds most of the time.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity 

of heat waves will effect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality.

See also Physiology, Question 1.

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Individuals are diurnally active. In spring and summer, activity peaks 

occur in morning and afternoon; in fall, active throughout the day; 

and in winter, usually one activity peak in the middle of the day 

(references in Steele 1998).

We assumed that rise in temperatures will not significantly impact 

morning and evening activity periods, when temperatures tend to be 

cooler than mid-day.

See also Physiology, Question 1.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Squirrels are active year-round. When at rest, the body temperature of 

squirrels declines a few degrees, particularly at night when in the 

nest; this phenomenon has sometimes been referred to as 

heterothermy (Gurnell 1987). Some evidence to suggest that squirrels 

are able to employ a form of adaptive hypothermia (see reference in 

Gurnell 1987: 66). In fact, Pauls (1979) measured body temperature 

of two red squirrels in the laboratory and found that they lowered 

body temperature while in the nest, as well as when active 

underground, which was considered to potentially result in a 

significant energy savings. The fact that red squirrels tend to lower 

body temperature at night and when at rest suggests some ability to 

reduce energy requirements. This led to the score of “-1” for this 

question.

-1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Tamiasciurus is the only genus of North America tree squirrels that 

stores food in any important amount (Brown 1984). Caches are 

comprised of mounds of unopened cones buried in cone scale debris 

below a feeding perch; the scale debris is called a midden. They are 

often near one or more large cone-bearing trees and at the base of a 

tree of large-diameter or a downed log (Brown 1984). Hollow trees, 

against stumps, and underground dens and crevices are also used for 

-1
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Physiology: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

cone storage. The primary cache is strongly defended. Moisture in the 

cache keeps the cones from opening, so locations must be in shaded 

areas, depressions, or north-facing locations that stay moist. In 

Arizona, middens are often placed under ponderosa pine (Hoffmeister 

1986).

Mount Graham red squirrel female body mass did not increase in 

winter (Koprowski 2005).

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

None reported. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Not all female red squirrels breed each year (Brown 1984). In a 

related species, it was observed that in years of low food, most 

chickarees (Tamiasciurus douglasii) did not breed in spring and none 

bred in fall (Smith 1968 as cited in Brown 1984). In Montana, 

Halvorson and Engeman (1983) found that most mortality (67%) 

occurred before 12 months of age, with few red squirrel individuals 

surviving more than 7 years. The median longevity for males was 3 

months and 6 months for females.

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that squirrels have 

insufficient food for breeding, most of the population would not 

survive longer than the periods of limited reproduction.

1

Phenology: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Little information on cues that trigger breeding. Steele (1998) noted 

that compared to ground squirrels, red squirrel females are 

asynchronous in the timing of estrus (can vary up to 1-2 months).

Individuals are often consistent in estrus timing among years, 

however. Becker (1993) concluded that timing of estrus in red 

squirrels (T. hudsonicus) appears to result from an interaction 

between an endogenous circannual reproductive cycle (such as day 

length) and net energy gain (e.g., food availability). The consumption 

of certain high-quality food may be involved (Steele 1998). Kemp 

and Keith (1970) indicated that red squirrels may come into breeding 

condition in response to feeding on spruce flower buds.

It is likely that food availability of some kind is important, and that 

temperature and moisture influence the availability of food, but since 

the relationship to squirrel breeding would be indirect, this question 

was scored as “0.”

0

2. Event timing Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

As previously mentioned (Phenology, Question 1), to what extent 

environmental factors trigger breeding is unclear, but it appears likely 

that food availability plays some key role. The timing of precipitation 

and increases in temperature can alter the timing of food availability. 

1
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Phenology: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

Consider food a critical resource and assumed relatively short period 

of time between food availability and breeding. See Phenology, 

Questions 1 and 2.

-1

4. Resilience to 

timing 

mismatches 

during breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Brown (1984) reported that red squirrels typically have only one litter 

per year but Layne (1954) reported two litters in one year in New 

York. Smith (1968) also cited that females come into estrus for only 

one day per year (usually in late March or early April [Brown 1984]) 

(although females are not synchronous), gestation is 35 days, and 

young remain in the nest for 45 days or more. After leaving the nest, 

they remain with the adult female for another 2-3 weeks. Litter size is 

generally 2-4.

Hoffmeister (1986) indicated that red squirrels in Arizona (including 

in the Pinaleño Mountains) may produce two litters (one in spring and 

a second in summer). However, Koprowski (2005) cited references 

indicating that red squirrels typically have a single reproductive 

season in late spring or early summer. Steele (1998) cited references 

indicating that, particularly in the western and northwestern portion of 

their range, red squirrels typically produce only 1 litter per year.

1

Biotic interactions: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

From Brown (1984): Conifer seeds are an important component of the 

diet of red squirrels; important species in Arizona include white fir, 

subalpine fir, blue spruce, Engelmann spruce, white pine, ponderosa 

pine, and Douglas-fir. In late winter, terminal buds of conifers are 

eaten in addition to seeds from stored cones. Terminal buds can be an 

important component of the diet in a severe winter or if cone stores 

are insufficient. Inner bark and cambium are also consumed. Male 

cones, available in the early spring, are not stored nor defended. In 

summer, branches containing female cones are chewed off; the seeds 

are either eaten or the cones are stored. Other food includes false 

truffles and other fungi (sometimes stored), nestling birds, insects, 

and carrion.

Cones are dug out of caches for harvesting of seeds. In winter, 

squirrels keep a path open to the cache via paths under the snow. See 

Physiology, Question 6 for more information on caches.

Epigeous and hypogeous mycorrhizal fungi can be important to red 

squirrels in summer and other periods of food shortage (references in 

Steele 1998).

Although it would appear that Mount Graham red squirrels vary their

diet, it depends heavily on trees for food, including seeds. Trees, in 

general, are expected to decline. The score here reflects potential for 

reduction in seed crops.

1

2. Predators Are important 

predator populations 

expected to change?

Goshawks are considered a predator of red squirrels; pine martens do 

not occur in Arizona (Brown 1984). Schauffert and others (2002) 

observed five predation attempts in ~41,000 hours of field time over 

7 years; predators included Mexican spotted owl, bobcat, and 

northern goshawk. Other potential predators included Cooper’s 

0
USDA Forest Service RMRS-GTR-273. 2012. 131

169

Biotic interactions: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

hawks, sharp-shinned hawks, greathorned owls, and gray foxes, all of 

which are reported as known predators by Steele (1998).

Overall, it appears that Mount Graham red squirrels have a suite of 

predators. Furthermore, Schauffert and others (2002) indicated that 

their low number of observations suggest that successful predation 

attempts appear to be low.

3. Symbionts Are populations of 

symbiotic species 

expected to change?

Relationship between squirrels and seed crop considered under Biotic 

Interactions, Question 1.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

From Yahner (2003): A variety of endoparasites, ectoparasite, and 

diseases have been reported for red squirrels, including, sucking lice, 

nematodes, tapeworms, fleas, ticks, chiggers, and mites, and they are

known to be susceptible to sarcocysts, botfly, tularemia, and various 

other infections, some viral.

It appears that mortality from plague is uncommon in tree squirrels. 

Smith and others (2010) reported that seroprevalence for Yersinia 

pestis (bacterium that causes plague) was high in Allen’s and longeared chipmunks (Tamias senex and T. quadrimaculatus) and in the 

pine squirrel (Tamiasciurus douglasii) in northern California over 28 

years of monitoring, but that all 3 were moderately resistant to plague 

and survived infection. A search on Web of Science for “plague” and 

“Tamiasciurus” yielded only this citation (Smith and others 2010), 

and a search on Web of Science for “plague” and “Sciurus” yielded 

no results. A search of “plague” and “tree squirrels” yielded only 

Hudson and others (1971) who mentioned a case of eastern fox 

squirrels dying in urban Denver in 1968, some of which tested 

positive for antigens to plague and/or had fleas that were host to 

Yersinia pestis.

Overall, not clear whether there would be a significant increase in 

disease mortality in association with climate change.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Steele (1998) indicated that red squirrels experience little, if any, 

competition with tree and ground squirrels and chipmunks due to 

differences in habitats and food resources from other species.

However, discussion exists regarding the impact on Abert’s squirrel 

on this sub-species of red squirrel. Abert’s squirrels, which were 

introduced into the Pinaleño Mountains, may have contributed to the 

decline of the Mount Graham red squirrel (Hoffmeister 1986). Brown 

(1984) cited Layne (1954) that red squirrels in New York were not 

able to prevent pilfering of their caches by eastern gray squirrels, 

leading to exclusion by the gray squirrels. Abert’s squirrels are 

considered to have the potential to reduce population viability of the 

Mount Graham red squirrel by reducing food resources (see 

references in Rushton and others 2006); in some areas, Abert’s 

squirrels have been reported to reduce cone crops by as much as 74%.

Using remote cameras at 9 occupied Mount Graham red squirrel 

middens, 7 unoccupied middens, and 7 random sites, Edelman and 

others (2005) found that Abert’s squirrels were recorded only at 

unoccupied middens. The authors concluded that kleptoparasitism of 

red squirrel middens by Abert’s squirrel appeared to be uncommon, 

possibly due to territorial defense. Edelman and others (2009) 

concluded, based on work in mixed conifer habitat, that competition 

for nest sites appeared unlikely given that Abert’s squirrels used dreys 

mostly, whereas red squirrels used mostly cavity nests. Abert’s 

squirrel nests were in areas that were more open and contained greater 

species diversity, whereas red squirrel nest sites were in more densely 

-1
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Biotic interactions: Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Trait/Quality Question Background info. & explanation of score Points

forested areas dominated by corkbark fir.

Overall, unclear to what extent Abert’s squirrel directly impacts 

numbers of Mount Graham red squirrel, but the potential appears to 

exist.

Abert’s squirrels were identified as being vulnerable to climate 

change as part of this assessment.

Literature Cited

Becker, C.D. 1993. Environmental cues of estrus in the North American red squirrel (Tamiasciurus 

hudsonicus Bangs). Canadian Journal of Zoology 71:1326-1333.

Brown, D.E. 1984. Arizona’s Tree Squirrels. Phoenix: Arizona Game and Fish Department. 114 p.

Clarkson, D.P., and J.H. Ferguson. 1969. Effect of temperature upon activity in the red squirrel. 

American Zoologist 9:1110.

Edelman, A.J., J.L. Koprowski, and S.R. Bertelsen. 2009. Potential for nest site competition between 

native and exotic tree squirrels. Journal of Mammalogy 90:167-174.

Edelman, A.J., J.L Koprowski, and J.L Edelman. 2005. Kleptoparasitic behavior and species richness at 

Mt. Graham red squirrel middens. In: Gottfried, G.J., S. Brooke, L.G. Eskew, C.B. Carleton, comps. 

Connecting mountain islands and desert seas: Biodiversity and management of the Madrean 

Archipelago II. 2004 May 11-15; Tucson, AZ. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station: 395-398.

Gurnell, J. 1987. The Natural History of Squirrels. New York: Facts on File Publications. 201 p.

Halvorson, C.H., and R.M. Engeman. 1983. Survival analysis for a red squirrel population. Journal of 

Mammalogy 64:332-336.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Kemp, G.A., and L.B. Keith. 1970. Dynamics and regulation of red squirrel (Tamiasciurus hudsonicus) 

populations. Ecology 51:763-779.

Koprowski, J.L., K.M. Leonard, C.A. Zugmeyer, and J.L. Jolley. 2006. Direct effects of fire on

endangered Mount Graham red squirrels. Southwestern Naturalist 51:59-63.

Koprowski, J.L. 2005. Management and conservation of tree squirrels: The importance of endemism, 

species richness, and forest condition. In: Gottfried, G.J., S. Brooke, L.G. Eskew, C.B. Carleton, comps. 

Connecting mountain islands and desert seas: Biodiversity and management of the Madrean 

Archipelago II. 2004 May 11-15; Tucson, AZ. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station: 245-250.

Koprowski, J.L., M.I. Alanen, and A.M. Lynch. 2005. Nowhere to run and nowhere to hide: Response of 

endemic Mt. Graham red squirrels to catastrophic forest damage. Biological Conservation 126:491-498.

Koprowski, J.L., and M.C. Corse. 2001. Food habits of the Chiricahua fox squirrel (Sciurus nayaritensis 

chiricahuae). Southwestern Naturalist 46:62-65.

Gurnell, J. 1987. The Natural History of Squirrels. New York: Facts on File Publications. 201 p.

Hudson, B.W., M.I. Goldenberg, J.D. McCluskie, H.E. Larson, C.D. McGuire, A.M. Barnes, and J.D. 

Poland. 1971. Serological and bacteriological investigations of an outbreak of plague in an urban tree 

squirrel population. American Journal of Tropical Medicine and Hygiene 20:255-263.

Leonard, K.M., and J.L. Koprowski. 2009. A comparison of habitat use and demography of red squirrels 

at the southern edge of their range. American Midland Naturalist 162:125-138.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Merrick, M.J., S.R. Bertelsen, and J.L. Koprowski. 2007. Characteristics of Mount Graham red squirrel 

nest sites in a mixed conifer forest. Journal of Wildlife Management 71:1958-1963.
USDA Forest Service RMRS-GTR-273. 2012. 133

171

Pauls, R.W. 1979. Body temperature dynamics of the red squirrel (Tamiasciurus hudsonicus): 

Adaptations for energy conservation. Canadian Journal of Zoology 57:1349-1354.

Schauffert, C.A., J.L Koprowski, V.L. Greer, M.I. Alanen, K.A. Hutton, and P.J. Young. 2002. 

Interactions between predators and Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis). 

Southwestern Naturalist 47:498-501.

Smith, C.R., J.R. Tucker, B.A. Wilson, and J.R. Clover. 2010. Plague studies in California: A review of 

long-term disease activity, flea-host relationships and plague ecology in the coniferous forests of the 

southern Cascades and northern Sierra Nevada mountains. Journal of Vector Ecology 35:1-12.

Steele, M.A. 1998. Tamiasciurus hudsonicus. American Society of Mammalogists. Mammalian Species 

No. 586: 1-9.

Steele, M.A., and J.L. Koprowski. 2001. North American Tree Squirrels. Washington, DC: Smithsonian 

Institution Press. 225 p.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Yahner, R.H. 2003. Pine Squirrels. In: Feldhamer, G.C., B.C. Thompson, and J.A. Chapman, eds. Wild 

mammals of North America: Biology, management, and conservation. Baltimore, MD: Johns Hopkins 

University Press:268-275.

Habitat: Mesquite mouse (Peromyscus merriami)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change? 

Taxonomic note: This species is closely related to, and formerly 

included in, Peromyscus eremicus. The two can be very difficult to 

distinguish morphologically (Hoffmeister and Lee 1963), although 

not genetically, and some museum specimens may have been 

incorrectly identified (Kingsley 2006).

In Arizona, this species occurs in the southern-middle portion of the 

state; range extends into Mexico (Hoffmeister 1986). The majority of 

known records for this species in Arizona are in Pima County along 

the Santa Cruz River and its tributaries (Kingsley 2006).

Is almost entirely restricted to mesquite forests (bosques: Hoffmeister 

1986). Hoffmeister (1986) indicated that it occurs in heavy, forest-like 

stands of mesquite (such stands were more abundant in the past). 

Kingsley (2006) found in Pima County, individuals occur not just in 

large velvet mesquite (Prosopis vetulina) bosques, but “in a wider 

variety of mesquite-dominated communities on floodplain soils.” This 

species was not found in isolated patches of mesquite surrounded by 

urban development, narrow rocky washes with few mesquites, 

mesquite-invaded grassland, or upland vegetation.

This species occurs, or potential habitat exists, on the following 

EMAs: Tumacacori, Santa Rita, Huachuca, and Santa Catalina (Jones, 

personal communication). Projections of suitable climate for 

vegetation communities (Chapter 1) predicted declines in suitable 

climate for plains grassland, Madrean forest and woodland, and 

Madrean conifer forest, and increases of suitable climate for semidesert grassland. Sonoran desert scrub is also predicted to increase, to 

a small degree, on the Santa Catalina EMA.

Velvet mesquite is a facultative riparian species native to the Sonoran 

biotic region (Stromberg and others 1993). The wettest habitats in 

which this species occurs are riverine floodplains with perennially 

available groundwater. Riparian communities are expected to 

decrease in area.

2
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Habitat: Mesquite mouse (Peromyscus merriami)

Trait/Quality Question Background info. & explanation of score Points

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to change?

See Habitat, Question 1. 2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

No information found on this topic. A similar species, P. eremicus, 

often lives in abandoned burrows of other mammals or in part of a 

wood rat house (Hoffmeister 1986). 

0

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

non-breeding 

periods expected to 

change?

No information found on this topic. 0

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

No information found on this topic. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change?

No information found on this topic. 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Home ranges of a similar species, P. eremicus, averaged 0.3 ha 

(Ogston 1974 as cited in Veal and Caire 1979). Reports of distances 

travelled by other species in the genus vary. Peromyscus maniculatus 

has been observed to move 50-1320 m, which is considered “long 

distance” (Rehmeier and others 2004) and >3 km (Murie and Murie 

1931 as cited in Maier 2002). Peromyscus leucopus has been reported 

to have moved >14 km (Maier 2002).

Overall, we considered Peromyscus spp. to be relatively poor 

dispersers.

1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

No information to suggest that this species undertakes migratory 

movements.

0
USDA Forest Service RMRS-GTR-273. 2012. 135

173

Physiology: Mesquite mouse (Peromyscus merriami)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Peromyscus spp. are nocturnally active (Burt and Grossenheider 

1976), so they avoid activity during the hottest part of the day. We 

assumed that this species estivates, as does P. eremicus (see 

Physiology, Question 5), so assumed it can respond to higher 

temperatures and lower moisture availability.

We assumed that temperatures will remain below physiological 

thresholds most of the time. 

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality for this 

species.

See also Physiology, Question 1.

0

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Peromyscus spp. are nocturnally active (Burt and Grossenheider 

1976). The closely related P. eremicus was found to be most active on 

moonlit nights, in comparison to P. californicus, which was most 

active on moonless nights (Owings and Lockard 1971 as cited in Veal 

and Caire 1979).

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

In the closely related P. eremicus, torpor mostly occurs on a daily 

basis (active at night, torpid during the day) and can be used any time 

energy supplies are limited (references in Veal and Caire 1979).

Torpor occurred at any ambient temperature below 30 °C (Macmillen 

1965). Winter torpor appears to result only from food restriction, as 

compared to summer torpor (estivation), which results from food 

limitation or a negative water balance; estivation can last several 

weeks (Macmillen 1965).

We assumed that the above biology applies to P. merriami as well.

-1

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

The closely-related P. eremicus was found to exhibit the highest level 

of food hoarding among five Peromyscus taxa; the amount of 

hoarding was not apparently related to ambient temperature or 

photoperiod (Barry 1976 as cited in Veal and Caire 1979). We 

assumed that hoarding behavior also occurs in P. merriami.

-1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

None reported. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

In the closely related P. eremicus, the average age at first conception 

is 10 months with, on average, 50 days between litters (Davis and 

Davis 1979 as cited in Veal and Caire 1979). “Suspect that mesquite 

mice are born in nearly every month, much as with P. eremicus” 

(Hoffmeister 1986). Such a high reproductive rate suggests that this 

species is relatively short-lived. P. leucopus is said to have a complete 

population turn-over each year from mortality (Snyder 1956 in 

1
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Physiology: Mesquite mouse (Peromyscus merriami)

Trait/Quality Question Background info. & explanation of score Points

Lackey and others 1985), so we assumed a similar situation for P. 

merriami.

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions eliminate breeding (e.g., insufficient food), most of the 

population would not survive longer than the periods of limited 

reproduction.

Phenology: Mesquite mouse (Peromyscus merriami)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities

related to fecundity 

or survival? 

 “Suspect that mesquite mice are born in nearly every month, much as 

with P. eremicus...” (Hoffmeister 1986). If this is the case, it appears 

that reproduction is not related to specific cues.

0

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

No apparent connection to discrete events (see Phenology, 

Question 1).

0

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

Reproduction occurs year-round (see Phenology, Question 1). 

Resources do not appear to be particularly limited in general.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

“Suspect that mesquite mice are born in nearly every month, much as 

with P. eremicus...” Hoffmeister (1986). The closely related P. 

eremicus appears to curtail reproduction in hot dry periods in summer 

(Moor 1968 as cited in Veal and Caire 1979).

-1

Biotic interactions: Mesquite mouse (Peromyscus merriami)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Little information on this species. In the closely related P. eremicus

in the California coastal sage scrub community, the diet consisted 

primarily of fruit and flowers of shrubs (Meserve 1976 as cited in 

Veal and Caire 1979). Also reported to consume seeds, insects, and 

green vegetation based on seasonal availability (references in Veal 

and Caire 1979). Other studies of P. eremicus reported that diet 

consists of seeds and desert annuals, in addition to mesquite beans, 

hackberry, nutlets, insects, and green vegetation; some studies 

reported insects as being an important part of the diet (references in 

Veal and Caire 1979).

0
USDA Forest Service RMRS-GTR-273. 2012. 137

175

Biotic interactions: Mesquite mouse (Peromyscus merriami)

Trait/Quality Question Background info. & explanation of score Points

Assuming that P. merriami has a similar diet breadth to P. eremicus, 

species consumes a variety of prey.

2. Predators Are important 

predator populations 

expected to change?

We assumed that this species is preyed upon by a variety of 

predators. In the closely related P. eremicus, documented predation 

by barn owls in Sonora, Mexico, screech owl, and king snake 

(references in Veal and Caire 1979).

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information to suggest important symbiotic relationships exist. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

P. eremicus is host to a variety of parasites, including the nematode 

Gongylonema peromysci, and several species of mites, chiggers, 

ticks, fleas, and biting lice; in Mexico, documented to have bot fly 

larvae (Cuterebra spp.) under the skin (references in Veal and Caire 

1979). Bot fly infestation has not been observed to have detectable 

effects on several measured host characteristics, including body mass, 

length and mass of testes, fecundity, and tolerance to cold stress (see 

references in Nichols 1994). Antibodies to Sin Nombre Virus, a type 

of hantavirus, were identified in Peromyscus eremicus in southeastern 

Arizona (Kuenzi and others 1999), but no indication that there has 

been widespread mortality due to this.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Little information. An experiment where three species of Dipodomys

were excluded resulted in the authors concluding that Peromyscus 

eremicus and the 3 other species of small mammals were in direct 

competition (Heske and others1994). This relationship may hold for 

P. merriami. The range of Dipodomys ordii and D. merriami overlap 

with that of Peromyscus merriami, and at least some of their habitat 

affinities seem similar.

Possible that other species compete with P. merriami as well, so 

likely to have a variety of competitive relationships.

0

Literature Cited

Burt, W.H., and R.P. Grossenheider. 1976. A Field Guide to the Mammals of North America North of 

Mexico (3rd ed.). Boston: Houghton Mifflin Company.

Heske, E.J., J.H. Brown, and S. Mistry. 1994. Long-term experimental study of a Chihuahuan Desert 

rodent community: 13 years of competition. Ecology 75:438-445.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Hoffmeister, D.F., and M. R. Lee. 1963. The status of the sibling species Peromyscus merriami and 

Peromyscus eremicus. Journal of Mammalogy 44:201-213.

Jones, Larry. 2010. [Personal communication]. February 17, 2010. Tucson, AZ: U.S. Department of 

Agriculture, Forest Service, Coronado National Forest, Assistant Program Manager for Wildlife, Fish, 

and Rare Plants.

Jones, Larry. 2011. [Personal communication]. May 18, 2011. Tucson, AZ: U.S. Department of 

Agriculture, Forest Service, Coronado National Forest, Assistant Program Manager for Wildlife, Fish, 

and Rare Plants.

Kingsley, K.J. 2006. Evaluation of mesquite mouse (Persomyscus merriami) status in Pima County, 

Arizona. Prepared for: Pima County Regional Flood Control Distict, Water Resources Division, Public 

Works Center, Tucson, AZ. Arizona Game and Fish Department, Heritage Grant Program #I05001. 

Available: http://www.pima.gov/cmo/sdcp/reports/d30/EvaluationMesquite%20MouseStatus.pdf.
138 USDA Forest Service RMRS-GTR-273. 2012.

176

Kuenzi, A.J., M.L. Morrison, D.E. Swann, P.C. Hardy, and G.T. Downard. 1999. A longitudinal sutdy of 

Sin Nombre Virus prevalence in rodents, southwestern Arizona. Emerging Infectious Diseases 5:113-

117.

Lackey, J.A., D.G. Huckaby, and B. G. Ormiston. 1985. Peromyscus leucopus. American Society of 

Mammalogists. Mammalian Species No. 247.

Macmillen, R.E. 1965. Aestivation in the cactus mouse, Peromyscus eremicus. Comparative 

Biochemistry and Physiology 16:247-248.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Maier, T.J. 2002. Long-distance movements by female white-footed mice, Peromyscus leucopus, in 

extensive mixed-wood forest. Canadian Field-Naturalist 116:108-111.

Nichols, L.B. 1994. The effect of bot fly (Cuterebra) infestation on cold-night trap mortality in cactus 

mice (Peromyscus eremicus). Southwestern Naturalist 39:383-385.

Rehmeier, R.L., G.A. Kaufman, and D.W. Kaufman. 2004. Long-distance movements of the deer mouse 

in tallgrass prairie. Journal of Mammalogy 85:562-568.

Stromberg, J.C., S.D. Wilkins, and J.A. Tress. 1993. Vegetation-hydrology models: Implications for 

management of Prosopis velutina (velvet mesquite) riparian ecosystems. Ecological Applications 

3:307-314.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Veal, R., and W. Caire. 1979. Peromyscus eremicus. American Society of Mammalogists. Mammalian Species No. 118.

Habitat: White-bellied long-tailed vole (Microtus longicaudus leucophaeus)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change? 

This sub-species occurs in the Pinaleño Mountains (Hoffmeister 

1986). Note that the long-tailed vole has a large range throughout 

most of the western United States and Canada to eastern Alaska, with 

14 sub-species, as identified by Hall 1981 (as cited in Smolen and 

Keller 1987). Hoffmeister (1986) identified 4 sub-species as 

occurring in Arizona. Across its range, M. longicaudus occurs in a 

variety of habitats ranging from forests, forest-meadow ecotones, and 

riparian areas, to grassy or sagebrush areas (see references in Smolen 

and Keller 1987).

In Arizona, long-tailed voles occur in meadows, grassy valleys, 

grassy clearings in forests, sagebrush flats, and rocky slopes near or 

in coniferous forest (Hoffmeister 1986). In the Pinaleño Mountains, it 

was reported that this sub-species could be found “in any of the 

meadows or flats...above 8000 feet, where the grass is tall and thick 

and becomes heavily saturated with dew.... Frequently, there was 

standing water among the grass where they lived.” (Hoffmeister 1956 

as cited in Hoffmeister 1986). Hoffmeister (1986) also indicated that 

in Arizona, where long-tailed voles occur in the absence of Microtus 

montanus, they may occupy more mesic areas than elsewhere in the 

Southwest.

Spicer (1985) indicated that the sub-species occurs in the Pinaleño 

Mountains from 1829-3269 m and in a variety of grassy habitats 

ranging from wet to dry. This includes areas containing “meadows, 

cienegas, and creeks; narrows strips along creeks, openings in 

coniferous forest and along roadsides; occasionally steep slopes with 

2
USDA Forest Service RMRS-GTR-273. 2012. 139 177

Habitat: White-bellied long-tailed vole (Microtus longicaudus leucophaeus)

Trait/Quality Question Background info. & explanation of score Points

openings of bunchgrasses...although such habitats are found in 

heavily forested areas above 2930 m...most occur between 2650 m 

and 2930 m on the relatively gently rolling semi-plateau of the crest 

of the range.” The author indicated it is most abundant in areas with 

the thickest grass and grass-like vegetation in meadows and near 

water.

Van Horne (1982) reported that long-tailed voles are atypical voles in 

that they tend to occupy shrubby or forest edge areas rather than 

primarily in grasslands, except in high elevations where they may 

occupy meadows. The highest populations observed consistently in 

coastal coniferous forest in Alaska were on 7-10 year-old clear cut 

areas; densities were lower in mature timber stands than in 

successional stands (Van Horne 1982). Pugh and others (2003) 

indicated that for voles “...optimal habitat contains stable amounts of 

moisture and moisture-laden plant food, influenced by permanent 

water sources including the water table or by elevation and 

microclimate effects of geomorphology.”

For the Pinaleño EMA, projections of suitable climate for vegetation 

communities (Chapter 1) predicted declines in suitable climate for 

Chihuahua desert scrub, Madrean forest and woodland, and Rocky 

Mountain conifer forest, with increases of suitable climate for semidesert grassland, and little change by year 2090 for Madrean conifer 

forest and Sonoran desert scrub.

Reports for Arizona suggest this sub-species occurs more abundantly 

in association with more mesic areas (which may or may not include 

forests and riparian areas).

We considered it likely that habitat will decline due to reduced 

moisture (increased aridity). Not clear whether habitat might increase 

at higher elevations where temperatures are colder.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Non-breeding habitat the same as breeding habitat; see Habitat, 

Question 1.

2

3. Habitat 

components: 

breeding

Are specific habitat 

components required 

for breeding 

expected to change? 

Not clear if long-tailed voles require standing water. The presence of 

standing water was not considered a requirement by some authors 

(Borell and Ellis 1934 as cited in Smolen and Keller 1987). In 

Nevada, long-tailed voles have been found as far as 0.81 km from 

water (Hall 1946 as cited in Smolen and Keller 1987). Findley and 

others (1975) indicated that in the laboratory, Microtus longicaudus

appeared to have greater drinking water needs than M. mexicanus or 

M. montanus, and that short-term water deprivation was often fatal. 

Not clear how this translates to field conditions.

Voles build nests for rearing young, resting, and protection from 

extreme environmental conditions (Pugh and others 2003). Nests are 

formed from dried grass and plant fibers, and can either be above- or 

belowground and placed under rocks or logs, near boards or 

fenceposts, or in brush piles.

Overall, not clear if there are identifiable habitat components that will 

be altered by climate change.

0

4. Habitat 

components: 

Are specific habitat 

components required 

No clear information on relationships. 0
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178

Habitat: White-bellied long-tailed vole (Microtus longicaudus leucophaeus)

Trait/Quality Question Background info. & explanation of score Points

non-breeding for survival during 

non-breeding 

periods expected to 

change?

In Alaska, herbs were considered critical for over-winter survival 

(Van Horne 1982); covered under Biotic Interactions, Question 1.

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

In Alaskan coastal coniferous forest, long-tailed voles occurred in the 

greatest density (which was related to high productivity) where herb 

and shrub cover was high (Van Horne 1982). Not clear whether this 

translates to current occupied areas for this sub-species.

0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

Recruitment and over-winter survival decreased as forb cover 

decreased through forest succession and shading increased (Van 

Horne 1982). Not clear whether this was related to food or something 

else; also unclear whether this applies to current occupied areas for 

this sub-species.

See Habitat, Question 5.

0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Individuals appear to move only small distances. The average 

distance moved of Microtus spp. among multiple capture sites in 

California was 59 m for males and 49 m for females, with 3 males 

moving >1000 m (Jenkins 1948 as cited in Smolen and Keller 1987). 

Van Horne (1982) documented 4 long-tailed voles moving 0.5 km, 

and one adult male that moved 1.1 km.

1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

No information found to indicate that additional habitats are used. 0

Physiology: White-bellied long-tailed vole (Microtus longicaudus leucophaeus)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

In captivity, above 35 °C, long-tailed voles spent 90% of their time 

lying flat on their stomachs (Beck and Anthony 1971). In captivity, 

they appear to have no behavioral mechanisms for temperature 

regulation when ambient temperatures are above 30 °C. Temperatures 

above 35 °C are lethal to M. montanus within 2 hours (Packard 1968 

as cited in Beck and Anthony 1971). Voles are not known to have 

specific physiological traits for conserving body water and are not 

considered “arid adapted” (Pugh and others 2003). Voles build nests 

for rearing young, resting, and protection from extreme 

environmental conditions, and nests can either be above- or 

belowground, and under rocks or logs (Pugh and others 2003).

We assumed that temperatures will remain below physiological 

thresholds most of the time.

See also Physiology, Questions 3 and 4.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

Are extreme weather 

or disturbance 

events that result in 

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We assumed it 

0
USDA Forest Service RMRS-GTR-273. 2012. 141

179

Physiology: White-bellied long-tailed vole (Microtus longicaudus leucophaeus)

Trait/Quality Question Background info. & explanation of score Points

conditions direct mortality or 

reproductive failure 

expected to change?

unlikely that heat waves would cause widespread mortality.

See also Physiology, Questions 1 and 4.

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Spicer (1985) indicated that voles are active diurnally and nocturnally 

and that this sub-species was trapped at night and during the day. In 

Alaska, long-tailed voles were observed to be active mostly at night 

(Van Horne 1982). Voles must eat frequently, so activity tends to be 

intermittent (Pugh and others 2003).

Not clear that activity periods overall will be reduced.

See also Physiology, Questions 1 and 3.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Voles are homeotherms; they have not been documented to use 

seasonal hibernation, daily torpor, or prolonged fasting (Wunder 1985 

as cited in Pugh and others 2003). Pugh and others (2003) described 

physiological, morphological, and behavioral traits for dealing with 

cold temperatures. 

1

6. Survival 

during

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Voles may clip grass for winter storage (Wunder 1978 in Pugh and 

others 2003). Microtus xanthognathus has been reported to store 

rhizomes (Wolff and Lidicker 1980 as cited in Pugh and others 2003). 

Little documentation of vole food storage (Wunder 1985 as cited in 

Pugh and others 2003). Mattson (2004) documented bears consuming 

vole caches (Microtus spp.) in Yellowstone National Park.

We assumed that, at high elevations where snow cover exists in 

winter, food storage would be primary method of survival since voles 

are not known to use torpor (see Physiology, Question 5).

-1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

None reported. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Long-tailed voles rarely live more than 1 year (Jenkins 1948 as cited 

in Smolen and Keller 1987). Females may ovulate as early as 3 weeks 

of age and gestation is 20-23 days; this effectively allows the 

population to increase during favorable environmental conditions 

(Pugh and others 2003). This ability to increase population size 

rapidly would not appear to offer specific resistance against 

unfavorable conditions, however. While, Van Horne (1982) indicated 

that long-tailed voles are thought to exhibit annual fluctuations in 

density (though not multi-annual fluctuations as in some other vole 

species), Spicer (1985) indicated that this sub-species is not known to 

have population irruptions.

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce food resources to the point that voles have 

insufficient food for breeding, most of the population would not 

survive longer than the periods of limited reproduction.

1
142 USDA Forest Service RMRS-GTR-273. 2012.

180

Phenology: White-bellied long-tailed vole (Microtus longicaudus leucophaeus)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

In Nevada, the breeding season is from May-October with June and 

July showing the most reproductive activity (Hall 1946 as cited in 

Smolen and Keller 1987). Ovulation appears to be induced by 

copulation or hormonal stimulation (Seabloom 1985 as cited in Pugh 

and others 2003). Jannett (1982) indicated that estrus is male-induced 

and is not an estrus cycle. Odor is the predominant cue used to 

evaluate reproductive status and receptivity. Little information on this 

topic, although Van Horne (1982) suggested that in Alaskan 

coniferous forest, reproduction may be cued to day length and 

temperature proximately, but ultimately to a berry crop.

0

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Little information available. Changes in precipitation and increases in 

temperature can alter timing of food availability, which could alter 

timing of breeding. 

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

Critical resources for breeding probably involve food but relationship 

is unclear.

0

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Long-tailed vole young are born at least from late April-September; 

believed that females have more than 1 litter during the year 

(Hoffmeister 1986). Van Horne (1982) observed that at least half of 

the females produced 2 litters in a season (in Alaska); number of 

litters may differ according to latitude. Females reported to produce 

no more than 2 litters in their lifetime (Smolen and Keller 1987); this 

observed by Van Horne (1982) in Alaska. The mean number of 

embryos was 4.51 (range 2-7; n=39 females that had embryos). 

-1

Biotic interactions: White-bellied long-tailed vole (Microtus longicaudus leucophaeus)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Voles are herbivores. Pugh and others (2003) indicated that most 

species of Microtus consume a wide variety of food items (mostly 

green succulent vegetation), and that items may change in relative 

proportions and species from one season to the next and from one 

year to the next. Microtus spp. may consume roots, bark, and fungi; 

rarely do they consume insects or meat. In Alaska, herbs were 

considered critical for over-winter survival (Van Horne 1982). Longtailed voles consume fruits and seeds mostly, but also dicots and some 

monocots (Van Horne 1982). In Wyoming, diets consisted of 38% 

green plant material by volume, 1% seed fragments, and 61% 

unidentified matter (n=14; Clark 1973 as cited in Smolen and Keller 

1987). Other items recorded include fungus and sagebrush bark and 

leaves in Nevada in winter (see references in Smolen and Keller 

1987).

Growth rates of the first and second cohorts of Microtus montanus

offspring in Wyoming were significantly lower in a year of low 

summer rainfall (1988) than in a summer of heavy rainfall (1987), and 

production from a third cohort was lower. Grasses and sedges were 

1
USDA Forest Service RMRS-GTR-273. 2012. 143

181

Biotic interactions: White-bellied long-tailed vole (Microtus longicaudus leucophaeus)

Trait/Quality Question Background info. & explanation of score Points

shorter in 1988 than in 1987.

Although long-tailed voles eat a variety of foods, their dependence on 

green vegetation will potentially be reduced by increased aridity.

2. Predators Are important 

predator populations 

expected to change?

Predators include barn owls, great horned owls, long-eared owls, 

short-eared owls, prairie falcon, ermines, long-tailed weasels, and 

pine martens (see references in Smolen and Keller 1987). Most 

species of raptors feed on voles; during vole irruptions, other species 

may prey on them (e.g., shrikes, magpies, crows, white-tailed kites, 

great blue herons, and bitterns; references in Pugh and others 2003). 

Other mammalian predators of voles include short-tailed shrews, 

badgers, coyotes, skunks, weasels, and bobcats; reptile predators 

include a variety of snakes (references in Pugh and others 2003).

Long-tailed Voles have a suite of predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found to suggest existence of important symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Long-tailed voles have been reported to have a variety of parasites. 

Reported endoparasites include Giardia spp. and three species of 

nematodes (see references in Smolen and Keller 1987). Reported 

ectoparasites include mites, fleas, lice, and ticks. Also cestodes (Pugh 

and others 2003). Dead voles have been found harboring the 

bacterium that causes tularemia (Francisella tularensis), but not clear 

what role this disease had in mortality observed during vole irruptions 

(Pugh and others 2003). Plague bacillus (Yersinia pestis) has been 

found in Microtus californicus.

Pugh and others (2003) reported no clear relationships of widespread 

mortality to disease.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Hoffmeister (1986) indicated that in Arizona, M. montanus occurs 

only in the White Mountains (Apache and Greenlee Counties); M. 

mexicanus indicated as occurring in areas north of CNF.

0

Literature Cited

Beck, L.R., and R.G. Anthony. 1971. Metabolic and behavioral thermoregulation in the long-tailed vole, 

Microtus longicaudus. Journal of Mammalogy 52:404-412.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Jannett, F.J., Jr. 1982. Male-induced estrus in the long-tail vole (Microtus longicaudus) and the sagebrush 

vole (Lagurus curtatus). American Zoologist 22:932.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Mattson, D.J. 2004. Consumption of voles and vole food caches by Yellowstone grizzly bears: 

Exploratory analyses. Ursus 15:218-226.

Pugh, S.R., S. Johnson, and R.H. Tamarin. 2003. Voles. In: Feldhamer, G.C., B.C. Thompson, and J.A. 

Chapman, eds. Wild mammals of North America: Biology, management, and conservation. Baltimore, 

MD: Johns Hopkins University Press. 1216 p.

Smolen, M.J., and B.L. Keller. 1987. Microtus longicaudus. American Society of Mammalogists. 

Mammalian Species No. 271: 1-7.

Spicer, R.B. 1985. Status of the white-bellied vole, Microtus longicaudus leucophaeus Allen, of 

southeastern Arizona. Prepared for: Office of Endangered Species, U.S. Fish and Wildlife Service, 
144 USDA Forest Service RMRS-GTR-273. 2012.

182

Albuquerque, NM. Prepared by: Arizona Game and Fish Department, Phoenix. Contract # 14-16-0002-

82-216.

U.S. Forest Service. 2009. Draft Coronado National Forest ecological sustainability report. Tucson, AZ: 

U.S. Department of Agriculture, Forest Service. Available: http://www.fs.fed.us/r3/coronado/planrevision/documents/final/cnf-ecological-sustainability-report-final-022009.pdf.

Van Horne, B. 1982. Demography of the longtail vole Microtus longicaudus in seral stages of coastal 

coniferous forest, southeast Alaska. Canadian Journal of Zoology 60:1690-1709.

Habitat: Coues’ white-tailed deer (Odocoileus virginianus couesi)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change? 

The white-tailed deer has a large range, from southern Canada 

throughout most of the coterminous United States, to northern South 

America (although not present in Utah and rare in Nevada and 

California; Smith 1991). The sub-species that occurs in Arizona is 

Odocoileus virginianus couesi (in eastern New Mexico and Texas, O. 

v. texanus occurs; Hoffmeister 1986).

White-tailed deer inhabit a wide range of habitats in North America 

(from north-temperate to subtropical and semi-arid environments) and 

is most abundant east of the Mississippi River (McCabe and McCabe 

1984 as cited in Smith 1991). Within arid regions, this species occurs 

in the more mesic areas; most of its range within the Southwest 

received >25 cm of rain each years; areas with ~40 cm per year have 

the highest numbers of individuals (Smith 1991). In Mexico, they are

most abundant in pine-oak forests, and in Central America, most 

abundant in second-growth forests, thickets, and forest-savannah 

ecotones.

In Arizona, they occur in mountain ranges in southeastern Arizona, as 

well as on the Mogollon Plateau and other areas; also observed in 

desert ranges (Ajos, Growlers, and Saucedas; Hoffmeister 1986). In 

Arizona, found mostly in woodlands (evergreen oaks or oak-juniperpinyon) but also in ponderosa pine forest, desert scrub, and deciduous 

forest, and occasionally in spruce-fir in the Graham Mountains 

(Hoffmeister 1986). Hoffmeister (1986) indicated that probably more 

than three-quarters of individuals in Arizona occur in the oaks, 

junipers, pinyon, Apache, and Chihuahuan pines.

Overall, habitat for white-tailed deer has increased in some areas 

through increases in second-growth forest, openings, and farmlands 

as a result of logging, clearing, and agriculture; forest openings and 

early-successional habitats have benefitted the species (Smith 1991). 

Expansion into west Texas and other arid regions has been 

encouraged by irrigation. Tree removal improved forage in previously 

unoccupied portions of northern boreal forests (Smith 1991).

Seasonal drought is thought to exclude white-tailed deer from western 

Arizona; the disappearance of isolated populations from western-most 

portions of the range in Arizona were thought to be correlated with an 

increased propensity for spring drought since 1950 (Brown and Henry 

1981).

Coues’ white-tailed deer occur, or potential habitat exists, on all 12 of 

the EMAs on CNF (USFS 2009). Projections of suitable climate for 

vegetation communities forest wide (Chapter 1) predicted declines in 

suitable climate for all plant community types, with the exception of 

increases of suitable climate for semi-desert grassland and small 

increases in Sonoran desert scrub (present in small amounts on the 

CNF).

2
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183

Habitat: Coues’ white-tailed deer (Odocoileus virginianus couesi)

Trait/Quality Question Background info. & explanation of score Points

Although white-tailed deer have been observed to prefer early 

successional forests, in the Southwest, woodlands and pine forests 

may already be fairly open compared to northern-latitude forests.

Thus, we expected that wildfire and increased aridity have the 

potential to reduce habitat rather than increase it.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Although high-elevation individuals may move to lower elevations in 

winter, we assumed that they still utilize woodlands in winter.

See Habitat, Question 1.

2

3. Habitat 

components: 

breeding

Are specific habitat 

components required 

for breeding 

expected to change? 

Abundance of white-tailed deer in the Great Plains is limited by the 

quality and amount of vegetative cover (references in Smith 1991). In 

areas not heavily forested, the density and distribution is lower in 

areas with less riparian and other woody cover (references in Smith 

1991).

Free-standing water appears to be utilized by desert mule deer (O. 

hemionus crooki) in the region, and we assumed these trends apply to 

O. virginianus. Several tagged desert mule deer in Arizona (Picacho 

Mountains) observed at 6 catchments, 1 spring, and ephemeral rain 

pools, visited water sources generally once per day, consuming 1.5-

6.0 L per visit (Hazam and Krausman 1988). Large males were not 

observed at catchments in summer. Females in summer consumed the 

largest amounts of water (possibly related to lactation). There is 

debate over whether mule deer require free-standing water (see 

references in Kie and others 2003). It appears that the absence of 

standing water represents marginal conditions (Severson and Medina 

1983 as cited in Kie and others 2003).

A study of 9 female desert mule deer in Arizona (Belmont and 

Bighorn Mountains) found that the mean distance to water during 

fawning was not different from the non-fawning season (2.7 km and 

2.5 km, respectively; Fox and Krausman 1994). In this same study, 

home ranges of females usually contained or were near one water 

source at a minimum; such proximity has been attributed to an 

increased need for water during hot weather.

During summer (when temperatures are high and water availability is 

decreased), diurnal bed sites are considered important in enabling this 

sub-species to maintain body temperature and water balance (Knipe 

1977 as cited in Ockenfels and Brooks 1994). Tree density, tree 

species richness, and tree canopy cover were greater in bed sites than 

at random sites in the Santa Rita Mountain foothills.

Overall, reductions in natural water sources and reductions in trees 

are expected to reduce habitat components. 

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components required 

for survival during 

non-breeding 

periods expected to 

change?

Reductions in free-standing water potentially will negatively impact 

Coues’ white-tailed deer during the non-breeding season.

A study of 9 female desert mule deer in Arizona (Belmont and 

Bighorn Mountains) found that the mean distance to water during 

fawning was not different from the non-fawning season (2.7 km and 

2.5 km, respectively; Fox and Krausman 1994).

1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

A study of 9 female desert mule deer in Arizona (Belmont and 

Bighorn Mountains) showed that thermal and hiding cover were 

important components of habitat for fawns (as would be expected); 

1
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Habitat: Coues’ white-tailed deer (Odocoileus virginianus couesi)

Trait/Quality Question Background info. & explanation of score Points

reproductive success 

expected to change? 

fawns were bedded near vegetation that provided shade (Fox and 

Krausman 1994). It has been suggested that the condition and type of 

cover available for fawning influences the survival rate of fawns (see 

discussion in Fox and Krausman 1994).

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

Cover for hiding and concealment may be critical to ungulate 

population, but not clear that this is distinct from habitat needs 

covered in Habitat, Question 1 (Kie and others 2003).

0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

While white-tailed deer tend to occupy well-defined home ranges for 

multiple years (Staines 1974 as cited in Smith 1991), they have the 

ability to disperse long distances. Movements are correlated with age, 

sex, density, social interactions, latitude, season, and habitat 

characteristics (Smith 1991). Males move farther than females; young 

deer move farther than adults. Average seasonal migrations between 

15-23 km are common in northern and montane populations 

(Marchinton and Hirth 1984 as cited in Smith 1991).

-1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Individuals at high elevations often migrate to lower elevations. 

Those at highest elevations on the CNF expected to migrate to lower 

elevations for winter.

1

Physiology: Coues’ white-tailed deer (Odocoileus virginianus couesi)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Mule deer (O. hemionus) tolerate a wide range of temperatures, from 

below -15 °C in winter to >30 °C in summer in southern regions; 

Wallmo 1981 as cited in Kie and others 2003). We assumed that 

white-tailed deer have similar tolerances. This sub-species in 

Oklahoma was least active >30 °C; at high temperatures, deer use 

areas with shade trees (Ockenfels and Brooks 1994).

We assumed that temperatures will remain below physiological 

thresholds for the most part. 

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather 

or disturbance 

events that result in 

direct mortality or 

reproductive failure 

expected to change?

Extensive snow cover reduces movement and the availability of 

forage, which can lead to increase winter mortality (references in 

Smith 1991); this appears to be more of a problem in northern 

portions of North America. Snow depths of 25-30 cm may interfere 

with movements of mule deer in Colorado, with depths >50 cm 

having the potential to completely prevent access (Loveless 1967 as 

cited in Kie and others 2003). Again, we assumed that populations at 

high elevations would move down slope to areas with lower snow 

cover in the event of extreme snowfall events.

Likely that snow cover will be reduced as a result of higher 

temperatures, causing more precipitation to fall as rain than as snow.

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity of 

heat waves will affect survival and reproduction. We considered it 

0
USDA Forest Service RMRS-GTR-273. 2012. 147

185

Physiology: Coues’ white-tailed deer (Odocoileus virginianus couesi)

Trait/Quality Question Background info. & explanation of score Points

unlikely that heat waves would cause widespread mortality.

See also Physiology Question 1 above.

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Foraging is most extensive for 1-2 hours around sunrise and sunset 

(Hoffmeister 1986). In hot environments, feeding at night reduces 

thermal stress but possibly takes advantage of daily cycles of water 

content in forage species (Taylor 1969 as cited in Kie and others 

2003).

We assumed that rise in temperatures will not significantly impact 

morning and evening activity periods.

0

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

No. 1

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

No long-term food, fat, or water storage ability. 1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No alternative life history strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Females do not breed before they are 18 months old; many do not 

produce young in their first breeding effort (Hoffmeister 1986). 

Females usually produce 1 young in first birth, twins in later breeding 

seasons. As many as 65% of the fawns born in most years do not 

survive to be counted in winter surveys (Knipe 1977 as cited in 

Hoffmeister 1986).

Few individuals live more than 10 years (Halls 1978 as cited in Smith 

1991). Life expectancy is 2.5 years in Illinois (Calhoun and Loomis 

1974 as cited in Smith 1991); in Pennsylvania, life expectancy is 2 

years for males and 3 years for females (Forbes and others 1971 as 

cited in Smith 1991).

Note that seasonal drought is thought to exclude white-tailed deer

from western Arizona; the disappearance of isolated populations from 

western-most portions of its range in Arizona was thought to be 

correlated with an increased propensity for spring drought since 1950 

(Brown and Henry 1981).

If these conditions reduce resources to the point that individuals have

insufficient resources for breeding for several years, but conditions 

recover, we considered it likely that sufficient numbers of individuals 

would survive long enough to breed once conditions improve.

-1
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Phenology: Coues’ white-tailed deer (Odocoileus virginianus couesi)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Breeding activity of females is influenced by the presence of a mature 

rutting male, physical condition, and genetics (Smith 1991). “The 

ultimate determinant of breeding season is availability of adequate 

nutrition which is cued by photoperiodism (Verme and Ullrey 1984 as 

cited in Smith 1991). Females generally come into estrus in autumn 

(Sauer 1984 as cited in Smith 1991).

In Arizona, the fawning season for mule deer coincides with the 

summer monsoon (Fox and Krausman 1994); however, not clear that 

this is a cue or an ultimate evolutionary factor.

Temperature and moisture influence food abundance, but since the 

relationship to the timing of parturition would be indirect, this 

question was scored as “0.”

0

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Changes in the timing of precipitation and increases in temperature in 

spring can alter the timing of new growth in plants (see diet 

description in Biotic Interactions, Question 1), but not clear how 

white-tailed deer time breeding relative to consumption of new 

growth and whether new growth (versus other plant parts) is critical.

0

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

See Phenology, Question 2. 0

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Single breeding event per year. Females typically don’t breed until 

1.5 years of age (Halls 1978 as cited in Smith 1991) and usually 

produce 1 young in first birth, twins in later breeding seasons 

(Hoffmeister 1986).

1

Biotic interactions: Coues’ white-tailed deer (Odocoileus virginianus couesi)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

From Hoffmeister (1986): Diet changes throughout the year although 

much of what they consume is from shrubs. white-tailed deer eat 

leaves from many broad-leafed trees, including fallen leaves (both 

green and dry). A diet analysis in the Mazatzal Mountains (north of 

Phoenix) across several seasons found: (1) in midsummer, ate fruits 

of turbinella oak, skunk bush, mesquite, Emory oak, yellow-leaf 

silktassel, and catclaw acacia, as well as sagebrush; (2) in NovemberDecember, ate more shrubs (e.g., blackbrush, sagebrush, spurges, 

calliandra, and spiderwort); (3) in January, ate old leaves of shrubs 

(e.g., buckthorn, buckbrush, buckwheats, and sagebrush); (4) in late 

winter, ate new grass growth, filaree, and bromes; (5) and in the 

spring, ate new growth of sugar sumac, buckbrush, buckhorn, scrub 

oak, calliandra, and ratany (McCulloch 1973 as cited in Hoffmeister 

1986).

Anthony (1976) observed that during a year-long drought (~half the 

annual average precipitation) in southeastern Arizona, both white0
USDA Forest Service RMRS-GTR-273. 2012. 149

187

Biotic interactions: Coues’ white-tailed deer (Odocoileus virginianus couesi)

Trait/Quality Question Background info. & explanation of score Points

tailed and mule deer fed more on evergreen and drought-resistant 

species and less on deciduous shrubs.

Overall, white-tailed deer consume a variety of forage species and 

appear capable of switching forage species in periods of low rainfall.

2. Predators Are important 

predator populations 

expected to change?

Predation is listed as one of several proximate causes of death; other 

causes include disease, fence entanglement, automobile collisions, 

predation, hunter crippling, old age, and poaching (Halls 1984 as 

cited in Smith 1991). Predators include coyotes, bobcats, mountain 

lions, feral dogs, golden eagles; gray fox, owls, and hawks are 

considered predators on fawns (Hoffmeister 1986). Overall, whitetailed deer have a suite of predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found to suggest existence of important symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Disease is listed as one of several proximate causes of death (others 

include fence entanglement, automobile collisions, predation, hunter 

crippling, old age, and poaching (Halls 1984 as cited in Smith 1991). 

White-tailed deer are host to more than 100 species of internal and 

external parasites (Samuel 1994 as cited in Miller and others 2003).

High levels of mortality in southeastern U.S. populations have 

occurred due to epizootic hemorrhagic disease, and while mortality 

from this disease has occurred in Arizona, it has not been recognized 

as a significant problem in cervids in Arizona (Noon and others 

2002). Chronic wasting disease, a neurological disease caused by an 

infectious prion, affects captive and free-ranging deer in North 

America; appears that it has not been observed in Arizona (Williams 

and others 2002). Not clear whether climate change would affect 

spread or susceptibility to this disease.

Overall, did not find cases of significant mortality from disease in 

Arizona.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Mule deer also occurs in Arizona (Hoffmeister 1986). Where the two 

species occur together, white-tailed deer generally occur at higher 

elevations. Mule deer are considered better adapted to arid conditions 

than white-tailed deer based on distributional differences (Brown and 

Henry 1981).

Brown and Henry (1981) indicated that the desert mule deer may 

have replaced or displaced white-tailed deer in lower elevations; not 

clear whether this is due to direct competition or whether changes in 

habitat over time reduced suitability for white-tailed deer. Anthony 

and Smith (1977) studied the two species in the San Cayetano and 

Dos Cabeza Mountains in southeastern Arizona; in the former, there 

was a “buffer zone” between the two species, but the two were 

sympatric in the latter area, and mule deer were dominant over whitetaileds in behavioral interactions. The authors concluded that the zone 

of non-overlap suggested exclusion of white-taileds by mule deer.

Overall, even if changes in conditions favor mule deer over whitetailed deer, not clear that the former will be positively affected by 

climate change.

0

Literature Cited

Anthony, R.G. 1976. Influence of drought on diets and numbers of desert deer. Journal of Wildlife 

Management 40:140-144.
150 USDA Forest Service RMRS-GTR-273. 2012.

188

Anthony, R.G., and N. S. Smith. 1977. Ecological relationships between mule deer and white-tailed deer 

in southeastern Arizona. Ecological Monographs 47:255-277.

Brown, D.E., and R.S. Henry. 1981. On relict occurrences of white-tailed deer within the Sonoran Desert 

in Arizona. Southwestern Naturalist 26:147-152.

Fox, K.B., and P.R. Krausman. 1994. Fawning habitat of desert mule deer. Southwestern Naturalist 

39:269-275.

Hazam, J.E., and P.R Krausman. 1988. Measuring water consumption of desert mule deer. Journal of 

Wildlife Management 52:529-534.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Kie, J.G., T. Bowyer, and K.M. Stewart.2003. Ungulates in western coniferous forests: Habitat 

relationships, population dynamics, and ecoystem processes. In: Zabel, C.J., and R.G. Anthony, eds. 

Mammal community dynamics: Management and conservation in the coniferous forests of Western 

North America. Cambridge, United Kingdom: Cambridge University Press: 296-340.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Miller, K.V., L.I. Muller, and S. Demaris. 2003. White-tailed Deer. In: Feldhamer, G.C., B.C. Thompson, 

and J.A. Chapman. Wild mammals of North America: Biology, management, and conservation. 

Baltimore, MD: Johns Hopkins University Press: 906-930.

Noon, T.H., S.L. Wesche, J. Heffelfinger, A. Fuller, G.A. Bradley, and C. Regglardo. 2002. Hemorrhagic 

disease in deer in Arizona. Journal of Wildlife Diseases 38:177-181.

Ockenfels, R.A., and D.E. Brooks. 1994. Summer diurnal bed sites of Coues white-tailed deer. Journal of 

Wildlife Management 58:70-75.

Smith, W.P. 1991. Odocoileus virginianus. American Society of Mammalogists. Mammalian Species 

No. 388.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Williams, E.S., M.W. Miller, T.J. Kreeger, R.H. Kahn, and E.T. Thorne. 2002. Chronic wasting disease 

of deer and elk: A review with recommendations for management. Journal of Wildlife Management 

66:551-563.

Habitat: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change? 

Ovis canadensis mexicana is one of 6 extant sub-species of Ovis 

canadensis; it occurs in Arizona, southwestern New Mexico, western 

Texas, and portions of northern New Mexico (Shackleton 1985).

Desert bighorn sheep range from 78 m below sea-level (Death 

Valley, California) to >4200 m (Shackleton 1985). Its habitat tends to 

include vegetation associations that are adapted to dry, rocky, or 

sandy soils containing arid-adapted plants (Krausman and Bowyer 

2003). In Arizona, prefers precipitous, rocky desert ranges; 

vegetation is rarely thick or tall, and individuals often use the highest 

ridges as lookouts (Hoffmeister 1986). Buechner (1960) suggested 

that the most productive habitat in Arizona is between 3000-4000 ft 

in jojoba (Simmondsia spp.) communities as well as riparian 

communities. Hoffmeister (1986) mentioned that suitable habitat 

includes creek beds or near natural tanks; several plant species may 

be more abundant there (ocotillo, saguaro, cacti, and brittlebrush). 

Cliff and rock areas are required for escape habitat. Alderman and 

others (1989) observed common use of desert washes in Arizona. 

0
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Habitat: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

Cain and others (2005) considered Sonoran desert scrub, Madrean 

oak woodland, and semi-desert grassland as potential habitat in the 

Santa Catalina Mountains.

Visibility is an important habitat feature for bighorn sheep to avoid 

predators; some areas that had once been occupied no longer support 

sheep because vegetation increased following fire suppression (see 

references in Krausman and Bowyer 2003). Maturing chaparral 

resulted in reduced visibility, which lowered its suitability for 

bighorn (DeForge 1980 as cited in Krausman and Bowyer 2003). 

Wilson and others (1980) indicated that areas of dense vegetation 

over 30 inches tall are generally used less than areas with shorter 

vegetation, or are avoided. Low-severity fires may not significantly 

reduce vegetation that impedes visibility for desert bighorn sheep

(Cain and others 2005).

Surveys by the Arizona Game and Fish Department documented 

bighorn sheep within the last 5 years in the Galiuro and Peloncillo 

Mountains (Brochu, personal communication). Sheep in the Galiuro 

Mountains were observed on CNF lands. Hoffmeister (1986) 

indicated that in 1974, 14 individuals were reported in the Santa 

Catalina’s and 60 in the early 1980s. Desert bighorn sheep may no 

longer regularly occupy the Santa Catalina range (Heffelfinger, 

personal communication).

Desert bighorn sheep occur, or potential habitat exists, on the 

Galiuro, Peloncillo and Santa Catalina EMAs on CNF (USFS 2009). 

Projections of suitable climate for vegetation communities on these 

three EMAs (Chapter 1) predicted declines in suitable climate for 

Madrean forest and woodland and Madrean coniferous forest, an 

increase in semi-desert grassland, and a small increase in Sonoran 

desert scrub.

Assuming that desert bighorn sheep can utilize semi-desert grassland 

that is expected to increase, we expected that habitat will be typeconverted.

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

We assumed that non-breeding habitat is similar to breeding habitat 

on the CNF. See Habitat, Question 1.

0

3. Habitat 

components: 

breeding

Are specific habitat 

components required 

for breeding 

expected to change? 

The importance/requirement of sources of free-standing water is 

debated. Water is obtained through food (e.g., saguaro, cholla, prickly 

pear and other cacti, and agave; Hoffmeister 1986). Bradley (1963) 

suggested that bighorn sheep probably need to drink at least every 

few weeks. Krausman and Bowyer (2003) did not indicate that 

bighorn sheep require free-standing water. Desert bighorn sheep 

occupy the Little Harquahala Mountains in Arizona where freestanding water is not known to occur (Alderman and others1989).

We did not consider free-standing water a habitat component required 

for breeding.

Females seek steep, rugged terrain to be secluded while giving birth 

(Krausman and Bowyer 2003; Bangs and others 2005a). Parturition 

sites are used for only a few days (Bangs and others 2005a). This 

availability not expected to change as a direct result of climate 

change. 

0
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Habitat: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

4. Habitat 

components: 

non-breeding

Are specific habitat 

components required 

for survival during 

non-breeding 

periods expected to 

change?

See Habitat, Question 3 for discussion of water.

Bighorn sheep need cliffs and other precipitous terrain for escaping 

predators; rarely far from such cover (references in Krausman and 

Bowyer 2003). In New Mexico, locations were nearer to topography 

with 60% slope than were random locations (Bangs and others 

2005b). Availability of steep terrain not expected to change as a 

direct result of climate change. 

0

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

The distribution of water holes in Nevada influenced patterns of 

home-range use in O. c. nelsoni (references in Shackleton 1985). 

Some researchers have suggested that water is the most limiting 

factor for desert bighorn sheep (references in Broyles and Cutler 

1999). Other research (generally, more recent studies) indicated that 

the presence of perennial water sources (which provides water during 

the hottest parts of year) may not limit populations (references in 

Broyles and Cutler 1999). Broyles and Cutler (1999) detected no 

difference in relative abundance or in various measures of 

reproductive output in 4 ranges with perennial surface water 

compared to 3 ranges without (Cabeza Prieta National Wildlife 

Refuge in Arizona).

Cain and others (2008) removed water catchments in Cabeza Prieta 

NWR and compared pre- and post-removal indices in a “treatment” 

mountain range and a control range. The authors did not detect 

changes in home-range area, movement rates, or distance that sheep 

were from water during hotter months. Krausman and Bowyer (2003; 

see references therein) indicated that the value of water sources has 

been questioned because there is a lack of empirical evidence that 

artificial water sources benefit populations.

Hoffmeister (1986) indicated that rainfall in Arizona’s desert ranges 

is infrequent enough that natural catchments dry up during much of 

the year.

See also Habitat, Question 3.

0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

See Habitat, Question 5. 0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Considered very mobile. Some populations/sub-species of bighorn 

sheep move between summer and winter ranges as many as ~48 km 

(see Shackleton 1985). See also Habitat, Question 8.

-1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Some populations/sub-species of bighorn move between seasonal 

home ranges, moving to lower elevations for winter; populations 

occupying low desert ranges do not (Geist 1971 as cited in 

Shackleton 1985). Krausman and Bowyer (2003) indicated that most 

desert bighorn populations “are restricted to small areas during hot 

summer months due to suboptimal distribution of resources.” While 

most populations remain in isolated areas, others move among 

mountain ranges, move in elevation, or move to/from water sources 

(McQuivey 1978 as cited in Krausman and Bowyer 2003). Does not 

appear that desert bighorn individuals move down-slope in winter 

(Gerhart, personal communication; Heffelfinger, personal 

communication).

Flesch and others (2010) studied desert bighorn sheep in the Cabeza 

Prieta Mountains and Pinta Mountains on Cabeza Prieta NWR. They 

did not observe movements between the two mountain ranges 

(separated by an 11-km wide valley), but within mountain ranges, 

1
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191

Habitat: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

average distance moved was 1.6 km, and more movements were 

documented in late summer and fall than in winter.

Overall, seasonal movements appear to be undertaken by at least 

some individuals.

Physiology: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Desert bighorn sheep can tolerate extremes in air temperature from 20 

°F to 120 °F (Wilson and others 1980). Bighorns are diurnal but may 

be active on moonlit nights (Shackleton 1985). Desert bighorn sheep 

use both vegetation and caves as sources of thermal cover during the 

hottest parts of the day (Cain and others 2008). To dissipate heat, sheep 

pant and sweat (references in Simmons 1969). At Cabeza Prieta NWR 

(elevational range 740-3300 ft), on hot days in summer, where bighorn 

sheep were observed to bed up to 7 hours per day; “much of the 

feeding was done at night (Simmons 1969).”

See Habitat, Questions 3 and 5 for discussion of drinking water. We 

assumed temperatures will remain below physiological thresholds for 

the most part, but see Physiology, Question 4 regarding activity 

periods.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No. Temperature-dependent sex determination is mainly observed in 

reptiles and fish (Manolakou and others 2006).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme weather 

or disturbance 

events that result in 

direct mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear to what extent timing and intensity 

of heat waves will affect survival and reproduction. We considered it 

unlikely that heat waves would cause widespread mortality.

See Physiology, Question 4 for discussion of activity periods.

0

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Bighorns are diurnal but may be active on moonlit nights (Shackleton 

1985). Daily patterns are comprised of alternating feeding bouts and 

rest-rumination bouts. Feeding bouts usually occur near dawn or 

dusk. Total daily feeding time remained relatively constant 

throughout the year, except when daylight decreased in winter, 

although the mean number of feeding bouts may change from one 

season to the next (Eccles 1981 as cited in Krausman and Bowyer 

2003).

Activity of desert bighorn is affected by temperature (Chilelli and 

Krausman 1981 as cited in Krausman and Bowyer 2003). In Arizona 

(Cabeza Prieta NWR), when wet-bulb temperatures were >19 °C, 

sheep bedded in the shade on average 7 hours each day (Simmons 

1969; wet bulb temperatures are lower than dry-bulb temperatures 

when air is not 100% saturated). Average dry-bulb temperature when 

sheep bedded was 32 °C (90 °F; Simmons 1969). Heat stress in 

summer is an important issue; bedding during the hottest parts of the 

day and feeding and watering on shaded slopes helps to minimize 

negative affects (Krausman and Bowyer 2003).

During spring and summer, desert bighorn rested 60% of the day in 

Arizona (Alderman and others 1989). The hourly amount of time that 

females spent foraging was negatively correlated with mean 

temperature in all seasons. Sheep were active 39% of the night during 

summer, fall, and winter, and 26% of the night during spring. 

1
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Physiology: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

Nocturnal activity was not influenced by temperature; the same 

degree of activity occurred in winter.

Although this sub-species occurs in arid regions, it is identified as 

being sensitive to temperature. We considered it possible that 

increases in temperature would result in reduced activity.

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

No information to suggest use of torpor. 1

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Active year-round. 1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No alternative strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Although mortality for the first year of life can be as high as 90% 

(references in Krausman and Bowyer 2003), male O. c. canadensis

frequently lives 15 or 16 years (Geist 1971 as cited in Shackleton 

1985). Appears that females have a higher mortality rate than males, 

although this may be in part due to problems with properly aging 

females older than 5 years (references in Shackleton 1985).

Bender and Weisenberger (2005) found that population size and trend 

for populations in New Mexico were best described by a model that 

included only precipitation as a covariate, and that the ratio of 

lambs:females was positively related to the current year’s 

precipitation total (period from late gestation through weaning), most 

likely because precipitation influenced forage quality and quantity.

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce resources to the point that bighorn sheep have 

insufficient resources for breeding, but conditions recover after, 

likely that sufficient numbers of individuals would survive long 

enough to breed once conditions improve.

-1

Phenology: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Cues for mating and parturition not clearly related to temperature or 

moisture.

Considering the range of bighorn sheep, differences in mating period 

characteristics (onset, extent of synchrony, and mating period 

duration) and timing of lambing are related to local environmental 

conditions, which appear to be related to the timing of plant growth; 

for example, the lambing period begins earlier and ends later in 

southern populations (references in Thompson and Turner 1982; 

Shackleton 1985). The mating season (rut) begins with males joining 

0
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Phenology: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

maternal groups; courtship begins when an estrous female is detected 

by a male using olfaction (Shackleton 1985).

Bighorn sheep have an extended mating period (references in 

Krausman and Bowyer 2003); births are documented in the Sonoran 

Desert in all months except October. Poor correlation between start 

and length of growing season and lambing period thought to be due to 

unpredictable precipitation patterns. This may be an adaptive strategy 

to varying and unpredictable forage production.

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Bighorn sheep have an extended mating period (references in 

Krausman and Bowyer 2003); births are documented in the Sonoran 

Desert in all months except October. Poor correlation between start 

and length of growing season and lambing period thought to be due to 

unpredictable precipitation patterns. This may be an adaptive strategy 

to varying and unpredictable forage production.

-1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

See Phenology, Question 1. 0

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Females generally do not breed until they are 2.5 years old 

(Hoffmeister 1986). Only one breeding event per year; breeding 

occurs between July and September (peak in August) and young are 

born usually in February in Arizona (Russo 1956 as cited in 

Hoffmeister 1986). 

1

Biotic interactions: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Bighorn sheep are considered relatively opportunistic in their diet 

with relative proportions of browse, forbs, and grass varying by subspecies, population, sex, and age (references in Krausman and 

Bowyer 2003). Desert bighorn tend to consume more browse than 

grasses and forbs. Preferred foods are fruits and leaves of mesquite, 

ironwood, palo verde, catclaw, coffeeberry, bush muhly, jojoba, 

brittlebrush, and calliandra; also feed on dry leaves of three-awn, 

fillaree, galleta, and fluff grass, as well as scrape the ground to access 

roots (Hoffmeister 1986). Near Yuma at the Kofa NWR (Sonoran 

zone), plants that are considered important include Mormon tea, 

grama, agave, ratany, desert mallow, prickly pear, bursage, 

desertthorn, and plantain (Halloran and Crandall 1953). Diet breadth 

can vary from one day to the next; numerous species of plants may be 

consumed in one day, but the next day, only one or a few species may 

be consumed (Hoffmeister 1986).

Sheep in Chihuahua, Mexico, “like all other sheep of the southern 

deserts including Texas and Arizona” ate little grass but ate a large 

variety of desert vegetation, including cactus and its fruit (Sheldon 

1925 as cited in Halloran and Crandall 1953). In Texas, sheep were 

“especially fond of the browse of mountain mahogany, syringa, 

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Biotic interactions: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

Ceanothus, and other common shrubs and feed to a great extent on 

the smaller plants” and may feed to a small extent on grasses (Bailey 

1928 as cited in Halloran and Crandall 1953).

Hoffmeister (1986) indicated that “water is considered as important 

as food;” some of the plants that consume provide water (e.g., 

saguaro, cholla, prickly pear, other cacti, and agave). Saguaro fruits 

are especially sought for food (Hoffmeister 1986).

Overall, a variety of forage species are consumed.

2. Predators Are important 

predator populations 

expected to change?

Young sheep may be preyed upon by eagles, coyotes, and bobcats 

(Hoffmeister 1986). Coyote predation is mostly on young sheep; 

cougars are also documented predators (references in Shackleton 

1985). Mountain lion predation was documented for desert bighorn 

sheep (mostly adults) in the Sierra Ladron Mountains in New Mexico 

(Rominger 2004) following the introduction of bighorn sheep to this 

area, which was not known to support them historically.

Overall, bighorn sheep have a suite of predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found to suggest existence of important symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Disease can be a significant cause of mortality for bighorn sheep with 

sudden mortality of notable numbers of individuals reported as 

common (see references in Krausman and Bowyer 2003).

Hoffmeister (1986) indicated that they “readily and frequently have 

bacterial infections, some of which are lethal. They also have 

tapeworms and lung infections.” Bighorns are susceptible to 

bluetongue (caused by bluetongue virus), contagious ecthyma, 

parainfluenza, encephalitis, and various bacterial infections 

(Shackleton 1985). A significant source of mortality can result from 

chronic sinusitis in this sub-species (Bunch 1980 as cited in 

Shackleton 1985). Introduced mites of domestic sheep cause scabies 

in bighorn sheep, which can result in significant mortality (references 

in Shackleton 1985).

Lungworm-pneumonia complex can result in association with 

infections by lungworms (Protostrongylus stilesi and P. rushi; 

Buechner 1960). Hemorrhagic septicemia, which can lead to 

pneumonia, was attributed to a large die-off in Colorado in the 1920s 

(the majority of a herd of 350 sheep); this condition is caused by a 

bacterium Pasteurella oviseptica (Buechner 1960). However, there 

was some debate as to whether this was the actual cause of mortality.

The virus causing epizootic hemorrhagic disease was found in tissues 

of a desert bighorn sheep in Arizona that also possessed lesions 

typical of the disease (Noon and others 2002) and was thought to be 

the first record of this disease in Arizona bighorn.

Not clear that above diseases will increase in prevalence as a result of 

projected changes in climate. 

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

Overgrazing by cattle and desert bighorn is said to limit the density of 

sheep through competition for space and forage (Krausman and

Bowyer 2003). Competition from domestic sheep and goats 

historically has been the most serious type of competition for desert 

bighorn. Diet and habitat overlap with other ungulates (Shackleton 

1985). Deer often use the same habitat; cattle are said to have same 

diet but do not overlap in steep terrain (references in Shackleton 

1985). Domestic sheep and Barbary sheep (native to Africa) are 

considered the biggest competitive threats to bighorn sheep across 

0
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Biotic interactions: Desert bighorn sheep (Ovis canadensis mexicana)

Trait/Quality Question Background info. & explanation of score Points

their range. Feral burros consume browse species of plants in many 

areas, which suggests forage competition with bighorns where the 

two species co-occur (see references in Krausman and Bowyer 2003).

Not expected that above competitors will increase as a result of 

projected changes in climate. 

Literature Cited

Alderman, J.A., P.R. Krausman, and B. D. Leopold. 1989. Diel activity of female desert bighorn sheep in 

western Arizona. Journal of Wildlife Management 53:264-271.

Bangs, P.D., P.R. Krausman, K.E. Kunkel, and Z.D. Parsons. 2005a. Habitat use by desert bighorn sheep 

during lambing. European Journal of Wildlife Research 51:178-184.

Bangs, P.D., P.R. Krausman, K.E. Kunkel, and Z.D. Parsons. 2005b. Habitat use by female desert 

bighorn sheep in the Fra Cristobal Mountains, New Mexico, USA. European Journal of Wildlife 

Research 51:77-83.

Bender, L.C., and M.E. Weisenberger. 2005. Precipitation, density, and population dynamics of desert 

bighorn sheep on San Andres National Wildlife Refuge, New Mexico. Wildlife Society Bulletin 

33:956-964.

Bradley, W.G. 1963. Water metabolism in desert mammals. Transactions of the Desert Bighorn Council 

7:26-39. Available: http://www.desertbighorncouncil.org/transactions_old.html.

Brochu, Ben. 2011. [Personal communication]. May 25, 2011. Tucson, AZ: Arizona Game and Fish 

Department, Wildlife Manager.

Broyles, B., and T.L. Cutler. 1999. Effect of surface water on desert bighorn sheep in the Cabeza Prieta 

National Wildlife Refuge, southwestern Arizona. Wildlife Society Bulletin 27:1082-1088.

Buechner, H.K. 1960. The bighorn sheep in the United States, its past, present, and future. Wildlife 

Monographs 4:1-174.

Cain, J.W., III, H.E. Johnson, and P.R. Krausman. 2005. Wildfire and desert bighorn Sheep habitat, Santa 

Catalina Mountains, Arizona. Southwestern Naturalist 50:506-513.

Cain, J.W., III, P.R. Krausman, J.R. Morgart, B.D. Jansen, and M.P. Pepper. 2008. Responses of desert 

bighorn sheep to removal of water sources. Wildlife Monographs 171:1-30.

Flesch, A.D., C.W. Epps, J.W. Cain, III, M. Clark, P.D. Krausman, and J.R. Morgart. 2010. Potential 

effects of the United States-Mexico border fence on wildlife. Conservation Biology 24:171-181.

Halloran, A.F., and H.B. Crandell. 1953. Notes on bighorn food in the Sonoran Zone. Journal of Wildlife 

Management 17:318-320.

Heffelfinger, Jim. 2010. [Personal communication]. May 20, 2010. Tucson, AZ: Arizona Game and Fish 

Department, Game Specialist.

Hoffmeister, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish 

Department. 602 p.

Krausman, P.R., and R.T. Bowyer. 2003. Mountain sheep. In: Feldhamer, G.C., B.C. Thompson, and J.A. 

Chapman, eds. Wild mammals of North America: Biology, management, and conservation. Baltimore, 

MD: Johns Hopkins University Press: 1095-1115.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Noon, T.H., S.L. Wesche, D. Cagle, D.G. Mead, E.J. Bicknell, G.A. Bradley, S. Riplog-Peterson, D. 

Edsall, and C. Reggiardo. Hemorrhagic disease in bighorn sheep in Arizona. Journal of Wildlife 

Diseases 38:172-176.

Rominger, E.M., H.A. Whitlaw, D.L. Weybright, W.C. Dunn, and W.B. Ballard. 2004. The influence of 

mountain lion predation on bighorn sheep translocations. Journal of Wildlife Management 68:993-999.
158 USDA Forest Service RMRS-GTR-273. 2012.

196

Shackleton, D.M. 1985. Ovis canadensis. American Society of Mammalogists. Mammalian Species No. 

230:1-9.

Simmons, N.M. 1969. Heat stress and bighorn behavior in the Cabeza Prieta Game Range, Arizona. 

Transactions of the Desert Bighorn Council 13:55-63. Available: 

http://www.desertbighorncouncil.org/transactions_old.html.

Thompson, R.W., and J.C. Turner. 1982. Temporal geographic variation in the lambing season of bighorn 

sheep. Canadian Journal of Zoology 60:1781-1793.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-evision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Wilson, L.O., J. Blaisdell, G. Welsh, [and others]. 1980. Desert Bighorn habitat requirements and 

management recommendations. Transactions of the Desert Bighorn Council 24:1-7. Available: 

http://www.desertbighorncouncil.org/transactions_old.html.

Habitat: Sonoran desert tortoise (Gopherus agassizii, Sonoran population)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change? 

Gopherus agassizii occurs in southern Utah, southern Nevada, 

western Arizona, and southeastern California, most of Sonora to 

northwestern Sinaloa, Mexico (Auggenberg and Franz 1978). Two 

geographic assemblages of tortoise have been identified among desert 

tortoises in the United States by genetic analyses; the “Mohave 

assemblage” generally coincides with the range of the Mohave Desert 

(north and west of the Colorado River) and the “Sonoran assemblage” 

(south and east of the Colorado River; Lamb and McLuckie 2002).

Recently, a study provided evidence to support recognition of desert 

tortoise populations south and east of the Colorado River (i.e., the 

Sonoran population) as a distinct species, Gopherus morafkai 

(Murphy and others 2011). We have retained the use of G. agassizii

for this report.

In Arizona, the range of the Sonoran desert tortoise occurs in Sonoran 

desert scrub (Van Devender 2002a). In the Sonoran Desert, tortoises 

typically occur on rocky slopes and bajadas and deeply incised 

washes emanating from rocky bajadas, are absent from intermountain 

valley floors (Riedle and others 2008). Averill-Murray and AverillMurray (2005) found this species in intermountain valleys in low 

densities in Ironwood Forest National Monument in Arizona. This 

species has been reported in ecotonal areas comprised of Sonoran 

desert scrub with “elements” of Mohave desert scrub, juniper 

woodland, interior chaparral, and desert grassland (Averill-Murray 

and others 2002b).

This species occurs, or potential habitat exists for this species, on the 

following EMAs: Tumacacori, Galiuro, and Santa Catalina (USFS 

2009). Projections of suitable climate for vegetation communities 

(Chapter 1) predicted declines in suitable climate for Madrean forest 

and woodland, Madrean conifer forest, with increases of suitable 

climate for semi-desert grassland and small increases on Chiricahua 

EMA for Sonoran desert scrub.

Overall, expect that projected changes in Sonoran desert scrub would 

not result in significant reductions in desert scrub for this species, and 

possibly would increase it.

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Habitat: Sonoran desert tortoise (Gopherus agassizii, Sonoran population)

Trait/Quality Question Background info. & explanation of score Points

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Same as breeding habitat; see Habitat, Question 1. 0

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

Requires burrows, which may be formed by erosion, desert tortoises, 

or other animals (Averill-Murray and others 2002a). Tortoise nests are 

typically inside burrows (female buries eggs; Averill-Murray and 

others 2002b). In the Mohave Desert of southwestern Nevada, desert 

tortoises spend up to 95% of their life within a shelter (Nagy and 

Medica 1986 as cited in Riedle and others 2008). Uses burrows for 

nesting, courtship, escape from temperature extremes, to avoid 

predators (references in Riedle and others 2008). Desert tortoises 

show high fidelity to burrows, including returning to same 

hibernacula or nest sites in successive years (references in Riedle and 

others 2008). They use multiple shelters during the year (AverillMurray and others 2002a) and in a fenced population have been 

observed to use multiple burrows per day (Nagy and Medica 1986).

In the Sonoran Desert, use a variety of substrates for shelter, generally 

under rocks, but also they use woodrat middens, burrows dug by other 

animals, or caliche caves (references in Riedle and others 2008). In 

south-central Arizona (Florence Military Reservation), utilized 

caliche caves as shelter more than other types of shelter (Riedle and 

others 2008).

Shelter availability in the Sonoran Desert depends on the “complexity 

and geological structure of the terrain (Averill-Murray and others 

2002a).”

Availability of burrows not expected to change as a result of climate 

change.

0

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

Requires burrows for over-wintering; see Habitat, Question 3. 0

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

Found no information on variation in reproductive success as related 

to habitat features for the Sonoran desert tortoise. It appears that there 

is little or none for desert tortoise in general.

0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

In the Sonoran Desert, density and abundance of desert tortoise varies 

widely; differences in the density of shelter sites may partly explain 

these differences (Averill-Murray and others 2002b). Availability of 

burrows not expected to change as a result of climate change.

0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Desert tortoises show high fidelity to burrows, including returning to 

same hibernacula or nest sites in successive years (references in 

Riedle and others 2008). Mean home range estimates in the Sonoran 

Desert averaged over several studies ranged from 9.2-25.8 ha for 

females and 2.6-23.3 ha for males (Averill-Murray and others 2002a). 

Dispersal by Sonoran desert tortoises away from rocky ridge habitats 

is rare, although there are instances of individuals of both sexes 

moving up to 3 km away from their activity centers over a period of a 

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Habitat: Sonoran desert tortoise (Gopherus agassizii, Sonoran population)

Trait/Quality Question Background info. & explanation of score Points

few weeks (Averill-Murray and others 2002b). In some locations, 

individuals may occur at low density in valleys between mountain 

ranges and such valleys may be important to maintaining population 

viability (Averill-Murray and Averill-Murray 2005).

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during

migration that are 

separated from 

breeding and nonbreeding habitats?

No information to indicate that additional habitats are required. 0

Physiology: Sonoran desert tortoise (Gopherus agassizii, Sonoran population)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Desert tortoises cannot tolerate body temperatures above 39.5-43.0 °C 

(Brattstrom 1965 as cited in Averill-Murray and others 2002a). Four 

desert tortoise populations in Arizona were active at temperatures 

between 20 °C and 45 °C (Woodman and others 1996 as cited in 

Averill-Murray and others 2002a). Desert tortoises are reported to use 

burrows as shelter from temperature extremes (references in Riedle 

and others 2008).

Tortoises drink standing water from puddles produced by 

thunderstorms and have been observed eating damp soil and obtaining 

water from the ground surface through their nose (Averill-Murray and 

others 2002a). Sufficient hydration allows tortoises to acquire energy 

from plants. Also, drinking water allows them to flush excess salts 

and rehydrate their bladders (see Biotic Interactions, Question 1 for 

more information on ion balance). Thus, water is particularly 

important for desert tortoise (Peterson 1996).

Expect that this species would seek out burrows to avoid exceeding 

temperature thresholds as they do currently, but reductions in 

precipitation have the potential to reduce periods with rainfall which 

could alter the ability of desert tortoises to find drinking water. Thus, 

score of “1” was assigned.

1

2. Sex ratio Is sex ratio 

determined by 

temperature? 

Temperature-dependent sex determination has been reported for this 

family (Testudinidae; Vitt and Caldwell 2009). In the northeastern 

Mojave Desert, nest temperatures exceeding 32 °C produced females, 

whereas lower temperatures produced males (Spotila and others 1994 

as cited in Averill-Murray and others 2002a); the authors indicated 

that it is likely that this threshold temperature varies across the range 

of desert tortoise. Baxter and others (2008) found some support that 

temperature during the early to middle part of incubation (day 15-45 

of a ~90-day incubation period) may play a role in sex determination 

in the Mojave Desert populations of desert tortoise.

1

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Desert tortoises are reported to use burrows as shelter from 

temperature extremes (references in Riedle and others 2008). We 

assumed that desert tortoises could survive short periods of high 

temperature by utilizing burrows.

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Physiology: Sonoran desert tortoise (Gopherus agassizii, Sonoran population)

Trait/Quality Question Background info. & explanation of score Points

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

There is a bimodal activity pattern. Active in late March or April after 

leaving winter hibernacula (though appear to be less active during this 

period than in summer). Activity declines in the dry season 

(“foresummer”) in May and June, and then activity increases again 

following start of monsoon in late July and August (Averill-Murray 

and others 2002a). Spring activity may be important for acquiring 

energy resources for egg-laying which occurs near the onset of the 

rainy season. Also, desert tortoises are generally inactive during 

midday during the hottest times of year (references in Averill-Murray 

and others 2002a).

An increase in temperature and changes in precipitation have the 

potential to alter seasonal activity periods given that currently active 

periods coincide with periods of food abundance and in summer, 

water availability.

1

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Cycles of dormancy are common in amphibians and reptiles, and 

hibernation is most likely primarily a response to cold temperatures 

and less so to a change in resource availability (Vitt and Caldwell 

2009). While hibernating, activity mostly ceases, body temperature 

depends on temperature of the hibernation site, and physiological 

processes are reduced. Such inactivity is called brumation in 

ectotherms, not hibernation.

Desert tortoises hibernate during the cool months of the year 

(November-February; Averill-Murray and others 2002a). 

Accumulates fat during summer for winter hibernation (Van 

Devender 2002a). Hibernating tortoises in a semi-natural setting 

(fenced population) did not lose significant levels of body mass or 

body water over winter (Nagy and Medica 1986). Desert tortoises also 

estivate (Nagy and Medica 1986).

We assumed that wintering sites would be largely buffered from 

increased temperatures.

0

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Ectotherm. -1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

No alternative strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Desert tortoises are long-lived species. In natural populations, 

Sonoran populations thought to reach sexual maturity at about 16 

years of age (Germano and others 2002). Sonoran desert tortoises 

have been observed to live as long as 35 years (Germano 1992 as 

cited in Averill-Murray and others 2002b). Survivorship of desert 

tortoises tends to be high (Averill-Murray and others 2002b).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce resources to the point that this species has 

insufficient resources for breeding, but conditions recover after, we 

considered it likely that sufficient numbers of individuals would 

survive long enough to breed once conditions improve.

-1
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Phenology: Sonoran desert tortoise (Gopherus agassizii, Sonoran population)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Temperature is an important cue in reptiles (Licht 1972). Tortoises 

emerge from burrows in spring, but the emergence can be protracted, 

and females appear to emerge earlier than males (Averill-Murray and 

others 2002a). Also, “temperature probably plays a more important 

role than day length in the onset of hibernation at a particular 

location.”

Rainfall appears to be a cue for emerging from burrows and feeding 

in summer. In a fenced population of desert tortoise in southern 

Nevada, 10 of 11 tortoises emerged from estivating in their burrows 

before or during a thunderstorm in mid-July, and some constructed 

shallow basins in which rainwater pooled, after which they fed on dry 

vegetation (Nagy and Medica 1986). Increased activity, drinking and 

feeding following summer rain was also observed in California 

(Minnich 1977 as cited in Nagy and Medica 1986). There is a lag of 

about 10 days between the start of summer rains and when 

“perennials have substantial new growth or summer annuals 

germinate and accumulate much biomass (Averill-Murray and others 

2002a).” 

1

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

In the Sonoran desert tortoise, egg-laying typically occurs between 

early June and early August near the start of the rainy season, 

although mean egg-laying date “does not appear to be directly related 

to recent rainfall (Averill-Murray and others 2002b).”

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

The number of Sonoran desert tortoise females breeding in a given 

year and clutch size shows a relationship to recent rainfall (AverillMurray and Klug 2000 as cited in Averill-Murray and others 2002b). 

Also shown to relate to rainfall from prior winter, presumably via 

food (i.e., spring annual plant production; Averill-Murray 2002).

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Sonoran desert tortoises lay a maximum of one clutch per year, 

although females may not reproduce in every year (references in 

Averill-Murray and others 2002b).

1

Biotic interactions: Sonoran desert tortoise (Gopherus agassizii, Sonoran population)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Desert tortoises are considered opportunistic herbivores, eating many 

different types of plants (Van Devender and others 2002b). This 

includes plant material from trees and shrubs, sub-shrubs and woody 

vines, spring annual grasses, succulents, herbaceous perennials, and 

dicot annuals.

For relationship to consuming water, see Physiology, Question 1.

Potassium intake in food may currently be a problem for desert 

tortoises, and increasing levels may cause tortoises to reduce feeding, 

or possibly stop feeding, with increasing aridity (Nagy and Medica 

1986). Desert tortoise lack functional extrarenal salt glands, unlike 

0
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201

Biotic interactions: Sonoran desert tortoise (Gopherus agassizii, Sonoran population)

Trait/Quality Question Background info. & explanation of score Points

other desert reptiles, like chuckwallas and desert iguanas, which have 

nasal salt glands through which they can excrete excess potassium. 

Thus, tortoises have to excrete potassium through urine, which uses 

body water.

2. Predators Are important 

predator populations 

expected to change?

Mortalities have been attributed to mountain lions, which are 

considered to be one of the few natural predators with the ability to 

break the shell of an adult tortoise (references in Averill-Murray and 

others 2002b). Other carnivores, such as coyotes, bobcats, foxes, 

badgers, and common ravens, may prey on hatchlings, juveniles, or 

eggs. Golden eagles and other raptors, and greater roadrunner may 

also be predators. Gila monsters are documented predators.

Overall, this species has a variety of predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found regarding important symbiotic relationships. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Upper Respiratory Tract Disease in desert tortoises is caused by 

Mycoplasma agassizii (Dickinson and others 2002) and also has been 

associated with Pasteurella testudinis, an irodovirus (Sandmeier and 

others 2009). Physical signs include discharge from the eyes and 

nose, conjunctivitis, and eyelid swelling (Jacobsen and others 1991 as 

cited in Dickinson and others 2002). Arizona Fish and Game 

conducted health studies of Mojave and Sonoran populations of 

tortoise. The 5-year study in Arizona took place in the Arizona 

Upland habitats (study plots near Bagdad and Aguila) beginning in 

1990. Sonoran populations had a low incidence of obvious 

Mycoplasma agassizii infection compared to Mohave tortoises 

(Dickinson and others 2002). Not clear that this disease causes 

consistent levels of mortality across the Mojave (Dickinson and 

others 2002).

Shell disease (cutaneous dyskeratosis) was associated with a mortality 

rate of 70% in a population of Mohave tortoises (1982-1988). 

Dickinson and others (2002) indicated that this disease may not be a 

serious problem for Sonoran populations, but more studied is 

recommended for it and Mojave populations.

Dickinson and others (2002) indicated that disease does not appear to 

be a major limiting favor of Sonoran desert tortoise. No clear 

indication that climate change would increase propensity for mortality 

from disease.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

No information found on competitors. 0

Literature Cited

Auffenberg, W., and R. Franz. 1978. Gopherus agassizii. No. 212. Catalogue of American Amphibians 

and Reptiles. Society for the Study of Amphibians and Reptiles.

Averill-Murray, R.C. 2002. Reproduction of Gopherus agassizii in the Sonoran Desert, Arizona. 

Chelonian Conservation and Biology 4:295-301.

Averill-Murray, R.C., and A. Averill-Murray. 2005. Regional-scale estimation of density and habitat use 

of the desert tortoise (Gopherus agassizii) in Arizona. Journal of Herpetology 39:65-72.
164 USDA Forest Service RMRS-GTR-273. 2012.

202

Averill-Murray, R.C., B.E. Martin, S.J. Bailey, and E.B. Wirt. 2002a. Activity and behavior of the 

Sonoran Desert tortoise in Arizona. In: Van Devender, T.R., ed. The Sonoran Desert Tortoise: Natural 

history, biology, and conservation. Tucson: The University of Arizona Press: 135-158.

Averill-Murray, R.C., A.P. Woodman, and J.M. Howland. 2002b. Population ecology of the Sonoran 

Desert tortoise in Arizona. In: Van Devender, T.R., ed. The Sonoran Desert Tortoise: Natural history, 

biology, and conservation. Tucson: The University of Arizona Press: 109-134.

Baxter, P.C., D.S. Wilson, and D.J. Morafka. 2008. The effects of nest date and placement of eggs in 

burrows on sex ratios and potential survival of hatchling desert tortoises, Gopherus agassizii. Chelonian 

Conservation and Biology 7:52-59.

Dickinson, V.M., J.L. Jarchow, M.H. Trueblood, and J.C. deVos. 2002. Are free-ranging Sonoran Desert 

tortoises healthy? In: Van Devender, T.R., ed. The Sonoran Desert tortoise: natural history, biology, and 

conservation. Tucson: The University of Arizona Press: 242-263.

Germano, D.J., F.H. Pough, D.J. Morafka, E.M. Smith, and M.J. Demlong. 2002. Growth of desert 

tortoises: Implications for conservation and management. In: Van Devender, T.R., ed. The Sonoran 

Desert tortoise: Natural history, biology, and conservation. Tucson: The University of Arizona Press: 

263-288.

Lamb, T., and A.M. McLuckie. 2002. Genetic differences among geographic races of the desert tortoise. 

In: Van Devender, T.R., ed. The Sonoran Desert tortoise: Natural history, biology, and conservation. 

Tucson: The University of Arizona Press: 67-85.

Licht, P. 1972. Environmental physiology of reptilian breeding cycles: Role of temperature. General and 

Comparative Endocrinology Supplement 3:477-488.

Murphy, R.W, K.H. Berry, T. Edwards, A.E. Leviton, A. Lathrop, and J.D. Riedle. 2011. The dazed and 

confused identity of Agassiz’s

land tortoise, Gopherus agassizii (Testudines, Testudinidae) with the description of a new species, and its 

consequences for conservation. ZooKeys 113: 39-71.

Nagy, K.A., and P.A. Medica. 1986. Physiological ecology of Desert tortoises in southern Nevada. 

Herpetologica 42:73-92.

Peterson, C.C. 1996. Ecological energetics of the desert tortoise (Gopherus agassizii): Effects of rainfall 

and drought. Ecology 77:1831-1844.

Riedle, J.D., R.C. Averill-Murray, C.L. Lutz, and D.K. Bolen. 2008. Habitat use by desert tortoises 

(Gopherus agassizii) on alluvial fans in the Sonoran Desert, south-central Arizona. Copeia 2008 

2:414-420.

Sandmeier, F.C., C.R. Tracy, S. dePré, and K. Hunter. 2009. Upper respiratory tract disease (URTD) as a 

threat to desert tortoise populations: A reevaluation. Biological Conservation 142:1255-1268.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Van Devender, T.R. 2002a. Natural history of the Sonoran Tortoise in Arizona. In: Van Devender, T.R., 

ed. The Sonoran Desert tortoise: Natural history, biology, and conservation. Tucson: The University of 

Arizona Press: 3-28.

Van Devender, T.R. 2002b. Grasses, mallows, desert vine, and more: Diet of the desert tortoise in 

Arizona and Sonora. In: Van Devender, T.R., ed. The Sonoran Desert tortoise: natural history, biology, 

and conservation. Tucson: The University of Arizona Press: 159-173.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.
USDA Forest Service RMRS-GTR-273. 2012. 165

203

Habitat: Slevin’s bunchgrass lizard (Sceloporus slevini)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change? 

Taxonomic note: This species was formerly considered Sceloporus 

scalaris slevini (Watkins-Colwell and others 2003).

From Painter (2009): This species occurs in montane habitats 

(including woodlands and forests dominated by pines), intermountain 

valleys, and riparian areas. In Arizona, elevation range is from 1300 m 

in the Sonoita Plains to ~2600 m in the Chiricahua Mountains (Barfoot 

Park). Range of this species in the United States is southeastern 

Arizona and southwestern New Mexico. It is common on east- and 

south-facing slopes where dense grasses occur. Reported in Santa Rita, 

Dragoon, Huachuca, and Chiricahua Mountains in Arizona.

Bock and others (1990) indicated that this species was abundant in 

lowland semi-desert grassland (dominated by 5 species of grama grass) 

in an area that had been protected from livestock grazing for 20 years 

(Sonoita Plain, Santa Cruz County); authors indicated that “apparent 

restriction of Sceloporus scalaris to montane meadows may be an 

historic artifact associated with chronic and ubiquitous grazing of 

lower-elevation perennial grasslands.” This species does not survive at 

lower elevations where cattle graze as a result of loss of bunchgrass

cover (Watkins-Colwell and others 2003).

This species occurs, or potential habitat exists, for this species, on the 

following EMAs: Peloncillo, Chiricahua, Dragoon, Santa Rita, 

Huachuca, and Whetstone (USFS 2009). Projections of suitable climate 

for vegetation communities (Chapter 1) predicted declines in suitable 

climate for Madrean forest and woodland, Madrean conifer forest, and 

Plains grassland, with increases of suitable climate for semi-desert 

grassland, and small increases on Chiricahua EMA for Sonoran desert 

scrub.

Overall, areas with suitable climate for semi-desert grassland expected 

to increase, which is expected to increase total amount of habitat for 

this species.

-1

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to 

change?

Same as breeding habitat; see Habitat, Question 1. -1

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

Clumps of thick grass have been called essential (Painter 2009; 

Watkins-Colwell and others 2003). In valley grasslands, grasses may 

include sacatons, grammas, panic grasses, and tobosa; in montane 

areas, bromes and muhlys are typical (Painter 2009). Grasses serve as 

cover from predators and sites for thermoregulation. Bock and others 

(1990) found this species in grazed areas lacking dense grass cover but 

where other debris occurred (boards and other surface litter) under 

which lizards were found; not clear what kind of surface litter was 

involved and whether this typically occurs in sufficient quantities in 

areas absent bunchgrass.

Overall, semi-desert grassland likely to increase, which would involve 

increase in grass cover.

-1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

See Habitat, Question 3; grass cover especially important in winter for 

thermoregulation in winter months (Painter 2009).

-1
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Habitat: Slevin’s bunchgrass lizard (Sceloporus slevini)

Trait/Quality Question Background info. & explanation of score Points

non-breeding 

periods expected to 

change?

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

No information. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to 

change?

In the Chiricahua Mountains, higher population densities were 

observed in areas with ~90% cover of grasses (Blepharoneuron 

tricholepsis, Muhlenbergia virescens, and Bromus frondosus; Ballinger 

and Congdon 1981). Ballinger and Congdon (1996) attributed loss of 

grasses from cattle grazing on the CNF in the Chiricahua Mountains to 

the severe declines of densities of this lizard species that in the 1970s 

had been 100-200 individuals per ha.

Expect grass cover to increase.

-1

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Most amphibians and reptiles move relatively little across their lifetime 

except when breeding (Vitt and Caldwell 2009). No information found 

on this species. However, in another spiny lizard in Texas, Sceloporus 

merriami, home ranges averaged 100m2

 in females and 150-250m2 in 

males.

1

8. Migratory or 

transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

No information found to indicate that additional habitats are required. 0

Physiology: Slevin’s bunchgrass lizard (Sceloporus slevini)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Members of this family (Phrynosomatidae) are diurnally active 

(Leaché 2009). This species remains active throughout the year 

(Painter 2009). Individuals actively thermoregulate and maintain body 

temperature well above that of the surrounding ambient temperature; 

body temperature in Arizona individuals (n=851) averaged 32.6 °C 

(Painter 2009). Critical thermal maximum, the temperature at which 

individuals lose their righting response, was measured in this species 

by Mathies and Andrews (1995); median values from individuals from 

high elevation populations and low-elevation populations were 44.8 °C 

and 44.6 °C, respectively. The genus Sceloporus maintains relatively 

high and stable body temperatures during activity, which is thought to 

be associated in part with open vegetation that allows for easy 

thermoregulation (Andrews 1998). Mean body temperatures of this 

genus in temperate latitudes were 35 °C (96 °F) throughout their 

elevational range (Andrews 1998).

It’s likely that lizards would seek refuge in burrows to escape 

temperature extremes (Huey and others 2010). 

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

Vitt and Caldwell (2009) did not provide information on whether 

temperature-dependent sex determination occurs in Phrynosomatidae, 

suggesting that it may be unknown. In some members of Iguania (the 

0
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Physiology: Slevin’s bunchgrass lizard (Sceloporus slevini)

Trait/Quality Question Background info. & explanation of score Points

infraorder of Squamata that contains this family as well as other 

groups), sex determination is known to be genetically based, while in 

others (e.g., Agamidae) temperature-dependent sex determination has 

been observed.

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern

United States. We assumed that lizards could survive short periods of 

high temperature by utilizing burrows, even if foraging opportunities 

were reduced for several days.

0

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Members of this family (Phrynosomatidae) are diurnally active 

(Leaché 2009). This species remains active throughout the year 

(Painter 2009). Newlin (1974), working in the Chiricahua Mountains at 

~2500 m elevation, found no significant differences in mean hourly 

capture rate or observation rate between 0900-1500, but observed 

reduced activity from 0800-0900 and 1500-1600 (observations for all 

months appear to be lumped; study conducted May-August, 

September, October and February).

In summer, activity in summer ended ~2 hours earlier in the afternoon 

at cooler high-elevation sites (2664 m, 2852 m) than at warmer lowelevation sites (1463 m) (Mathies and Andrews 1995). Warmer 

temperatures may increase activity periods for populations at high 

elevations, but not likely to increase activity periods at low elevations. 

At low elevations, which are warmer overall, activity during summer 

has the potential to be reduced. Dunham (1993) predicted that a rise of 

2 °C would severely reduce the number of hours per day Sceloporus 

merriami in Texas could be active given specific assumptions (i.e., if 

this species was active only at body temperatures of 32.2 °C); less 

restrictive assumptions resulted in less reduction in activity.

The score of “1” for this question reflects possible effect on lowelevation populations.

1

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Although cycles of dormancy are common in amphibians and reptiles, 

this species remains active throughout the year (Ballinger and Congdon 

1981; Painter 2009). Able to maintain body temperature above 

ambient; mean body temperature of 23 lizards was 31 °C when 

ambient temperature was 12 °C (Ballinger and Congdon 1981). Newlin 

(1974) observed active in February when temperatures were 10-20 °C 

and snow existed in portions of the study area.

1

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Ectotherm. -1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

Females of this species retain eggs in the body longer than other 2 

Sceloporus species that occur at lower altitudes; this may be an 

adaptation to reduce the development time of embryos in cold climates 

(DeMarco 1992). Not clear whether increases in temperature would 

result in this species reducing the time to oviposition following 

fertilization, and if so, whether this would have an effect (positive or 

negative) on fitness.

0

8. 

Reproduction 

Can this species 

outlive periods 

Individuals become reproductively active in their first year after 

hatching in September (Ballinger and Congdon 1981). In a mark1
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Physiology: Slevin’s bunchgrass lizard (Sceloporus slevini)

Trait/Quality Question Background info. & explanation of score Points

in variable 

environments

where reproduction 

is limited?

recapture 4-year study in the Chiricahua Mountains, lizards were 

observed at a minimum of 2, 3, or 4 years of age. Yearling mortality 

was estimated at 75%; although individuals as old as 5 years have been 

observed, only ~6% survived to 2 years of age or older.

In 1997, Smith and others (1998) observed dramatic reductions in 

numbers of this species on the Sonoita Plain where previously numbers 

had been high; they attributed the reduction in density to drought (low 

rainfall) in the preceding two years.

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions eliminate breeding (e.g., insufficient food), most of the 

population would not survive longer than the periods of limited 

reproduction. 

Phenology: Slevin’s bunchgrass lizard (Sceloporus slevini)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Temperature is an important cue in reptiles; it has been called the “most 

important and widespread of the timing cues for saurian reproduction 

(Licht 1972).”

This species is oviparous (Watkins-Colwell, and others 2003), which 

makes it unlike many reptiles in cold environments that bear live young. 

Newlin (1974) observed that in 1973, egg laying began in late July, 

with all females having deposited eggs by mid-August. Egg laying in 

this species coincides with the onset of summer rains (Ballinger and 

Congdon 1981), although it is not clear whether this is a cue for laying. 

Newlin (1974) indicated that mating probably occurs between February 

and May.

The typical pattern for temperate-zone lizards is for low-elevation 

populations to initiate reproduction earlier in spring than at higher, 

cooler elevations. However, a different trend has been observed in this 

species. High-elevation females began ovulating 2-3 weeks earlier than 

low-elevation females and retained their eggs longer (~40 days at 

“high” versus ~20 days at “low;” Mathies and Andrews 1995). 

1

2. Event 

timing

Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

See Phenology, Question 1.

The length of the cold season is an important constraint on how long the 

reproductive season lasts in reptiles, and soil temperatures are high 

enough only in summer for embryonic development to occur rapidly 

enough (Vitt and Caldwell 2009). Increased temperatures may alter the 

length of the breeding season.

Clutch size did not appear to vary significantly with variations in 

rainfall (Ballinger and Congdon 1981).

Changes in the timing of precipitation and increases in temperature can 

alter the timing of prey availability and abundance.

1

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

Cues and critical resources (e.g., food) expected to be closely related in 

time and space.

-1
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Phenology: Slevin’s bunchgrass lizard (Sceloporus slevini)

Trait/Quality Question Background info. & explanation of score Points

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

In southeastern Arizona at higher elevation, mating occurs in April, 

oviposition in late June through early July, and hatching in September; 

these events probably occur earlier at lower elevations (Painter 2009).

Only one clutch of eggs is produced per year per female (Newlin 1974; 

Ballinger and Congdon 1981; Painter 2009).

1

Biotic interactions: Slevin’s bunchgrass lizard (Sceloporus slevini)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

In a study in the Chiricahua Mountains, the two most important groups 

of prey based on stomach analyses were Homoptera/Hemiptera (31% by 

volume), and Hymenoptera (17% by volume); Coleoptera were 10% 

and larvae were 10% (Newlin 1974). In Durango, Mexico, in a 2-year 

study, individuals of this species consumed adult beetles (40%), ants 

(35%), hemipterans (26%) grasshoppers (68%), and beetles (35%), with 

differences among years in terms of the type of prey most consumed 

(Degenhardt 1996).

Overall, species consumes a variety of prey species.

0

2. Predators Are important 

predator 

populations 

expected to 

change?

Specific information lacking on predators of this species. Newlin (1974) 

noted that Twin-spotted rattlesnakes (Crotalus pricei) might be 

predators. We assumed that this species has a variety of predators, such 

as birds (e.g., roadrunner) and mammals and other reptiles. In general, 

lizard predators include birds, mammals, snakes, other lizards, fish, 

spiders, centipedes, scorpions, and tailless whip scorpions (Pianka and 

Vitt 2003). Predation tends to be heaviest on lizard eggs and juveniles.

0

3. Symbionts Are populations of 

symbiotic species 

expected to 

change?

No information found to indicate existence of important symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to 

change? 

Little information. Helminths were reported in individuals collected in 

California; that only immature helminthes (no adults) were found 

suggested to the authors that this lizard species host a limited parasitic 

fauna (Goldbert and Bursey 1992). 

0

5. Competitors Are populations of 

important 

competing species 

expected to 

change?

Newlin (1974) indicated that Yarrow’s spiny lizard (Sceloporus jarrovi) 

occurs sympatrically and is considered to a potential competitor, but the 

author considered it likely that the two species are separated 

ecologically due to different habitat preferences. Pygmy short-horned 

lizard (Phrynosoma douglasi) was also considered a potential 

competitor, but not readily observed in Newlin’s study.

Not clear that strong competition exists between this species and those 

mentioned above.

0
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208

Literature Cited

Andrews, R.M. 1998. Geographic variation in field body temperature of Sceloporus lizards. Journal of 

Thermal Biology 23:329-334.

Ballinger, R.E., and J.D. Congdon. 1996. Status of the bunch grass lizard, Sceloporus scalaris, in the 

Chiricahua Mountains of southeastern Arizona. Bulletin of the Maryland Herpetological Society 

32:67-69.

Ballinger, R.E., and J.D. Congdon. 1981. Population ecology and life history strategy of a montane lizard 

(Sceloporus scalaris) in southeastern Arizona. Journal of Natural History 15:213-222.

Bock, C.E., H.M. Smith, and J.H. Bock. 1990. The effect of livestock grazing upon abundance of the 

lizard, Sceloporus scalaris, in southeastern Arizona. Journal of Herpetology 24:445-446.

Degenhardt, W.G., C.W. Painter, and A.H. Price. 1996. The amphibians and reptiles of New Mexico. 

Albuquerque: University of New Mexico Press. 433 p.

DeMarco, V. 1992. Embryonic development times and egg retention in four species of sceloporine 

lizards. Functional Ecology 6:436-444.

Dunham, A.E. 1993. Population responses to environmental change: operative environments, 

physiologically structured models, and population dynamics. In: Kareiva, P.M., J.G. Kingsolver, and 

R.B. Huey, eds. Biotic Interactions and Global Change. Sunderland, Massachusetts: Sinauer Associates, 

Inc.: 95-119.

Goldberg, S.R., and C.R. Bursey. 1992. Helminths of the bunch grass lizard, Sceloporus scalaris slevini

(Iguanidae). Journal of the Helminthological Society 59:130-131.

Huey, R.B., J.B. Losos, and C. Moritz. 2010. Are lizards toast? Science 328:832-833.

Leaché, A.D. 2009. Family Phrynosomatidae: Phrynosomatid Lizards (Zebra-tailed, Earless, Fringe-toed, 

Spiny, Tree, Brush, Side-blotched, California Rock, and Horned Lizards). In: Jones, L.L.C., and R.E. 

Lovich, eds. Lizards of the American Southwest: A Photographic Field Guide. Tucson, AZ: Rio Nuevo 

Publishers: 139-141.

Licht, P. 1972. Environmental physiology of reptilian breeding cycles: Role of temperature. General and 

Comparative Endocrinology Supplement 3:477-488.

Mathies, T., and R.M. Andrews. 1995. Thermal and reproductive biology of high and low elevation 

populations of the lizard Sceloporus scalaris: implications for the evolution of viviparity. Oecologia 

104:101-111.

Newlin, M.E. 1974. Reproduction, trophic ecology, and other aspects of natural history in the bunch grass 

lizard, Sceloporus scalaris. Thesis. Angelo State University, San Angelo, TX. 111 p.

Painter, C.W. 2009. Slevin’s Bunchgrass Lizard. In: Jones, L.L.C., and R.E. Lovich, eds. Lizards of the 

American Southwest: A Photographic Field Guide. Tucson, AZ: Rio Nuevo Publishers: 250-253.

Pianka, E.R., and L.J. Vitt. 2003. Lizards: Windows to the Evolution of Diversity. Berkeley: University 

of California Press.

Smith, H.M., D. Chiszar, A. Chiszar, [and others]. 1998. Slevin’s bunch grass lizard (Sceloporus slevini) 

decimated on the Sonoita Plain, Arizona. Herpetological Review 29:225-226.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.

Watkins-Colwell, G.J., H.M. Smith, and D. Chiszar. 2003. Sceloporus slevini Smith. No. 771. Catalogue 

of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles.
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209

Habitat: Giant spotted whiptail (Aspidoscelis burti strictogrammus)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change? 

Taxonomic note: The genus for North American whiptails fairly recently 

changed from Cnemidophorus to Aspidoscelis (Persons and Wright 

2009). The giant spotted whiptail is the only sub-species of Aspidoscelis 

burti in the United States. It occurs in southeastern Arizona and extreme 

southwestern New Mexico (Rosen 2009). Canyon spotted whiptail is the 

common name used for Aspidoscelis burti (Degenhardt and others 1996, 

Rosen 2009).

From Rosen (2009): A. burti occurs primarily in “thorn scrub 

environments, in mountain canyons, in semi-desert grassland, the Arizona 

Upland portion of the Sonoran Desert, and the lower Madrean Oak 

Woodland. It also occurs along perennial streams, cienegas, and 

surrounding thorn scrub in arid valleys.” The types of plants that occur in 

preferred thickets in thorn scrub include velvet mesquite, desert 

hackberry, catclaw acacia, etc. These lizards utilize riparian woodland 

and nearby thickets, occur mostly between ~822-1219 m, and use rock 

slopes, embankments in arroyos, and vegetated bottomlands that are 

densely vegetated. Occur mainly in canyons in the Santa Catalina, 

Rincon, Santa Rita, Whetstone, Galiuro, Pinaleño, and Santa Teresa 

Mountains.

Rosen (2009) indicated that A. burti is found in canyon-bottom thickets

especially near perennial water. In New Mexico, A. burti occurs in 

riparian areas dominated by sycamore, cottonwood, and ash and grasses 

and forbs, including open areas of bunch grass within riparian areas 

(Degenhardt and others 1996).

Drying of valleys streams and frequent damage to riparian vegetation 

appear to have resulted in reductions in occurrence of this habitat in 

valleys (Rosen 2009).

The giant spotted whiptail occurs, or potential habitat exists, on all EMAs 

except for three (Chiricahua, Dragoon, and Whetstone; USFS 2009). 

Projections of suitable climate for vegetation communities on all EMAs 

combined (Chapter 1) predicted declines in suitable climate for all plant 

community types, with the exception of increases of suitable climate for 

semi-desert grassland, and small increases in Sonoran desert scrub 

(present in small amounts on the CNF).

Individuals appear to use more than one habitat, including Madrean oak 

woodland and desert riparian habitat, both of which are expected to 

decline.

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to change?

Non-breeding habitat is same as breeding habitat. See Habitat, 

Question 1.

2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

No information found to indicate existence of specific habitat 

components for breeding.

0

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

non-breeding 

No information found to indicate existence of specific habitat 

components for survival during non-breeding periods.

0
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Habitat: Giant spotted whiptail (Aspidoscelis burti strictogrammus)

Trait/Quality Question Background info. & explanation of score Points

periods expected to 

change?

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

No information found. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to 

change? 

No information found. 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Rosen (2009) indicated that individuals tend to actively forage in an 

area about 150 m in diameter.

1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

No indication that individuals undergo movements that require them to 

use additional habitats.

0

Physiology: Giant spotted whiptail (Aspidoscelis burti strictogrammus)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions 

expected to 

change?

Most members of the Family Teiidae are active foragers with high 

preferred body temperatures (Persons and Wright 2009). Whiptails 

(consist of the genus Aspidoscelis) are diurnal and are active during the 

warmest times of day.

Body temperatures are usually in the range of 37-42 °C; individuals can 

retain heat in their large mass which allows them to forage well into 

shade (Rosen 2009). They are active through the heat of the day 

generally, although they may spend more time in shade (Rosen 2009). 

The high body temperatures of whiptails in part support their high 

activity levels (Pianka and Vitt 2003).

Considered likely that lizards would seek refuge in burrows to escape 

temperature extremes (Huey and others 2010). 

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

In Vitt and Caldwell (2009), genetic sex determination is reported for 

the Teiidae family; i.e., temperature-dependent sex determination not 

known occur in this family. Note that females lay eggs (i.e., not 

viviparous).

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to 

change?

Increase in frequency of heat waves is predicted for southwestern 

United States. We assumed that lizards could survive short periods of 

high temperature by utilizing burrows; even if foraging opportunities 

were reduced for several days (see also Physiology, Question 1).

0
USDA Forest Service RMRS-GTR-273. 2012. 173

211

Physiology: Giant spotted whiptail (Aspidoscelis burti strictogrammus)

Trait/Quality Question Background info. & explanation of score Points

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to 

change?

Whiptails are diurnal, and are active during the warmest times of day, 

and therefore have shorter active seasons than other species that may 

occur in the same areas (Persons and Wright 2009). Individuals become 

active in late April to mid-May and remain active until mid-September 

or October (Rosen 2009). In temperate North America, whiptails go 

underground in fall (Pianka and Vitt 2003). Winne and Keck (2004) 

tested the hypothesis that high soil temperatures are required for 

whiptails to initiate and cease daily activity and found that circadian 

cycles in two bisexual species of Aspidoscelis (A. inornata 

heptagramma and A. gularis septemvittatus) can play an important role 

in both the initiation and cessation of daily activity. Thus, not clear the 

relative contribution of temperature versus circadian cycle to daily 

activity period.

Score of “0” reflects possibility that seasonal activity period may 

increase if spring months are warmer for longer periods, but may be 

offset if temperatures during warmest part of day become hotter.

See also Physiology, Question 1.

0

5. Metabolic 

inhibition

Does this species 

possess an ability 

to reduce metabolic 

energy or water 

requirements?

Cycles of dormancy are common in amphibians and reptiles; 

hibernation (some refer to hibernation in ectotherms as “brumation”) is 

most likely primarily a response to cold temperatures and less so to a 

change in resource availability (Vitt and Caldwell 2009). While 

hibernating, activity mostly ceases, body temperature depends on 

temperature of the hibernation site, and physiological processes are 

reduced.

Individuals are inactive in winter (see Physiology, Question 4) when 

they occupy burrows. Most temperate zone lizards become inactive 

during winter, and move underground to sites that do not freeze.

We assumed these areas would be largely buffered from increased 

temperatures.

0

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the 

capacity to store 

energy or water in 

the long term?

Ectotherm. -1

7. Variable life 

history

Does this species 

have alternative 

life history 

strategies to cope 

with variable 

resources or 

climate conditions?

Both males and females comprise this sub-species (Rosen 2009), unlike 

some other whiptails which consist of only females that reproduce by 

parthenogenesis (Persons and Wright 2009).

No known variable life history strategies.

0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

No information found on longevity but we assumed it to be a few years 

on average in the wild. Longevity record of individuals in captivity was 

3 years for the New Mexico whiptail (Cnemidophorus

neomexicanus/Aspidoscelis neomexicana; Bowler 1975).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions eliminate breeding (e.g., insufficient food), most of the 

population would not survive longer than the periods of limited 

reproduction. 

1
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212

Phenology: Giant spotted whiptail (Aspidoscelis burti strictogrammus)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Temperature is an important cue in reptiles; it has been called the “most 

important and widespread of the timing cues for saurian reproduction 

(Licht 1972).” In temperate zone lizards that become inactive in winter, 

decreasing day length and cooler temperatures trigger a response of the 

pituitary gland leading to changes in hormones that lead to the urge to 

become inactive (Pianka and Vitt 2003).

Goldberg (1987b) indicated that individuals emerged in April or early 

May “depending on yearly climatic conditions.” 

1

2. Event 

timing

Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

Most temperate zone lizards become inactive during winter, and move 

underground to sites that do not freeze; such inactivity is called 

brumation in ectotherms (not hibernation). Decreasing day length and 

colder temperatures trigger a hormonal response that leads to inactivity 

(Pianka and Vitt 2003). Pianka and Vitt (2003) indicated that in 

temperate North America, whiptails go underground in fall.

1

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

Cues and critical resources (e.g., food) expected to be closely related in 

time and space.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Females produce one or more clutches from early June through midJuly (Rosen 2009). Goldberg (1987b) found evidence of a female 

producing >1 clutch per season.

-1

Biotic interactions: Giant spotted whiptail (Aspidoscelis burti strictogrammus)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Rosen (2009) indicated that the diet probably includes arthropods as 

well as small juvenile lizards. Individuals dig in organic debris and 

under trees to find arthropods. Pianka and Vitt (2003) indicated that 

most whiptails eat a variety of insects (particularly termites) and 

spiders.

Overall, appears that giant spotted whiptails consume a variety of prey.

0

2. Predators Are important 

predator populations 

expected to change?

Predators thought to include Sonora whipsnakes and greater 

roadrunners (Rosen 2009). In general, lizard predators include birds, 

mammals, snakes, other lizards, fish, spiders, centipedes, scorpions, 

tailless whip scorpions, with predation tending to be heaviest on 

lizard eggs and juveniles (Pianka and Vitt 2003).

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found regarding symbiotic relationships. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

Four nematodes and two cestodes known in this sub-species (n=57) 

(Goldberg 1987a; Goldberg and others 1989). No information found 

indicating widespread mortality from disease.

0
USDA Forest Service RMRS-GTR-273. 2012. 175

213

Biotic interactions: Giant spotted whiptail (Aspidoscelis burti strictogrammus)

Trait/Quality Question Background info. & explanation of score Points

reproductive failure 

in this species 

expected to change? 

5. Competitors Are populations of 

important competing 

species expected to 

change?

Rosen (2009) indicated that important competitors may be the 

unisexual parthenogenetic species resulting from hybridization. These 

unisexuals do well in areas disturbed by humans. Not clear that these

unisexuals would be positively impacted by climate change.

0

Literature Cited

Bowler, J.K., 1975. Longevity of reptiles and amphibians in North American collections as of 1 

November, 1975. Society for the Study of Amphibians and Reptiles, Miscellaneous Publications, 

Herpetological Circular 6:1-32.

Degenhardt, W.G., C.W. Painter, and A.H. Price. 1996. The amphibians and reptiles of New Mexico. 

Albuquerque: University of New Mexico Press.

Goldberg, S.R. 1987a. Larval cestodes (Mesocestoides sp.) in the giant spotted whiptail, Cnemidophorus 

burti strictogrammus. Journal of Herpetology 21:337.

Goldberg, S.R. 1987b. Reproductive cycle of the giant spotted whiptail, Cnemidophorus burti 

strictogrammus, in Arizona. Southwestern Naturalist 32:510-511.

Goldberg, S.R., and C.R. Bursey. 1989. Helminths of the giant spotted whiptail, Cnemidophorus burti 

strictogrammus (Sauria: Teiidae). Proceedings of the Helminthological Society 56:86-87.

Licht, P. 1972. Environmental physiology of reptilian breeding cycles: Role of temperature. General and 

Comparative Endocrinology Supplement 3:477-488.

Pianka, E.R., and L.J. Vitt. 2003. Lizards: Windows to the evolution of diversity. Berkeley: University of 

California Press.

Persons, T.B., and J.W. Wright. 2009. Family Teiidae: Whiptails and their allies. In: Jones, L.L.C., and 

R.E. Lovich, eds. Lizards of the American Southwest: a photographic field guide. Tucson, AZ: Rio 

Nuevo Publishers: 322-325.

Rosen, P.C. 2009. Canyon Spotted Whiptail. In: Jones, L.L.C., and R.E. Lovich, eds. Lizards of the 

American Southwest: a photographic field guide. Tucson, AZ: Rio Nuevo Publishers: 330-333.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.

Winne, C.T., and M.B. Keck. 2004. Daily activity patterns of whiptail lizards (Squamata: Teiidae: Aspidoscelis): A 

proximate response to environmental conditions or an endogenous rhythm? Functional Ecology 18:314-321
176 214 USDA Forest Service RMRS-GTR-273. 2012.

Habitat: Northern Mexican gartersnake (Thamnophis eques megalops)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change? 

In the United States, this sub-species has been primarily known from 

central and southern Arizona, with a limited distribution in New 

Mexico; also known from Mexico (Rosen and Schwalbe 1988; USFWS 

2006). It is the only sub-species that occurs in the United States (Rosen 

and Schwalbe 1988). Across its range, observed at 40-2590 m (130-

8496 ft) in elevation (USFWS 2006). Most localities in which 

individuals were observed by Rosen and Schwalbe (1988) ranged from 

914-1524 m (3000-5000 ft).

Considered to be restricted to riparian areas, except when dispersing 

(USFWS 2006). In Arizona, found to be most abundant in “source-area 

wetlands” around cienegas, cienega-streams, and stock tanks (Rosen 

and Schwalbe 1988). In New Mexico, most observations of Thamnophis 

eques have been at a few shallow stock tanks with abundant shoreline 

vegetation (e.g., often with abundant cattails; Degenhardt and others 

1996). Rosen and Schwalbe (1988) also identified large river riparian 

woodlands and forests and streamside gallery forests (well-developed 

broadleaf deciduous riparian forests) as habitats. Cienegas are midelevation wetlands characterized by permanently saturated, highly 

organic, reducing soils (Hendrickson and Minckley 1984 as cited in 

USFWS 2006).

The northern Mexican gartersnake occurs, or potential habitat exists, on 

the following EMAs: Tumacacori, Santa Rita, and Huachuca (USFS 

2009). Projections of suitable climate for vegetation communities on all 

EMAs combined (Chapter 1) predicted declines in suitable climate for 

all plant community types, with the exception of increases of suitable 

climate for semi-desert grassland and small increases in Sonoran desert 

scrub (present in small amounts on the CNF).

Riparian habitats predicted to decline due to decreased water flows on 

average, increased fire frequency, and possibly changes to the flood 

regime (earlier peak flows).

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to 

change?

Non-breeding habitat is same as breeding habitat. See Habitat, 

Question 1.

2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

Dense bank and aquatic vegetation is considered an essential component

of suitable habitat (Rosen and Schwalbe 1988), and is particularly 

important for neonates (references in USFWS 2006). Individuals use 

riparian herbaceous vegetation for cover, thermoregulation, and 

foraging. Removal of vegetation for even one season has to potential to 

lead to extirpation of a population (Rosen and Schwalbe 1988). Seldom 

seen more than 15 m from permanent water; T. eques is closely tied to 

permanent water (Rosen and Schwalbe 1988).

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

non-breeding 

periods expected to 

change?

See Habitat, Question 3. 1
USDA Forest Service RMRS-GTR-273. 2012. 177

215

Habitat: Northern Mexican gartersnake (Thamnophis eques megalops)

Trait/Quality Question Background info. & explanation of score Points

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

No information (see Habitat, Question 3). 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to 

change? 

No information (see Habitat, Question 4). 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Most amphibians and reptiles move relatively little across their lifetime 

except when breeding (Vitt and Caldwell 2009). Rosen and Schwalbe 

(1988) reported that individuals are rarely seen >15 m from permanent 

water, “although it may occasionally wander overland.” 

1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

No information found indicating that individuals undergo seasonal 

movements involving additional habitats.

0

Physiology: Northern Mexican gartersnake (Thamnophis eques megalops)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions 

expected to 

change?

Northern Mexican gartersnakes are surface active at ambient temperatures 

between 22-33 °C (71-91 °F) and forage along banks of water bodies 

(USFWS 2006). Thermal preferendum for the Thamnophis genus appears to 

be near 30 °C (Rosen 1991). Not clear that physiological threshold would 

regularly be exceeded. Forages in water and in areas with vegetative cover.

0

2. Sex ratio Is sex ratio 

determined by 

temperature? 

In Vitt and Caldwell (2009), genetic sex determination was reported for the 

Colubridae family; i.e., temperature-dependent sex determination not 

known occur in this family.

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance 

events that result 

in direct 

mortality or 

reproductive 

failure expected 

to change?

Individuals occupying streams may be exposed to increased levels of 

flooding (proportionally greater streamflow in winter and early spring as 

snow melts earlier) which could increase mortality. Increase in frequency 

of heat waves is predicted for southwestern United States. We assumed

that snakes could survive short periods of high temperature by utilizing 

vegetative cover and/or standing water, even if foraging opportunities were 

reduced for several days.

1

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to 

change?

T. eques is active during the warm months of the year (Degenhardt and 

others 1996). The body temperature during the active season in Arizona of 

18 individuals averaged 27.26 °C (22-33 °C; Rosen 1991). Forages along 

watercourses; seeks shelter from predators in thick streamside vegetation 

or in the stream (Degenhardt and others 1996). In Chihuahua, Mexico, this 

sub-species had peak activity between 1000-1100 hours in summer (Van 

Devender and Lowe 1977). Swims above and below water while foraging 

or escaping. After summer rains that begin in late June, individuals were 

observed frequently on the road at night. Association with water suggests 

that daily activity period will not be limited as long as water is present.

1
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216

Physiology: Northern Mexican gartersnake (Thamnophis eques megalops)

Trait/Quality Question Background info. & explanation of score Points

However, reduced precipitation could reduce the length of seasonal 

activity periods by reducing water in pools/tanks, potentially leading to 

earlier retreats to hibernacula. 

5. Metabolic 

inhibition

Does this species 

possess an ability 

to reduce 

metabolic energy 

or water 

requirements?

Cycles of dormancy are common in amphibians and reptiles; hibernation 

(some refer to hibernation in ectotherms as “brumation”) is most likely 

primarily a response to cold temperatures and less so to a change in 

resource availability (Vitt and Caldwell 2009). While hibernating, activity 

mostly ceases, body temperature depends on temperature of the 

hibernation site, and physiological processes are reduced.

We assumed that burrows would be largely buffered from increased 

temperatures.

0

6. Survival 

during 

resource 

limitation

Does this species 

have lower 

energy 

requirements or 

possess the 

capacity to store 

energy or water 

in the long term?

Ectotherm. -1

7. Variable life

history

Does this species 

have alternative 

life history 

strategies to cope 

with variable 

resources or 

climate 

conditions?

No information found to suggest alternative life history strategies. 0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where 

reproduction is 

limited?

Males thought to mature at 2 years of age, and females at 2-3 years (Rosen 

and Schwalbe 1988). Only ~50% of the females bear young each year 

(Rosen and Schwalbe 1988). Follicular enlargement begins in autumn for the 

next year’s litter (Rosen and Schwalbe 1988). No longevity record for T. 

eques in Snider and Bowler (1992). Low survivorship of neonates and 

possibly yearlings was observed in Arizona (Rosen and Schwalbe 1988).

Periods of extreme reductions in rainfall may last 5 years, which could 

reduce ponds and other water sources on which individuals depend for 

breeding. If these conditions eliminate breeding, we expected that most of 

the population would not survive longer than the periods of limited 

reproduction given: (1) the time to maturity, (2) that only about half of the 

females breed every year, and (3) individuals are probably not particularly 

long-lived.

1

Phenology: Northern Mexican gartersnake (Thamnophis eques megalops)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Temperature is an important cue in reptiles (Licht 1972). T. eques is 

active during the warm months of the year (Degenhardt and others 

1996).

1

2. Event 

timing

Are activities 

related to species’ 

fecundity or 

Follicular enlargement begins in autumn for the next year’s litter (Rosen 

and Schwalbe 1988). Ovulation begins in late March or early April 

(Rosen and Schwalbe 1988); the authors indicate that mating probably 

1
USDA Forest Service RMRS-GTR-273. 2012. 179

217

Phenology: Northern Mexican gartersnake (Thamnophis eques megalops)

Trait/Quality Question Background info. & explanation of score Points

survival tied to 

discrete events that 

are expected to 

change? 

occurs in fall and very likely also occurs in early spring. Timing of 

temperature increases in late winter/early spring and rainfall patterns are 

likely important to this species.

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

Cues and critical resources (e.g., food) expected to be closely related in 

time and space.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

In Arizona, 8 females produced 7-26 neonates (averaged 13.6; Rosen 

and Schwalbe 1988). Females typically move to warm 

microenvironments a few meters from water and give birth from early 

June to early July, with ~50% of the females bearing young each year 

(Rosen and Schwalbe 1988). 

1

Biotic interactions: Northern Mexican gartersnake (Thamnophis eques megalops)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Frogs, tadpoles, and fish are dominant prey; also lizards and mice and 

likely earthworms (Rosen and Schwalbe 1988). The most important prey 

were considered to be leopard frogs, Woodhouse’s toads, Gila and 

roundtail chubs, and very likely other small fish, especially Gila

topminnow (Rosen and Schwalbe 1988). Substantial numbers of 

individuals were only observed where anurans and prey fish were 

abundant. The authors thought that native prey species appear to play a 

larger role in the ecology of this sub-species than for other striped 

gartersnakes in Arizona. Forages using a variety of behaviors including 

ambush (both in water and on land), active foraging in riffles, vegetation 

mats and occasionally open water, and it capitalizes on transitory 

concentrations of prey (Rosen and Schwalbe 1988).

Diet consists mostly of amphibians (adult and larval forms) and fishes 

(adult and juvenile forms); and may also include tree frogs, deer mice, 

lizards (Aspidoscelis and Sceloporus, larval tiger salamanders), and 

leeches (USFWS 2006). In one study in Mexico, differences in diet were 

found—large snakes fed mainly on fish, frogs, and salamander larvae, 

and leeches, and small snakes fed mostly on earthworms and leeches 

(Garcia and Drummond 1988).

Overall, it appears that a variety of prey species are consumed. However, 

the northern Mexican gartersnake appears especially vulnerable to the 

loss of native prey species, such as leopard frogs (multiple references in 

USFWS 2006) that are expected to be vulnerable to climate change. 

USFWS (2006) stated “if an area is solely comprised of nonnative fish, 

the northern Mexican gartersnake may be faced with nutritional stress or 

face starvation.” Thus a score of “1” was assigned to this question.

1

2. Predators Are important 

predator 

populations 

Rosen and Schwalbe (1988) considered that bullfrogs might influence 

populations of gartersnakes through predation. The authors indicated that 

during surveys in Arizona, “Mexican garter snakes were rare, and in 

-1
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218

Biotic interactions: Northern Mexican gartersnake (Thamnophis eques megalops)

Trait/Quality Question Background info. & explanation of score Points

expected to 

change?

some localities possible extirpated, where bullfrogs were abundant.” 

Authors also conjectured that bias toward large adults at the San 

Bernardino NWR was due to predation of small snakes by bullfrogs.

A variety of predators is thought to prey on northern Mexican 

gartersnakes, including birds of prey, other snakes, wading birds, 

raccoons, skunks, and coyotes (Rosen and Schwalbe 1988). Bullfrog and 

crayfish are thought to be the biggest threat to northern Mexican 

gartersnakes (references in USFWS 2006).

Overall, there are a suite of predators. However, USFWS (2006) 

indicated that the expansion of nonnative predators (bullfrogs, crayfish 

and green sunfish) is the primary cause of decline in this sub-species in 

southeastern New Mexico. These aquatic predators of the northern 

Mexican gartersnake are likely to be vulnerable to climate change as 

well. Thus, a score of “-1” was assigned.

3. Symbionts Are populations of 

symbiotic species 

expected to 

change?

No information found regarding symbiotic relationships. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to 

change? 

Disease in this sub-species has not been identified as a major threat, but 

little information about diseases in snakes, in general, exists (USFWS 

2006). Batrachochytrium (fungus causing chytrid infections) has not 

been reported on reptilian hosts in the wild (USFWS 2006). Individuals 

in Mexico documented to be host to various helminth parasites but no 

discussion of impacts from these parasites (Jimenez-Ruiz and others 

2002).

0

5. Competitors Are populations of 

important 

competing species 

expected to 

change?

Nonnative species (e.g., bullfrogs, nonnative fish, and crayfish) compete 

with northern Mexican gartersnake for prey (USFWS 2006). Crayfish 

alter the abundance and structure of aquatic and semi-aquatic vegetation 

used by gartersnakes (USFWS 2006). These aquatic species are likely to 

be vulnerable to climate change as well. Marcy’s checkered gartersnake 

(T. marcianus marcianus) is a semi-terrestrial species; it may be outcompeting northern Mexican gartersnakes at San Bernardino National 

Refuge in southern Arizona (Rosen and others 2001 as cited in USFWS 

2006).

Thus, we assigned a score of “0” because non-native aquatic competitors 

are likely to decrease but Marcy’s checkered gartersnake may increase.

0

Literature Cited

Degenhardt, W.G., C.W. Painter, and A.H. Price. 1996. The amphibians and reptiles of New Mexico. 

Albuquerque: University of New Mexico Press.

Garcia, C.M., and H. Drummond. 1988. Seasonal and ontogenetic variation in the diet of the Mexican 

garter snake, Thamnophis eques, in Lake Tecosomulco, Hidalgo. Journal of Herpetology 22:129-134.

Jimenez-Ruiz, F.A., L. Garcia-Prieto, and G. Perez-Ponce de Leon. 2002. Helminth infracommunity 

structure of the sympatric garter snakes Thamnophis eques and Thamnophis megalongaster from the 

Mesa Central of Mexico. Journal of Parasitology 88:454-460.

Licht, P. 1972. Environmental physiology of reptilian breeding cycles: Role of temperature. General and 

Comparative Endocrinology Supplement 3:477-488.

Rosen, P.C. 1991. Comparative field study of thermal preferenda in garter snakes (Thamnophis). Journal 

of Herpetology 25:301-312.

Rosen, P.C., and C.R. Schwalbe. 1988. Status of the Mexican and narrow-headed garter snakes 

(Thamnophis eques megalops and Thamnophis rufipunctatus) in Arizona. Unpublished report from 
USDA Forest Service RMRS-GTR-273. 2012. 181

219

Arizona Game and Fish Department, Phoenix, AZ, to U.S. Fish and Wildlife Service, Albuquerque, 

NM. 88 p.

Snider, A.T., and J.K. Bowler. 1992. Longevity of reptiles and amphibians in North American 

collections. Second edition. Herpetological Circular No. 21. Society for the Study of Amphibians and 

Reptiles. 40 p.

U.S. Fish and Wildlife Service [USFWS]. 2006. 12-Month finding on a petition to list the Northern 

Mexican Gartersnake (Thamnophis eques megalops) as threatened or endangered with critical habitat. 

Federal Register 71:56227-56256.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Van Devender, T.R., and C.H. Lowe, Jr. 1977. Amphibians and reptiles of Yepómera, Chihuahua, 

Mexico. Journal of Herpetology 11:41-50.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.

Habitat: Arizona ridge-nosed rattlesnake (Crotalus willardi willardi)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change? 

In the United States, this sub-species occurs in southern Arizona 

between 4000 and 9000 ft in elevation and has been reported in the 

Huachuca, Santa Rita, Canelo, Patagonia, and Whetstone Mountains 

(Degenhardt and others 1996; Brennan 2008). Often occurs in Madrean 

evergreen woodland, in or near drainages that contain abundant canopy 

cover and leaf litter. In the Huachuca Mountains, the most frequently 

occurring perennial plants within 2.5 m of individuals when they were 

captured were bullgrass (Muhlenbergia emersleyi), Mexican pinyon 

(Pinus cembroides), Emory oak (Quercus emoryi), and Arizona white 

oak (Q. arizonica; McCrystal and others 1996). In the Patagonia 

Mountains, they were silverleaf oak (Q. hypoleucoides), Mexican 

pinyon, squaw bush (Rhus trilobata), and bullgrass. Rado and Rowlands 

(1981) found an individual under bark near a decomposing log where 

dominant vegetation included Arizona sycamore, Mexican pinyon, one 

seed juniper, Arizona ash, Emory oak, and Mexican blue oak.

Degenhardt and others (1996) called Crotalus willardi obscurus in New 

Mexico a “montane generalist...occurring mostly above 1800m.” In 

New Mexico and northern Mexico, most have been collected “in and 

along steep rocky canyons with intermittent streams or on exposed talus 

slopes.” Authors indicated that dominant vegetation where C .w. 

obscurus occurs includes various species of oaks, Apache and 

Chihuahuan pine, alligator juniper, Arizona cypress, Arizona madrone, 

Manzanita, and various grasses.

Arizona ridge-nosed rattlesnakes occur, or potential habitat exists for 

this species, on the following EMAs: Santa Rita, Huachuca, and 

Whetstone (USFS 2009). Projections of suitable climate for vegetation 

communities (Chapter 1) predicted declines in suitable climate for 

Madrean forest and woodland, Madrean conifer forest, and plains 

grassland, with increases of suitable climate for semi-desert grassland.

Overall, we expected that projected reductions in pine-oak woodland 

habitats (from increased aridity, drought, and high intensity fires) will 

reduce breeding habitat.

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonSame as breeding habitat; See Habitat, Question 1. 2
182 USDA Forest Service RMRS-GTR-273. 2012.

220

Habitat: Arizona ridge-nosed rattlesnake (Crotalus willardi willardi)

Trait/Quality Question Background info. & explanation of score Points

breeding activities 

by this species 

expected to 

change?

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

No information found to indicate existence of specific habitat 

components for breeding.

0

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

non-breeding 

periods expected to 

change?

Requires over-wintering sites. McCrystal and others (1996) conducted a 

study in autumn and indicated that Arizona ridge-nosed rattlesnakes are

semi-fossorial and are “generalized in the cover they choose when 

opportunities are varied.” The authors indicated that they seemed to 

prefer burrows or holes in the ground, but that they have been observed 

to use holes under rocks, holes in rock piles (possibly leading to holes in 

the ground) and occasionally clumps of bunch grass. Refuge was rarely 

sought under dead logs. In areas with less rock cover, individuals 

seemed to use bunchgrass and burrow more frequently. Not clear to 

authors whether bunchgrass clumps were used in winter; no feces or 

shed skins were found there as at other refugia.

In Mexico, ridge-nosed rattlesnakes have been found over-wintering 40-

46 cm deep in talus (Degenhardt and others 1996).

Availability of such holes/burrows/rock piles not expected to change as a 

direct result of climate change.

0

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

No information found on habitat quality and reproduction. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to 

change? 

No information found on habitat quality and survival. 0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Most amphibians and reptiles move relatively little during their lifetime 

except when breeding (Vitt and Caldwell 2009). Smith and others (2001) 

found that 3 radio-tagged C. w. obscurus had a daily activity area of 5.6-

74.4 m2

 during May-July 1997. Six individuals of C. w. willardi were 

found 0-105 m from where originally located across 6-1097 days 

(McCrystal and others 1996)

1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

No information found to suggest that Arizona ridge-nosed rattlesnakes

undergo seasonal movements.

0
USDA Forest Service RMRS-GTR-273. 2012. 183 221

Physiology: Arizona ridge-nosed rattlesnake (Crotalus willardi willardi)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

In Mexico, ridge-nosed rattlesnakes have been found basking both at air 

temperatures of 6-9 °C (43-48 °F) in the shade and 26 °C (79 °F) in the 

sun (Degenhardt and others 1996). Body temperatures of C. w. willardi

in the Huachuca and Patagonia Mountains during fall surveys averaged 

24.2 °C (McCrystal and others 1996).

Armstrong and Murphy (1979) indicated that this sub-species appears 

to prefer the “more humid canyon bottoms of pine-oak habitats as 

opposed to the arid slopes where C. lepidus and C. pricei are common.” 

The authors indicated that although this preference seemed to exist, an 

individual was also observed on an east-facing slope in scrub oak. In 

Sonora, Mexico, individuals were found to be common in rocky stream 

beds where pools of water stood following summer rains; two species 

of Sceloporus were common here (thought to be important prey). 

Authors thought this sub-species was more active on warm, humid days 

when there was intermittent sunlight, particularly before and after rain 

showers in the afternoons when the temperature was 24-29 °C.

McCrystal and others (1996) indicated that this sub-species “does not 

exhibit regular surface activity when conditions are hot and dry, but 

will be found active during cool times, providing there is access to the 

sun for basking. We have found them moving in the rain, and have seen 

them basking in every month of the year, including basking on dry 

sunlit rocks less than 3 meters from snow.”

We chose the score of “1” due to the potential that Arizona ridge-nosed 

rattlesnakes are sensitive to higher temperatures.

1

2. Sex ratio Is sex ratio 

determined by 

temperature? 

In Vitt and Caldwell (2009), genetic sex determination is reported for 

the Viperidae family; i.e., temperature-dependent sex determination not 

known occur in this family.

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern United 

States. We assumed that snakes could survive short periods of high 

temperature by utilizing cover; even if foraging opportunities were 

reduced for several days (see also Physiology, Question 1). Eight radiotagged rattlesnakes (Crotalus spp.) exposed to low-intensity fire survived, 

and were in subterranean retreats following the fire (Smith and others 

2001), suggesting the ability to escape high intensity temperatures. 

0

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Ridge-nosed rattlesnakes are primarily diurnally active but occasionally 

they are crepuscular or occasionally nocturnally active at lower 

elevations (Brennan 2008). Not active during late fall and winter.

Possible that seasonal activity period may increase if non-winter 

months are warmer for longer periods, but may be offset if temperatures 

during warmest part of day become hotter. Score of “1” reflects 

information that activity associated with intermittent sunlight, and 

before and after rain showers at moderate temperatures (see Physiology, 

Question 1), suggesting that Arizona ridge-nosed rattlesnakes may be 

more sensitive to higher temperatures than other reptiles.

1

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Cycles of dormancy are common in amphibians and reptiles, and 

hibernation is most likely primarily a response to cold temperatures and 

less so to a change in resource availability (Vitt and Caldwell 2009). 

While hibernating, activity mostly ceases, body temperature depends on 

temperature of the hibernation site, and physiological processes are 

reduced. Such inactivity is called brumation in ectotherms (not 

hibernation).

Inactive in winter. In Mexico, ridge-nosed rattlesnakes have been found 

over-wintering 40-46 cm deep in talus (Degenhardt and others 1996). 

0
184 USDA Forest Service RMRS-GTR-273. 2012.

222

Physiology: Arizona ridge-nosed rattlesnake (Crotalus willardi willardi)

Trait/Quality Question Background info. & explanation of score Points

We assumed that wintering sites would be largely buffered from 

increased temperatures.

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Ectotherm. -1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

Females appear to reproduce every other year or at greater intervals 

(Holycross and Goldberg 2001), but not clear that this is a benefit to 

variable resources or climate conditions.

0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Little information on survivorship in the wild. The longevity record for 

captive C. w. willardi is 21 years (Bowler1975); 34 longevity records for 

Crotalus spp. in captivity range 3 years to 3-30 years (Bowler1975), 

suggesting that this genus may have relatively long lifespans 

(Bowler1975).

Periods of extreme reductions in rainfall may last 5 years. If these 

conditions reduce resources to the point that Arizona ridge-nosed 

rattlesnakes have insufficient resources for breeding, but conditions 

recover after, we assumed it is likely that sufficient numbers of 

individuals would survive long enough to breed once conditions improve.

-1

Phenology: Arizona ridge-nosed rattlesnake (Crotalus willardi willardi)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Temperature is an important cue in reptiles (Licht 1972). Temperature 

may be an important cue for departing and returning to over-wintering 

sites.

1

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

See Phenology, Question 1.

The length of the cold season is an important constraint on how long 

the reproductive season lasts in reptiles (Vitt and Caldwell 2009). 

Increased temperatures may alter the length of the breeding season.

Young (2-9) are born from late July-August (Holycross and Goldberg 

2001). This coincides with the start of summer rains and the appearance 

of juvenile Sceloporus, a prey species; it is possible that parturition is 

timed to coincide with the increase of prey availability. Ovulation and 

fertilization probably occur in early spring, with a 4-5-month gestations 

period after that. Copulation occurs in mid-summer to early fall. 

However, reproduction appears to biennial or longer. 

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

Cues and critical resources (e.g., food) expected to be closely related in 

time and space.

-1
USDA Forest Service RMRS-GTR-273. 2012. 185

223

Phenology: Arizona ridge-nosed rattlesnake (Crotalus willardi willardi)

Trait/Quality Question Background info. & explanation of score Points

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Individuals mate in summer or fall, and young are born the following 

summer (Brennan 2008). Females appear to produce young every other 

year or at longer intervals (Holycross and Goldberg 2001).

1

Biotic interactions: Arizona ridge-nosed rattlesnake (Crotalus willardi willardi)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Brennan (2008) indicated that this sub-species consumes mostly lizards, 

mice and centipedes, occasionally birds and scorpions. McCrystal and 

others (1996) concluded that this sub-species appears to be a food 

generalist.

In a study of C. w. obscurus, adults fed primarily on small mammals 

(62.3%), lizards (26.4%) and occasionally passerine birds (9.4%). 

Peromyscus spp. comprised 64.9% of the small mammals consumed 

and Sceloporus spp. for 68.4% of lizards. Juveniles consumed a diet of 

57% lizards and 71% of these were identified as Sceloporus spp.; 

centipedes constituted 33% of the diet (Holycross and others 2001a).

Multiple prey species are consumed, although not as wide of a variety 

of prey as some species.

0

2. Predators Are important 

predator populations 

expected to change?

Little information on predators exists (Holycross and others 2001b). 

One observation of a snake carcass (C. w. obscurus) was believed to 

have been preyed upon by a Mexican spotted owl or a red-tailed hawk 

(Holycross and others 2001b).

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found that indicates important symbiotic relationships. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Little information. McAllister and others (1996) indicated theirs is the 

first published report on parasites of C. willardi obscurus. The authors 

found oocysts and sporocysts of Sarcocystis spp. (protozoans) in the 

feces of individuals in Mexico. No information on whether the parasite 

was causing visible illness in the individuals snakes. Salmonella has 

been reported in captive populations of C. willardi (Grupka and others 

2006); not clear whether this might apply to wild individuals.

0

5. Competitors Are populations of 

important competing 

species expected to 

change?

No information found on competitors. 0

Literature Cited

Armstrong, B.L., and J.B. Murphy. 1979. The natural history of Mexican rattlesnakes. University of 

Kansas Museum of Natural History Special Publication No. 5. vii + 88 p.

Bowler, J.K., 1975. Longevity of reptiles and amphibians in North American collections as of 1 

November, 1975. Society for the Study of Amphibians and Reptiles, Miscellaneous Publications, 

Herpetological Circular 6:1-32.

Brennan, T.C. 2008. Ridge-nosed Rattlesnake (Crotalus willardi). Online field guide to the reptiles and 

amphibians of Arizona. Available: http://www.reptilesofaz.org/Snakes-Subpages/h-c-willardi.html.
186 USDA Forest Service RMRS-GTR-273. 2012.

224

Degenhardt, W.G., C.W. Painter, and A.H. Price. 1996. The amphibians and reptiles of New Mexico. 

Albuquerque: University of New Mexico Press.

Grupka, L.M., E.C. Ramsay, and D.A. Bemis. 2006. Salmonella surveillance in a collection of 

rattlesnakes (Crotalus spp.). Journal of Zoo and Wildlife Medicine 37:306-312.

Holycross, A.T., and S.R. Goldberg. 2001. Reproduction in northern populations of the ridgenose 

rattlesnake, Crotalus willardi (Serpentes: Viperidae). Copeia 2001: 473-481.

Holycross, A.T., C.W. Painter, D.G. Barker, and M.E. Douglas. 2001a. Foraging ecology of the 

threatened New Mexico ridge-nosed rattlesnake (Crotalus willardi obscurus). In: Schuett, G.W., M. 

Hoggren, M.E. Douglas, and H.W. Greene, eds. Biology of the Vipers. Eagle Mountain, UT: Eagle 

Mountain Publishing: 243-251.

Holycross, A.T., L.K. Kamees, and C.W. Painter. 2001b. Observations of predation on Crotalus willardi

obscurus in the Animas Mountains, New Mexico. Southwestern Naturalist 46:363-364.

Licht, P. 1972. Environmental physiology of reptilian breeding cycles: Role of temperature. General and 

Comparative Endocrinology Supplement 3:477-488.

McAllister, C.T., S.J. Upton, D.G. Barker, and C.W. Painter. 1996. Sarcocystis sp. (Apicomplexa) from 

the New Mexico ridgenose rattlesnake, Crotalus willardi obscurus (Serpentes: Viperidae) from Sonora, 

Mexico. Journal of the Helminthological Society of Washington 63:128-130.

McCrystal, H.K., C.R. Schwalbe, and D.F. Retes. 1996. Selected aspects of the ecology of the Arizona 

ridge-nosed rattlesnake (Crotalus willardi willardi) and the banded rock rattlesnake (Crotalus lepidus 

klauberi) in Arizona. Final Report. Arizona Game and Fish Department. Heritage Grant IIPAM 192304. 

Submitted to Heritage Program, Arizona Game and Fish Department, Phoenix, AZ. September 13, 

1996.

Rado, T.A., and P.G. Rowlands. 1981. A range extension and low elevation record for the Arizona ridgenosed rattlesnake (Crotalus w. willardi). Herpetological Review 12:15.

Smith, L.J., A. T. Holycross, C.W. Painter, and M.E. Douglas. 2001. Montane rattlesnakes nd prescribed 

fire. Southwestern Naturalist 46:54-61.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.

Habitat: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change?

Tiger salamanders overall have a wide distribution, but this sub-species 

is historically only known from Santa Cruz and Cochise counties and 

currently occurs only in the San Rafael Valley (Storfer and others 

2004). The San Rafael Valley consists of plains grassland and Madrean 

evergreen woodland (Collins and others 1988).

Across their range, tiger salamanders tend to occur in grasslands, 

savannahs, and woodland edges (Lannoo and Phillips 2005). Terrestrial 

adults of this sub-species utilize grassland habitats and adjacent slopes 

in the San Rafael Valley (Brooks and Rorabaugh 1997). Actual 

breeding is aquatic (affect of climate change on water sources covered 

in Habitat, Question 3), but terrestrial adults move from surrounding 

uplands they use for over-wintering to access breeding areas.

Habitat for the Sonoran tiger salamander occurs only on the Huachuca 

EMA (USFS 2009). Climate change projections for vegetation 

communities (Chapter 1) on the Huachuca EMA predicted declines in 

suitable conditions for Madrean forest and woodland, Madrean conifer 

0
USDA Forest Service RMRS-GTR-273. 2012. 187

225

Habitat: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

forest, and Plains grassland, and increases in suitable conditions for 

semi-desert grassland.

Increased grasslands would lead to an increase in terrestrial habitat, 

although decline of Madrean oak woodland would constitute a loss, 

which could result in no net gain in habitat area.

2. Area and 

distribution: 

non-breeding

Is the area or location 

of the associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Same as Habitat, Question 1. 0

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected to 

change? 

Breeding in tiger salamanders is aquatic (Lannoo and Phillips 2005), so 

permanent or semi-permanent water sources are required. Utilizes nonflowing water (Degenhardt and others 1996). Water sources must 

persist seasonally at least long enough for larvae to metamorphose into 

terrestrial forms if populations are to persist. Larval stage lasts at least 

10 weeks but can be longer; varies with environmental factors (e.g., 

food, temperature, salamander density, etc.). Some larvae develop into 

terrestrial adults, a morph that lacks gills; others develop into gilled 

aquatic adults (referred to by various names including branchiate 

adults, neotenic adults, and paedomorphs; Lannoo and Phillips 2005). 

Larvae may not metamorphose in their first year and instead overwinter in permanent water sources (USFWS 2002).

All known extant and historical aquatic populations are restricted to the 

cattle tanks (human-made earthen stock ponds) or impounded cienegas 

with 31 km of Lochiel, Arizona (Brooks and Rorabaugh 1997). 

Historically probably bred in springs, natural cienegas or possibly 

backwater pools (Brooks and Rorabaugh 1997). Some ranchers have 

maintained water in cattle ponds to support tiger salamanders (Snyder 

1988 as cited in USFWS 2002).

In the San Rafael Valley, many ponds that contain salamanders do not 

have aquatic or bank-line vegetation; thus, this appears not to be 

required for presence of this sub-species (USFWS 2002).

Presence of ponds expected to decline with increased aridity. Several 

stock ponds went dry during droughts in 1994 and 1996 (Brooks and 

Rorabaugh 1997). 

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

Year-round water is required by aquatic morphs (neotenic adults) and 

larvae that have not yet undergone metamorphosis. Collins and others 

(1988) noted that only ~17-40% of animals actually metamorphose to 

terrestrial form each year based on data from Bodie Tank in San 

Raphael Valley. Neotenic adults may not be able to undergo 

metamorphosis when threatened by drought (Lannoo and Phillips 

2005). Juveniles may stay near wet areas and feed, or may move to 

upland areas to burrow (Lannoo and Phillips 2005).

Note that there is often significant, but naturally occurring, larval 

mortality in tiger salamanders that breed in semi-permanent water 

sources when they dry each year, as is often the case with amphibians 

(Lannoo and Phillips 2005), yet populations persist. No indication that 

neotenic adults can burrow into mud and aestivate if ponds dry (Lannoo 

and Phillips 2005); thus, if they cannot metamorphose before their

water source dries they are subject to mortality. Sub-adult tiger 

salamanders have been observed burrowing in mud cracks when a 

cattle tank dried up (Webb 1969 as cited in Degenhardt 1996 and 

others). Furthermore, occasional drying of ponds reduces predator 

1
188 USDA Forest Service RMRS-GTR-273. 2012.

226

Habitat: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

populations (fish, bullfrogs), which could ultimately benefit breeding 

and non-breeding Sonoran tiger salamanders.

Overall, if the percentage of individuals that Collins and others (1988) 

observed as undergoing metamorphosis at Bodie Tank is indicative of 

individuals across the population of this sub-species, we assumed that 

year-round ponds are important to the persistence of the population.

Terrestrial adults require deep friable soils for burrowing (they can dig 

their own burrows, but often are associated with mammal burrows; 

references in Lannoo and Phillips 2005). However, no expected 

significant reduction in friable soils under climate change.

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

Little information. In field enclosures during summer months, 

Holomuzki (1986) found that larval survivorship and growth were 

generally greater in vegetated shallows than in enclosures in the 

limnetic zone (well-lit surface waters away from shore); this variation 

was correlated with lower food levels, lower temperatures, and lower 

oxygen in deeper limnetic areas. Further, the authors found significant 

variation in fitness among years despite the fact that food, temperature, 

and oxygen remained relatively constant, suggesting that other 

unmeasured factors were important.

0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change?

Little information; see Habitat, Question 5. 0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Terrestrial adults move from over-wintering sites in uplands to wet 

areas for breeding (Lannoo and Phillips 2005). One tagged male moved 

162 m to an upland site (Semlitsch 1983a as cited in Lannoo and 

Phillips 2005). Brooks and Rorabaugh (1997) noted an account of a 

single terrestrial salamander being found at a location that was probably 

1 km from an aquatic site. In other Ambystoma spp., adults usually 

return to breed in the same ponds where they hatched (USFWS 2002). 

Considered to have low ability to disperse.

1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Terrestrial adults move from over-wintering sites in uplands to wet 

areas for breeding (Lannoo and Phillips 2005). In some populations of 

tiger salamander, newly metamorphosed individuals stay near aquatic 

habitat rather than migrating into uplands (Lannoo and Phillips 2005). 

However, these transitional areas are not expected to be substantially 

different from wintering areas.

0

Physiology: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

This sub-species is tolerant of a wide temperature range; temporary 

ponds can range in temperature across the year from <5 °C to 30 °C; 

temperature in terrestrial environments can range from below 0 °C to 

>35 °C (USFWS 2002). We assumed that water or air temperature will 

not exceed thresholds. Standing water expected to become less 

available, but this is covered in Habitat section.

Decrease in precipitation and increased evaporation (due to increased 

temperatures) may reduce the amount of moisture available for adults to 

move between breeding ponds and over-wintering areas, and/or survive 

during over-wintering periods (increases probability of desiccation). 

1
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Physiology: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

2. Sex ratio Is sex ratio 

determined by 

temperature? 

Vitt and Caldwell (2009) indicated that salamanders do not experience 

temperature-dependent sex determination. 

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Increase in frequency of heat waves is predicted for southwestern 

United States. Overall, not clear that heat waves during summer would 

reduce survival and reproduction due to high probability that terrestrial 

forms would be in or near water at this time of year.

0

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Reduced precipitation could reduce the length of seasonal activity 

periods by reducing water in pools/tanks and leading to earlier retreats 

to hibernacula. 

1

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Cycles of dormancy are common in amphibians and reptiles; 

hibernation (some refer to hibernation in ectotherms as “brumation”) is 

most likely primarily a response to cold temperatures and less so to a 

change in resource availability (Vitt and Caldwell 2009). While

hibernating, activity mostly ceases, body temperature depends on 

temperature of the hibernation site, and physiological processes are 

reduced.

Terrestrial adults occupy burrows during winter (Lannoo and Phillips 

2005). We assumed that burrows would be largely buffered from 

increased temperatures.

0

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Ectotherm. -1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

The presence of both aquatic and terrestrial adult forms is considered a 

benefit in that populations can survive the non-breeding season on land 

in burrows, and thus do not depend on ponds during the non-breeding 

season.

Tiger salamanders have a cannibal morph larvae, which may eat 

conspecifics among other prey and have proportionally large heads and 

teeth (Lannoo and Phillips 2005). The authors did not indicate this as a 

sub-species where this morph has been documented in wild 

populations, but do note that it has been induced in laboratory 

conditions. Cannibal morphs are not observed in all years in those 

populations in which they are known to occur; conspecific density 

appears to trigger their presence (references in Lannoo and Phillips 

2005). Five individuals of this morph have been observed out of 

thousands of individuals in the San Rafael Valley (USFWS 2002).

-1

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Little information on this sub-species. Branchiate adults of the subspecies A. t. nebulosum have survived for up to 8 years in captivity 

(USFWS 2002). Based on 150 individuals of this same sub-species 

taken from the wild, none were estimated to be older than 6 years 

(USFWS 2002). In the eastern tiger salamander, most individuals die 

before they can breed a second time (Church and others 2007).

Periods of extreme reductions in rainfall may last 5 years, which can 

1
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Physiology: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

reduce ponds and other water sources on which individuals depend for 

breeding. If these conditions eliminate breeding, most of the population 

would not survive longer than the periods of limited reproduction.

Phenology: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Amphibians, in general, respond to temperature and moisture cues in 

the timing of breeding (Carey and Alexander 2003). This sub-species 

has been known to breed as early as January and as late as early May; 

rarely breed after monsoon rains in July and August (USFWS 2002). 

Migrations to breeding areas from wintering sites are triggered by 

warm spring rains in northern wetlands (references in Lannoo and 

Phillips 2005); considered possible that temperature triggers migration 

in Arizona (given that rains are mostly in winter and summer). Wet or 

rainy weather may stimulate terrestrial activity (Degenhardt and others 

1996).

1

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Known to breed as early as January and as late as early May; rarely 

breed after monsoon rains in July and August (USFWS 2002). Eggs 

hatch 2-4 weeks after being laid; eggs develop more quickly in warm 

water than in cold water (USFWS 2002). Possible that eggs will 

develop more quickly under climate change, but unclear how much 

warmer the water in ponds will be.

In as few as 2 months, larvae of this sub-species can develop into the 

size required to metamorphose (>45 mm snout-vent length) into 

terrestrial adults; in the San Rafael Valley, however, because many of 

the sites hold water year-long, larvae often do not metamorphose as 

quickly as this, or they develop into branchiate adults instead of 

metamorphosing (USFWS 2002). In some cases, branchiate adults can 

metamorphose into terrestrial morphs if their pond starts to dry up, but 

these individuals often do not successfully complete metamorphosis 

(USFWS 2002).

The timing of metamorphosis in tiger salamanders in high elevations of 

the Rocky Mountains was related to the temperature of the water (Bizer

1978 as cited in Degenhardt and others1996).

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

Individuals are non-migratory. Cues and critical resources (e.g., food) 

expected to be closely related in time and space.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

This sub-species has been known to breed as early as January and as 

late as early May; rarely breed after monsoon rains in July and August 

(USFWS 2002). Breeding season is short in tiger salamanders, and 

males typically arrive at ponds before females (Degenhardt and others 

1996). Allison and others (1994) reported an opportunistic second 

breeding attempt in A. t. nebulosum following the drying and re-filling 

of a lake in late summer. Not clear that this pattern is typical in either 

sub-species.

1
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Biotic interactions: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Tiger salamander larvae are size-selective feeders (being gape-limited) 

but are generalists, consuming zooplankton, ostracods, aquatic insect 

larvae and adults, mollusks, oligochaetes, leeches, crayfish, anuran 

tadpoles, small fish, and in the case of cannibalistic morph, conspecifics 

(references in Lannoo and Phillips 2005). The diet of neotenic adults 

typically is similar to that of large larvae (references in Lannoo and 

Phillips 2005). Terrestrial adults consume a variety of invertebrates 

associated with soil and soil surfaces, such as annelids and insects 

(larvae and adults); also reported to consume small vertebrates (e.g., 

field mice, lizards). Non-breeding terrestrial adults may forage in 

wetlands lacking fish (Lannoo and Phillips 2005).

Overall, tiger salamanders consume a variety of prey.

0

2. Predators Are important 

predator populations 

expected to change?

Tiger salamanders have a variety of predators (predators consume eggs, 

larvae, and adults, see references in Lannoo and Phillips 2005), 

including caddis flies, dragonfly naiads, predaceous diving beetles, 

giant water bugs, newts, salamanders, snakes, a wide range of birds, 

and a variety of mammals (e.g., bobcats, raccoons, and coyotes). 

Predation occurs despite terrestrial individuals producing secretions 

along the dorsal surface of the tail that contain neurotoxins. Neotenic 

adults tend to require fishless water sources (Lannoo and Phillips 

2005). In San Rafael Valley, exotic fish tend to eliminate salamanders 

(Collins and others 1988). Bullfrogs were introduced into the SRV; 

bullfrog larvae may eat eggs of tiger salamanders, and adult bullfrogs 

may prey on larval salamanders (Collins and others 1988). USFWS 

(2002) indicated that many ponds in San Rafael Valley have not 

maintained consistently high densities of bullfrogs and their effect on 

this sub-species is unclear.

Overall, there is a suite of predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No information found to indicate existence of important symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change?

Disease is considered one of the biggest threats to this sub-species 

(Brooks and Rorabaugh 1997). Collins and others (1988) reported 

mortality from an undiagnosed disease whose symptoms were similar 

to Aeromonas spp. infection (red leg disease) that killed all aquatic 

individuals in at least three sites in the San Rafael Valley in 1985. 

Epizootics are not uncommon in tiger salamanders, including this subspecies (Jancovich and others 1997). Further study identified a virus as 

the primary pathogen involved in epizootics, and was named ATV 

(Ambystoma tigrinum virus; Jancovich and others 1997). The virus is 

highly infectious. Recolonization following die-offs has been observed 

in the San Rafael Valley. Little information found on triggers for 

epizootics involving this virus.

Chytrid fungal infections known to occur in this sub-species although 

minimal symptoms were observed in many individuals of this subspecies during a laboratory study (Davidson and others 2003). There is 

conflicting evidence about whether changes in climate are affecting 

susceptibility of amphibians to chytrid fungal infections (Lips and 

others 2008).

Recurring mass mortality of tiger salamanders has been observed in an 

oligotrophic lake in Utah with the proximate cause of death caused by 

epizoic bacteria (Acinetobacter spp.; Worthylake and Hovingh 1989). 

The authors suggested that high bacteria levels seemed likely due to 

high levels of nitrogen from atmospheric sources and from sheep.

Stress can induce outbreaks of red-leg disease in tiger salamanders; 

0
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Biotic interactions: Sonoran tiger salamander (Ambystoma tigrinum stebbinsi)

Trait/Quality Question Background info. & explanation of score Points

e.g., heavy siltation of a pond associated with a nearby construction 

project leading to zooplankton crash was thought to be related to the 

only outbreak of this disease noted in a population in the Midwest 

(Lannoo and Phillips 2006). Parasitic nematodes occur in tiger 

salamanders (Lannoo and Phillips 2005). Leeches can infect some 

populations of tiger salamanders; effects of leeches on Ambyostoma 

tigrinum nebulosum were unclear, although they have been reported to 

cause significant mortality in larvae in other amphibian populations 

(Holomuzki 1986).

Not clear that climate change would directly increase widespread 

mortality from diseases.

5. Competitors Are populations of 

important competing 

species expected to 

change?

Other sub-species that occur in Arizona are the Arizona tiger 

salamander (A. t. nebulosum) and the barred tiger salamander (A. t. 

mavortium). Storfer and others (2004) conducted a genetic study to 

evaluate whether these two sub-species might have been introduced 

into the range of A. t. stebbinsi. The results suggested that introgression 

from introduced A. t. mavortium may be altering the gene pool of A. t. 

stebbinsi.

Not clear that climate change would increase competition of this subspecies with other sub-species.

0

Literature Cited

Allison, L.J., P.E. Brunkow, and J.P. Collins. 1994. Opportunistic breeding after summer rains by 

Arizona tiger salamanders. Great Basin Naturalist 54:376-379.

Brooks, A., and J. Rorabaugh. 1997. 50 CFR Part 17. Endangered and threatened wildlife and plants: 

Determination of endangered status for three wetland species found in southern Arizona and northern 

Sonora, Mexico. Federal Register Volume 62, Number 3: 665-689.

Carey, C., and M.A. Alexander 2003. Climate change and amphibian declines: Is there a link? Diversity 

and Distributions 9: 111-121.

Church, D. R., L.L. Bailey, H.M. Wilbur, W.L. Kendall, and J. E. Hines. 2007. Iteroparity in the variable

environment of the salamander Ambystoma tigrinum. Ecology 88: 891-903.

Collins, J.P., T.R. Jones, and H.J. Berna. 1988. Conserving genetically distinctive populations: The case 

of the Huachuca tiger salamander (Ambystoma tigrinum stebbinsi Lowe). In: Szaro, R.C., K.C. 

Severson, and D.R. Patten, eds. Management of amphibians, reptiles, and small mammals in North 

America. Fort Collins, CO: USDA Forest Service GTR-RM-166: 43-53.

Davidson, E.W., M. Parris, J.P. Collins, J.E. Longcore, A.P. Pessier, and J. Brunner. 2003. Pathogenicity 

and transmission of chyrtridiomycosis in tiger salamanders (Ambystoma tigrinum). Copeia 

2003:601-607.

Degenhardt, W. G., C. W. Painter, and A.H. Price. 1996. Amphibians and reptiles of New Mexico. 

Albuquerque: University of New Mexico Press. 431 p.

Holomuzki, J.R. 1986. Effect of microhabitat on fitness components of larva tiger salamanders, 

Ambystoma tigrinum nebulosum. Oecologia 71:142-148.

Jancovich, J. K., E. W. Davidson, J. F. Morado, B. L. Jacobs, and J. P. Collins. 1997. Isolation of a lethal 

virus from the endangered tiger salamander, Ambystoma tigrinum stebbinsi Lowe. Diseases of Aquatic 

Organisms 31: 161-167.

Lannoo, M.J., and C.A. Phillips. 2005. Tiger salamander. In: Lannoo, M., ed. Amphibian declines: The 

conservation status of United States species. Berkeley: University of California Press: 636-639. Species 

accounts also available: http://amphibiaweb.org/index.html.

Lips, K.R., J. Diffendorfer, J.R. Mendelson, III, and M.W. Sears. 2008. Riding the wave: Reconciling the 

roles of disease and climate change in amphibian declines. PLoS Biology 6:e72. 

doi:10.1371/journal.pbio.0060072.
USDA Forest Service RMRS-GTR-273. 2012. 193

231

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4: 59.

Storfer, A., S.G. Mech, M.W. Reudink, R.E. Ziemba, J. Warren, and J.P. Collins. 2004. Evidence for 

introgression in the endangered Sonora tiger salamander, Ambystoma tigrinum stebbinsi (Lowe). Copeia 

4: 783-796.

U.S. Fish and Wildlife Service [USFWS]. 2002. Sonora tiger salamander (Ambystoma tigrinum stebbinsi) 

recovery plan. Phoenix, AZ: U.S. Fish and Wildlife Service. iv + 67 p.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.

Worthylake, K.M., and P. Hovingh. 1989. Mass mortality of salamanders (Ambystoma tigrinum) by 

bacteria (Acinetobacter) in an oligotrophic seepage mountain lake. Great Basin Naturalist 49:364-372.

Habitat: American bullfrog (Rana catesbeiana)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type used 

for breeding 

activities by this 

species expected to 

change? 

This species is widespread across North America, although introduced in 

the western part of the continent (Casper and Hendricks 2005). Bullfrogs 

breed in permanent bodies of water, in shallow areas with vegetation. 

Adult bullfrogs are mostly aquatic and prefer warm, still-water habitats 

but also occupy shorelines of lakes and streams. In New Mexico, 

generally occurs below 2100 m (Degenhardt and others 1996).

This species occurs, or potential habitat exists for this species, on all 12 

of the EMAs on CNF (Jones, personal communication). Projections of

suitable climate for vegetation communities on all EMAs combined 

(Chapter 1) predict declines in suitable climate for all plant community 

types, with the exception of increases of suitable climate for semi-desert 

grassland, and small increases in Sonoran desert scrub (present in small 

amounts on the CNF).

Permanent water sources are expected to decline with projected 

conditions.

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type used 

for non-breeding 

activities by this 

species expected to 

change?

Same as above (Habitat, Question 1). 2

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected to 

change? 

Breeds in permanent water including ponds, lakes, rivers, and 

irrigation ponds. Some variation in metamorphosis duration and also 

some use of temporary ponds (Bury and Whelan 1984 as cited in 

Casper and Hendricks 2005).

Permanent water sources are expected to decline with projected 

conditions.

1
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Habitat: American bullfrog (Rana catesbeiana)

Trait/Quality Question Background info. & explanation of score Points

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for survival 

during non-breeding 

periods expected to 

change?

Winter hibernation usually takes place under water (Treanor and 

Nichola 1972 as cited in Casper and Hendricks 2005). Record of a 

bullfrog found in winter under leaf litter in a soil pocket in Michigan 

(Bohnsack 1952 as cited in Casper and Hendricks 2005). A 

radiotelemetry study in Ohio in winter of 6 individuals found 5 overwintering in relatively shallow areas in the corners of ponds and one 

frog 1-2 m from a pond (Stinner and others 1994). Of the 208 times 

frogs were located, they were submerged in each case (Stinner and 

others 1994).

Permanent water sources are expected to decline with projected 

conditions.

1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive success 

expected to change? 

Embryo mortality occurs when water temperatures exceed 32° C 

(Howard 1978b as cited in Casper and Hendricks 2005), but we 

assumed that water in most ponds rarely, if ever, gets this hot. 

Tadpoles prefer warm waters (24-30 °C; Brattstrom 1962b as cited in 

Casper and Hendricks 2005) but move into deep water until just before 

metamorphosis; avoid predators by seeking cover.

Water temperature might increase due to increased air temperatures, 

which could favor tadpole development.

-1

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to change? 

Some sources cited need for deep water for hibernation (Degenhardt 

and others 1996), but have also been found in shallow water. Some 

reductions in water depth may be expected, but unknown connection 

between water depth (and changes to water depth) and winter survival. 

0

7. Ability to 

colonize new 

areas

What is this species’ 

capacity and 

tendency to 

disperse?

Movement over land occurs on warm, rainy nights; this includes adults 

as well as dispersing of newly metamorphosed individuals (see 

references in Casper and Hendricks 2005). Can move up to 159 m in 

one night and has been found at isolated temporary ponds (Degenhardt 

and others 1996). In New York, a mean movement of 402 m and 

maximum movement of 1600 m was observed (Ingram and Raney 

1943 as cited in Casper and Hendricks 2005).

While low rainfall may reduce dispersal to new areas, we assumed it 

will be sufficient to allow dispersal, at least in some years. Although 

our sources did not suggest that there is sex-biased dispersal in this 

species, we considered this species “mobile,” though not “very 

mobile” relative to organisms that fly (e.g., birds and bats) and larger 

mammals, hence the score of “0.”

0

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Seasonal movements are considered limited and transitional habitats 

not required. 

0

Physiology: American bullfrog (Rana catesbeiana)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions expected 

to change?

Embryo mortality occurs when water temperatures exceed 32 °C 

(Howard 1978b as cited in Casper and Hendricks 2005), but we 

assumed that water in most ponds rarely, if ever, gets this hot. We 

assumed that water temperature will not exceed thresholds. Standing 

water expected to become less available, but this is covered in Habitat 

section.

0
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Physiology: American bullfrog (Rana catesbeiana)

Trait/Quality Question Background info. & explanation of score Points

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No information in Casper and Hendricks (2005) to indicate 

temperature-dependent sex determination. Vitt and Caldwell (2009) 

indicated that frogs do not experience temperature-dependent sex 

determination. 

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive failure 

expected to change?

Individuals occupying edges of streams may be exposed to increased 

flooding in spring (proportionally greater streamflow in winter and 

early spring as snow melts earlier), which could increase mortality.

No information in Casper and Hendricks (2005) to indicate that direct 

mortality from flooding has been a problem to date.

Since this species is aquatic, not likely to be seriously affected by 

temperatures associated with heat waves.

1

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to change?

Association with water suggests that activity period will not be limited 

as long as water is present. Movements occur on warm nights when 

rainy; possible that reduced precipitation will affect summer 

monsoonal rains to the point of limiting movements postmetamorphosis.

1

5. Metabolic 

inhibition

Does this species 

possess an ability to 

reduce metabolic 

energy or water 

requirements?

Cycles of dormancy are common in amphibians and reptiles, and 

hibernation is most likely primarily a response to cold temperatures 

and less so to a change in resource availability (Vitt and Caldwell 

2009). While hibernating, activity mostly ceases, body temperature 

depends on temperature of the hibernation site, and physiological 

processes are reduced.

Bullfrogs are not tolerant of freezing conditions (Casper and Hendricks 

2005). A study in Missouri reported that adults become torpid before 

frost occurs and juveniles remain active until freezing temperatures 

occur (Willis and others 1956). In contrast, Stinner and others (1994) 

suggested that bullfrogs in Ohio in winter remain active in winter and 

prefer warm, relatively shallow water.

See also Habitat, Questions 4 and 6.

Not clear whether this species would hibernate in areas where freezing 

or near-freezing temperatures do not occur regularly (e.g., low 

elevations in Arizona). Overall, scored as “0” (neutral) to account for 

this species occurring in waters where it does go torpid in winter.

0

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the capacity 

to store energy or 

water in the long 

term?

Ectotherm. -1

7. Variable life 

history

Does this species 

have alternative life 

history strategies to 

cope with variable 

resources or climate 

conditions?

The time to metamorphosis from tadpole to juvenile is negatively 

correlated with the average length of the frost-free period (references 

in Casper and Hendricks 2005). Low water temperatures during 

development have been associated with increased time to 

metamorphosis (references in Collins 1979). Based on this, considered 

possible that bullfrogs at higher elevations currently take longer to 

metamorphose than bullfrogs at lower elevations. With increased 

temperatures tadpoles where water temperature is a limiting factor 

would be expected to metamorphose in a shorter period of time in the 

future.

Yearling males do not maintain territories when male-male 

competition is intense and instead attempt to intercept females 

-1
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Physiology: American bullfrog (Rana catesbeiana)

Trait/Quality Question Background info. & explanation of score Points

attracted to larger males (Howard 1984). No known relationship 

between these strategies and climate.

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where reproduction 

is limited?

Longevity estimated as 8-10 years (Casper and Hendricks 2005).

Multi-year droughts expected, which have the potential to reduce 

ponds and other water sources on which this species depends dry up. 

Blair (1961) reported that bullfrogs declined in the late 1950s and then 

were extirpated when there was a severe drought and the tank under 

study dried up. Survival rates of tadpoles in ponds in Kentucky were 

11.8-17.6% (Cecil and Just 1979).

1

Phenology: American bullfrog (Rana catesbeiana)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Amphibians, in general, respond to temperature and moisture cues in 

the timing of breeding (Carey and Alexander 2003). Ambient 

temperature strongly influences reproduction in frogs (Gibbs and 

Breisch 2001). Breeding occurs earlier in southern latitudes (Casper 

and Hendricks 2005) as for many vertebrates. In Texas, breeds from 

March through October (Blair 1961). In Kansas, calling begins when 

air temperatures are above 21 °C (Fitch 1956c as cited in Casper and 

Hendricks 2005). Calling season of this species in Texas corresponded 

more to hot summer season than other anurans, and evening calling 

associated with higher temperatures (Blair 1961) and individuals called 

after rainfall events. Adults tend to remain inactive until water 

temperatures reach 15 °C (Harding 1977 as cited in Casper and 

Hendricks 2005).

1

2. Event 

timing

Are activities related 

to species’ fecundity 

or survival tied to 

discrete events that 

are expected to 

change? 

Species uses still water for breeding. Changes to timing of peak flow in 

spring could alter the timing of when still waters are achieved in the 

spring. On the other hand, breeding may occur earlier due to 

temperature rises, as breeding activity is associated with temperature 

and rainfall (see Phenology, Question 1).

1

3. Mismatch 

potential

What is the 

separation in time or 

space between cues 

that initiate 

activities and 

discrete events that 

provide critical 

resources?

Cues and critical resources (e.g., food) expected to be closely related in 

time and space.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies or 

have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Double clutching has been observed in Michigan (Emlen 1977 as cited 

in Casper and Hendricks 2005) and expected to occur elsewhere, 

particularly in southern latitudes. Older females may produce two 

clutches per year (Howard 1978b as cited in Casper and Hendricks 

2005). Reproductive period is prolonged as there is large variation in 

date of sexually receptivity for individual females and males remain 

reproductively active (Degenhardt and others 1996).

-1
USDA Forest Service RMRS-GTR-273. 2012. 197

235

Biotic interactions: American bullfrog (Rana catesbeiana)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

An opportunistic predator; preys on almost any animal it can capture 

(smaller than it) including conspecifics (Casper and Hendricks 2005). 

Consumes invertebrates, snakes, rodents, frogs, and salamanders. 

Often eats beetles and snails in New Mexico (Degenhardt and others 

1996).

0

2. Predators Are important 

predator 

populations 

expected to change?

Various predators. Tadpoles relatively unpalatable to fish (references 

in Casper and Hendricks 2005). Tadpoles eaten by salamanders, other 

frogs, turtles, snakes, birds, mammals, as well as adult bullfrogs 

(Casper and Hendricks 2005). 

0

3. Symbionts Are populations of 

symbiotic species 

expected to change?

No known symbionts. 0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to change? 

Chytridiomycosis is a disease associated with amphibian declines. 

Laboratory studies suggest that bullfrogs are an efficient carrier of the 

pathogen (although they appear to be resistant to clinical effects of the 

disease (Daszak and others 2004). Conflicting evidence about whether 

changes in climate are affecting susceptibility of amphibians to 

chytrid fungal infections (Lips and others 2008).

0

5. Competitors Are populations of 

important 

competing species 

expected to change?

Bullfrog tadpoles have been shown to out-compete native tadpoles 

such as yellow-legged frog (Rana boylii) and Pacific tree frogs (Hyla 

regilla) in California (Kupferberg 1997). No known major 

competitors.

0

Literature Cited

Blair, W.F. 1961. Calling and spawning seasons in a mixed population of anurans. Ecology 42:99-110.

Carey, C., and M.A. Alexander 2003. Climate change and amphibian declines: Is there a link? Diversity 

and Distributions 9:111-121.

Casper, G.S. and R. Hendricks. 2005. American Bullfrog. In: Lannoo, M., ed. Amphibian declines: The 

conservation status of United States species. Berkeley: University of California Press: 540-546. Species 

accounts also available: http://amphibiaweb.org/index.html.

Cecil, S.G., and J.J. Just. 1979. Survival rate, population density and development of a naturally 

occurring anuran larvae (Rana catesbeiana). Copeia 3:447-453.

Collins, J.P. 1979. Intrapopulation variation in the body size at metamorphosis and timing of 

metamorphosis in the bullfrog, Rana catesbeiana. Ecology 60:738-749.

Daszak, P., A. Strieby, A.A. Cunningham, J.E. Longcore, C.C. Brown, and D. Porter. 2004. Experimental 

evidence that the bullfrog (Rana catesbeiana) is a potential carrier of chytridiomycosis, an emerging 

fungal disease of amphibians. Herpetological Journal 14:201-207.

Degenhardt, W.G., C.W. Painter, and A.H. Price. 1996. Amphibians and reptiles of New Mexico. 

Albuquerque: University of New Mexico Press. 431 p.

Gibbs, J.P., and A.R. Breisch. 2001. Climate warming and calling phenology of frogs near Ithaca, New 

York, 1900-1999. Conservation Biology 15:1175-1178.

Howard, R. 1984. Alternative mating behaviors of young male bullfrogs. American Zoologist 

24:397-406.

Jones, Larry. 2010. [Personal communication]. February 17, 2010. Tucson, AZ: U.S. Department of 

Agriculture, Forest Service, Coronado National Forest, Assistant Program Manager for Wildlife, Fish, 

and Rare Plants.

Kupferberg, S. 1997. Bullfrog (Rana catesbeiana) invasion of a California river: The role of larval 

competition. Ecology 78:1736-1751.
198 USDA Forest Service RMRS-GTR-273. 2012.

236

Lips, K.R., J. Diffendorfer, J.R. Mendelson. III, and M.W. Sears. 2008. Riding the wave: Reconciling the 

roles of disease and climate change in amphibian declines. PLoS Biology 6:e72. 

doi:10.1371/journal.pbio.0060072.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Stinner, J., N. Zarlinga, and S. Orcutt. 1994. Overwintering behavior of adult bullfrogs, Rana 

catesbeiana, in northeastern Ohio. Ohio Journal of Science 94:8-13.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.

Willis, Y.L., D.L. Moyle, and T.S. Baskett. 1956. Emergence, breeding, hibernation, movements, and 

transformation of the bullfrog, Rana catesbeiana, in Missouri. Copeia 1:30-41.

Habitat: Chiricahua leopard frog (Rana chiricahuensis)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for breeding 

activities by this 

species expected to 

change? 

Occurs in Arizona, New Mexico, and Mexico (Platz and Mecham 

1979). Found chiefly in oak, mixed oak, and pine woodlands and pine 

forests; ranges into chaparral, grassland, and even desert (Stebbins 

1985). Distribution of species is fragmented by aridity (Mecham 1968c 

as cited in Sredl and Jennings 2005). Elevational range is 1000-2710 m 

(Platz and Mecham 1979).

Breeds in still waters in a range of natural and human-created systems 

(multiple references in Sredl and Jennings [2005]; see Habitat, 

Question 3). At thermal springs in New Mexico this species had 

prolonged annual activity including year-round activity at one site and 

including winter breeding (Scott and Jennings 1985).

This species occurs, or potential habitat exists for this species, on 

seven of the EMAs on CNF: Peloncillo, Chiricahua, Dragoon, 

Tumacacori, Santa Rita, Huachuca, and Galiuro (USFS 2009). 

Projections of suitable climate for vegetation communities on all 

EMAs combined (Chapter 1) predicted declines in suitable climate for 

all plant community types, with the exception of increases of suitable 

climate for semi-desert grassland and small increases in Sonoran desert 

scrub (present in small amounts on the CNF).

Riparian and forested habitats predicted to decline due to decreased 

stream flows on average, increased aridity, and increased fire risk. 

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonbreeding activities 

by this species 

expected to 

change?

Individuals likely over-winter near breeding sites, but information 

about locations of hibernation areas not well known (Sredl and 

Jennings 2005). Generally considered a habitat generalist (Sredl and 

Jennings 2005). Juvenile habitat not well studied, but in a closelyrelated species, Rana yavapaiensis, juveniles were more frequently 

found in small ponds and marshy areas, whereas adults were more 

often associated with large pools (Sredl 1994 as cited in Sredl and 

Jennings 2005). Adult habitat ranges from perennial to near-perennial 

(Sredl and Jennings 2005). Not known how this species survives loss 

of surface water, but other species of leopard frog in the Southwest 

have been observed burrowing into cracks in the mud (Howland and 

others 1997 as cited in Sredl and Jennings 2005).

2
USDA Forest Service RMRS-GTR-273. 2012. 199

237

Habitat: Chiricahua leopard frog (Rana chiricahuensis)

Trait/Quality Question Background info. & explanation of score Points

Predicted changes in habitat considered same as for breeding habitat; 

see Habitat, Question 1.

3. Habitat 

components: 

breeding

Are specific habitat 

components 

required for 

breeding expected 

to change? 

Requires water for breeding (Sredl and Jennings 2005). Breeding areas 

include rivers, permanent streams and pools, intermittent streams, 

wetlands, and springs. Also observed in earthen tanks and drinkers (for 

livestock), wells, abandoned swimming pools, backyard ponds, etc. 

(Sredl and Jennings 2005). Shallow water with emergent and perimeter 

vegetation provide adult and tadpole basking areas; deeper water, root 

masses, and undercut banks offer refuge from predators and may offer 

hibernacula (unpublished data cited in Sredl and Jennings 2005).

Important breeding areas include those with few predators (fish, 

bullfrogs, and crayfish).

Some studies have found frogs and eggs masses to be most abundant in 

areas with warmer water (Jennings 1988, 1990 as cited in Sredl and 

Jennings 2005). Thermal springs in New Mexico provide winter 

breeding opportunities (Sredl and Jennings 2005). Unclear how much 

water temperature in southern Arizona streams would increase.

Potential for water during breeding season to be reduced we considered 

a larger impact than potential increased suitability for breeding by 

increase in water temperature.

1

4. Habitat 

components: 

non-breeding

Are specific habitat 

components 

required for 

survival during 

non-breeding 

periods expected to 

change?

See Habitat, Question 3. Reduced precipitation could reduce ability to 

survive during non-breeding season.

1

5. Habitat 

quality and 

reproduction

Are features of the 

habitat associated 

with better 

reproductive 

success expected to 

change? 

Little information. 0

6. Habitat 

quality and 

survival

Are features of the 

habitat associated 

with better survival 

expected to 

change? 

Year-round water supply, areas with undercut banks for escape from 

predation and potential hibernacula (Sredl and Jennings 2005). 

1

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Male home ranges have been estimated at 161 m2

 and 357 m2 in the 

dry and wet seasons, respectively (unpublished data in Sredl and 

Jennings 2005). One male moved 3.5 km in one direction over a 2-

month period. Overall, considered to have a low ability to disperse 

given small home range and given absence of data suggesting this 

species consistently moves long distances. 

1

8. Migratory 

or transitional 

habitats

Does this species 

require additional 

habitats during 

migration that are 

separated from 

breeding and nonbreeding habitats?

Unlike some other amphibians, breeding migrations have not been 

noted in this species (Sredl and Jennings 2005). Maintaining corridors 

for dispersal of juveniles and adults may be critical to preserving 

populations (Jennings and Scott 1991 as cited in Sredl and Jennings 

2005), but we considered this beyond the scope of this question.

0
200 USDA Forest Service RMRS-GTR-273. 2012.

238

Physiology: Chiricahua leopard frog (Rana chiricahuensis)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are physiological 

thresholds related 

to temperature or 

moisture expected 

to change?

Decrease in precipitation and increased evaporation (due to increased

temperatures) may reduce the amount of moisture available for this 

species to survive during over-wintering periods (increases probability 

of desiccation).

We assumed that water temperature will not exceed thresholds.

Standing water expected to become less available, but this is covered 

in Habitat section above.

1

2. Sex ratio Is sex ratio 

determined by 

temperature? 

Vitt and Caldwell (2009) indicated that frogs do not experience 

temperature-dependent sex determination. 

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive 

failure expected to 

change?

Individuals occupying edges of streams may be exposed to increased 

flooding (proportionally greater streamflow in winter and early spring 

as snow melts earlier) which could increase mortality. Since this 

species is aquatic, not likely to be seriously affected by air 

temperatures associated with short-term heat waves.

1

4. Limitations 

to active 

period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to 

change?

Adult habitat ranges from perennial to near-perennial (Sredl and 

Jennings 2005); not known how this species survives loss of surface 

water (other species of leopard frog in the Southwest have been 

observed burrowing into cracks in the mud [Howland and others 1997 

as cited in Sredl and Jennings 2005]). Thus, reduced precipitation 

could reduce activity periods through increased aridity of the 

environment.

1

5. Metabolic 

inhibition

Does this species 

possess an ability 

to reduce 

metabolic energy 

or water 

requirements?

Cycles of dormancy are common in amphibians and reptiles, and 

hibernation is most likely primarily a response to cold temperatures 

more than to a change in resource availability (Vitt and Caldwell 

2009). While hibernating, activity mostly ceases, body temperature 

depends on temperature of the hibernation site, and physiological 

processes are reduced.

Post-metamorphic individuals are generally not active NovemberFebruary, although few studies have been conducted on wintertime 

activity (Sredl and Jennings 2005). Individuals likely over-winter near 

breeding sites but information about locations of hibernation areas not 

well known (Sredl and Jennings 2005). Considered possible that 

hibernacula would be exposed to increased temperatures (thus, score of 

“1”).

1

6. Survival 

during 

resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the 

capacity to store 

energy or water in 

the long term?

None. Ectotherm. -1

7. Variable life 

history

Does this species 

have alternative 

life history 

strategies to cope 

with variable 

resources or 

climate conditions?

Frogs have tadpole stage, but this is not considered a benefit since 

water is also required for this stage.

0

8. 

Reproduction 

Can this species 

outlive periods 

Multi-year droughts are projected. Preliminary estimates suggest that 

individuals can live as long as 6 years (Durkin 1995 as cited in Sredl 

1
USDA Forest Service RMRS-GTR-273. 2012. 201

239

Physiology: Chiricahua leopard frog (Rana chiricahuensis)

Trait/Quality Question Background info. & explanation of score Points

in variable 

environments

where reproduction 

is limited?

and Jennings 2005), although most individuals expected to live shorter 

periods than this. In 2002/2003 surveys, Jones and Sredl (2005) 

observed apparent local extirpations that coincided with a drought that 

began in 1996/1997 at a large numbers of sites. 

Phenology: Chiricahua leopard frog (Rana chiricahuensis)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Amphibians in general respond to temperature and moisture cues in the 

timing of breeding (Carey and Alexander 2003). Ambient temperature 

strongly influences reproduction in frogs (Gibbs and Breisch 2001). 

Proximate cues that stimulate mating are not well studied in this 

species (Sredl and Jennings 2005). One unpublished report on a closely 

related species, Rana subaquavocalis (Platz 1997 as cited in Sredl and 

Jennings 2005) indicated that oviposition appeared to be correlated 

with changes in water temperature and not precipitation.

1

2. Event 

timing

Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

Species requires still water for breeding. Changes to timing in peak 

flow in spring flow (earlier peak flow) and timing of rise in water 

temperatures likely to change.

1

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

Species is non-migratory. Resources are closely timed. -1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Egg masses have been reported in all months except November, 

December, and January (references in Sredl and Jennings 2005). Egglaying in this species in Arizona and New Mexico appears to differ 

according to elevation of occupied habitat; during 1972-1979, 

populations below ~1800 m generally deposited eggs from spring to 

late summer (most before June), whereas those above 1800 m laid in 

June, July, and August (Frost and Platz 1983). 

-1

Biotic interactions: Chiricahua leopard frog (Rana chiricahuensis)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

No comprehensive study of diet of larval or adult forms has been 

conducted (Sredl and Jennings 2005). Larvae are herbivorous; adults 

likely eat a diverse array of insects (Degenhardt and others 1996 as 

cited in Sredl and Jennings 2005). Analyses of stomach contents 

showed invertebrates and vertebrates (fish, conspecific and 

heterospecific frogs, and birds; Stebbins 1951 as cited in Sredl and 

Jennings 2005).

0
202 USDA Forest Service RMRS-GTR-273. 2012.

240

Biotic interactions: Chiricahua leopard frog (Rana chiricahuensis)

Trait/Quality Question Background info. & explanation of score Points

2. Predators Are important 

predator 

populations 

expected to 

change?

Detailed studies have not been conducted (Sredl and Jennings 2005). 

Considered likely that tadpoles are preyed upon by aquatic insects and 

vertebrates (birds, snakes, and non-native fish). Juvenile and adult 

frogs likely preyed upon by fish (native and non-native), American 

bullfrogs, gartersnakes, birds, and a variety of mammals (Sredl and 

Jennings 2005). Likely predators—giant water bugs (belostomatids) 

and black-necked gartersnakes (Thamnophis cyrtopsis)—were 

observed during surveys by Jones and Sredl (2005). Presence of 

American bullfrogs, crayfish, and predatory fish are negatively 

correlated with presence of this species (references in Sredl and 

Jennings 2005) although in New Mexico, many populations have 

declined in the absence of bullfrogs (Jennings and Scott 1991 as cited 

in Sredl and Jennings 2005).

Overall, this species considered to be preyed upon by a suite of 

predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to 

change?

No information on this species in Sredl and Jennings (2005) regarding 

symbiotic relationships.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to 

change? 

Six species of trematode and one nematode were found in this species 

(Goldberg and others 1998b as cited in Sredl and Jennings 2005).

In late 1980s, high mortality of this species in earthen cattle tanks in 

New Mexico was observed, including extirpation of many 

populations over 3 years; “post-metamorphic death syndrome” was 

implicated although chytrid fungus may have played a role (Sredl and 

Jennings 2005). Chytrid fungus is present in Arizona and many 

species, including this one, have been affected (Sredl and Jennings 

2005). Outbreaks of the fungus have occurred during the cool season 

(Sredl and others 2000 as cited in Sredl and Jennings 2005). The 

fungus was confirmed present in populations in New Mexico that 

declined (Sredl and Jennings 2005). Conflicting evidence about 

whether changes in climate are affecting susceptibility of amphibians 

to chytrid fungal infections (Lips and others 2008).

0

5. Competitors Are populations of 

important 

competing species 

expected to 

change?

Negative association with American bullfrogs (Rosen and others 1995 

as cited in Sredl and Jennings 2005) considered to be predatory, not 

competitive. No clear relationships found regarding important 

competition with other species.

0

Literature Cited

Carey, C., and M.A. Alexander 2003. Climate change and amphibian declines: Is there a link? Diversity 

and Distributions 9:111-121.

Frost, J.S., and J.E. Platz. 1983. Comparative assessment of modes of reproductive isolation among four 

species of leopard frogs (Rana pipiens complex). Evolution 37:66-78.

Gibbs, J.P., and A.R. Breisch. 2001. Climate warming and calling phenology of frogs near Ithaca, New 

York, 1900-1999. Conservation Biology 15:1175-1178.

Jones, L.L.C., and M.J. Sredl. 2005. Chiricahua leopard frog status in the Galiuro Mountains, Arizona, 

with a monitoring framework for the species’ entire range. In: Gottfried, G.J., B.S. Gebow, L.G. Eskew, 

C.B. Carleton, comps. Connecting mountain islands and desert seas: Biodiversity and management of 

the Madrean Archipelago II. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of Agriculture, 

Forest Service, Rocky Mountain Research Station: 88-91.
USDA Forest Service RMRS-GTR-273. 2012. 203

241

Lips, K.R., J. Diffendorfer, J.R. Mendelson, III, and M.W. Sears. 2008. Riding the wave: Reconciling the 

roles of disease and climate change in amphibian declines. PLoS Biology 6:e72. 

doi:10.1371/journal.pbio.0060072.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Platz, J.E., and J.S. Mecham. 1979. Rana chiricahuensis, a new species of leopard frog (Rana pipiens

complex) from Arizona. Copeia 1979:383-390.

Scott, N.J., Jr., and R.D. Jennings. 1985. The tadpoles of five species of New Mexican leopard frogs. 

Museum of Southwestern Biology, Occasional Papers, Number 3. Albuquerque: University of New 

Mexico.

Sredl, M.J., and R.D. Jennings. 2005. Chiricahua Leopard Frogs. In: Lannoo, M., ed. Amphibian 

declines: The conservation status of United States species. Berkeley: University of California Press: 

546-549. Species accounts also available: http://amphibiaweb.org/index.html.

Stebbins, R.C. 1985. A Field Guide to Western Amphibians and Reptiles (Second edition). New York: 

Houghton Mifflin.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture. Available: http://www.fs.fed.us/r3/coronado/planrevision/documents/final/cnf-ecological-sustainability-report-final-022009.pdf.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.

Habitat: Tarahumara frog (Rana tarahumarae)

Trait/Quality Question Background info. & explanation of score Points

1. Area and 

distribution: 

breeding

Is the area or 

location of the 

associated 

vegetation type 

used for 

breeding 

activities by this 

species expected 

to change? 

From Rorabaugh and Hale (2005): This species is known from 63 

locations in montane canyons, from southeastern Arizona, south to 

Mexico (parts of Sinaloa and Chihuahua). Historically, this species was 

known from 6 locations in the United States (3 in Santa Rita Mountains 

and 3 in the Atascosa-Pajarito-Tumacacori Mountains complex), but by 

1983, it had been extirpated from Arizona. Declines in some sites in 

Mexico occurred around the same time (Rorabaugh and others 2005). 

Individuals were re-established in the Santa Rita Mountains in 2004 (Big 

Casa Blanca Canyon). Zweifel (1968) provided (historical) locality 

information in Arizona, all of which was within 20 km of the Mexican 

border; elevational range 457-1828 m (1500-6000 ft) Rorabaugh and 

others (2005) and Hale and May (1983) also reviewed historical 

locations.

Breeding habitat is oak and pine-oak woodlands; juveniles appear to use 

same habitat as adults (references in Rorabaugh and Hale 2005). Zweifel 

(1955) indicated that cottonwoods and willows frequently shade pools 

used by this species. Large streams are generally avoided, probably due 

to the greater variation in flow rates and greater propensity for remaining 

flooded longer in spring from winter snowmelt (Hale and May 1983).

This species occurs, or potential habitat exists for this species, only in the 

Santa Rita EMA on CNF (USFS 2009). Projections of suitable climate 

for vegetation communities on this EMAs (Chapter 1) predicted declines 

in suitable climate for Madrean forest and woodland and Madrean 

coniferous forest and an increase in semi-desert grassland.

Riparian and woodland habitats predicted to decline due to decreased 

stream flows on average, increased aridity, and increased fire risk. 

2

2. Area and 

distribution: 

non-breeding

Is the area or 

location of the 

associated 

vegetation type 

used for nonNon-breeding habitat considered to be same as breeding habitat. See 

Habitat, Question 1.

Hibernacula covered in Habitat, Question 4.

2
204 USDA Forest Service RMRS-GTR-273. 2012.

242

Habitat: Tarahumara frog (Rana tarahumarae)

Trait/Quality Question Background info. & explanation of score Points

breeding 

activities by this 

species expected 

to change?

3. Habitat 

components: 

breeding

Are specific 

habitat 

components 

required for 

breeding 

expected to 

change? 

This species has aquatic reproduction and requires a permanent water 

source for metamorphosis (Rorabaugh and Hale 2005). Generally breeds 

April-May, when permanent water is often limited to springs and pools 

>1 m in depth in bedrock or among boulders. Best breeding habitat are 

such pools with low mean flows (<0.2 cubic ft/sec and relatively steep 

gradients; “plunge pools”). Tadpole metamorphosis has been reported to

take 2 years (Hale and May 1983); in semi-wild conditions, most took 

>10 months.

Water sources are expected to decline.

1

4. Habitat 

components: 

non-breeding

Are specific 

habitat 

components 

required for 

survival during 

non-breeding 

periods expected 

to change?

This species requires a permanent water source for metamorphosis 

(Rorabaugh and Hale 2005). See also Habitat, Question 3.

An important feature is the presence of hibernacula that allow individuals to 

remain moist and offers protection from predators and freezing temperatures; 

such hibernacula include moist areas around rocks or boulders along streams 

and at “plunge pools” (Hale and May 1983).

Water sources are expected to decline.

1

5. Habitat 

quality and 

reproduction

Are features of 

the habitat 

associated with 

better 

reproductive 

success expected 

to change? 

No information found. 0

6. Habitat 

quality and 

survival

Are features of 

the habitat 

associated with 

better survival 

expected to 

change? 

Both boulder plunge pools (formed by boulders creating a barrier across 

a streambed) and bedrock plunge pools (formed when bedrock is exposed 

along the streambed) are highly favorable habitat for this species (Hale 

and May 1983).

Climate change would not alter the abundance of boulders or bedrock; 

water availability covered in Habitat, Questions 3 and 4.

0

7. Ability to 

colonize new 

areas

What is this 

species’ capacity 

and tendency to 

disperse?

Capacity to disperse appears to be low. In Big Casa Blanca Canyon in 

Arizona, juveniles and males reported to move <1885 m, and females 

<651 m and were along stream courses; authors indicated limited 

overland movements might have occurred (Hale and May 1983). Authors 

also indicated that some individuals prefer to remain in specific pools or 

stream reaches.

Tadpoles likely are transported downstream. Hale and May (1983) 

documented upstream movements by most frogs during the summer 

rainy season; closer to autumn, frogs moved mostly downstream, 

although some may move upstream to reach hibernacula.

1

8. Migratory or 

transitional 

habitats

Does this species 

require 

additional 

habitats during 

migration that 

are separated 

from breeding 

and nonbreeding 

habitats?

Rorabaugh and Hale (2005) indicated it is unknown if this species 

undertakes breeding migrations. Seasonal short-distance movements 

documented in Hale and May (2003). In Big Casa Blanca Canyon in 

Arizona, juveniles and males reported to move <1885 m, and females 

<651 m along stream courses (Hale and May 1983). See also Habitat, 

Question 7 for additional information.

0
USDA Forest Service RMRS-GTR-273. 2012. 243 205

Physiology: Tarahumara frog (Rana tarahumarae)

Trait/Quality Question Background info. & explanation of score Points

1. 

Physiological 

thresholds

Are limiting 

physiological 

conditions 

expected to 

change?

Decrease in precipitation and increased evaporation (due to increased 

temperatures) may reduce the amount of moisture available for this 

species to survive during over-wintering periods (increases 

probability of desiccation).

We assumed that water temperature will not exceed thresholds. 

Standing water expected to become less available, but this is covered 

in Habitat section.

1

2. Sex ratio Is sex ratio 

determined by 

temperature? 

No information in Rorabaugh and Hale (2005) to indicate this occurs 

in Rana tarahumarae. Vitt and Caldwell (2009) indicated that frogs 

do not experience temperature-dependent sex determination. 

0

3. Exposure to 

extreme 

weather 

conditions

Are extreme 

weather or 

disturbance events 

that result in direct 

mortality or 

reproductive 

failure expected to 

change?

Individuals occupying stream edges may be exposed to increased 

flooding (proportionally greater streamflow in winter and early spring 

as snow melts earlier) which could increase mortality. Since this 

species is aquatic, not likely to be seriously affected by air 

temperatures associated with heat waves.

1

4. Limitations 

to active period

Are projected 

temperature or 

precipitation 

regimes that 

influence activity 

period of species 

expected to 

change?

Appears to feed nocturnally and diurnally depending on when prey 

species are active (Rorabaugh and Hale 2005). Rorabaugh and Hale 

(2005) indicated that during the dry season before the summer rains, 

most individuals probably reside in plunge pools to avoid desiccation. 

But the authors indicated that Hale and May (1983) suggested that 

this species may aestivate during this period.

Reduced precipitation could reduce the length of seasonal activity 

periods by reducing water depth in plunge pools and leading to earlier 

retreats to hibernacula. 

1

5. Metabolic 

inhibition

Does this species 

possess an ability 

to reduce 

metabolic energy 

or water 

requirements?

Cycles of dormancy are common in amphibians and reptiles, and 

hibernation is most likely primarily a response to cold temperatures 

more than to a change in resource availability (Vitt and Caldwell 

2009). While hibernating, activity mostly ceases, body temperature 

depends on temperature of the hibernation site, and physiological 

processes are reduced.

In Big Casa Blanca Canyon, this species was not active in February 

when water temperatures were ~8 °C; when water temperatures 

averaged ~15 °C many frogs were active (Hale and May 1983). 

Authors indicated that they appear to hibernate very near the water 

line, “perhaps in air pockets behind partially submerged boulders near 

pools.” Boulder plunge pool habitat offers places for frogs to retreat 

during periods of cold weather (Hale and May 1983).

During the dry season, although some frogs may aestivate, most 

congregate in pools that have not gone dry.

Given that many individuals appear to over-winter in areas that do not 

appear to be largely protected from temperature fluctuations as would 

underwater burrowing into mud, considered possible that hibernacula 

would be exposed to increased temperatures (thus, score of “1”).

1

6. Survival 

during resource 

limitation

Does this species 

have lower energy 

requirements or 

possess the 

capacity to store 

energy or water in 

the long term?

Ectotherm. -1
206 USDA Forest Service RMRS-GTR-273. 2012.

244

Physiology: Tarahumara frog (Rana tarahumarae)

Trait/Quality Question Background info. & explanation of score Points

7. Variable life 

history

Does this species 

have alternative 

life history 

strategies to cope 

with variable 

resources or 

climate 

conditions?

Frogs have a tadpole stage, but this is not considered a benefit since 

water is required for this stage.

0

8. 

Reproduction 

in variable 

environments

Can this species 

outlive periods 

where 

reproduction is 

limited?

Hale and May (1983) estimated that the oldest frogs in Big Casa 

Blanca Canyon (Arizona) were 6 years post-metamorphosis at the 

least. Larvae take 2 years to complete metamorphosis (Hale and May 

1983).

Periods of extreme reductions in rainfall may last 5 years, which can 

reduce ponds and other water sources on which this species depends. 

If these conditions eliminate breeding, most of the population would 

not survive longer than the periods of limited reproduction.

1

Phenology: Tarahumara frog (Rana tarahumarae)

Trait/Quality Question Background info. & explanation of score Points

1. Cues Does this species 

use temperature or 

moisture cues to 

initiate activities 

related to fecundity 

or survival? 

Amphibians, in general, respond to temperature and moisture cues in 

the timing of breeding (Carey and Alexander 2003). Ambient 

temperature strongly influences reproduction in frogs (Gibbs and 

Breisch 2001). Hale and May (1983) indicated that spring emergence 

is directly related to water temperatures (which vary by elevation, 

exposure, flow rates, and water source).

1

2. Event 

timing

Are activities 

related to species’ 

fecundity or 

survival tied to 

discrete events that 

are expected to 

change? 

Changes to timing in spring flow (earlier peak flow) and timing of 

rise in water temperatures likely to change.

1

3. Mismatch 

potential

What is the 

separation in time 

or space between 

cues that initiate 

activities and 

discrete events that 

provide critical 

resources?

Species is non-migratory. Cues and critical resources (e.g., food) 

expected to be closely related in time and space.

-1

4. Resilience 

to timing 

mismatches 

during 

breeding

Does this species 

employ strategies 

or have traits that 

increase the 

likelihood of 

reproduction cooccurring with 

important events?

Hale and May (1983) reported that amplectic frogs and egg masses 

were generally found from April to mid-May. Thus, the species does 

not appear to have a prolonged breeding period.

1
USDA Forest Service RMRS-GTR-273. 2012. 207

245

Biotic interactions: Tarahumara frog (Rana tarahumarae)

Trait/Quality Question Background info. & explanation of score Points

1. Food 

resources

Are important food 

resources for this 

species expected to 

change?

Larvae are likely omnivorous with a tendency to consume algae, as 

are most ranid tadpoles (Rorabaugh and Hale 2005). Adults consume 

a variety of prey ranging from juvenile Sonoran mud turtles, Sonora 

chubs, snakes, beetles, moths, water bugs, scorpions, centipedes, 

grasshoppers, mantids, wasps, spiders, crickets, caddis flies, and 

katydids (references in Zweifel 1955; Rorabaugh and Hale 2005). 

Appears to feed nocturnally and diurnally, depending on time that 

prey species are known to be active (Rorabaugh and Hale 2005).

Overall, species consumes a variety of prey species.

0

2. Predators Are important 

predator 

populations 

expected to 

change?

From Rorabaugh and Hale (2005) and references therein: Frog adults, 

tadpoles, and egg masses are expected to have a variety of predators 

including gartersnakes and other snake species, birds, frogs, 

salamanders, fish, invertebrates, and water bugs (Belostoma and 

Lethocerus genera). Non-native fish (e.g., green sunfish [Lepomis 

cyanellus], but also largemouth bass [Micropterus salmoides]) and 

American bullfrog predation may have been partly responsible for the 

elimination of Tarahumara frog from Pena Blanca Canyon in Arizona. 

Large chub species (Gila sp.) may have eliminated this species from 

one site in Mexico.

Overall, preyed upon by a suite of predators.

0

3. Symbionts Are populations of 

symbiotic species 

expected to 

change?

No information on this species in Rorabaugh and Hale (2005) 

regarding symbiotic relationships.

0

4. Disease Is prevalence of 

diseases known to 

cause widespread 

mortality or 

reproductive failure 

in this species 

expected to 

change?

During a die-off in Sycamore Canyon (Arizona) in 1974, individuals

of this species were collected that were infected with 

chytridiomycosis; the chytrid fungus has also been found in frogs 

collected in Mexico (Rorabaugh and Hale 2005). The fungus is 

considered as a possible factor involved in the extirpation of this 

species in Arizona (Hale and others 2005); these authors consider that 

cold may play a role in creating stress for frogs that may make them 

more susceptible to infection.

Other factors considered to have potentially contributed to the 

extirpation of this species in Arizona are: heavy metal poisoning (acid 

rain from copper smelters may have mobilized naturally-occurring 

metals in streamside deposits into the water), predation, competition, 

flooding or severe drought, and winter cold (Rorabaugh and Hale 

2005). Conflicting evidence about whether changes in climate are 

affecting susceptibility of amphibians to chytrid fungal infections 

(Lips and others 2008).

Individuals mildly infected with nematodes and trematodes reported 

in Sonora, Mexico (Hale and Jarchow 1988).

0

5. Competitors Are populations of 

important 

competing species 

expected to 

change?

In southern Arizona, this species was found in association with 

Chiricahua leopard frogs, and in most locations where this species 

occurs, canyon tree frogs (Hyla arenicolor) have been observed 

(Rorabaugh and Hale 2005). No information in Rorabaugh and Hale 

(2005) indicating strong competition between R. tarahumarae and 

these species.

0

Literature Cited

Carey, C., and M.A. Alexander 2003. Climate change and amphibian declines: Is there a link? Diversity 

and Distributions 9:111-121.
208 USDA Forest Service RMRS-GTR-273. 2012.

246

Gibbs, J.P., and A.R. Breisch. 2001. Climate warming and calling phenology of frogs near Ithaca, New 

York, 1900-1999. Conservation Biology 15:1175-1178.

Hale, S.F., P.C. Rosen, J.L. Jarchow, and G.A. Bradley. 2005. Effects of the chytrid fungus on the 

Tarahumara frog (Rana tarahumarae) in Arizona and Sonora, Mexico. In: Gottfried, G.J., B.S. Gebow, 

L.G. Eskew, C.B. Edminster, comps. Connecting mountain islands and desert seas: Biodiversity and 

management of the Madrean Archipelago II. 2004 May 11-15; Tucson, AZ. Proc. RMRS-P-36. Fort 

Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 407-

411.

Hale, S.F., and J.L. Jarchow. 1988. The status of the Tarahumara frog (Rana tarahumarae) in the United 

States and Mexico: Part II. Prepared for: Arizona Game and Fish Department, and Office of 

Endangered Species, U.S. Fish and Wildlife Service, Albuquerque, NM.

Hale, S.F., and C.J. May. 1983. Status report for the Rana tarahumarae Boulenger. Prepared for: Office 

of Endangered Species, U.S. Fish and Wildlife Service, Albuquerque, NM. Prepared by Stephen F. 

Hale, Arizona Natural Heritage Program, Tucson, AZ, and Clayton J. May, Pima Community College, 

Tucson, AZ.

Lips, K.R., J. Diffendorfer, J.R. Mendelson, III, and M.W. Sears. 2008. Riding the wave: Reconciling the 

roles of disease and climate change in amphibian declines. PLoS Biology 6:e72. 

doi:10.1371/journal.pbio.0060072.

Manolakou, P., G. Lavranos, and R. Angelopoulou. 2006. Molecular patterns of sex determination in the 

animal kingdom: A comparative study of the biology of reproduction. Reproductive Biology and 

Endocrinology 4:59.

Rorabaugh, J.C., and S.F. Hale. 2005. Tarahumara Frog. In: Lannoo, M., ed. Amphibian declines: The 

conservation status of United States species. Berkeley: University of California Press: 593-595. Species 

accounts also available: http://amphibiaweb.org/index.html.

Rorabaugh, J.C., S.F. Hale, M.J. Sredl, and C. Ivanyi. 2005. Return of the Tarahumara frog to Arizona. 

In: Gottfried, G.J., B.S. Gebow, L.G. Eskew, C.B. Edminster, comps. Connecting mountain islands and 

desert seas: biodiversity and management of the Madrean Archipelago II. 2004 May 11-15; Tucson, 

AZ. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky 

Mountain Research Station: 345-348.

U.S. Forest Service [USFS]. 2009. Draft Coronado National Forest ecological sustainability report. 

Tucson, AZ: U.S. Department of Agriculture, Forest Service. Available: 

http://www.fs.fed.us/r3/coronado/plan-revision/documents/final/cnf-ecological-sustainability-reportfinal-022009.pdf.

Vitt, L.J., and J.P. Caldwell. 2009. Herpetology. Oxford, United Kingdom: Elsevier. 697 p.

Zweifel, R.G. 1955. Ecology, distribution, and systematic of frogs of the Rana boylei group. University 

of California Publications in Zoology: 54:207-292. Berkeley: University of California Press.

Zweifel, R.G. 1968. Rana tarahumarae Boulenger. No. 66. Catalogue of American Amphibians and 

Reptiles. Society for the Study of Amphibians and Reptiles.

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