United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

General Technical 

Report RMRS-GTR-284

August 2012

Vulnerability of Species to Climate Change in the 

Southwest: Threatened, Endangered, and At-Risk 

Species at the Barry M. Goldwater Range, Arizona

Karen E. Bagne and Deborah M. Finch
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Bagne, Karen E.; Finch, Deborah M. 2012. Vulnerability of species to climate 

change in the Southwest: threatened, endangered, and at-risk species at the 

Barry M. Goldwater Range, Arizona. Gen. Tech. Rep. RMRS-GTR-284. Fort 

Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain 

Research Station. 139 p.

Abstract

Future climate change is anticipated to result in ecosystem changes, and consequently, 

many species are expected to become increasingly vulnerable to extinction. This 

scenario is of particular concern for threatened, endangered, and at-risk species 

(TER-S) or other rare species. The response of species to climate change is uncertain 

and will be the outcome of complex interactions and processes. Nevertheless, a 

simple flexible strategy is needed to help integrate climate change into management 

planning and actions. This assessment uses SAVS, an assessment tool based on 

ecological principals, to rank individual species of interest within the eastern portion 

of the Barry M. Goldwater Range, Arizona, according to predicted climate change 

responses and associated population declines balanced with responses expected 

to incur resilience or population increases. Further, specific areas of vulnerability, 

research needs, and management implications are identified for each species in 

detailed species accounts. Based solely on predicted response to climate change, 

Sonoran pronghorn (Antilocapra americana sonoriensis) and desert tortoise (Gopherus 

morafkai) are the most vulnerable to population declines. Results also suggest that 

climate change will make management of some TER-S species more difficult. Several 

critical management areas are identified that can mitigate negative impacts to benefit 

multiple species, including fire and fuels, invasive species, natural and artificial waters, 

and landscape-scale planning. Management planning should be in place that will 

assist species impacted by extreme events such as prolonged drought, severe wildfires, 

and/or intense flooding. The assessment process was also used to identify areas where 

climate change may present opportunities, as opposed to challenges, for species 

management.

Keywords: climate change, vulnerability, Southwest, Arizona, endangered species, 

SAVS

Authors

Karen E. Bagne is a Wildlife Ecologist with the USDA Forest Service, Rocky Mountain 

Research Station.

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

Ecosystem program of the USDA Forest Service, Rocky Mountain Research Station.

Cover photo: Barry M. Goldwater Range by R. Whittle. Photos are authorized for this 

publication only, and any further use requires authorization from the photographers.
Contents

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

Climate Change Assessment................................................................................1

Purpose..........................................................................................................................1

Approach........................................................................................................................2

Scope.............................................................................................................................3

Projections of Climate, Disturbance, and Biotic Communities .........................4

Current and Future Climate............................................................................................4

Water Sources ...............................................................................................................5

Disturbance....................................................................................................................5

Biotic Communities ........................................................................................................6

Mexico and Central America ..........................................................................................8

Scoring Results and Discussion ..........................................................................9

Vertebrate Species.........................................................................................................9

Vascular Plants ............................................................................................................13

Management Implications: Using Assessment Results ...................................13

Artificial and Natural Waters.........................................................................................14

Fire, Fuels, and Invasive Species Management ..........................................................15

Anticipating Shifts in Distribution..................................................................................15

Coping With Physiological Thresholds.........................................................................16

Anticipating Shifts in Timing .........................................................................................17

Prioritization .................................................................................................................17

Landscape-Scale Management and Partners..............................................................17

Uncertainty...................................................................................................................18

Next Steps.............................................................................................................18

Literature Cited.....................................................................................................19

Appendix A: Species Accounts ..........................................................................25

Couch’s Spadefoot.......................................................................................................26

Morafkai’s Desert Tortoise............................................................................................33

Saddled Leaf-nosed Snake..........................................................................................43

Red-backed Whiptail....................................................................................................49

Yuman Fringe-toed Lizard............................................................................................55

American Peregrine Falcom.........................................................................................61

Cactus Ferruginous Pygmy-Owl ..................................................................................67

Gilded Flicker ...............................................................................................................75

Le Conte’s Thrasher.....................................................................................................81

Cave Myotis .................................................................................................................87

California Leaf-nosed Bat.............................................................................................93

Mexican Long-tongued Bat ..........................................................................................99

Lesser Long-nosed Bat..............................................................................................107

Desert Bighorn Sheep................................................................................................118

Sonoran Pronghorn....................................................................................................126

Acuña Cactus.............................................................................................................135
Acknowledgments

This project was funded by the Department of Defense Legacy Resource Management 

Program (Project 09-433). Additional funding was provided by the USDA Forest 

Service. Information from the original report (posted on www.denix.osd.mil, August 

2010) was updated to create this report.

We thank Richard Whittle and Daniel Garcia of Luke Air Force Base for their support. 

Megan Friggens produced Figure 3 and, along with Sharon Coe, provided review 

and discussion of climate change topics that improved this assessment. Collaborators 

that inspired assessment development include: Carolyn Enquist and David Gori of 

The Nature Conservancy, Lisa Graumlich at the University of Arizona, and Heather 

Bateman at Arizona State University Polytechnic. Further support and advice was 

provided by Jack Triepke and Bryce Rickel of USDA Forest Service, Rocky Mountain 

Region. Mary Bagne provided editing assistance.
USDA Forest Service RMRS-GTR-284. 2012. 1

Introduction

A large number of species are imperiled and at risk of extinction if populations 

continue to decline (Wilcove and Master 2005). Of Federal landholdings, those 

managed by the Department of Defense (DoD) harbor the most endangered or 

threatened species. Those lands also contain large numbers of species at risk—those 

that are imperiled but not yet listed as endangered or threatened by the U.S. Fish 

and Wildlife Service (USFWS) (NatureServe 2004). These species, also known as 

threatened, endangered, and at-risk species (TER-S) are an important element of 

natural resource management. For species that are not listed as Federally endangered or threatened, effective and proactive management of species at risk can 

prevent listing, reduce management costs, and protect biodiversity while insuring 

that critical military training is not disrupted (NatureServe 2004). Two endangered 

vertebrate species and several candidate species are known or have the potential 

to occur in the eastern portion of the Barry M. Goldwater Range (BMGR-East) in 

southern Arizona.

Over the past century, the climate in the southwestern United States has been 

becoming warmer and drier, and this trend is expected to continue (Field and others 2007). In fact, this region is projected to be subject to a significant change 

in climate that will have broad impacts on ecosystems. Because current climate 

conditions are already physiologically challenging, even small changes can exceed species’ tolerances. There is a broad consensus among climate models that 

conditions will become more extreme (Archer and Predick 2008), which will have 

consequences for biodiversity. While the exact nature of these consequences is unknown, shifts in species distributions and changes in populations are highly likely. 

Declining populations and eventual extinction is of increasing concern for species 

already at high extinction risk that are expected to experience negative impacts 

from climate change.

Climate change is a new challenge for natural resource managers that has 

the potential to exacerbate existing management issues and create new ones. 

Preservation of biodiversity will be particularly challenging and few strategies 

have been proposed to guide managers (Lucier and others 2006). Species assessments of vulnerability or extinction risk are management tools used to help 

prioritize conservation needs so that actions can be directed in an effective and efficient manner (Glick and others 2011). Species can be ranked based on assessment 

outcome, but implementation of management actions will also be constrained by 

goals, economics, politics, and feasibility. To include climate change in a vulnerability assessment is a challenging task because the strongest climate change effects 

are not yet manifest, global carbon and nitrogen cycling are complex, species vary 

in sensitivity and adaptive capacity, and direct effects on relatively few species 

have been identified. To ignore climate change is to risk being unable to respond to 

a biodiversity crisis (McLaughlin and others 2002; Early and Sax 2011).

Climate Change Assessment

Purpose

Anticipation of future impacts of changing climate can help ameliorate those 

impacts through early intervention—a key factor for balancing ongoing and uninterrupted military operations with cost-effective natural resource management. 
2 USDA Forest Service RMRS-GTR-284. 2012.

Resources for management are also limited, thus priority targets and actions need 

to be identified (see Box 1). The purpose of this assessment is to address the vulnerability of individual TER-S to population declines associated with projected 

changes in climate at BMGR-East in southern Arizona. Pertinent projections for 

climate and biotic communities, from which climate change response is predicted, 

are summarized from the current literature. Species are ranked by anticipated vulnerability, and potential management actions are suggested based on the specific 

vulnerabilities identified. The interaction of climate change variables with currently known threats to species is also discussed.

Box 1. Why assess vulnerability?

Vulnerability is the susceptibility to negative impact. Vulnerability 

assessments help us identify where negative impacts are likely to occur 

and why. In this assessment, we define the vulnerability of terrestrial 

vertebrate species to climate change as likely declines in populations through 

either reduced survival or reproduction. Managers that use vulnerability 

assessments can:

1. Help set priorities and prepare for the future 

2. Identify adaptation strategies that target predicted effects 

3. Make more efficient use of scarce resources

Modified from Glick and others (2011)

Approach

Vulnerability of species to climate change will depend on sensitivity, exposure, 

and adaptive capacity (Glick and others 2011). We used the System for Assessing 

Vulnerability of Species (SAVS) to rank vulnerability of terrestrial vertebrates to 

climate change (Bagne and others 2011). This tool scores individual species based 

on basic ecology and life history traits that are related to climate. Traits related to 

sensitivity and adaptive capacity are integrated into the system, and exposure, or 

future projection, is considered but taken from published sources prior to scoring. 

Scores are the balance of a set of 22 traits that predict vulnerability (i.e., reduced 

survival or reproduction), resilience (i.e., increased survival or reproduction), or 

no change. Because the same set of traits is applied to all species, scores can be 

used to compare vulnerability of a set of species. The system produces an overall 

score and four category scores for habitat, physiology, phenology, and interactions 

as well as uncertainty for these scores. Each score is the balance of the number of 

vulnerable versus resilient traits, with all traits weighted equally and adjusted to 

a common scale (see Bagne and others 2011 for details). Uncertainty is based on 

the availability of information or in cases of opposing predictions for an individual 

question.We used a spreadsheet to aid score calculations, but calculations can also 

be made by hand following Bagne and others (2011) or on the SAVS web site 

(http://www.fs.fed.us/rmrs/species-vulnerability/). Traits associated with vulnerability for an individual species or that are common across several species are used 

to identify management actions to reduce vulnerability.

We developed and used a similar but separate pilot scoring tool to predict individual plant species’ vulnerability. The plant species vulnerability pilot tool is 
USDA Forest Service RMRS-GTR-284. 2012. 3

available at: http://denix.osd.mil/nr/OtherConservationTopicsAH/ClimateChange.

cfm. That tool produces an overall score and three category scores for habitat, 

physiology, and interactions as well as uncertainty for these scores in the same 

manner as SAVS.

Scope

Predicted species response and vulnerability scores are based on available 

projections of how climate and related phenomena are expected to change in the 

region of interest. Unlike the vertebrate species tool, the plant vulnerability tool 

is integrated with specific climate projections and is, thus, restricted to the southwestern United States. For this assessment, we focused on projections up to the 

next 50 years. The specific projections used for the assessment follow this section.

We assessed species with known or suspected occurrence in BMGR-East listed 

by USFWS as endangered or threatened (Figure 1). We also included additional 

species that are either proposed or under review for Federal listing or of high conservation priority for Arizona as identified by the State Wildlife Action Plan (AGFD 

2006). To provide information on a more diverse array of taxa, we also scored 

some species that were not identified as at risk, but were identified as conservation 

elements in the proposed biodiversity management framework (Hall and others 

2001). We limited this report to terrestrial vertebrate and vascular plant species. 

No plants were identified from the eastern portion of the range that were Federally 

endangered or threatened. We assessed one plant species that potentially occurs on 

BMGR-East, the acuña cactus, which is a candidate for listing. Prioritization and 

identification of vulnerabilities are presented separately for vertebrates and plants.

BMGR-East

ARIZONA

Figure 1. Map of Barry M. Goldwater Range and vicinity showing BMGR-East assessed in this document. 

Map modified from INRMP (2003).
4 USDA Forest Service RMRS-GTR-284. 2012.

Projections of Climate, Disturbance, and Biotic Communities

Current and Future Climate

The Southwest is characterized by a hot and arid climate, which is also highly 

variable because of its geographical location and positioning between two circulation regimes (Sheppard and others 2002). BMGR-East lies in a particularly hot 

and arid part of the region, but with considerable variability from east to west and 

from high to low elevations. High summer temperatures at nearby Gila Bend, averaged over the period 1892 to 2000, were over 38 °C (100 °F) with a maximum 

of 50 °C (122 °F) (INMRP 2003). In winter, average temperatures range from 

4 °C to 24 °C (40 °F to 75 °F). Recorded temperatures already indicate that the 

region is warming at a rate unprecedented in the last 400 years (Sheppard and 

others 2002). There is also evidence of fewer days below freezing and an increase 

in winter temperatures for the Sonoran Desert (Weiss and Overpeck 2005). With 

increasing levels of carbon dioxide (CO2), average annual temperature is expected 

to increase approximately 2.2 °C (4 °F) by 2050 (www.climatewizard.org, PRISM 

group, United States mid-century, 12-km resolution, downscaling based on Maurer 

and others 2007). These estimates may be too low as recent emission rates have 

exceeded those used to forecast future climate (from preliminary 2009 and 2010 

global and national estimates of carbon emissions, http://cdiac.ornl.gov).

Precipitation in the region falls in winter and in summer with a dry period from 

April to June (INRMP 2003). Average annual precipitation declines from east 

to west with 21.7 cm (8.5 inches) per year in Ajo, on the southeastern edge of 

BMGR-East, and 11 cm (4.33 inches) per year at Tacna, near the northwestern 

edge. Rainfall is higher in the mountains and may be up to 28 cm (11 inches) per 

year (INRMP 2003). Shifting of circulation patterns associated with the El Niño 

Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) alters 

winter precipitation patterns in the Southwest. Winters are wetter during El Niño 

when the westerly flow of moist air across North America shifts southward and 

are drier during La Niña when the flow shifts to the north. Changes in PDO enhance or dampen ENSO patterns (Shepperd and others 2002). During the summer, 

westerly winds diminish and a high pressure ridge forms signaling the start of the 

monsoon season, which brings moisture to the region from the Gulf of Mexico and 

the Gulf of California (Shepperd and others 2002). Unlike the widespread gentle 

rains of winter, the monsoons bring intense thunderstorms with highly variable 

local rainfall, which affects water uptake by soil and vegetation. Summer monsoonal rains fall principally in July and August and primarily on the eastern parts 

of BMGR-East. Monsoon patterns in this subregion differ from monsoons to the 

east in New Mexico, which come earlier and last into September, and monsoons 

to the south in Mexico, which also last longer and have much higher precipitation 

totals (Figure 2; Comrie and Glenn 1998).

Projections for precipitation are more varied than those for temperature. In one 

set of models, projections for winter rain (December to February) are approximately unchanged for 2050 under the current emissions rate and averaged circulation 

models (www.climatewizard.org, PRISM group, United States mid-century, 12-

km resolution, downscaling based on Maurer and others 2007). Other studies 

predict drying of the Southwest driven by changes in humidity and atmospheric 

circulation (Seager and others 2007). Periodic La Niña conditions in conjunction 

with a drying of the region are projected to bring severe and prolonged droughts 

(Seager and others 2007; Cook and others 2009). Predictions for summer monsoon 
USDA Forest Service RMRS-GTR-284. 2012. 5

rains are problematic (Mitchell and others 2002). Of note, however, is that annual 

monsoon rainfall has historically not been well correlated among the subregions 

(i.e., a dry summer does not tend to affect all subregions simultaneously), which 

has important implications for wide ranging and migratory animals.

Water Sources

The Gila River is the major watershed for BMGR-East (INRMP 2003). 

Upstream areas of the watershed are mostly located on protected lands, so climate 

change effects on water sources of BMGR-East will primarily be a direct result of 

changes to precipitation and temperature rather than related to changes in water 

diversion. Surface water is limited on BMGR-East and mostly ephemeral, and rain 

catchment basins have been modified in some places to retain water for longer 

periods (INRMP 2003). Surface water is dependent on local rainfall and thus subject to considerable alteration as climate warms and circulation patterns change. 

Unfortunately, rainfall is poorly projected, making it difficult to predict changes 

in natural water sources and run-off, but increasing rainfall variability will almost 

certainly result in greater interannual variation in the number and longevity of surface water sources. In addition, even with no change in rainfall, predicted higher 

temperatures will increase evaporation rates, resulting in less moisture available 

for plants and animals. Similarly, tinajas, where water collects in rock depressions, 

and other temporary water sources may be threatened.

Disturbance

As the climate changes, greater flood risk from more intense storms is projected 

for the southwestern United States (Garfin and Lenart 2007; Seager and others 

2007). Precipitation falling in intense rainfall events can decrease water available 

for mesic environments while potentially increasing soil water availability for 

xeric environments (Knapp and others 2008), which adds to the complexity associated with predicting species’ responses to climate change.

Figure 2. North American monsoon subregions and monthly precipitation patterns. The Barry M. Goldwater Range lies within 

subregion 2 (Comrie and Glenn 1998).
6 USDA Forest Service RMRS-GTR-284. 2012.

Wildfires are expected to become more frequent with projected increases in temperature in many regions (Rogers and Vint 1987; Swetnam and Betancourt 1990; 

Esser 1992; Westerling and others 2006). Historically, fires in the Sonoran Desert 

occurred infrequently following periods of high rainfall that produced herbaceous 

growth capable of carrying fire through usually sparse vegetation (McLaughlin 

and Bowers 1982). In conjunction with warmer temperatures, projected increases 

in climate variability will increase fire occurrence as years of high rainfall are 

followed by dry/hot years, increasing conditions conducive both to ignition and 

fuel accumulation (McLaughlin and Bowers 1982). Changes in vegetation structure and composition are also important to fire risk and are discussed in Biotic 

Communities.

Biotic Communities

BMGR-East lies in the center of the Sonoran Desert region. Major plant 

communities feature various desert scrub communities, including xeroriparian, 

creosotebush-bursage, and palo-verde mixed cacti. There are also some dune habitats in BMGR-East in the San Cristobal and Growler Valleys (INRMP 2003). 

Future vegetation will depend on the quantity and season of precipitation, which is 

not well modeled, as well as the interaction of other factors such as fire, soils, and 

topography (McPherson and Weltzin 2000).

As temperatures increase, Sonoran Desert boundaries may expand northward 

and eastward while contracting in the southeast (Weiss and Overpeck 2005). Based 

on climate modeling of biotic communities, Sonoran desertscrub is expected to 

remain the dominant biotic community at BMGR-East for at least the next 50 

years (Figure 3; Rehfeldt and others 2006). This evidence seems to suggest there 

will be little change to biotic communities of BMGR-East, but projections lack 

detail for individual plant species’ tolerances, seasonal rainfall, and interacting 

effects of disturbance that will have major impacts on biodiversity and eventual 

community composition. Of particular concern for communities in the region is 

the alteration of bimodal rainfall patterns. Summer rains are not well projected 

but are particularly important to annuals and succulents, while woody plants tend 

to rely on winter precipitation (Ehleringer and others 1991). Greater variability 

in rainfall and increasing droughts will affect xeroriparian communities because 

water tables will fall with reduced inputs. Palo-verde (Circidium microphyllum) 

is subject to periodic die-offs during droughts with higher mortality with increasing size (Bowers and Turner 2001). Analogous responses and a reduction in trees, 

particularly in larger size classes, might be expected for similar desert tree species.

Fire regimes in the region have also been altered by introduced plant species 

that provide fine fuels that carry fire. Spread of invasive plants is of particular 

concern as they can enhance the spread of fire through sparsely vegetated lands 

(Brown and Minnich 1986). In particular, grasses, which are primarily C4, may 

be favored by increases in temperature and more frequent fire occurrence (Esser 

1992). Mediterranean grass (Schismus barbatus), a C4 grass, and Sahara mustard 

(Brassica tournefortii), an annual forb, are common invasives in the region. Sahara 

mustard germinates following winter rains, has very high germination rates, and 

can form continuous stands of fuel for fires (Trader and others 2006; Lambert and 

others 2010). Red brome (Bromus rubens) also occurs but is rare on BMGR-East. 

In addition to competing for water and nutrients, these plants can increase rapidly 

during wet periods then die back leaving dry, flammable foliage and increased fire 

risk. Elevated CO2 can greatly increase productivity of plants where water and nutrients are available (Smith and others 2000). Unfortunately, in arid environments, 
USDA Forest Service RMRS-GTR-284. 2012. 7

this effect of increasing biomass is particularly strong for the non-native red brome 

during wet years, giving it further competitive advantage over native annuals 

(Smith and others 2000). Another grass of regional concern that is rapidly expanding and becoming increasingly problematic in the Sonoran Desert is buffelgrass 

(Pennisetum ciliare), a native perennial of Africa introduced for livestock grazing. 

Buffelgrass promotes a frequent high severity fire regime, which encourages further growth of these grasses while negatively impacting native desert vegetation 

(Williams and Baruch 2000). Buffelgrass is found throughout the Sonoran Desert 

region, but at BMGR-East, is known only from a few locations along State Route 

85 and the Crater Range (INRMP 2006). It is more extensive to the north along 

Interstate 8 (Van Devender and Dimmitt 2006).

Many succulent species, particularly cacti, are important elements in the natural communities of BMGR-East. Metabolism (Crassulacean acid metabolism or 

Figure 3. Current and projected climate change as modeled for the biotic communities of 

Arizona (entire Barry M. Goldwater Range outlined). Projections are from Rehfeldt and 

others (2006).
8 USDA Forest Service RMRS-GTR-284. 2012.

CAM) in cacti and other common succulent plants limits water loss by having 

stomata open at night (Smith and others 1984). Succulents are likely to survive 

drier conditions, but increases in fires, if they occur, will be detrimental as these 

plants are often prone to fire mortality. Saguaros (Carnegiea gigantea) are longlived and reproduce episodically with periods of high recruitment that are often 

followed by periods of decline (Pierson and Turner 1998). Recruitment pulses 

are also associated with frequent El Niño events, a pattern that is projected to be 

influenced by warmer temperatures. In general, however, climate is expected to 

become more variable, thus we expect some years of high moisture to occur that 

would be favorable to germination. More questionable is the duration of moist 

periods, as a sequence of wet years is needed for recruitment pulses (Pierson and 

Turner 1998). In addition, newly recruited seedlings are expected to be vulnerable 

to drought and intense flooding (Pierson and Turner 1998). Saguaro seedling survival is further reduced by competition with invasive plants, which are expected to 

increase (Morales-Romero and Molina-Freaner 2008). Cacti phenology is strongly 

influenced by temperature, and there are clear indications for earlier flowering of 

many Sonoran desert plant species including columnar and agave cacti (Bowers 

2007; Bustamante and Búrquez 2008). In particular, greater variability in fall-winter temperatures is associated with earlier production of flowers, whereas greater 

variability in mean minimum temperatures is associated with a delay in flowering 

(Bustamante and Búrquez 2008). Less precipitation and increases in extreme temperatures are likely to shorten the length of flowering season, which has a direct 

effect on fruit production (as well as nectar availability) (Bustamante and Búrquez 

2008). However, warmer winter temperatures will probably extend flowering and 

fruiting seasons in northern populations near the United States-Mexico border 

where flowering season is shorter than in more southerly regions (Bustamante and 

Búrquez 2008).

Mexico and Central America

A few species in this assessment, primarily bats and birds, migrate long distances and are subject to changing climate in regions distant from BMGR-East. 

Projected changes in pertinent regions are summarized below.

Much of Mexico also has a monsoonal precipitation pattern, but annual rainfall 

is considerably higher to the south than in the border area near Arizona and New 

Mexico (Figure 2; Comrie and Glenn 1998). Projecting changes in the climate in 

Mexico is difficult because many General Circulation Models (GCMs) are unable to adequately describe the current climate. Examining a number of models, 

it is clear that temperatures will increase for all times of year and most dramatically in northern parts of Mexico. Modeling precipitation is less certain, but most 

models predict reduced annual and summer rainfall with higher temperatures that 

will exacerbate drying through evaporation (Liverman and O’Brien 1991). At least 

currently, monsoons are generally asynchronous between northern-central Mexico 

and the Southwest borderlands (Comrie and Glenn 1998).

Increases in temperature have also been projected for Central America and, 

while precipitation projections are again more variable, most models indicate 

reduced rainfall in wet and dry seasons (Magrin and others 2007). Dry periods 

are also projected to become more extreme and accompanied by increases in extreme events including intense rain, flooding, and hurricanes (Magrin and others 

2007). Central America is also at high risk for forest loss associated with increasing temperatures (Scholze and others 2005). Increases in temperature may lead to 

conversion of semi-arid regions to arid and the shifting of high-elevation pine and 
USDA Forest Service RMRS-GTR-284. 2012. 9

pine-oak forests upslope. Increases in fire, resulting from increased temperatures 

and more variable rainfall, will reduce some tree species, such as oaks and sycamores, although mature pines should be resistant to all but high severity fires.

Scoring Results and Discussion

Vertebrate Species

Fifteen vertebrate species of BMGR-East were scored for vulnerability to climate change. Full score details and information related to individual species is in 

Appendix A. The highest score, or the species most vulnerable to population decline, was the Sonoran pronghorn (Antilocapra americana sonoriensis) (Figure 4, 

Table 1). The lowest score was the California leaf-nosed bat (Macrotus californicus), although it still had a slightly positive score close to 0, indicating a relatively 

neutral effect of climate change. Effects on gilded flicker (Colaptes chrysoides) 

were also expected to be relatively neutral overall with few predicted vulnerabilities (Table 2). No species was scored as negative or expected to benefit overall from 

climate change effects, although many species possessed resilient traits (Table 2). 

Scores do not directly translate to linear population projections because we do 

not know the relative importance of each trait in determining population change 

nor could every possible predictor of population response to climate change be 

included. Also note that although the highest overall score recorded here, 8.2, is 

well below the highest possible score of 20, this score would require the species to 

possess all 22 traits and that each of those traits predicts population decline, which 

is biologically improbable. The scores are the balance of species’ traits associated 

with vulnerability minus traits associated with resilience; thus, the score indicates 

the overall predicted direction of change while the magnitude is an indication of 

how far the balance is skewed toward vulnerable (positive) or resilient (negative) 

traits.

Figure 4. Sonoran pronghorn was 

the most vulnerable to climate 

change of the species scored. 

This male is marked with an ear 

tag. Photo by A. Alvidrez.
10 USDA Forest Service RMRS-GTR-284. 2012.

Species Habitat Physiology Phenology Interactions Overall Score Uncertainty

Sonoran pronghorn 2.1 1.7 2.5 2.0 8.2 27.0

Morafkai’s desert tortoise 2.1 0.5 3.8 1.0 7.0 18.0

Cactus ferruginous pygmy-owl 1.3 0.8 2.5 1.0 5.3 64.0

Yuman fringe-toed lizard 1.4 1.5 0.8 1.0 5.2 27.0

Red-backed whiptail -0.1 1.7 2.5 1.0 4.4 45.0

American peregrine falcon -0.1 0.8 2.5 2.0 4.4 18.0

Desert bighorn -0.1 1.5 2.5 1.0 4.3 32.0

Mexican long-tongued bat 1.3 0.7 0.8 1.0 4.1 27.0

Couch’s spadefoot 1.4 -0.3 2.1 1.0 4.1 9.0

Le Conte’s thrasher -0.8 2.5 -0.4 1.0 2.4 36.0

Cave myotis -1.1 -0.2 3.8 1.0 2.2 32.0

Lesser long-nosed bat -0.2 0.7 0.8 1.0 2.2 14.0

Saddled leaf-nosed snake -0.8 -1.0 3.8 1.0 1.5 41.0

Gilded flicker -0.8 0.8 1.3 0.0 0.8 45.0

California leaf-nosed bat -0.8 -1.2 3.8 0.0 0.5 36.0

Table 1. Climate change vulnerability scores for selected vertebrate species at BMGR-East from most vulnerable (positive) to most resilient (negative) scores. Possible scores range from -20 to 20 for overall and -5 to 5 for each category. 

Uncertainty is a percentage of scoring questions with limited information or contradictory predictions. Full scoring and 

scientific names are available in Appendix A.
USDA Forest Service RMRS-GTR-284. 2012. 11 Species

H1. Changes to Breeding Habitat

H2. Changes to Non-breeding Habitat

H3. Breeding Habitat Components

H4. Non-breeding Habitat Components

H5. Changes to Habitat Quality

H6. Dispersal ability

H7. Migration Habitats

PS1. Limiting Physiological Conditions

PS2. Temperature-determined Sex Ratios

PS3. Disturbance Events

PS4. Daily Activity Period

PS5. Adaptive Strategies

PS6. Metabolic Rate

PH1. Reliance on Climate Cues

PH2. Reliance on Discrete Resource Peaks

PH3. Activities and Resource Separation 

PH4. # of Reproductive Events per Year

I1. Changes in Food Resources

I2. Changes in Predation

I3. Symbiotic Relationships

I4. Changes in Disease

I5. Changes in Competition

Sonoran pronghorn

n

n

n

v

v

v

n

v

n

n

n

v

n

n

v

n

v

v

n

n

v

n

Morafkai’s desert tortoise

n

n

n

v

v

v

n

v

v

n

v r r v

v

n

v

v

n

n

n

n

Cactus ferruginous pygmy-owl

v

v

n

n

v r n

v

n

n

n

n

n

n

v

n

v

n

n

n

n

v

Yuman fringe-toed lizard

n

n

n

v

n

v

n

v

n

n

v

v r v

v

n r n

n

v

n

n

Red-backed whiptail

n

n

n

n

v r n

n

n

n

v

v

n

n

v

n

v

v

n

n

n

n

American peregrine falcon

n

n

n

n

n r v

n

n

n

n

v

n

n

v

n

v

v

n

n

v

n

Desert bighorn

n

n

n

n

v r n

v

n

n

v r n

n

v

n

v

n

n

n

v

n

Mexican long-tongued bat

v

v

n

n

n r v r n

v

n

v

n

n

v r v

v

n

n

n

n

Couch’s spadefoot

n

n

v

n

v

n

n

v

n

n

v r r v

v r v

v

n

n

n

n

Le Conte’s thrasher

n

n

n

n

n r n

v

n

n

v

v

n

n

v

n r v

n

n

n

n

Cave myotis r r n

n

v r v

v

n

n

n r n

n

v

v

v

n

n

n

v

n

Lesser long-nosed bat

n

v

n

n r r v r n

v

n

v

n

n

v r v

v

n

n

n

n

Saddled leaf-nosed snake

n

n

n

n

n r n

n

n

n

n

n r v

v

n

v

v

n

n

n

n

Gilded flicker

n

n

n

n

n r n

n

n

n

n

v

n

n

n

n

v

n

n

n

n

n

California leaf-nosed bat

n

n

n

n

n r n r n r n

v

n

n

v

v

v

n

n

n

n

n

Table 2. Predicted effect of climate change on individual criteria from SAVS designated by shading and letter (n = neutral, v = vulnerable, and r = resilient) for TER-S at BMGR-East. Details on SAVS are found in Bagne and others (2011). Scientific names are in Appendix A.
12 USDA Forest Service RMRS-GTR-284. 2012.

Examination of the category scores reveals more details on vulnerability 

(Table 1). Note that category scores are adjusted to be on a comparable scale because a different number of questions comprise each category. This adjustment is 

not made for overall scores where each question is of equal weight regardless of 

category. In this set of scores, a low overall score may be a result of neutral effects 

across several categories (i.e., few vulnerabilities) or a combination of vulnerable 

traits balanced by resilient traits, such as for the California leaf-nosed bat (Table 2). 

This has important implications for management and is critical to score interpretation because the relative influence of individual traits on populations is unknown.

Phenology was consistently an important category in vulnerability for most 

species (Table 1). The phenology category score reflects the relative influence of 

climate on species’ phenology, timing of resources, and the potential for timing 

flexibility. The majority of species had phenological vulnerabilities from critical 

timing tied to discrete resource peaks and inflexibility in reproductive events to 

provide resilience to those timing changes (Table 2). Ultimate outcome of these 

relationships is difficult to project because synchronicity of species to resources 

can depend on the degree of timing shifts from multiple elements. Absence of 

favorable timing predictions is partly due to the lack of knowledge about cues and 

temporal resources for many species, but we also know that timing is sensitive to 

warming and has already been detected in a broad range of species (Bradley and 

others 1999; Jenni and Kery 2003; Millar and Herdman 2004). Interactions tended 

to have neutral scores, but uncertainty was also high for this category as information on key biological interactions is often limited (Appendix A). Habitat was an 

important vulnerability category for several of the most vulnerable species despite 

the prediction of resilience of the dominant vegetation type, Sonoran desert scrub, 

in this region (Table 1 and Table 2). Predictions of habitat change based solely on 

biome shifts do not entirely capture habitat-related vulnerability and may be inadequate to use as a proxy for changes in associated species. Dispersal ability, another 

of the habitat scoring criteria, was an important area of resilience for a majority of 

species; thus, minimizing dispersal barriers will be important (Table 2).

All species scored were vulnerable rather than resilient to climate change overall. It is likely that this result is partly due to climate change exacerbating current 

stressors that are already responsible for declines in these species. Additionally, exposure or the magnitude of climate change is expected to be high in the Southwest, 

increasing vulnerability of species in the region. Although the calculation of scores 

is such that possible negative and positive scores are equal, there could be some 

other bias in scoring, such as a tendency of the scorer to favor vulnerability scores 

or some inherent factor in the system that biases it toward vulnerable (positive) 

scores. There was no clear link between uncertainty and vulnerability score, thus 

there was no obvious bias related to incomplete information (Table 1).

All taxonomic classes had similar average vulnerability with the lowest for 

birds (average = 3.2) and the highest for reptiles (average = 4.5). Members of 

these groups do not cluster together but are scattered throughout the rankings. The 

most vulnerable species, the Sonoran pronghorn, is also an endangered species, 

although the other endangered species, the lesser long-nosed bat (Leptonycteris 

yerbabuenae), was relatively less vulnerable than most other species in the assessment. Importantly, the two species under review by USFWS for listing—Sonoran 

populations of the desert tortoise (now Morafkai’s desert tortoise) and Arizona 

populations of the cactus ferruginous pygmy-owl (Glaucidium brasilianum cactorum)—are also the second and third most vulnerable in this assessment. These 

species were also more vulnerable than resilient across all categories (Figure 5). 

The scope of this assessment may be partly responsible for these patterns.
USDA Forest Service RMRS-GTR-284. 2012. 13

Vascular Plants

Only one plant species was assessed, the acuña cactus (Echinomastus erectrocentrus var. acunensis). It is a USFWS candidate for listing. It received a 

vulnerability score of 2.8 out of a maximum of 10, indicating increased vulnerability to population declines with projected climate change. The category scores, each 

with a maximum of 3, are 1.5 for habitat, -1.0 for physiology, and 2.0 for interactions. That a cactus species is also vulnerable to declines associated with climate 

change despite physiological adaptations to hot climates is an important outcome 

for management. Interactions such as fire and invasive plants may threaten habitats 

and pollinators or seed dispersal may be reduced if associated species decline or 

shift migration timing out of sync with the flowering phenology of the cactus.

Management Implications: Using Assessment Results

This assessment seeks to help clarify the threat of climate change to individual species and identify potential management actions. Management of TER-S, 

however, is not exclusively based on vulnerability, nor is climate change the only 

potential threat to species. Feasibility, economics, and political considerations all 

play a role in management decisions, but are outside the scope of this assessment. 

Other aspects of prioritization such as population trends or genetic uniqueness are 

also considerations (Given and Norton 1993). Management actions are likely to be 

more effective and targeted if priorities and potential impacts are clear.

During scoring, we kept our focus on the coming decades that, while more conservative than longer outlooks, are of more practical use to current management 

and are more projectable. Below, we summarize management themes gleaned 

from the individual species accounts, which contain detailed information for each 

species (see Appendix A). These themes suggested target areas for management 

Figure 5. Vulnerability category 

and overall scores for 

endangered species (E), 

Federal candidate species, or 

Federal species of concern at 

BMGR-East. Scientific names 

appear in Appendix A.
14 USDA Forest Service RMRS-GTR-284. 2012.

that were common to multiple species (Table 3). For example, vulnerability related 

to heat tolerance may be mitigated through managing for plants that provide shade 

or by providing drinking water sources. Habitats threatened by increased fire may 

be protected by removing invasive plants or creating fire breaks. Often called adaptation strategies, these actions reduce the impacts of climate change or increase 

resilience of species or their habitats. Other management strategies may focus on 

reducing current threats to species, including those that may be exacerbated by 

climate change such as water withdrawals, border traffic, and energy development. 

Management implications are general recommendations from the assessment that 

should be considered for species management and not as a critique of current management programs.

Artificial and Natural Waters

Artificial waters are widely used in wildlife management in the Southwest, although the benefits and potential negative impacts are not well quantified (Broyles 

1995). Regardless, increasing droughts and high temperatures will likely make 

these water sources critical to many species as water requirements increase. This 

situation may also apply to species that can usually satisfy most of their water 

needs through diet when faced with more extreme conditions. The majority of 

modified natural water catchments on BMGR-East are located in the Sand Tank 

and Sauceda Mountains (INRMP 2003). Current and proposed natural and artificial waters on BMGR-East, including valley locations, should be evaluated for 

availability to a wide variety of species under drought conditions. Rosenstock and 

Species

Fire/Invasive PlantsWater 

sources

Vehicular 

traffic

Shade and 

microsites

Corridors and 

dispersal

Timing 

restrictions

Sonoran pronghorn x x x x x

Morafkai’s desert tortoise x x x x x

Cactus ferruginous pygmyowl x x

Yuman fringe-toed lizard x x x

Red-backed whiptail x x

American peregrine falcon x x

Desert bighorn x x x

Mexican long-tongued bat x x

Couch’s spadefoot x x x x

Le Conte’s thrasher x (x) x x x

Cave myotis x x

Lesser long-nosed bat x x

Saddled leaf-nosed snake x

Gilded flicker x

California leaf-nosed bat x

Acuña cactus x x

Table 3. Summary of common management target areas for reducing anticipated climate change threats to individual species on BMGR-East. This list is not comprehensive but includes areas that were shared by multiple species and that have 

the potential to reduce climate change vulnerability. Specific management actions may differ for species within the same 

target area. “Timing restrictions” refers to altering dates when activities are restricted. Options marked “(x)” may have 

response to management in the opposite direction to other species. Scientific names appear in Appendix A.
USDA Forest Service RMRS-GTR-284. 2012. 15

others (2004) provided detailed analysis and recommendations for water enhancements. Evaluation of future suitability of water enhancements should pay particular 

attention to substrates, capacity and annual longevity, habitat surroundings, special 

species requirements, disease transmission, and potential for supplemental water 

inputs. Accordingly, artificial waters may need to be expanded or modified.

Fire, Fuels, and Invasive Species Management

As previously described, conditions conducive to fire ignition and spread are 

expected to increase. Because individual species respond differently to fire, fires 

that burn very large areas or encourage conversion to non-native vegetation are of 

the most concern from a biodiversity perspective. Xeroriparian habitats, for example, may be more vulnerable as the denser vegetation provides more fuel for fires. 

Of particular concern in this region is the interplay between climate, fire, and invasive species, which could degrade habitats for a wide variety of species (Figure 6).

Management of non-native plants, rather than fuel management, will be key as a 

number of non-native plants play a major role in altering fire regimes and can outcompete native grasses and forbs. Measures that prevent introductions and spread 

will be essential and less costly than control measures after non-natives have become established. Critical areas for control may include locations of known TER-S 

or adjacent to habitats with TER-S, dispersal sources such as along roads, and 

areas with increased ignition risk. Elevated CO2 may also exacerbate competitive dominance of non-natives, particularly during wet years, and managers should 

anticipate annual variability in the need for invasive species control measures. 

Increasing drought periods, however, may reduce red brome and other invasives 

that lack persistent seed banks and can present opportunities for effective control 

(Burgess and others 1991; Salo 2004).

Anticipating Shifts in Distribution

Depending on a wide variety of factors, including dispersal ability, physiological thresholds, and vegetation response, populations may shift in distribution as 

local climate changes. From the perspective of a management unit, these shifts 

will be observed as a change in numbers regardless of the greater population. 

Management efforts will be better spent on species that are less able to shift with 

changing habitats than on those that are disappearing from BMGR-East but increasing elsewhere. Shifting of habitats or populations should also be anticipated 

for geographically based protected areas or designated critical habitat. Managers 

Figure 6. Species like the desert tortoise are 

vulnerable to loss of habitat, including loss of 

cactus, an important food and water source, and 

shrubs that provide shade. Increases in invasive 

grasses and frequency of fires will accelerate 

habitat change. Photo by D. Garcia.
16 USDA Forest Service RMRS-GTR-284. 2012.

will need to reevaluate the future suitability of current or proposed protected 

areas. Drier or more variable conditions may shift timing and locations of foraging habitats for species like the Sonoran pronghorn or the lesser long-nosed bat. 

Although we did not assess species that do not occur at BMGR-East, new species 

may disperse to the region that require inclusion in management planning. We anticipate some migratory species limited by cold winter conditions to increase use 

of BMGR-East toward year-round residency. Summer conditions will likely limit 

expansion of new species into the region that are not already tolerant of high temperatures. Monitoring can help identify species in the early stages of expansion.

Movements and migrations are partly adaptations to changing conditions, thus 

species may reduce vulnerability by shifting with climate. To facilitate population shifts, corridors will be an important part of managing species under climate 

change. Of particular concern are the highway barriers that prevent some species 

from moving to the more mesic environments of the Gila River and Río Sonoyta. 

These movements are likely critical during drought periods for individual survival. 

This conditional migration is particularly relevant to sustaining Sonoran pronghorn populations.

It may be necessary in some cases to assist the migration process to prevent 

extinction. Generally known as assisted migration, individuals are moved to new, 

presumably favorable locations outside of their historic range. Costs can be high, 

and the nature of climate change is such that new locations cannot be expected 

to remain suitable in the long term. Introduction of species to new regions is also 

fraught with problems, including disruption of species interactions, hybridization, 

and unpredictable outcomes (Ricciardi and Simberloff 2009). Translocations that 

include recent historical range (i.e., reintroductions) eliminate many of these issues, but may be of questionable benefit in the long term as the climate continues 

to warm. Conversely, translocations may be beneficial for climate change management as new locations may include more favorable microsites, help reduce the risk 

of stochastic events, offer better natural dispersal opportunities, or buy time until 

further actions can be evaluated. Falk and others (1996) provided guidelines for 

rare plant reintroductions.

Coping With Physiological Thresholds

Although physiological limitations may shift species’ distributions, limitations 

will also add to stress manifested as poor survival or reproduction (Bernardo and 

Spotila 2006). On initial consideration, desert species might be expected to be resilient to increasing heat and aridity, which are the conditions they are adapted to. 

This idea ignores the relatively narrow window of adaptation available at the upper physiological thresholds that may make species in extreme environments more 

rather than less vulnerable (Pörtner 2001; Stillman 2003; Hargrove 2010; Sinervo 

and others 2010). TER-S are at a particular disadvantage for physiological stress, 

as their small population size will limit adaptation through natural selection. In 

addition, little is known about physiological tolerances of species under projected 

future conditions. In this assessment, we assumed tolerances would be exceeded 

for those species already prone to drought mortality or inhabiting the most extreme 

environments, but this topic needs more study and will be dependent on future 

greenhouse gas emission rates.

Although an entire management area can become physiologically unsuitable, 

it is likely that some favorable microsites will remain, at least for the near future. Besides the management of artificial and natural waters already discussed, 

managers can take advantage of variation in environmental conditions across the 
USDA Forest Service RMRS-GTR-284. 2012. 17

landscape and direct protection or enhancements to favorable microsites. In this 

assessment, limitations of high heat or low moisture were the most concerning, 

thus priority could be given to microsites with suitable habitat that are cool and 

moist, such as north-facing slopes or canyon bottoms. Microsites that provide 

shade are important to thermoregulation (Walsberg 1993) and management that 

encourages shade plants could be of benefit to some species. Xeroriparian areas 

are important for a number of TER-S as well as migrating bird species and likely 

provide important thermal refuges from the more sparse and exposed adjacent vegetation. Managers should also note that more mesic microsites and shaded areas 

are also more prone to invasion by non-native annuals (Brooks 1999). In addition, 

because drought is a limiting factor for many of these species, managers should 

include drought effects in planning documents and anticipate the possible need for 

intervention.

Anticipating Shifts in Timing

Phenology is an important aspect of life history and is often sensitive to climate 

conditions. It also was the category most associated with vulnerability for vertebrate species in this assessment (Table 1) and is a potential issue for plant species 

that are pollinated or dispersed by animals. Management that is time sensitive, 

such as restricting activities during breeding of a target species, needs to anticipate 

that timing will change and restrictions must track those changes. Although timing 

of individuals is not readily managed, in some cases, management can affect the 

timing of resources, such as the presence and duration of temporary pools.

Prioritization

The apparent vulnerability of most TER-S on BMGR-East to climate change 

highlights the challenges that will face managers and the need for proactive solutions. Managers already make choices about where to focus resources, but as 

stresses on species magnify, there will likely be an increasing need to prioritize 

species and/or actions. Identification of vulnerabilities suggests target areas for effective management, some of which can affect multiple species (Table 3). Scores 

from this assessment can be used to aid decisions by identifying species most vulnerable to the additional impact of climate change and the species’ traits associated 

with vulnerabilities. Species that are expected to be resilient may require management if they negatively impact TER-S. Ranks in this assessment are based on the 

number of predicted vulnerabilities across species for the same set of criteria, but 

likely do not directly translate to a linear progression of population change because some traits may have threshold effects or may be limiting factors. Obviously, 

predictions of climate and vulnerability are uncertain, but an assessment, even if 

limited, can provide input when no other information is available and serve as a 

starting point for beginning to address species management under climate change.

Landscape-Scale Management and Partners

Perhaps one of the greatest challenges for managing species under future climate is that with continued greenhouse gas emissions, the future is not a steady 

state. Most management planning, however, focuses on the next 10 to 20 years 

and we assessed species with that timeline in mind. Partners will be extremely 

valuable, and managers from adjacent lands will be experiencing similar climate 

conditions and issues. Management at a landscape scale is well suited for climate 
18 USDA Forest Service RMRS-GTR-284. 2012.

change issues, as well as being cost effective. Cooperative approaches can allow 

more flexibility and help to balance the costs and benefits of competing needs. For 

example, cooperative monitoring at a large scale can separate population shifts 

from regional declines and detect newly arriving species early. Natural variability 

in local conditions at a landscape scale will also be important for many aspects of 

species’ responses to climate as identified here. For example, temperature variation across a broad landscape may help ensure variation in population sex ratios 

for species such as desert tortoise. BMGR-East is well situated for landscape-scale 

management; in addition to comprising a large geographic area, it is surrounded by 

large, undeveloped public and tribal lands.

Uncertainty

Although drawn from basic life history and ecology, in many instances, uncertainty arose during the scoring process because of lack of information. Deficiencies 

were common in a few key areas for vertebrates, but were more extensive for 

plant species and ultimately limited the scoring criteria available. Lack of information was doubly problematic for interactions as few key interacting species (e.g., 

prey, predators, pollinators, and disease vectors) were known, nor were there often climate change projections for these species. Despite limitations in prediction, 

we felt it was important to include critical relationships of species with climate. 

Uncertainties were used to identify research priorities, which are noted in the 

individual species accounts (Appendix A). Predicting the future is inherently uncertain, but the exercise of prediction will improve as better models are developed 

and more research is conducted.

Next Steps

Vulnerability and resilience predictions are based on responses that are likely a 

matter of degree and are dependent on the strength or duration of projected changes. This assessment is not meant to substitute for more thorough and complex 

analyses of the climate change response of individual species, but those approaches will also be limited in their ability to predict the future. Predictions for plant 

species were particularly difficult to make using this approach and may be more 

suitable for modeling techniques based on climate envelope or niche modeling 

than vertebrate species. The scoring systems used in this assessment are simple and 

flexible by design. Scores can easily be modified to reflect any future changes in 

projections, although we suspect these will make little difference to the outcome. 

Managers are encouraged to apply scoring to additional species or to use their 

knowledge to modify the scoring of species included here. By focusing on ecology 

and life history traits, these scoring systems can take advantage of the considerable 

knowledge of local resource managers rather than depend on expertise in modeling 

or computer simulations that need to be tailored to particular species or regions.

This assessment can help identify management targets, including species and 

actions. Information from assessments can also be used as part of more complex 

multi-species or landscape planning such as outlined by Lawson and others (2008). 

In addition, this assessment highlights different pathways by which populations 

can be affected by climate, which is important for initiating dialogue and finding solutions. Predicting effects on individual species is inherently complex and 

primarily speculative at this point, but we believe that the need for managers to 

address climate change is becoming more urgent (Thomas and others 2004) and 
USDA Forest Service RMRS-GTR-284. 2012. 19

tools, regardless of their limitations, are needed now. We also want to emphasize 

that managing for climate change is not just about challenges, but also about opportunities (Box 2). While the assessment process and the product are inherently 

imprecise, this effort is an important first step toward anticipating and responding 

to climate change, and it provides a framework for integrating new research and 

information.

Box 2. Seizing Opportunity

Although climate change will present challenges to species and their 

management, opportunites will likely be presented as well. The shifting of species distributions can mean a local reduction in an undesirable 

species, such as an alien plant species (Bradley 2009), or an improvement for a new species, such as a species that shifts its distribution from a 

degraded habitat to a protected area. Natural resource managers can take 

advantage of increasing climate variability to implement actions during 

the most favorable conditions. For example, drought in arid systems can 

sometimes favor native species over non-native species, assisting weed 

control (Salo 2004). During wet periods, planting or natural recruitment 

in combination with grazing may improve seedling establishment of 

woody species (Holmgren and Sheffer 2001). Translocation or corridor 

enhancements to encourage animal dispersal may be most successful 

during wet years associated with high reproductive success. The climate 

change challenge may also serve as a catalyst to promote adaptive management strategies, highlight sustainability, and foster partnerships.

Literature Cited

Arizona Game and Fish Department (AGFD). 2006. DRAFT. Arizona’s 

comprehensive wildlife conservation strategy: 2005-2015. Arizona Game and 

Fish Department, Phoenix, Arizona.

Archer, S. R. and K. I. Predick. 2008. Climate change and ecosystems of the 

southwestern United States. Rangelands 30:23-28.

Arriaga, L., A. E. Castellanos, E. Moreno, and J. Alarcon. 2004. Potential ecological 

distribution of alien invasive species and risk assessment: a case study of buffel 

grass in arid regions of Mexico. Conservation Biology 18:1504-1514.

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

vulnerability of species (SAVS) to climate change. USDA Forest Service, Rocky 

Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257. Online at: http://

www.fs.fed.us/rm/grassland-shrubland-desert/products/species-vulnerability/

savs-climate-change-tool.

Bernardo, J. and J. Spotila. 2006. Physiological constraints on organismal response 

to global warming: mechanistic insights from clinally varying populations and 

implications for assessing endangerment. Biology Letters 2:135-139.

Bowers, J. E. and R. M. Taylor. 2001. Dieback and episodic mortality of Cercidium 

microphyllum (foothill paloverde), a dominant Sonoran Desert tree. Journal of 

the Torrey Botanical Society 128:128-140.
20 USDA Forest Service RMRS-GTR-284. 2012.

Bradley, N. L., A. C. Leopold, J. Ross, and W. Huffaker. 1999. Phenological changes 

reflect climate change in Wisconsin. Proceedings of the National Academy of 

Sciences of the United States of America 96:9701-9704.

Brooks, M. L. 1999. Habitat invasibility and dominance by alien annual plants in 

the western Mojave Desert. Biological Invasions 1:325-337.

Brown, D. E., and R. A. Minnich. 1986. Fire and changes in creosote bush scrub 

of the western Sonoran desert, California. American Midland Naturalist 

116:411-422.

Broyles, B. 1995. Desert wildlife water developments: questioning use in the 

Southwest. Wildlife Society Bulletin 23:663-675.

Burgess, T. L., J. E. Bowers, and R. M. Turner. 1991. Exotic plants at the desert 

laboratory, Tucson, Arizona. Madroño 38:96-114.

Burquez-Montijo, A., M. Miller, and A. Martinez-Yrizar. 2002. Mexican 

grasslands, thornscrub, and the transformation of the Sonoran Desert by invasive 

exotic buffelgrass. Pages 126-146 In B. Tellman, ed., Arizona-Sonoran Desert 

Museum Studies in Natural History, Tucson, AZ.

Comrie, A. C. and E. C. Glenn. 1998. Principal components-based regionalization 

of precipitation regimes across southwest United States and northern Mexico, 

with an application to monsoon precipitation variability. Climate Research 

10:201-215.

Cook, E. R., R. Seager, R. R. Heim, Jr., R. S. Vose, C. Herweijer, and C. 

Woodhouse. 2009. Megadroughts in North America: placing IPCC projections 

of hydroclimatic change in a long-term palaeoclimate context. Journal of 

Quaternary Science 25:48-61.

Early, R. and D. F. Sax. 2011. Analysis of climate paths reveals potential limitations 

on species range shifts. Ecology Letters 14:1125-1133.

Esser, Gerd. 1992. Implications of climate change for production and decomposition 

in grasslands and coniferous forests. Ecological Applications 2:47-54.

Falk, D., C. Millar, and M. Olwell. 1996. Part Five: Guidelines for Preparing a 

Rare Plant Reintroduction Plan. Pages 454-490 In D. Falk, C. Millar, and M. 

Olwell, eds., Restoring Diversity: Strategies for Reintroduction of Endangered 

Plants. Island Press, Washington, DC.

Field, C. B., L. D. Mortsch, M. Brklacich, D. L. Forbes, P. Kovacs, J. A. Patz, S. 

W. Running, and M. J. Scott. 2007. North America. Pages 617-652 In M. L. 

Parry, 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 University Press, Cambridge, UK.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water 

resources. Southwest Hydrology 6:16-17.

Given, D. R. and D. A. Norton. 1993. A multivariate approach to assessing threat 

and priority setting in threatened species conservation. Biological Conservation 

64:57-66.

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

Horizon: A Guide to Climate Change Vulnerability Assessment. National 

Wildlife Federation, Washington, DC.

Graham, E. A. and P. S. Nobel. 1996. Long term effects of a doubled atmospheric 

CO2 concentration on the CAM species Agave deserti. Journal of Experimental 

Botany 47:61-69.
USDA Forest Service RMRS-GTR-284. 2012. 21

Graham, R. T., S. McCaffrey, and T. B. Jain, tech. eds. 2004. Science basis for 

changing forest structure to modify wildfire behavior and severity. Gen. Tech. 

Rep. RMRS-GTR-120. Fort Collins, CO: U.S. Department of Agriculture, 

Forest Service, Rocky Mountain Research Station. 43 p.

Hall, J. A., P. Comer, A. Gondor, R. Marshall, and S. Weinstein. 2001. Conservation 

Elements of and a Biodiversity Management Framework for the Barry M. 

Goldwater Range, Arizona. The Nature Conservancy of Arizona, Tucson.

Hargrove, L. J. 2010. Limits to species’ distributions: spatial structure and dynamics 

of breeding bird populations along an ecological gradient. Dissertation. 

University of California, Riverside, CA.

Holmgren, M. and M. Scheffer. 2001. El Niño as a window of opportunity for the 

restoration of degraded arid ecosystems. Ecosystems 4:151-159.

Integrated Natural Resources Management Plan (INRMP). 2003. Final 

environmental impact statement for Barry M. Goldwater Range: volume I. U.S. 

Department of the Air Force, U.S. Department of the Navy, U.S. Department of 

the Interior, and Arizona Game and Fish Department.

Jenni, L. and M. Kéry. 2003. Timing of autumn bird migration under climate 

change: advances in long-distance migrants, delays in short-distance migrants. 

Proceedings of the Royal Society 270:1467-1471.

Kelly, A. and M. Goulden. 2008. Rapid shifts in plant distribution with 

recent climate change. Proceedings of the National Academy of Sciences 

USA 105:11823-11826.

Knapp, A. K., C. Beier, D. D. Briske, [and others]. 2008. Consequences of more 

extreme precipitation regimes for terrestrial ecosystems. Bioscience 58:811-821.

Lambert, A., C. D’Antonio, and T. Dudley. 2010. Invasive species and fire in 

California ecosystems. Fremontia 38:29:36.

Lawson, D., H. Regan, and T. Mizerek. 2008. Multi-species management using 

modeling and decision theory: applications to integrated natural resources 

management planning. DoD Legacy Program Report, Project 05-264.

Lenoir, J. J., C. Gegout, P. A. Marquet, P. de Ruffray, and H. Brisse. 2008. A 

significant upward shift in plant species optimum elevation during the 20th

century. Science 320:1768-1771.

Liverman, D. M. and K. L. O’Brien. 1991. Global warming and climate change 

in Mexico. Pages 351-364 In Global Environmental Change. ButterworthHeinemann Ltd.

Lucier, A., M. Palmer, H. Mooney, K. Nadelhoffer, D. Ojima, and F. Chavez. 

2006. Ecosystems and climate change: research priorities for the U.S. Climate 

Change Science Program. Recommendations from the scientific community. 

Report on an ecosystems workshop, prepared for the Ecosystems Interagency 

Working Group. Special Series No. SS-92-06, University of Maryland Center 

for Environmental Science, Chesapeake Biological Laboratory, Solomons, MD. 

50 p.

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 M.L. Parry, 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 University Press, Cambridge, UK: 581-615.
22 USDA Forest Service RMRS-GTR-284. 2012.

Maurer, E. P., L. Brekke, T. Pruitt, and P. B. Duffy. 2007. Fine-resolution climate 

projections enhance regional climate change impact studies, Eos Trans. AGU 

88:504.

McLaughlin, J. F., J. J. Hellmann, C. L. Boggs, and P. R. Ehrlich. 2002. Climate 

change hastens population extinctions. Proceedings of the National Academy of 

Sciences 99:6070-6074.

McLaughlin, S. E. and J. P. Bowers. 1982. Effects of wildfire on a Sonoran Desert 

plant community. Ecology 63:246-248.

McPherson, G. R. and J. F. Weltzin. 2000. Disturbance and climate change in 

United States/Mexico borderland plant communities: a state-of-the-knowledge 

review. USDA Forest Service, Gen. Tech. Rep. RMRS-GTR-50.

Millar, J. and E. Herdman. 2004. Climate change and the initiation of spring 

breeding by deer mice in the Kananaskis Valley, 1985-2003. Canadian Journal 

of Zoology 82:1444-1450.

Minnich, R. A. and Y. H. Chou. 1997. Wildland fire patch dynamics in the Chaparral 

of southern California and northern Baja California. International Journal of 

Wildland Fire 7:221-248.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf 

of California sea surface temperatures and the North American monsoon: 

mechanistic implications from observations. Journal of Climate 15:2261-2281.

Morales-Romero, D. and F. Molina-Freaner. 2008. Influence of buffelgrass pasture 

conversion on the regeneration and reproduction of the columnar cactus, 

Pachycereus pecten-aboriginum, in northwestern Mexico. Journal of Arid 

Environments 72:228-237.

NatureServe. 2004. Species at risk on Department of Defense installations: revised 

report and documentation. Report (Legacy 03-154) prepared for Department of 

Defense and U.S. Fish and Wildlife Service.

Pierson, E. and R. Turner. 1998. An 85-year study of Saguaro (Carnegiea gigantea) 

demography. Ecology 79:2676-2693.

Pörtner, H. O. 2001. Climate change and temperature-dependent biogeography: 

oxygen limitation of thermal tolerance in animals. Naturwissenschaften 

88:137-146.

Rehfeldt, G. E., N. L. Crookston, M. V. Warwell, and J. S. Evans. 2006. 

Empirical analyses of plant-climate relationships for the western United States. 

International Journal of Plant Sciences 167:1123-1150.

Ricciardi, A. and D. Simberloff. 2009. Assisted colonization is not a viable 

conservation strategy. Trends in Ecology and Evolution 24:248-253.

Richter, B., R. Mathews, D. Harrison, and R. Wigington. 2003. Ecologically 

sustainable water management: managing river flows for ecological integrity. 

Ecological Applications 13:206-224.

Robinett, D. 1994. Fire effects on southeastern Arizona Plains grasslands. 

Rangelands 16:143-148.

Rogers, G. F. and M. K. Vint. 1987. Winter precipitation and fire in the Sonoran 

Desert. Journal of Arid Environments 13:47-52.

Rojas-Martinez, A., A. Valiente-Banuet, M. del Coro Arizmendi, A. AlcantaraEguren, and H. T. Arita. 1999. Seasonal distribution of the long-nosed bat 

(Leptonycteris curasoae) in North America: does a generalized migration 

pattern really exist? Journal of Biogeography 26:1065-1077.
USDA Forest Service RMRS-GTR-284. 2012. 23

Rosenstock, S. S., M. J. Rabe, C. S. O’Brien, and R. B. Waddell. 2004. Studies 

of wildlife water developments in southwestern Arizona: wildlife use, water 

quality, wildlife diseases, wildlife mortalities, and influences on native 

pollinators. Arizona Game and Fish Department, Research Branch Technical 

Guidance Bulletin No. 8, Phoenix. 15 p.

Salo, L. F. 2004. Population dynamics of red brome (Bromus madritensis subsp. 

rubens): times for concern, opportunities for management. Journal of Arid 

Environments 57:291-296.

Scholze, M., W. Knorr, N. W. Arnell and I. C. Prentice. 2005. A climate change 

risk analysis for world ecosystems. Proceedings of the National Academy of 

Sciences 103:13116-13120.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent 

transition to a more arid climate in southwestern North America. Science 

316:1181-1184.

Serrat-Capdevila, A., J. B. Valdes, J. G. Perez, K. Baird, L. J. Mata, and T. Maddock. 

2007. Modeling climate change impacts and uncertainty on the hydrology of a 

riparian system: the San Pedro Basin (Arizona/Sonora). Journal of Hydrology 

347:48-66.

Shepperd, P., A. Comrie, G. Packin, K. Angersbach, and M. Hughs. 2002. The 

climate of the US Southwest. Climate Research 21:219-238.

Sinervo, B., F. Méndez-de-la-Cruz, D. B. Miles,[and others]. 2010. Erosion of lizard 

diversity by climate change and altered thermal niches. Science 328:894-899.

Smith, S. D., B. Didden-Zopfy and P. S. Nobel. 1984. High-temperature responses 

of North American cacti. Ecology 65:643-651.

Smith, Stanley D., Travis E. Huxman, Stephen F. Zitzer, Therese N. Charlet, David 

C. Housman, James S. Coleman, Lynn K. Fenstermaker, Jeffrey R. Seemann, 

and Robert S. Nowak. 2000. Elevated CO2 increases productivity and invasive 

species success in an arid ecosystem. Nature 408:79-82.

Stephens, S. L. and L. W. Ruth. 2005. Federal forest-fire policy in the United 

States. Ecological Applications 15:532-542.

Stillman, J. H. 2003. Acclimation capacity underlies susceptibility to climate 

change. Science 301:65.

Stromberg, J. C. 1998. Dynamics of Fremont cottonwood (Populus fremontii) and 

saltcedar (Tamarix chinensis) populations along the San Pedro River, Arizona. 

Journal of Arid Environments 40:133-155.

Stromberg, J. C., S. J. Lite, T. J. Rychener, L. Levick, M. D. Dixon, and J. W. 

Watts. 2006. Status of the riparian ecosystem in the upper San Pedro River, 

Arizona: Application of an assessment model. Environmental Monitoring and 

Assessment 115:145-173.

Stromberg, J. C., R. Tiller, and B. Richter. 1996. Effects of groundwater decline 

on riparian vegetation of semiarid regions: the San Pedro, Arizona. Ecological 

Applications 6:113-131.

Swetnam, T. W. and Betancourt, J. L. 1990. Fire-Southern Oscillation relations in 

the southwestern United States. Science 249:1017-1021.

Thomas, C. D., A. Cameron, R. E. Green, [and others]. 2004. Extinction risk from 

climate change. Nature 427:145-148.

Thomas, P. A. 2006. Mortality over 16 years of cacti in a burnt desert grassland. 

Plant Ecology 183:9-17.
24 USDA Forest Service RMRS-GTR-284. 2012.

Trader, M., M. Brooks, and J. Draper. 2006. Seed production by the non-native 

Brassica tournefourtii (Sahara mustard) along desert roadsides. Madroño 

53:313-320.

Vásquez-León, M., C. T. West, and T. J. Finan. 2003. A comparative assessment of 

climate vulnerability: agriculture and ranching on both sides of the US-Mexico 

border. Global Environmental Change 13:159-173.

Van Devender, T. R. and M. A. Dimmitt. 2006. Final report on conservation of 

Arizona upland Sonoran Desert habitat: Status and threats of buffelgrass 

(Pennisetum ciliare) in Arizona and Sonora. Arizona-Sonora Desert Museum, 

Tucson, AZ.

Walsberg, G. E. 1993. Thermal consequences of diurnal microhabitat selection in 

a small bird. Ornis Scandinavica 24:174-182.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global 

Change Biology 11:2065-2077.

Westerling, A. L., H. G. Hidalgo, D. R. Cayan, and T. W. Swetnam. 2006. Warming 

and earlier spring increase western U.S. forest wildfire activity. Science 

313:940-943.

Wilcove, D. S. and L. L. Master. 2005. How many endangered species are there in 

the United States? Frontiers in Ecology and the Environment 3:414-420.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: 

ecosystem consequences and the role of ecophysiology. Biological Invasions 

2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 25

Appendix A: Species Accounts
26 USDA Forest Service RMRS-GTR-284. 2012.

Couch’s Spadefoot

(Scaphiopus couchii)

SUMMARY

The reliance of Couch’s spadefoot on rainfall for suitable foraging and breeding conditions makes this species 

particularly vulnerable to future alterations of quantity or timing of rainfall. Conversely, this species is well 

adapted to fluctuating resources, thus vulnerability is reduced relative to many desert amphibians. Protection 

of playas and management of corridors during explosive breeding events will benefit this species.

VULNERABILITY Score Uncertainty

Habitat 1.4 14%

Physiology -0.3 0%

Phenology 2.1 0%

Interactions 1.0 20%

Overall 4.1 9%

Introduction

Couch’s spadefoot is not particularly rare nor is it endemic to the Sonoran desert, but spadefoots are closely 

tied to ephemeral rainfall patterns and, thus, are also closely tied to climate. It is also one of the few relatively 

common amphibians on BMGR (Hall and others 2001). In addition, it is one of the ephemeral water-breeding 

amphibians identified as a conservation element in the proposed biodiversity management framework for 

BMGR (Hall and others 2001).

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main document.

-5 0 5

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0
USDA Forest Service RMRS-GTR-284. 2012. 27

Other Threats and Interactions With Climate

Couch’s spadefoot is fairly common in southern Arizona but faces a number of threats, including habitat 

degradation. Although these threats are perhaps fewer than those faced by amphibians that are more aquatic, 

populations of this and similar species are also poorly studied because of their limited surface activities. 

Larvae are exposed to ultraviolet radiation, pollutants, disease, and predators, but these effects are somewhat 

reduced in the temporary pools that are generally favored. Threats may be increased for more permanent 

waters such as stock tanks, but with warming temperatures, these habitats may become increasingly 

important.

Research Needs

A number of features of this species, such as having two larval morphs and the ability to aestivate for long 

periods, are thought to give this species resilience to resource variation, but information is limited. These 

resiliencies have not been evaluated under future climate projections and may, on more detailed analysis, 

be found to be insufficient to maintain populations. For example, what are the population consequences of 

increasing proportions of carnivorous larvae as ponds dry faster? Little is known about suitability of different 

types of breeding ponds, but this could be important for populations as the availability of water sources 

change.

Management Implications

Playas and other areas that collect rainwater and have suitable soils for aestivation will be especially critical 

and should be protected from potentially harmful activities such as vehicle use. With greater variability 

in rainfall projected, temporary management for suitable and safe corridors will also be important to this 

species, particularly during periods of explosive breeding. Timing changes to breeding should also be 

anticipated and considered when establishing timing restrictions on potentially detrimental activities.
28 USDA Forest Service RMRS-GTR-284. 2012.

Habitat:	
  Couch’s	
  spadefoot	
  (Scaphiopus	
  couchii)

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	
  various	
  mesquite	
  and	
  creosote	
  flats,	
  mesquite	
  

bosque,	
  shortgrass	
  prairie,	
  and	
  irrigated	
  agricultural	
  

lands	
  (Degenhardt	
  and	
  others	
  1996)	
  of	
  Sonoran	
  and	
  

Chihuahuan	
  deserts	
  in	
  Arizona	
  (Brennan	
  and	
  Holycross	
  

2006).	
  Particularly	
  occurs	
  near	
  playas	
  (Hall	
  and	
  others

2001).	
  Although	
  grasslands	
  may	
  increase,	
  Couch’s	
  

spadefoot	
  also	
  uses	
  desert	
  scrub	
  habitats	
  and,	
  combined,

these	
  vegetation	
  types	
  are	
  expected	
  to	
  remain	
  

approximately	
  the	
  same.	
  

0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Requires	
  breeding	
  ponds (Degenhardt	
  and	
  others	
  1996),	
  

which	
  will	
  be	
  less	
  common	
  and	
  more	
  ephemeral	
  with	
  

decreased	
  rainfall	
  and	
  greater	
  evaporation. Also	
  observed	
  

using	
  stock	
  ponds	
  for	
  breeding. 1

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Needs	
  loose	
  soil	
  or	
  animal	
  burrows	
  to	
  aestivate (Ruibal	
  

and	
  others	
  1969).	
  Suitable	
  soils	
  will	
  be	
  unaffected	
  by	
  

climate.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Deeper	
  soils	
  associated	
  with	
  better	
  survival(Ruibal	
  and	
  

others	
  1969).	
  Likely	
  unaffected.	
  Longer	
  pond	
  duration	
  

associated	
  with	
  better	
  survival	
  of	
  larvae (Degenhardt	
  and	
  

others	
  1996),	
  and	
  projected	
  changes	
  in	
  climate	
  are	
  likely	
  

to	
  lead	
  to	
  shorter	
  pond	
  duration.

1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Occasional	
  dispersal	
  of	
  long	
  distances,	
  but	
  generally	
  

shows	
  high	
  site	
  fidelity	
  to	
  breeding	
  areas (Greenberg	
  and	
  

Tanner	
  2005).	
  Although	
  capable	
  of	
  long	
  distance

dispersal, its	
  infrequency	
  may	
  not	
  incur	
  resiliency	
  and	
  is	
  

similar	
  to	
  limitations	
  incurred	
  by	
  sex-­‐biased	
  dispersal.

0

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

No	
  additional	
  habitats	
  required.

0
USDA Forest Service RMRS-GTR-284. 2012. 29

Physiology:	
  Couch’s	
  spadefoot	
  (Scaphiopus	
  couchii)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Fairly	
  tolerant	
  of	
  extreme	
  temperatures	
  and	
  limited	
  rains.	
  

Nocturnal	
  behavior	
  may	
  also	
  buffer	
  individuals	
  from	
  

hottest	
  temperatures. Tolerates	
  temperatures	
  between	
  15

°C	
  and	
  34 °C (Wasserman	
  1970).	
  Adults	
  able	
  to	
  survive	
  

during	
  high	
  temperatures	
  and	
  dry	
  conditions (Moore	
  

1937).	
  Negative	
  impacts	
  are	
  expected	
  from	
  desiccation	
  of	
  

ponds	
  before	
  metamorphosis	
  is	
  complete	
  and	
  reduced	
  

longevity	
  in	
  larvae	
  that	
  develop	
  quickly (Tinsley	
  and	
  

Tocque	
  1996).	
  Ephemeral	
  ponds	
  are	
  needed	
  for	
  breeding	
  

and	
  are	
  vulnerable	
  to	
  very	
  hot/dry	
  conditions	
  that	
  cause	
  

them	
  to	
  evaporate	
  before	
  metamorphosis	
  (2-­‐6	
  weeks)	
  

resulting	
  in	
  complete	
  mortality	
  of	
  tadpoles (Tinsley	
  and	
  

Tocque	
  1996). Although	
  they	
  possess	
  specialized	
  

adaptations,	
  adults	
  are	
  prone	
  to	
  desiccation	
  under	
  

extreme	
  conditions	
  and	
  tadpoles	
  are	
  prone	
  to	
  desiccation	
  

before	
  completing	
  metamorphosis.	
  Vulnerability	
  to	
  

desiccation	
  is	
  expected	
  to	
  increase.

1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  determined	
  

by	
  temperature?	
  

No. 0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  events	
  

(e.g.,	
  severe	
  storms,	
  

fires,	
  floods)	
  that	
  affect	
  

survival	
  or	
  

reproduction	
  expected	
  

to	
  change?	
  

Nocturnal	
  when	
  active	
  and	
  hibernates	
  much	
  of	
  the	
  year	
  

underground	
  in	
  a	
  burrow.	
  Seasonal	
  torpor	
  used,	
  but	
  

hibernacula	
  are	
  buffered	
  from	
  ambient	
  temperatures.	
  

Likely	
  escapes	
  mortality	
  from	
  fire	
  in	
  underground	
  

retreats.	
  No	
  disturbances	
  known	
  that	
  result	
  in	
  mortality.

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Surface	
  activity	
  for	
  movements	
  and	
  foraging	
  restricted	
  

to	
  wet	
  periods	
  (Degenhardt	
  and	
  others	
  1996).	
  Decreases	
  

in	
  rain	
  will	
  likely	
  put	
  greater	
  restrictions	
  on	
  when	
  adults	
  

and	
  juveniles	
  can	
  be	
  active. 1

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

This	
  species	
  possesses	
  several	
  flexible	
  strategies.	
  

Species	
  can	
  hibernate	
  12	
  months	
  or	
  possibly	
  more

(Ruibal	
  and	
  others	
  1969).	
  Females	
  can	
  lay	
  hundreds	
  of	
  

eggs	
  after	
  rains (Degenhardt	
  and	
  others 1996).	
  There	
  

are	
  two	
  larval	
  morphs—one	
  is	
  fast	
  growing	
  and	
  

carnivorous	
  and	
  the	
  other	
  is	
  slow	
  growing	
  and	
  

omnivorous	
  (Degenhardt	
  and	
  others	
  1996).	
  It	
  is	
  thought	
  

that	
  this	
  is	
  a	
  strategy	
  to	
  cope	
  with	
  differences	
  in	
  pond	
  

longevity	
  and	
  food	
  availability.	
  Ephemeral	
  pond	
  

conditions	
  favor	
  carnivorous	
  larvae (Phennig	
  1992).

More	
  efficient	
  in	
  accumulating	
  food	
  reserves	
  than	
  New	
  

Mexico	
  spadefoot	
  (S.	
  multiplicata)	
  and	
  needs	
  only	
  

approximately	
  2	
  days	
  to	
  accumulate	
  reserves	
  to	
  

aestivate	
  for	
  12	
  months (Dimmitt	
  and	
  Ruibal	
  1980b).

-­1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic. -­1
30 USDA Forest Service RMRS-GTR-284. 2012.

Phenology:	
  Couch’s	
  spadefoot	
  (Scaphiopus	
  couchii)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Adults	
  may	
  move	
  toward	
  the	
  soil	
  surface	
  in	
  spring	
  in	
  

anticipation	
  of	
  rains (Ruibal	
  and	
  others	
  1969).	
  Emergence	
  

triggered	
  by	
  low	
  frequency	
  vibrations	
  associated	
  with	
  

heavy	
  rain	
  and	
  thunder	
  rather	
  than	
  soil	
  moisture

(Dimmett	
  and	
  Ruibal	
  1980a).	
  Uses	
  rainfall	
  as	
  a	
  cue,	
  and	
  

changes	
  in	
  rainfall	
  patterns	
  are	
  expected.

1

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Rainfall	
  patterns	
  will	
  likely	
  be	
  altered	
  and	
  rainfall	
  is	
  

required	
  for	
  breeding	
  and	
  foraging.

1

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Cues	
  (rainfall/vibrations)	
  are	
  directly	
  related	
  to	
  resource	
  

availability	
  (ponds	
  and	
  termites).	
  

-­1

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  breeding	
  event	
  per	
  year.	
  

1

Biotic	
  Interactions:	
  Couch’s	
  spadefoot	
  (Scaphiopus	
  couchii)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Opportunistic	
  feeding	
  on	
  small	
  invertebrates	
  including	
  

termites,	
  ants,	
  and	
  crickets.	
  Termites	
  were	
  a	
  large	
  

percentage	
  of	
  the	
  diet	
  for	
  this	
  species	
  in	
  Arizona	
  and	
  also	
  

emerge	
  during	
  summer	
  rains (Dimmitt	
  and	
  Ruibal	
  

1980b).	
  Reduced	
  rainfall	
  will	
  also	
  affect	
  emergence	
  of	
  

termites.	
  Larvae	
  are	
  omnivorous	
  and	
  feed	
  on	
  detritus	
  and	
  

microorganisms (Bragg	
  1964).	
  

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Larvae	
  fed	
  on	
  by	
  various	
  beetles,	
  birds,	
  reptiles,	
  and	
  

mammals.	
  Adults	
  secrete	
  noxious	
  compounds	
  from	
  the	
  

skin (Degenhardt	
  and	
  others	
  1996).	
  No	
  likely	
  alterations	
  

to	
  overall	
  predation	
  rates	
  with	
  changing	
  climate.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.

0
USDA Forest Service RMRS-GTR-284. 2012. 31

Biotic	
  Interactions:	
  Couch’s	
  spadefoot	
  (Scaphiopus	
  couchii)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

No	
  known	
  diseases	
  that	
  result	
  in	
  widespread	
  mortality.	
  

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

May	
  compete	
  with	
  various	
  other	
  temporary	
  pond	
  

breeders,	
  but	
  it	
  is	
  thought	
  that	
  community	
  structure	
  is	
  

determined	
  by	
  competitive	
  interactions	
  that	
  are	
  primarily	
  

within	
  species (Dayton	
  and	
  Fitzgerald	
  2001).

0
32 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s comprehensive wildlife conservation strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, Arizona.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257. 

Bragg, A. N. 1964. Further study of predation and cannibalism in spadefoot tadpoles. Herpetologica 20:17-24.

Dayton, G. H. and L. A. Fitzgerald. 2001. Competition, predation, and the distribution of four desert anurans. 

Oecologia 129:430-435.

Degenhardt, W. G., C. W. Painter, and A. H. Price. 1996. Amphibians and Reptiles of New Mexico. University of 

New Mexico Press, Albuquerque, NM. 431 p.

Dimmitt, M. A. and R. Ruibal. 1980a. Environmental correlates of emergence in spadefoot toads (Scaphiopus). 

Journal of Herpetology 14:21-29.

Dimmitt, M. A. and R. Ruibal. 1980b. Exploitation of food resources by spadefoot toads (Scaphiopus). Copeia 

1980:854-862.

Dukes J. S. and H.A. Mooney. 1999. Does global change increase the success of biological invaders? Trends in 

Ecology and Evolution 14:135-139.

Esser, Gerd. 1992. Implications of climate change for production and decomposition in grasslands and 

coniferous forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Greenberg, C. and G. Tanner. 2005. Spatial and temporal ecology of eastern spadefoot toads on a Florida 

landscape. Herpetologica 61:20-28.

Hall, J. A., P. Comer, A. Gondor, R. Marshall, and S. Weinstein. 2001. Conservation Elements of and a 

Biodiversity Management Framework for the Barry M. Goldwater Range, Arizona. The Nature Conservancy 

of Arizona, Tucson.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: Mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Moore, G. A. 1937. The spadefoot toad under drought conditions. Copeia 4:225-226.

NatureServe. 2009. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. 

NatureServe, Arlington, Virginia. Online at: http://www.natureserve.org/explorer. (Accessed: November 18, 

2009)

Phennig, D. W. 1992. Polyphenism in spadefoot toad tadpoles as a logically adjusted evolutionarily stable 

strategy. Evolution 46:1408-1420.

Ruibal, R., L. Tevis, Jr., and V. Roig. 1969. The terrestrial ecology of the spadefoot toad Scaphiopus hammondii. 

Copeia 3:571-584.

Seager, R. T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Tinsley, R. C. and K. Tocque. 1996. The population dynamics of a desert anuran, Scaphiopus couchii. Austral 

Ecology 20:376-384.

Wasserman, A. O. 1970. Scaphiopus couchii baird. Catalogue of American Amphibians and Reptiles 85.1-85.4.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 

11:2065-2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140. 
USDA Forest Service RMRS-GTR-284. 2012. 33

Morafkai’s Desert Tortoise

(Gopherus morafkai) 

SUMMARY

Desert tortoise possesses a number of adaptations to survive in the hot and dry conditions that will likely 

increase with climate change. Overall, the species is expected to experience an increase in vulnerability with 

climate change and aspects of its biology related to phenology, primarily timing of rainfall, were identified as 

particularly vulnerable to detrimental changes. Although some physiological traits will likely help it cope with 

fluctuating resources, temperature-dependent sex ratios are vulnerable to changes from increasing temperatures. Thus, ultimate changes in populations will be partly dependent on the relative influence of physiological versus phenological traits. Adult tortoises are well adapted to survive resource fluctuations making them 

resilient to climate change, but the young are more vulnerable and reproduction is likely to be reduced, resulting in population changes that could take decades to be evident. Management related to succulents, fire, and 

water sources will be important.

VULNERABILITY Score Uncertainty

Habitat 2.1 0%

Physiology 0.5 17%

Phenology 3.8 25%

Interactions 1.0 40%

Overall 7.0 18%

Introduction

This species, found in Arizona and Sinaloa and Sonora, Mexico, was recently identified as distinct from those 

populations found west of the Colorado River (Gopherus agassizii) (Murphy and others 2011). This confirms 

previous genetic evidence of evolutionarily separate species (Lamb and Lydeard 1994). The USFWS listed the 

Beaver Dam Slope population of desert tortoise in Utah as threatened in 1980 (USFWS 2008). Populations 

in California, Nevada, Utah, and northern Arizona (i.e., Mojave) were listed as Federally threatened in 1990. 

Sonoran populations are also considered threatened outside their normal range based on similarity of 

appearance. USFWS confirmed there is evidence that the Sonoran population is distinct and may warrant 

Federal listing (Federal Register, 28 August 2009, Volume 74, Number 166) but to date has not ruled on these 

populations or populations of the new species, which is not entirely restricted to the Sonoran Desert. Critical 

habitat and recovery plans were only available for the Mojave population (i.e., Agassizi’s desert tortoise) 

at the time of this report. Monitoring data is limited for Sonoran populations, compromising estimation of 

population trends for Morafkai’s desert tortoise. 

BMGR-East Climate Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

-5 0 5
34 USDA Forest Service RMRS-GTR-284. 2012.

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Summer monsoon changes unknown (Mitchell and others 2002)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

• CAM plants (succulents and cacti) will be resilient to increasing temperatures

• A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text

• Other Threats and Interactions with Climate

Numerous threats have been identified previously, including loss and degradation of habitat, collection for the 

pet trade, disease, predation, and increased drought associated with climate change (USFWS 2008). Increases 

in ravens in urban areas may increase predation of hatchling tortoises in surrounding natural habitats (Kristan 

and Boarman 2001). Release of pet tortoises into the wild may also spread disease (USFWS 2008). Off-road 

vehicle use threatens burrows and can also result in the crushing of individuals. Competition with livestock 

and other herbivores for food is a concern. Environmental toxins have been suggested to play a role in disease 

susceptibility (Boarman 2002). None of these is likely to interact with changes in climate except indirectly 

through socioeconomic changes that affect regional demographics.

The spread of non-native grasses increases fire frequency and may reduce native plants and habitat quality. 

Increases in fire and temperatures are predicted to occur with climate change, exacerbating this problem. 

Development of lands for alternative energy production is likely and may affect tortoise habitats adjacent to 

BMGR. Wind development may be compatible with desert tortoise habitat (Lovich and Daniels 2000), but 

there are concerns about habitat loss from solar developments (USFWS 2008). 

Research Needs

Research on Sonoran populations of desert tortoise was assumed to be on Morafkai’s desert tortoise. USFWS 

(2008) identified a number of areas for further research on desert tortoises, including characterization of 

stable age distributions for increasing populations, determination of factors that influence the distribution 

of desert tortoises, habitat restoration, improvements for population and mitigation models, desert tortoise 

diseases and their effects, and resolving population structure of the desert tortoise across its range. 

In relation to climate change, research on distribution and habitat use relative to projected vegetation 

changes will be particularly important. This type of analysis could also include detailed projections related to 

soil surface temperature and moisture and breeding distribution to evaluate the potential for issues related 

to temperature-dependent sex ratios and hatching success. Although tortoises can survive long periods 

without water, its availability during critical periods may help mitigate detrimental effects of summer drought. 

Research related to the potential for water developments or other habitat modifications to improve tortoise 

habitats would be valuable. Research is also lacking on the interaction of tortoise diseases and climate 

variables as well as frequency of disease mortality in populations outside the Mojave Desert, California.

Management Implications

Detrimental effects of climate change were projected to have a greater impact on young tortoises than adults, 

thus changes in adult populations would not be expected for many years and reproductive success should be 

consider as part of any monitoring program. Thermal environment is key, thus management that maintains 

vegetative cover and reduces soil compaction that prevents burrowing is important (Zimmerman 1994). In 

addition, management that maintains the thermal environment will become more critical as temperatures 
USDA Forest Service RMRS-GTR-284. 2012. 35

increase and rainfall levels become more variable. In creating protected areas for desert tortoise, the thermal 

aspects of these areas, such as slope or shade, should be considered to ensure the continued benefits of these 

locations as temperatures rise. Management related to enhancement of temporary rainfall catchment may 

also be beneficial. 

Major vulnerabilities for this species involved timing because important reproductive variables such as 

breeding and incubation times as well as sex ratio are temperature and/or rainfall related. Thus, timing of 

important activities will likely be altered in this species, but the outcome of such changes is unknown. The 

outcome will depend on complex interactions, microhabitats occupied, annual variability, and how closely 

timing in tortoise activities adjusts with timing in vegetation growth or other important events. For this 

assessment, we assumed timing changes increased the likelihood of detrimental impacts relative to current 

conditions, but we recognize that tortoises may prove resilient to some degree. Management that includes a 

large range and various microhabitats will likely enhance resilience to timing issues.

Although not currently a major threat at BMGR, fire and its interaction with introduced plants can significantly 

alter vegetation and may be an emerging issue that warrants monitoring. Succulents are prone to fire 

mortality, and fires are expected to increase with climate change and invasive plants, some of which increase 

fire occurrence, may be well adapted to changing climate conditions (Dukes and Mooney 1999). At the same 

time, invasive grasses and forbs appear to provide suitable forage for desert tortoises, thus increases in 

invasives may be beneficial to some extent although the concentration of these plants along roadsides adds 

to tortoise mortality risk. BMGR already actively controls some invasive plants, such as tumbleweeds, and fire 

risk should be evaluated for critical tortoise habitats such as those dominated by palo verde and cacti or that 

have favorable thermal conditions. 
36 USDA Forest Service RMRS-GTR-284. 2012.

HABITAT:	
  Morafkai’s	
  desert	
  tortoise	
  (Gopherus	
  morafkai)

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?

Use	
  a	
  variety	
  of	
  desert	
  vegetation	
  types,	
  including	
  scrub	
  

communities	
  associated	
  with	
  cacti	
  and	
  palo	
  verde.	
  

Southwestern	
  Arizona	
  is	
  near	
  the	
  center	
  of	
  the	
  range	
  for	
  

desert	
  tortoise,	
  which	
  extends	
  from	
  Utah	
  into	
  Mexico.	
  

Vegetation	
  associations	
  include	
  creosote	
  bush,	
  palo	
  

verde-­‐mixed	
  cacti,	
  and	
  saguaro-­‐ocotillo	
  cacti	
  associations.	
  

Native	
  plants	
  of	
  these	
  vegetation	
  types	
  are	
  not	
  likely	
  to	
  be	
  

reduced	
  by	
  increasing	
  temperatures	
  (up	
  to	
  year	
  2050).	
  

Increased	
  fire	
  occurrence	
  is	
  projected	
  but	
  will	
  depend	
  on	
  

ground	
  cover.	
  Sonoran	
  desert	
  habitats	
  may	
  expand	
  to	
  the	
  

north,	
  but	
  these	
  regions	
  will	
  be	
  more	
  prone	
  to	
  increased	
  

fire	
  frequency	
  because	
  of	
  higher	
  rainfall	
  levels	
  and	
  

already	
  high	
  levels	
  of	
  invasive	
  grasses.

0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?

Suitable	
  burrows	
  and	
  soils	
  are	
  required	
  for	
  breeding.	
  Not	
  

expected	
  to	
  change.

0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?

Required	
  habitat	
  elements	
  include	
  periodic	
  water	
  sources	
  

and	
  suitable	
  locations	
  for	
  burrows.	
  Temporary	
  pools	
  

created	
  by	
  rainfall	
  appear	
  to	
  be	
  important,	
  particularly	
  

during	
  the	
  summer	
  months,	
  for	
  growth	
  and	
  survival	
  

(Nagy	
  and	
  others	
  1998).	
  In	
  the	
  San	
  Pedro	
  Valley,	
  Arizona,	
  

desert	
  tortoises	
  hibernated	
  in	
  burrows	
  excavated	
  in	
  

friable	
  soils	
  on	
  steep,	
  south-­‐facing	
  slopes,	
  probably	
  for	
  

thermal	
  advantage	
  (Bailey	
  and	
  others	
  1995).	
  Generally	
  

dig	
  deep	
  burrows,	
  but	
  some	
  Sonoran	
  tortoises	
  aestivate	
  

in	
  rock	
  crevices	
  or	
  under	
  boulders	
  (De	
  Vos	
  and	
  others

1983;	
  NatureServe	
  2009).

Need	
  suitable	
  areas	
  for	
  burrows	
  (washes,	
  crevices,	
  and	
  

friable	
  soils).	
  Burrows	
  are	
  not	
  likely	
  to	
  be	
  affected	
  by	
  

climate,	
  but	
  periodic	
  water	
  sources	
  will	
  be	
  reduced	
  with	
  

warmer	
  temperatures	
  and	
  more	
  variable	
  rainfall.

1

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Greater	
  spring	
  annual	
  production	
  may	
  be	
  associated	
  with	
  

a	
  greater	
  proportion	
  of	
  females	
  breeding	
  and	
  greater	
  

reproductive	
  success.	
  Winter	
  precipitation,	
  which	
  

correlates	
  with	
  spring	
  annual	
  production,	
  is	
  expected	
  to	
  

remain	
  similar	
  to	
  current	
  levels,	
  but	
  greater	
  variability	
  is	
  

anticipated	
  along	
  with	
  greater	
  evaporation.	
  Projections	
  

for	
  summer	
  precipitation	
  are	
  more	
  uncertain.	
  Greater	
  

vegetative	
  cover,	
  particularly	
  shrubs,	
  may	
  increase	
  

survival	
  through	
  improving	
  the	
  thermal	
  environment.	
  

Increasing	
  fires	
  will	
  likely	
  reduce	
  native	
  desert	
  shrubs	
  in	
  

some	
  areas	
  and	
  many	
  shrubs	
  are	
  drought	
  deciduous.

1
USDA Forest Service RMRS-GTR-284. 2012. 37

HABITAT:	
  Morafkai’s	
  desert	
  tortoise	
  (Gopherus	
  morafkai)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Desert	
  tortoises	
  are	
  not	
  territorial	
  and	
  generally	
  occupy	
  

home	
  ranges	
  of	
  fewer	
  than	
  50	
  ha,	
  though	
  individuals	
  may	
  

move	
  several	
  kilometers	
  (NatureServe	
  2009).	
  Males	
  may	
  

also	
  have	
  larger	
  home	
  ranges	
  than	
  females.	
  Can	
  move	
  

several	
  kilometers,	
  but	
  movements	
  are	
  generally	
  limited

and	
  are	
  often	
  blocked	
  by	
  roads	
  and	
  fences.	
  Probably	
  

limited	
  in	
  their	
  ability	
  to	
  expand	
  into	
  new	
  habitats	
  within	
  

limited	
  time	
  periods.

1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Do	
  not	
  migrate	
  through	
  or	
  require	
  transitional	
  habitats.

0

Physiology:	
  Morafkai’s	
  desert	
  tortoise	
  (Gopherus	
  morafkai)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Adults	
  are	
  effective	
  at	
  retaining	
  water	
  and	
  store	
  it	
  in	
  the	
  

bladder	
  for	
  up	
  to	
  a	
  year	
  (Peterson	
  1996;	
  Henen	
  and	
  

others	
  1998).	
  Adults	
  are	
  capable	
  of	
  withstanding	
  large	
  

imbalances	
  in	
  electrolytes	
  and	
  water	
  (Henen	
  1997).	
  In	
  

addition,	
  they	
  can	
  switch	
  from	
  producing	
  urea	
  to	
  more	
  

water-­‐conserving	
  uric	
  acid	
  (NatureServe	
  2009).	
  Young	
  

tortoises	
  are	
  more	
  prone	
  to	
  dehydration	
  and	
  starvation	
  

than	
  larger	
  adults	
  (NatureServe	
  2009).	
  Eggs	
  are	
  laid	
  in	
  

shallow	
  depressions	
  generally	
  near	
  the	
  entrance	
  of	
  the	
  

burrow.	
  For	
  Mojave	
  tortoises,	
  incubation	
  temperatures	
  

need	
  to	
  be	
  between	
  26 °C	
  and	
  33 °C	
  but	
  could	
  be	
  

successful	
  at	
  up	
  to	
  35 °C.	
  Soil	
  moisture	
  above	
  4%	
  can	
  

compromise	
  hatching	
  (Spotila	
  and	
  others	
  1994).	
  Lower	
  

survival	
  rates	
  in	
  the	
  Mojave	
  Desert were	
  associated	
  with	
  

droughts	
  (Longshore	
  and	
  others	
  2003).	
  Distribution	
  is	
  

thought	
  to	
  be	
  limited	
  by	
  aridity	
  in	
  the	
  lower	
  Colorado	
  

River	
  Valley	
  (Van	
  Devender	
  2002)	
  and	
  by	
  wet	
  climates	
  in	
  

the	
  tropics	
  that	
  promote	
  fungus	
  pathogens	
  (Bury	
  and	
  

others	
  2002).	
  Droughts,	
  which	
  are	
  expected	
  to	
  increase,	
  

are	
  associated	
  with	
  higher	
  mortality,	
  particularly	
  for	
  

juveniles.	
  

1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

Tortoises	
  have	
  temperature-­‐determined	
  sex	
  ratios,	
  with	
  

males	
  hatching	
  at	
  lower	
  temperatures	
  and	
  females	
  at	
  

higher	
  temperatures.	
  In	
  Nevada,	
  the	
  pivotal	
  temperature	
  

for	
  determining	
  sex	
  was	
  found	
  to	
  be	
  31.8 °C	
  (Spotila	
  and	
  

others	
  1994).

1

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Hibernacula	
  of	
  females	
  were	
  in	
  shorter	
  burrows	
  than	
  

males	
  and	
  thus	
  subject	
  to	
  greater	
  temperature	
  

fluctuations	
  (Bailey	
  and	
  others	
  1995).	
  Male	
  hibernacula	
  

may	
  be	
  more	
  buffered	
  from	
  extreme	
  conditions	
  than	
  

female	
  hibernacula.	
  Burrow	
  excavation	
  behaviors	
  may	
  be	
  

flexible	
  and	
  individuals	
  probably	
  can	
  adjust	
  burrow	
  

dimensions	
  to	
  adequately	
  buffer	
  from	
  ambient	
  

temperatures.	
  Slow	
  moving,	
  thus	
  may	
  be	
  prone	
  to	
  direct	
  

0
38 USDA Forest Service RMRS-GTR-284. 2012.

Physiology:	
  Morafkai’s	
  desert	
  tortoise	
  (Gopherus	
  morafkai)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

mortality	
  during	
  fires,	
  but	
  fire	
  risk	
  in	
  these	
  habitats	
  is	
  

generally	
  not	
  high.	
  No	
  known	
  mortality	
  associated	
  with	
  

flooding	
  or	
  fires.

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Spend	
  much	
  of	
  the	
  year	
  inactive	
  although	
  activity	
  is	
  

strongly	
  associated	
  with	
  temperature.	
  Active	
  periods	
  and	
  

movements	
  were	
  reduced	
  during	
  a	
  drought	
  year	
  as	
  

compared	
  to	
  a	
  wet	
  year	
  in	
  the	
  Mojave Desert,	
  which	
  may	
  

be	
  an	
  adaptation	
  to	
  save	
  energy	
  when	
  resources	
  are	
  

limited	
  (Duda	
  1999).	
  Desert	
  tortoises	
  also	
  tended	
  to	
  be	
  

inactive	
  during	
  hot	
  temperatures	
  such	
  as	
  mid-­‐day	
  in	
  

summer	
  and	
  more	
  active	
  following	
  summer	
  rains	
  

(Zimmerman	
  1994;	
  Duda	
  1999).	
  Activity	
  patterns	
  and	
  

burrow	
  use	
  are	
  sensitive	
  to	
  surface	
  temperatures	
  

(Zimmerman	
  1994).	
  During	
  summer,	
  tortoises	
  generally	
  

sleep	
  under	
  bushes	
  at	
  night	
  and	
  activities	
  are	
  still	
  

primarily	
  diurnal,	
  although	
  more	
  limited	
  during	
  hot	
  

temperatures	
  (Zimmerman	
  1994).	
  Activity	
  periods	
  likely	
  

reduced	
  with	
  higher	
  temperatures	
  and	
  greater	
  

evaporation.

1

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Desert	
  tortoises	
  can	
  store	
  water	
  in	
  the	
  bladder	
  and	
  switch	
  

between	
  production	
  of	
  urea	
  and	
  uric	
  acid.	
  Females	
  can	
  

also	
  store	
  sperm	
  and	
  sperm	
  can	
  be	
  stored	
  from	
  the	
  

previous	
  year	
  (Rostal	
  and	
  others	
  1994).	
  Agassizi’s	
  desert	
  

tortoises	
  have	
  also	
  been	
  known	
  to	
  construct	
  rainwater	
  

catchments	
  (Medica	
  and	
  others	
  1980).	
  These	
  strategies	
  

may	
  be	
  helpful	
  as	
  resources	
  and	
  populations	
  fluctuate	
  

across	
  years.

-­1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Desert	
  tortoises	
  have	
  low	
  metabolic	
  rates	
  as	
  compared	
  to	
  

other	
  reptiles	
  and	
  can	
  tolerate	
  long	
  drought	
  periods	
  

(Peterson	
  1996).

-­1

Phenology:	
  Morafkai’s	
  desert	
  tortoise	
  (Gopherus	
  morafkai)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Temperature	
  and	
  moisture	
  related	
  to	
  emergence	
  from	
  

hibernacula,	
  after	
  which	
  mating	
  and	
  egg laying	
  occur.	
  

Emergence	
  from	
  hibernacula	
  varies	
  with	
  temperature	
  and	
  

rainfall,	
  and	
  individuals	
  may	
  emerge	
  opportunistically	
  

(NatureServe	
  2009).	
  Desert	
  tortoises	
  hibernate	
  in	
  winter	
  

and	
  may	
  also	
  aestivate	
  during	
  hot	
  summer	
  temperatures.	
  

Tortoises	
  will	
  emerge	
  periodically	
  from	
  burrows	
  during	
  

winter	
  to	
  bask	
  or	
  move	
  between	
  burrows	
  (Averill-­‐Murray	
  

2000).

1

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Rainfall	
  is	
  important	
  to	
  digestion	
  and	
  growth.	
  Quantity	
  

and	
  timing	
  of	
  rainfall	
  was	
  found	
  to	
  be	
  an	
  important	
  

interaction	
  responsible	
  for	
  variation.	
  Timing	
  and	
  quantity	
  

of	
  rainfall	
  will	
  likely	
  be	
  altered	
  with	
  climate	
  change.	
  

Incubation	
  time	
  varies	
  with	
  temperature.	
  Differences	
  in	
  

female	
  hibernacula	
  may	
  influence	
  individual	
  timing	
  of	
  

emergence	
  (Bailey	
  and	
  others	
  1995).

1
USDA Forest Service RMRS-GTR-284. 2012. 39

Phenology:	
  Morafkai’s	
  desert	
  tortoise	
  (Gopherus	
  morafkai)

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	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Spermatogenesis	
  and	
  mating	
  occurs	
  in	
  the	
  fall.	
  Mating	
  

also	
  occurs	
  in	
  spring,	
  after	
  emergence	
  from	
  hibernation,	
  

from	
  March	
  to	
  April	
  (Rostal	
  and	
  others	
  1994).	
  Eggs	
  

incubate	
  >85	
  days	
  following	
  fertilization	
  and	
  egg	
  laying	
  in	
  

the	
  spring.	
  Because	
  hibernation	
  emergence	
  is	
  likely	
  cued	
  

by	
  temperature,	
  it	
  is	
  not	
  distant	
  from	
  conditions	
  that	
  will	
  

affect	
  resources.

0

4.	
  Resilience	
  

to	
  timing

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Egg	
  laying	
  occurs	
  from	
  May	
  to	
  early	
  July,	
  and	
  in	
  some	
  

regions,	
  females	
  can	
  have	
  a	
  second	
  clutch,	
  although	
  

Sonoran	
  populations	
  seem	
  to	
  have	
  a	
  single	
  clutch	
  per	
  year	
  

(NatureServe	
  2009).	
  Proportion	
  of	
  females	
  reproducing	
  in	
  

a	
  given	
  year	
  appears	
  to	
  be	
  related	
  to	
  winter	
  and	
  spring	
  

rainfall	
  (Averill-­‐Murray	
  2000).	
  Breed	
  once	
  per	
  year	
  (or	
  

less)	
  in	
  the	
  spring.

1

Biotic	
  Interactions:	
  Morafkai’s	
  desert	
  tortoise	
  (Gopherus	
  morafkai)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Eat	
  a	
  variety	
  of	
  plant	
  species.	
  Herbaceous	
  growth	
  will	
  

fluctuate	
  with	
  rainfall	
  and	
  likely	
  become	
  more	
  variable.	
  

Grasses	
  may	
  increase	
  with	
  higher	
  temperatures	
  and	
  

increased	
  fires,	
  but	
  forbs	
  are	
  higher	
  quality	
  forage	
  than	
  

grasses.	
  Although	
  there	
  will	
  be	
  some	
  years	
  of	
  high	
  

herbaceous	
  growth,	
  increasing	
  droughts	
  and	
  higher	
  

temperatures	
  will	
  likely	
  reduce	
  vegetation	
  available	
  in	
  

many	
  years.	
  Desert	
  tortoises	
  feed	
  primarily	
  on	
  vegetation	
  

but	
  also	
  some	
  insects	
  (NatureServe	
  2009).	
  Annual	
  grasses	
  

eaten	
  include	
  non-­‐native	
  species	
  such	
  as	
  red	
  brome	
  

(Bromus	
  rubens).	
  Forbs,	
  both	
  native	
  and	
  non-­‐native,	
  were	
  

processed	
  more	
  efficiently,	
  required	
  less	
  water	
  to	
  digest,	
  

and	
  contained	
  more	
  nitrogen	
  than	
  grasses	
  (Nagy	
  and	
  

others	
  1998).	
  Dry	
  forage	
  along	
  with	
  consumption	
  of	
  rain	
  

water	
  is	
  important	
  to	
  building	
  energy	
  stores	
  (Peterson	
  

1996).	
  

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Predation	
  at	
  nests	
  may	
  be	
  high	
  (Germano	
  1994).	
  A	
  large	
  

range	
  of	
  predators	
  eat	
  hatchlings	
  and	
  juveniles	
  (USFWS	
  

2008).	
  Increased	
  urban	
  development	
  has	
  been	
  implicated	
  

in	
  increasing	
  ravens	
  and	
  thus	
  tortoise	
  predation	
  (Kristan	
  

and	
  Boarman	
  2001),	
  but	
  this	
  interaction	
  may	
  not	
  be	
  

present	
  in	
  Sonoran	
  populations	
  (Averill-­‐Murray	
  2000).	
  

Predation	
  of	
  eggs	
  is	
  fairly	
  high	
  but	
  opportunistic	
  by	
  a	
  

wide	
  variety	
  of	
  predators.	
  No	
  current	
  urban	
  development	
  

near	
  BMGR-­‐East	
  that	
  is	
  likely	
  to	
  significantly	
  increase	
  

raven	
  populations	
  on	
  DoD	
  lands	
  in	
  the	
  near	
  future.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.	
  Winter	
  burrows	
  may	
  be	
  used	
  communally,	
  

but	
  not	
  known	
  how	
  common	
  this	
  behavior	
  is,	
  although	
  it	
  

is	
  assumed	
  it	
  decreases	
  energy	
  needed	
  for	
  

thermoregulation.

0
40 USDA Forest Service RMRS-GTR-284. 2012.

Biotic	
  Interactions:	
  Morafkai’s	
  desert	
  tortoise	
  (Gopherus	
  morafkai)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

At	
  least	
  two	
  diseases	
  have	
  been	
  implicated	
  in	
  widespread	
  

mortality:	
  upper	
  respiratory	
  tract	
  disease	
  caused	
  by	
  

mycoplasma	
  (Jacobson	
  and	
  others	
  1991)	
  and	
  cutaneous	
  

dyskeratosis	
  or	
  shell	
  disease	
  (Jacobson	
  and	
  others	
  1994).	
  

Most	
  disease-­‐related	
  declines	
  have	
  been	
  documented	
  for	
  

Mojave	
  populations	
  and	
  there	
  have	
  been	
  no	
  recent	
  

declines	
  attributed	
  to	
  disease	
  in	
  Sonoran	
  populations	
  

(Averill-­‐Murray	
  2000).	
  The	
  majority	
  of	
  Sonoran	
  tortoises	
  

from	
  one	
  study,	
  however,	
  were	
  recorded	
  as	
  having	
  shell	
  

disease,	
  though	
  it	
  was	
  not	
  implicated	
  in	
  mortality	
  (Averill-­‐

Murray	
  2000).	
  Transmission	
  may	
  be	
  increased	
  by	
  release	
  

of	
  captive-­‐reared	
  or	
  pet	
  tortoises,	
  or	
  possibly	
  ravens.	
  

Disease	
  susceptibility	
  has	
  also	
  been	
  linked	
  to	
  toxins	
  such	
  

as	
  arsenic.	
  Susceptible	
  to	
  disease,	
  though	
  most	
  mortality	
  

has	
  been	
  documented	
  in	
  Mojave	
  populations.	
  No	
  known	
  

relationship	
  between	
  virulence	
  or	
  transmission	
  of	
  these	
  

diseases	
  and	
  climate.

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Competition	
  for	
  forage	
  is	
  thought	
  to	
  occur	
  with	
  livestock	
  

and	
  other	
  herbivores	
  (USFWS	
  2008).BMGR	
  does	
  not	
  have	
  

livestock	
  grazing.	
  Changes	
  in	
  climate	
  would	
  be	
  most	
  likely	
  

to	
  decrease	
  competing	
  native	
  grazers,	
  but	
  populations	
  of	
  

potential	
  competitive	
  species	
  are	
  low.

0
USDA Forest Service RMRS-GTR-284. 2012. 41

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s comprehensive wildlife conservation strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, Arizona.

Averill-Murray, R.C., and C.M. Klug. 2000. Monitoring and ecology of Sonoran desert tortoises in Arizona. 

Nongame and Endangered Wildlife Program Technical Report 161. Arizona Game and Fish Department, 

Phoenix, Arizona.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257. 

Bailey, S. J., C. R. Schwalbe, and C. H. Lowe. 1995. Hibernaculum Use by a Population of Desert Tortoises 

(Gopherus agassizii) in the Sonoran Desert. Journal of Herpetology 29:361-369.

Boarman, W. I. 2002. Threats to desert tortoise populations: a critical review of the literature. U.S. Geological 

Survey, Western Ecological Research Center, Sacramento, California.

Bury, R. B., D. J. Germano, T. R. Van Devender, and B. E. Martin. 2002. Chapter 5: the Desert Tortoise in 

Mexico. Pages 86-108 In T. R. Van Devender, ed., The Sonoran Desert Tortoise: Natural History, Biology, and 

Conservation.

Cox, J. R. and G. B. Ruhle. 1986. Influence of climatic and edaphic factors on the distribution of Eragrostis 

lehmanniana nees in Arizona, USA. African Journal of Range and Forage Science: 3.

Duda, J. J., A. J. Krzysik, and J. E. Freilich. 1999. Effects of drought on desert tortoise movement and activity. 

The Journal of Wildlife Management 63:1181-1192.

Dukes, J. S. and H. A. Mooney. 1999. Does global change increase the success of biological invaders? Trends in 

Ecology and Evolution 14:135-139.

Ehleringer, J. R., S. L. Phillips, W. S. F. Schuster, and D. R. Sandqui. 1991. Differential utilization of summer rains 

by desert plants. Oecologia 88:430-434.

Esser, Gerd. 1992. Implications of climate change for production and decomposition in grasslands and 

coniferous forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Germano, D. J. 1994. Growth and age at maturity of North American tortoises in relation to regional climates. 

Canadian Journal of Zoology 72:918-931.

Henen, B. T. 1997. Seasonal and annual energy budgets of female desert tortoises (Gopherus agassizii). 

Ecology 78:283-296.

Henen, B. T., C. C. Peterson, I. R. Wallis, K. H. Berry, and K. A. Nagy. 1998. Effects of climatic variation on field 

metabolism and water relations of desert tortoises. Oecologia 117:365-373.

Hoffmeister, D. F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish Dept. 

602 p.

Jacobson, E. R., J. M. Gaskin, M. B. Brown, R. K. Harris, C. H. Gardiner, J. L. LaPointe, H. P. Adams, and C. 

Reggiardo. 1991. Chronic upper respiratory tract disease of free-ranging desert tortoises (Xerobates 

agassizii). Journal of Wildlife Diseases 27:296-316.

Jacobson, E. R., T. J. Wronski, J. Schumacher, C. Reggiardo, and K. H. Berry. 1994. Cutaneous dyskeratosis in 

free-ranging desert tortoises, Gopherus agassizii, in the Colorado Desert of Southern California. Journal of 

Zoo and Wildlife Medicine 25:68-81.

Kristan, W. B. and W. I. Boarman. 2003. Spatial pattern of risk of common raven predation on desert tortoises. 

Ecology 84:2432-2443.

Longshore, K. M., J. R. Jaeger, and J. M. Sappington. 2003. Desert tortoise (Gopherus agassizii) survival at two 

eastern Mojave Desert sites: death by short-term drought? Journal of Herpetology 37:169-177.
42 USDA Forest Service RMRS-GTR-284. 2012.

Lovich, J. E., and R. Daniels. 2000. Environmental characteristics of desert tortoise (Gopherus agassizii) burrow 

locations in an altered industrial landscape. Chelonian Conservation and Biology 3:714-721.

Medica, P. A., R. B. Bury, and R. A. Luckenbach. 1980. Drinking and construction of water catchments by the 

desert tortoise, Gopherus agassizii, in the Mojave Desert. Herpetologica 36:301-304.

McLaughlin, S. E. and J. P. Bowers. 1982. Effects of wildfire on a Sonoran Desert plant community. Ecology 

63:246-248.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

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. doi:10.3897/zookeys.113.1353.

Nagy, K. A., B. T. Henen, and D. B. Vyas. 1998. Nutritional quality of native and introduced food plants of wild 

desert tortoises. Journal of Herpetology 32:260-267. 

NatureServe. 2009. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. 

NatureServe, Arlington, Virginia. Online at: http://www.natureserve.org/explorer. (Accessed: November 18, 

2009)

Peterson, C. C. 1996. Ecological energetics of the desert tortoise (Gopherus agassizii): effects of rainfall and 

drought. Ecology 77:1831-1844. 

Pinkava, D. J. 1999. Cactaceae cactus family, part three Cylindropuntia. Journal of the Arizona-Nevada 

Academy of Science 32(1):32-47.

Rostal, D. C., V. A. Lance, J. S. Grumbles, and A. C. Alberts. 1994. Seasonal reproductive cycle of the desert 

tortoise (Gopherus agassizii) in the eastern Mojave Desert. Herpetological Monographs 8:72-82.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Smith, S. D., B. Didden-Zopfy, and P. S. Nobel. 1984. High-temperature responses of North American cacti. 

Ecology 65:643-651. 

Spotila, J. R., L. C. Zimmerman, C. A. Binckley,[and others]. 1994. Effects of incubation conditions on 

sex determination, hatching success, and growth of hatchling desert tortoises, Gopherus agassizii. 

Herpetological Monographs 8:103-116.

U.S. Fish and Wildlife Service (USFWS). 2008. Draft revised recovery plan for the Mojave population of 

the desert tortoise (Gopherus agassizii). U.S. Fish and Wildlife Service, California and Nevada Region, 

Sacramento, CA. 209 p.

Van Devender, T. R. 2002. Chapter 1: Natural History of the Sonoran Tortoise in Arizona. Pages 3-28 In T. R. 

Van Devender, ed., The Sonoran Desert Tortoise: Natural History, Biology, and Conservation. University of 

Arizona Press, Tucson, AZ.

Van Devender, T. R. and M. A. Dimmitt. 2006. Final report on conservation of Arizona upland Sonoran Desert 

habitat: status and threats of buffelgrass (Pennisetum ciliare) in Arizona and Sonora. Arizona-Sonora Desert 

Museum, Tucson, AZ. 

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.

Zimmerman, L. C., M. P. O’Connor, S. J. Bulova, J. R. Spotila, S. J. Kemp, and C. J. Salice. 1994. Thermal ecology 

of desert tortoises in the eastern Mojave Desert: seasonal patterns of operative and body temperatures, 

and microhabitat utilization. Herpetological Monographs 8:45-59.
USDA Forest Service RMRS-GTR-284. 2012. 43

Saddled Leaf-nosed Snake

(Phyllorhynchus browni)

SUMMARY

The saddled leaf-nosed snake may be vulnerable to climate change because of its specialized diet of snake and 

lizard eggs, although overall, the predicted increase in vulnerability for this species was limited. Phenology 

was an area of high vulnerability for this species as the timing of hibernation and breeding may shift. Vulnerability of this species will depend on how other species respond; thus, predicting future population changes is 

particularly complex and uncertainty is high.

VULNERABILITY Score Uncertainty

Habitat -0.8 29%

Physiology -1.0 50%

Phenology 3.8 25%

Interactions 1.0 60%

Overall 1.5 41%

Introduction

The saddled leaf-nosed snake was formerly thought to be a subspecies of spotted leaf-nosed snake 

(Phyllorhynchus decurtatus). Little is known about populations and the species is listed as being of unknown 

status in the Arizona State Wildlife Action Plan (AGFD 2006). The U.S. Forest Service designates it as sensitive. 

The proposed biodiversity management framework for BMGR suggests that the saddled leaf-nosed snake will 

be vulnerable to climate change effects (Hall and others 2001).

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

-5 0 5

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0
44 USDA Forest Service RMRS-GTR-284. 2012.

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

The specialist diet of this species may increase its vulnerability to population declines with climate change 

(Hall and others 2001). Other snake and lizard species may be vulnerable to declines and, in turn, may affect 

populations of leaf-nosed snakes. Military activities that use roads at night may increase risk for this species, 

but climate is not expected to alter this impact. Vehicular use of dunes, including recreational and law 

enforcement use, could also negatively impact this species, and border patrol activities could conceivably 

increase. Buffering of climate impacts varies with factors such as irrigation and government programs, both of 

which predict that drought impacts will be less severe in the United States as compared to Mexico (VásquezLeón and others 2003). In the absence of alterations to immigration policies, increased illegal traffic at the 

international border is expected. 

Research Needs

The saddled leaf-nosed snake is a poorly understood species, so little information is available to assess its 

vulnerability and almost all aspects of its natural history need more study. Its secretive nocturnal habits add 

to problems with research and population monitoring. The restricted diet of this snake will likely increase its 

vulnerability to declines, but its ability to switch to other food sources is unknown. P. decurtatus eats small 

lizards.

Management Implications

Various nighttime military training activities, particularly those that involve vehicles, may affect this species 

through direct mortality or disturbance. Daytime vehicle use on dunes can also impact burrows or buried 

snakes. Although most human threats to this species are not expected to increase with climate change, 

border patrol activities, and thus vehicular use, may increase with climate change if drought stress increases 

illegal immigration in the region. Reducing mortality sources could help maintain populations if other threats 

increase. Travel through leaf-nosed snake habitats should be managed to reduce impacts. Protection of other 

snake and lizard species will ensure adequate food resources for this species. 
USDA Forest Service RMRS-GTR-284. 2012. 45

Habitat:	
  Saddled	
  leaf-­nosed	
  snake	
  (Phyllorhynchus	
  browni)

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	
  northern	
  part	
  of	
  its	
  range,	
  this	
  snake	
  inhabits	
  

desertscrub	
  with	
  mesquite,	
  saltbush,	
  creosote	
  bush,	
  palo

verde,	
  and	
  saguaro	
  cactus.	
  In	
  southern	
  areas,	
  it	
  

frequents	
  thornscrub	
  and	
  the	
  lower	
  edge	
  of	
  thornforest	
  

(Stebbins,	
  1985).	
  Usually	
  occurs	
  in	
  foothills	
  (Brennan	
  

and	
  Holycross	
  2006).	
  No	
  expected	
  change	
  in	
  area	
  

occupied	
  by	
  this	
  vegetation	
  type	
  on	
  BMGR.

0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Lays	
  eggs	
  underground	
  in	
  burrow.	
  No	
  expected	
  changes	
  

in	
  suitable	
  soils	
  for	
  burrowing.

0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Uses	
  burrows	
  for	
  hibernation	
  and	
  digs	
  its	
  own	
  burrow.	
  

No	
  expected	
  changes	
  in	
  suitable	
  soils	
  for	
  burrowing.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  to	
  

change?	
  

None	
  known.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Unknown	
  dispersal,	
  but	
  assumed	
  to	
  be	
  mobile	
  without	
  

major	
  barriers. -­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Not	
  migratory.

0
46 USDA Forest Service RMRS-GTR-284. 2012.

Physiology:	
  Saddled	
  leaf-­nosed	
  snake	
  (Phyllorhynchus	
  browni)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Little	
  information.	
  Range	
  is	
  Arizona	
  and	
  Mexico	
  (Brennan	
  

and	
  Holycross	
  2006).	
  Not	
  expected	
  to	
  exceed	
  critical	
  

temperatures	
  in	
  habitats	
  occupied,	
  and	
  not	
  generally	
  

exposed	
  to	
  the	
  hottest	
  temperatures.

0

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Hibernates	
  during	
  cold	
  months	
  and	
  is	
  often	
  buried	
  in	
  sand	
  

(Brennan	
  and	
  Holycross	
  2006).	
  Likely	
  to	
  escape	
  at	
  least	
  

some	
  disturbance	
  events.	
  No	
  other	
  information. 0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Wholly	
  nocturnal,	
  and	
  no	
  anticipated	
  changes	
  in	
  activity	
  

periods.

0

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

No	
  flexible	
  strategies	
  known.

0

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic. -­1

Phenology:	
  Saddled	
  leaf-­nosed	
  snake	
  (Phyllorhynchus	
  browni)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Temperature	
  is	
  likely	
  cue	
  for	
  hibernation.

1

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Limited	
  information	
  but	
  it	
  is	
  assumed	
  that	
  eggs	
  are	
  laid	
  in	
  

summer	
  (BISON-­‐M).	
  Eggs	
  are	
  thought	
  to	
  be	
  laid	
  in	
  June	
  to	
  

July	
  in	
  decurtatus.	
  Hatchlings	
  emerge	
  starting	
  in	
  July	
  

(Brennan	
  and	
  Holycross	
  2006).	
  Resource	
  peaks	
  are	
  not	
  

known,	
  although	
  may	
  time	
  breeding	
  to	
  availability	
  of	
  eggs	
  

of	
  other	
  snakes,	
  which	
  will	
  be	
  subject	
  to	
  phenological	
  

changes	
  in	
  breeding.

1

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Cues	
  not	
  expected	
  to	
  be	
  distant	
  from	
  activities	
  such	
  as	
  

breeding.

0
USDA Forest Service RMRS-GTR-284. 2012. 47

Phenology:	
  Saddled	
  leaf-­nosed	
  snake	
  (Phyllorhynchus	
  browni)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  reproductive	
  event	
  per	
  year.

1

Biotic	
  Interactions:	
  Saddled	
  leaf-­nosed	
  snake	
  (Phyllorhynchus	
  browni)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

This	
  species	
  is	
  a	
  specialist	
  that	
  mostly	
  eats	
  eggs	
  of	
  snakes	
  

and	
  lizards	
  (Stebbins	
  1985,	
  Brennan	
  and	
  Holycross	
  2006).	
  

Although	
  various	
  lizards	
  and	
  snakes	
  may	
  be	
  resilient	
  to	
  

climate	
  change,	
  reproduction	
  is	
  more	
  sensitive	
  and	
  likely	
  

reduced	
  in	
  many	
  species	
  by	
  increasing	
  droughts.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Not	
  known,	
  but	
  assumed	
  to	
  have	
  various	
  predators.	
  Not	
  

expected	
  to	
  change	
  overall. 0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

None.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

None	
  known.

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

None	
  known.

0
48 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s comprehensive wildlife conservation strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257. 

BISON-M. Biotic Information System of New Mexico. New Mexico Game and Fish Department. Online at: 

http://www.bison-m.org.

Brennan, T. C. and A. T. Holycross. 2006. A field guide to amphibians and reptiles in Arizona. Arizona Game and 

Fish Department. Phoenix, AZ.

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17. 

Hall, J. A., P. Comer, A. Gondor, R. Marshall, and S. Weinstein. 2001. Conservation Elements of and a 

Biodiversity Management Framework for the Barry M. Goldwater Range, Arizona. The Nature Conservancy 

of Arizona, Tucson.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

NatureServe. 2009. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. 

NatureServe, Arlington, Virginia. Online at: http://www.natureserve.org/explorer. (Accessed: November 18, 

2009).

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Stebbins, R. C. 1985. A Field Guide to Western Reptiles and Amphibians. Second Edition. National Audubon 

Society. Houghton Mifflin Co., Boston and New York.

Vásquez-León, M., C. T. West, and T. J. Finan. 2003. A comparative assessment of climate vulnerability: 

agriculture and ranching on both sides of the US-Mexico border. Global Environmental Change 13:159-173.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 49

Red-backed Whiptail

(Aspidoscelis xanthonota)

SUMMARY

Red-backed whiptails are expected to have some increased vulnerability to declines associated with future 

climate change. Phenology, as related to both seasonal and daily activity, is an area of vulnerability, although 

phenological relationships are not well known for this species. Management of xeroriparian habitats, particularly the prevention of invasion by non-native grasses, as well as protection of large trees and shrubs will be 

important.

VULNERABILITYY Score Uncertainty

Habitat -0.1 29%

Physiology 1.7 50%

Phenology 2.5 25%

Interactions 1.0 60%

Overall 4.4 45%

Introduction

Formerly, red-backed whiptail was a subspecies of the canyon spotted whiptail and identified as 

Cneimidophorous burti xanthonotus or Aspidoscelis burti xanthonota. It potentially occurs in xeroriparian 

scrub in the Sand Tank Mountains (Hall and others 2001). Arizona State Fish and Game identifies it as a species 

of greatest conservation need, Tier 1B, in the Arizona State Wildlife Action Plan (AGFD 2006). Furthermore, it 

was identified as potentially vulnerable to climate change effects on BMGR (Hall and others 2001). BMGR is 

the edge of the range for this species; thus, climate-related shifts in distribution will likely affect its abundance 

and occurrence locally (Hall and others 2001). 

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

-5 0 5

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0
50 USDA Forest Service RMRS-GTR-284. 2012.

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

Lizards in hot environments may be vulnerable to temperature changes associated with energetics (Sinervo 

and others 2010). Partly based on climate projections and temperature tolerances, Sinervo and others (2010) 

estimated extinction of 14% of local populations and 4% of species by 2050 for this family, Teiidae.

Although red-backed whiptail occurs in a variety of habitats, xeroriparian areas may be prone to changes 

associated with invasive grasses and fire occurrence. Projected increases in climate variability will also 

increase fire occurrence as years of high rainfall are followed by dry/hot conditions, creating conditions 

conducive both to fire ignition and fuel accumulation. Fire regimes in the region have also been altered by 

introduced plant species that provide fine fuels to carry fire. Red brome (Bromus rubens), Mediterranean 

grass (Schismus barbatus), and Sahara mustard (Brassica tournefortii) are common invasives in the region. 

Buffelgrass promotes a frequent high severity fire regime, which encourages further growth of these grasses 

while negatively impacting native desert vegetation (Williams and Baruch 2000). The vulnerability of habitats 

will depend on their proximity to sources of invasive grasses as well as natural fuel levels and ignition sources.

Research Needs

This species’ habitat requirements are not well known. Of particular interest is its association with water 

sources, which, if critical, will increase vulnerability to climate change. In addition, if seasonal hibernation is 

triggered by photoperiod (Winne and Keck 2004), then the species may be more prone to issues related to 

mismatched timing between emergence and favorable temperature or resource levels.

Management Implications

Although local occurrences are not well known, activities on BMGR that impact xeroriparian areas could be 

detrimental to this species. Of particular management concern with climate change is the vulnerability of 

these habitats to severe fire, including the increased probability of invasion by exotic grass species. Shrub and 

tree cover may be increasingly important for thermoregulation in a warmer climate, thus activities should be 

managed to reduce impacts on these features.
USDA Forest Service RMRS-GTR-284. 2012. 51

Habitat:	
  Red-­backed	
  whiptail (Aspidoscelis	
  xanthonota)

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	
  has	
  a	
  restricted	
  range	
  within	
  Sonoran	
  

desertscrub	
  of	
  Arizona	
  (Brennan	
  and	
  Holycross	
  2006).	
  It

occurs	
  in	
  upland	
  Sonoran	
  desertscrub	
  of	
  south	
  central	
  

Arizona	
  and	
  into	
  Mexico	
  above	
  2000	
  ft.	
  Associated	
  with	
  

valley	
  bottom	
  floodplains,	
  xeroriparian	
  scrub,	
  dunes,	
  and	
  

various	
  desertscrub	
  habitats	
  (Hall	
  and	
  others).	
  Prefers	
  

rocky	
  slopes	
  and	
  canyon	
  bottoms	
  (Brennan	
  and	
  

Holycross	
  2006).	
  No	
  expected	
  overall	
  changes	
  expected	
  

for	
  Sonoran	
  desertscrub	
  and	
  dune	
  habitats.

0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Lay	
  eggs	
  underground	
  in	
  burrows.	
  Soils	
  suitable	
  for	
  

burrowing	
  not	
  expected	
  to	
  change.

0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Litter	
  and	
  debris	
  seems	
  to	
  be	
  important	
  for	
  foraging	
  and	
  

escaping	
  predators	
  in	
  the	
  canyon	
  spotted	
  whiptail	
  

(BISON-­‐M),	
  but	
  not	
  known	
  if	
  similarly	
  important	
  for	
  this	
  

species. 0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Presence	
  is	
  often	
  associated	
  with	
  canyon	
  bottoms	
  near	
  

springs	
  and	
  tinajas	
  (Brennan	
  and	
  Holycross	
  2006),	
  which	
  

may	
  have	
  increased	
  prey.	
  Water	
  sources	
  expected	
  to	
  be	
  

reduced. 1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Little	
  information,	
  but	
  assumed	
  to	
  be	
  highly	
  mobile.

-­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

No	
  migratory	
  habitats	
  required.

0
52 USDA Forest Service RMRS-GTR-284. 2012.

Physiology:	
  Red-­backed	
  whiptail (Aspidoscelis	
  xanthonota)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Heliothermic	
  and	
  average	
  thermal	
  maxima	
  of	
  29	
  °C	
  in	
  this	
  

family	
  (Sinervo	
  and	
  others	
  2010).	
  There	
  was	
  no	
  limiting	
  

factor	
  relating	
  to	
  high	
  temperature	
  extremes	
  for	
  two	
  

other	
  species	
  of	
  whiptails	
  (A.	
  inornata	
  and	
  A.	
  gularis)	
  

(Winne	
  and	
  Keck,	
  2004).	
  Assume	
  similar	
  tolerance	
  for	
  

high	
  temperatures	
  for	
  this	
  species.

0

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Escapes	
  some	
  exposure	
  through	
  hibernation	
  during	
  cold	
  

or	
  hot	
  months.	
  No	
  effects	
  of	
  disturbance	
  known.

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Active	
  during	
  spring	
  and	
  fall	
  and	
  hibernate	
  during	
  cold	
  or	
  

very	
  hot	
  temperatures.	
  Heliothermic	
  and	
  daily	
  periods	
  

favorable	
  for	
  activity	
  expected	
  to	
  be	
  reduced	
  by	
  warmer	
  

temperatures	
  in	
  hot	
  climates	
  such	
  as	
  at	
  BMGR.	
   1

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

No	
  strategies	
  known.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic.

0

Phenology:	
  Red-­backed	
  whiptail (Aspidoscelis	
  xanthonota)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?

Seasonal	
  activity	
  patterns	
  as	
  related	
  to	
  soil	
  temperatures	
  

were	
  experimentally	
  tested	
  in	
  whiptails.	
  Although	
  

cessation	
  of	
  activities	
  occurred	
  during	
  high	
  temperatures,	
  

cessation	
  was	
  controlled	
  by	
  circadian	
  rhythm	
  rather	
  than	
  

triggered	
  by	
  exogenous	
  factors	
  such	
  as	
  temperature	
  or	
  

food	
  intake	
  (Winne	
  and	
  Keck	
  2004).

0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?

Lay	
  eggs	
  in	
  early	
  to	
  mid	
  summer	
  (Brennan	
  and	
  Holycross	
  

2006).	
  Precipitation	
  related	
  to	
  variability	
  of	
  food	
  

resources	
  in	
  A.	
  tigris	
  (Pianka	
  1970),	
  and	
  timing	
  of	
  

precipitation	
  is	
  expected	
  to	
  change. 1
USDA Forest Service RMRS-GTR-284. 2012. 53

Phenology:	
  Red-­backed	
  whiptail (Aspidoscelis	
  xanthonota)

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	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

No	
  direct	
  response	
  to	
  resources,	
  and	
  initiation	
  of	
  breeding	
  

is	
  not	
  very	
  distant	
  from	
  resources.

0

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  reproductive	
  event	
  per	
  year	
  (Brennan	
  and	
  Holycross	
  

2006).

1

Biotic	
  Interactions:	
  Red-­backed	
  whiptail (Aspidoscelis	
  xanthonota)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Preys	
  on	
  a	
  variety	
  of	
  insects	
  including	
  ants,	
  termites,	
  

beetles,	
  and	
  caterpillars,	
  as	
  well	
  as	
  spiders	
  (Brennan	
  and	
  

Holycross	
  2006).	
  Clutch	
  size	
  of	
  A.	
  tigris	
  was	
  positively	
  

related	
  to	
  total	
  precipitation	
  of	
  last	
  5	
  years	
  (probably	
  due	
  

to	
  affect	
  on	
  food	
  resources)	
  and	
  inversely	
  related	
  to	
  

variation	
  in	
  precipitation	
  of	
  last	
  5	
  years	
  (Pianka	
  1970).	
  

Precipitation	
  expected	
  to	
  become	
  more	
  variable,	
  thereby

increasing	
  years	
  of	
  low	
  food	
  abundance.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

No	
  information	
  on	
  predators,	
  but	
  likely	
  various.	
  No	
  

expected	
  change	
  to	
  predation	
  rates. 0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

No	
  known	
  diseases.

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

No	
  known	
  competitors,	
  although	
  potentially	
  other	
  

whiptails. 0
54 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s comprehensive wildlife conservation strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Asplund, K. K. 1970. Metabolic scope and body temperatures of whiptail lizards (Cnemidophorus). 

Herpetologica 26:403-411.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257. 

Brennan, T. C. and A. T. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game 

and Fish Department. Phoenix, AZ.

Esser, Gerd. 1992. Implications of climate change for production and decomposition in grasslands and 

coniferous forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17. 

Hall, J. A., P. Comer, A. Gondor, R. Marshall, and S. Weinstein. 2001. Conservation Elements of and a 

Biodiversity Management Framework for the Barry M. Goldwater Range, Arizona. The Nature Conservancy 

of Arizona, Tucson. 199 + ix p. + 15 unpaginated figures.

Milstead, W. W. 1957. Observations on the natural history of four species of whiptail lizard, Cnemidophorus

(Sauria, Teiidae) in Trans-Pecos Texas. Southwestern Naturalist 2:105-121.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T.J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Pianka, E. R. 1970. Comparative autecology of the lizard Cnemidophorus tigris in different parts of its 

geographic range. Ecology 51:703-720.

Rogers, G. F. and M. K. Vint. 1987. Winter precipitation and fire in the Sonoran Desert. Journal of Arid 

Environments 13: 47-52.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Sinervo, B., F. Méndez-de-la-Cruz, D. B. Miles, [and others]. 2010. Erosion of lizard diversity by climate change 

and altered thermal niches. Science 328:894-899.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.

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.
USDA Forest Service RMRS-GTR-284. 2012. 55

Yuman Desert Fringe-toed Lizard

(Uma rufopunctata)

SUMMARY

Despite the fact that the Yuman desert fringe-toed lizard is adapted to a very hot and dry environment, it is 

vulnerable to declines associated with projected changes in climate. Vulnerability was identified for all categories, but was highest for physiological response. Management of dune habitats, including maintenance of 

vegetation that provides shade, will likely be important to sustaining future populations. Additionally, changes 

to local burrowing mammal populations may have indirect impacts and should be monitored.

VULNERABILITY Score Uncertainty

Habitat 1.4 29%

Physiology 1.5 17%

Phenology 0.8 0%

Interactions 1.0 60%

Overall 5.2 27%

Introduction

Taxonomy has changed for this and related species leaving some confusion about designation of species. In 

addition, individuals from the Mohawk Dunes may be from a yet undescribed species (Trepanier and Murphy 

2001). Yuman desert fringe-toed lizard was once formerly recognized as Cowles fringe-toed lizard (Uma notata 

rufopunctata) or grouped with the Sonoran fringe-toed lizard (Uma notata). It is listed by the Arizona Game 

and Fish Department as a species of greatest conservation need (AGFD 2006). Furthermore, it is identified as a 

species conservation element in the proposed biodiversity management framework for BMGR (Hall and others 

2001).

Fringe-toed lizards are adapted to life on wind-blown sand dunes. They also occur on large sand flats and 

prefer habitats that are sparsely vegetated. They are found on the west section as well as the far western 

end of the eastern section of BMGR, particularly the Mohawk Dunes area. Regardless of the exact taxonomic 

relationships among species and subspecies, vulnerability scores apply to the fringe-toed lizards that occupy 

dune habitats at BMGR.

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

-5 0 5

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0
56 USDA Forest Service RMRS-GTR-284. 2012.

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

Dune habitats are limited and fragmented at BMGR. Invasive plants, including Saharan mustard (Brassica 

tournefortii), Arabian schismus (Schismus arabicus), and Mediterranean grass (Schismus barbatas), are 

encroaching on dune habitats, compromising their suitability. In addition, vehicular use of dunes, including 

use for military training, recreation, and law enforcement, can collapse animal burrows. Buffering of climate 

impacts varies with factors such as irrigation and government programs, both of which predict that drought 

impacts will be less severe in the United States as compared to Mexico (Vásquez-León and others 2003). In the 

absence of alterations to immigration policies, increased illegal traffic at the international border is expected. 

Barriers such as roads or fences can disrupt sand dune formation.

In an evaluation of climate change affects related to energetics, for this family, Phynosomatidae, 3% of species 

were identified as likely to go extinct by 2050 (Sinervo and others 2010). There may be more need for body 

cooling, and quality of shade may be an important factor in future suitable habitat.

Research Needs

Basic life history information is limited for this species. Research related to drought effects on lizard 

populations would be particularly helpful. In addition, evaluation of thermal properties of various suitable 

habitats would be informative for habitat management planning.

Management Implications

Management related to vehicles in fringe-toed lizard habitats will continue to be important. Planning should 

include the likelihood of increasing threats from vehicles and border security activities. Factors related to 

vegetation distribution are already known to be important for this species, but the importance of shade 

should further refine targeted shrub species that provide the best protection from increasing temperatures. 

Small burrowing mammals on dunes may be vulnerable to higher temperatures reducing availability of 

suitable burrows. Monitoring or management related to burrow availability may be necessary. Variability in 

rainfall and its association with breeding success may mean greater annual population fluctuations and, thus, 

greater habitat area requirements to sustain populations of this species in the future.
USDA Forest Service RMRS-GTR-284. 2012. 57

Habitat:	
  Yuman	
  desert	
  fringe-­toed	
  lizard	
  (Uma	
  rufopunctata)

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?

Yuman	
  fringe-­‐toed	
  lizards	
  require	
  sand	
  habitats	
  (either	
  

dunes	
  or	
  flats)	
  that	
  are	
  sparsely	
  vegetated.	
  Occurs	
  in	
  dune	
  

habitats	
  with	
  some	
  vegetation	
  such	
  as	
  bursage	
  and	
  

creosote	
  (AGFD	
  2003).	
  No	
  change	
  expected	
  in	
  dune	
  area. 0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Eggs	
  are	
  buried	
  in	
  moist	
  sand	
  (Brennan	
  and	
  Holycross	
  

2006).	
  Sand	
  availability	
  is	
  not	
  expected	
  to	
  change	
  (but	
  see	
  

Phenology,	
  Question	
  2) 0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Burrows	
  in	
  sand	
  to	
  escape	
  predators	
  and	
  is	
  more	
  likely	
  to	
  

occur	
  in	
  areas	
  with	
  more	
  sand	
  and	
  less	
  vegetation,	
  but	
  

require	
  some	
  vegetation	
  for	
  predator	
  escape	
  and	
  

thermoregulation	
  (Pough	
  1970).	
  Vegetation	
  that	
  provides	
  

suitable	
  shade	
  is	
  expected	
  to	
  be	
  reduced	
  with	
  increasing	
  

droughts.	
  Burrows	
  also	
  required	
  for	
  hibernation	
  (see	
  

Interactions,	
  Question	
  3)

1

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Species	
  presence	
  is	
  associated	
  with	
  greater	
  quantities	
  of	
  

sand,	
  but	
  unknown	
  connection	
  to	
  survival	
  though	
  

potentially	
  allows	
  for	
  better	
  escape	
  from	
  predators.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Little	
  information.	
  Probably	
  have	
  fairly	
  limited	
  

movements	
  and	
  may	
  be	
  restricted	
  by	
  patchiness	
  of	
  dune	
  

habitats.

1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Not	
  migratory.

0
58 USDA Forest Service RMRS-GTR-284. 2012.

Physiology:	
  Yuman	
  desert	
  fringe-­toed	
  lizard	
  (Uma	
  rufopunctata)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

This	
  species	
  already	
  experiences	
  very	
  high	
  temperatures.	
  

Species	
  in	
  this	
  family	
  may	
  be	
  prone	
  to	
  extinction	
  based	
  on	
  

body	
  temperatures	
  and	
  activity	
  restrictions	
  imposed	
  by	
  

hot	
  temperatures	
  (Sinervo	
  and	
  others	
  2010).

1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Hibernates	
  underground	
  in	
  existing	
  burrows	
  during	
  the	
  

cold	
  months	
  of	
  winter	
  and	
  late	
  fall	
  (AGFD	
  2003),	
  thus	
  may	
  

escape	
  many	
  storms.	
  No	
  known	
  mortality	
  factors	
  with	
  

disturbance. 0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Requires	
  vegetation	
  for	
  shade,	
  so	
  prone	
  to	
  increasing	
  

need	
  to	
  use	
  shade	
  on	
  hot	
  days,	
  thus	
  reducing	
  active	
  

periods.	
   1

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

None	
  known.

1

6.	
  Metabolic	
  

rates

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic. -­1

Phenology:	
  Yuman	
  desert	
  fringe-­toed	
  lizard	
  (Uma	
  rufopunctata)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Temperature	
  affects	
  emergence	
  from	
  hibernation,	
  egg	
  

development,	
  and	
  surface	
  activity	
  (AZGFD	
  2003).	
  

Photoperiod	
  was	
  more	
  important	
  than	
  temperature	
  in	
  

determining	
  egg	
  laying	
  in	
  Uma	
  notata	
  (Mayhew	
  1961).	
  

Hibernation	
  timing	
  is	
  vulnerable	
  to	
  changes	
  in	
  

temperature.

1

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Lay	
  eggs	
  from	
  May	
  through	
  August	
  (AGFD	
  2003).	
  Eggs	
  are	
  

buried	
  in	
  moist	
  sand	
  (Brennan	
  and	
  Holycross	
  2006).	
  

Moist	
  periods	
  will	
  likely	
  change	
  as	
  seasonal	
  rainfall	
  shifts.

1

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

No	
  large	
  distance	
  between	
  breeding	
  and	
  resources.

0
USDA Forest Service RMRS-GTR-284. 2012. 59

Phenology:	
  Yuman	
  desert	
  fringe-­toed	
  lizard	
  (Uma	
  rufopunctata)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

4.	
  Resilience

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Females	
  may	
  lay	
  more	
  than	
  one	
  clutch	
  per	
  year,	
  but	
  

forego	
  reproduction	
  when	
  food	
  is	
  scarce	
  (Mayhew	
  1966).

-­1

Biotic	
  Interactions:	
  Yuman	
  desert	
  fringe-­toed	
  lizard	
  (Uma	
  rufopunctata)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Omnivorous	
  and	
  eat	
  a	
  wide	
  variety	
  of	
  insects	
  and	
  

vegetation	
  (Turner	
  and	
  Schwalbe	
  1998).	
  No	
  reproduction	
  

occurs	
  in	
  years	
  with	
  low	
  invertebrate	
  abundance,	
  thus	
  

these	
  types	
  of	
  foods	
  are	
  limiting	
  to	
  populations.	
  All	
  

invertebrate	
  prey	
  are	
  not	
  likely	
  to	
  decline	
  or	
  increase	
  

simultaneously.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Likely	
  various	
  birds	
  and	
  mammals.	
  No	
  overall	
  changes	
  

expected. 0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

Requires	
  other	
  animals	
  to	
  create	
  burrows	
  for	
  hibernation.	
  

Uses	
  animal	
  burrows	
  for	
  hibernation	
  (AGFD	
  2003).	
  Fewer	
  

burrowing	
  mammals	
  may	
  occupy	
  these	
  habitats	
  as	
  they	
  

get	
  hotter.

1

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

None	
  known.

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

None	
  known.

0
60 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2003. Uma rufopunctata. Unpublished abstract compiled and edited by 

the Heritage Data Management System, Arizona Game and Fish Department, Phoenix, AZ.

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s comprehensive wildlife conservation strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257. 

Brennan, T. C., and A. T. Holycross. 2006. A field guide to amphibians and reptiles in Arizona. Arizona Game 

and Fish Department. Phoenix, AZ.

Esser, Gerd. 1992. Implications of climate change for production and decomposition in grasslands and 

coniferous forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17. 

Hall, J. A., P. Comer, A. Gondor, R. Marshall, and S. Weinstein. 2001. Conservation Elements of and a 

Biodiversity Management Framework for the Barry M. Goldwater Range, Arizona. The Nature Conservancy 

of Arizona, Tucson. 

Mayhew, W. 1961. Photoperiodic response in female fringe-toed lizards. Science 134:2104-2105.

Mayhew, W. W. 1966. Reproduction in the psammophilous lizard Uma scoparia. Copeia 1:114-122.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Pough, F. H. 1970. The burrowing ecology of the sand lizard, Uma notata. Copeia: 1970:145-157.

Seager, R., T. Ming, and I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Trepanier, T. L. and R. W. Murphy. 2001. The Coachella Valley fringe-toed lizard (Uma inornata): genetic 

diversity and phylogenetic relationships of an endangered species. Molecular Phylogenetics and Evolution 

18:327-334.

Turner, D. S. and C. R. Schwalbe. 1998. Ecology of Cowles fringe-toed lizard. Arizona Game and Fish 

Department Heritage Fund IIPAM Project No. I95042. Final Report to Arizona Game and Fish Department. 

78 p. 

Vásquez-León, Marcela, C. T. West, and T. J. Finan. 2003. A comparative assessment of climate vulnerability: 

agriculture and ranching on both sides of the US-Mexico border. Global Environmental Change 13:159-173.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 61

American Peregrine Falcon

(Falco peregrinus anatum)

SUMMARY

Peregrine falcons are flexible in their habitat use, which will help them cope with climate change effects to 

some extent. Phenology, as related to prey levels, is an area of potential vulnerability depending on whether 

different aspects shift in concert. Although Arizona habitats are expected to remain suitable in the near future, 

the falcons will be exposed to other climate change effects at wintering and stopover sites. If falcons are found 

breeding, any restriction of military activities near nesting sites needs to consider future breeding timing 

changes.

VULNERABILITY Score Uncertainty

Habitat -0.1 0%

Physiology 0.8 33%

Phenology 2.5 25%

Interactions 2.0 20%

Overall 4.4 18%

Introduction

Peregrine falcons are not known to nest on BMGR and may only be transients. The species was Federally listed 

in 1970 and delisted in 1999. However, the Arizona Game and Fish Department designated the American 

peregrine falcon as a species of greatest conservation need, Tier 1B, in the Arizona State Wildlife Action Plan 

(AGFD 2006).

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• Decreased annual rainfall in Central America (Magrin and others 2007)

-5 0 5

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0
62 USDA Forest Service RMRS-GTR-284. 2012.

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

Population declines in the past are thought to have been primarily due to DDT use, and populations are 

recovering. Because this species is migratory, climate or land-use changes in Mexico and Central America will 

affect populations in Arizona.

Research Needs

Wintering habitat requirements for this species are not well known. Migration routes and destinations are also 

not well known for populations in the southwest United States. In addition, physiological thresholds as they 

relate to increasing temperatures in hotter portions of the falcon’s range are needed to predict climate change 

response.

Management Implications

Territory size and spacing is related to nest site and prey availability (White and others 2002). Both are 

probably relatively low in this region, thus it is unlikely that management actions will affect more than a few 

individuals. Peregrine falcons drink frequently (White and others 2002), and water needs will likely increase 

in the future, thus management related to water sources, including artificial waters, will be important. 

Monitoring and identification of suitable nesting habitats will indicate if further measures need to be taken. 

If nesting is confirmed, restriction of activities at suitable nesting sites is important and managers should plan 

for shifts in breeding timing.
USDA Forest Service RMRS-GTR-284. 2012. 63

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?

Occupies	
  a	
  wide	
  variety	
  of	
  habitats,	
  including	
  forests,	
  

grasslands,	
  and	
  scrublands	
  (White	
  and	
  others	
  2002).	
  

Most	
  of	
  BMGR	
  has	
  suitable	
  vegetation	
  and	
  should	
  

continue	
  to	
  remain	
  suitable	
  despite	
  changes	
  in	
  

dominance	
  of	
  specific	
  vegetation	
  types.

0

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?

Occupies	
  even	
  wider	
  range	
  of	
  habitats	
  in	
  winter.	
  No	
  

expected	
  changes.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Vertical	
  substrate	
  with	
  ledges	
  for	
  nesting.	
  Mostly	
  cliffs,	
  

but	
  will	
  also	
  use	
  buildings	
  in	
  urban	
  areas.	
  No	
  projected	
  

changes	
  to	
  cliffs. 0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Uses	
  perches	
  to	
  scan	
  for	
  prey.	
  Wide	
  variety	
  of	
  perch	
  

locations	
  with	
  no	
  expected	
  change	
  in	
  availability.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success

or	
  survival	
  expected	
  

to	
  change?	
  

Reproductive	
  success	
  has	
  been	
  related	
  to	
  female	
  age,	
  but	
  

not	
  habitat	
  variables	
  (White	
  and	
  others	
  2002).

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Highly	
  mobile.

-­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Migratory.	
  Birds	
  that	
  breed	
  in	
  more	
  southerly	
  locations	
  

may	
  actually	
  travel	
  less	
  south	
  into	
  Mexico	
  than	
  those	
  that	
  

breed	
  in	
  the	
  far	
  north,	
  which	
  may	
  travel	
  to	
  Central	
  

America	
  to	
  winter	
  (White	
  and	
  others	
  2002). 1
64 USDA Forest Service RMRS-GTR-284. 2012.

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?

One	
  of	
  the	
  most	
  widely	
  distributed	
  vertebrate	
  species,	
  

peregrine	
  falcons	
  are	
  tolerant	
  of	
  a	
  wide	
  range	
  of	
  

conditions	
  (White	
  and	
  others	
  2002).	
  Convective	
  cooling	
  

through	
  the	
  bare	
  tarsus	
  is	
  considered	
  important,	
  and	
  this	
  

surface	
  area	
  varies	
  with	
  region	
  (White	
  and	
  others	
  2002).	
  

Not	
  expected	
  to	
  be	
  limited,	
  although	
  no	
  specific	
  

information.

0

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Thought	
  to	
  be	
  less	
  prone	
  to	
  mortality	
  from	
  adverse	
  

weather	
  during	
  migration	
  than	
  many	
  other	
  bird	
  species	
  

(White	
  and	
  others	
  2002).	
  Nestlings	
  vulnerable	
  to	
  late,	
  wet	
  

springs	
  (White	
  and	
  others	
  2002).	
  Spring	
  expected	
  to	
  

occur	
  earlier	
  rather	
  than	
  later,	
  although	
  this	
  may	
  not	
  be	
  a	
  

major	
  factor	
  in	
  warmer	
  climates.

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Most	
  cooling	
  is	
  through	
  behaviors	
  such	
  as	
  orientation,	
  

erection	
  of	
  feathers,	
  or	
  panting.	
  No	
  known	
  limitations	
  to	
  

daily	
  active	
  period. 0

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

None	
  known.	
  Only	
  rare	
  records	
  of	
  cooperative	
  breeding	
  

(White	
  and	
  others	
  2002).

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic,	
  although	
  higher	
  than	
  congeneric	
  

species	
  (White	
  and	
  others	
  2002). 0

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Timing	
  of	
  migration	
  and	
  breeding	
  seems	
  to	
  be	
  in	
  response	
  

to	
  a	
  wide	
  variety	
  of	
  signals,	
  including	
  climate,	
  

photoperiod,	
  and	
  prey	
  levels	
  (White	
  and	
  others	
  2002).	
  

Not	
  a	
  direct	
  response	
  to	
  temperature	
  alone. 0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Based	
  on	
  areas	
  with	
  similar	
  climates,	
  egg	
  laying	
  occurs	
  

from	
  March	
  to	
  April	
  (White	
  and	
  others	
  2002).	
  Likely	
  that	
  

breeding	
  is	
  timed	
  to	
  prey	
  levels	
  that	
  fluctuate	
  with	
  

breeding	
  of	
  other	
  species,	
  which,	
  in	
  turn,	
  is	
  subject	
  to	
  

climate-­‐related	
  changes. 1
USDA Forest Service RMRS-GTR-284. 2012. 65

Phenology:	
  American	
  peregrine	
  falcon (Falco	
  peregrinus	
  anatum)

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	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

In	
  some	
  areas,	
  migratory	
  behaviors	
  seem	
  to	
  be	
  in	
  direct	
  

response	
  to	
  prey	
  levels	
  (White	
  and	
  others	
  2002).	
  This	
  

seems	
  to	
  be	
  limited	
  to	
  leaving	
  breeding	
  grounds,	
  and	
  

breeding	
  timing	
  is	
  not	
  likely	
  to	
  be	
  very	
  flexible	
  to	
  resource	
  

timing. 0

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with

important	
  events?

One	
  brood	
  per	
  year.

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?

Most	
  important	
  prey	
  are	
  birds	
  although	
  a	
  wide	
  variety	
  of	
  

species	
  from	
  various	
  taxonomic	
  groups	
  are	
  also	
  eaten	
  

(White	
  and	
  others	
  2002).	
  Doves	
  are	
  likely	
  important	
  prey	
  

in	
  this	
  region	
  and	
  may	
  decline	
  with	
  shrinking	
  water	
  

sources.	
  

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Great	
  horned	
  owls	
  are	
  an	
  important	
  predator	
  on	
  young,	
  

but	
  predation	
  for	
  adults	
  is	
  probably	
  not	
  frequent.	
  No	
  

expected	
  changes	
  in	
  predation	
  levels.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

Some	
  secondary	
  infection	
  through	
  prey	
  of	
  Trichomonas	
  

(White	
  and	
  others	
  2002).	
  Infections	
  may	
  increase	
  with	
  

increased	
  transmission	
  in	
  doves	
  from	
  crowding	
  at	
  

shrinking	
  water	
  sources. 1

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

No	
  major	
  competitors	
  known.

0
66 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s comprehensive wildlife conservation strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17. 

Liverman, D. M. and K. L. O’Brien. 1991. Global Warming and Climate Change in Mexico. Pages 351-364 In 

Global Environmental Change. Butterworth-Heinemann Ltd.

Magrin, G., C. G. García, D. Cruz Choque, J. C. Giménez, A. R. Moreno, G. J. Nagy, C. Nobre, and A. Villamizar. 

2007. Latin America. Pages 581-615 In M. L. Parry, 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 

University Press, Cambridge, UK.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: Mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Scholze, M., W. Knorr, N. W. Arnell, and I. C. Prentice. 2005. A climate change risk analysis for world 

ecosystems. Proceedings of the National Academy of Sciences 103:13116-13120.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

White, C. M., N. J. Clum, T. J. Cade, and W. G. Hunt. 2002. Peregrine Falcon (Falco peregrinus). In A. Poole, ed., 

The Birds of North America Online. Ithaca: Cornell Lab of Ornithology.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 67

Cactus Ferruginous Pygmy-Owl

(Glaucidium brasilianum cactorum)

SUMMARY

The cactus ferruginous pygmy-owl is vulnerable to declines associated with a warming climate. Vulnerabilities 

are associated with changes expected for xeroriparian habitats and interactions with other cavity nesting species. In addition, this species possesses few resilient traits that could help it cope with changing conditions. 

Management related to fire and to both plant and animal invasive species will be important.

VULNERABILITY Score Uncertainty

Habitat 1.3 100%

Physiology 0.8 33%

Phenology 2.5 50%

Interactions 1.0 60%

Overall 5.3 64%

Introduction

The cactus ferruginous pygmy-owl is a subspecies of the ferruginous pygmy-owl. This subspecies occurs at the 

northern end of the species’ distribution, which reaches all the way to Tierra del Fuego (Cartron and others 

2000). The Arizona population was listed as a distinct population segment until 2006, when it was determined 

that this designation was unsupported (Federal Register/Vol. 71/April 14, 2006). It was listed in Arizona as 

Federally endangered in 1997 after apparent population declines. As of June 2008, the USFWS determined a 

review of the status of this subspecies was warranted and initiated a status review (Federal Register/Vol. 73/

June 2, 2008). The petition for this status review identified populations in the western United States as distinct 

and as Glaucidium ridgwayi cactorum (G. brasilianum being restricted to South America) (Proudfoot and 

others 2006). The findings of this review were not available at the time of this report. The USFWS found that 

listing was not warranted for the entire species range or as distinct population segments (Federal Register/Vol. 

76/Oct. 5, 2011). The State of Arizona identifies this as a species of greatest conservation need, Tier 1A (AGFD 

2006). Population declines may have begun as early as the 1920s and are likely related to loss and degradation 

of riparian habitats (Johnson and others 2003). Populations remain low and fragmented in Arizona. The only 

other U.S. occurrences are in Texas where populations are not proposed for Federal listing and may be from a 

different subspecies.

Cactus ferruginous pygmy-owls occur in Organ Pipe Cactus National Monument, Cabeza Prieta National 

Wildlife Refuge, and on Tohono O’odham Nation lands (USFWS 2003). They are not recorded on BMGR as of 

the time of this report but have the potential to occur, particularly in the Sauceda and Sand Tanks Mountains 

(Hall and others 2001), and there have been several unconfirmed sightings on BMGR (USFWS 2003).

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

-5 0 5
68 USDA Forest Service RMRS-GTR-284. 2012.

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

• CAM plants (succulents and cacti) will be resilient to increasing temperatures (Smith and others 1984)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

Destruction of riparian woodlands in Arizona is likely to have played a significant role in the decline of this 

species (Johnson and others 1979), and continued degradation of these habitats is of concern. Changes in 

hydrologic regimes and warmer temperatures along with increased wildfires and human demands for water 

with climate change will only increase the threat to the species’ habitat. Individuals are also susceptible 

to injury or death from collisions with traffic (USFWS 2003). In addition, they may abandon nests or alter 

movements in response to disturbance (USFWS 2003), including disturbance associated with military 

activities.

Projected increases in climate variability will increase fire occurrence as years of high rainfall are followed by 

dry/hot conditions, creating conditions conducive both to fire ignition and fuel accumulation. Although some 

level of fire occurrence may be beneficial to ferruginous pygmy-owl habitats, fires that are intense enough to 

kill plants used for nesting or encourage conversion to other habitat types will be detrimental. Fire regimes 

in the region have also been altered by introduced plant species that provide fine fuels to carry fire. Red 

brome (Bromus rubens), Mediterranean grass (Schismus barbatus), and Sahara mustard (Brassica tournefortii) 

are common invasives in the region. Buffelgrass (Pennisetum ciliare) promotes a frequent high severity fire 

regime, which encourages further growth of grasses while negatively impacting native desert vegetation 

(Williams and Baruch 2000).

Research Needs

In general, there is only limited information about the life history and population demographics of the 

species, particularly from outside the United States. Little is known about the habitat quality of locations 

where pygmy-owls are found (Cartron and others 2000c), but this would provide valuable information for 

conservation. Also, information is needed on responses to land management practices such as grazing and 

recreation. For example, is installation of nest boxes a viable option for sustaining populations (Cartron 

and others 2000c)? Information is needed on limiting factors at the northern range boundary and dispersal 

behaviors, which is important for determining the potential for population increase or range expansion 

in the United States (Proudfoot and others 2000). Investigation into the factors involved in the apparent 

shift in habitat use from riparian woodlands to desert scrub may also shed light on the species’ potential 

response to changing climatic conditions. Studies of basic ecological and physiological information could be 

more successful in locations where populations are larger. The USFWS (2003) noted that information about 

populations in Mexico and their interaction with populations in Arizona is critical to understanding the degree 
USDA Forest Service RMRS-GTR-284. 2012. 69

of isolation of the U.S. population and management needs. The owl’s interactions with other species are also 

poorly understood.

Management Implications

Management actions that protect large trees and saguaros while promoting understory growth should 

favor the ferruginous pygmy-owl. Management of introduction and spread of invasive grasses will also be 

important. Invasive grasses can degrade xeroriparian habitats as well as encourage fires, which will remove 

important shrubs and trees for this species. Management related to control of invasive grasses will be 

especially important as desert washes will be prone to invasion. Careful use of prescribed fire may enhance 

habitat suitability (USFWS 2003) and may protect habitats from more severe fires. 

Post-fire rehabilitation of habitats is also an important management planning consideration as high severity 

fires will be inevitable. Nest boxes could mitigate some loss of trees or cactus, but attention should be given to 

box microclimate during construction and placement. Although active management of competing non-native 

cavity nesters may not be necessary, care should be taken to not enhance habitats for these species.
70 USDA Forest Service RMRS-GTR-284. 2012.

Habitat:	
  Cactus	
  ferruginous	
  pygmy-­owl	
  (Glaucidium	
  brasilianum	
  cactorum)

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	
  Arizona,	
  the	
  cactus	
  ferruginous	
  pygmy	
  owl	
  occurs	
  in	
  

Sonoran	
  desert	
  scrub	
  and	
  xeroriparian	
  vegetation,	
  but	
  

historically	
  was	
  also	
  associated	
  with	
  cottonwood	
  and	
  

mesquite	
  riparian	
  woodlands	
  (Cartron	
  and	
  others

2000b).	
  Desert	
  scrub	
  habitats	
  may	
  be	
  of	
  marginal	
  quality,	
  

but	
  may	
  play	
  an	
  important	
  role	
  in	
  habitat	
  connectivity.	
  A	
  

complex	
  landscape	
  of	
  edges,	
  dense	
  shrubs,	
  and	
  open	
  

overstory	
  seems	
  to	
  be	
  important.	
  Habitat	
  requirements	
  

are	
  not	
  well	
  known.	
  Although	
  desert	
  scrub	
  will	
  likely	
  

remain,	
  xeroriparian	
  habitats	
  with	
  trees	
  and	
  shrubs	
  will	
  

be	
  more	
  vulnerable	
  to	
  declines	
  associated	
  with	
  water	
  

table	
  declines	
  as	
  well	
  as	
  increasing	
  fires.

1

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.

1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Trees	
  or	
  cactus	
  large	
  enough	
  to	
  support	
  cavities	
  are	
  

required	
  for	
  breeding.	
  Saguaro	
  cactus	
  are	
  commonly	
  used	
  

nesting	
  substrates	
  in	
  Arizona	
  (Cartron	
  and	
  others	
  2000b).	
  

Require	
  suitable	
  substrate	
  for	
  nesting	
  cavities.	
  Dependent	
  

on	
  excavating	
  species	
  (see	
  Interactions).	
  Large	
  trees	
  are	
  

prone	
  to	
  fire	
  and	
  drought.	
  Cactus	
  are	
  likely	
  more	
  resilient	
  

and	
  often	
  occupy	
  habitats	
  less	
  prone	
  to	
  fire	
  (but	
  see	
  other	
  

threats).	
  Nests	
  located	
  1996-­‐2002	
  in	
  Arizona	
  were	
  

primarily	
  in	
  saguaro	
  cactus.

0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Cavities	
  are	
  also	
  used	
  for	
  caching	
  prey,	
  so	
  number	
  of	
  

cavities	
  may	
  be	
  associated	
  with	
  habitat	
  selection	
  

(Proudfoot	
  and	
  others	
  2000).	
  Same	
  as	
  above.	
  

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Seem	
  to	
  be	
  associated	
  with	
  proximity	
  to	
  forest	
  patches	
  

and	
  edges	
  of	
  open	
  woodlands	
  (USFWS	
  2003).	
  Understory	
  

cover	
  may	
  be	
  important	
  for	
  survival,	
  particularly	
  of	
  

fledglings	
  (USFWS	
  2003).	
  It	
  is	
  not	
  known	
  if	
  fires	
  have	
  a	
  

positive	
  or	
  negative	
  effect	
  on	
  habitat	
  for	
  this	
  species	
  

(USFWS	
  2003),	
  although	
  throughout	
  its	
  range,	
  it	
  occurs	
  in	
  

second	
  growth	
  shrublands,	
  forest	
  edge	
  habitats,	
  and	
  

xeroriparian	
  habitats	
  (Cartron	
  and	
  others	
  2000b).	
  Drier	
  

conditions	
  will	
  likely	
  reduce	
  foliar	
  cover	
  and	
  increase	
  

shrub	
  mortality.

1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Generally	
  considered	
  to	
  be	
  permanent	
  resident	
  with	
  

dispersal	
  of	
  juveniles,	
  but	
  there	
  has	
  been	
  some	
  suggestion	
  

of	
  possible	
  migratory	
  behaviors	
  from	
  Sonora,	
  Mexico

(Proudfoot	
  and	
  others	
  2000;	
  USFWS	
  2003).	
  Juveniles	
  may	
  

disperse	
  more	
  than	
  20	
  km	
  (USFWS	
  2003).	
  Little	
  

information	
  is	
  available	
  on	
  site	
  fidelity	
  (Proudfoot	
  and	
  

others	
  2000). Highly	
  mobile	
  species	
  with	
  most	
  dispersal	
  

by	
  juveniles	
  of	
  both	
  sexes.

-­1
USDA Forest Service RMRS-GTR-284. 2012. 71

Habitat:	
  Cactus	
  ferruginous	
  pygmy-­owl	
  (Glaucidium	
  brasilianum	
  cactorum)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Does	
  not	
  require	
  transitional	
  habitats,	
  although	
  

movements	
  are	
  not	
  well	
  studied	
  (see	
  above).

0

Physiology:	
  Cactus	
  ferruginous	
  pygmy-­owl	
  (Glaucidium	
  brasilianum	
  cactorum)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Arizona	
  is	
  the	
  northern	
  edge	
  of	
  the	
  range	
  for	
  this	
  species	
  

(USFWS	
  2003)	
  and	
  may	
  be	
  less	
  suitable	
  than	
  more	
  

southerly	
  and	
  tropical	
  parts	
  of	
  the	
  range	
  (Johnson	
  and	
  

others	
  2003).	
  Although	
  this	
  species	
  lives	
  in	
  a	
  broad	
  

spectrum	
  of	
  physical	
  conditions,	
  does	
  not	
  possess	
  

specialized	
  adaptations	
  for	
  desert	
  conditions.	
  Very	
  hot	
  

environments,	
  such	
  as	
  BMGR,	
  may	
  exceed	
  tolerances	
  in	
  

the	
  future.

1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

No	
  information.

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

These	
  owls	
  are	
  active	
  primarily	
  during	
  the	
  day,	
  

particularly	
  at	
  dawn	
  and	
  dusk,	
  but	
  also	
  can	
  be	
  active	
  at	
  

night	
  (Proudfoot	
  and	
  Johnson	
  2000).	
  Night	
  activity	
  was	
  

drastically	
  reduced	
  4-­‐7	
  days	
  before	
  initiation	
  of	
  fledging	
  

(Proudfoot	
  and	
  Johnson	
  2000).

No	
  known	
  correspondence	
  of	
  activity	
  with	
  climate.

0

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

None	
  known,	
  although	
  flexible	
  migratory	
  behaviors	
  are	
  

potentially	
  helpful	
  if	
  present.

0

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic. 0

	
  	
  	
  
72 USDA Forest Service RMRS-GTR-284. 2012.

Phenology:	
  Cactus	
  ferruginous	
  pygmy-­owl	
  (Glaucidium	
  brasilianum	
  cactorum)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Probably	
  use	
  combination	
  of	
  internal	
  and	
  external	
  signals	
  

to	
  initiate	
  breeding.

0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Mating	
  begins	
  in	
  February	
  with	
  egg	
  laying	
  in	
  late	
  April	
  to	
  

May.	
  Young	
  fledge	
  from	
  the	
  end	
  of	
  May	
  through	
  June	
  and	
  

disperse	
  from	
  natal	
  sites	
  end	
  of	
  July	
  through	
  August	
  

(Proudfoot	
  and	
  others	
  2000).	
  Breeding	
  likely	
  timed	
  to	
  

coincide	
  with	
  peak	
  food	
  availability	
  or	
  favorable	
  climate.	
  

Discrete	
  events	
  not	
  specifically	
  known,	
  but	
  prey	
  species	
  

often	
  subject	
  to	
  temperature-­‐related	
  fluctuations.

1

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Discrete	
  events	
  not	
  known,	
  but	
  not	
  likely	
  to	
  respond	
  

directly	
  to	
  resource	
  levels.

0

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  breeding	
  event,	
  and	
  re-­‐nesting	
  only	
  occurs	
  if	
  failure	
  

occurs	
  very	
  early	
  in	
  the	
  nesting	
  cycle.

1

Biotic	
  Interactions:	
  Cactus	
  ferruginous	
  pygmy-­owl	
  (Glaucidium	
  brasilianum	
  

cactorum)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Prey	
  items	
  include	
  birds,	
  lizards,	
  insects,	
  and	
  small	
  

mammals,	
  which	
  can	
  be	
  larger	
  than	
  the	
  pygmy-­‐owl.	
  

Reptiles	
  are	
  the	
  primary	
  prey	
  in	
  Arizona	
  (Cartron	
  and	
  

others	
  2000).	
  May	
  be	
  preyed	
  upon	
  by	
  larger	
  raptors,	
  but	
  

there	
  are	
  few	
  documented	
  cases	
  of	
  predation	
  (USFWS	
  

2003).	
  Reptiles	
  are	
  an	
  important	
  component	
  of	
  the	
  diet,	
  

but	
  various	
  species	
  are	
  taken	
  along	
  with	
  alternative	
  prey	
  

such	
  as	
  insects	
  and	
  small	
  mammals.	
  No	
  overall	
  changes	
  

expected	
  in	
  prey.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Important	
  predators	
  include	
  other	
  larger	
  raptors.	
  

Predation	
  is	
  not	
  likely	
  a	
  major	
  source	
  of	
  mortality. 0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

Needs	
  other	
  species	
  to	
  excavate	
  cavities.	
  Gila	
  

woodpeckers	
  and	
  northern	
  flicker	
  are	
  common	
  

excavators	
  of	
  the	
  cavities	
  used	
  by	
  the	
  pygmy-­‐owl	
  (Cartron	
  

and	
  others	
  2000).	
  A	
  wide	
  variety	
  of	
  other	
  secondary	
  

cavity	
  nesters	
  compete	
  for	
  cavities,	
  including	
  non-­‐native	
  

species	
  such	
  as	
  European	
  starlings	
  and	
  house	
  sparrows,	
  

0
USDA Forest Service RMRS-GTR-284. 2012. 73

Biotic	
  Interactions:	
  Cactus	
  ferruginous	
  pygmy-­owl	
  (Glaucidium	
  brasilianum	
  

cactorum)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

but	
  these	
  interactions	
  are	
  not	
  well	
  studied	
  (USFWS	
  2003).	
  

Generally	
  uses	
  cavities	
  created	
  by	
  Gila	
  woodpeckers	
  and	
  

northern	
  flickers,	
  but	
  not	
  limited	
  to	
  these	
  species.	
  Gila	
  

woodpeckers	
  were	
  assessed	
  as	
  relatively	
  neutral	
  to	
  

climate	
  change	
  at	
  BMGR.

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

May	
  be	
  susceptible	
  to	
  trichomoniasis,	
  which	
  is	
  

transmitted	
  from	
  infected	
  prey	
  (Cartron	
  and	
  others

2000).	
  West	
  Nile	
  virus	
  may	
  also	
  affect	
  this	
  species	
  

(USFWS	
  2003),	
  but	
  no	
  records.

Trichomoniasis	
  is	
  present	
  in	
  Arizona	
  and	
  could	
  be	
  passed	
  

through	
  infected	
  mourning	
  doves	
  or	
  pigeons.	
  Not	
  

expected	
  to	
  be	
  a	
  significant	
  source	
  of	
  mortality	
  as	
  these	
  

are	
  not	
  common	
  prey	
  items.	
  Transmission	
  of	
  West	
  Nile	
  

virus	
  from	
  mosquitoes	
  may	
  be	
  reduced	
  during	
  drier

conditions,	
  but	
  not	
  a	
  known	
  mortality	
  factor	
  in	
  this	
  

species.

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Competes	
  for	
  cavities	
  with	
  other	
  species.	
  General	
  

outcome	
  of	
  these	
  encounters	
  is	
  unknown.	
  Non-­‐natives	
  

such	
  as	
  starlings	
  and	
  house	
  finches	
  likely	
  compete	
  for	
  

cavities	
  and	
  are	
  likely	
  resilient	
  to	
  climate	
  change.

1
74 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s comprehensive wildlife conservation strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

Cartron, J. E., W. S. Richardson, and G. A. Proudfoot. 2000. The cactus ferruginous pygmy-owl: taxonomy, 

distribution, and natural history. Pages 5-16 In J.E. Cartron, D. Finch, tech. eds., Ecology and conservation of 

the cactus ferruginous pygmy-owl in Arizona. USDA Forest Service, Rocky Mountain Research Station, Gen. 

Tech. Rep. RMRS-GTR-43.

Cartron, J. E., S. H. Stoleson, S. M. Russell, G. A. Proudfoot, and W. S. Richardson. 2000b. The ferruginous 

pygmy-owl in the tropics and at the northern end of its range: habitat relations and requirements. Pages 

47-55 In J. E. Cartron, D. M. Finch, tech. eds., Ecology and conservation of the cactus ferruginous pygmy-owl 

in Arizona. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-43.

Cartron, J. E., W. S. Richardson, D. M. Finch, and D. J. Krueper. 2000c. Research needs for the conservation of 

the cactus ferruginous pygmy-owl in Arizona. Pages 65-68 In J. E. Cartron, D. M. Finch, tech. eds., Ecology 

and conservation of the cactus ferruginous pygmy-owl in Arizona. USDA Forest Service, Rocky Mountain 

Research Station, Gen. Tech. Rep. RMRS-GTR-43.

Hall, J. A., P. Comer, A. Gondor, R. Marshall, and S. Weinstein. 2001. Conservation Elements of and a 

Biodiversity Management Framework for the Barry M. Goldwater Range, Arizona. The Nature Conservancy 

of Arizona, Tucson.

Johnson, R. R., J. E. Cartron, L. T. Haight, R. B. Duncan, and K. J. Kingsley. 2003. Cactus ferruginous pygmy-owl 

in Arizona, 1872-1971. The Southwestern Naturalist 48:389-401.

Monson, G. 1998. Ferruginous Pygmy-Owl (Glaucidium brasilianum). Pages 159-161 In R. L. Glinski, ed., The 

Raptors of Arizona. University of Arizona Press, Tucson.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Proudfoot, G. A. and R. R. Johnson. 2000. Ferruginous Pygmy-Owl (Glaucidium brasilianum). In A. Poole, ed., 

The Birds of North America Online. Ithaca: Cornell Lab of Ornithology.

Proudfoot, G. A., R. L. Honeycutt, and R. D. Slack. 2006. Mitochondrial DNA variation and phylogeography of 

the ferruginous pygmy-owl (Glaucidium brasilianum). Conservation Genetics 7:1-12.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

U.S. Fish and Wildlife Service (USFWS). 2003. Cactus ferruginous pygmy-owl (Glaucidium brasilianum 

cactorum) draft recovery plan. Albuquerque, NM. 164 p. + appendices. 

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G., and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 75

Gilded Flicker

(Colaptes chrysoides)

SUMMARY

Gilded flicker was not found to be particularly vulnerable to declines associated with projected climate 

change. Although not widespread at BMGR, expansion of buffelgrass threatens to convert saguaro-dominated 

habitats to grasslands and greatly reduce habitat available for the gilded flicker. Management related to sustaining populations of saguaro will be important to the future of this species. Control of invasive grasses will 

also be important for reducing high intensity fires, preventing conversion to grasslands, and, possibly, sustaining ant populations.

VULNERABILITY Score Uncertainty

Habitat -0.8 43%

Physiology 0.8 50%

Phenology 1.3 50%

Interactions 0.0 40%

Overall 0.8 45%

Introduction

Gilded flickers are endemic to the Sonoran desert. It is one of several species that make up the primary 

excavator guild identified as a conservation element for the biodiversity management framework (Hall and 

others 2001). A wide range of other species use cavities excavated by the gilded flicker. In addition, they are a 

species of greatest conservation need, Tier 1B, in the Arizona State Wildlife Action Plan (AGFD 2006).

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

• CAM plants (succulents and cacti) will be resilient to increasing temperatures (Smith and others 1984)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

-5 0 5
76 USDA Forest Service RMRS-GTR-284. 2012.

Other Threats and Interactions with Climate

Based on Breeding Bird Survey data, gilded flicker populations are considered stable or possibly increasing 

(Moore 1995). Suitable substrates for cavity excavation are thought to be limiting in northern flickers (Moore 

1995), but may be less so for gilded flickers as large cactus are softer and tend to be relatively more abundant 

on the landscape than large snags or trees with large dead limbs. Loss of saguaro is probably the largest threat 

to this species. Although cacti are well-adapted to hot, dry conditions, it may be vulnerable to fires. Cactus 

can survive fires, but mortality rates have been found to be higher after burning. In addition, mortality can be 

increased by higher fire intensities and higher frequencies, which are both induced by exotic grass invasions. 

Buffelgrass (Pennisetum ciliare), in particular, is a major factor in conversion of Sonoran desert habitats to 

grasslands. This conversion is likely to be exacerbated by climate change as more variable rainfall encourages 

build-up of fuels followed by dry conditions conducive to ignitions and fire spread. Even if saguaro can survive 

invasion and fires, seedling survival may be severely reduced (Morales-Romero and Molina-Freaner 2008). 

Buffelgrass may also reduce foraging success of flickers as open ground is reduced. Buffelgrass is not common 

on BMGR, but further introduction and spread from current locations is highly likely.

If European starling eventually expands on BMGR, it could decrease cavity availability, although one study 

suggests that negative impacts of starling on gilded flicker are relatively small (Kerpez and Smith 1990).

Research Needs

Other than threats related to invasive grasses, little information is available on expected response of saguaro 

cactus populations to climate change. Its association with a wide variety of species as well as its iconic status 

makes assessing threats to saguaro a high priority. Gilded flickers may also be a contributor to saguaro 

population dynamics as cavity excavation often results in mortality (McAuliffe and Hendricks 1988). It is 

unknown if climate variables such as drought or rainfall affect the rate of this mortality. Gilded flicker is less 

studied than the similar northern flicker. More information is needed regarding habitat requirements and 

quality, particularly related to foraging. Microclimate of nests may be important in a warming climate, but is 

poorly known in this species. Tendency to orient cavities to the north may indicate some avoidance of sun and 

heat (Zwartjes and Nordell 1998). Little is known about ant response to climate change, which will be critical 

for this species, although some preliminary research indicates numbers of ants may be lower in buffelgrass 

habitats (Franklin 2009). 

Management Implications

Preservation of columnar cactus will be key to sustaining gilded flickers and their ecological role in the region. 

Management to prevent spread of buffelgrass will be critical to preserving desert landscapes with large 

columnar cactus in the future, so current locations should be controlled and introduction points, such as 

roads, should be monitored. 
USDA Forest Service RMRS-GTR-284. 2012. 77

Habitat:	
  Gilded	
  flicker	
  (Colaptes	
  chrysoides)

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?

Lives	
  in	
  Sonoran	
  desertscrub	
  with	
  large	
  cactus	
  (Moore	
  

1995).	
  Although	
  Sonoran	
  desert	
  habitats	
  may	
  expand	
  

northward,	
  no	
  change	
  in	
  area	
  is	
  expected	
  in	
  this	
  region. 0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Large	
  cactus,	
  generally	
  saguaro,	
  is	
  needed	
  for	
  breeding	
  

(Moore	
  1995).	
  Cactus	
  are	
  relatively	
  resilient	
  to	
  warmer	
  

temperatures	
  (but	
  see	
  other	
  threats	
  as	
  related	
  to	
  non-­‐

native	
  grasses). 0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

None	
  known.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

None	
  known.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Highly	
  mobile.

-­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Resident	
  species.

0

Physiology:	
  Gilded	
  flicker	
  (Colaptes	
  chrysoides)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

No	
  data.	
  Widespread	
  across	
  landscapes	
  with	
  a	
  variety	
  of	
  

conditions. 0
78 USDA Forest Service RMRS-GTR-284. 2012.

Physiology:	
  Gilded	
  flicker	
  (Colaptes	
  chrysoides)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

None	
  known.

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

No	
  limitations	
  to	
  activity	
  known.

0

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

No	
  flexible	
  strategies.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic.

0

Phenology:	
  Gilded	
  flicker	
  (Colaptes	
  chrysoides)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Not	
  known,	
  but	
  breeding	
  is	
  likely	
  based	
  on	
  a	
  combination	
  

of	
  internal	
  and	
  external	
  cues.

0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Limited	
  information	
  on	
  timing	
  of	
  breeding,	
  but	
  egg laying	
  

seems	
  to	
  begin	
  in	
  early	
  April	
  (Moore	
  1995).	
  No	
  

information	
  on	
  potential	
  resource	
  peaks	
  or	
  other	
  

variables	
  related	
  to	
  breeding	
  timing. 0

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

No	
  large	
  separation	
  in	
  timing,	
  but	
  also	
  does	
  not	
  adjust	
  

breeding	
  directly	
  to	
  resource	
  timing.

0

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Only	
  one	
  brood	
  per	
  season	
  (Moore	
  1995).

1
USDA Forest Service RMRS-GTR-284. 2012. 79

Biotic	
  Interactions:	
  Gilded	
  flicker	
  (Colaptes	
  chrysoides)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Not	
  closely	
  studied	
  in	
  this	
  species,	
  but	
  red-­‐shafted	
  flicker	
  

eats	
  mostly	
  ants	
  (Moore	
  1995).	
  Probably	
  eats	
  other	
  

ground	
  insects	
  as	
  well	
  as	
  some	
  seeds	
  and	
  fruits	
  (Moore	
  

1995).	
  No	
  studies	
  are	
  available,	
  but	
  overall	
  reduction	
  in	
  

ants	
  is	
  not	
  expected.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Limited	
  information,	
  but	
  small	
  raptors	
  have	
  been	
  

observed	
  depredating	
  flickers.	
  Nestlings	
  are	
  protected	
  to	
  

some	
  extent	
  in	
  cavities,	
  although	
  still	
  vulnerable	
  to	
  snake	
  

and	
  rodent	
  predation.	
  No	
  strong	
  response	
  to	
  nest	
  

predators	
  observed	
  in	
  adults	
  (Moore	
  1995).

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts,	
  although	
  many	
  other	
  species	
  depend	
  on	
  

the	
  cavities	
  it	
  excavates. 0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

None	
  known.

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Sometimes	
  hybridizes	
  with	
  red-­‐shafted	
  flicker,	
  but	
  usually	
  

only	
  in	
  riparian	
  areas	
  (Moore	
  1995).	
  May	
  compete	
  with	
  

European	
  starlings	
  for	
  cavities	
  (Moore	
  1995),	
  but	
  

starlings	
  are	
  currently	
  uncommon	
  at	
  BMGR.

0
80 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s Comprehensive Wildlife Conservation Strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Franklin, K. 2009. The consequences of buffelgrass pasture development for biodiversity in the southern 

Sonoran Desert. Dissertation, University of Arizona, AZ.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Hall, J. A., P. Comer, A. Gondor, R. Marshall, and S. Weinstein. 2001. Conservation Elements of and a 

Biodiversity Management Framework for the Barry M. Goldwater Range, Arizona. The Nature Conservancy 

of Arizona, Tucson.

Kerpez, T. A. and N. S. Smith. 1990. Competition between European starlings and native woodpeckers for nest 

cavities in saguaros. Auk 107:367-375.

McAuliffe, J. R. and P. Hendricks. 1988. Determinants of the vertical distributions of woodpecker nest cavities 

in the Sahuaro cactus. The Condor 90:791-801.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Moore, W. S. 1995. Gilded Flicker (Colaptes chrysoides). In A. Poole. ed., The Birds of North America Online. 

Ithaca: Cornell Lab of Ornithology.

Morales-Romero, D. and F. Molina-Freaner. 2008. Influence of buffelgrass pasture conversion on the 

regeneration and reproduction of the columnar cactus, Pachycereus pecten-aboriginum, in northwestern 

Mexico. Journal of Arid Environments 72:228-237.

Seager, R., T. Mingfang, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Smith, S. D., B. Didden-Zopfy, and P. S. Nobel. 1984. High-temperature responses of North American cacti. 

Ecology 65:643-651.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G., and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.

Zwartjes, P. W. and S. E. Nordell. 1998. Patterns of cavity-entrance orientation by gilded flickers (Colaptes 

chrysoides) in Cardón cactus. The Auk 115: 119-126. 
USDA Forest Service RMRS-GTR-284. 2012. 81

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

Le Conte’s Thrasher

(Toxostoma lecontei)

SUMMARY

Le Conte’s thrasher occupies sparsely vegetated desert washes and dunes subject to very high temperatures. 

The species is well adapted to these conditions and is likely to be resilient to future climate change based on 

many features of its biology, but with climate becoming even more extreme, this species could experience 

population declines associated with physiological limitations. 

VULNERABILITY Score Uncertainty

Habitat -0.8 14%

Physiology 2.5 50%

Phenology -0.4 50%

Interactions 1.0 40%

Overall 2.4 36%

Introduction

Le Conte’s thrasher is associated with extremely dry habitats in the southwestern United States extending into 

parts of Mexico. It is a Federal species of concern and a species of greatest conservation need, Tier 1B, from 

the Arizona State Wildlife Action Plan (AGFD 2006).

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

Major population reductions have mostly been from loss of habitat due to development (Sheppard 1996). 

Off-highway vehicle or other traffic, which can concentrate in washes and sparse vegetation, may degrade 

-5 0 5
82 USDA Forest Service RMRS-GTR-284. 2012.

habitats. Vehicular traffic may increase with climate change. Buffering of climate impacts varies with factors 

such as irrigation and government programs, both of which predict that drought impacts will be less severe 

in the United States as compared to Mexico (Vásquez-León and others 2003). In the absence of alterations 

to immigration policies, increased illegal traffic at the international border is expected. Threats on BMGR 

identified by Arizona Game and Fish Department include ground-based training and heavy equipment 

maneuvers as well as invasive plant species such as Sahara mustard (Brassica tournefortii) and Mediterranean 

grass (Schismus barbatus). Spread of invasive plants is particularly concerning as they can enhance the spread 

of fire through sparsely vegetated lands, which can contribute to degradation of thrasher habitats (Brown 

and Minnich 1986). Climate change is likely to exacerbate spread of these invasive plants and increases in 

fires, in part, through more variable rainfall that results in very wet years followed by very dry years that are 

conducive to large fires.

Research Needs

The breeding bird survey rarely detects Le Conte’s thrasher because surveys occur after most singing has 

ended (Sheppard 1996). Thus, population trends are unknown in this species. Although well adapted to 

desert conditions, there is no information on the species about the effects of droughts or flooding, both of 

which may increase in frequency and/or severity. In addition, competitive interactions with other thrashers 

and relation to habitat variables are not well known but are important for considering future population 

trajectories.

Management Implications

BMGR has few of the known major threats to this species. Management planning should include the 

expectation of increasing threats from vehicles and border security activities. This species generally does not 

occur near water or in areas where other thrasher species dominate. Activities that increase suitability for 

other thrasher species, such as encouraging shrub growth or installing water features, could be detrimental 

to Le Conte’s thrasher. Conversely, some areas may increase in suitability as hotter and drier conditions 

decrease shrub cover in areas where cover is currently too high to attract this species. Monitoring designed to 

detect this species may be warranted in locations with potential impacts. Finally, activity restrictions to avoid 

breeding disturbance should anticipate potential changes in breeding timing.
USDA Forest Service RMRS-GTR-284. 2012. 83

Habitat:	
  Le	
  Conte’s	
  thrasher	
  (Toxostoma	
  lecontei)

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	
  sparsely	
  vegetated	
  desert	
  shrublands	
  and	
  

dunes	
  with	
  low	
  relief	
  topography	
  and	
  sandy	
  soils	
  

(Sheppard	
  1996).	
  Often	
  associated	
  with	
  salt	
  bush,	
  cholla,	
  

and	
  creosote.	
  Areas	
  with	
  greater	
  shrub	
  cover	
  are	
  

generally	
  occupied	
  by	
  other	
  thrasher	
  species	
  (Sheppard	
  

1996).	
  Although	
  areas	
  of	
  sparse	
  vegetation	
  may	
  increase,	
  

suitable	
  soil	
  and	
  topography	
  will	
  not.	
  Overall	
  area	
  is	
  not	
  

expected	
  to	
  change.

0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Nests	
  often	
  in	
  saltbush	
  or	
  cholla	
  cactus.	
  Young	
  may	
  

disperse	
  1-­‐3	
  km	
  from	
  the	
  nest	
  (Sheppard	
  1996).	
  Cholla	
  

cactus	
  and	
  saltbush	
  likely	
  not	
  reduced. 0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Availability	
  of	
  secure	
  night	
  roosts	
  likely	
  important	
  

(Sheppard	
  1996).	
  Roosts	
  and	
  nests	
  in	
  shrubs	
  with	
  dense	
  

foliage	
  or	
  thorny	
  cactus,	
  occasionally	
  in	
  small	
  trees	
  such	
  

as	
  smoke	
  tree	
  (Sheppard	
  1996). 0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Feeds	
  in	
  litter	
  under	
  desert	
  shrubs,	
  but	
  no	
  known	
  

variable	
  associated	
  with	
  better	
  foraging	
  success.	
  It	
  is	
  also	
  

not	
  associated	
  with	
  dense	
  shrub	
  cover,	
  but	
  this	
  may	
  be	
  

because	
  of	
  competitive	
  interactions. 0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Highly	
  mobile.

-­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Not	
  migratory.

0
84 USDA Forest Service RMRS-GTR-284. 2012.

Physiology:	
  Le	
  Conte’s	
  thrasher	
  (Toxostoma	
  lecontei)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Can	
  endure	
  extremely	
  hot	
  surface	
  temperatures	
  

(Sheppard	
  1996).	
  BMGR	
  habitats	
  it	
  occupies	
  are	
  already	
  

very	
  hot.	
  Although	
  well	
  adapted	
  to	
  current	
  conditions,	
  

this	
  species	
  will	
  be	
  exposed	
  to	
  higher	
  temperatures	
  with	
  

little	
  means	
  of	
  escape.	
  May	
  not	
  tolerate	
  further	
  increases.

1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Few	
  nests	
  lost	
  during	
  cold	
  and	
  rainy	
  weather	
  in	
  California	
  

(Sheppard	
  1996).

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Generally	
  inactive	
  during	
  very	
  high	
  temperatures.	
  Limits	
  

activities	
  during	
  hottest	
  part	
  of	
  the	
  day,	
  thus	
  these	
  

periods	
  may	
  increase. 1

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

None	
  known.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic. 0

Phenology:	
  Le	
  Conte’s	
  thrasher	
  (Toxostoma	
  lecontei)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Not	
  known,	
  but	
  likely	
  a	
  combination	
  of	
  internal	
  and	
  

external	
  signals.

0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

No	
  evidence	
  of	
  breeding	
  following	
  summer	
  monsoons.	
  

Probably	
  begin	
  egg	
  laying	
  in	
  mid-­‐February	
  in	
  Arizona	
  

(Sheppard	
  1996)	
  with	
  breeding	
  activities	
  ceasing	
  by	
  June.	
  

Timing	
  may	
  relate	
  to	
  cooler	
  temperatures	
  for	
  vulnerable	
  

young	
  in	
  the	
  nest,	
  thus	
  changes	
  are	
  expected. 1
USDA Forest Service RMRS-GTR-284. 2012. 85

Phenology:	
  Le	
  Conte’s	
  thrasher	
  (Toxostoma	
  lecontei)

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	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Activities	
  are	
  not	
  distant	
  from	
  cues.

0

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Often	
  have	
  two	
  broods	
  per	
  year	
  (Sheppard	
  1996).

-­1

Biotic	
  Interactions:	
  Le	
  Conte’s	
  thrasher	
  (Toxostoma	
  lecontei)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Eats	
  mostly	
  arthropods,	
  although	
  bird	
  eggs,	
  small	
  lizards,	
  

and	
  seeds	
  may	
  also	
  be	
  eaten.	
  Digs	
  for	
  arthropods	
  in	
  litter	
  

and	
  sandy	
  soils.	
  Arthropods	
  occupying	
  litter	
  may	
  be	
  

reduced	
  with	
  drier	
  conditions.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Various	
  predators	
  on	
  nests	
  and	
  one	
  report	
  of	
  an	
  adult	
  

eaten	
  by	
  a	
  prairie	
  falcon	
  (Sheppard	
  1996).	
  Predation	
  is	
  

not	
  likely	
  a	
  major	
  factor	
  in	
  mortality.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

No	
  major	
  diseases	
  known.

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

May	
  compete	
  with	
  other	
  thrashers	
  for	
  habitat	
  and	
  other	
  

birds	
  for	
  nesting	
  sites,	
  but	
  no	
  known	
  effect	
  on	
  

populations.	
  It	
  is	
  possible	
  that	
  this	
  species’	
  adaptations	
  to	
  

extreme	
  conditions	
  will	
  allow	
  it	
  to	
  compete	
  better	
  than	
  

other	
  thrashers	
  in	
  a	
  warming	
  climate,	
  but	
  no	
  available	
  

information	
  on	
  competitive	
  interactions.

0
86 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s Comprehensive Wildlife Conservation Strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

Brown, D. E., and R. A. Minnich. 1986. Fire and changes in creosote bush scrub of the western Sonoran Desert, 

California. American Midland Naturalist 116:411-422.

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Sheppard, J. M. 1996. Le Conte’s Thrasher (Toxostoma lecontei). In A. Poole, ed., The Birds of North America 

Online. Ithaca: Cornell Lab of Ornithology.

Vásquez-León, M., C. T. West, and T. J. Finan. 2003. A comparative assessment of climate vulnerability: 

agriculture and ranching on both sides of the US-Mexico border. Global Environmental Change 13:159-173.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 87

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

Cave Myotis

(Myotis velifer)

SUMMARY

Vulnerability of the cave myotis to population declines is increased under climate change projections. This 

species both migrates and hibernates, two activities associated with timing changes that may lead to mismatches with other events such as insect emergence or suitable breeding conditions. Timing relationships are 

complex, thus eventual outcome in the future is unknown and periodic monitoring is recommended. Roosts 

and open water sources are important elements for this species and should be considered in management 

planning.

VULNERABILITY Score Uncertainty

Habitat -1.1 14%

Physiology -0.2 33%

Phenology 3.8 25%

Interactions 1.0 60%

Overall 2.2 32%

Introduction

The cave myotis occurs on BMGR. It has been a Federal species of concern since 1994. The U.S. Forest Service 

also identifies it as sensitive. Despite being widespread, this species is threatened locally, particularly in 

western portions of its range. 

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

-5 0 5
88 USDA Forest Service RMRS-GTR-284. 2012.

Other Threats and Interactions with Climate

The patchy distribution of this species may be due to its reliance on caves. Recent population declines in 

cave myotis are thought to be related to local habitat loss (BISON-M). Cave myotis, like many other bats, is 

vulnerable to disturbance at roosts, especially at maternity roosts. 

Research Needs

More information on suitable roost sites at a local level is needed as this feature affects species presence. 

Threat of white-nosed fungus for Arizona bats will be important to the species overall, but this disease may 

have limited effects on BMGR. More information is needed to understand the threat of this disease in areas 

outside its known range. Importance of various foraging habitats is not well known. How populations may be 

affected by drought conditions will be critical to predicting climate change effects.

Management Implications

Most cave myotis winter outside of Arizona, and their affinity for cool, moist hibernacula is unlikely to 

increase winter presence in the future. Maternity roost on the other hand may become more critical and 

suitability may be altered over time. Potential roost sites should be checked periodically for species presence. 

Any restrictions that span specific dates intended to protect bats should anticipate changes in timing of bat 

activities. Some monitoring of populations is warranted, as identified phenological vulnerability will have 

an uncertain outcome on populations because interactions with resources are more complex than can be 

evaluated here. Flexibility in migratory behaviors will likely help this species cope with changes on a broad 

scale, but will increase the likelihood of population changes on BMGR and other parts of Arizona.
USDA Forest Service RMRS-GTR-284. 2012. 89

Habitat:	
  Cave	
  myotis	
  (Myotis	
  velifer)

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	
  various	
  desert	
  grassland	
  habitats,	
  but	
  also	
  been	
  

found	
  in	
  pinyon-­‐juniper	
  woodland	
  (BISON-­‐M).	
  Grasslands	
  

may	
  increase	
  with	
  warmer	
  temperatures. -­1

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?

May	
  move	
  to	
  southwestern	
  Mexico	
  for	
  winter	
  (BISON-­‐M).	
  

Assume	
  similar	
  habitats	
  to	
  breeding.

-­1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Roosts	
  in	
  caves	
  and	
  mines,	
  occasionally	
  buildings	
  or	
  

bridges.	
  Often	
  found	
  near	
  the	
  entrance	
  (BISON-­‐M).	
  Caves	
  

and	
  mines	
  will	
  not	
  change	
  with	
  climate. 0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Prefers	
  moist	
  caves	
  for	
  hibernation	
  (NatureServe	
  2009).	
  

In	
  Arizona,	
  winter	
  roosts	
  are	
  in	
  moist	
  caves	
  above	
  6000	
  

ft.	
  Cave	
  availability	
  is	
  not	
  expected	
  to	
  change	
  (but	
  see	
  

Physiology,	
  Question	
  1). 0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

In	
  Arizona,	
  often	
  in	
  vicinity	
  of	
  water	
  sources	
  (Hoffmeister	
  

1986).	
  It	
  is	
  likely	
  that	
  these	
  features	
  are	
  important	
  for	
  

successful	
  foraging	
  and	
  likely	
  to	
  decline	
  with	
  warmer	
  

temperatures. 1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Highly	
  mobile.

-­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Mostly	
  migratory	
  in	
  Arizona	
  although	
  migratory	
  behavior	
  

seems	
  somewhat	
  flexible	
  (NatureServe	
  2009).

1
90 USDA Forest Service RMRS-GTR-284. 2012.

Physiology:	
  Cave	
  myotis	
  (Myotis	
  velifer)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Ranges	
  from	
  the	
  southwestern	
  and	
  central	
  United	
  States

into	
  Central	
  America.	
  Preferred	
  hibernaculum	
  

temperature	
  is	
  8	
  to	
  9°	
  C	
  (Hoffmeister	
  1986).	
  Most	
  bats	
  in	
  

Arizona	
  migrate	
  to	
  hibernate,	
  but	
  those	
  that	
  remain	
  seek	
  

out	
  moist,	
  cool	
  habitats	
  (Hoffmeister	
  1986).	
  Not	
  known	
  if	
  

warmer,	
  drier	
  conditions	
  will	
  exceed	
  thresholds,	
  but	
  they	
  

may.	
  Rely	
  on	
  moist,	
  cool	
  caves	
  for	
  hibernation,	
  which	
  will	
  

warm	
  and	
  lose	
  moisture	
  with	
  increasing	
  temperatures.

1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

None	
  known.	
  Buffered	
  from	
  extremes,	
  to	
  some	
  extent,	
  in	
  

hibernaculum.

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Nocturnal.	
  No	
  expected	
  changes	
  in	
  activity.

0

5.	
  Survival	
  

during

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Sperm	
  is	
  stored	
  over	
  winter,	
  which	
  may	
  maintain	
  

breeding	
  with	
  population	
  and	
  resource	
  fluctuations.	
  In	
  

addition,	
  migratory	
  behavior	
  may	
  be	
  flexible	
  

(NatureServe	
  2009)

-­1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic.

0

	
  	
  	
  	
  	
  	
  	
  	
  	
  

Phenology:	
  Cave	
  myotis	
  (Myotis	
  velifer)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Emergence	
  from	
  roosts	
  is	
  later	
  after	
  sunset	
  in	
  summer	
  

than	
  spring	
  (NatureServe	
  2009)	
  and	
  is	
  apparently	
  

signaled	
  by	
  exterior	
  light	
  levels	
  (Hoffmeister	
  1986).	
  Other	
  

cues	
  not	
  known. 0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Young	
  born	
  mid	
  to	
  late	
  June	
  in	
  Arizona,	
  and	
  females	
  leave	
  

maternity	
  colonies	
  in	
  August	
  (NatureServe	
  2009).	
  

Favorable	
  weather	
  conditions	
  and	
  insect	
  peaks	
  are	
  likely	
  

to	
  change	
  timing. 1
USDA Forest Service RMRS-GTR-284. 2012. 91

Phenology:	
  Cave	
  myotis	
  (Myotis	
  velifer)

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	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Bats	
  in	
  Mexico	
  moved	
  to	
  higher-­‐elevation	
  caves	
  to	
  

hibernate	
  (NatureServe	
  2009),	
  perhaps	
  to	
  take	
  advantage	
  

of	
  colder	
  conditions.	
  Emergence	
  from	
  hibernation	
  and	
  

migration	
  occurs	
  far	
  from	
  insect	
  emergence	
  and	
  feeding	
  

of	
  young. 1

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  reproductive	
  event	
  per	
  year.

1

Biotic	
  Interactions:	
  Cave	
  myotis	
  (Myotis	
  velifer)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Insectivorous	
  and	
  likely	
  opportunistic	
  (NatureServe	
  

2009).	
  Overall,	
  prey	
  levels	
  not	
  expected	
  to	
  change. 0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Likely	
  various.	
  No	
  overall	
  changes	
  in	
  predation	
  expected.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

Hibernates	
  in	
  large	
  clusters	
  and	
  occupies	
  roosts	
  with	
  

other	
  species	
  (NatureServe	
  2009).	
  May	
  have	
  thermal	
  

advantages,	
  but	
  no	
  known	
  changes	
  in	
  clusters.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

Single	
  bat	
  found	
  in	
  May	
  2010	
  with	
  white-­‐nose	
  syndrome	
  

from	
  western	
  Oklahoma	
  was	
  from	
  this	
  species	
  (USFWS	
  

news	
  release:	
  19	
  May	
  2010).	
  This	
  is	
  the	
  first	
  reported	
  

occurrence	
  of	
  the	
  disease	
  in	
  this	
  species	
  and	
  the	
  first	
  from	
  

west	
  of	
  the	
  Mississippi,	
  although	
  no	
  associated	
  mortality	
  

was	
  reported.	
  Transmission	
  may	
  increase	
  if	
  individuals	
  

are	
  restricted	
  to	
  fewer	
  suitable	
  roosts.

1

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Myotis	
  lucifugus	
  occultus	
  may	
  exclude	
  this	
  species	
  from	
  

suitable	
  habitat	
  (BISON-­‐M).	
  No	
  known	
  changes	
  in	
  this	
  

species	
  although	
  likely	
  to	
  be	
  similarly	
  vulnerable. 0
92 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

BISON-M. Biotic Information System of New Mexico [web application]. New Mexico Game and Fish 

Department. Online at: http://www.bison-m.org.

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Liverman, D. M. and K. L. O’Brien. 1991. Global warming and climate change in Mexico. Pages 351-364 In 

Global Environmental Change. Butterworth-Heinemann Ltd.

Hoffmeister, D. F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish Dept. 

602 p.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

NatureServe. 2009. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. 

NatureServe, Arlington, Virginia. Online at: http://www.natureserve.org/explorer. (Accessed: December 2, 

2009)

Seager, R., T. Mingfang, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 93

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

California Leaf-nosed Bat

(Macrotus californicus)

SUMMARY

Overall, California leaf-nosed bats are not expected to be vulnerable to climate-related population declines. 

Phenology, however, is related to a number of predicted changes that could be detrimental to this species. 

Considerable uncertainty surrounds threats related to timing changes, for which the ultimate outcome of 

the population is unknown. Periodic monitoring of populations, including assessment of potential roosts, is 

recommended.

VULNERABILITY Score Uncertainty

Habitat -0.8 14%

Physiology -1.2 33%

Phenology 3.8 50%

Interactions 0.0 60%

Overall 0.5 36%

Introduction

The scientific name has been revised from Macrotus waterhousii californicus. California leaf-nosed bat occurs 

in the Sonoran Desert of North America and is unusual for the inclusion of cactus fruit in its diet and for 

remaining active throughout the year. In addition, it does not migrate. This is the most common bat species 

on BMGR and 11 active roost sites are known (Hall and others 2001). Individuals can have large home ranges, 

and foraging habitat may include BMGR as well as surrounding lands (Dalton 2001). The California leaf-nosed 

bat is a Federal species of concern. It is listed by the Bureau of Land Management as sensitive and by Arizona 

Game and Fish Department as a species of greatest conservation need (AGFD 2006). In addition, this species 

was ranked by the Western Bat Working Group as at a high risk of imperilment and is a conservation element 

for the proposed biodiversity management framework (Hall and others 2001).

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

-5 0 5
94 USDA Forest Service RMRS-GTR-284. 2012.

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

Disturbance at roosts is an important threat to bat species. Pesticide use threatens insect prey (Hall and 

others 2001), but is unlikely to increase with climate change. Disturbance at roosts may be expected to 

increase in some regions along the United States-Mexico border with negative impacts on roosting bats. 

Increased droughts predicted under future climate scenarios will result in failure of agricultural crops and will 

put stress on growing human populations. Buffering of climate impacts varies with factors such as irrigation 

and government programs, both of which predict that drought impacts will be less severe in the United States 

as compared to Mexico (Vásquez-León and others 2003). In the absence of alterations to immigration policies, 

increased illegal traffic at the international border is expected and, subsequently, an increase in human use of 

caves and disturbance at roosts.

Research Needs

The Biodiversity Management Framework for BMGR (Hall and others 2001) notes several research needs for 

California leaf-nosed bat: What are its water requirements and how is it affected by artificial waters? How is 

it affected by variation in rainfall? In addition, because its range is thought to be limited by the availability of 

warm roosts, we also question if there are potential roosts that will become suitable with warmer conditions 

at BMGR and surrounding lands. Habitat quality can be important for maintaining populations, but we found 

no information linking habitat to reproduction or survival. This type of research could suggest strategies for 

successful management of populations.

Management Implications

Although abandoned mines and caves are not expected to be threatened by climate change, their protection 

will remain critical to overall management. In addition, warmer winter temperatures may change suitability 

of roost sites, thus unoccupied sites cannot be assumed to remain so. Potential roost sites should be 

checked periodically for species presence. Some monitoring of populations is warranted, as their identified 

phenological vulnerability will have an uncertain outcome on populations because interactions with resources 

are more complex than can be evaluated here. Although this species will be subject to changes in timing, it 

may prove to be adaptable. Any restrictions that span specific dates intended to protect bats should anticipate 

changes in timing of bat activities.
USDA Forest Service RMRS-GTR-284. 2012. 95

Habitat:	
  California	
  leaf-­nosed	
  bat	
  (Macrotus	
  californicus)

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	
  California	
  leaf-­‐nosed	
  bat	
  lives	
  in	
  various	
  desert	
  scrub	
  

habitats	
  of	
  the	
  Sonoran	
  desert.	
  Xeroriparian	
  areas	
  may	
  be	
  

particularly	
  important	
  for	
  foraging	
  (Hall	
  and	
  others

2001).	
  Sonoran	
  desert	
  habitats	
  are	
  expected	
  to	
  expand	
  

northward	
  in	
  the	
  United	
  States,	
  but	
  BMGR	
  is	
  likely	
  to	
  

remain	
  the	
  same	
  general	
  vegetation	
  type	
  and	
  area.

0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

It	
  uses	
  caves	
  and	
  old	
  mines	
  for	
  day	
  and	
  maternity	
  roosts	
  

(NatureServe	
  2009),	
  as	
  well	
  as	
  bridges,	
  porches,	
  culverts,	
  

caves	
  and	
  other	
  structures	
  to	
  rest	
  at	
  night	
  while	
  foraging.	
  

Needs	
  caves	
  or	
  old	
  mines	
  for	
  maternity	
  roosts.	
  

Availability	
  not	
  expected	
  to	
  change.

0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Needs	
  caves	
  or	
  old	
  mines	
  for	
  day	
  roosts.	
  Also	
  uses	
  various	
  

crevices	
  for	
  night	
  roosts.	
  Availability	
  not	
  expected	
  to	
  

change.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

No	
  known	
  habitat	
  associations	
  with	
  increased	
  

reproduction.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Highly	
  mobile.

-­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Not	
  migratory.

0
96 USDA Forest Service RMRS-GTR-284. 2012.

Physiology:	
  California	
  leaf-­nosed	
  bat	
  (Macrotus	
  californicus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

The	
  leaf-­‐nosed	
  bat	
  is	
  intolerant	
  of	
  cold	
  temperatures,	
  and	
  

although	
  it	
  does	
  not	
  hibernate	
  (NatureServe	
  2009),	
  it

depends	
  on	
  roosts	
  to	
  escape	
  cold	
  temperatures.	
  Roosts	
  

can	
  also	
  be	
  used	
  to	
  escape	
  hot	
  conditions.	
  Thermal	
  

neutral	
  zone	
  is	
  33 °C	
  to	
  40 °C.	
  Warmer	
  winter	
  

temperatures	
  may	
  improve	
  survival.

-­1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Behaviors	
  adapted	
  to	
  desert	
  conditions	
  include	
  roosting	
  

in	
  warm	
  conditions	
  in	
  winter.	
  Exposure	
  to	
  cold	
  

temperatures	
  can	
  cause	
  death.	
  No	
  other	
  information. -­1

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Mostly	
  active	
  around	
  sunrise	
  and	
  sunset.	
  Intolerant	
  of	
  

cold	
  temperatures	
  and	
  roosts	
  during	
  the	
  day,	
  avoiding	
  the	
  

warmest	
  temperatures.	
  Activity	
  period	
  expected	
  to	
  

remain	
  approximately	
  the	
  same	
  (but	
  see	
  Question	
  1). 0

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

No.	
  It	
  is	
  thought	
  that	
  the	
  species	
  is	
  probably	
  able	
  to	
  

tolerate	
  desert	
  conditions	
  because	
  of	
  foraging	
  and	
  

roosting	
  behavior	
  rather	
  than	
  specialized	
  physiology	
  (Bell	
  

and	
  others	
  1986),	
  but	
  there	
  is	
  no	
  recent	
  research	
  on	
  this	
  

topic.	
  

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic.

0

Phenology:	
  California	
  leaf-­nosed	
  bat	
  (Macrotus	
  californicus)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Mating	
  takes	
  place	
  in	
  the	
  fall	
  and	
  young	
  are	
  born	
  in	
  May	
  

and	
  June	
  (NatureServe	
  2009).

This	
  long	
  gestation	
  period	
  is	
  sustained	
  by	
  delayed	
  

embryonic	
  development.	
  Embryonic	
  development	
  is	
  slow	
  

during	
  winter	
  then	
  speeds	
  up.	
  No	
  known	
  relation	
  of	
  cues	
  

to	
  temperature.

0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Young	
  are	
  born	
  in	
  the	
  spring,	
  likely	
  corresponding	
  to	
  

favorable	
  temperatures	
  and/or	
  emergence	
  of	
  insects.	
  

Emergence	
  of	
  moths	
  and	
  cicadas	
  is	
  related	
  to	
  temperature	
  

and	
  prone	
  to	
  timing	
  change. 1

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

Mating	
  occurs	
  far	
  in	
  advance	
  of	
  birth	
  of	
  young.	
  The	
  trigger	
  

or	
  mechanism	
  behind	
  this	
  increase	
  in	
  development	
  rate	
  

could	
  be	
  temperature	
  related. 1
USDA Forest Service RMRS-GTR-284. 2012. 97

Phenology:	
  California	
  leaf-­nosed	
  bat	
  (Macrotus	
  californicus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  reproductive	
  event	
  per	
  year.

1

Biotic	
  Interactions:	
  California	
  leaf-­nosed	
  bat	
  (Macrotus	
  californicus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Primary	
  prey	
  are	
  flying	
  insects	
  that	
  are	
  active	
  at	
  night	
  

such	
  as	
  moths,	
  beetles,	
  and	
  grasshoppers	
  (NatureServe	
  

2009).	
  No	
  projections	
  known	
  related	
  to	
  changes	
  in	
  

nocturnal	
  insects.	
  Cicadas	
  are	
  taken	
  and	
  are	
  resilient	
  to

high	
  temperatures	
  (Heath	
  and	
  others	
  1970).	
  Occasionally,	
  

leaf-­‐nosed	
  bats	
  also	
  feed	
  on	
  cactus	
  fruits.	
  Foraging	
  may	
  be	
  

concentrated	
  around	
  xeroriparian	
  corridors,	
  areas	
  with	
  

high	
  densities	
  of	
  saguaro	
  cactus,	
  and	
  tinajas	
  (Hall	
  and	
  

others	
  2001).	
  Unknown	
  changes	
  in	
  abundance	
  of	
  prey.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Probably	
  various,	
  but	
  no	
  specific	
  information.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts. California	
  leaf-­‐nosed	
  bats	
  will	
  roost	
  with	
  

other	
  bat	
  species,	
  but	
  also	
  in	
  single	
  species	
  aggregates	
  

(Arita	
  1993).

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

Species	
  is	
  susceptible	
  to	
  rabies.	
  Rabies	
  can	
  result	
  in	
  

mortality,	
  but	
  is	
  generally	
  not	
  considered	
  a	
  threat	
  to	
  bat	
  

colonies	
  (Gillette	
  and	
  Kimbrough	
  1970).	
  Another	
  

emerging	
  bat	
  disease	
  is	
  white-­‐nose	
  syndrome,	
  which	
  has	
  

been	
  killing	
  large	
  numbers	
  of	
  roosting	
  bats	
  in	
  

northeastern	
  North	
  America.	
  So	
  far,	
  it	
  appears	
  this	
  

disease	
  only	
  threatens	
  hibernating	
  species	
  and	
  is	
  

associated	
  with	
  cold	
  conditions	
  (Blehert	
  and	
  others

2008).	
  California	
  leaf-­‐nosed	
  bats	
  have	
  neither	
  of	
  these	
  

risk	
  factors.	
  

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

No	
  known	
  competitors.

0
98 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s Comprehensive Wildlife Conservation Strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Arita, H. T. 1993. Conservation biology of the cave bats of Mexico. Journal of Mammalogy 74:693-702.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

Bell, G. P., G. A. Bartholomew, and K. A. Nagy. 1986. The roles of energetics, water economy, foraging behavior, 

and geothermal refugia in the distribution of the bat, Macrotus californicus. Journal of Comparative 

Physiology 156:441-450.

Cockrum, E. L. and S. P. Cross. 1964. Time of bat activity over water holes. Journal of Mammalogy 45:635-636.

Environment and Natural Resources Division. December 2006. Programmic Biological Assessment for Ongoing 

and Future Military Operations and Activities at Fort Huachuca, Arizona.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Gillette, D. D. and J. D. Kimbrough. 1970. Chiropteran Mortality. In B. Slaugher and D. Walton, eds. About Bats. 

Southern Methodist University Press, Dallas, TX.

Hall, J. A., P. Comer, A. Gondor, R. Marshall, and S. Weinstein. 2001. Conservation Elements of and a 

Biodiversity Management Framework for the Barry M. Goldwater Range, Arizona. The Nature Conservancy 

of Arizona, Tucson.

Heath, J. E. and P. J. Wilkin. 1970. Temperature responses of the desert cicada, Diceroprocta apache

(Homoptera, Cicadidae). Physiological Zoology 43:145-154.

McLaughlin, S. E. and J. P. Bowers. 1982. Effects of wildfire on a Sonoran Desert plant community. Ecology 

63:246-248.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: Mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

NatureServe. 2009. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. 

NatureServe, Arlington, Virginia. Online at: http://www.natureserve.org/explorer. (Accessed: December 2, 

2009)

Pinkava, D. J. 1999. Cactaceae cactus family, part three, Cylindropuntia. Journal of the Arizona-Nevada 

Academy of Science 32:32-47.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Vásquez-León, M., C. T. West, and T. J. Finan. 2003. A comparative assessment of climate vulnerability: 

agriculture and ranching on both sides of the US-Mexico border. Global Environmental Change 13:159-173.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 99

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

Mexican Long-tongued Bat

(Choeronycteris mexicana)

SUMMARY

Populations of Mexican long-tongued bats that occur in Arizona are females that migrate from Mexico to maternity colonies. Like the lesser long-nosed bat, this species is vulnerable to changes in temperature that will 

affect habitats and, in particular, flowering cacti and agave. Conversely, warmer winters will make conditions 

more favorable to year-round presence in the future. Fire, fuels, and invasive grass species management will 

be critical to this species.

VULNERABILITY Score Uncertainty

Habitat 1.3 14%

Physiology 0.7 67%

Phenology 0.8 0%

Interactions 1.0 20%

Overall 4.1 27%

Introduction

Mexican long-tongued bat is a USFWS species of concern, a Forest Service sensitive species, and a species 

of greatest conservation need, Tier 1C, in Arizona State Wildlife Action Plan (AGFD 2006). Many aspects of 

this species’ biology are not well known, but populations may be declining in Arizona (BISON-M). Individuals 

recorded in Arizona have been mostly females, but there are a few records of males in the United States (Balin 

2009). Arizona populations are largely maternal roosting colonies, although it is rare to see more than 25 

individuals together (Joaquίn and others 1987). Similar in ecology to the lesser long-nosed bat, this species is 

nectivarous and migrates from U.S. locations to Mexico where it is generally a year-round resident. At the time 

of this report, there was no confirmation of this species on BMGR, but suitable habitat is present.

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

-5 0 5
100 USDA Forest Service RMRS-GTR-284. 2012.

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• CAM plants (succulents and cacti) will be resilient to increasing temperatures (Smith and others 1984)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

Many historic locations for this species remain occupied in Arizona (Cryan and Bogan 2003). Thus, although 

rare, populations in Arizona may be relatively stable. Mexican long-tongued bat, however, is threatened by a 

number of factors expected to be exacerbated by future climate change.

Like most bats, Mexican long-tongued bat is vulnerable to roost disturbance (NatureServe 2009). Roost 

protection is complicated by disturbance at roost sites. It is unknown if this species is sensitive to gating 

like lesser long-nosed bats. Climate change will potentially increase roost disturbance by illegal immigrants. 

Increased droughts predicted under future climate scenarios will result in failure of agricultural crops and put 

stress on growing human populations. Buffering of climate impacts varies with factors such as irrigation and 

government programs, both of which predict that drought impacts will be less severe in the United States as 

compared to Mexico (Vásquez-León and others 2003). In the absence of alterations to immigration policies, 

increased illegal traffic at the international border is expected. 

The greatest threat to bat foraging areas at a landscape level is the likely expansion of invasive grasses and the 

concurrent increase in fire occurrence with subsequent reduction in agaves and cacti. Buffelgrass (Pennisetum 

ciliare), in addition to other invasive plants, is rapidly expanding and is becoming increasingly problematic 

in the Sonoran Desert (Burquez-Montijo and others 2002). It was, and continues to be, introduced in the 

Sonoran desert to enhance livestock grazing with almost the entire Sonoran Desert ecosystem prone to 

buffelgrass invasion (Arriaga and others 2004). Fires occur more frequently in the dry biomass created, 

and burning encourages more buffelgrass (Arriaga and others 2004). The invasion of African grasses and 

accompanying alteration of fire regimes will be exacerbated by climate change. Although currently limited 

in distribution at BMGR, African grasses will not likely be limited by climate changes in this region, and any 

increase in fire and other disturbances will favor grasses at the expense of species prone to fire mortality such 

as cacti and agaves. 

Research Needs

Critical resource requirements are not well known in this species, making effective management difficult. 

We found little information on the specific requirements for roosting locations, which will be important to 

identifying critical roost resources. Important foraging plants are also not well known in this species, although 

Mexican long-tongued bats are assumed to select a broader range of plants than lesser long-nosed bats. More 

study is needed to understand flexible, migratory behaviors in this species. Depending on how this flexibility 

occurs in populations or individuals, changes in migration might be expected to occur regularly resulting in 

observed population fluctuations at isolated locations.

Management Implications

Buffelgrass has only been found along roadways in limited locations at BMGR but spread is almost inevitable 

along these corridors. Drought and very arid regions of BMGR will limit expansion to some extent. The 

potential for increasing impacts from invasive African grasses and increasing fires warrants consideration in 

management planning and implementation of preventative actions. It will also be a major factor affecting 

populations while on wintering grounds in Mexico. Management related to post-fire rehabilitation should 

also include actions that encourage agaves and cacti in suitable areas. Cactus flowering timing also depends 
USDA Forest Service RMRS-GTR-284. 2012. 101

on size, thus management that encourages diversity of size could be used to extend flowering period 

(Bustamante and Búrquez 2008).

Measures to protect bat species in general, such as closure of mines and caves, will benefit this species. 

Timing changes in bat arrival and presence at BMGR related to climate change should be anticipated, and time 

restrictions on activities that span specific dates should be altered accordingly. In addition, identification and 

monitoring of suitable caves or mines is warranted as conditions become more favorable for these bats. 
102 USDA Forest Service RMRS-GTR-284. 2012.

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?

In	
  the	
  United	
  States,	
  Mexican	
  long-­‐tongued	
  bat	
  breeds

along	
  the	
  border	
  region	
  with	
  Mexico.	
  In	
  Arizona,	
  this	
  

species	
  inhabits	
  primarily	
  the	
  oak-­‐pine	
  belt	
  at	
  elevations	
  

ranging	
  from	
  4000	
  to	
  6000	
  ft	
  as	
  well	
  as	
  saguaro-­‐palo-­‐

verde	
  desertscrub	
  (BISON-­‐M).	
  Additionally,	
  it	
  is	
  often	
  

associated	
  with	
  Madrean	
  evergreen	
  woodlands	
  and	
  semi-­‐

desert	
  grasslands	
  with	
  agave	
  species	
  in	
  this	
  region	
  (Cryan	
  

and	
  Bogan	
  2003).	
  Increasing	
  fires	
  and	
  invasive	
  grasses	
  

will	
  likely	
  reduce	
  pine-­‐oak	
  habitats	
  along	
  with	
  upward	
  

elevational	
  shifts.

1

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?

Individuals	
  that	
  breed	
  in	
  the	
  United	
  States	
  are	
  mostly

females	
  and,	
  after	
  breeding,	
  migrate	
  to	
  Mexico	
  for	
  the	
  

winter	
  (Joaquίn	
  and	
  others	
  1987;	
  BISON-­‐M).	
  Central	
  

Mexico	
  vegetation	
  associations	
  include	
  desert	
  scrub	
  and	
  

mixed	
  pine-­‐oak	
  forest	
  (NatureServe,	
  2009).	
  These	
  

vegetation	
  types	
  are	
  expected	
  to	
  be	
  exposed	
  to	
  increased	
  

fires	
  and	
  invasive	
  grasses.

1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Maternity	
  roosts	
  are	
  required	
  and	
  are	
  usually	
  found	
  in	
  

caves	
  or	
  abandoned	
  mines	
  (NatureServe	
  2009).	
  

Availability	
  not	
  expected	
  to	
  change. 0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Day	
  and	
  night	
  roosts	
  are	
  also	
  required	
  for	
  non-­‐breeding	
  

individuals	
  (BISON-­‐M).	
  Roost	
  locations	
  include	
  buildings,	
  

rock	
  fissures,	
  and	
  caves	
  (NatureServe	
  2009).	
  Availability	
  

not	
  expected	
  to	
  change. 0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

None	
  known.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Highly	
  mobile,	
  although	
  males	
  and	
  females	
  have	
  different	
  

dispersal	
  patterns. -­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Populations	
  in	
  Arizona	
  are	
  migratory.

1
USDA Forest Service RMRS-GTR-284. 2012. 103

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?

Limited	
  information.	
  Range	
  extends	
  from	
  southern	
  

California,	
  Arizona,	
  and	
  southwest	
  New	
  Mexico	
  

southward	
  into	
  central	
  Mexico	
  and	
  into	
  Central	
  America	
  

(Joaquίn	
  and	
  others	
  1987).	
  This	
  species	
  is	
  limited	
  in	
  

occupation	
  of	
  Arizona	
  habitats	
  because	
  of	
  cold	
  limitations.	
  

Warmer	
  temperatures	
  may	
  create	
  more	
  favorable	
  

conditions.

-­1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Fire	
  or	
  other	
  extreme	
  weather	
  is	
  unlikely	
  to	
  result	
  in	
  

direct	
  mortality.	
  Roosts	
  are	
  somewhat	
  protected	
  from	
  

disturbance,	
  although	
  there	
  have	
  been	
  incidences	
  of	
  

flooding	
  of	
  roosts	
  and	
  bat	
  mortality	
  in	
  some	
  species.	
  

Heavy	
  rainfall	
  events,	
  which	
  are	
  expected	
  to	
  increase,	
  are	
  

associated	
  with	
  mortality	
  in	
  some	
  species	
  and	
  have	
  been	
  

documented	
  at	
  Carlsbad	
  Caverns,	
  New	
  Mexico.	
  Flood	
  risk	
  

at	
  specific	
  BMGR	
  roosts	
  is	
  unknown.	
  

1

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species

expected	
  to	
  change?

Active	
  at	
  night.	
  No	
  information	
  on	
  limitations	
  to	
  foraging	
  

on	
  hot	
  nights.	
  Rests	
  part	
  of	
  the	
  night	
  in	
  night	
  roosts.	
  

Activity	
  periods	
  will	
  probably	
  not	
  be	
  reduced	
  or	
  

increased. 0

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Seems	
  to	
  have	
  somewhat	
  flexible	
  migration.	
  Not	
  known	
  if	
  

this	
  flexibility	
  is	
  possessed	
  within	
  individuals	
  or	
  within	
  

certain	
  populations.	
  All	
  bats	
  in	
  Arizona	
  are	
  migratory, and	
  

it	
  is	
  not	
  known	
  if	
  they	
  would	
  not	
  migrate	
  if	
  flowering	
  

failed.	
  Possible,	
  but	
  too	
  little	
  information	
  to	
  assume	
  

flexibility.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic. 0

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	
  (e.g.,,

hibernation,	
  

migration,	
  breeding)?	
  

Cues	
  are	
  likely	
  a	
  combination	
  of	
  internal	
  and	
  external	
  

signals.	
  Does	
  not	
  hibernate.

0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Births	
  in	
  Arizona	
  occur	
  between	
  mid June	
  and	
  early	
  July	
  

(BISON-­‐M)	
  and	
  may	
  be	
  timed	
  to	
  peak	
  flowering.	
  Earlier	
  

flowering	
  has	
  been	
  documented	
  in	
  many	
  Sonoran	
  Desert	
  

plant	
  species,	
  including	
  columnar	
  cacti	
  and	
  agave	
  

(Bustamante	
  and	
  Búrquez	
  2008). 1
104 USDA Forest Service RMRS-GTR-284. 2012.

Phenology:	
  Mexican	
  long-­tongued	
  bat	
  (Choeronycteris	
  mexicana)

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	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

These	
  bats	
  follow	
  the	
  sequential	
  flowering	
  of	
  agave,	
  

saguaro,	
  ocotillo,	
  palo	
  verde,	
  and	
  prickly	
  pear	
  cactus	
  

(Fleming	
  1988).	
  Migrations	
  are	
  described	
  as	
  following	
  the	
  

sequential	
  flowering	
  of	
  various	
  cacti	
  species	
  (Fleming	
  

1988). -­1

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  reproductive	
  event	
  per	
  year.

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?

Consume	
  nectar	
  and	
  pollen	
  from	
  flowering	
  plants,	
  such	
  as	
  

agaves	
  and	
  saguaro,	
  and	
  may	
  supplement	
  their	
  diet	
  with	
  

cactus	
  fruit	
  and	
  insects	
  (BISON-­‐M).	
  Mexican	
  long-­‐tongued	
  

bats	
  may	
  be	
  able	
  to	
  feed	
  on	
  a	
  greater	
  variety	
  of	
  flowers	
  

than	
  lesser	
  long-­‐nosed	
  bats	
  because	
  of	
  their	
  longer	
  

tongues	
  (BISON-­‐M).	
  In	
  Arizona,	
  large	
  numbers	
  of	
  bats	
  are	
  

thought	
  to	
  rely	
  on	
  hummingbird	
  feeders	
  before	
  and	
  after	
  

agave	
  flowering	
  season	
  (BISON-­‐M).	
  Flowering	
  and,	
  thus,

nectar	
  availability	
  generally	
  decreases	
  under	
  dry	
  

conditions.	
  In	
  addition,	
  more	
  variable	
  rainfall	
  may	
  

increase	
  variability	
  in	
  flowering.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Limited	
  information	
  on	
  predators,	
  but	
  known	
  to	
  be	
  

preyed	
  upon	
  by	
  owls	
  (Joaquίn	
  and	
  others	
  1987).	
  

Predation	
  rates	
  not	
  likely	
  to	
  change.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.	
  

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

Rabies	
  has	
  been	
  found	
  in	
  this	
  species	
  in	
  Mexico	
  and,	
  while	
  

it	
  can	
  result	
  in	
  bat	
  mortality,	
  rabies	
  is	
  not	
  common	
  and	
  

generally	
  not	
  considered	
  to	
  be	
  a	
  significant	
  threat	
  to	
  bat	
  

populations	
  (Gillette	
  and	
  Kimbrough	
  1970).	
  Another	
  

emerging	
  bat	
  disease	
  is	
  white-­‐nose	
  syndrome,	
  which	
  has	
  

been	
  killing	
  large	
  numbers	
  of	
  roosting	
  bats	
  in	
  

northeastern	
  North	
  America.	
  So	
  far,	
  it	
  appears	
  this	
  

disease	
  only	
  threatens	
  hibernating	
  species	
  and	
  is	
  

associated	
  with	
  cold	
  conditions	
  (Blehert	
  and	
  others

2008).	
  Mexican	
  long-­‐tongued	
  bats	
  have	
  neither	
  of	
  these	
  

risk	
  factors.

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Other	
  nocturnal	
  nectarivores	
  that	
  exploit	
  these	
  nectar	
  

resources	
  are	
  much	
  smaller	
  (e.g.,	
  moths	
  and	
  birds),	
  so	
  

probably	
  little	
  competition.	
  Could	
  be	
  competition	
  with	
  

other	
  bats,	
  but	
  lesser	
  long-­‐nosed	
  bat	
  probably	
  exploits	
  

additional	
  flower	
  resources	
  with	
  its	
  longer	
  tongue.	
  

Expected	
  to	
  be	
  similarly	
  affected	
  by	
  climate	
  change.

0
USDA Forest Service RMRS-GTR-284. 2012. 105

Literature Cited

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s Comprehensive Wildlife Conservation Strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Arita, H. T. 1993. Conservation biology of the cave bats of Mexico. Journal of Mammalogy 74:693-702.

Arriaga, L., A. Castellanos, V. E. Moreno, and J. Alarcon. 2004. Potential ecological distribution of alien invasive 

species and risk assessment: a case study of buffel grass in arid regions of Mexico. Conservation Biology 

18:1504-1514.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257. 

Balin, 2009. Mexican long-tongued bat (Choeronycteris mexicana) in El Paso, Texas. Southwestern Naturalist 

54:225-226.

BISON-M. Biotic Information System of New Mexico. New Mexico Game and Fish Department. Online at: 

http://www.bison-m.org.

Blehert, D. S., A. C. Hicks, M. Behr, C. U. Meteyer, B. M. Berlowski-Zier, and E. L. Buckles. 2008. Bat white-nose 

syndrome: an emerging fungal pathogen? SciencExpress. Published online October 30, 2008; 10.1123/

science.11638.

Burquez-Montijo, A., M. Miller, and A. Martinez-Yrizar. 2002. Mexican grasslands, thornscrub, and the 

transformation of the Sonoran Desert by invasive exotic buffelgrass. Pages 126-146 In B. Tellman, ed., 

Arizona-Sonoran Desert Museum Studies in Natural History, Tucson, AZ.

Bustamante, E. and A. Búrquez. 2008. Effects of plant size and weather on the flowering phenology of the 

organ pipe cactus (Stenocereus thurberi). 102:1019-30.

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. 

Environment and Natural Resources Division. December 2006. Programmic Biological Assessment for Ongoing 

and Future Military Operations and Activities at Fort Huachuca, Arizona. 

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Fleming, T. H. 1988. Evolution and ecology of phyllostomid bats. Pages 1-34 In The Short-Tailed Bat: A Study in 

Plant-Animal Interactions. The University of Chicago Press, Chicago.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Gillette, D. D. and J. D. Kimbrough. 1970. Chiropteran Mortality. In B. Slaugher and D. Walton, eds., About Bats. 

Southern Methodist University Press, Dallas, TX.

Graham, E. A. and P. S. Nobel. 1996. Long term effects of a doubled atomospheric CO2 concentration on the 

CAM species Agave deserti. Journal of Experimental Botany 47:61-69.

Joaquίn, A-C, R. R. Hollander, and J. K. Jones, Jr. Choeronycteris mexicana. Mammalian Species 291:1-5.

Liverman, D. M. and K. L. O’Brien. 1991. Global warming and climate change in Mexico. Pages 351-364 In 

Global Environmental Change. Butterworth-Heinemann Ltd.

McLaughlin, S. E. and J. P. Bowers. 1982. Effects of wildfire on a Sonoran Desert plant community. Ecology 

63:246-248.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

NatureServe. 2009. NatureServe Explorer: an online encyclopedia of life [web application]. Version 7.1. 

NatureServe, Arlington, Virginia. Online at: http://www.natureserve.org/explorer. (Accessed: July 12, 2010)
106 USDA Forest Service RMRS-GTR-284. 2012.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Smith, S. D., B. Didden-Zopfy, and P. S. Nobel. 1984. High-temperature responses of North American cacti. 

Ecology 65:643-651.

Vásquez-León, M., C. T. West, and T. J. Finan. 2003. A comparative assessment of climate vulnerability: 

agriculture and ranching on both sides of the US-Mexico border. Global Environmental Change 13:159-173.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
USDA Forest Service RMRS-GTR-284. 2012. 107

Lesser Long-nosed Bat

(Leptonycteris yerbabuenae)

SUMMARY

Lesser long-nosed bat was assessed as moderately vulnerable to declines related to global climate change. 

Vulnerability is increased by reliance on quantity and timing of flowering of a limited number of plant species, while resilience is incurred by flexible migratory behaviors and probable resilience of forage plant populations to increasing temperatures. Unfortunately, changes in climate are expected to exacerbate current 

threats, making conservation of this species more challenging. Although few individuals of this species have 

been recorded at BMGR, current critical threats of roost disturbance and loss of foraging habitats will likely be 

increased through growing international border activity as well as the interactive effects of fire occurrence and 

non-native invasive grasses. 

VULNERABILITY Score Uncertainty

Habitat -0.2 14%

Physiology 0.7 33%

Phenology 0.8 0%

Interactions 1.0 0%

Overall 2.2 14%

Introduction

Lesser long-nosed bat was listed in 1988 as endangered under the subspecies Leptonycteris curasoae 

yerbabuenae. Originally, they were listed as Leptonycteris sanborni (Sanborn’s bat), but was also sometimes 

identified as Leptonycteris curasoae. Numbers of lesser long-nosed bats have increased in recent years or 

may not have been as low as reported when first listed. The five-year review by USFWS suggested downlisting 

the status to threatened because current populations appear to be stable or increasing, but the review also 

acknowledged that threats still exist, particularly for roosts, impacts in Mexico, and vulnerability of foraging 

plants to fire and invasive species (USFWS 2005). Populations are migratory from Mexico where there are also 

resident populations of this species (USFWS 2005). In this account, we focus on the migratory group that lives 

in Arizona and southern Sonora.

Only 3 maternity roosts and approximately 40 roosts overall are known in the United States (USFWS 2005). 

At BMGR, no roosting colonies have been found, and there have been few lesser long-nosed bats recorded, 

although the Sand Tank Mountains are thought to have good foraging and roosting habitats (Hall and others 

2001). There are large maternity colonies in surrounding areas such as Cabeza Prieta National Wildlife Refuge, 

Organ Pipe Cactus National Monument, and the Tohono O’odham Reservation. BMGR may serve as foraging 

habitat for migrating individuals.

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

-5 0 5
108 USDA Forest Service RMRS-GTR-284. 2012.

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• CAM plants (succulents and cacti) will be resilient to increasing temperatures (Smith and others 1984)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

There are many known threats to this species. Suitable concentrations of food plants and day roosts are 

considered critical (Fleming 1995). The USFWS five-year review identified illegal border activity, fire, and 

drought as important threats to roosts or foraging habitats (USFWS 2005). The review further noted that 

grazing, tequila harvesting, and prescribed fire are probably not substantial threats in the United States. 

(USFWS 2005). Urban development, wind farms, and changing fire regimes are additional potential threats 

that have yet to be addressed as part of recovery planning. Climate change impacts were not specifically 

addressed in the review.

Roost protection is complicated by disturbance at roost sites. There are also issues with gating cave and mine 

entrances, including gate vandalism and bat avoidance after gating (USFWS 2005). Lesser long-nosed bats 

may be sensitive to gate construction and configuration. Climate change will also potentially increase roost 

disturbance by illegal immigrants. Increased droughts predicted under future climate scenarios will result 

in failure of agricultural crops and stress growing human populations. Buffering of climate impacts varies 

with factors such as irrigation and government programs, both of which predict that drought impacts will be 

less severe in the United States as compared to Mexico (Vásquez-León and others 2003). In the absence of 

alterations to immigration policies, increased illegal traffic at the international border is expected.

Climate change may create timing mismatches between species and resources. A number of observations 

and studies have found there is not close synchrony between lesser long-nosed bat arrival in Arizona and 

New Mexico with the peak of agave flowering (Fleming and others 2001; Scott 2004). Bat arrival late in agave 

blooming may allow flexibility in earlier bat arrival, although advancement of blooming may be problematic 

if bat migration cannot advance equally (see Table A1). Observations of timing, however, are limited and 

generally occurred only over short time periods, so it is reasonable to assume there is annual variability of 

arrival, flowering, and, therefore, the synchrony of these events.

Timing and the extent of synchronicity in flowering of forage species along migratory routes will affect 

population sizes and arrival dates in Arizona, at least as observed from a single location such as BMGR. 

Migratory and non-migratory demes probably make the species more resilient as a whole to climate and 

resource variability. More critical to populations is failure of flowering, particularly if synchronous across their 

range. In one study, monsoons were found to be generally asynchronous between northern Mexico and the 
USDA Forest Service RMRS-GTR-284. 2012. 109

Sources:	
  

a

	
  Fleming	
  2001	
  (1995-­‐1996,	
  Bahia	
  de	
  Kino,	
  Sonora,	
  MX)

b

	
  Fleming	
  1993	
  (?,	
  numerous	
  locations,	
  MX)

c	
  Horner	
  and	
  others	
  1998	
  (1989-­‐1990,	
  Bahia	
  de	
  Kino,	
  Sonora,	
  MX)

d	
  Fleming	
  2001	
  (1997,	
  Organ	
  Pipe,	
  AZ) e	
  Scott	
  2004	
  (1997,	
  Chiricahuas,	
  AZ)

f	
  Slauson	
  2000	
  (1993-­‐1994,	
  southern	
  AZ) g	
  Cockrum	
  1991	
  (13	
  year	
  average,	
  Chiricahua	
  Mountains,	
  AZ)

h	
  Ober	
  and	
  Steidl	
  2004	
  (1999	
  Huachuca	
  Mountains,	
  AZ) i

Beatty	
  1955	
  (?,	
  AZ)

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Saguaro 

blooming 

MX

?a 1-30a latea

Agave 

blooming 

MX

1-31b 1-30b 1-31b 1-30b 1-31b 1-midb

LLNB 

presence 

MX

?a

?c

1-30a

1-30c

1-mid?a

1-endc

Saguaro 

blooming 

AZ/NM

lated 1-31d earlyd

Agave 

blooming 

AZ/NM

18-30e

latef

1-31e

1-31f

1-31e

1-31f

1-12e

1-30f earlyf

LLNB 

arrival 

AZ/NM

14-?i

24-31e

~9g

2-7h

1-12e

Table A1. Event timing and lesser long-nosed bat (LLNB) populations in northern Mexico (MX), southern 

Arizona (AZ), and New Mexico (NM). Dates of recorded events are listed by month with sources, including 

recording year and location of observation, noted below.
110 USDA Forest Service RMRS-GTR-284. 2012.

southwestern United States (Comrie and Glenn 1998), thus adequate resources should be available within 

some part of the range. Monsoon behavior under current climate projections, however, is unpredictable at 

this point and past patterns may not extend into the future. Interestingly, there is some evidence that seed 

set of agaves was higher in the past (Howell and Roth 1981), a factor that is likely affected by climate. It is also 

possible that there was greater synchronicity between bat arrival and flowering in the past.

BMGR has saguaro (Cereus giganteus) and other large cactus species as well as desert agave (Agave deserti). 

Lesser long-nosed bats use clumped concentrations of agaves rather than isolated individuals (Ober and Steidl 

2004). The greatest threat to bat foraging areas at a landscape level is the likely expansion of invasive grasses 

and the concurrent increase in fire occurrence with subsequent reduction in agaves and cacti. Buffelgrass 

(Pennisetum ciliare), in addition to the already common red brome (Bromus rubens), is rapidly expanding and 

is becoming increasingly problematic in the Sonoran Desert. It was, and continues to be, introduced in the 

Sonoran Desert to enhance livestock grazing although almost the entire Sonoran Desert ecosystem is prone to 

buffelgrass invasion (Arriaga and others 2004). The invasion of African grasses and accompanying alteration of 

fire regimes will be exacerbated by climate change. African grasses will likely not be limited by climate changes 

in this region, and any increase in fire and other disturbances will favor further conversion to grasslands.

Part of the U.S. strategy to combat increasing CO2 levels is to promote alternative energy sources. Wind farms 

are increasingly being proposed in many areas, including the Southwest. Wind turbines are known to kill bats 

(Arnett and others 2008), but to date, there has been no documented mortality for lesser long-nosed bat. 

Potential for impacts will be, at least in part, related to wind farm locations and their proximity to bat roosts, 

migratory routes, or foraging areas.

Research Needs

Several areas of deficient information on lesser long-nosed bat were identified in the USFWS five-year review, 

including: bat response to gates and other methods aimed at preventing roost disturbance, wind farm 

impacts, overall population size, and long-term effects of fire on foraging resources (USFWS 2005).

Additional research needs identified by this assessment follow. Of particular interest is how fluctuations in 

flowering timing alter bat migratory behavior and timing of arrival throughout the U.S. range and, in particular, 

BMGR. In addition, little is known about how climate variability may affect flowering variability, particularly 

across latitudes where the bat occurs, and if variables related to flowering influence bat survival. Information 

on the interactions among warming climate, fire, and expansion of invasive grasses will be valuable in 

identifying effective management actions. Information is also needed on bat mortality and wind turbines, as 

well as on management options that reduce populations of African grasses and probability of spread.

Management Implications

Lesser long-nosed bat only spends a portion of the year on BMGR. Activities in Mexico, where this species 

winters, will affect populations that migrate to Arizona.

Presence of the lesser long-nosed bat at BMGR is tied to the birth of young at nearby maternity caves and the 

blooming of columnar cactus and agave. The potential for increasing impacts from invasive African grasses 

and increasing fires on cacti and agaves warrants consideration in management planning and implementation 

of preventative actions. Management related to post-fire rehabilitation should also plan for and implement 

actions that encourage cacti and agaves while discouraging further spread of invasive plants. Encouragement 

of diverse cactus size may also help to extend the flowering season (Bustamante and Búrquez 2008).
USDA Forest Service RMRS-GTR-284. 2012. 111

Anticipated changes in bat arrival and use of BMGR with climate change indicates the need to reevaluate any 

time restrictions on activities that span specific dates meant to protect bats. Gates at roosts also should be 

evaluated as this species is sensitive to their configuration. Any potential roosts on BMGR should be identified 

and monitored. 
112 USDA Forest Service RMRS-GTR-284. 2012.

Habitat:	
  Lesser	
  long-­nosed	
  bat	
  (Leptonycteris	
  yerbabuenae)

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?

Lesser	
  long-­‐nosed	
  bats	
  primarily	
  occupy	
  Sonoran	
  Desert	
  

vegetation	
  along	
  with	
  a	
  variety	
  of	
  woodlands,	
  grasslands,	
  

and	
  shrublands	
  where	
  food	
  resources	
  are	
  available.	
  

Climate	
  projections	
  indicate	
  possible	
  expansion	
  of	
  the	
  

Sonoran	
  Desert	
  northward	
  as	
  temperatures	
  warm	
  (Weiss	
  

and	
  Overpeck	
  2005).	
  Accordingly,	
  expansion	
  of	
  available	
  

habitat	
  for	
  lesser	
  long-­‐nosed	
  bat	
  might	
  be	
  inferred,	
  but	
  

other	
  important	
  issues	
  are	
  to	
  be	
  considered.	
  Expansion	
  

will	
  be	
  limited	
  by	
  projected	
  increases	
  in	
  fire	
  frequency	
  

and	
  increases	
  in	
  invasive	
  grass	
  species	
  that	
  will	
  both	
  be	
  

favored	
  by	
  a	
  warming	
  climate.	
  No	
  overall	
  change	
  in	
  area	
  

projected.

0

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	
  areas	
  will	
  likely	
  be	
  reduced	
  with	
  decreases	
  

in	
  Sonoran	
  Desert	
  habitats	
  to	
  the	
  south	
  in	
  Mexico	
  

predicted	
  by	
  temperature	
  and	
  precipitation	
  projections	
  in	
  

addition	
  to	
  the	
  interacting	
  effects	
  of	
  invasive	
  grasses	
  and	
  

fire	
  occurrence.	
  Sonoran	
  Desert	
  is	
  projected	
  to	
  decline	
  in	
  

the	
  southern	
  portions	
  of	
  the	
  range	
  (Weiss	
  and	
  Overpeck	
  

2005).	
  Active	
  conversion	
  of	
  Sonoran	
  Desert	
  to	
  grasslands	
  

and	
  projected	
  increases	
  in	
  fires	
  make	
  further	
  loss	
  of	
  

habitat	
  area	
  likely.

1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Several	
  types	
  of	
  roosts	
  are	
  used:	
  day	
  roosts,	
  maternity	
  

roosts,	
  bachelor	
  roosts,	
  and	
  temporary	
  night	
  roosts.	
  

Roosts	
  are	
  often	
  in	
  caves	
  or	
  abandoned	
  mines.	
  Maternity	
  

roosts	
  are	
  not	
  known	
  to	
  occur	
  on	
  BMGR.	
  Roosts	
  are	
  of	
  

variable	
  types	
  and	
  microclimates.	
  Climate	
  unlikely	
  to	
  

affect	
  availability	
  of	
  suitable	
  roosts.

0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Roosts	
  are	
  often	
  in	
  caves	
  or	
  abandoned	
  mines.	
  Individuals	
  

require	
  multiple	
  roost	
  types	
  at	
  different	
  locations.	
  

Thought	
  to	
  use	
  roosts	
  with	
  a	
  variety	
  of	
  microclimates,	
  so	
  

it	
  is	
  unlikely	
  that	
  warmer	
  temperatures	
  will	
  decrease	
  

roost	
  availability. 0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Warmer	
  maternity	
  caves	
  associated	
  with	
  better	
  

development	
  of	
  young	
  (Arends	
  and	
  others	
  1995).	
  May	
  

benefit	
  from	
  rising	
  temperatures.

-­1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Migratory	
  and	
  highly	
  mobile	
  moving	
  over	
  large	
  areas	
  to	
  

feed. -­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

For	
  Arizona,	
  this	
  species	
  is	
  a	
  long-­‐distance	
  migrant.	
  Some	
  

populations	
  remain	
  resident	
  in	
  Mexico.	
  Migratory	
  

behavior	
  is	
  thought	
  to	
  take	
  advantage	
  of	
  periodic	
  

resources	
  (USFWS	
  1995).	
  Males	
  and	
  females	
  follow	
  

progressive	
  flowering	
  of	
  columnar	
  cacti	
  and	
  paniculate	
  

agaves.	
  Although	
  highly	
  mobile,	
  they	
  avoid	
  crossing	
  high-­‐

density	
  urban	
  housing	
  (USFWS	
  2005).

1
USDA Forest Service RMRS-GTR-284. 2012. 113

Physiology:	
  Lesser	
  long-­nosed	
  bat	
  (Leptonycteris	
  yerbabuenae)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Lesser	
  long-­‐nosed	
  bats	
  have	
  a	
  lower	
  critical	
  temperature	
  

of	
  30.5 °C	
  and	
  generally	
  seek	
  warm	
  conditions	
  (Fleming	
  

and	
  others	
  1998).	
  They	
  often	
  roost	
  colonially	
  in	
  caves	
  that	
  

trap	
  metabolic	
  heat,	
  but	
  have	
  been	
  found	
  in	
  a	
  variety	
  of	
  

different	
  roost	
  conditions	
  (USFWS	
  1995).	
  Migratory	
  

females	
  give	
  birth	
  in	
  Arizona,	
  and	
  warmer	
  maternity	
  

roosts	
  may	
  increase	
  growth	
  rates	
  of	
  the	
  young	
  (Arends	
  

and	
  others	
  1995).	
  Leave	
  United	
  States	
  because	
  of	
  cold	
  

winter	
  conditions	
  and	
  seem	
  well	
  suited	
  to	
  desert	
  

conditions	
  with	
  a	
  fairly	
  high	
  lower	
  critical	
  temperature.	
  

While	
  projected	
  changes	
  are	
  not	
  expected	
  to	
  exceed	
  

physiological	
  thresholds,	
  they	
  may	
  instead	
  reduce	
  cold	
  

periods,	
  which	
  are	
  unsuitable.

-­1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

Heavy	
  rainfall	
  events,	
  which	
  are	
  expected	
  to	
  increase,	
  are	
  

associated	
  with	
  mortality	
  in	
  some	
  species—documented	
  

at	
  Carlsbad	
  Caverns.	
  Although	
  BMGR	
  has	
  no	
  known	
  

roosts,	
  individuals	
  that	
  forage	
  on	
  BMGR	
  may	
  use	
  roosts	
  

that	
  are	
  prone	
  to	
  flooding	
  (risk	
  unknown).

1

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Species	
  can	
  fly	
  long	
  distances	
  between	
  roosts	
  and	
  

foraging	
  sites	
  (from	
  50-­‐100	
  km;	
  USFWS	
  1995).	
  Although	
  

distance	
  from	
  roosts	
  to	
  foraging	
  areas	
  is	
  considered	
  an	
  

important	
  component	
  of	
  energy	
  expenditure,	
  lesser	
  long-­‐

nosed	
  bats	
  have	
  also	
  been	
  found	
  to	
  be	
  efficient	
  fliers	
  and	
  

well	
  adapted	
  to	
  performing	
  long,	
  daily	
  commutes	
  (Horner	
  

and	
  others	
  1998).	
  Active	
  at	
  night.	
  Rest	
  part	
  of	
  the	
  night	
  in	
  

night	
  roosts,	
  but	
  no	
  information	
  on	
  limitations	
  to	
  foraging	
  

on	
  hot	
  nights.	
  Although	
  distance	
  between	
  roost	
  sites	
  and	
  

foraging	
  locations	
  may	
  be	
  affected,	
  there	
  is	
  no	
  anticipated	
  

effect	
  because	
  apparently	
  do	
  not	
  need	
  to	
  expend	
  large	
  

amounts	
  of	
  energy	
  to	
  forage	
  at	
  distant	
  locations.

0

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Migratory	
  behavior	
  seems	
  to	
  be	
  variable	
  with	
  both	
  

migratory	
  and	
  sedentary	
  strategies	
  that	
  may	
  be	
  an	
  

adaptation	
  to	
  highly	
  variable	
  flowering	
  resources	
  (Rojas-­‐

Martinez	
  and	
  others	
  1999).	
  Occurrence	
  of	
  migratory	
  and	
  

non-­‐migratory	
  demes	
  related	
  to	
  resource	
  availability	
  and	
  

likely	
  helpful	
  with	
  fluctuating	
  resources.	
  All	
  individuals	
  at	
  

BMGR,	
  however,	
  are	
  migratory,	
  so	
  these	
  populations	
  do	
  

not	
  possess	
  this	
  alternative,	
  and	
  plasticity	
  in	
  behavior	
  

within	
  demes	
  is	
  unknown.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic. 0
114 USDA Forest Service RMRS-GTR-284. 2012.

Phenology:	
  Lesser	
  long-­nosed	
  bat	
  (Leptonycteris	
  yerbabuenae)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Do	
  not	
  hibernate. Probably	
  initiate	
  migration	
  based	
  on	
  

flowering	
  resources,	
  but	
  it	
  may	
  also	
  be	
  related	
  to	
  progress	
  

of	
  pregnancy	
  in	
  females.	
  No	
  direct	
  moisture	
  or	
  

temperature	
  cues	
  known.	
   0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

Migratory	
  females	
  arrive	
  in	
  Arizona	
  pregnant	
  and	
  give	
  

birth	
  to	
  one	
  young	
  that	
  can	
  fly	
  at	
  about	
  4	
  weeks.	
  Birth	
  is	
  

not	
  highly	
  synchronous	
  among	
  individuals	
  at	
  the	
  same	
  

maternity	
  cave, as	
  pregnant	
  females	
  co-­‐occur	
  with	
  

females	
  with	
  young	
  that	
  are	
  ready	
  to	
  fly	
  (USFWS	
  1995).	
  

Females	
  that	
  do	
  not	
  migrate	
  give	
  birth	
  in	
  winter	
  in	
  Mexico	
  

(USFWS	
  2005).	
  Migration	
  and	
  breeding	
  is	
  tied	
  to	
  

flowering	
  timing,	
  which	
  is	
  likely	
  to	
  be	
  altered	
  by	
  changes	
  

in	
  temperature	
  and	
  precipitation.	
  

1

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Lesser	
  long-­‐nosed	
  bats	
  are	
  present	
  April	
  to	
  November	
  in	
  

Arizona,	
  although	
  this	
  seems	
  to	
  vary	
  by	
  year.	
  Movements	
  

coincide	
  with	
  blooming	
  (cactus	
  in	
  the	
  spring	
  and	
  agave	
  in	
  

the	
  summer).	
  Likely	
  that	
  this	
  species’	
  movements	
  are	
  

directly	
  related	
  to	
  presence	
  of	
  nectar	
  resources,	
  thus	
  has	
  

the	
  potential	
  to	
  respond	
  quickly	
  to	
  changes.

-­1

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  reproductive	
  event	
  per	
  year.

1

Biotic	
  Interactions:	
  Lesser	
  long-­nosed	
  bat	
  (Leptonycteris	
  yerbabuenae)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Lesser	
  long-­‐nosed	
  bats	
  are	
  adapted	
  to	
  feed	
  on	
  nectar	
  and	
  

pollen	
  of	
  various	
  columnar	
  cactus	
  and	
  paniculate	
  agave	
  

species.	
  They	
  are	
  able	
  to	
  switch	
  between	
  various	
  cactus	
  

and	
  agave	
  species	
  when	
  flowering	
  of	
  one	
  species	
  fails.

Also	
  may	
  eat	
  insects	
  and	
  fruits	
  and	
  have	
  been	
  observed	
  to	
  

use	
  hummingbird	
  feeders	
  (USFWS	
  2005). Northern	
  

migrants	
  eat	
  almost	
  exclusively	
  CAM	
  plants	
  (agaves	
  and	
  

cacti).	
  Because	
  of	
  their	
  ability	
  to	
  open	
  their	
  stomates	
  at	
  

night,	
  CAM	
  plants	
  are	
  well	
  adapted	
  to	
  dry	
  conditions.	
  In

Mexico,	
  lesser	
  long-­‐nosed	
  bats	
  are	
  known	
  to	
  feed	
  on	
  C3

plants	
  (most	
  shrubs	
  and	
  forbs)	
  as	
  well	
  (Fleming	
  and	
  

others	
  1993).	
  Species	
  on	
  BMGR	
  are	
  primarily	
  saguaro	
  and	
  

desert	
  agave.	
  These	
  CAM	
  plants	
  are	
  resilient	
  to	
  dry	
  

conditions,	
  but	
  flowering	
  and	
  thus	
  nectar	
  availability	
  

generally	
  decreases	
  under	
  dry	
  conditions.	
  In	
  addition,	
  

more	
  variable	
  rainfall	
  may	
  increase	
  variability	
  in	
  

flowering.

1
USDA Forest Service RMRS-GTR-284. 2012. 115

Biotic	
  Interactions:	
  Lesser	
  long-­nosed	
  bat	
  (Leptonycteris	
  yerbabuenae)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Few	
  incidences	
  of	
  predation	
  have	
  been	
  documented	
  and	
  

predators	
  were	
  various.	
  No	
  avoidance	
  of	
  activity	
  during	
  

full	
  moons	
  suggests	
  predation	
  pressure	
  while	
  foraging	
  is	
  

not	
  strong	
  (USFWS	
  1995).	
  There	
  is	
  a	
  potential	
  for	
  large	
  

impacts	
  of	
  single	
  predators	
  at	
  small	
  roosts,	
  but	
  overall	
  

predation	
  probably	
  has	
  little	
  impact	
  on	
  populations.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

This	
  species	
  is	
  an	
  important,	
  but	
  not	
  exclusive,	
  pollinator	
  

and	
  seed	
  disperser	
  for	
  these	
  plants.	
  Some	
  researchers	
  cite	
  

close	
  association	
  and	
  bat	
  adaptations	
  in	
  paniculate	
  agaves	
  

and	
  columnar	
  cacti	
  as	
  evidence	
  for	
  a	
  tight	
  mutualistic	
  

relationship,	
  but	
  others	
  have	
  noted	
  that	
  this	
  relationship	
  

is	
  likely	
  not	
  as	
  strong	
  in	
  the	
  southwestern	
  United	
  States

and	
  northwest	
  Mexico	
  as	
  in	
  areas	
  where	
  nectar-­‐feeding	
  

bats	
  occur	
  year-­‐round	
  (Fleming	
  and	
  others	
  2001).	
  

Foraging	
  plant	
  populations	
  expected	
  to	
  survive	
  warmer	
  

temperatures	
  and	
  reduced	
  rainfall.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

Rabies	
  has	
  been	
  found	
  in	
  this	
  species	
  in	
  Mexico	
  and,	
  while	
  

it	
  can	
  result	
  in	
  bat	
  mortality,	
  rabies	
  is	
  not	
  common	
  and	
  

generally	
  not	
  considered	
  to	
  be	
  a	
  significant	
  threat	
  to	
  bat	
  

populations	
  (Gillette	
  and	
  Kimbrough	
  1970).	
  Another	
  

emerging	
  bat	
  disease	
  is	
  white-­‐nose	
  syndrome,	
  which	
  has	
  

been	
  killing	
  large	
  numbers	
  of	
  roosting	
  bats	
  in	
  

northeastern	
  North	
  America.	
  So	
  far,	
  it	
  appears	
  this	
  

disease	
  only	
  threatens	
  hibernating	
  species	
  and	
  is	
  

associated	
  with	
  cold	
  conditions	
  (Blehert	
  and	
  others

2008).	
  Lesser	
  long-­‐nosed	
  bats	
  have	
  neither	
  of	
  these	
  risk	
  

factors.	
  

0

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Lesser	
  long-­‐nosed	
  bats	
  roost	
  with	
  a	
  variety	
  of	
  other	
  bats	
  

in	
  Mexico	
  (Arita	
  1993)	
  and	
  do	
  not	
  appear	
  to	
  segregate	
  

from	
  other	
  bat	
  species	
  at	
  roosts. Other	
  nocturnal	
  

nectarivores	
  that	
  exploit	
  these	
  nectar	
  resources	
  are	
  much	
  

smaller	
  (e.g.,	
  moths	
  and	
  birds),	
  so	
  probably	
  little	
  

competition.	
  Could	
  compete	
  with	
  other	
  nectarivorous

bats,	
  but	
  Mexican	
  long-­‐tongued	
  bat	
  probably	
  exploits	
  

additional	
  flower	
  resources	
  with	
  its	
  longer	
  tongue.	
  

Expected	
  to	
  be	
  similarly	
  affected	
  by	
  climate	
  change.

0
116 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Arita, H. T. 1993. Conservation biology of the cave bats of Mexico. Journal of Mammalogy 74:693-702.

Arends, A., F. J. Bonaccorso, and M. Genoud. 1995. Basal rates of metabolism of nectarivorous bats 

(Phyllostomidae) from a semiarid thorn forest in Venezuela. Journal of Mammalogy 76:947-956.

Arnett, E. B., W. Brown, W. P. Erickson, [and others]. 2008. Patterns of bat fatalities at wind energy facilities in 

North America. Journal of Wildlife Management 72:61-78.

Arriaga, L., A. Castellanos V., E. Moreno, and J. Alarcon. 2004. Potential ecological distribution of alien invasive 

species and risk assessment: a case study of buffel grass in arid regions of Mexico. Conservation Biology 

18:1504-1514.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

Beatty, L. D. 1955. Autecology of the longnose bat, Leptonycteris nivalis (Saussure). Unpublished thesis, 

University of Arizona, Tucson. (Primary document unavailable; as referenced in Scott 2004.)

Blehert, D. S., A. C. Hicks, M. Behr, C. U. Meteyer, B. M. Berlowski-Zier, and E. L. Buckles. 2008. Bat white-nose 

syndrome: an emerging fungal pathogen? Sciencexpress. Published online October 30, 2008; 10.1123/

science.11638.

Burquez-Montijo, A., M. Miller, and A. Martinez-Yrizar. 2002. Mexican grasslands, thornscrub, and the 

transformation of the Sonoran Desert by invasive exotic buffelgrass. Pages 126-146 In B. Tellman, ed., 

Arizona-Sonoran Desert Museum Studies in Natural History, Tucson, AZ.

Cockrum, E. L. 1991. Seasonal distribution of northwestern populations of the long-nosed bats, Leptonycteris 

sanborni Family Phyllostomidae. Anales del Instituto Biologica, Universidad Nacional Autonoma de Mexico, 

Serie Zoologica 62:181-202.

Comrie, A. C. and E. C. Glenn. 1998. Principal components-based regionalization of precipitation regimes 

across southwest United States and northern Mexico, with an application to monsoon precipitation 

variability. Climate Research 10:201-215.

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Fleming, T. H., R. A. Nufiez, and L. L. Sternberg. 1993. Seasonal changes in the diets of migrant and nonmigrant nectarivorous bats as revealed by carbon stable isotope analysis. Oecologia 94:72-75.

Fleming, T. H., A. A. Nelson, and V. M. Dalton. 1998. Roosting behavior of the lesser long-nosed bat, 

Leptonycteris curacoae. Journal of Mammalogy 79:147-155.

Fleming, T. H., C. T. Sahley, N. Holland, J. D. Nason, and J. L. Hamrick. 2001. Sonoran columnar cacti and the 

evolution of generalized pollination systems. Ecological Monographs 71:511-530.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Gillette, D. D. and J. D. Kimbrough. 1970. Chiropteran Mortality. In B. Slaugher and D. Walton, eds., About Bats. 

Southern Methodist University Press, Dallas, TX.

Graham, E. A. and P. S. Nobel. 1996. Long term effects of a doubled atomospheric CO2 concentration on the 

CAM species Agave deserti. Journal of Experimental Botany 47:61-69.

 Horner M. A., T. H. Fleming, and C. T. Sahley. 1998. Foraging behaviour and energetics of a nectar-feeding bat, 

Leptonycteris curasoae (Chiroptera: Phyllostomidae). Journal of Zoology, London 244:575-586.

Howell, D. J. and B. S. Roth. 1981. Sexual reproduction in agaves: the benefits of bats; the cost of semelparous 

advertising. Ecology 62:1-7.

Liverman, D. M. and K. L. O’Brien. 1991. Global warming and climate change in Mexico. Pages 351-364 In 

Global Environmental Change. Butterworth-Heinemann Ltd.
USDA Forest Service RMRS-GTR-284. 2012. 117

Maurer, E. P., L. Brekke, T. Pruitt, and P. B. Duffy. 2007. Fine-resolution climate projections enhance regional 

climate change impact studies, Eos Trans. AGU, 88(47):504.

McLaughlin, S. E. and J. P. Bowers. 1982. Effects of wildfire on a Sonoran Desert plant community. Ecology 

63:246-248.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Ober, H. K. and R. J. Steidl. 2004. Foraging rates of Leptonycteris curasoae vary with characteristics of Agave 

palmeri. Southwestern Naturalist 49:68-74.

Ober, H. K., R. J. Steidl, and V.M. Dalton. 2000. Foraging ecology of lesser long-nosed bats. Final Report to 

University of Arizona, School of Renewable Natural Resources, Tucson, AZ. 25 p.

Rojas-Martinez, A., A. Valiente-Banuet, M. del Coro Arizmendi, A. Alcantara-Eguren, and H. T. Arita. 1999. 

Seasonal distribution of the long-nosed bat (Leptonycteris curasoae) in North America: does a generalized 

migration pattern really exist? Journal of Biogeography 26:1065-1077.

Scott, P. 2004. Timing of Agave palmeri flowering and nectar-feeding bat visitation in the Peloncillos and 

Chiracahua Mountains. Southwestern Naturalist 49:425-434.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Slauson, L. A. 2000. Pollination biology of two chiropterophilous agaves in Arizona. American Journal of Botany 

87:825-836.

U.S. Fish and Wildlife Service (USFWS). 1995. Recovery plan for the lesser long-nosed bat, Leptonycteris 

curasoae yerbabuenae. U.S. Fish and Wildlife Service, Albuquerque, NM. 45 p.

U.S. Fish and Wildlife Service (USFWS). 2005. Lesser long-nosed bat five year review: summary and evaluation. 

Prepared by Richardson, Scott. Arizona Ecological Service Office, Tucson, AZ.

Vásquez-León, M., C. T. West, and T. J. Finan. 2003. A comparative assessment of climate vulnerability: 

agriculture and ranching on both sides of the US-Mexico border. Global Environmental Change 13:159-173.

Van Devender, T. R. and M. A. Dimmitt. 2006. Final report on conservation of Arizona upland Sonoran Desert 

habitat: status and threats of buffelgrass (Pennisetum ciliare) in Arizona and Sonora. Arizona-Sonora Desert 

Museum, Tucson, AZ.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140. 
118 USDA Forest Service RMRS-GTR-284. 2012.

Desert Bighorn Sheep

(Ovis canadensis mexicana)

SUMMARY

Desert bighorn sheep has a number of characteristics that should aid survival during dry periods, which are 

expected to increase in the region with projected climate change. Overall, this species is predicted to be moderately vulnerable to detrimental effects of climate change. Water availability has important relationships with 

bighorn breeding and survival and is likely to be an increasingly critical issue. Management actions that can 

mitigate drought conditions should be considered, but the ability of artificial waters to buffer populations has 

not been demonstrated so far. Although not currently major threats in the Southwest, interactions of climate 

with predation and disease need investigation.

VULNERABILITY Score Uncertainty

Habitat -0.1 29%

Physiology 1.5 33%

Phenology 2.5 25%

Interactions 1.0 40%

Overall 4.3 32%

Introduction

There are four desert subspecies of bighorn sheep. The mexicana subspecies has no USFWS status but is 

designated as sensitive by the U.S. Forest Service and managed as a game species on BMGR. As of April 2009, 

hunting was closed on BMGR east of Highway 85 because of declining populations but remains open to the 

west of Highway 85. 

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• CAM plants (succulents and cacti) will be resilient to increasing temperatures (Smith and others 1984)

-5 0 5

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0
USDA Forest Service RMRS-GTR-284. 2012. 119

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Other Threats and Interactions with Climate

Low population size in the desert bighorn sheep elevates even small mortality factors to critical stressors. 

Declines during drought periods may be regular occurrences (McKinney and others 2001), but low population 

size makes subsequent recovery slow and local extinctions more likely.

At Cabeza Prieta National Wildlife Refuge, presence of permanent water did not appear to affect bighorn 

sheep populations (Broyles and Cutler 1999). Water has been suggested as limiting to populations, particularly 

during hot periods, but water sources may also be a source of toxins or disease, attract predators, and 

increase human disturbance (see Broyles and Cutler 1999 for discussion). Conversely, bighorn sheep is 

documented to use artificial water sources, and mortality from dehydration might be inferred from several 

cases where dead individuals have been found at water sources that have gone dry. Water limitations may 

interact with issues of reduced forage during drought periods.

An analysis of California bighorn sheep metapopulations and predicted response to climate change found 

that elevation, permanent springs, and precipitation were important to persistence (Epps and others 2004). 

Metapopulations in drier, low-elevation areas were more vulnerable, which likely indicates that Arizona 

populations are vulnerable to a warming climate based on these same factors.

Research Needs

Predation and disease have been identified as important threats to desert bighorn, but interactions of these 

factors with climate are not well known. These interactions will be critical to anticipating climate change 

response. Ability of artificial waters to buffer populations from declines has not been demonstrated, but has 

also received only limited study.

Management Implications

A recent study by Cain and others (2008) did not find detrimental effects on survival or reproduction with 

removal of artificial water sources, but precipitation variation during the study made conclusions difficult. 

Artificial waters, however, did not prevent mortalities during drought conditions of the pre-treatment period. 

The question of managing wildlife by creating artificial water sources is becoming a more critical one. The 

current benefits of artificial waters to bighorn populations have not been well documented (Broyles 1995), but 

as temperatures increase, the potential benefit of artificial waters is increased as physiological thresholds are 

approached.

BMGR is closed to cattle grazing, which has minimized issues related to grazing competition and disease 

transmission. Some trespass grazing and grazing by feral burros occurs (BMGR 2003), but is unlikely to have 

significant or altered impacts with climate change unless there is increased contact with livestock that results 

in disease transmission, such as through attraction to a localized water source. 
120 USDA Forest Service RMRS-GTR-284. 2012.

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?

Desert	
  bighorn	
  sheep	
  are	
  associated	
  with	
  a	
  wide	
  variety	
  

of	
  vegetation	
  types	
  in	
  rugged	
  mountainous	
  terrain,

including	
  juniper	
  and	
  desert	
  scrub	
  communities.	
  In	
  the	
  

Harqualaha	
  Mountains,	
  bighorn	
  sheep	
  were	
  found	
  to	
  

avoid	
  permanent	
  water	
  and	
  bajadas,	
  while	
  favoring	
  areas	
  

with	
  preferred	
  browse	
  species	
  and	
  open	
  vegetation	
  

(Krausman	
  and	
  Leopold	
  1986).	
  In	
  addition,	
  they	
  have	
  

been	
  associated	
  with	
  vegetation	
  that	
  included	
  ocotillo	
  

(Krausman	
  and	
  others	
  1989).	
  Relative	
  proportions	
  of	
  

grass,	
  shrubs,	
  and	
  forbs	
  expected	
  to	
  vary	
  with	
  increased	
  

temperatures	
  plus	
  interactions	
  with	
  fire	
  and	
  invasive	
  

plants,	
  but	
  suitable	
  rugged	
  mountain	
  habitats	
  expected	
  to	
  

remain	
  relatively	
  unchanged.

0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

None	
  known.

0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Barrel	
  cacti	
  may	
  be	
  an	
  important	
  water	
  source	
  during	
  hot	
  

periods	
  (Warrick	
  and	
  Krausman	
  1989).	
  It	
  has	
  been	
  

suggested	
  that	
  these	
  benefits	
  may	
  be	
  lost	
  during	
  dry	
  

periods	
  when	
  cacti	
  become	
  dehydrated.	
  Cacti	
  can	
  lose	
  up	
  

to	
  81%	
  of	
  their	
  water	
  after	
  being	
  dehydrated	
  for	
  18	
  

months	
  and	
  still	
  survive	
  (Barcikowski	
  and	
  Nobel	
  1984),	
  

but	
  presumably,	
  the	
  benefits	
  from	
  eating	
  dessicated	
  

cactus	
  would	
  be	
  reduced.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

For	
  Ovis	
  canadensis	
  nelsoni	
  in	
  Nevada,	
  higher	
  

precipitation	
  in	
  September	
  to	
  December	
  had	
  a	
  positive	
  

effect	
  on	
  lamb	
  survival	
  the	
  following	
  year,	
  presumably	
  

through	
  increased	
  plant	
  growth	
  (Douglas	
  and	
  Leslie	
  

1986).	
  Higher	
  winter	
  precipitation	
  was	
  also	
  associated	
  

with	
  population	
  increases	
  in	
  Arizona	
  (McKinney	
  and	
  

others	
  2001).	
  Lower	
  lamb	
  survival	
  has	
  been	
  associated	
  

with	
  lower	
  quality	
  of	
  forage	
  (Krausman	
  and	
  others	
  1988).	
  

Winter	
  precipitation	
  expected	
  to	
  be	
  unchanged,	
  but	
  soil	
  

moisture	
  available	
  to	
  plants	
  reduced	
  with	
  warmer	
  

temperatures.	
  Many	
  vegetation	
  characteristics	
  may	
  relate	
  

to	
  predator	
  avoidance,	
  which	
  may	
  be	
  increased	
  in	
  open	
  

vegetation	
  types	
  where	
  visibility	
  is	
  improved.	
  Other	
  

studies	
  have	
  also	
  found	
  a	
  positive	
  association	
  of	
  bighorn	
  

sheep	
  presence	
  and	
  escape	
  terrain	
  (Andrew	
  and	
  others

1999;	
  McKinney	
  and	
  others	
  2003).	
  There	
  is	
  little	
  

quantitative	
  data,	
  however,	
  on	
  the	
  relation	
  between	
  

survival	
  and	
  landscape	
  variables	
  presumably	
  associated	
  

with	
  predator	
  avoidance.	
  More	
  open	
  vegetation	
  types	
  and	
  

abiotic	
  features	
  may	
  increase	
  predator	
  detection	
  and	
  

increase	
  survival.	
  Cacti	
  or	
  other	
  succulent	
  plants	
  may	
  be	
  

important	
  for	
  surviving	
  dry	
  periods.	
  Cacti	
  are	
  relatively	
  

1
USDA Forest Service RMRS-GTR-284. 2012. 121

Habitat:	
  Desert	
  bighorn	
  sheep	
  (Ovis	
  canadensis	
  mexicana)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

resistant	
  to	
  drought	
  conditions.	
  Most	
  associations	
  

expected	
  to	
  remain	
  unchanged,	
  but	
  quality	
  of	
  forage	
  is	
  

expected	
  to	
  be	
  more	
  variable	
  as	
  rainfall	
  becomes	
  more	
  

variable.

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Highly	
  mobile.

-­1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Seasonal	
  movements,	
  but	
  no	
  additional	
  habitats	
  required.

0

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	
  are	
  well	
  adapted	
  to	
  water	
  

limitations	
  and	
  have	
  the	
  ability	
  to	
  reduce	
  water	
  losses	
  

from	
  urine	
  and	
  feces,	
  absorb	
  water	
  into	
  the	
  bloodstream	
  

rapidly,	
  and	
  have	
  red	
  blood	
  cells	
  resistant	
  to	
  osmotic	
  

stress	
  (Hansen	
  1982).	
  There	
  is	
  disagreement	
  over	
  the	
  

importance	
  of	
  water	
  for	
  the	
  subspecies	
  (Smith	
  and	
  

Krausman	
  1988;	
  Broyles	
  and	
  Cutler	
  1999).	
  Drought	
  years	
  

are	
  associated	
  with	
  reduced	
  populations	
  and	
  lower	
  

survival	
  rates	
  (McKinney	
  and	
  others	
  2001).	
  Observed	
  

mortality	
  during	
  droughts	
  historically	
  indicates	
  that	
  this	
  

species	
  may	
  not	
  tolerate	
  further	
  temperature	
  increases	
  or	
  

moisture	
  stress.

1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

No	
  known	
  mortality	
  from	
  disturbance	
  events,	
  although	
  

some	
  likely	
  occurs.

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Actively	
  seek	
  shade	
  and	
  may	
  spend	
  more	
  time	
  inactive	
  

when	
  temperatures	
  are	
  high.	
  Higher	
  temperatures	
  may	
  

reduce	
  activities	
  or	
  movements. 1

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Some	
  studies	
  have	
  found	
  breeding	
  can	
  extend	
  to	
  most	
  of	
  

the	
  year,	
  but	
  that	
  the	
  majority	
  of	
  lambs	
  are	
  born	
  in	
  the	
  

spring	
  (Rubin	
  and	
  others	
  2000).	
  An	
  extended	
  

reproductive	
  period	
  may	
  be	
  advantageous	
  to	
  variable	
  

conditions.	
  This	
  may	
  be	
  advantageous	
  for	
  increasing	
  

variability	
  in	
  rainfall.

-­1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate. 0
122 USDA Forest Service RMRS-GTR-284. 2012.

	
  	
  	
  	
  	
  	
  	
  	
  	
  

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?	
  

Not	
  known	
  what	
  triggers	
  breeding,	
  but	
  at	
  least	
  partly	
  

internal.

0

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?	
  

In	
  the	
  Harqualaha	
  Mountains,	
  lambs	
  were	
  born	
  from	
  

January	
  to	
  June	
  (Krausman	
  1989).	
  In	
  California,	
  most	
  

young	
  were	
  born	
  in	
  March	
  following	
  winter	
  rains	
  when	
  

forage	
  was	
  highest	
  and	
  before	
  dry	
  conditions	
  arrived,	
  

which	
  presumably	
  increased	
  survival	
  (Rubin	
  and	
  others

2000).	
  Survival	
  was	
  lower	
  in	
  lambs	
  born	
  after	
  the	
  peak	
  

period	
  (Rubin	
  and	
  others	
  2000).	
  Another	
  study	
  in	
  New	
  

Mexico	
  noted	
  prolonged	
  and	
  irregular	
  breeding	
  timing	
  

with	
  lambs	
  born	
  from	
  December	
  to	
  September,	
  suggesting	
  

this	
  strategy	
  could	
  be	
  in	
  response	
  to	
  unpredictable	
  

rainfall	
  patterns	
  (Lenarz	
  1979).	
  Timing	
  of	
  births	
  has	
  been	
  

related	
  to	
  survival	
  of	
  lambs	
  in	
  some	
  studies.	
  Availability	
  of	
  

forage	
  in	
  the	
  spring	
  is	
  important	
  for	
  lamb	
  survival.	
  

Changes	
  in	
  precipitation	
  patterns	
  are	
  likely	
  to	
  alter	
  the	
  

arrival	
  of	
  peak	
  forage	
  conditions.

1

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Available	
  forage	
  does	
  not	
  occur	
  far	
  in	
  advance	
  or	
  at	
  

distant	
  locations	
  from	
  breeding.	
  

0

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Adults	
  can	
  breed	
  every	
  year,	
  but	
  a	
  study	
  in	
  Arizona	
  found	
  

that	
  there	
  were	
  often	
  no	
  lambs	
  produced	
  the	
  year	
  after	
  a	
  

successful	
  breeding	
  so,	
  effectively,	
  breeding	
  occurs	
  less	
  

than	
  once	
  a	
  year	
  (Krausman	
  and	
  others	
  1989).

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?

Desert	
  bighorn	
  sheep	
  eat	
  a	
  wide	
  variety	
  of	
  plant	
  species	
  

and	
  vary	
  use	
  with	
  availability.	
  Shrub	
  species	
  are	
  dominant	
  

in	
  the	
  diet	
  followed	
  by	
  forbs	
  and	
  then	
  grasses	
  (Krausman	
  

and	
  others	
  1989;	
  Miller	
  and	
  Gaud	
  1989).	
  They	
  also	
  eat	
  

barrel	
  cactus	
  and	
  obtain	
  water	
  from	
  it	
  during	
  hot	
  periods	
  

(Warrick	
  and	
  Krausman	
  1989).	
  Shrubs	
  may	
  be	
  reduced	
  by	
  

fire,	
  but	
  forbs	
  and	
  grasses	
  may	
  be	
  encouraged.	
  Shrubs	
  and	
  

shrub	
  foliage	
  may	
  also	
  be	
  reduced	
  periodically	
  by	
  

drought.	
  Cacti	
  are	
  an	
  important	
  component	
  of	
  forage	
  

during	
  drought	
  periods	
  and	
  are	
  resistant	
  to	
  drought.

0
USDA Forest Service RMRS-GTR-284. 2012. 123

Biotic	
  Interactions:	
  Desert	
  bighorn	
  sheep	
  (Ovis	
  canadensis	
  mexicana)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Mountain	
  lions	
  are	
  often	
  considered	
  a	
  significant	
  predator	
  

(Hayes	
  and	
  others	
  2000).	
  Coyotes	
  are	
  common	
  predators	
  

of	
  lambs.	
  Other	
  predators	
  include	
  bobcats	
  and	
  gray	
  fox.	
  In	
  

the	
  Southwest,	
  predation	
  is	
  thought	
  to	
  be	
  primarily	
  

opportunistic	
  and	
  not	
  a	
  serious	
  threat	
  (Smith	
  and	
  

Krausman	
  1988).	
  Various	
  predators,	
  which	
  are	
  probably	
  

also	
  limited	
  by	
  drought.	
  No	
  expected	
  increases.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

Bighorn	
  sheep	
  are	
  prone	
  to	
  transmission	
  of	
  disease	
  from	
  

domestic	
  sheep.	
  Many	
  documented	
  cases	
  of	
  high	
  mortality

and	
  disease	
  in	
  bighorns,	
  including	
  pneumonia	
  Pasteurella	
  

sp.	
  (Callan	
  and	
  others	
  1991),	
  bluetongue	
  (Robinson	
  and	
  

others	
  1967),	
  botulism	
  (Swift	
  and	
  others	
  2000),	
  chronic	
  

sinusitis	
  (Bunch	
  and	
  Allen	
  1981),	
  and	
  scabies	
  (Lange	
  

1980).	
  Sources	
  of	
  transmission	
  include	
  other	
  ungulates,	
  

mites,	
  bot	
  flies,	
  and	
  contaminated	
  water	
  sources.	
  

Susceptible	
  to	
  a	
  wide	
  range	
  of	
  diseases.	
  Livestock	
  grazing	
  

is	
  limited	
  and	
  is	
  not	
  likely	
  to	
  be	
  an	
  increasing	
  source	
  of	
  

infections.	
  Use	
  of	
  limited	
  water	
  (artificial	
  and	
  natural)	
  

may	
  be	
  increased	
  with	
  drier	
  conditions	
  and	
  may	
  also	
  

increase	
  disease	
  transmission.

1

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Some	
  competition	
  with	
  native	
  ungulates	
  has	
  been	
  

documented	
  for	
  food	
  and	
  water,	
  but	
  appears	
  to	
  not	
  be	
  

detrimental	
  in	
  the	
  Southwest	
  (Smith	
  and	
  Krausman	
  

1988).	
  Examination	
  of	
  diet	
  in	
  mule	
  deer	
  and	
  bighorns	
  

found	
  little	
  overlap	
  (Krausman	
  and	
  others	
  1989),	
  but	
  

there	
  are	
  concerns	
  about	
  competition	
  for	
  water	
  with	
  this	
  

species.	
  Conversely,	
  negative	
  competitive	
  effects	
  of	
  

domestic	
  livestock	
  have	
  been	
  documented	
  and	
  implicated	
  

in	
  bighorn	
  sheep	
  declines	
  (Smith	
  and	
  Krausman	
  1988).	
  

No	
  livestock	
  grazing	
  on	
  BMGR.	
  Bighorn	
  sheep	
  may	
  also	
  

compete	
  with	
  other	
  wildlife	
  for	
  water,	
  but	
  extent	
  is	
  

unknown	
  and	
  probably	
  limited.

0
124 USDA Forest Service RMRS-GTR-284. 2012.

Literature Cited

Andrew, N. G., V. C. Bleich, and P. V. August. 1999. Habitat selection by mountain sheep in the Sonoran Desert: 

implications for conservation in the United States and Mexico. California Wildlife Conservation Bulletin 

12:1-30.

Arizona Game and Fish Department. 2006. DRAFT. Arizona’s Comprehensive Wildlife Conservation Strategy: 

2005-2015. Arizona Game and Fish Department, Phoenix, AZ.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

Barcikowski, W. and P. S. Nobel. 1984. Water relations of cacti during desiccation: distribution of water in 

tissues. Botanical Gazette 145:110-115.

Barry M. Goldwater Range (BMGR). 2003. Proposed integrated natural resources management plan: draft EIS. 

Departments of the Air Force, Navy, and Interior, AZ.

Broyles, B. 1995. Desert wildlife water developments: questioning use in the Southwest. Wildlife Society 

Bulletin 23:663-675.

Broyes, B. and T. 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.

Bunch, T. D. and S. D. Allen. 1981. Survey of chronic sinusitis-induced skull anomalies in desert bighorn sheep. 

Journal of the American Veterinary Medicine Association 179:1150-1152.

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 171:1-32.

Callan, R. J., T. D. Bunch, G. W. Workman, and R. E. Mock. 1991. Development of pneumonia in desert bighorn 

sheep after exposure to a flock of exotic wild and domestic sheep. Journal of the American Veterinary 

Medicine Association 198:1052-1056.

Dewey, T. and L. Ballenger. 1999. “Ovis canadensis” [Online]. Animal Diversity Web. Online at: http://

animaldiversity.ummz.umich.edu. (Accessed November 18, 2009)

Epps, C. W., D. R. McCullouch, J. D. Wehausen, V. C. Bleich, and J. L. Rechel. 2004. Effects of climate change on 

population persistence of desert-dwelling mountain sheep in California. Conservation Biology 18:102-113.

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17.

Hansen, M. C. 1982. Desert bighorn sheep: another view. Wildlife Society Bulletin 10:133-140.

Hayes, C. L., E. S. Rubin, M. C. Jorgensen, R. A. Botta, and W. M. Boyce. 2000. Mountain lion predation of 

bighorn sheep in the Peninsular Ranges, California. The Journal of Wildlife Management 64:954-959.

Hoffmeister, D. F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish Dept. 

602 p.

Krausman, P. R. and B. D. Leopold. 1986. Habitat components for desert bighorn sheep in the Harquahala 

Mountains, Arizona. The Journal of Wildlife Management 50:504-508.

Krausman, P. R., B. D. Leopold, R. F. Seegmiller, and S. G. Torres 1989. Relationships between desert bighorn 

sheep and habitat in western Arizona. Wildlife Monographs 102:3-66.

Lange, R. E., A. V. Sandoval, and W. P. Meleny. 1980. Psoroptic scabies in bighorn sheep (Ovis canadensis 

mexicana) in New Mexico. Journal of Wildlife Disease 16:77-82.

Lenarz, M. S. 1979. Social structure and reproductive strategy in desert bighorn sheep (Ovis canadensis 

mexicana). Journal of Mammalogy 60:671-678.

Liverman, D. M. and K. L. O’Brien. 1991. Global warming and climate change in Mexico. Pages 351-364 In 

Global Environmental Change. Butterworth-Heinemann Ltd.
USDA Forest Service RMRS-GTR-284. 2012. 125

McKinney, T., T. W. Smith, and J. D. Hanna. 2001. Precipitation and desert bighorn sheep in the Mazatzal 

Mountains, Arizona. The Southwestern Naturalist 46:345-353. 

McKinney, T., S. R. Boe and J. C. deVos, Jr. 2003. GIS-based evaluation of escape terrain and desert bighorn 

sheep populations in Arizona. Wildlife Society Bulletin 31:1229-1236.

McLaughlin, S. E. and J. P. Bowers. 1982. Effects of wildfire on a Sonoran Desert plant community. Ecology 

63:246-248.

McPherson, G. R. and J. F. Weltzin. 2000. Disturbance and climate change in United States/Mexico borderland 

plant communities: a state-of-the-knowledge review. USDA Forest Service, Rocky Mountain Research 

Station, Gen. Tech. Rep. RMRS-GTR-50.

Miller, G. D. and W. S. Gaud. 1989. Composition and variability of desert bighorn sheep diets. Journal of 

Wildlife Management 53:597-606.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Pinkava, D. J. 1999. Cactaceae cactus family, part three, Cylindropuntia. Journal of the Arizona-Nevada 

Academy of Science 32:32-47.

O’Brien, C., S. Rosenstock, J. Hervert, J. Bright, and S. Boe. 2005. Landscape-level models of potential habitat 

for Sonoran pronghorn. Wildlife Society Bulletin 33:24-34.

Robinson, R. M., T. L. Hailey, C. W. Livingston, and J. W. Thomas. 1967. Bluetongue in the desert bighorn sheep. 

The Journal of Wildlife Management 31:165-168.

Rubin, E. S., W. M. Boyce, and V. C. Bleich. 2000. Reproductive strategies of desert bighorn sheep. Journal of 

Mammalogy 81:769-786.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Smith, N. S. and P. R. Krausman. 1988. Desert bighorn sheep: a guide to selected management practices. U.S. 

Fish and Wildlife Service Biological Report 88.

Smith, S. D., B. Didden-Zopfy, and P. S. Nobel. 1984. High-temperature responses of North American cacti. 

Ecology 65:643-651.

SWIFT, P. K., J. D. Wehausen, H. B. Ernest, R. S. Singer, A. M. Pauli, H. Kinde, T. E. Rocke, and V. C. Bleich. 

2000. Desert bighorn sheep mortality due to presumptive type C botulism in California. Journal of Wildlife 

Diseases 36:184-189.

Van Devender, T. R. and M. A. Dimmitt. 2006. Final report on conservation of Arizona upland Sonoran Desert 

habitat: status and threats of buffelgrass (Pennisetum ciliare) in Arizona and Sonora. Arizona-Sonora Desert 

Museum, Tucson, AZ.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Warrick, G. D. and P. R. Krausman. 1989. Barrel cacti consumption by desert bighorn sheep. Southwestern 

Naturalist 34:483-486.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.
126 USDA Forest Service RMRS-GTR-284. 2012.

Sonoran Pronghorn

(Antilocapra americana sonoriensis)

SUMMARY

Vulnerability to drought mortality is a key issue for the Sonoran pronghorn, and associated risk will likely 

increase in the future. Impacts related to changes in phenology created high vulnerability to population 

declines with climate change. Natural resilience to droughts and fluctuations in resources is likely incurred 

by the pronghorn’s wide ranging habits, but movements of current populations are restricted by roads and 

fences. Effects of increased temperatures and more variable rainfall patterns will likely have detrimental 

effects on populations through changes in forage quantity and quality and increases in direct mortality, 

particularly to fawns. Improving this species’ ability to survive drought conditions will likely be critical to 

sustaining populations and will require a broad landscape view for management planning as vegetation 

changes and shifts, although uncertain, occur on a large scale.

VULNERABILITY Score Uncertainty

Habitat 2.1 14%

Physiology 1.7 33%

Phenology 2.5 25%

Interactions 2.0 40%

Overall 8.2 27%

Introduction

Pronghorns are the only members of their family, Antilocapridae. The subspecies, Sonoran pronghorn, was 

designated as Federally endangered in 1967. There is a semi-captive breeding population, and breeding stock 

has been translocated from Mexican populations (USFWS 2003). Population surveys conducted from 1992 to 

2000 showed a continuing declining trend (USFWS 2003). A population low of 20 animals was estimated for 

2002 and was blamed on low forage levels related to drought conditions. Sixty-eight Sonoran pronghorns was 

the estimated U.S. population for December 2008 (Sonoran Pronghorn Monthly Update, 20 January 2009). 

A five-year review of the status of the subspecies was initiated by the USFWS in 2008, but results were not 

available at the time of this report.

Three subpopulations of the subspecies exist, with one in the United States and the other two in Mexico 

where the species is also designated as endangered (USFWS 2003). Pronghorns mostly occur on the western 

half of BMGR (2003), but also extend into the west end of the eastern half of the Range as well. They also 

occur in the bordering Cabeza Prieta National Wildlife Refuge, Organ Pipe Cactus National Monument, and 

nearby Bureau of Land Management lands. Suitable pronghorn habitat is also available east of Highway 85 on 

BMGR-East but is not currently utilized (O’Brien and others 2005). 

-5 0 5

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0
USDA Forest Service RMRS-GTR-284. 2012. 127

BMGR-East Climate and Projections

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• CAM plants (succulents and cacti) will be resilient to increasing temperatures (Smith and others 1984)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main document.

Other Threats and Interactions with Climate

Numerous impacts have been proposed to have caused the low population size and continued declines in 

Sonoran pronghorn. Current populations are so small that any effect detrimental to survival or reproduction 

is critical to extinction vulnerability. USFWS (1998, 2003) suggested that important impacts include predation, 

forage availability, barriers to movement, and disease. Other known impacts include disturbance related to 

illegal border activity and military operations and competition with cattle. A recent study, however, found that 

pronghorn were mostly habituated to military overflights (Krausman and others 2004). Inbreeding and Allee 

effects are also potential threats in small populations.

Climate change will likely affect forage availability and quality, which have already been identified as 

influencing population fluctuations. Increasing variability in rainfall will cause parallel variability in forage, 

which could be especially damaging to these small populations in drought years. Fires also occur more 

frequently with increasing rainfall variability and increasing temperatures. Fires probably only reduce forage 

in the short term and generally increase vegetative growth in post-fire habitats. Interacting effects of fire 

with grass species, particularly those that are introduced, along with warmer temperatures will enhance 

grass forage, but grasses are generally not a large component of the diet (Buechner 1950). Increasing fires 

will threaten other essential habitat elements, including trees for thermal protection and chain-fruit cholla 

(Cylindropuntia fulgida) (and other succulents).

Research Needs

Impacts, both positive and negative, of wildlife waters are not well understood. Effectiveness of artificial 

waters and forage enhancement plots in mitigating detrimental impacts of drought on Sonoran pronghorn 

would be particularly applicable with future climate change. Risk of disease transmission at artificial waters 

needs to be explored. Because migration is speculated to improve the pronghorn’s ability to cope with 

changing conditions, an evaluation of the spatial and temporal variation in forage, interactions with climate, 

and current land use could provide important information on potential migration corridor enhancements. 

An assessment of habitat quality under drought conditions would also be helpful. Research on variables that 

affect predation rates and methods to reduce predation of captive-reared young could provide information for 

improving survival rates.
128 USDA Forest Service RMRS-GTR-284. 2012.

Management Implications

Although no recovery criteria or critical habitats have been established, recovery efforts suggested by the 

USFWS (2003) include: establish forage enhancement plots on BMGR, evaluate reliance on sources of free 

water, remove coyotes when and where pronghorns are most vulnerable, investigate transplant locations, 

increase aerial monitoring in Mexico, investigate disease vectors, reduce disturbance during critical periods, 

and reduce movement barriers. This climate change assessment identifies forage availability, water sources, 

disease vectors, and movement barriers as the most critical research needs. 

BMGR is closed to cattle grazing, which has minimized issues related to grazing competition and disease 

transmission. Some trespass grazing and grazing by feral burros occurs (BMGR 2003), but is unlikely to have 

significant or altered impacts unless there is increased contact that results in disease transmission such as 

through attraction to a localized water source. 

Management often restricts activities during periods when disturbance can have the greatest negative 

impacts, such as during breeding. The adjacent Cabeza Prieta National Wildlife Refuge institutes fawning 

season closures on March 15 to July 15. Changes in climate, however, are likely to alter breeding timing, 

particularly earlier, so closure dates should be reevaluated.

Although not currently a major threat at BMGR, fire and its interaction with introduced plants can significantly 

alter vegetation and may be an emerging issue that warrants monitoring. At least in the short term, fire 

promotes grasses over shrubs, shrubs being the preferred forage of Sonoran pronghorn. In addition, 

succulents, which are an important water source, are prone to fire mortality and often require shrubs as 

nursery plants for establishment, thus increasing recovery time following fires. Both of these resources are 

limited and may be important to pronghorn survival during drought periods. BMGR already has programs 

to control some invasive plants, and these efforts will be essential to protecting native habitats. Roadsides 

are likely locations where invasives can spread as they serve as corridors to seed transfer and provide water 

through run-off. Fire-prone invasive species should be included in control, and increased fire risk should be 

evaluated for critical pronghorn habitats such as those dominated by palo verde and cacti. 

Drought conditions, which are expected to increase, are limiting, thus management actions to mitigate 

drought conditions, such as water management, providing migration corridors, or forage enhancements, 

will be critical. Forage enhancement plots and wildlife waters are part of current management and should 

be evaluated for their ability to mitigate negative impacts of severe drought. Additional management should 

focus on desert trees, as these provide shade important for pronghorn survival during hot conditions. 

Although direct effects such as heat and disease may have negative impacts, changes in the quantity and 

quality of vegetation for forage will likely be the most important climate change impact on pronghorn 

populations. Shrubs and succulents are particularly valuable for survival. Projections for vegetation, however, 

are dependent on the interactions of complex factors such as fire and invasive grasses on current conditions, 

as well as on changes to seasonal precipitation, which are still difficult to predict with current climate models. 

Although it is unknown how vegetation will ultimately respond, it is likely that over a large area, there will be 

both beneficial and detrimental vegetation shifts for pronghorns. Management of populations therefore may 

best anticipate uncertain future changes by planning over a broad area, including lands adjacent to BMGR and 

particularly areas where droughts will have lower impact. These include areas that are currently inaccessible 

to pronghorn, thus enhancement of migration opportunities is essential to drought resilience. 
USDA Forest Service RMRS-GTR-284. 2012. 129

Habitat:	
  Sonoran	
  pronghorn	
  (Antilocapra	
  americana	
  sonoriensis)

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	
  southwestern	
  Arizona,	
  Sonoran	
  pronghorn	
  are	
  

associated	
  with	
  vegetation	
  such	
  as	
  big	
  galleta	
  grass,	
  

creosote	
  bush,	
  bursage,	
  and	
  saltbush.	
  Pronghorns	
  occupy	
  

similar	
  habitat	
  in	
  Sonora,	
  Mexico,	
  where	
  they	
  are	
  

associated	
  with	
  stable	
  sand	
  dunes	
  interspersed	
  with	
  

grasslands	
  (Hoffmeister	
  1986).	
  They	
  also	
  occur	
  in	
  

creosotebush-­‐bursage	
  habitat	
  year-­‐round	
  and	
  utilize	
  

areas	
  containing	
  palo	
  verde-­‐mixed	
  cacti	
  plant	
  

associations	
  in	
  spring	
  and	
  summer	
  (Federal	
  Register,	
  7	
  

September	
  1994,	
  p.	
  46266).	
  Sonoran	
  desert	
  habitats	
  are	
  

expected	
  to	
  expand	
  northward	
  in	
  the	
  United	
  States.

Expansion	
  areas	
  will	
  not	
  be	
  available	
  to	
  pronghorns	
  

because	
  of	
  roads	
  and	
  fences.

0

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.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Dense	
  shrubs	
  are	
  important	
  fawning	
  locations	
  for	
  

Antilocarpa	
  amercana	
  in	
  sagebrush	
  habitats	
  (Alldredge	
  

1994),	
  but	
  relationship	
  is	
  unknown	
  for	
  Sonoran	
  

populations.	
  Open	
  habitats	
  may	
  also	
  be	
  associated	
  with	
  

increased	
  survival	
  of	
  adults	
  as	
  predators	
  are	
  more	
  easily	
  

detected	
  and	
  avoided.	
  Palo	
  verde	
  is	
  drought	
  deciduous.	
  

Dry	
  conditions	
  and	
  fires	
  may	
  reduce	
  shrubs	
  or	
  shrub	
  

cover	
  with	
  mixed	
  results	
  for	
  breeding	
  success.	
  Likely	
  

depends	
  on	
  distribution	
  of	
  shrub	
  clumps,	
  but	
  distribution	
  

of	
  shrub	
  patches	
  is	
  difficult	
  to	
  project.

0

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?	
  

Washes	
  and	
  habitats	
  with	
  palo	
  verde	
  and	
  chain	
  fruit	
  

cholla	
  are	
  preferred	
  and	
  home	
  range	
  size	
  is	
  reduced	
  

compared	
  to	
  other	
  habitats	
  indicating	
  greater	
  habitat	
  

quality	
  (Hervert	
  and	
  others	
  2005).	
  Availability	
  of	
  free	
  

water	
  reportedly	
  is	
  a	
  critical	
  factor	
  (Hoffmeister	
  1986)	
  

and	
  pronghorns	
  are	
  known	
  to	
  drink	
  from	
  artificial	
  water	
  

sources	
  (Morgart	
  and	
  others 2005),	
  but	
  water	
  

requirements	
  are	
  not	
  well	
  known.	
  Requirement	
  of	
  free-­‐

standing	
  water	
  is	
  assumed	
  for	
  at	
  least	
  some	
  periods,	
  and	
  

availability	
  of	
  this	
  water	
  is	
  likely	
  to	
  decrease.

1

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Succulence	
  of	
  forage	
  has	
  been	
  suggested	
  as	
  a	
  measure	
  of	
  

habitat	
  quality	
  that	
  incurs	
  greater	
  reproductive	
  success	
  

(Kitchen	
  1974),	
  and	
  has	
  also	
  been	
  related	
  to	
  frequency	
  of	
  

drinking	
  (Beale	
  and	
  Smith	
  1970).	
  Drier	
  conditions	
  and	
  

reduction	
  in	
  natural	
  waters	
  are	
  projected.

Trees	
  provide	
  shade	
  for	
  survival	
  in	
  hot	
  weather.	
  Fires	
  

fueled	
  by	
  invasive	
  grasses	
  are	
  likely	
  to	
  be	
  detrimental	
  to	
  

shrubs	
  and	
  trees,	
  although	
  extent	
  of	
  this	
  increased	
  fire	
  

risk	
  at	
  BMGR	
  is	
  unknown.	
  In	
  addition,	
  starting	
  in	
  April,	
  

pronghorns	
  need	
  to	
  drink	
  water	
  because	
  they	
  switch	
  

from	
  forbs	
  to	
  shrub	
  forage.	
  

1
130 USDA Forest Service RMRS-GTR-284. 2012.

Habitat:	
  Sonoran	
  pronghorn	
  (Antilocapra	
  americana	
  sonoriensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Historically,	
  pronghorn	
  likely	
  moved	
  to	
  wetter	
  regions	
  

with	
  more	
  succulent	
  forage,	
  such	
  as	
  along	
  permanent	
  

rivers,	
  before	
  movements	
  were	
  limited	
  by	
  fences	
  and	
  

highways	
  (USFWS	
  2003).	
  Pronghorns	
  have	
  a	
  high	
  

capacity	
  to	
  disperse,	
  but	
  there	
  are	
  already	
  many	
  barriers	
  

to	
  dispersal.	
  Barriers	
  are	
  unlikely	
  to	
  be	
  reduced	
  with	
  

changes	
  in	
  climate	
  and	
  may	
  even	
  be	
  increased	
  with	
  

related	
  increases	
  in	
  border	
  activities	
  and	
  increasing	
  

human	
  populations.	
  Overall,	
  limited	
  ability	
  to	
  colonize	
  

new	
  areas.

1

7.	
  Migratory	
  

or	
  transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

No	
  transitional	
  habitats	
  known.

0

Physiology:	
  Sonoran	
  pronghorn	
  (Antilocapra	
  americana	
  sonoriensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  

Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  

to	
  change?

Generally	
  adapted	
  to	
  hot	
  and	
  dry	
  desert	
  conditions.	
  

Drought	
  has	
  been	
  implicated	
  in	
  mortality	
  due	
  directly	
  to	
  

heat	
  stress	
  or	
  indirectly	
  to	
  reduced	
  forage	
  (Bright	
  and	
  

Hervert	
  2005).	
  Young	
  may	
  also	
  be	
  prone	
  to	
  heat-­‐related	
  

mortality	
  above	
  40 °C	
  (Wilson	
  and	
  Krausman	
  2008).	
  

Hotter	
  temperatures	
  and	
  more	
  frequent	
  droughts	
  are	
  

predicted.

1

2.	
  Sex	
  ratio Is	
  sex	
  ratio	
  

determined	
  by	
  

temperature?	
  

No.

0

3.	
  Exposure	
  to	
  

weather-­‐

related	
  

disturbance

Are	
  disturbance	
  

events	
  (e.g.,	
  severe	
  

storms,	
  fires,	
  floods)	
  

that	
  affect	
  survival	
  or	
  

reproduction	
  

expected	
  to	
  change?	
  

No	
  known	
  effects	
  of	
  disturbance	
  events.

0

4.	
  Limitations	
  

to	
  daily	
  

activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Alternating	
  periods	
  of	
  feeding	
  and	
  rest	
  occur	
  throughout	
  

the	
  day,	
  with	
  fairly	
  continuous	
  feeding	
  in	
  the	
  early	
  

morning	
  and	
  late	
  afternoon,	
  and	
  longer	
  rest	
  periods	
  at	
  

night	
  (Davis	
  1974).	
  They	
  have	
  both	
  nocturnal	
  and	
  diurnal	
  

activities	
  with	
  peaks	
  at	
  dawn	
  and	
  dusk,	
  particularly	
  

during	
  hot	
  periods	
  (Buechner	
  1950;	
  Kitchen	
  1974).	
  

Reduce	
  activities	
  during	
  hot	
  parts	
  of	
  the	
  day	
  in	
  summer	
  

and	
  winter,	
  compensating	
  with	
  a	
  switch	
  to	
  more	
  activity	
  

during	
  crepuscular	
  periods	
  (Wilson	
  2009).	
  This	
  flexibility	
  

in	
  behavior	
  may	
  limit	
  reductions	
  in	
  activity	
  periods	
  

associated	
  with	
  climate,	
  although	
  relationship	
  is	
  not	
  well	
  

known.

0
USDA Forest Service RMRS-GTR-284. 2012. 131

Physiology:	
  Sonoran	
  pronghorn	
  (Antilocapra	
  americana	
  sonoriensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

5.	
  Survival	
  

during	
  

resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Probably	
  initiate	
  migration	
  to	
  other	
  areas	
  to	
  cope	
  with	
  

changing	
  resources,	
  but	
  migratory	
  behavior	
  is	
  now	
  

considerably	
  limited	
  by	
  fences	
  and	
  roads. 1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic. 0

	
  	
  	
  	
  	
  	
  	
  	
  	
  

Phenology:	
  Sonoran	
  pronghorn	
  (Antilocapra	
  americana	
  sonoriensis)

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	
  (e.g.,

hibernation,	
  

migration,	
  breeding)?

Not	
  known	
  what	
  triggers	
  breeding.	
  Earlier	
  timing	
  in	
  

Sonoran	
  populations	
  is	
  a	
  significant	
  difference	
  from	
  

northern	
  populations.	
  Although	
  breeding	
  timing	
  may	
  be	
  

sensitive	
  to	
  temperature	
  or	
  moisture,	
  they	
  may	
  not	
  be	
  

direct	
  cues. 0

2.	
  Breeding	
  

timing

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?

Rainfall	
  events	
  are	
  likely	
  important	
  in	
  fawn	
  survival,	
  so	
  it	
  

is	
  likely	
  that	
  timing	
  of	
  breeding	
  to	
  these	
  events	
  is	
  

important.	
  In	
  addition,	
  starting	
  in	
  April,	
  pronghorns	
  need	
  

to	
  drink	
  water,	
  because	
  they	
  switch	
  from	
  forbs	
  to	
  shrub	
  

forage	
  (Wilson	
  2009).

Rainfall	
  quantity	
  and	
  timing	
  is	
  likely	
  to	
  become	
  more	
  

variable.

1

3.	
  Mismatch	
  

potential

What	
  is	
  the	
  

separation	
  in	
  time	
  or	
  

space	
  between	
  cues	
  

that	
  initiate	
  activities	
  

related	
  to	
  survival	
  or	
  

fecundity	
  and	
  discrete	
  

events	
  that	
  provide	
  

critical	
  resources?

Breeding	
  is	
  separated	
  in	
  time	
  from	
  fawning	
  to	
  some	
  

extent.	
  Fawn	
  survival	
  is	
  dependent	
  on	
  predator	
  levels	
  and	
  

mortality	
  has	
  been	
  linked	
  to	
  drought;	
  thus,	
  successful	
  

timing	
  may	
  relate	
  to	
  precipitation	
  and/or	
  predator	
  

populations,	
  which	
  cannot	
  be	
  adjusted	
  for.	
  No	
  strong	
  

probability	
  of	
  mismatch,	
  but	
  no	
  particular	
  traits	
  to	
  reduce	
  

mismatch	
  in	
  timing	
  either.

0

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  breeding	
  event	
  per	
  year	
  or	
  less.

1
132 USDA Forest Service RMRS-GTR-284. 2012.

Biotic	
  Interactions:	
  Sonoran	
  pronghorn	
  (Antilocapra	
  americana	
  sonoriensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Sonoran	
  pronghorns	
  eat	
  a	
  variety	
  of	
  desert	
  plants,

including	
  cacti,	
  pigweed	
  (Amaranthus	
  palmeri),	
  ragweed	
  

(Ambrosia	
  sp.),	
  locoweed	
  (Astragalus	
  sp.),	
  brome	
  (Bromus	
  

sp.),	
  and	
  snakeweed	
  (Gutierrezia	
  sarothrae)	
  (USFWS	
  

1998).	
  Grass	
  is	
  only	
  a	
  minor	
  component	
  of	
  the	
  pronghorn	
  

diet	
  (Buechner	
  1950).	
  In	
  addition,	
  Sonoran	
  pronghorns	
  

are	
  known	
  to	
  switch	
  preferred	
  forage	
  species	
  with	
  

variations	
  in	
  climate	
  (deVos	
  and	
  Miller	
  2005;	
  Hervert	
  and	
  

others	
  2005).	
  Cacti,	
  and	
  in	
  particular	
  chain	
  fruit	
  cholla	
  

(Cylindropuntia	
  fulgida),	
  provide	
  a	
  source	
  of	
  water	
  

(Pinkava	
  1999)	
  and	
  are	
  important	
  during	
  hot	
  and	
  dry	
  

conditions	
  (Hervert	
  and	
  others 1997).	
  During	
  droughts,	
  

cacti	
  are	
  a	
  major	
  component	
  of	
  the	
  diet	
  (Hughes	
  and	
  

Smith	
  1990).

Greater	
  variability	
  in	
  rainfall	
  will	
  increase	
  forage	
  

availability	
  in	
  some	
  years,	
  but	
  drought	
  periods	
  will	
  reduce	
  

forage.	
  Fires	
  may	
  increase	
  cover	
  of	
  grass,	
  but	
  grass	
  is	
  only	
  

a	
  minor	
  forage	
  component.	
  Cacti	
  are	
  an	
  important	
  

component	
  of	
  forage	
  during	
  drought	
  periods	
  and	
  are	
  

resistant	
  to	
  drought	
  although	
  water	
  content	
  will	
  be	
  

reduced.	
  Overall	
  reductions	
  predicted.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

In	
  American	
  pronghorn	
  (A.	
  a.	
  americana),	
  coyotes	
  did	
  not	
  

depredate	
  adults,	
  but	
  could	
  successfully	
  kill	
  fawns	
  up	
  to	
  

45	
  days	
  old	
  (Byers	
  1997).	
  Young	
  pronghorn	
  raised	
  from	
  

captivity	
  and	
  released,	
  however,	
  seem	
  to	
  be	
  vulnerable	
  

and	
  are	
  often	
  killed	
  by	
  coyotes.	
  There	
  is	
  evidence	
  of	
  

predation	
  by	
  coyotes,	
  bobcats,	
  and	
  mountain	
  lions.	
  Coyote	
  

populations	
  are	
  likely	
  somewhat	
  resilient	
  to	
  changes	
  in	
  

climate	
  given	
  their	
  wide	
  range	
  of	
  tolerances	
  and	
  prey	
  

species.	
  Predation	
  rates	
  are	
  high	
  and	
  may	
  not	
  be	
  expected	
  

to	
  increase	
  significantly.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  

in	
  this	
  species	
  

expected	
  to	
  change?	
  

Testing	
  of	
  individuals	
  revealed	
  presence	
  of	
  bluetongue	
  

and	
  epizootic	
  hemorrhagic	
  disease,	
  which	
  are	
  both	
  

potentially	
  fatal	
  (USFWS	
  2003).	
  Biting	
  midges (Culicoides

spp.)	
  are	
  suspected	
  as	
  the	
  vector	
  for	
  these	
  diseases	
  and	
  

breed	
  in	
  wet	
  areas.	
  Bluetongue	
  is	
  also	
  transmitted	
  to	
  

pronghorn	
  from	
  cattle	
  (USFWS	
  1998).	
  Increasing	
  reliance	
  

of	
  water	
  sources	
  where	
  biting	
  midges	
  (vectors)	
  breed	
  and	
  

increased	
  attraction	
  to	
  those	
  areas	
  due	
  to	
  water	
  

limitations	
  may	
  increase	
  bluetongue	
  infection	
  rates.

1

5.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Competition	
  is	
  strong	
  with	
  domestic	
  sheep	
  and	
  weaker	
  

with	
  cattle	
  (Buechner	
  1950).	
  Cattle	
  eat	
  some	
  forbs	
  and	
  

other	
  browse	
  species	
  that	
  are	
  preferred	
  by	
  pronghorns,	
  

but	
  pronghorns	
  seem	
  to	
  represent	
  little	
  competition	
  as	
  

grasses	
  preferred	
  by	
  cattle	
  comprise	
  only	
  a	
  small	
  

proportion	
  of	
  their	
  diet	
  (Buechner	
  1950).	
  Although	
  

pronghorn	
  have	
  been	
  observed	
  to	
  be	
  able	
  to	
  sustain	
  

populations	
  on	
  overgrazed	
  cattle	
  lands	
  (Buechner	
  1950),	
  

cattle	
  may	
  present	
  more	
  of	
  a	
  competitive	
  problem	
  

(Yoakum	
  2004).	
  Cattle	
  and	
  domestic	
  sheep	
  are	
  usually	
  not	
  

present	
  on	
  BMGR.	
  Interactions	
  with	
  other	
  ungulates	
  are	
  

likely	
  limited.

0
USDA Forest Service RMRS-GTR-284. 2012. 133

Literature Cited

Alldredge, A. W., R. D. Deblinger, and J. Peterson. 1991. Birth and fawn bed site selection by pronghorns in a 

sagebrush-steppe community. Journal of Wildlife Management 55:222-227.

Bagne, K. E., M. M. Friggens, and D. M. Finch. 2011. A system for assessing vulnerability of species (SAVS) to 

climate change. USDA Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. RMRS-GTR-257.

Barry M. Goldwater Range (BMGR). 2003. Proposed integrated natural resources management plan: draft EIS. 

Departments of the Air Force, Navy, and Interior, Arizona.

Beale, D. and A. Smith. 1970. Forage use, water consumption, and productivity of pronghorn antelope in 

western Utah. Journal of Wildlife Management 34:570-582.

Bowers, J. E. and R. M. Turner. 2001. Dieback and episodic mortality of Cercidium microphyllum (foothill 

paloverde), a dominant Sonoran Desert tree. Journal of the Torrey Botanical Society 128:128-140.

Bright, J. L. and J. J. Hervert. 2005. Adult and fawn mortality of Sonoran pronghorn. Wildlife Society Bulletin 

33(1):43-50.

Buechner, H. K. 1950. Life history, ecology, and range use of the pronghorn antelope in Trans-Pecos Texas. 

American Midland Naturalist 43:257-354.

deVos, J. C. and W. H. Miller. 2005. Habitat use and survival of Sonoran pronghorn in years with above-average 

rainfall. Wildlife Society Bulletin 33:35-42.

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Fox, L. M., P. R. Krausman, M. L. Morrison, and R. M. Kattnig. 2000. Water and nutrient content of forage in 

Sonoran pronghorn habitat, Arizona. California Fish and Game 86(4):216-232.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17. 

Hervert, J. J., J. L. Bright, R. S. Henry, L. A. Piest, and M. T. Brown. 2005. Home-range and habitat-use patterns 

of Sonoran pronghorn in Arizona. Wildlife Society Bulletin 33:8-15.

Hoffmeister, D. F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish Dept. 

602 p.

Hughes, K. S. and N. S. Smith. 1990. Sonoran pronghorn use of habitat in Southwest Arizona. Report to Cabeza 

Prieta National Wildlife Refuge, Ajo, AZ.

Kitchen, D. W. 1974. Social behavior and ecology of the pronghorn. Wildlife Monographs 38:3-96.

Krausman, P. R., L. K. Harris, C. L. Blasch, K. K. G. Koenen, and J. Francine. 2004. Effects of military operations 

on behavior and hearing of endangered Sonoran pronghorn. Wildlife Monographs 157:1-41.

Liverman, D. M. and K. L. O’Brien. 1991. Global warming and climate change in Mexico. Pages 351-364 in 

Global Environmental Change. Butterworth-Heinemann Ltd.

McLaughlin, S. E. and J. P. Bowers. 1982. Effects of wildfire on a Sonoran Desert plant community. Ecology 

63:246-248.

McPherson, G. R. and J. F. Weltzin. 2000. Disturbance and climate change in United States/Mexico borderland 

plant communities: a state-of-the-knowledge review. USDA Forest Service, Rocky Mountain Research 

Station, Gen. Tech. Rep. RMRS-GTR-50.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Morgart, J. R., J. J. Hervert, P. R. Krausman, J. L. Bright, and R. S. Henry. 2005. Sonoran pronghorn use of 

anthropogenic and natural waters. Wildlife Society Bulletin 33:51-60.

Pinkava, D. J. 1999. Cactaceae cactus family, part three, Cylindropuntia. Journal of the Arizona-Nevada 

Academy of Science 32(1):32-47.
134 USDA Forest Service RMRS-GTR-284. 2012.

O’Brien, C., S. Rosenstock, J. Hervert, J. Bright, and S. Boe. 2005. Landscape-level models of potential habitat 

for Sonoran pronghorn. Wildlife Society Bulletin 33:24-34.

Seager, R., T. Ming, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Swetnam, T. W. and J. L Betancourt. 1990. Fire-southern oscillation relations in the southwestern United 

States. Science 249:1017-1020.

U.S. Fish and Wildlife Service (USFWS). 1998. Recovery criteria and estimates of time for recovery actions for 

the Sonoran pronghorn. U.S. Fish and Wildlife Service, Region 2, Albuquerque, NM. 

U.S. Fish and Wildlife Service (USFWS). 2003. Supplement and amendment to the 1998 final revised Sonoran 

pronghorn recovery plan (Antilocapra americana sonoriensis). U.S. Fish and Wildlife Service, Albuquerque, 

NM.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140.

Wilson, R. R. and P. R. Krausman. 2008. Possibility of heat-related mortality in desert ungulates. Journal of the 

Arizona-Nevada Academy of Science 40:12-15. 

Wilson, R. R., P. R. Krausman, and J. R. Morgart. 2009. Behavior and activity budgets of Sonoran pronghorns 

(Antilocapra americana sonoriensis). Southwestern Naturalist 54:45-54. 

Yoakum, J. 2004. Management plans, environmental impact statements and guides. Pages 541-569 In B. W. 

O’Gara and J. D. Yoakum, eds., Pronghorn Ecology and Management. University Press of Colorado, Boulder.
USDA Forest Service RMRS-GTR-284. 2012. 135

Acuña Cactus

(Echinomastus erectrocentrus var. acunensis)

SUMMARY

Acuña cactus is vulnerable to declines associated with future climate change. Although well adapted to hot 

temperatures and limited water, increasing fires and possible declines in animal dispersers and pollinators are 

likely to be detrimental. Management that addresses fire risk and improves conditions for recruitment will be 

important for sustaining populations.

VULNERABILITY Score Uncertainty

Habitat 1.5 25%

Physiology -1.0 33%

Interactions 2.0 33%

Overall 2.8 30%

Introduction

Acuña cactus is a candidate for listing as a Federally endangered or threatened species and may occur on 

BMGR. It is restricted to knolls and gravel ridges between major washes in Sonoran desertscrub habitat. 

Nearby populations are reported from the Sand Tank and Sauceda Mountains on lands administered by the 

Bureau of Land Management, as well as Organ Pipe Cactus National Monument (CBD 2002).

BMGR-East Climate Projections Used for Assessment

• Annual increase in temperature 2.2 °C (4 °F) by 2050 (www.climatewizard.org, A2 emissions, ensembled 

GCM) and greater evaporation

• No change in average rainfall by 2050 (www.climatewizard.org, A2 emissions, ensembled GCM)

• Sonoran Desert expands northward and eastward, and contracts in the southeast (Weiss and Overpeck 

2005)

• More droughts and intense storms (Seager and others 2007)

• Earlier and more intense flooding (Garfin and Lenart 2007; Seager and others 2007)

• Summer monsoon changes unknown (Mitchell and others 2002)

• Grasses favored over shrubs (Esser 1992)

• Increases in invasive grasses and fires (Esser 1992; Williams and Baruch 2000)

A detailed review of projections is in the “Projections of Climate, Disturbance, and Biotic Communities” 

section of the main text.

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

certain

Least 

certain

More 

vulnerable

More 

resilient 0

-3 0 3
136 USDA Forest Service RMRS-GTR-284. 2012.

Other Threats and Interactions with Climate Change

Threats identified by USFWS are grazing, collection, mining, recreation, and land development (CBD 2002). 

Acuña cactus populations may be declining at the nearby Organ Pipe Cactus National Monument (CBD 2002). 

Reasons for decline in this protected population are unclear; perhaps natural limiting factors have been 

exacerbated by dry conditions. For example, impacts from native grazers and insect borers may increase 

during dry years. In addition, seed germination can depend on temperature, innate dormancy, light, and 

ingestion by animals (Rojas-Aréchiga and Vázquez-Yanes 2000). None of these threats is likely a major concern 

on BMGR except perhaps off-highway vehicle use. Illegal immigrant traffic and associated border patrol 

activities may similarly threaten populations.

Johnson (1992) found the number of flowers produced annually to be positively correlated with annual 

rainfall. Water storage or cactus volume was also correlated with flowering, further indicating that flowering is 

limited by water availability (Johnson 1992). Furthermore, germination may be highest following monsoonal 

rains (Johnson 1993). Monsoonal rain is important and, although not well projected into the future, it is 

expected that rainfall timing will shift. There should still be some years with adequate rainfall for recruitment, 

although conditions for germination and seedling survival are not well known.

One of the largest threats on Federal lands may be the interaction of invasive grass species with fire, a threat 

also noted in the petition to list the species as endangered (CBD 2002). Invasive grasses such as buffelgrass 

(Pennisetum ciliare) encourage frequent, high intensity fires that convert desert scrub to grasslands and do 

not allow desert species time to recover. More arid locations may be expected to support a different fire 

regime. Higher fuel loads associated with the introduced buffelgrass increase fire intensity and may result in 

much higher initial mortality. More importantly, invasion by these grasses rather than just the occasional high 

fuel loads that occur following heavy rainfall years can change fire regimes to ones that are not compatible 

with many desert plants.

Research Needs

Limiting factors are unknown and need to be evaluated, as protected populations seem to be in decline. 

Conditions favorable to recruitment will be important and can help inform management related to habitat 

enhancement, restoration, or post-fire rehabilitation. An assessment of fire risk could also identify needs and 

target areas for management.

Management Implications

Potential for occurrence of acuña cactus on lands managed as part of BMGR should be evaluated. 

Management related to fire risk will be important, at least in some locations. Fire threat will depend on 

various factors, including topography, surrounding vegetation, proximity to introduced grasses, and soils. 

Invasive grasses can also compete for water and should be controlled in the vicinity of cactus populations. 

Acuña cactus should also be included in post-fire planning. Protection of multiple populations will be 

important for this species as drought and other stresses may result in local population extinctions.
USDA Forest Service RMRS-GTR-284. 2012. 137

Habitat:	
  Acuña	
  cactus	
  (Echinomastus	
  erectrocentrus	
  var.	
  acunensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Increased	
  

droughts	
  and	
  

warming.

Is	
  this	
  species	
  

associated	
  with	
  

wetlands,	
  riparian	
  

areas,	
  or	
  other	
  mesic	
  

environments	
  

expected	
  to	
  decline?

No. Acuña	
  cactus	
  occur	
  on	
  well-­‐drained	
  granite	
  

substrates	
  on	
  knolls	
  at	
  elevations	
  ranging	
  

from	
  397-­‐610	
  m	
  (1300-­‐2000	
  ft)	
  (CBD	
  2002). 0

2.	
  Habitat	
  

elements

Does	
  this	
  species	
  

require	
  specialized	
  

microsites?

Isolated	
  by	
  occurrence	
  on	
  specialized	
  soil	
  types	
  (CBD	
  

2002). 1

3	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  this	
  species	
  

dispersal	
  ability?

Cactus	
  seeds	
  or	
  fruit	
  are	
  transported	
  by	
  animals,

including	
  ants	
  (Rojas-­‐Aréchiga	
  and	
  Vázquez-­‐Yanes	
  2000).	
  

Dispersal	
  will	
  depend	
  on	
  climate	
  change	
  effects	
  on	
  these	
  

species.

1

4.	
  Seedling	
  

conditions

Do	
  seedlings	
  require	
  

different	
  conditions	
  

from	
  mature	
  

individuals	
  (shade,	
  

moisture,	
  fires,	
  nurse	
  

plants,	
  etc)?

Various	
  conditions	
  that	
  improve	
  microsite	
  moisture	
  have	
  

been	
  associated	
  with	
  cactus	
  germination,	
  including	
  nurse	
  

plants	
  and	
  rocks	
  (Rojas-­‐Aréchiga	
  and	
  Carlos	
  Vázquez-­‐

Yanes	
  2000).	
  No	
  information	
  found	
  for	
  this	
  species,	
  but	
  

rocky	
  habitats	
  may	
  fulfill	
  this	
  function.	
  No	
  expected	
  

change.

0

Physiology:	
  Acuña	
  cactus	
  (Echinomastus	
  erectrocentrus var.	
  acunensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Exposure	
  to	
  

disturbance

Are	
  disturbance	
  

events	
  that	
  result	
  in	
  

direct	
  mortality	
  or	
  

reproductive	
  failure	
  

expected	
  to	
  change?	
  

Although	
  many	
  cacti	
  may	
  live	
  through	
  wildfires	
  in	
  semi-­‐

desert	
  grasslands,	
  annual	
  mortality	
  for	
  many	
  species	
  is	
  

increased	
  and	
  may	
  be	
  more	
  important	
  than	
  short-­‐term	
  

effects	
  (Thomas	
  2006).	
  Fires	
  are	
  expected	
  to	
  increase.

1

2.	
  Adaptations	
  

to	
  survive	
  

water	
  

limitations

Does	
  this	
  species	
  

possess	
  adaptations	
  

to	
  increase	
  survival	
  

during	
  droughts	
  (i.c.,	
  

waxy	
  leaves,	
  water	
  

storage,	
  cavitation,	
  

drought	
  deciduous)?

Yes.	
  Cactus	
  have	
  specialized	
  adaptations	
  for	
  dry	
  

conditions.

-­1

3.	
  

Photosynthetic	
  

pathway

Which	
  

photosynthetic	
  

pathway	
  does	
  this	
  

species	
  use?

CAM.

-­1
138 USDA Forest Service RMRS-GTR-284. 2012.

Interactions:	
  Acuña	
  cactus	
  (Echinomastus	
  erectrocentrus	
  var.	
  acunensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Pollination What	
  is	
  the	
  

pollination	
  vector?

Flowers	
  are	
  self-­‐incompatible	
  and	
  insect	
  pollinators	
  are	
  

required.	
  Insect	
  pollinators	
  were	
  mostly	
  solitary	
  bees	
  

from	
  the	
  family	
  Anthophoridae	
  (Johnson	
  1992).

1

2.	
  Disease	
   Any	
  known	
  

diseases/parasites	
  

that	
  result	
  in	
  mass	
  

mortality	
  related	
  to	
  

temperature	
  or	
  

precipitation?	
  

Not	
  known	
  for	
  this	
  species.

0

3.	
  

Competitors

Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Hedgehog	
  cactus	
  flowering	
  was	
  not	
  found	
  to	
  interfere	
  

with	
  pollination	
  of	
  this	
  species	
  (Johnson	
  1992).	
  May	
  

compete	
  for	
  water	
  with	
  grasses.	
  Grasses	
  expected	
  to	
  

increase	
  in	
  some	
  areas.

1
USDA Forest Service RMRS-GTR-284. 2012. 139

Literature Cited

Center for Biological Diversity (CBD). 2002. Petition to list the acuña cactus as endangered. Unpublished 

report. 

Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous 

forests. Ecological Applications 2:47-54.

Garfin, G. and M. Lenart. 2007. Climate change effects on Southwest water resources. Southwest Hydrology 

6:16-17. 

Johnson, R. A. 1992. Pollination and reproductive ecology of acuña cactus, Echinomastus erectrocentrus var. 

acunensis (Cactaceae). International Journal of Plant Science 153:400-408. 

Johnson, R. A., M. A. Baker, D. J. Pinkava, and G.A. Ruffner. 1993. Seedling establishment, mortality, growth, 

and flower production in acuña cactus, Ecinomastus erectrocentrus var. acunensis. Pages 170-180 in 

R.Sivinski and K. Lightfoot, eds., Proceedings of the Southwestern Rare and Endangered Plant Conference, 

Santa Fe, NM.

Mitchell, D. L., D. Ivanova, R. Rabin, K. Redmond, and T. J. Brown. 2002. Gulf of California sea surface 

temperatures and the North American monsoon: mechanistic implications from observations. Journal of 

Climate 15:2261-2281.

Rojas-Aréchiga, M. and C. Vázquez-Yanes. 2000. Cactus seed germination: a review. Journal of Arid 

Environments 44:85-104.

Seager, R., T. Mingfang, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

climate in southwestern North America. Science 316:1181-1184.

Thomas, P. A. 2006. Mortality over 16 years of cacti in a burnt desert grassland. Plant Ecology 183:9-17.

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065-

2077.

Williams, D. G. and Z. Baruch. 2000. African grass invasion in the Americas: ecosystem consequences and the 

role of ecophysiology. Biological Invasions 2:213-140. 
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