United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

General Technical 

Report RMRS-GTR-302

June 2013

Vulnerability of Species to Climate Change in the 

Southwest: Threatened, Endangered, and At-Risk 

Species at Fort Huachuca, Arizona

Karen E. Bagne and Deborah M. Finch
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Bagne, Karen E.; Finch, Deborah M. 2013. Vulnerability of species to climate 

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

Huachuca, Arizona. Gen. Tech. Rep. RMRS-GTR-302. Fort Collins, CO: U.S. 

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

183 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, a vulnerability scoring tool based on 

ecological principles, to rank individual species of interest within the Fort Huachuca 

region 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. Based solely on predicted response to climate change, 

northern Mexican gartersnake and southwestern willow flycatcher are the most 

vulnerable to population declines. Results also suggest that climate change will make 

management of some TER-S 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 intense flooding. The 

assessment process was also used to identify areas where climate change may present 

opportunities, as opposed to challenges, for management of TER-S.

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

SAVS

Authors

Karen E. Bagne is a Wildlife Ecologist employed through an agreement 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 photos: (clockwise from top) West Range, Fort Huachuca, Arizona. (Photo 

by Pam Landin.) Huachuca water umbel, Cochise County, Arizona. (Photo by Pam 

Landin.) Mexican spotted owl, Fort Huachuca, Arizona. (Photo by Colby Henley.) 

Chiricahua leopard frog, Cochise County, Arizona. (Photo by Pam Landin.) 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...........................................................................................................6

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

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

Scoring Results..............................................................................................9

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

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

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

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

Artificial and Natural Waters................................................................................15

Anticipating Shifts in Distribution.........................................................................17

Coping With Physiological Thresholds................................................................18

Anticipating Shifts in Timing ................................................................................18

Prioritization ........................................................................................................18

Landscape-Scale Management and Partners.....................................................19

Uncertainty..........................................................................................................19

Next Steps.....................................................................................................19

Literature Cited.............................................................................................20

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

Amphibians

Sonoran tiger salamander...................................................................................26

Western barking frog...........................................................................................33

Chiricahua leopard frog.......................................................................................39

Arizona treefrog...................................................................................................49

Reptiles

Desert ;massasauga ...........................................................................................56

Arizona ridge-nosed rattlesnake .........................................................................63

Northern Mexican gartersnake............................................................................69

Birds

Bald eagle ...........................................................................................................75

Northern goshawk...............................................................................................81

Northern aplomado falcon...................................................................................87

American peregrine falcon ..................................................................................94

Western yellow-billed cuckoo............................................................................100

Mexican spotted owl..........................................................................................109

Elegant trogon...................................................................................................116

Southwestern willow flycatcher .........................................................................124

Northern buff-breasted flycatcher......................................................................132

Mammals

Arizona shrew ...................................................................................................138

Cave myotis ......................................................................................................144

Lesser long-nosed bat.......................................................................................150

Mexican long-tongued bat.................................................................................161

Black-tailed prairie dog......................................................................................168

Plants

Huachuca water umbel .....................................................................................174

Lemmon fleabane .............................................................................................179
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. Megan Friggens and Sharon Coe, Rocky Mountain Research Station, provided 

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

We thank Sheridan Stone of Fort Huachuca Army Installation and Glenn Frederick 

of Bureau of Land Management for comments that improved the 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, Region 

3. Mary Bagne provided editing assistance.
USDA Forest Service RMRS-GTR-302. 2013. 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. They also contain large numbers of species at risk—those that 

are imperiled but not yet listed by the U.S. Fish and Wildlife Service (USFWS) 

(NatureServe 2004). These species, also known as TER-S (threatened, endangered, 

and at-risk species), are an important element of natural resources 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). Six threatened or endangered terrestrial vertebrate 

species and one endangered plant species are known to occur or potentially occur 

at the Fort Huachuca Army Installation in southeastern Arizona (ENRD 2006). 

Fort Huachuca is also among the top 20 DoD installations for highest numbers of 

species at risk (NatureServe 2004).

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 will experience negative impacts from 

climate change.

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

the potential to exacerbate existing management issues while creating 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 Stein 2010). 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 
2 USDA Forest Service RMRS-GTR-302. 2013.

uninterrupted military operations with cost-effective natural resource management. Resources for management are also limited, thus priority targets and actions 

need to be identified (see Box 1). This assessment addresses the vulnerability of 

individual TER-S to population declines associated with projected changes in climate at Fort Huachuca in southeastern Arizona. Species are ranked by anticipated 

vulnerability, and potential management actions are identified based on the specific vulnerabilities identified. 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; and 

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 a key component of prediction but is 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-302. 2013. 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 made 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 within 

the next 50 years or less. Although scores are limited to the region, they are also 

generally applicable to adjacent lands to Fort Huachuca. The specific projections 

used follow this section.

We assessed species with known occurrence at Fort Huachuca listed by the 

USFWS as endangered or threatened. We included additional species that are either 

proposed for Federal listing, Federal species of concern, or of high conservation 

priority for Arizona as identified by the State Wildlife Action Plan (AGFD 2006). 

Only one plant species on Fort Huachuca was Federally listed: the endangered 

Huachuca water umbel (Lilaeopsis schaffneriana var. recurva) (Figure 1). One 

species, the willow flycatcher (Empidonax trailii extimus), that occurs adjacent 

to but not on the Fort was included along with three species for which there are 

no recent records: the desert massasauga (Sistrurus catenatus edwardsi), northern 

aplomado falcon (Falco femoralis septentrionalis), and the black-tailed prairie dog 

(Cynomys ludovicianus). Prioritization and identification of vulnerabilities are presented separately for vertebrates and plants.

Figure 1. The Huachuca water umbel 

only occurs in a few locations, 

placing it at a greater threat to 

extinction with population declines. 

Photo credit: B. Radke, USFWS.
4 USDA Forest Service RMRS-GTR-302. 2013.

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). The current climate at Fort Huachuca 

is dry with warm summers and mild winters. Recorded temperatures already indicate that the region is warming at a rate unprecedented in the last 400 years 

(Sheppard and others 2002). With increasing levels of CO2, temperatures are expected to rise in southeastern Arizona. Average annual temperature is expected to 

increase approximately 2.2 °C or 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).

Rain falls in the summer and winter with the majority (~60%) arriving during summer monsoons for an average annual rainfall of 38 cm (ENRD 2006). 

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. Monsoon patterns in this subregion 

differ from monsoons to the east in New Mexico, which come earlier, and monsoons to the south in Mexico, which 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 and spring rain is reduced 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). However, even with no change in rainfall, predicted higher temperatures 

will increase evaporation, which will result in less available moisture for plants 

and animals. 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 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.
USDA Forest Service RMRS-GTR-302. 2013. 5

Water Sources

The Fort has mostly ephemeral streams that only flow during significant precipitation events. The perennial reaches are in Garden and Huachuca Canyons, though 

there are minor perennial reaches elsewhere. Flows are generally lowest in early 

spring before the summer monsoons arrive. Since 1930, this spring dry period has 

started earlier and lasted longer. These changes have been attributed to climate 

factors, such as earlier snow melt, and to changes in upland vegetation (ENRD 

2006). The major perennial stream in the region is the San Pedro River, which is 

located outside the Fort boundaries (ENRD 2006). Stream flow simulations for 

the San Pedro River based on multiple climate models show significant decrease 

in base flows and alteration of riparian habitats even while keeping ground water 

extraction at current levels (Serrat-Capdevila and others 2007). Climate factors 

reducing stream flow on the San Pedro will likely affect streams on Fort Huachuca 

similarly. Decisions related to the amount and location of ground water withdrawals, both locally and from nearby communities, will affect future surface waters 

on Fort Huachuca, but increased demand from growing populations along with the 

current depression of the water table under the Fort and Sierra Vista points toward 

continued depletion of the aquifer (ENRD 2006).

Surface water is largely dependent on local rainfall and thus subject to considerable alteration as climate warms and circulation patterns change. Shallow 

water sources, such as ponds and pools, will be particularly vulnerable to drying. 

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. Changes in vegetation influencing soil infiltration, such as 

root depth or cover, can further alter surface water and adds to the complexity of 

projections.

Figure 2. North American monsoon subregions and monthly 

precipitation patterns. (Comrie and Glenn 1998).
6 USDA Forest Service RMRS-GTR-302. 2013.

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 these events may increase soil water availability for 

xeric ones (Knapp and others 2008), which adds to the problems associated with 

predicting species’ responses to climate change.

Wildfires are expected to become more frequent with projected increases in 

temperature (Rogers and Vint 1987; Swetnam and Betancourt 1990; Esser 1992; 

Westerling and others 2006). In addition to temperature interactions, projected increases in climate variability will also increase fire occurrence as years of high 

rainfall are followed by dry/hot years creating 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

There is considerable topographic variation on the Fort and, consequently, a 

variety of vegetation types and environmental conditions. Lower elevations at Fort 

Huachuca are dominated by Chihuahuan desert scrublands and open scrub-grasslands (ENRD 2006). Higher elevations are primarily Madrean oak and oak-pine 

woodlands (ENRD 2006). Riparian deciduous forest and montane conifer are also 

present and, although they cover a relatively small area of Fort Huachuca, these 

vegetation types are important to regional biodiversity. Future vegetation will 

depend on the quantity and season of precipitation, which is currently not well 

modeled, as well as the interaction of other factors such as fire, grazing, soils, and 

topography (McPherson and Weltzin 2000). Regardless, climate change is likely to 

result in widespread disruption of present biotic communities (Figure 3; Rehfeldt 

and others 2006). Ignoring small-scale variation not captured by these models, 

there is a strong tendency toward homogenization of a diverse set of communities 

toward a single climate regime currently associated with desert grasslands. This 

does not mean that all habitats will necessarily be replaced by desert grasslands, 

but that environmental conditions will favor desert grassland across an expanding 

area while other communities will experience conditions outside those they are 

currently associated with. Because different species vary in their tolerances, new 

mixes of species or novel species assemblages will likely result.

The relative dominance of shrubs (primarily C3) versus grasses (primarily C4) 

with climate change remains uncertain (McPherson and Weltzin 2000). C3 shrubs 

are favored by increases in CO2 and grazing and may be expected to remain dominant in many areas where they are already established (Archer and others 1995). 

Alternatively, C4 grasses may be favored by increases in temperature and more 

frequent fire occurrence (Esser 1992). 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 

may induce recurring shifts between grasslands and shrublands, although shrubs 

will take longer to reestablish after disturbance. In corraboration with projections 

based on climate (Figure 3), we assumed for this assessment that increasing fires 

would favor grassland expansion in the next 50 years. Future vegetation trajectories also depend on current vegetation, which, in turn, has been influenced by the 

heavy grazing that occurred in the past. For example, areas with greater quantities 
USDA Forest Service RMRS-GTR-302. 2013. 7

of fine fuel species such as grasses will be more prone to fire and a continued grassland trajectory, while more sparsely vegetated scrublands will be prone to periodic 

shrub die-offs during drought conditions.

Fire regimes in the region have also been altered by introduced grasses, particularly African species—a process that is likely to continue. One of these species, 

Lehmann’s lovegrass (Eragrostis lehmanniana), is already common on portions 

of the Fort (ENRD 2006). Buffelgrass (Pennisetum ciliare), also responsible for 

changing fire regimes, has not yet been documented on Fort Huachuca, but occurs 

within at least a 100-km radius around nearby Tucson (Van Devender and Dimmitt 

2006). Spread of African grasses, along with increased fires, will encourage further 

conversion of native habitats to non-native grasslands.

Figure 3. Current and projected 

climate change as modeled 

for the biotic communities 

of Arizona. Inset shows Fort 

Huachuca. Projections are 

from Rehfeldt and others 

(2006). Projections were used 

to identify future trends for 

biotic communities.
8 USDA Forest Service RMRS-GTR-302. 2013.

Although CAM (crassulacean acid metabolism) plants, such as cactus and agaves, will be resilient to increasing hot and dry conditions (Smith and others 1986), 

they are prone to increased mortality with increasing fires (Thomas 2006), and 

frequent burning can harm agave seedlings and encourage Lehmann’s lovegrass 

(Robinett 1994). Flowering phenology is also strongly related to climate. Less precipitation and increases in extreme temperatures can shorten the length of cactus 

flowering season, which has a direct effect on fruit production and nectar availability (Bustamante and Búrquez 2008).

Riparian habitats in the region are predicted to decline due to decreased average 

stream flows, increased evaporation, and changes to the flood regime (Stromberg 

and others 2006; Serrat-Capdevila and others 2007). Surface water diversions 

from nearby communities also contribute to decline (Stromberg and others 1996). 

In particular, Stromberg and others (2006) predicted a decrease in cottonwood 

and willow, an increase of mesquite, and no change in salt cedar (Tamarix spp.). 

Comparisons of salt cedar-dominated versus cottonwood-willow-dominated habitats on the San Pedro River indicate that surface flow permanence was the most 

important determinant of plant species dominance (Lite and Stromberg 2005); 

thus, with warmer temperatures and continued water table withdrawals (Stromberg 

and others 1996), we may expect greater dominance of salt cedar. Ironically, very 

high water levels have also been associated with declines in willows and cottonwoods on the Colorado River (Laymon and Halterman 1987).

Forest and woodlands types are generally projected to shift upward in elevation 

as temperatures warm (Kelly and Goulden 2008; Lenoir and others 2008). With 

the relatively small and isolated mountain ranges that occur in this region, upward 

shifts will inevitably shrink forest habitats. The highest elevations, here montane 

conifer forest, will be at the greatest risk. The lower elevation Madrean oak and 

pine-oak communities are also at risk for considerable change. Projections shown 

in Figure 3, based on Rehfeldt and others (2006), show the trajectory and future 

stress on biotic communities with limited Madrean woodlands and no coniferous 

forest by 2060. These projections, however, are of future climate correlated with 

the current environment in which biotic communities occur, which cannot capture 

the fundamental niche of all species nor their complex ecological relationships. 

Thus, for this assessment, we viewed these projections as trends (e.g., less forest) 

rather than as the ultimate spatial extent of future communities.

Mexico and Central and South America

A number of species in this assessment, primarily birds, migrate long distances 

and are subject to changing climate in distant regions. 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 (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 to central Mexico and the 

Southwest borderlands (Figure 2; Comrie and Glenn 1998).
USDA Forest Service RMRS-GTR-302. 2013. 9

Increases in temperature are also projected for Central America and, although 

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 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.

Toward the southern part of South America, the climate is projected to become 

more suitable for tropical vegetation, but toward the north, the climate is projected to become drier (Magrin and others 2007). As in North America, wildfires 

are expected to increase in frequency. In northern South America, it is projected that tropical forests will be replaced by savannahs (Magrin and others 2007). 

Mangroves and other coastal habitats are vulnerable to sea level rise throughout 

the region (Magrin and others 2007).

Scoring Results

Vertebrate Species

The vulnerability of 21 vertebrate species to climate change was scored for Fort 

Huachuca, Arizona. Full score details and information related to individual species 

is in Appendix A. Almost all species scored were vulnerable rather than resilient to 

climate change (Table 1). It is likely that this result is partly due to climate change 

exacerbating some of the current impacts already responsible for declines in these 

species. The highest score, or the species most vulnerable to population decline, 

was the northern Mexican gartersnake (Thamnophis eques megalops) followed 

by the southwestern willow flycatcher (Table 1). Species with high vulnerability 

tended to be vulnerable across multiple factors or categories rather than have many 

predictors of vulnerability within a single factor (Table 1). The lowest score was 

for the black-tailed prairie dog, the only species with a negative score, indicating a 

prediction of more favorable conditions and potentially increasing populations in 

the absence of other threats. The aplomado falcon (Falco femoralis septentrionalis) had the second lowest score, but at 1.2, we expect a relatively neutral response 

to climate change conditions in this region. Scores do not directly translate to linear population projections, because we do not know the relative importance of 

each trait considered nor was every possible predictor of population response to 

climate change included. Also note that the highest overall score recorded here, 

10.8, is well below the highest possible score of 20. However, a score of 20 would 

require the species to possess all 22 traits and that each of those traits predicts 

population decline, which is biologically improbable.

Scores are the balance of traits associated with vulnerability minus those associated with resilience; thus, the sign of a score indicates the overall predicted 

direction of change while its magnitude is an indication of how far the balance is 

skewed towards vulnerable (positive) or resilient (negative) traits. Thus, it is not 

just areas of vulnerability but also resilience that affect overall and category scores. 

For example, Mexican spotted owl (Strix occidentalis lucida) has fewer areas of 

vulnerability than the Sonoran tiger salamander (Ambystoma tigrinum stebbinsi), 
10 USDA Forest Service RMRS-GTR-302. 2013.

but because the salamander has more areas of resilience, its overall score is lower 

(Table 2). Similarly, 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 aplomado falcon (Falco femoralis septentrionalis) (Table 2). This has important implications for management and is 

critical to score interpretation because species can be vulnerable for very different 

reasons and, although treated as equal during scoring, the relative influence of each 

of the individual traits on populations is unknown.

Amphibians (average = 6.5) and reptiles (average = 7.0) had the highest vulnerability on average while vulnerability of birds was lower (average = 4.5). This 

trend exists despite recognition in the scoring system of the metabolic resilience 

of ectotherms. Mammals, on average, were the least vulnerable (average = 2.7), 

with the most vulnerable being Arizona shrew (Sorex arizonae) (Table 1). A more 

striking pattern is that related species did not group together in the assessment, and 

taxonomic group members are scattered throughout the rankings. For example, 

the three reptile species assessed, all snakes, ranged from 2.2 to 10.8. Bird species were both near the top and the bottom of the list. More ecologically aligned 

species were similarly vulnerable as exemplified by the two nectivorous bats, the 

lesser long-nosed (Leptonycteris yerbabuenae) and the Mexican long-tongued 

(Choeronycteris mexicana).

Table 1. Climate change vulnerability scores for TER-S at Fort Huachuca, Arizona, listed from most vulnerable (positive scores) 

to most resilient (negative scores). Possible scores range from -20 to 20 for overall and -5 to 5 for each factor. Uncertainty is 

a percentage of scoring questions with limited information or contradictory predictions. Full scoring and scientific names are 

available in Appendix A.

Species Habitat Physiology Phenology Interactions Overall Score Uncertainty (%)

Northern Mexican gartersnake 2.9 2.3 2.5 3.0 10.8 27.0

Southwestern willow flycatcher 2.7 1.7 3.8 2.0 9.9 36.0

Arizona treefrog 3.6 0.7 2.5 1.0 8.0 23.0

Arizona ridge-nosed rattlesnake 2.1 1.5 3.8 1.0 8.0 41.0

Chiricahua leopard frog 2.7 0.7 2.1 2.0 7.8 9.0

Arizona shrew 2.1 2.5 1.3 0.0 6.4 55.0

Western yellow-billed cuckoo 1.3 2.5 3.8 -1.0 6.1 45.0

Buff-breasted flycatcher 1.3 0.8 3.8 0.0 5.3 41.0

Mexican spotted owl 1.3 0.8 2.5 1.0 5.3 27.0

Sonoran tiger salamander 2.1 -0.3 2.1 1.0 5.0 45.0

Western barking frog 2.1 0.5 2.1 0.0 5.0 14.0

Mexican long-tongued bat 1.3 0.7 0.8 1.0 4.1 27.0

Elegant trogon 2.0 -1.2 3.8 0.0 4.1 32.0

Peregrine falcon -0.1 0.8 2.5 1.0 3.5 23.0

Lesser long-nosed bat 0.5 0.7 0.8 1.0 3.1 9.0

Bald eagle 1.3 0.8 -0.4 0.0 2.4 23.0

Northern goshawk 1.3 -1.0 2.5 0.0 2.4 27.0

Cave myotis -1.1 -0.2 3.8 1.0 2.2 32.0

Desert massasauga -1.8 1.5 3.8 0.0 2.2 41.0

Aplomado falcon -2.6 0.8 2.5 2.0 1.2 23.0

Black-tailed prairie dog -2.5 -1.0 2.5 0.0 -2.4 23.0
USDA Forest Service RMRS-GTR-302. 2013. 11

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 Fort Huachuca. Details on SAVS are found in Bagne and others (2011). See Appendix A for more details.

Common name Scientific name

Changes to Breeding Habitat

Changes to Non-breeding Habitat

Changes to Breeding Habitat Components

Changes to Non-breeding Habitat Components

Changes to Habitat Quality

Dispersal Ability

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. Separation Between Activities and Resources

PH4. # of Reproductive Events per Year

Changes in Food Resources

Changes in Predation

Symbiotic Relationships

Changes in Disease

Changes in Competition

Northern Mexican gartersnake Thamnophis eques megalops v v n v v n n v n v v v r n v n v v v n n vSouthwestern willow flycatcher Empidonax trailii extimus v v v n v r v v n n n v n n v v v v n n v nArizona treefrog Hyla wrightorum v v v v n v n v n n n n r n v n v n n n v nArizona ridge-nosed rattlesnake Crotalis willardi willardi v v n n n v n v n n v v r v v n v n n v n nChiricahua leopard frog Lithobates chiricahuensis v v v v r v n n n v v n r v v r v n v n n vArizona shrew Sorex arizonae v v n n n v n v n n n v v n n n v n n n n nWestern yellow-billed cuckoo Coccyzus americanus occidentalis v n v n n r v v n v n v n n v v v r n n n nBuff-breasted flycatcher Empidonax fulvifrons pygmaeus v v n n n r v n n n n v n n v v v n n n n nMexican spotted owl Strix occidentalis lucida v v n n v r n v n n n n n n v n v v n n n nSonoran tiger salamander Ambystoma tigrinum stebbinsi n n v n v v n v n n v r r v v r v n v n n nWestern barking frog Eleutherodactylus augusti cactorum v v n n n v n v n v v r r v v r v n n n n nMexican long-tongued bat Choeronycteris mexicana v v n n n r v r n v n v n n v r v v n n n nElegant trogon Trogon elegans v v v n n r v r n v n r n n v v v n n n n nPeregrine falcon Falco peregrinus anatum n n n n n r v n n n n v n n v n v n n n v nLesser long-nosed bat Leptonycteris yerbabuenae v v n n r r v r n v n v n n v r v v n n n nBald eagle Haliaeetus leucocephalus n v n v n r v n n n n v n n r n n n n n n nNorthern goshawk Accipiter gentilis atricipillus v n n v v r n n n n n r n n v n v n n n n nCave myotis Myotis velifer r r n n v r v v n n n r n n v v v n n n v nDesert massasauga Sistrurus catenatus edwardsi r r n n v r n v n n v v r v v n v n n n n nAplomado falcon Falco femoralis septentrionalis r r v n r r n n n n n v n n v n v v n n v nBlack-tailed prairie dog Cynomys ludovicianus r r n n n r n n n n n r n n v n v n n n n n
12 USDA Forest Service RMRS-GTR-302. 2013.

Examination of the category scores reveals more details on vulnerability 

(Table 1, Figure 4). Note that category scores are adjusted to be on a comparable 

scale because a different number of questions comprise each category. Phenology 

was consistently an important factor in vulnerability for many species (Table 1). 

The phenology factor score reflects the relative influence of climate on species’ 

phenology, timing of resources, and the potential for timing flexibility. 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). 

Habitat scores tended to mirror, with some exceptions, projected habitat change for 

the Southwest with more resilience in grassland species and higher vulnerability in 

riparian and semi-aquatic species. Climate change exacerbates habitat threats that 

are already implicated in species declines such as the loss of habitats vulnerable to 

fire or subject to water withdrawals. Importantly, even where habitat was expected 

to expand, a species could still be found vulnerable because of the diverse criteria 

used in the scoring system. Physiology tended to be an important factor for high 

scoring species. Although the two most vulnerable species had high scores for 

interactions, many species had neutral interaction scores, but uncertainty was also 

high as information on key biological interactions was often limited (Appendix A).

The four Federally endangered species, the southwestern willow flycatcher, the 

lesser long-nosed bat, the aplomado falcon, and the Sonoran tiger salamander were 

vulnerable to further population declines but were not all the highest scored. Those 

species currently considered at increased risk of extinction, but without Federal 

protection may be of particular interest to managers. The two candidate species for 

endangered species listing, yellow-billed cuckoo and Arizona treefrog, were highly vulnerable to further decline associated with climate change, but climate change 

was only listed as a threat warranting candidacy for the treefrog (USFWS 2001, 

Figure 4. Vulnerability 

category and overall 

scores for Federal 

candidate species or 

Federal species of concern 

at Fort Huachuca.
USDA Forest Service RMRS-GTR-302. 2013. 13

2012). Several species designated as at-risk or currently in review by USFWS 

were also identified as vulnerable to declines associated with climate change, including the highest scoring species, northern Mexican gartersnake (Figure 4).

Vascular Plants

Only two plant species were assessed—one endangered and the other a candidate 

for listing. Both received almost identical scores that indicated greater vulnerability with climate change (Table 3). Although population responses may ultimately 

be similar, these species were vulnerable for very different reasons. The Huachuca 

water umbel will be exposed to greater drying of its required wetland and riparian 

habitats, but its ability to disperse via rhizomes and with floods may give it some 

advantage under projected changes. It is also thought that rhizomes are resistant to 

drought, although this will depend on drought duration and/or severity. Assessing 

vulnerability for Lemmon fleabane (Erigeron lemmonii) was limited by lack of 

information. Although conditions in Scheelite Canyon were expected to remain 

suitable into the near future, this species also seems to possess few attributes that 

could be considered resilient. Pollination and reproduction, as for many species, 

is vulnerable as insects will also be subject to changing conditions resulting in 

changes in timing and/or numbers.

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 factors (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 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 that 

were common to multiple species (Table 4). For example, 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 

Table 3. Climate change vulnerability scores for threatened and endangered plant species at Fort Huachuca, 

Arizona, listed from most vulnerable (positive scores) to most resilient (negative scores). Possible scores 

range from -10 to 10 for overall and -3 to 3 for each factor. Uncertainty is a percentage of scoring questions 

with limited information or contradictory predictions. Full scoring and scientific names are available in 

Appendix A.

Species Habitat Physiology Interactions

Overall 

score

Uncertainty 

(%)

Lemmon fleabane -0.3 2 1 2.9 60

Huachuca water umbel 0.5 1 1 2.8 30
14 USDA Forest Service RMRS-GTR-302. 2013. Table 4. Summary of common management target areas for reducing anticipated climate change threats to individual species on Fort Huachuca. This list is not comprehensive but includes target 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 potentially disruptive activities are restricted. Scientific names appear in Appendix A. Species Fire/fuels/ invasive plants Water/riparian Post-fire rehabilitation Corridors/ dispersal Timing restrictions Upland microsites Northern Mexican gartersnake x x x Southwestern willow flycatcher x x Arizona treefrog x x x x Arizona ridge-nosed rattlesnake x Chiricahua leopard frog x x x x Arizona shrew x x x x Western yellow-billed cuckoo x x Buff-breasted flycatcher x x Mexican spotted owl x x x x Sonoran tiger salamander x x x x Western barking frog x x x Mexican long-tongued bat x x Elegant trogon x x x x Peregrine falcon x x Lesser long-nosed bat x x Bald eagle x Northern goshawk x x Cave myotis x x x Desert massasauga x x Aplomado falcon x Black-tailed prairie dog x Huachuca water umbel x x Lemmon’s fleabane x x
USDA Forest Service RMRS-GTR-302. 2013. 15

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.

Fire, Fuels, and Invasive Species Management

As previously noted, conditions conducive to fire ignition and spread are expected to increase. Because individual species respond differently to fire, those 

fires that burn very large areas or encourage habitat conversion, particularly to 

non-native vegetation, are of the most concern from a biodiversity perspective. 

Of particular concern in this region is the interplay among climate, fire, and invasive grasses, which could degrade habitats for some species such as the lesser 

long-nosed bat. Other species may benefit from expanding grasslands, but conversion from native to primarily non-native grasses alters ecosystem processes and 

relationships (D’Antonio and Vitousek 1992; Geiger and McPherson 2005; Van 

Devender and Dimmit 2006). Changes in grassland fire regimes will also affect 

adjacent woodland and forest habitats as fires spread and communities shift upward. Thus, habitats for forest species such as Mexican spotted owl and Arizona 

ridge-nosed rattlesnake (Crotalis willardi willardi) may be affected. Overall, management related to fire has the potential to increase resilience or improve habitat 

for most of the species in this assessment (Table 4).

Fuel management, either through prescribed burning or mechanical treatment, 

can be used to help reduce fire severity and spread (Graham and others 2004). 

Management that focuses primarily on suppression is often counterproductive as 

this approach eventually encourages greater fire severity (Minnich and Chou 1997; 

Stephens and Ruth 2005). Because fires of high severity are also inevitable, plans 

should be in place to reduce potential impacts from fire-fighting efforts (e.g., backfiring and chemical suppressants) and rehabilitate habitats following fire if needed.

Management of non-native plants, particularly invasive grasses, will also be key 

as non-natives play a major role in altering fire regimes and can outcompete native 

grasses and forbs. In addition, measures that prevent introductions and spread will 

be essential and less costly than control measures. 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).

Artificial and Natural Waters

Surface water is already severely limited in the region and native species with 

aquatic life stages have already declined significantly. Natural and artificial waters 

on Fort Huachuca should be evaluated for availability to species under drought 

conditions to plan for limiting conditions. Evaluation should consider substrates, 

capacity and annual longevity, habitat surroundings, special species requirements, 

disease transmission, and potential for supplemental inputs. Artificial waters are 

widely used in wildlife management in the Southwest, although the benefits and 
16 USDA Forest Service RMRS-GTR-302. 2013.

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, not just those that have aquatic life stages. Depending on 

availability of projected surface waters, artificial waters may accordingly need to 

be expanded or modified.

Several TER-S require riparian or aquatic habitats. Management that can maintain water tables and streamflows will be important to these species, but the ability 

to influence current hydrologic processes is limited and likely to become increasingly difficult as temperatures rise and human demand increases. Project proposals 

affecting water withdrawals in the region need to be considered carefully, because 

of the exacerbating stress on TER-S and rare habitats. Managing water with climate change includes identifying incompatibilities between human and ecosystem 

needs (Richter and others 2003).

For some TER-S in this assessment, drying of waters also presents an opportunity. West Nile virus spread by mosquitoes could be reduced improving conditions 

for susceptible species. A number of aquatic breeders, including the Chiricahua 

leopard frog (Lithobates chiricahuensis), Arizona treefrog (Hyla wrightorum), and 

the Sonoran tiger salamander, have been extirpated from permanent water sources 

by invasive predators and competitors such as fish or American bullfrogs (Rana 

catesbeiana), but they are often more tolerant of drying conditions and are currently restricted to temporary waters (Figure 5). As water sources become increasingly 

intermittent, they may become more suitable for some species, and further enhancements, such as invasive species control measures or creating corridors, can 

make the most of this situation and allow the critical shift of species from drying 

habitats to newly suitable ones (Box 2).

Figure 5. Warmer conditions and increasing drought threaten waters occupied by the Chiricahua leopard frog. 

Photo credit: J. Rorabaugh, USFWS.
USDA Forest Service RMRS-GTR-302. 2013. 17

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 Fort Huachuca but increasing elsewhere. Shifting of habitats or populations should also be anticipated 

for geographically based protected areas or designated critical habitat. Managers 

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

that target individual species. Cave myotis (Myotis velifer) roosts in cool and moist 

caves, and as conditions change so will the locations of suitable caves. Although it 

is difficult to project what new species may disperse to and occupy Fort Huachuca 

in the future, they may be species that require inclusion in management planning. 

We identified black-tailed prairie dog as potentially expanding based on climate 

change resilience, depending on impacts from other sources and dispersal barriers. 

Birds can also be anticipated to be some of the first to shift. Monitoring can help 

identify species in the early stages of expansion.

Movements and migrations are partly adaptations to changing conditions; thus, 

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

change. 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 geographic or elevational 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) or 

Box 2. Seizing Opportunity

Although climate change will present challenges to species and their 

management, there will likely be opportunities 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 

arriving, such as for a species that shifts 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 nonnative 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.
18 USDA Forest Service RMRS-GTR-302. 2013.

higher elevations within the current range eliminate many of these issues but may 

be of questionable benefit in the long term. Conversely, translocations may be 

beneficial for climate change management as new locations may include more 

favorable microsites, help reduce risk of stochastic events, or offer better natural 

dispersal opportunities. Both plants in this assessment could likely be established 

at new locations, although questions remain as to the desirability of these actions. 

Falk and others (1996) provided guidelines for rare plant reintroductions.

Coping With Physiological Thresholds

In the absence of dispersal, physiological limitations can result in additional 

environmental stress manifested as poor survival or reproduction (Bernardo and 

Spotila 2006). TER-S are at a particular disadvantage for physiological stress, as 

small population sizes will limit adaptation through natural selection. 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 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 should be 

given to microsites with suitable habitat that are cool and moist, such as northfacing 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. Protection of areas with greater litter accumulation or water-retaining soil types could help species such as the Arizona treefrog. 

Fort Huachuca and surrounding areas have varied topography conducive to diverse 

microclimates, thus there is good potential to use this strategy. In addition, because 

drought is a limiting factor for many of these species, it may be best to add drought 

effects to planning documents and anticipate possible interventions.

Anticipating Shifts in Timing

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

conditions. It also was the most sensitive factor to changes 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 need to track these changes. Although timing of individual 

activities is not readily managed, in some cases, management can affect the timing 

of resources. An example with potential for intervention and critical to a number of 

species in this assessment is the presence and duration of temporary pools.

Prioritization

The apparent vulnerability of TER-S to climate change highlights the challenges that will face managers. Managers already need to make choices about where to 

focus resources, but as stresses on species magnify, there will likely be an increasing need to prioritize species, actions, or both. 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 also require management if they 

negatively impact TER-S. Ranks in this assessment are based on the number of 
USDA Forest Service RMRS-GTR-302. 2013. 19

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. Predictions of climate and 

vulnerability are uncertain, but an assessment, even if limited, can provide input 

when no other information is available and can serve as a starting point to address 

species management under climate change.

Landscape-Scale Management and Partners

Perhaps one of the greatest challenges for managing species under a 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 change issues, as well as being cost effective. Cooperative approaches can help to balance 

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. Fort Huachuca is already part of the Huachuca FireScape, a 

regional effort to address fuels reduction and a good example of a landscape-scale 

management plan that can begin to address adaptation to climate change (USFS 

2009). Similar landscape efforts are needed to address climate change threats to 

species and related factors, including wildlife corridors, invasive species, water 

availability, and microsite diversity.

Uncertainty

Although drawn from basic life history and ecology, in many instances, scoring 

was sometimes uncertain because of lack of information. Deficiencies were common in a few key areas for vertebrates but were more extensive for plant species 

and limited the scoring criteria used. Physiological thresholds for vertebrates in 

natural environments are known for few species and thus limited our ability to 

score this important trait. More uncertainty is added when scoring depends on a 

secondary prediction for another species (e.g., predators, pollinators, and disease 

vectors). Although predictions may be limited by information gaps, 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). Resource managers can accomadate uncertainty to a large 

extent by employing monitoring programs to identify critical impacts early and 

taking an adaptive management approach that can adjust to complex response. 

Predicting the future is inherently uncertain, but the exercise of prediction will 

improve as better models are developed and more research is done.

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 
20 USDA Forest Service RMRS-GTR-302. 2013.

suitable for modeling 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 vulnerability 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 that 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 opportunity (Box 2). Although the process and the product are inherently 

imprecise, this effort is an important first step toward anticipating and responding to climate change and provides a framework for integrating new research and 

information.

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USDA Forest Service RMRS-GTR-302. 2013. 25

Appendix A: Species Accounts
26 USDA Forest Service RMRS-GTR-302. 2013.

Sonoran Tiger Salamander 

(Ambystoma tigrinum stebbinsi)

SUMMARY

Declines in amphibians are associated with interactions of multiple threats and the threat due to climate 

change is likely to contribute to further declines. Life history strategies, such as having both terrestrial 

and aquatic life forms, may give this species some resilience to fluctuating rainfall patterns and drought. 

Unfortunately, this species range is already very restricted locally and is vulnerable to extirpation as habitat 

suitability fluctuates. Vulnerability to climate change could conversely be an opportunity for management to 

aid in the removal of non-native barred salamanders.

Introduction

The Sonoran subspecies of tiger salamander is currently listed by the U.S. Fish and Wildlife Service (USFWS) 

as endangered. No critical habitat has been designated as of the time of this report. It is a species of greatest 

conservation need, Tier 1B, in Arizona State Wildlife Action Plan or SWAP (AGFD 2006). Currently, Sonoran tiger 

salamanders are found mostly in human-made ponds or cattle tanks and occur in ponds in the San Rafael Valley, 

Arizona. Following European settlement, erosion and alterations to the hydrology within the species’ range are 

thought to have destroyed most of the temporary pond habitats. Permanent water, although suitable, often has 

introduced fish and bullfrogs, which prey on salamanders. Most salamanders on Fort Huachuca are thought to 

be barred tiger salamanders except for one pond near the San Rafael Valley in the Upper Garden Canyon (USFWS 

2002).

Fort Huachuca Climate and Projections

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

and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

VULNERABILITY Score Uncertainty

Habitat 2.1 43%

Physiology -0.3 33%

Phenology 2.1 50%

Interactions 1.0 60%

Overall 5.0 45%

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

-5 0 5 
USDA Forest Service RMRS-GTR-302. 2013. 27

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

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

Tiger salamanders are threatened by loss of habitat, introduced predators, and hybridization with barred tiger 

salamanders (USFWS 2002). Threats such as ultra-violet (UV) radiation, water pH, pesticides, and disease may 

interact and increase susceptibility to declines. A number of these threats will likely be exacerbated in the future 

by climate change. Although most threats identified are associated with aquatic habitats, terrestrial habitats may 

also be vulnerable to drier conditions, which will limit their suitability.

This species is restricted to only a few locations, and introduced predators and barred tiger salamanders, with 

which it can hybridize, limit dispersal to new locations. Dispersal among aquatic habitats, however, will become 

increasingly important as these habitats vary in susceptibility to drying. Drought can further disrupt dispersal by 

removing potential corridors and altering habitat suitability. Monsoons likely play a role in providing dispersal 

opportunities, but are not well projected for the future. It is likely that monsoon rainfall will become more 

variable so dispersal opportunity is expected to likewise fluctuate widely from year to year.

Research Needs

Periodic die-offs associated with Ambystoma Tigrinum Virus (ATV) have no known relationship to climate or 

habitat, but this virus has only been recently identified and little field study has been conducted. Habitat features 

associated with favorable terrestrial habitats have received little attention. An assessment related to future 

condition of wetlands and dispersal corridors will be important to identifying suitable habitat of the future and 

planning management. 

Management Implications

Management related to maintaining water tables and pond duration is important. The only known salamander 

population on Fort Huachuca occurs in an artificial pond. This pond has shrunk and even dried in past years, but 

the population has survived these episodes (ENRD 2006). Longer dry periods, however, will likely be detrimental, 

though critical limits are not known for the species. Although options for this particular pond are unknown, 

some ponds may be suitable for artificial water inputs should they dry for too long a period. Additionally, 

factors related to tank construction and pond substrates can likely be used to increase water retention of 

ponds. Attention should also be given to protection of terrestrial habitats adjacent to temporary ponds used by 

terrestrial salamanders. Litter and debris as well as low levels of disturbance are likely important factors that can 

be managed to maintain favorable microclimate of these habitats.

Currently occupied habitats are those that dry periodically to discourage non-native predators and competitors 

while still staying moist long enough to allow development of larval salamanders. These areas will be subject to 

further drying that can eventually make them unsuitable. Some areas that currently sustain permanent waters 

may actually increase in suitability as drying occurs and aquatic non-natives are extirpated. Dispersal will then be 

critical to survival in the future. Removal of barred tiger salamanders and introduced fish from suitable dispersal 

habitats could also be implemented to increase available habitats and resiliency of populations to declines. 

Aspects of vulnerability outlined for the Sonoran subspecies could aid in extirpation of barred tiger salamanders 

or hybrids where they occur and can be encouraged where appropriate. Translocation could be a viable option 

for future management of this species and should be planned based on predicted future wetland conditions 

along with potential for increased predation. The status of this species as a carrier of chytrid fungus should be 

considered in relation to proximity of susceptible TER frogs and during any assisted migration programs.
28 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Sonoran	
  Tiger	
  Salamander (Ambystoma	
  tigrinum	
  stebbinsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Area	
  and	
  

distribution:

breeding

Is	
  the	
  area	
  or	
  location	
  

of	
  the	
  associated	
  

vegetation	
  type	
  used	
  

for	
  breeding	
  activities	
  

by	
  this	
  species	
  

expected	
  to	
  change?

Terrestrial	
  adults	
  live	
  in	
  oak	
  woodlands	
  and	
  grasslands	
  

(USFWS	
  2002).	
  Grasslands	
  may	
  expand,	
  but	
  woodlands	
  

will	
  be	
  vulnerable	
  to	
  increasing	
  fires	
  and	
  upslope	
  shifts.	
  

Overall,	
  no	
  change	
  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?

Same	
  as	
  above.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Eggs	
  are	
  laid	
  in	
  water	
  of	
  permanent	
  or	
  temporary	
  sources	
  

and	
  attached	
  to	
  vegetation,	
  debris,	
  or	
  rocks	
  (USFWS	
  

2002).	
  Water	
  availability	
  is	
  expected	
  to	
  be	
  reduced. 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?	
  

Terrestrial	
  adults	
  use	
  mammal	
  burrows	
  or	
  bury	
  

themselves	
  in	
  soft	
  soils	
  to	
  escape	
  desiccation.	
  Soils	
  

suitable	
  for	
  burrows	
  are	
  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?	
  

Better	
  survival	
  is	
  associated	
  with	
  more	
  emergent	
  

vegetation,	
  some	
  shallow	
  water,	
  and	
  soft	
  substrates	
  

(Sarell	
  2004).	
  Emergent	
  vegetation	
  may	
  be	
  reduced	
  with	
  

warmer	
  temperatures	
  and	
  greater	
  evaporation,	
  although	
  

this	
  will	
  depend	
  on	
  hydrology	
  of	
  specific	
  sites.

1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Little	
  information	
  on	
  site	
  fidelity,	
  but	
  other	
  congeneric	
  

salamanders	
  generally	
  return	
  to	
  the	
  ponds	
  where	
  they	
  

were	
  born.	
  Dispersal	
  has	
  been	
  observed	
  up	
  to	
  3-­‐4	
  km	
  

from	
  source	
  populations	
  (USFWS	
  2002).	
  Others	
  note	
  that	
  

tiger	
  salamanders	
  have	
  a	
  minimal	
  capacity	
  for	
  dispersal	
  

and	
  they	
  usually	
  migrate	
  162 m	
  to	
  229 m	
  from	
  breeding	
  

pond	
  to	
  aestivation	
  sites	
  over	
  3	
  days	
  (AmphibiaWeb	
  

2008).Dispersal	
  is	
  also	
  thought	
  to	
  be	
  limited	
  by	
  

distribution	
  of	
  temporary	
  ponds.	
  Overall,	
  limited	
  ability	
  

to	
  disperse	
  as	
  habitats	
  change.

1

7.	
  Migratory	
  or	
  

transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Moves	
  between	
  terrestrial	
  and	
  aquatic	
  environments,	
  but	
  

no	
  specific	
  transitory	
  habitats	
  required.

0
USDA Forest Service RMRS-GTR-302. 2013. 29

Physiology:	
  Sonoran	
  Tiger	
  Salamander (Ambystoma	
  tigrinum	
  stebbinsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Eggs	
  are	
  prone	
  to	
  freezing	
  and	
  dehydration	
  (USFWS	
  

2000).	
  Adults	
  are	
  tolerant	
  temperature	
  from	
  5 °C	
  to	
  30 °C	
  

in	
  ponds	
  and	
  in	
  terrestrial	
  environments	
  can	
  survive	
  

below	
  freezing	
  to	
  above	
  35 °C	
  (USFWS	
  2002).	
  Terrestrial	
  

amphibians	
  are	
  prone	
  to	
  desiccation,	
  which	
  will	
  increase	
  

with	
  warmer	
  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?

Although	
  floods	
  may	
  occur	
  more	
  frequently	
  along	
  stream	
  

courses,	
  currently	
  occupied	
  ponds	
  are	
  not	
  vulnerable	
  to	
  

flooding.	
  No	
  effects	
  of	
  fires	
  are	
  known. 0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Terrestrial	
  movements	
  are	
  limited	
  by	
  moisture	
  and	
  may	
  

be	
  decreased	
  by	
  warmer	
  temperatures	
  and	
  greater	
  

evaporation.	
  Aquatic	
  movements	
  probably	
  will	
  not	
  be	
  

limited. 1

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Mostly	
  adults	
  are	
  terrestrial	
  while	
  larvae	
  are	
  aquatic.	
  

Mature	
  individuals	
  can	
  remain	
  aquatic	
  (branchiate	
  adults	
  

or	
  neotenes)	
  with	
  gills	
  or	
  metamorphose	
  into	
  gill-­‐less	
  

terrestrial	
  adults.	
  Branchiate	
  adults	
  occur	
  in	
  permanent	
  

water	
  sources	
  and	
  although	
  pond	
  drying	
  can	
  induce	
  

metamorphosis,	
  many	
  branchiate	
  adults	
  die	
  during	
  the	
  

process	
  (USFWS	
  2002).	
  In	
  permanent	
  water,	
  only	
  17%	
  

metamorphose	
  into	
  terrestrial	
  adults,	
  while	
  all	
  that	
  are	
  

large	
  enough	
  will	
  in	
  drying	
  ponds	
  (Collins	
  and	
  others

1988).	
  200	
  to	
  2000	
  eggs	
  are	
  laid	
  (USFWS	
  2000)	
  and	
  can	
  

have	
  large	
  reproductive	
  output	
  in	
  favorable	
  years.

-­1

6.	
  Metabolic	
  

rates

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic. -­1

Phenology:	
  Sonoran	
  Tiger	
  Salamander (Ambystoma	
  tigrinum	
  stebbinsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Cues Does	
  this	
  species	
  use	
  

temperature	
  or	
  

moisture	
  cues	
  to	
  

initiate	
  activities	
  

related	
  to	
  fecundity	
  or	
  

survival	
  (e.g.,	
  

hibernation,	
  migration,	
  

breeding)?	
  

Temperature	
  is	
  a	
  cue	
  for	
  adult	
  emergence	
  and	
  migration	
  

(AmphibiaWeb	
  2008).	
  

1
30 USDA Forest Service RMRS-GTR-302. 2013.

Phenology:	
  Sonoran	
  Tiger	
  Salamander (Ambystoma	
  tigrinum	
  stebbinsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

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?	
  

Requires	
  standing	
  water	
  from	
  January	
  through	
  June	
  for	
  

aquatic	
  young	
  to	
  develop	
  (USFWS	
  2002).	
  Rarely	
  breeds	
  

after	
  monsoon	
  rains	
  (USFWS	
  2002).	
  Standing	
  water	
  likely	
  

related	
  to	
  timing	
  of	
  winter	
  rainfall,	
  which	
  is	
  likely	
  to	
  

change.

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?

Eggs	
  take	
  longer	
  to	
  develop	
  in	
  colder	
  water	
  (USFWS	
  

2002),	
  thus	
  development	
  may	
  keep	
  up	
  with	
  changing	
  

pond	
  duration	
  to	
  some	
  extent.	
  Favorable	
  migration	
  

conditions	
  directly	
  trigger	
  migration. -­1

4.	
  Resilience	
  

to	
  timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Most	
  report	
  one	
  reproductive	
  event	
  per	
  year	
  (Sarell	
  

2004),	
  though	
  some	
  cite	
  two	
  if	
  habitat	
  is	
  available.

However,	
  Church	
  and	
  others	
  (2007)	
  suggested	
  the	
  latter	
  

is	
  prohibitively	
  costly	
  for	
  females.

1

Biotic	
  Interactions:	
  Sonoran	
  Tiger	
  Salamander (Ambystoma	
  tigrinum	
  

stebbinsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Adults	
  eat	
  a	
  variety	
  of	
  invertebrates.	
  Branchiate	
  adults	
  

eat	
  zooplankton	
  and	
  macroinvertebrates.	
  No	
  expected	
  

changes	
  in	
  overall	
  levels	
  of	
  diverse	
  prey	
  species.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Predation	
  is	
  considered	
  a	
  major	
  threat	
  to	
  this	
  species.	
  

Predators	
  included	
  caddis	
  flies,	
  dragonfly	
  naiads,	
  

predaceous	
  diving	
  beetles,	
  giant	
  water	
  bugs,	
  newts,	
  

conspecifics	
  (cannibalistic	
  morphs),	
  snakes,	
  predatory,	
  

wading	
  and	
  shore	
  birds,	
  badgers,	
  raccoons,	
  coyotes,	
  

opossums,	
  and	
  humans	
  (AmphibiaWeb	
  2008). Predators,	
  

particularly	
  American	
  bullfrog	
  and	
  introduced	
  fish,	
  pose	
  

significant	
  threat	
  and	
  considerable	
  impact	
  on	
  

salamanders	
  (USFWS	
  2002).	
  Currently	
  mostly	
  occupies	
  

habitats	
  without	
  fish	
  and	
  few	
  bullfrogs	
  (USFWS	
  2002),	
  

but	
  impacts	
  from	
  American	
  bullfrogs	
  may	
  increase	
  as	
  

they	
  are	
  expected	
  to	
  be	
  resilient	
  to	
  climate	
  change.

1

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	
  

Frequent	
  disease	
  outbreaks	
  attributed	
  to	
  a	
  ranavirus,	
  

ATV	
  (Jancovitch	
  and	
  others	
  1997).	
  Frogs	
  and	
  fish	
  could	
  

not	
  be	
  artificially	
  infected	
  and	
  are	
  not	
  likely	
  carriers	
  for	
  

this	
  disease	
  (Jancovitch	
  and	
  others	
  2001).	
  No	
  research	
  

was	
  found	
  to	
  indicate	
  that	
  these	
  ranaviruses	
  would	
  

increase	
  with	
  warmer	
  temperatures.	
  Note	
  that	
  this	
  

0
USDA Forest Service RMRS-GTR-302. 2013. 31

Biotic	
  Interactions:	
  Sonoran	
  Tiger	
  Salamander (Ambystoma	
  tigrinum	
  

stebbinsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

to	
  change?	
   species,	
  although	
  unaffected,	
  is	
  a	
  carrier	
  for	
  chytrid	
  

fungus.

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Fish	
  are	
  not	
  only	
  predators,	
  but	
  also	
  a	
  primary	
  

competitor	
  (Sarell	
  2004).	
  Fish	
  do	
  not	
  occur	
  in	
  current	
  

habitats.	
  Barred	
  salamanders	
  may	
  also	
  compete,	
  but	
  are	
  

expected	
  to	
  have	
  similar	
  response	
  to	
  climate	
  change.

0
32 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

AmphibiaWeb: Information on amphibian biology and conservation. [web application]. 2008. Berkeley, 

California: Ambystoma tigrinum. AmphibiaWeb, available at http://amphibiaweb.org/.

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Church, D. R. Bailey, L. L., Wilbur, H. M., Kendall, W. L., and J. E. Hines. 2007. Iteroparity in the variable 

enviorment of the salamander Amystoma tigrinum. Ecology 88:891-903.

Collins, J. P., T. R. Jones, and H. J. Berna. 1988. Conserving genetically distinctive populations: The case of the 

Huachuca tiger salamander (Ambystoma tigrinum stebbinsi Lowe). Pages 45-53 in R.C. Szaro, K.C. Severson, 

and D.R. Patton, editors. Management of amphibians, reptiles, and small mammals in North America. USDA 

Forest Service GTR-RM-166, Fort Collins, Colorado.

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. 

Jancovich, J. K., E. W. Davidson, J. F. Morado, B. L. Jacobs, and J. P. Collins. 1997. Isolation of a lethal virus from 

the endangered tiger salamander Ambystoma tigrinum stebbinsi. Diseases of Aquatic Organisms 31:161-

167.

Jancovich J. K., E. W. Davids, A. Seiler, B.L. Jacobs, and J. P. Collins. 2001. Transmission of the Ambystoma 

tigrinum virus to alternative hosts. Diseases of Aquatic Organisms 46:156-164.

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.

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.

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.

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.

Sarell, M. J. 2004. Tiger Salamander Ambystoma tigrinum. In Accounts and Measures for Managing Identified 

Wildlife–Accounts V. British Columbia Ministry of Water, Land and Air Protection, Victoria, BC.

Seager, R., M. Ting, 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.

Stromberg, Juliet, S. J. Lite, T. J. Rychener, L. R. Levick, M. D. Dixon, and J. M. 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.

USFWS (United States Fish and Wildlife Service). 2002. Sonora tiger salamander (Ambystoma tigrinum 

stebbinsi) recovery plan. U.S. Fish and Wildlife Service, Phoenix, Arizona. 

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

role of ecophysiology. 
USDA Forest Service RMRS-GTR-302. 2013. 33

Western Barking Frog 

(Eleutherodactylus augusti cactorum)

SUMMARY

The barking frog is unusual compared to other frogs in Arizona. It is a terrestrial species with direct development of the young from eggs, which also receive parental care. These features, along with its lack of reliance 

on aquatic habitats, may incur resilience to climate change in comparison with some frog species. Conversely, 

dependence on rainfall and moist habitats along with low dispersal ability will likely increase this species’ 

vulnerability to declines with climate change. Balancing these traits overall, this species was assessed to be 

vulnerable to population declines associated with projected climate change.

Introduction

Populations of western barking frog were discovered on Fort Huachuca in 2002. It is a species of greatest 

conservation need, Tier 1B, in Arizona State Wildlife Action Plan or SWAP (AGFD 2006) and designated as a 

species at risk (SWESA 2006). Range in the United States is Arizona, New Mexico, and Texas along the Mexico 

border (AmphibiaWeb 2010). It is the only representative of this mostly tropical family in Arizona. There is 

currently unresolved taxonomy for subspecies (AmphibiaWeb 2010) and individuals in Arizona differ from 

those found in New Mexico and Texas (Goldberg 2003).

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

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

section of the main document.

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 2.1 14%

Physiology 0.5 17%

Phenology 2.1 0%

Interactions 0.0 20%

Overall 5.0 14%

-5 0 5 
34 USDA Forest Service RMRS-GTR-302. 2013.

Other Threats and Interactions With Climate

Habitat loss may be the greatest current threat to this species. Open pit copper mining has been implicated in 

the loss of Arizona habitat (Goldberg 2003), but mining does not occur on or adjacent to Fort Huachuca. Other 

habitat loss, such as through disturbance, will likely increase with climate change as fires increase and rainfall 

becomes more variable. Although vegetation associated with this species will be vulnerable to changes, 

species’ presence may be more closely linked to geologic features such as rock outcrops. This species’ 

association with oak woodlands and mixed pine-oak forests may be more related to moisture than vegetation 

type. Changes in the amount of rainfall, especially the summer rains that are tied to breeding in this species, 

are difficult to project, but drier conditions on average are likely with increased evaporation from higher 

temperatures and changes in rainfall timing.

Research Needs

Little is known about this species and monitoring populations is difficult because of their cryptic behavior 

(Goldberg and Schwalbe 2004). Full species’ range in Arizona is unknown, because this species may be 

undetected in additional locations (Goldberg 2003).

Management Implications

This species may be difficult to manage if climate change brings drier conditions. Its association with particular 

geologic features and low dispersal ability make it unlikely to move upslope or to new locations. It may, 

however, currently occur in more locations than are known making any monitoring of population trends 

difficult. This species’ association with moist habitats rather than permanent waters and its ability to remain 

inactive for extended periods will help it cope with dry years better than many of the semi-aquatic amphibian 

species. Extent of vulnerability in this species will depend on monsoonal rain patterns and drought intensity. 

Because these climate events are not well projected, management may be best focused on documenting 

habitat and presence of the species. Planning that includes contingency plans for assisting species during 

extreme conditions should consider actions to assist this species. Although a controversial method, this 

species may be a good candidate for localized translocations with transfer from drier locales to more mesic 

locales. 
USDA Forest Service RMRS-GTR-302. 2013. 35

Habitat:	
  Western	
  Barking	
  Frog	
  (Eleutherodactylus	
  augusti	
  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,	
  occupies	
  elevations	
  from	
  1280	
  to	
  1890 m	
  

(Degenhardt	
  and	
  others	
  1996). In	
  Arizona,	
  barking	
  frogs	
  

have	
  been	
  found	
  in	
  rock	
  outcrops	
  within	
  Madrean	
  

evergreen	
  woodlands	
  (Goldberg	
  and	
  Schwalbe	
  2004)	
  and	
  

pine-­‐oak	
  woodlands	
  (Brennan	
  and	
  Holycross	
  2006).

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	
  getation	
  

type?

Eggs	
  are	
  laid	
  in	
  moist	
  and	
  protected	
  locations	
  such	
  as	
  

rain-­‐filled	
  cracks,	
  fissures,	
  and	
  moist	
  caves	
  or	
  under	
  

rocks	
  (AmphibaWeb	
  2010).	
  Rock	
  outcrops	
  and	
  fissures	
  

unlikely	
  to	
  change	
  (see	
  Physiology	
  Question	
  3	
  and	
  

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?

Winter	
  or	
  dry	
  season	
  refugia	
  are	
  required.	
  Generally	
  

associated	
  with	
  cliffs	
  and	
  caves.	
  Rock	
  outcrops	
  and	
  caves	
  

are	
  unlikely	
  to	
  change.

0

5.	
  Habitat	
  

quality

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?

Not	
  known.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Very	
  limited	
  movements.

1

7.	
  	
  Migratory	
  or	
  

transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Move	
  between	
  overwintering	
  and	
  summer	
  activity	
  sites	
  

up	
  to	
  50 m	
  (AmphibiaWeb	
  2010).	
  No	
  transitional	
  habitats	
  

required.

0
36 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Western	
  Barking	
  Frog	
  (Eleutherodactylus	
  augusti	
  cactorum)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Although	
  terrestrial,	
  like	
  many	
  amphibians,	
  this	
  species	
  is	
  

prone	
  to	
  dessication. 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	
  disturbance	
  interactions.	
  Moist,	
  rocky	
  habitats	
  

are	
  not	
  fire	
  prone.	
  It	
  is	
  speculated	
  that	
  females	
  may	
  stay	
  

with	
  the	
  eggs	
  and	
  excrete	
  urine	
  to	
  maintain	
  moisture	
  

(Brennan	
  and	
  Holycross	
  2006,	
  AmphibiaWeb	
  2010),	
  thus	
  

this	
  may	
  help	
  eggs	
  to	
  survive	
  more	
  variable	
  rainfall	
  and	
  

drying	
  conditions.	
  Extended	
  droughts	
  likely	
  limit	
  

reproduction	
  and	
  survival.

1

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Activity	
  is	
  limited	
  by	
  moisture.	
  Drier	
  conditions	
  are	
  likely	
  

with	
  warmer	
  temperatures.

1

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

May	
  go	
  several	
  years	
  without	
  breeding	
  and	
  then	
  has	
  

clutches	
  containing	
  from	
  50–76	
  eggs	
  (AmphibiaWeb	
  

2010).	
  Tadpoles	
  develop	
  inside	
  the	
  egg	
  and	
  emerge	
  fully	
  

developed. In	
  addition,	
  females	
  may	
  tend	
  the	
  eggs	
  and	
  

keep	
  them	
  moist	
  (Brennan	
  and	
  Holycross	
  2006).	
  These	
  

strategies	
  may	
  help	
  this	
  species	
  survive	
  during	
  dry	
  years.

-­1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic	
  and	
  may	
  be	
  able	
  to	
  use	
  torpor	
  facultatively	
  

(AmphibiaWeb	
  2010). -­1

Phenology:	
  Western	
  Barking	
  Frog	
  (Eleutherodactylus	
  augusti	
  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)?

Males	
  generally	
  call	
  during	
  rainfall	
  and	
  in	
  Arizona	
  

typically	
  with	
  summer	
  rains	
  beginning	
  in	
  June	
  or	
  July	
  

(AmphibiaWeb	
  2010).

1

2.	
  Event	
  timing Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?

Breeding	
  coincides	
  with	
  rainfall	
  likely	
  because	
  of	
  moist	
  

conditions	
  needed	
  for	
  successful	
  egg	
  laying	
  and	
  

development	
  (AmphibiaWeb	
  2010).	
  Foraging	
  may	
  also	
  be	
  

limited	
  by	
  moisture.	
  Timing	
  of	
  rainfall	
  is	
  likely	
  to	
  change. 1
USDA Forest Service RMRS-GTR-302. 2013. 37

Phenology:	
  Western	
  Barking	
  Frog	
  (Eleutherodactylus	
  augusti	
  cactorum)

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?

Breeding	
  appears	
  to	
  be	
  triggered	
  directly	
  by	
  rainfall,	
  

which	
  provides	
  required	
  moisture	
  for	
  egg	
  development,	
  

thus	
  there	
  is	
  a	
  close	
  match	
  between	
  cues	
  and	
  resources.

-­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:	
  Western	
  Barking	
  Frog	
  (Eleutherodactylus	
  augusti	
  

cactorum)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Eats	
  a	
  variety	
  of	
  invertebrates	
  including	
  grasshoppers,	
  

centipedes,	
  and	
  crickets	
  (AmphibiaWeb	
  2010).	
  Wide	
  

variety	
  of	
  prey,	
  likely	
  have	
  differing	
  responses	
  to	
  climate	
  

change.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Unknown	
  predators	
  (AmphibiaWeb	
  2010).

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.	
  Terrestrial	
  habits	
  likely	
  reduce	
  risk	
  of	
  

chytridiomycosis.

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

No	
  known	
  competitors.	
  Very	
  different	
  associations	
  than	
  

other	
  local	
  frogs. 0
38 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

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

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

AmphibiaWeb: Information on amphibian biology and conservation. [web application]. 2010. Berkeley, 

California: AmphibiaWeb. Available: http://amphibiaweb.org/. (Accessed: Jul 4, 2010).

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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool.

Brennan, T. C., and A. T. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game 

and Fish Department. Phoenix, AZ.

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 pp.

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.

Goldberg, C. S. 2003. Barking frog (Eleutherodactylus augusti). Sonoran Herpetologist 17:54-56.

Goldberg, C. S. and C. R. Schwalbe. 2004. Considerations for monitoring a rare anuran (Eleutherodactylus 

augusti). The Southwestern Naturalist 49:442-448.

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.

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.

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.

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.

Seager, R., M. Ting, 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.

(SWESA) Southwest Strategy Endangered Species Act Team. 2006. Species at Risk Report for New Mexico and 

Arizona. DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

Stromberg, Juliet, S. J. Lite, T. J. Rychener, L. R. Levick, M. D. Dixon, and J. M. 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.

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-302. 2013. 39

Chiricahua Leopard Frog 

(Lithobates or Rana chiricahuensis)

SUMMARY

Chiricahua leopard frogs only remain extant in small, scattered ponds and stock tanks because larger and 

more permanent water sources generally contain more native and non-native predators and competitors. Unfortunately, the currently occupied habitats will be at greater risk to drying as temperatures warm. Conversely, 

increased temperatures may offer a number of advantages as drying of water sources for short periods can 

help reduce non-native predators, higher temperatures reduce susceptibility to chytridiomycosis, and warmer 

waters increase growth rates. Many questions surround prediction of climate change effects in this species 

because of the complex interaction of threats and climate. Management will be critical, because location of 

suitable habitats is expected to shift.

Introduction

Genus was changed from Rana to Lithobates (Frost and others 2006), but Rana is still in common use. 

Chiricahua leopard frog was listed as threatened by USFWS in 2002. Populations previously identified as 

Ramsey Canyon leopard frog (Rana subaquavocolis) are now considered a population of the Chiricahua 

leopard frog (Goldberg and others 2004, Hillis and Wilcox 2005). Ramsey Canyon leopard frog is designated 

as a species at risk (SWESA 2006). There are two disjunct metapopulations: montane populations along the 

Mogollon rim and western New Mexico and southern populations in the border region of Arizona, New 

Mexico, and Mexico (USWFS 2007). They have disappeared from many of their historic locations and appear 

be present at less than 20% of those sites (USFWS 2007).

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 2.7 0%

Physiology 0.7 0%

Phenology 2.1 25%

Interactions 2.0 20%

Overall 7.8 9%

-5 0 5 
40 USDA Forest Service RMRS-GTR-302. 2013.

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

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

We focus on those impacts expected to interact with climate change and refer the reader to Southwest 

Endangered Species Act Team (2008) report on this species for a thorough overview of impacts and 

management recommendations regarding the Chiricahua leopard frog. Also note that the climate change 

vulnerability score was based on currently occupied habitats and several additional traits would have 

been considered vulnerable if we had included formerly occupied habitats during scoring. This species is 

threatened by invasive species, water regulation, mining, fire in upland habitats, pesticides, UV radiation, 

and chytridiomycosis (USFWS 2007). In addition, life history predisposes this species to ongoing extirpation 

and recolonization of populations, thus any disruption of metapopulation dynamics can result in the loss 

of the species from entire regions (USFWS 2007). Although not currently overlapping with the range of the 

Chiricahua leopard frog, the Rio Grande leopard frog (Rana berlandieri) has been introduced in other parts 

of Arizona (Platz and others 1990). Expansion of the larger Rio Grande leopard frog could negatively impact 

populations. Many of these threats are expected to interact with climate.

Individual localities are subject to extirpation and recolonization with metapopulation dynamics is important 

to long-term persistence. In addition, Maintenance of corridors for dispersal of juveniles and adults is thought 

to be critical to preserving populations (Jennings and Scott 1991, USFWS 2007). Drought can disrupt dispersal 

by removing potential corridors and altering habitat suitability. Changes in habitat suitability are complicated 

by the association of Chiricahua leopard frog presence with complexes of permenant and ephemeral waters. 

Temporary pools that do not support non-native predators may provide the best conditions for dispersal. 

Monsoons likely play a role in providing dispersal opportunities, but are not well projected for the future. 

It is likely that monsoon rainfall will become more variable so dispersal opportunity is expected to likewise 

fluctuate widely from year to year.

Fires, particularly those of high severity, can negatively impact leopard frog populations, particularly through 

indirect effects from burned upland habitats. Leopard frog habitat is lost or degraded following fire through 

sedimentation and high run-off events such as those which occurred in Miller Canyon following the 1977 

wildfire and the 2011 Monument Fire where sediment increased by almost 1000% (SWESA 2008, USFS 2011). 

Increased fire occurrence and severity in upland habitats and increased storm intensity are more likely to 

occur with future climate, resulting in an increased risk to Chiricahua leopard frog habitats. Depending on 

fire season and severity, fire can also have positive impacts through increases in water availability (Neary and 

others 2005), but these increases are generally temporary. Chemicals used in fire suppression are toxic to 

tadpoles and may concentrate in ponds and pools such as those favored by the Chiricahua leopard frog (Calfee 

and Little 2003).

Research Needs

There are conflicting predictions for the interaction of chytrid fungus and climate change that need to be 

resolved. Better information is needed on the interactions of chytrid fungus and temperature in effects on 

disease prevalence and population dynamics as well as other important variables such as bullfrogs and water 

permanence. Local landscape predictions of future wetland distributions will be important to evaluating 

dispersal and effective management options. The role of permanent versus ephemeral waters in long-term 

persistence of leopard frogs needs to be explored.
USDA Forest Service RMRS-GTR-302. 2013. 41

Management Implications

Substrate of water sources, such as those that can maintain wet mud layers, may be important in survival 

during periods when surface waters dry. Concrete substrates may maintain surface water longer, but would 

not provide refuge for burrowing during dry periods. These sites that are prone to drying are also where the 

species remains extant due to absence of aquatic predators (USFWS 2007); thus, management attention 

to water depth and duration as well as substrate may be critical with increasing droughts and evaporation. 

Monitoring of water sources will be critical during droughts or following wildfires and some locations may be 

suitable for artificial water inputs.

Currently occupied habitats are those that dry periodically to discourage non-native predators and 

competitors while still staying moist enough to allow survival of leopard frogs. These areas will be subject to 

further drying that will eventually make them unsuitable. Some areas that currently sustain permanent waters 

may actually increase in suitability for leopard frogs as drying occurs and non-natives are extirpated. Warmer 

waters are associated with higher resilience to chytrid fungus, thus higher elevations may become increasingly 

suitable. Dispersal will be critical to survival in the future as habitats change. Translocations could be a viable 

option for future management of this species and should be planned based on predicted future wetland 

conditions along with potential for increased predation or incidence of disease.

Reduction of fuels in upland habitats and adjacent to ponds may help reduce negative impacts on downslope 

leopard frog habitats. Impacts from fire suppression efforts such as construction of fuel breaks or use of 

fire retardants in areas upstream of leopard frog habitats should be minimized. Placement of straw bales 

or other erosion control measures are recommended to protect leopard frog habitats following wildfires 

(SWESA 2008). Conversely, sedimentation may alter hydrology of ponds favorably if non-native predators are 

displaced. Fuel reduction recommendations are not new, but predictions related to future fire occurrence 

make this a critical planning topic.
42 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Chiricahua	
  Leopard	
  Frog	
  (Lithobates	
  chiricahuensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Area	
  and	
  

distribution:

breeding

Is	
  the	
  area	
  or	
  location	
  

of	
  the	
  associated	
  

vegetation	
  type	
  used	
  

for	
  breeding	
  activities	
  

by	
  this	
  species	
  

expected	
  to	
  change?

Chiricahua	
  leopard	
  frogs	
  are	
  found	
  in	
  wetland	
  habitats	
  in	
  

oak,	
  pine	
  forests,	
  and	
  mixed	
  woodlands	
  with	
  some	
  range	
  

extensions	
  into	
  chaparral,	
  grassland,	
  and	
  desert	
  habitats	
  

at	
  elevations	
  from	
  1000–2710 m	
  (USFWS	
  2007).	
  They	
  

occur	
  in	
  various	
  permanent	
  and	
  near-­‐permanent	
  waters.	
  

Wetland	
  habitat	
  area	
  is	
  expected	
  to	
  be	
  reduced	
  in	
  all	
  

these	
  associated	
  upland	
  vegetation	
  types.

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?

Adults	
  breed	
  in	
  various	
  natural	
  and	
  human-­‐made	
  still	
  

waters	
  including	
  livestock	
  tanks	
  and	
  backyard	
  ponds.	
  

Shallow	
  water	
  with	
  emergent	
  vegetation	
  is	
  used	
  for	
  egg	
  

laying	
  in	
  adults	
  (USFWS	
  2007).	
  Waters	
  need	
  to	
  be	
  large	
  

enough	
  to	
  sustain	
  tadpoles	
  several	
  months	
  through	
  

metamorphosis.	
  Suitable	
  breeding	
  waters	
  are	
  expected	
  to	
  

be	
  reduced	
  with	
  greater	
  evaporation	
  from	
  increased	
  

temperatures.

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?	
  

Moist	
  locations	
  are	
  required	
  for	
  hibernation.	
  Deeper	
  

waters	
  and	
  undercut	
  banks	
  provide	
  escape	
  from	
  

predators	
  and	
  potential	
  hibernacula	
  (SWESA	
  2008).	
  

Other	
  leopard	
  frogs	
  hibernate	
  buried	
  in	
  mud	
  of	
  well-­‐

oxygenated	
  streams	
  and	
  ponds	
  (USFWS	
  2007).	
  We	
  

assume	
  similar	
  behavior	
  in	
  the	
  Chiricahua	
  leopard	
  frog.	
  

Moist	
  locations	
  and	
  deep	
  waters	
  are	
  expected	
  to	
  be	
  

reduced.

1

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?

Cover	
  provided	
  by	
  vegetation	
  along	
  the	
  water’s	
  edge	
  

might	
  provide	
  escape	
  from	
  visual	
  predators	
  while	
  

increasing	
  presence	
  of	
  other	
  predators	
  such	
  as	
  snakes	
  

(SWESA	
  2008).	
  Shallow	
  water	
  with	
  emergent	
  vegetation	
  

is	
  used	
  for	
  thermoregulation	
  in	
  adults	
  (USFWS	
  2007).	
  

Aquatic	
  vegetation	
  that	
  is	
  too	
  dense	
  can	
  be	
  detrimental	
  

by	
  reducing	
  water	
  temperatures	
  and	
  availability	
  of	
  

basking	
  sites	
  (SWESA	
  2008).	
  Changes	
  will	
  depend	
  on	
  size	
  

and	
  hydrology	
  of	
  current	
  waters,	
  but	
  may	
  increase	
  as	
  

larger	
  permanent	
  water	
  sources	
  become	
  more	
  

intermittent,	
  warmer,	
  and	
  shallower.	
  

-­1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Temporary	
  pools	
  may	
  be	
  important	
  during	
  movements	
  

(SWESA	
  2008).	
  Based	
  on	
  other	
  ranids	
  in	
  the	
  region,	
  

adults	
  can	
  likely	
  move	
  1	
  mile	
  overland,	
  3	
  miles	
  with	
  

intermittent	
  water	
  sources,	
  and	
  5	
  miles	
  along	
  permanent	
  

waters	
  (USFWS	
  2007).

Dispersal	
  will	
  depend	
  on	
  landscape	
  variables,	
  but	
  this	
  

species	
  has	
  a	
  low	
  ability	
  to	
  disperse	
  compared	
  to	
  other	
  

vertebrates.

1
USDA Forest Service RMRS-GTR-302. 2013. 43

Habitat:	
  Chiricahua	
  Leopard	
  Frog	
  (Lithobates	
  chiricahuensis)

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	
  to	
  move	
  between	
  

breeding	
  and	
  non-­‐breeding	
  areas.

0

Physiology:	
  Chiricahua	
  Leopard	
  Frog	
  (Lithobates	
  chiricahuensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Adults	
  are	
  semi-­‐aquatic	
  and	
  larvae	
  are	
  entirely	
  aquatic.	
  

Chiricahua	
  leopard	
  frogs	
  occur	
  in	
  hot	
  arid	
  environments	
  

of	
  Arizona,	
  New	
  Mexico,	
  and	
  Mexico	
  although	
  distribution	
  

of	
  species	
  is	
  fragmented	
  by	
  aridity	
  that	
  limits	
  pond	
  

habitats	
  (Lannoo	
  2005).	
  Water	
  temperatures	
  at	
  which	
  

eggs	
  have	
  been	
  found	
  in	
  the	
  wild	
  generally	
  range	
  from	
  

about	
  13 °C	
  to	
  30 °C	
  (55 °F	
  to	
  85 °F)	
  (Zweifel	
  1968,	
  

USFWS	
  2007).	
  Temperatures	
  are	
  not	
  likely	
  to	
  be	
  limiting	
  

in	
  aquatic	
  habitats	
  and	
  this	
  species	
  does	
  not	
  occur	
  away	
  

from	
  water	
  where	
  it	
  is	
  prone	
  to	
  dessication.

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?

Periodic	
  drying	
  of	
  individual	
  localities,	
  in	
  part,	
  drives	
  

metapopulation	
  dynamics.	
  Jones	
  and	
  Sredl	
  (2005)	
  

observed	
  apparent	
  local	
  extirpations	
  that	
  coincided	
  with	
  

drought.	
  Extirpation	
  of	
  populations	
  in	
  the	
  Baboquivari	
  

Mountains	
  was	
  attributed	
  to	
  drought	
  and	
  drying	
  of	
  stock	
  

tanks	
  (USFWS	
  2007).	
  Species	
  generally	
  breeds	
  away	
  from	
  

areas	
  prone	
  to	
  flooding.	
  High	
  severity	
  wildfires	
  have	
  also	
  

resulted	
  in	
  extirpation	
  of	
  populations	
  (USFWS	
  2007).	
  

Fires	
  are	
  expected	
  to	
  increase	
  in	
  intensity.

1

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Studies	
  of	
  diurnal	
  surveys	
  indicate	
  that	
  this	
  species	
  is	
  

active	
  early	
  in	
  the	
  day	
  and	
  avoids	
  activity	
  during	
  warmer	
  

air	
  temperatures	
  (USFWS	
  2007).	
  May	
  be	
  further	
  

limitations	
  to	
  activities	
  during	
  the	
  day. 1

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

None	
  known.

0

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic. -­1
44 USDA Forest Service RMRS-GTR-302. 2013.

Phenology:	
  Chiricahua	
  Leopard	
  Frog	
  (Lithobates	
  chiricahuensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Cues Does	
  this	
  species	
  use	
  

temperature	
  or	
  

moisture	
  cues	
  to	
  

initiate	
  activities	
  

related	
  to	
  fecundity	
  or	
  

survival	
  (e.g.,	
  

hibernation,	
  

migration,	
  breeding)?	
  

Water	
  temperature	
  is	
  likely	
  related	
  to	
  timing	
  of	
  egg	
  

laying.	
  Although	
  hibernation	
  has	
  not	
  been	
  studied	
  in	
  this	
  

species,	
  adults	
  are	
  generally	
  inactive	
  when	
  water	
  

temperature	
  is	
  below	
  52 °F	
  (14 °C)	
  from	
  November	
  

through	
  February	
  (USFWS	
  2007).	
  One	
  unpublished	
  

report	
  noted	
  that	
  oviposition	
  appeared	
  to	
  be	
  correlated	
  

with	
  changes	
  in	
  water	
  temperature,	
  and	
  not	
  precipitation	
  

(Lannoo	
  2005).	
  Supporting	
  this	
  view	
  is	
  the	
  observation	
  

that	
  oviposition	
  occurs	
  earlier	
  at	
  lower	
  elevations	
  (Frost	
  

and	
  Platz	
  1983)	
  and	
  Elliott	
  and	
  others	
  (2009)	
  found	
  that	
  

breeding	
  can	
  occur	
  whenever	
  the	
  water	
  temperature	
  

exceeds	
  about	
  57 °F	
  (14 °C).	
  Uses	
  temperature	
  cues	
  for	
  

breeding	
  and	
  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?	
  

Seasonal	
  activity	
  seems	
  to	
  be	
  limited	
  by	
  temperature	
  with	
  

year-­‐round	
  activity	
  and	
  breeding	
  noted	
  at	
  one	
  site	
  in	
  New	
  

Mexico	
  with	
  thermal	
  springs	
  (USFWS	
  2007,	
  SWESA

2008).	
  Egg	
  masses	
  have	
  been	
  reported	
  in	
  all	
  months	
  

except	
  November,	
  December,	
  and	
  January	
  (USFWS	
  2007).	
  

Populations	
  previously	
  identified	
  as	
  the	
  Ramsey	
  Canyon	
  

leopard	
  frog	
  lay	
  eggs	
  February	
  to	
  November	
  (SWESA

2008).	
  Populations	
  below	
  approximately	
  1800	
  m	
  

generally	
  deposited	
  eggs	
  mostly	
  before	
  June,	
  whereas	
  

above	
  1800 m	
  eggs	
  were	
  laid	
  in	
  June,	
  July,	
  and	
  August	
  

(Frost	
  and	
  Platz	
  1983).	
  Expected	
  changes	
  to	
  favorable	
  

breeding	
  times.

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?

Work	
  by	
  Jennings	
  found	
  that	
  frogs	
  were	
  most	
  abundant	
  

when	
  water	
  temperatures	
  were	
  warmer	
  and	
  more	
  egg	
  

masses	
  were	
  found	
  in	
  areas	
  with	
  warmer	
  water,	
  an	
  effect	
  

likely	
  related	
  to	
  increased	
  development	
  of	
  tadpoles	
  

(SWSAT	
  2008).	
  Egg	
  hatching	
  and	
  tadpole	
  development	
  

are	
  faster	
  in	
  warmer	
  temperatures	
  (Jennings	
  1990).	
  This	
  

may	
  help	
  time	
  breeding	
  to	
  favorable	
  conditions	
  as	
  the	
  cue	
  

(water	
  temperature)	
  is	
  directly	
  related	
  to	
  favorable	
  water	
  

conditions	
  for	
  egg	
  and	
  tadpole	
  development.

-­1

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  breeding	
  event	
  a	
  year	
  and	
  although	
  breeding	
  can	
  

occur	
  during	
  most	
  of	
  the	
  year	
  it	
  generally	
  is	
  limited	
  

within	
  a	
  region	
  and	
  few	
  populations	
  breed	
  year	
  round. 1
USDA Forest Service RMRS-GTR-302. 2013. 45

Biotic	
  Interactions:	
  Chiricahua	
  Leopard	
  Frog	
  (Lithobates	
  chiricahuensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Larvae	
  are	
  herbivorous	
  and	
  adults	
  eat	
  a	
  diverse	
  array	
  of	
  

insects	
  (Degenhardt	
  and	
  others	
  1996,	
  USFWS	
  2007).	
  

Christman	
  and	
  Cummer	
  (2005)	
  examined	
  stomach	
  

contents	
  of	
  museum	
  specimens	
  and	
  found	
  the	
  majority	
  to	
  

be	
  aquatic	
  and	
  terrestrial	
  invertebrates.	
  Changes	
  in	
  

invertebrates	
  are	
  expected	
  to	
  be	
  species	
  specific.	
  Larvae	
  

eat	
  algae,	
  which	
  may	
  increase	
  with	
  warmer	
  waters	
  

although	
  too	
  much	
  algae	
  removes	
  oxygen.	
  Based	
  on	
  

mixed	
  predictions,	
  no	
  overall	
  effect	
  is	
  applied.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

There	
  are	
  a	
  large	
  variety	
  of	
  predators	
  for	
  larvae	
  and	
  

adults.	
  Juvenile	
  and	
  adult	
  frogs	
  are	
  likely	
  preyed	
  upon	
  by	
  

fish	
  (native	
  and	
  non-­‐native),	
  American	
  bullfrogs,	
  garter	
  

snakes,	
  birds,	
  variety	
  of	
  mammals	
  (Lannoo	
  2005).	
  

Presence	
  of	
  American	
  bullfrogs,	
  crayfish,	
  and	
  predatory	
  

fish	
  are	
  negatively	
  correlated	
  with	
  presence	
  of	
  this	
  

species	
  (USFWS	
  2007).	
  Although	
  this	
  species	
  currently	
  

only	
  occupies	
  habitats	
  where	
  these	
  predators	
  are	
  not	
  

present,	
  but	
  future	
  interactions	
  are	
  expected	
  to	
  intensify	
  

as	
  aquatic	
  habitats	
  decline.

1

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?	
  

Chytridiomycosis	
  has	
  been	
  identified	
  in	
  populations	
  of	
  

the	
  Chiricahua	
  leopard	
  frog	
  including	
  some	
  from	
  those	
  

previously	
  identified	
  as	
  Ramsey	
  Canyon	
  leopard	
  frog	
  

(USFWS	
  2007).	
  In	
  late	
  1980s,	
  high	
  mortality	
  of	
  this	
  

species	
  in	
  earthen	
  cattle	
  tanks	
  in	
  New	
  Mexico	
  was	
  

observed	
  and	
  “post-­‐metamorphic	
  death	
  syndrome”	
  was	
  

implicated	
  although	
  chytrid	
  fungus	
  may	
  have	
  played	
  a	
  

role	
  (Lannoo	
  2005).	
  Although	
  implicated	
  in	
  declines	
  in	
  

numerous	
  amphibian	
  species	
  including	
  this	
  one,	
  there	
  are	
  

also	
  cases	
  where	
  this	
  species	
  is	
  coexisting	
  with	
  this	
  

disease,	
  thus	
  infection	
  may	
  act	
  synergistically	
  with	
  other	
  

stressors	
  (USFWS	
  2007).	
  In	
  Arizona,	
  die-­‐offs	
  of	
  ranids	
  are	
  

correlated	
  with	
  cooler	
  months	
  (Bradley	
  and	
  others	
  2002).	
  

Survival	
  of	
  frogs	
  with	
  chytrid	
  infection	
  is	
  improved	
  at	
  

sites	
  with	
  warmer	
  waters	
  (USFWS	
  2007).	
  American	
  

bullfrogs,	
  which	
  are	
  important	
  reservoirs	
  for	
  the	
  disease,	
  

however,	
  are	
  expected	
  to	
  be	
  resilient	
  to	
  climate	
  change	
  

increasing	
  transmission	
  rates	
  as	
  limited	
  water	
  sources	
  

become	
  more	
  crowded.	
  Although	
  increase	
  of	
  

susceptibility	
  of	
  amphibians	
  to	
  chytrid	
  fungus	
  with	
  

climate	
  change	
  remains	
  controversial,	
  in	
  this	
  case	
  rather	
  

than	
  predicting	
  a	
  decreased	
  mortality,	
  because	
  of	
  the	
  

effect	
  of	
  warmer	
  waters,	
  we	
  feel	
  any	
  positive	
  effect	
  will	
  be	
  

counterbalanced	
  with	
  increased	
  transmission	
  and	
  

potentially	
  synergistic	
  effects	
  with	
  other	
  stressors	
  related	
  

to	
  greater	
  variability	
  in	
  rainfall.	
  

0
46 USDA Forest Service RMRS-GTR-302. 2013.

Biotic	
  Interactions:	
  Chiricahua	
  Leopard	
  Frog	
  (Lithobates	
  chiricahuensis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Current	
  range	
  is	
  considered	
  limited	
  by	
  presence	
  of	
  non-­‐

native	
  predators	
  such	
  as	
  crayfish,	
  bullfrogs,	
  and	
  fish	
  

(USFWS	
  2007).	
  American	
  bullfrog	
  tadpoles	
  reduce	
  algae	
  

food	
  resources	
  available	
  for	
  leopard	
  frog	
  tadpoles	
  (Boone	
  

and	
  others	
  2004).	
  Although	
  competition	
  with	
  non-­‐natives	
  

is	
  currently	
  low	
  in	
  habitats	
  occupied,	
  we	
  do	
  expect	
  

competition	
  with	
  larvae	
  or	
  tadpoles	
  of	
  other	
  amphibians	
  

such	
  as	
  tiger	
  salamander	
  to	
  increase	
  as	
  wetland	
  areas	
  

shrink.

1
USDA Forest Service RMRS-GTR-302. 2013. 47

Literature Cited

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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Boone, M., E. Little, and R. Semlitsch. 2004. Overwintered bullfrog tadpoles negatively affect salamanders and 

anurans in native amphibian communities. Copeia 2004:683-690.

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.

Calfee, R. D. and E. E. Little. 2003. The effects of ultraviolet-B radiation on the toxicity of fire-fighting 

chemicals. Environmental Toxicology and Chemistry 22:1525-1531.

Christman, B. L., and M. R. Cummer. 2005. Food habits of Chiricahua leopard frogs (Rana chiricahuensis) and 

Plains leopard frogs (Rana blairi) in New Mexico. Final Report to New Mexico Share with Wildlife.

Elliott, L., C. Gerhardt, and C. Davidson. 2009. The Frogs and Toads of North America. Houghton, Miflin, 

Harcourt, Boston, MA.

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

Frost, D., T. Grant, J. Faivovich, [and others]. 2006. The amphibian tree of life. Bulletin of the American 

Museum of Natural History 297.

Frost, J. and J. Platz. 1983. Comparative assessment of modes of reproductive isolation among four species of 

leopard frogs (Rana pipiens complex). Evolution 37:66-78. 

Garfin, G. and M. Lenart. 2007. Climate Change Effects on Southwest Water Resources. Southwest Hydrology 

6:16-17. 

Goldberg, C. S., K. J. Field, and M. J. Sredl. 2004. Mitochondrial DNA sequences do not support species status 

of the Ramsey Canyon leopard frog (Rana subaquavocalis). Journal of Herpetology 38:313-319.

Hillis, D. M., and T. P. Wilcox. 2005. Phylogeny of New World true frogs (Rana). Molecular Phylogenetics and 

Evolution 34:299-314. 

Jones, L. and M. Sredl. 2005. Chiricahua leopard frog status in the Galiuro Mountains, Arizona, with a 

monitoring framework for the species’ entire range. Pages 88-91 in G. J. Gottfried, B. S. Gebow, L. G. Eskew, 

C. B. Edminster, tech. eds., Connecting mountain islands and desert seas: biodiversity and management of 

the Madrean Archipelago II. Proceedings, RMRS-P-36. U.S. Department of Agriculture, Forest Service, Rocky 

Mountain Research Station, Fort Collins, CO.

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.

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.

Lannoo, M. J. 2005. Amphibian declines: the conservation status of United States species. University of 

California Press, Berkeley, CA.

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

climate change impact studies. Eos Transations, American Geophysical Union 88:504.
48 USDA Forest Service RMRS-GTR-302. 2013.

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.

Neary, D. G., P. F. Ffolliott, and J. D. Landsberg. 2005. Chapter 5: Fire and Streamflow Regimes. Pages 107-118 

in D. G. Neary, K. C. Ryan, and L. F. DeBano, eds. Wildland fire in ecosystems: effects of fire on soils and 

water. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Gen. Tech. Rep. 

RMRS-GTR-42-vol.4.

Pilliod, D. S., R. B. Bury, E. J. Hyde, C. A. Pearl, and P. S. Corn. 2003. Fire and amphibians in North America. 

Forest Ecology and Management 178:163–181.

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.

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.

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

climate in southwestern North America. Science, 316:1181–1184.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

SWESA (Southwest Endangered Species Act Team). 2008. Chiricahua leopard frog (Lithobates [Rana]

chiricahuensis): Considerations for making effects determinations and recommendations for reducing 

and avoiding adverse effects. U.S. Fish and Wildlife Service, New Mexico Ecological Services Field Office, 

Albuquerque, New Mexico.

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

USFS (United States Forest Service). 2011. Monument Burned Area Report Assessment. Report FS-2500-8.

USFWS (United States Fish and Wildlife Service). 2007. Chiricahua Leopard Frog (Rana chiricahuensis) 

Recovery Plan. U.S. Fish and Wildlife Service, Southwest Region, Albuquerque, NM.

Wallace, J. E. 2006. Effects of wildland fire on lowland leopard frogs and their habitat in the Santa Catalina 

and Rincon Mountains, Coronado National Forest. Final Report to Coronado National Forest, Santa Catalina 

Ranger District, Tucson, Arizona.

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

role of ecophysiology. Biological Invasions 2:123–140.

Zweifel, R. G. 1968. Reproductive biology of anurans of the arid southwest, with emphasis on adaptation of 

embryos to temperature. Bulletin of the American Museum of Natural History 140: Article 1.
USDA Forest Service RMRS-GTR-302. 2013. 49

Arizona Treefrog (Hyla wrightorum)

SUMMARY

Threats related to habitat for the Arizona treefrog will likely increase with projected climate change. In addition, small population size and isolation from other populations will intensify extinction risk. Reduced rainfall 

and increased temperatures will threaten important temporary waters but may increase suitability of some 

currently permanent waters by creating more intermittent reaches. Reproductive failure from alteration of 

monsoon timing is additionally a concern. Potential benefits are likely to be overshadowed by the large number of intensifying threats expected. 

Introduction

In the past, Arizona treefrog was grouped with Hyla eximia. It inhabits wetlands or streams in pine, oak, and 

mixed forests in Arizona, mostly at elevations above 5000 ft (Brennan and Holycross 2006). Populations in the 

Huachuca Mountains and Canelo Hills are disjunct from other populations in Arizona and Mexico and may 

be a separate species based on genetic, call, and morphological differences (Gergus and others 2004, ENRD 

2006). Known as the Huachuca treefrog (ENRD 2006), these disjunct populations are candidates for Federal 

listing, reviewed as of November 2009. Breeding habitats currently very limited. The Huachuca/Canelo distinct 

population segment is known from fewer than 20 localities, 11 of which have confirmed observations of the 

frog in the last 10 years (USFWS 2008). 

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 3.6 14%

Physiology 0.7 17%

Phenology 2.5 25%

Interactions 1.0 40%

Overall 8.0 23%

-5 0 5 
50 USDA Forest Service RMRS-GTR-302. 2013.

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

The USFWS (2008) has identified a number of threats to this species. The most significant threats are high 

severity wildfires that result in habitat loss or direct mortality; drought; floods; introduced predator species; 

and habitat degradation caused by livestock grazing, off-highway vehicles, and environmental contamination. 

Limb deformities have been observed in this species (USFWS 2008). High severity wildfire, drought, and floods 

will all likely become more frequent or intense with climate change projected for the region, thus increasing 

these threats. Habitat decline and physiological stress due to drought and drying associated with future 

climate change were also noted as warranting review of this species for endangered status (USFWS 2012). 

Long-term survival of this species is also threatened by its occurrence in small, disjunct populations. Climate 

change will likely further reduce connectivity among populations and exacerbate this problem.

Research Needs

Monitoring of this species difficult, because breeding choruses of male Arizona treefrogs only last 2-3 days 

(Brennan and Holycross 2006). To restore or expand populations, there is a need to know if predator removal 

would be effective to increase suitable habitats. A related question that needs study is if the current use of 

temporary pools is a recent response to increased predation, or are permanent waters unsuitable for other 

reasons? These questions have implications for effective management of this species.

Management Implications

Forest management to reduce the risk of high intensity wildfires will help to protect treefrog habitats. In 

addition, management that promotes isolating temporary pools from sources of predators and competitors 

will be beneficial. A multispecies approach to management will be required because of the conflicting needs 

of species of more permanent waters. It may be, however, that increasingly dry conditions may increase 

suitability of some currently permanent water sources that support large numbers of aquatic predators. 

Potential suitable habitats of the future should be evaluated based on surface water projections, proximity 

to current treefrog populations, aquatic predator population projections, and potential for dispersal. 

Reproductive failure from alteration of monsoon timing is additionally a concern, particularly if rainfall 

quantity is greatly reduced or arrival is late. Monitoring and/or intervention may be needed during years of 

weak or late monsoons especially if these periods are prolonged or occur over several years. Management 

actions related to stock tanks should consider impacts and benefits to this species including the potential for 

breeding and disease transmission.
USDA Forest Service RMRS-GTR-302. 2013. 51

Habitat:	
  Arizona	
  treefrog	
  (Hyla	
  wrightorum)

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?

Live	
  in	
  ponderosa	
  pine,	
  oak,	
  and	
  mixed	
  forests.	
  Seem	
  to	
  

prefer	
  mesic	
  oak	
  habitats	
  and	
  wet	
  seeps	
  during	
  the	
  day	
  

(USFWS	
  2008).	
  Also	
  heard	
  calling	
  from	
  tree	
  tops	
  and	
  

found	
  under	
  rocks	
  and	
  logs.	
  Ponderosa	
  pine,	
  oak,	
  and	
  

mixed	
  forests	
  are	
  subject	
  to	
  increasing	
  fire	
  occurrence	
  

with	
  climate	
  change,	
  which	
  is	
  likely	
  to	
  reduce	
  habitats.

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?	
  

Breed	
  mostly	
  in	
  temporary	
  water	
  sources	
  that	
  lack	
  

predators	
  (Brennan	
  and	
  Holycross	
  2006),	
  including	
  stock	
  

tanks	
  and	
  intermittent	
  streams.	
  Not	
  known	
  if	
  these	
  are	
  

required	
  breeding	
  habitats	
  or	
  if	
  they	
  have	
  been	
  

extirpated	
  from	
  more	
  permanent	
  waters	
  because	
  of	
  large	
  

numbers	
  of	
  native	
  and	
  non-­‐native	
  predators.	
  Eggs	
  have	
  

been	
  found	
  in	
  permanent	
  waters	
  (NatureServe	
  2009).	
  

Egg	
  masses	
  attached	
  to	
  vegetation	
  just	
  below	
  the	
  surface	
  

(NatureServe	
  2009).	
  Use	
  waters	
  with	
  abundant	
  

vegetation	
  along	
  the	
  shoreline	
  (USFWS	
  2008).	
  Permanent	
  

and	
  temporary	
  water	
  likely	
  to	
  be	
  reduced	
  with	
  higher	
  

temperatures.

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?	
  

Non-­‐breeding	
  individuals	
  are	
  found	
  in	
  trees	
  or	
  in	
  moist	
  

locations	
  such	
  as	
  leaf	
  litter	
  or	
  burrowed	
  in	
  the	
  soil.	
  One	
  

individual	
  found	
  wintering	
  in	
  a	
  debris	
  pile	
  (Brennan	
  and	
  

Holycross	
  2006).	
  Also	
  been	
  found	
  in	
  winter	
  under	
  

boulders	
  and	
  in	
  a	
  deep	
  rock	
  fissure	
  (USFWS	
  2008).	
  Trees,	
  

leaf	
  litter,	
  and	
  debris	
  are	
  prone	
  to	
  fires.

1

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Not	
  known.	
  

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Movements	
  are	
  generally	
  limited	
  in	
  hylid	
  frogs	
  

(NatureServe	
  2009).	
  Low	
  mobility. 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.

0
52 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Arizona	
  treefrog	
  (Hyla	
  wrightorum)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Inactive	
  in	
  cold	
  or	
  dry	
  weather	
  (NatureServe	
  2009)	
  May	
  

be	
  prone	
  to	
  desiccation	
  in	
  non-­‐breeding	
  habitats.	
  

Although	
  there	
  may	
  be	
  some	
  reduction	
  for	
  low	
  

temperature	
  limits,	
  this	
  species	
  is	
  likely	
  prone	
  to	
  

desiccation	
  away	
  from	
  water.

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?	
  

Not	
  known.

0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Nocturnal	
  behavior	
  may	
  help	
  buffer	
  from	
  very	
  hot	
  

conditions.	
  No	
  anticipated	
  limitations	
  for	
  daily	
  activity.

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.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic. -­1
USDA Forest Service RMRS-GTR-302. 2013. 53

Phenology:	
  Arizona	
  treefrog	
  (Hyla	
  wrightorum)

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)?	
  

Breed	
  at	
  the	
  beginning	
  of	
  the	
  summer	
  monsoon	
  season.	
  

Breeding	
  is	
  short,	
  lasting	
  2-­‐8	
  days	
  in	
  H.	
  eximia	
  (BISON-­‐M).	
  

Adults	
  leave	
  breeding	
  habitats	
  shortly	
  after	
  breeding.	
  

Metamorphosis	
  takes	
  6	
  to	
  11	
  weeks	
  (Brennan	
  and	
  

Holycross	
  2006).	
  Breeding	
  may	
  not	
  be	
  solely	
  triggered	
  by	
  

rain	
  as	
  individuals	
  in	
  Scotia	
  Canyon	
  failed	
  to	
  breed	
  in	
  a	
  

year	
  when	
  temporary	
  pools	
  formed	
  late	
  and	
  despite	
  

presence	
  of	
  permanent	
  water	
  sources	
  (USFWS	
  2008).

Breeding	
  seems	
  to	
  be	
  triggered	
  by	
  more	
  than	
  just	
  rainfall.	
  

Maybe	
  temperature	
  or	
  circadian	
  rhythms,	
  but	
  cues	
  

unknown.

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?	
  

Needs	
  ponds	
  from	
  January	
  to	
  June	
  for	
  breeding.	
  Timing	
  of	
  

availability	
  of	
  ponds	
  is	
  likely	
  to	
  change	
  with	
  changes	
  in	
  

seasonal	
  rainfall.

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?

Failure	
  to	
  breed	
  with	
  late	
  monsoons	
  indicates	
  some	
  lack	
  

of	
  timing	
  flexibility,	
  although	
  breeding	
  is	
  not	
  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	
  (NatureServe	
  2009).

1
54 USDA Forest Service RMRS-GTR-302. 2013.

Biotic	
  Interactions:	
  Arizona	
  treefrog	
  (Hyla	
  wrightorum)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Adults	
  probably	
  eat	
  various	
  small	
  invertebrates.	
  Larvae	
  

probably	
  eat	
  algae,	
  organic	
  debris,	
  and	
  plant	
  tissue	
  

(NatureServe	
  2009).	
  No	
  overall	
  prediction	
  for	
  wide	
  

variety	
  of	
  food	
  resources.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Predation	
  thought	
  to	
  be	
  reduced	
  by	
  use	
  of	
  terrestrial	
  

refuges	
  during	
  the	
  day	
  (USFWS	
  2008).	
  Eaten	
  by	
  tiger

salamanders.	
  Ponds	
  where	
  they	
  breed	
  are	
  generally	
  too	
  

ephemeral	
  for	
  bullfrogs,	
  thus	
  reduced	
  predation	
  threat	
  as	
  

compared	
  to	
  some	
  other	
  frog	
  species	
  (USFWS	
  2008).	
  

Mostly	
  avoid	
  aquatic	
  predation	
  in	
  temporary	
  ponds	
  and	
  

terrestrial	
  habits.	
  Other	
  sources	
  of	
  predation	
  are	
  not	
  

known.

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?	
  

Limb	
  deformities	
  are	
  often	
  caused	
  by	
  trematode,	
  

Ribeiroia	
  ondatrae,	
  possibly	
  interacting	
  in	
  synergy	
  with	
  

toxins	
  or	
  introduced	
  fish	
  (Johnson	
  and	
  Sutherland	
  2003).	
  	
  

Snails	
  are	
  an	
  intermediate	
  host	
  and	
  are	
  often	
  abundant	
  in	
  

cattle	
  ponds	
  (Johnson	
  and	
  Lunde	
  2005	
  in	
  USFWS	
  2008).	
  

Presence	
  of	
  intermediate	
  hosts	
  such	
  as	
  snails,	
  other	
  

amphibians,	
  and	
  wading	
  birds	
  as	
  well	
  as	
  factors	
  related	
  to	
  

transmission	
  to	
  growing	
  tadpoles	
  such	
  as	
  low	
  growth	
  

rates	
  or	
  inactivity	
  in	
  response	
  to	
  predators	
  (Johnson	
  and	
  

Sutherland	
  2003).	
  Chytridiomycosis	
  not	
  identified	
  in	
  wild	
  

populations,	
  but	
  individuals	
  have	
  been	
  infected	
  in	
  

laboratory	
  setting	
  (USFWS	
  2008).	
  Exposure	
  to	
  

chytridiomycosis	
  as	
  transferred	
  from	
  leopard	
  frogs	
  or	
  

bullfrogs	
  is	
  likely	
  small	
  in	
  temporary	
  ponds,	
  but	
  the	
  role	
  

of	
  this	
  species	
  as	
  a	
  carrier	
  should	
  be	
  noted.	
  Exposure	
  to	
  

trematodes	
  in	
  stock	
  tanks	
  and	
  although	
  there	
  is	
  no	
  

known	
  relationship	
  of	
  infection/limb	
  deformity	
  with	
  

projected	
  climate	
  change,	
  use	
  of	
  stock	
  tanks	
  may	
  increase	
  

as	
  natural	
  waters	
  decline.

1

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

May	
  compete	
  with	
  American	
  bullfrog,	
  but	
  competition	
  

limited	
  by	
  use	
  of	
  terrestrial	
  retreats. 0
USDA Forest Service RMRS-GTR-302. 2013. 55

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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Brennan, T. C. and A. T. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game 

and Fish Department. Phoenix, AZ.

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

Garfin, G. and M. Lenart. 2007. Climate Change Effects on Southwest Water Resources. Southwest Hydrology 

6:16–17. 

Gergus, E. W. A., T. W. Reeder, B. K. Sullivan, and M. E. Douglas. 2004. Geographic Variation in Hyla 

wrightorum: Advertisement calls, allozymes, mtDNA, and morphology. Copeia. 2004:758-769.

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.

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.

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. Available online from http://www.natureserve.org/explorer. (Accessed: 

May 31, 2010).

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.

Seager, R., M. Ting, 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.

Stromberg, Juliet, S. J. Lite, T. J. Rychener, L. R. Levick, M. D. Dixon, J. M. 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.

USFWS (United States Fish and Wildlife Service). 10 April 2012. Species Assessment and Listing Priority 

Assignment Form. Southwest Region. Available at http://ecos.fws.gov/docs/candidate/assessments/2013/

r2/D03S_V02.pdf.

USFWS (United States Fish and Wildlife Service). 2008. Arizona treefrog (Huachuca/Canelo DPS) (Hyla 

wrightorum). Arizona Ecological Services Field Office. 1 page.

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

role of ecophysiology. Biological Invasions 2:123-140.
56 USDA Forest Service RMRS-GTR-302. 2013.

Desert Massasauga 

(Sistrurus catenatus edwardsi)

SUMMARY

Desert massasauga has very limited populations and is vulnerable to extirpation from the United States, thus 

any increase in threat is of concern. Habitat requirements for desert massasauga are not well understood 

making predictions about climate change effects uncertain although an increase in overall vulnerability is 

expected. This species may experience some expansion of habitats as local climate change conditions favor 

grasslands. At the same time, however, invasive grasses are expected to increase with unknown consequences 

for suitability of this species’ habitats. Additionally, this species is vulnerable to declines based on phenological characteristics, particularly timing of monsoonal rains. 

Introduction

Desert massasauga is designated as a species of greatest conservation need, Tier 1A, in Arizona State Wildlife 

Action Plan or SWAP (AGFD 2006) and as sensitive by the USDA Forest Service. It is currently only known in 

Arizona from Sulphur Springs and San Bernardino Valleys (AGFD 2001). There is an historic record from Fort 

Huachuca, but this species may now be extirpated. The massasauga is widespread, but the desert subspecies 

is only found in a few disjunct populations in southeast Arizona, southeast Colorado, southern New Mexico 

and northern Mexico (Stebbins 1985). 

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat -1.8 29%

Physiology 1.5 33%

Phenology 3.8 50%

Interactions 0.0 60%

Overall 2.2 41%

-5 0 5 
USDA Forest Service RMRS-GTR-302. 2013. 57

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

Based on its association with seasonal wetlands and its very limited populations, this subspecies is considered 

vulnerable to extinction with a warming climate (Greene 1994). Limited distribution will interact with any 

declines associated with climate change or other threats to increase risk of extirpation. Habitat loss from 

agriculture cited as major factor in declines as well as habitat degradation due to overgrazing (AGFD 2001). 

The massasauga is also prone to mortality on highways. Grazing is likely to interact with climate change as 

behaviors and populations of grazing animals change along increasing variability in vegetative growth, but no 

information is available related to how grazing impacts these snakes.

Fires are expected to become more frequent as rainfall becomes more variable and temperatures rise. 

In addition to temperature interactions, projected increases in climate variability will also increase fire 

occurrence as years of high rainfall are followed by dry/hot years creating conditions conducive both 

to ignition and fuel accumulation. Buffelgrass (Pennisetum ciliare), in addition to the already common 

Lehmann’s lovegrass (Eragrostis lehmanniana), is rapidly expanding and is becoming increasingly problematic 

in the Sonoran Desert. 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. Fires and non-native 

grass invasions will encourage greater conversion to grasslands with unknown changes to habitat suitability 

for the desert massasauga. 

Research Needs

Factors that led to population declines and the current disjunct distribution are mostly unknown. If grazing 

is a major threat, more information is needed on grazing variables that impact massasauga populations. 

Knowledge of the effects of non-native grasses on massasauga habitats will be critical as these grasses 

spread and invade native grasslands. Timing of monsoonal rains coincides with births, but the nature of this 

relationship is unknown making predictions difficult and beneficial management actions uncertain. Due to the 

current limited populations, an evaluation of suitable habitats and potential for dispersal is needed to design 

management intervention for this subspecies.

Management Implications

All populations are critical to survival of this subspecies in the United States, although massasauga is not 

generally of current management concern at Fort Huachuca as it appears to be extirpated. In addition, 

livestock grazing is limited at the Fort, thus any grazing impacts will be from native grazers. If massasaugas are 

found to be present in the area, management related to fire and invasive grasses will be critical to maintaining 

habitat for this species. Management actions that maintain water table levels will also be important to 

protecting seasonally wet grasslands.
58 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Desert	
  Massasauga	
  (Sistrurus	
  catenatus	
  edwardsi)

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	
  subspecies	
  occupies	
  desert	
  grasslands	
  in	
  Arizona,	
  

but	
  also	
  known	
  from	
  oak	
  woodlands	
  in	
  New	
  Mexico.	
  

Grasslands	
  may	
  increase	
  as	
  woodlands	
  retreat	
  to	
  higher	
  

elevations	
  and	
  fires	
  increase. -­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?	
  

Availability	
  of	
  burrows	
  is	
  not	
  expected	
  to	
  change.	
  More	
  

specific	
  requirements	
  are	
  unknown.

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?	
  

Hibernates	
  and	
  uses	
  burrows,	
  vegetation,	
  or	
  leaf	
  litter	
  for	
  

refuges	
  (Holycross	
  2003).	
  Availability	
  of	
  burrows	
  

expected	
  to	
  stay	
  the	
  same.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Associated	
  with	
  grasslands	
  that	
  are	
  seasonally	
  wet	
  

(Greene	
  1994),	
  which	
  may	
  improve	
  conditions	
  for	
  

foraging.	
  More	
  mesic	
  conditions	
  are	
  partly	
  dependent	
  on	
  

variables	
  such	
  as	
  topography	
  and	
  soils,	
  but	
  drying	
  is	
  

expected	
  with	
  warmer	
  temperatures	
  and	
  greater	
  

evaporation.

1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Radio-­‐tracked	
  individuals	
  (S.	
  catenatus)	
  had	
  large	
  home	
  

ranges	
  and	
  movements	
  in	
  Colorado	
  (NatureServe	
  2009).	
  

Known	
  to	
  move	
  seasonally	
  between	
  habitats	
  in	
  some	
  

regions	
  (NatureServe	
  2009)	
  suggesting	
  that	
  mobility	
  is	
  

not	
  limited.

-­1

7.	
  Migratory	
  or	
  

transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

Unknown	
  if	
  move	
  seasonally	
  in	
  Arizona.

0
USDA Forest Service RMRS-GTR-302. 2013. 59

Physiology:	
  Desert	
  Massasauga	
  (Sistrurus	
  catenatus	
  edwardsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Limited	
  information.	
  Occurs	
  in	
  a	
  wide	
  range	
  of	
  habitats	
  

and	
  conditions	
  throughout	
  range.	
  Often	
  in	
  vegetation	
  

associations	
  with	
  wetland	
  habitats	
  (NatureServe	
  2009).	
  

Fort	
  Huachuca	
  is	
  part	
  of	
  hottest	
  and	
  driest	
  part	
  of	
  the	
  

range	
  and	
  conditions	
  may	
  be	
  near	
  thresholds.	
  

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.

0

4.	
  Limitations	
  

to	
  daily	
  activity

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Primarily	
  nocturnal	
  in	
  the	
  summer,	
  but	
  also	
  days	
  when	
  

conditions	
  are	
  cooler.	
  More	
  surface	
  activity	
  is	
  observed	
  

following	
  monsoonal	
  rains	
  (Holycross	
  2003).	
  Apparently	
  

is	
  flexible	
  in	
  diurnalversus	
  nocturnal	
  activity	
  preference	
  

(NatureServe	
  2009).	
  Changes	
  to	
  rainfall	
  timing	
  and	
  

greater	
  evaporation	
  are	
  likely	
  to	
  reduce	
  wet	
  periods	
  

associated	
  with	
  activity.

1

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

No	
  known	
  strategies.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic.

-­1
60 USDA Forest Service RMRS-GTR-302. 2013.

Phenology:	
  Desert	
  Massasauga	
  (Sistrurus	
  catenatus	
  edwardsi)

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)?	
  

More	
  surface	
  activity	
  is	
  observed	
  following	
  monsoonal	
  

rains	
  (Holycross	
  2003).	
  Rainfall	
  is	
  potentially	
  a	
  cue.	
  

Temperature	
  is	
  likely	
  a	
  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?	
  

Extended	
  breeding	
  season	
  through	
  much	
  of	
  the	
  year	
  

although	
  births	
  may	
  be	
  limited	
  to	
  August	
  and	
  September	
  

(Holycross	
  2003).	
  Not	
  known	
  if	
  this	
  timing	
  relates	
  to	
  

monsoonal	
  rains,	
  but	
  seem	
  possible	
  considering	
  the	
  late	
  

dates	
  of	
  births.	
  Monsoonal	
  rains	
  are	
  subject	
  to	
  changes	
  in	
  

timing.

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?

Critical	
  resources	
  are	
  not	
  known.

0

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Females	
  probably	
  do	
  not	
  reproduce	
  every	
  year	
  (Goldberg	
  

and	
  Holycross	
  1999). 1

Biotic	
  Interactions:	
  Desert	
  Massasauga	
  (Sistrurus	
  catenatus	
  edwardsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Venomous.	
  Eats	
  mostly	
  lizards	
  and	
  small	
  mammals,	
  but	
  

also	
  centipedes,	
  spadefoots,	
  and	
  small	
  snakes	
  (Holycross	
  

2003).	
  No	
  expected	
  overall	
  changes	
  in	
  wide	
  variety	
  of	
  

food	
  items.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

No	
  important	
  predators	
  known.

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?	
  

None	
  known.

0
USDA Forest Service RMRS-GTR-302. 2013. 61

Biotic	
  Interactions:	
  Desert	
  Massasauga	
  (Sistrurus	
  catenatus	
  edwardsi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

None	
  known,	
  although	
  may	
  compete	
  with	
  other	
  snake	
  

species	
  for	
  food.	
  Similar	
  snake	
  species	
  are	
  likely	
  to	
  have	
  

the	
  same	
  vulnerabilities	
  to	
  climate	
  change.

0
62 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

AGFD (Arizona Game and Fish Department). 2001. Desert Massasauga. Unpublished abstract compiled and 

edited by the Heritage Data Management System, Arizona Game and Fish Department, Phoenix, AZ.

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool.

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.

Goldberg, S. R., and A. T. Holycross. 1999. Reproduction in the desert massasauga, Sistrurus catenatus 

edwardsii, in Arizona and Colorado. Southwestern Naturalist 44:531–535.

Greene, Harry W. 1994. Systematics and natural history, foundations for understanding and conserving 

biodiversity. American Zoologist 34:48–56.

Holycross, A. T. 2003. Desert massasauga (Sistrurus catenatus edwardsii). Sonoran Herpetologist 16:30–32.

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.

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.

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. Available online from http://www.natureserve.org/explorer. (Accessed: 

July 12, 2010).

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.

Seager, R., M. Ting, 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.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

Stebbins, R.C. 1985. A Field Guide to Western Reptiles and Amphibians. Second edition. Houghton Mifflin 

Company, Boston, Massachusetts.

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

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

role of ecophysiology. Biological Invasions 2:123–140.
USDA Forest Service RMRS-GTR-302. 2013. 63

Arizona Ridge-nosed Rattlesnake 

(Crotalis willardi willardi)

SUMMARY

Arizona ridge-nosed rattlesnake occupies high mountain refugia in southeastern Arizona and is expected to be 

vulnerable to declines associated with future climate change. Various aspects of this species’ life history contributed to vulnerability, but the largest contribution was traits associated with timing or phenology. Management related to increasing forest resiliency to high severity fires and drought will be important.

Introduction

Arizona ridge-nosed rattlesnake is known to occur on Fort Huachuca. It is a species of greatest conservation 

need, Tier 1A Arizona State Wildlife Action Plan or SWAP (AGFD 2006), and designated as a species at risk 

(SWESA 2006). It does not have Federal protection, but another subspecies, the New Mexican ridge-nosed 

rattlesnake, C. w. obscurus, is Federally threatened. Examination of systematics in these subspecies suggests 

that C. w. willardi may be the most distinct of the subspecies (Greene 1994).

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

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

Collecting of the New Mexican subspecies is considered a major threat and is likely to also threaten this 

subspecies. It has been suggested that this species is moderately vulnerable to climate change but can survive 

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 2.1 43%

Physiology 1.5 17%

Phenology 3.8 50%

Interactions 1.0 60%

Overall 8.0 41%

-5 0 5 
64 USDA Forest Service RMRS-GTR-302. 2013.

in mountain refuges as it has during past climate change (Greene 1994). Isolation and shrinking habitats 

suggest future population declines, as does the outcome of this assessment. Small populations will be 

vulnerable to extirpation from various threats and Allee effects. 

Research Needs

Many life history aspects and habitat requirements are not well known in this species. Variables related to 

canopy and fire history are important. Canopy or understory requirements and preferences are not known but 

will be important to guiding forest thinning or prescribed fire applications. Population dynamics, measures of 

habitat suitability, or energetics as measured along an elevational gradient would help predict future impacts. 

Management Implications

Fuels and fire management will be important to the extent that vegetation associations and preferred 

habitats are maintained, but it is difficult to predict how this species will respond to fire. High severity fires 

that remove the majority of canopy cover and leave little refugia, however, are likely to be detrimental. High 

densities of trees can increase fire severity and susceptibility of trees to drought; thus, thinning or prescribed 

fire may be useful for increasing resiliency to climate change effects for this species.
USDA Forest Service RMRS-GTR-302. 2013. 65

Habitat:	
  Arizona	
  Ridge-­nosed	
  Rattlesnake	
  (Crotalis	
  willardi	
  willardi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Area	
  and	
  

distribution:

breeding

Is	
  the	
  area	
  or	
  location	
  

of	
  the	
  associated	
  

vegetation	
  type	
  used	
  

for	
  breeding	
  activities	
  

by	
  this	
  species	
  

expected	
  to	
  change?

Occurs	
  in	
  Madrean	
  oak	
  and	
  coniferous	
  forests	
  (Brennan	
  

and	
  Holycross	
  2006).	
  These	
  habitats	
  are	
  expected	
  to	
  

decline	
  as	
  they	
  shift	
  upslope. 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?	
  

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?	
  

Dens	
  are	
  used	
  for	
  hibernation.	
  Variety	
  of	
  types	
  and	
  

locations	
  not	
  expected	
  to	
  change	
  overall.

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?

Daily	
  movements	
  are	
  limited	
  (NatureServe	
  2009).	
  

Presence	
  of	
  roads	
  was	
  found	
  to	
  effectively	
  isolate	
  

populations	
  of	
  timber	
  rattlesnake	
  (Clark	
  and	
  others

2010);	
  thus,	
  effective	
  dispersal	
  may	
  be	
  limited	
  with	
  

current	
  road	
  networks.

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
66 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Arizona	
  Ridge-­nosed	
  Rattlesnake	
  (Crotalis	
  willardi	
  willardi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Apparently	
  intolerant	
  of	
  desert	
  conditions.	
  Current	
  

genetic	
  isolation	
  and	
  speciation	
  in	
  sky	
  islands	
  may	
  be	
  due

to	
  desertification	
  of	
  lower	
  elevations	
  (Holycross	
  and	
  

Douglas	
  2007).	
  May	
  be	
  physiologically	
  intolerant	
  of	
  

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?	
  

Hibernates	
  during	
  the	
  extreme	
  heat	
  or	
  cold	
  (NatureServe	
  

2009).	
  No	
  known	
  response	
  to	
  fire	
  or	
  floods.

0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Activity	
  appears	
  to	
  be	
  somewhat	
  flexible.	
  Although	
  

mostly	
  diurnal,	
  also	
  have	
  some	
  periods	
  of	
  nocturnal	
  and	
  

crepuscular	
  activity	
  (Brennan	
  and	
  Holycross	
  2006).	
  

Greater	
  activity,	
  however,	
  is	
  also	
  associated	
  with	
  rainfall	
  

(NatureServe	
  2009),	
  which	
  is	
  expected	
  to	
  be	
  reduced	
  

with	
  warmer	
  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?

None	
  known.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Ectothermic. -­1

Phenology:	
  Arizona	
  Ridge-­nosed	
  Rattlesnake	
  (Crotalis	
  willardi	
  willardi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Cues Does	
  this	
  species	
  use	
  

temperature	
  or	
  

moisture	
  cues	
  to	
  

initiate	
  activities	
  

related	
  to	
  fecundity	
  or	
  

survival	
  (e.g.,	
  

hibernation,	
  

migration,	
  breeding)?	
  

Timing	
  of	
  hibernation	
  or	
  aestivation	
  is	
  directly	
  related	
  to	
  

temperature.

1

2.	
  Breeding	
  

timing	
  

Are	
  activities	
  related	
  

to	
  species’	
  fecundity	
  

or	
  survival	
  tied	
  to	
  

discrete	
  resource	
  

peaks	
  (e.g.,	
  food,	
  

Births	
  occur	
  late	
  July	
  through	
  August	
  (Holycross	
  and	
  

others	
  2001).	
  This	
  timing	
  is	
  coincident	
  with	
  monsoons,	
  

which	
  may	
  be	
  important	
  for	
  obtaining	
  greater	
  amounts	
  of	
  

prey.	
  Expected	
  changes	
  to	
  timing	
  or	
  variability	
  of	
  

monsoons.

1
USDA Forest Service RMRS-GTR-302. 2013. 67

Phenology:	
  Arizona	
  Ridge-­nosed	
  Rattlesnake	
  (Crotalis	
  willardi	
  willardi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

breeding	
  sites)	
  that	
  

are	
  expected	
  to	
  

change?

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?

Centipedes	
  and	
  lizards	
  may	
  be	
  important	
  food	
  resources	
  

for	
  juveniles,	
  but	
  unknown	
  how	
  timing	
  affects	
  survival.	
  

Not	
  known	
  if	
  rainfall	
  triggers	
  breeding.

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,	
  but	
  individuals	
  may	
  

only	
  breed	
  biennially	
  (Holycross	
  and	
  others	
  2001)

1

Biotic	
  Interactions:	
  Arizona	
  Ridge-­nosed	
  Rattlesnake	
  (Crotalis	
  willardi	
  

willardi)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Eats	
  primarily	
  lizards,	
  centipedes,	
  mice,	
  but	
  also	
  birds	
  

and	
  other	
  invertebrates	
  (Brennan	
  and	
  Holycross	
  1996).	
  

Rodents	
  are	
  generally	
  taken	
  by	
  adults,	
  and	
  centipedes	
  

and	
  lizards	
  are	
  taken	
  more	
  by	
  juveniles	
  (Greene	
  1994).	
  

Wide	
  variety	
  of	
  prey	
  species	
  with	
  no	
  overall	
  expected	
  

change	
  to	
  prey	
  levels.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

No	
  major	
  predators	
  known.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

May	
  den	
  over	
  winter	
  with	
  other	
  individuals	
  as	
  in	
  other	
  

rattlesnakes.	
  More	
  individuals	
  could	
  reduce	
  metabolic	
  

needs	
  and	
  increase	
  survival.	
  Based	
  on	
  other	
  sections	
  of	
  

this	
  assessment,	
  populations	
  may	
  be	
  reduced,	
  thereby

negatively	
  impacting	
  this	
  behavior.

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
68 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool.

Brennan, T. C. and A. T. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game 

and Fish Department. Phoenix, AZ.

Clark, R. W., W. S. Brown, R. Stechert, and K. R. Zamudio. 2010. Roads, interrupted dispersal, and genetic 

diversity in timber rattlesnakes. Conservation Biology 24:1059–1069.

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

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

6:16–17.

Greene, H. W. 1994. Systematics and natural history, foundations for understanding and conserving 

biodiversity. American Zoologist 34:48–56.

Holycross, A. T., S. R. Goldberg, and A. H. Price. 2001. Reproduction in northern populations of the ridgenose 

rattlesnake, Crotalus willardi (Serpentes: Viperidae). Copeia 2001:473–481.

Holycross, A. T. and M. E. Douglas. 2007. Geographic isolation, genetic divergence, and ecological nonexchangeability define ESUs in a threatened sky-island rattlesnake. Biological Conservation 134:142–154.

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.

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

climate change impact studies. Eos Transactions, American Geophysical Union. 88:504.

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. Available online from http://www.natureserve.org/explorer. (Accessed: 

December 2, 2009).

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.

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

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

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

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

role of ecophysiology. Biological Invasions 2:123–140.
USDA Forest Service RMRS-GTR-302. 2013. 69

Northern Mexican Gartersnake 

(Thamnophis eques megalops)

SUMMARY

The northern Mexican gartersnake is largely extirpated from its former range and now only occurs in a few 

isolated populations. We expect climate change to greatly increase its vulnerability to extinction through a 

variety of biological effects. In addition, a number of important current threats such as non-native species and 

loss of riparian habitats will likely be exacerbated. Management related to water table levels, protection of 

riparian areas, and control of invasive species will be critical.

Introduction

The northern Mexican gartersnake is a candidate species for Federal listing as endangered or threatened 

(current as of November 2009) and a species at risk (SWESA 2006). It is a species of greatest conservation 

need, Tier 1A, in Arizona State Wildlife Action Plan or SWAP (AGFD 2006). It occurs in Upper Scotia Canyon, 

Huachuca Mountains and historically occurred on the San Pedro River and Babocamari Cienega (USFWS 2006). 

Northern Mexican gartersnake has been extirpated from approximately 85% of historically occupied locations, 

which has been primarily attributed to the loss and degradation of riparian habitats (USFWS 2006). The 

northern Mexican gartersnake is one of 10 subspecies and the only one in the United States (USFWS 2006).

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• 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.

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY SCORE Uncertainty

Habitat 2.9 29%

Physiology 2.3 17%

Phenology 2.5 25%

Interactions 3.0 40%

Overall 10.8 27%

-5 0 5 
70 USDA Forest Service RMRS-GTR-302. 2013.

Other Threats and Interactions With Climate

Current threats include dams, diversions, groundwater pumping, introduction of non-native species 

(vertebrates, plants, and crayfish), woodcutting, mining, contaminants, urban and agricultural development, 

road construction, livestock grazing, wildfires, and undocumented immigration (USFWS 2006). Multiple 

threats occur at many locations and may work in synergy (USFWS 2006). Erosion and declining water 

tables, which are already implicated in declines, are likely to worsen with warmer temperatures, more 

severe flooding, and increased high severity wildfires. Grazing also can contribute to erosion and changes in 

hydrology as well as alter shoreline vegetation. Warmer temperatures and droughts may further concentrate 

grazing into mesic environments. There is also potential for increasing illegal immigration into the United 

States with climate change. 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 with 

potentially negative impacts for this species.

Research Needs

A number of areas are not well studied in this species. The effect of non-native animal species as predators 

and competitors is well known, but the effect of non-native plants on gartersnake habitats is not well studied 

despite current and future increases in the dominance of these species. Because of the large number of 

threats to this species and synergistic effects, methods for identifying the most effective restoration measures 

are needed.

Management Implications

Management that restricts activities that can degrade riparian habitats will be important. Fuels management 

activities can reduce risk of high severity wildfires that are likely to threaten habitats and food sources. 

Management actions that mitigate climate change impacts for native amphibians and fish will be critical for 

the northern Mexican gartersnake in addition to those species. Control measures for non-native species in 

occupied habitats should improve survival. Declines in non-native fish may be expected with reductions in 

surface waters, which may improve habitats in some areas and could be used to increase success of control 

measures.

Although livestock grazing is limited on Fort Huachuca, native grazers may impact riparian areas during 

droughts. This potential should be evaluated. Stock tanks should be maintained and management should 

consider enhancements related to water retention and emergent vegetation. Protection of localities and 

targeting of management actions should anticipate future conditions and focus on those expected to be more 

resilient to drying.
USDA Forest Service RMRS-GTR-302. 2013. 71

Habitat:	
  Northern	
  Mexican	
  Gartersnake	
  (Thamnophis	
  eques	
  megalops)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  	
  Area	
  and	
  

distribution:

breeding

Is	
  the	
  area	
  or	
  location	
  

of	
  the	
  associated	
  

vegetation	
  type	
  used	
  

for	
  breeding	
  activities	
  

by	
  this	
  species	
  

expected	
  to	
  change?

Occupies	
  riparian	
  habitats	
  from	
  40	
  to	
  2590	
  m	
  (USFWS	
  

2006).	
  Associated	
  with	
  a	
  variety	
  of	
  riparian	
  types	
  from	
  

mesquite	
  grasslands	
  to	
  cottonwood	
  gallery	
  forests	
  

(USFWS	
  2006).	
  It	
  also	
  uses	
  stock	
  tanks	
  (USFWS	
  2006).	
  

Riparian	
  forests	
  are	
  likely	
  to	
  decline	
  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?

Same	
  as	
  above.

1

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?	
  

Associated	
  with	
  ungrazed	
  habitats	
  with	
  high	
  vegetation	
  

density	
  and	
  organic	
  debris.	
  Dense	
  emergent	
  vegetation	
  

along	
  banks	
  is	
  likely	
  important	
  for	
  foraging	
  (USWFS	
  

2006).	
  Likely	
  to	
  be	
  reduced	
  as	
  water	
  tables	
  drop. 1

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Small	
  diameter	
  trees	
  may	
  be	
  important	
  for	
  

thermoregulation	
  and	
  cover	
  from	
  predators	
  (USFWS	
  

2006).	
  Vulnerable	
  to	
  water	
  table	
  declines.

1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Stock	
  tanks	
  may	
  be	
  important	
  for	
  dispersal	
  (USFWS	
  

2006)	
  and	
  likely	
  restricted	
  in	
  dispersal	
  because	
  of	
  

habitat.	
  May	
  be	
  able	
  to	
  disperse	
  long	
  distances	
  during	
  

rainy	
  periods.	
  Likely	
  restricted	
  in	
  ability	
  to	
  disperse	
  

although	
  mobile.

0

7.	
  Migratory	
  or	
  

transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

No.

0
72 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Northern	
  Mexican	
  Gartersnake	
  (Thamnophis	
  eques	
  megalops)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Limited	
  information.	
  Activity	
  restricted	
  to	
  relatively	
  cool	
  

conditions	
  for	
  this	
  region	
  and	
  may	
  indicate	
  low	
  critical	
  

thresholds.	
  May	
  not	
  be	
  tolerant	
  of	
  higher	
  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?	
  

Severe	
  flooding	
  is	
  considered	
  a	
  threat	
  to	
  this	
  species	
  

(USFWS	
  2006).	
  Flooding	
  is	
  expected	
  to	
  become	
  more	
  

intense. 1

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

The	
  northern	
  Mexican	
  gartersnake	
  is	
  surface	
  active	
  at	
  

ambient	
  temperatures	
  ranging	
  from	
  22–33	
   ̊C	
  (USFWS	
  

2006).	
  Time	
  periods	
  suitable	
  for	
  surface	
  activity	
  are	
  likely	
  

to	
  be	
  reduced	
  as	
  temperatures	
  warm.

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:	
  Northern	
  Mexican	
  Gartersnake	
  (Thamnophis	
  eques	
  megalops)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Cues Does	
  this	
  species	
  use	
  

temperature	
  or	
  

moisture	
  cues	
  to	
  

initiate	
  activities	
  

related	
  to	
  fecundity	
  or	
  

survival	
  (e.g.,	
  

hibernation,	
  

migration,	
  breeding)?	
  

Cues	
  not	
  known,	
  but	
  likely	
  combination	
  of	
  external	
  and	
  

internal	
  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?	
  

Mating	
  occurs	
  in	
  April	
  and	
  May	
  with	
  birth	
  of	
  live	
  young	
  in	
  

July	
  and	
  August	
  (USFWS	
  2006).	
  This	
  period	
  may	
  coincide	
  

with	
  monsoonal	
  rains	
  and	
  favorable	
  conditions	
  for	
  

surface	
  activity.	
  Likely	
  to	
  be	
  timing	
  changes. 1
USDA Forest Service RMRS-GTR-302. 2013. 73

Phenology:	
  Northern	
  Mexican	
  Gartersnake	
  (Thamnophis	
  eques	
  megalops)

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	
  large	
  separation	
  between	
  activities	
  and	
  events.

0

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Approximately	
  half	
  of	
  females	
  reproduce	
  in	
  a	
  single	
  year	
  

(USFWS	
  2006).

1

Biotic	
  Interactions:	
  Northern	
  Mexican	
  Gartersnake	
  (Thamnophis	
  eques	
  

megalops)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Eats	
  a	
  variety	
  of	
  amphibians	
  and	
  fish,	
  but	
  thought	
  to	
  

primarily	
  prey	
  on	
  native	
  species	
  (USFWS	
  2006).	
  Most	
  

native	
  amphibians	
  and	
  fish	
  are	
  vulnerable	
  to	
  climate	
  

change	
  and	
  likely	
  to	
  decline.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Large	
  number	
  of	
  predators,	
  but	
  predation	
  by	
  introduced	
  

game	
  fish	
  and	
  American	
  bullfrogs	
  are	
  considered	
  to	
  be	
  a	
  

major	
  threat	
  (USFWS	
  2006).	
  These	
  species	
  are	
  likely	
  

resilient	
  to	
  climate	
  change,	
  at	
  least	
  where	
  water	
  remains.

1

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	
  major	
  diseases	
  (USFWS	
  2006).

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Compete	
  with	
  American	
  bullfrog	
  for	
  food	
  (USFWS	
  2006).	
  

Bullfrogs	
  are	
  likely	
  resilient	
  to	
  climate	
  change. 1
74 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool.

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. Global Environmental 

Change 1:351–364.

Magrin, G., C. Gay García, D. Cruz Choque, [and others]. 2007. Latin America. Pages 581–615 in Climate 

Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth 

Assessment Report of the Intergovernmental Panel on Climate Change, M. L. Parry, O. F. Canziani, J. P. 

Palutikof, P. J. van der Linden and C. E. Hanson, eds., 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.

Robinett, D. 1994. Fire effects on southeastern Arizona Plains grasslands. Rangelands 16:143–148.

Seager, R., M. Ting, 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.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

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

USFWS (United States Fish and Wildlife Service). 2006. 12-Month Finding on a Petition To List the Northern 

Mexican Gartersnake (Thamnophis eques megalops) as Threatened or Endangered With Critical Habitat. 

Federal Register 71:56227–56256.

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.

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

role of ecophysiology. Biological Invasions 2:123–140.
USDA Forest Service RMRS-GTR-302. 2013. 75

Bald Eagle (Haliaeetus leucocephalus)

SUMMARY

Bald eagles winter in southeastern Arizona and are only likely to use Fort Huachuca occasionally as the Fort 

does not support adequate aquatic resources. Warmer temperatures are projected with greater warming in 

winter than in other seasons; thus, changes will likely occur sooner on wintering grounds than in areas where 

eagles only occur in summer. Populations of bald eagles in Arizona were found to be only somewhat more 

vulnerable with climate change projections. Reservoir levels are likely to decline with increasing droughts and 

could impact wintering eagles in the Southwest.

Introduction

Bald eagle was listed as endangered in 1967 in the lower 48 states of the United States, then for 43 states 

in 1978, and ultimately was delisted in the lower 48 states in 1999. In 2004, Southwest populations were 

petitioned as a distinct population segment. Populations in the Sonoran desert were proposed as a distinct 

population and endangered, but USFWS found listing was not warranted (February 2010) although the 

population segment briefly held a status as threatened from 2008 while the status was being reviewed. 

Individuals are only present in winter in southern Arizona. Wintering bald eagles have been seen at Willcox 

Playa, San Pedro, and Parker Canyon Lake, but any occurrence on the Fort is likely transitory (ENRD 2006).

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

-5 0 5 

VULNERABILITY Score Uncertainty

Habitat 1.3 14%

Physiology 0.8 33%

Phenology -0.4 25%

Interactions 0.0 20%

Overall 2.4 23%
76 USDA Forest Service RMRS-GTR-302. 2013.

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

DDT and shooting were important factors in past population declines, but now populations are increasing 

in many areas. Toxins from pesticides and heavy metals, however, continue to threaten this species through 

ingestion of contaminated prey (Buehler 2000). Habitat loss due to human development, particularly along 

shorelines, is still a major threat. On breeding grounds, climate change projections include earlier arrival 

of spring and increasing precipitation. Reproductive success can be reduced by wet and cold weather. The 

outcome will depend on the interaction of phenological changes in bald eagle arrival and phenology of spring 

weather conditions. In addition, earlier arrival on the breeding grounds is associated with better success 

because early individuals have access to the best sites. It is unknown how these timing changes will interact 

to affect breeding and, consequently, wintering populations in Arizona. Although we did not anticipate that 

food resources overall would be reduced, there may be some reductions in Arizona where eagles are primarily 

associated with reservoirs that will shrink with more frequent droughts and greater evaporation.

Research Needs

Many aspects of bald eagle ecology are well studied, but information is more limited on wintering ecology. 

Better information on how aspects of winter habitat may affect population dynamics would be useful. No 

information was available on how droughts may affect bald eagles, but this is an important interaction for 

populations that winter in the Southwest. Stopover requirements during migration are not well known and 

could be impacted by climate change differently than breeding or wintering habitats.

Management Implications

Fort Huachuca, although adjacent to a wintering area, probably provides only limited foraging habitat; thus, 

management activities are not expected to have much effect on local eagle populations. Availability of roost 

sites may encourage use of particular foraging areas. Forest management such as thinning and prescribed fire 

can enhance or be compatible with maintaining bald eagle roosting sites (DellaSala and others 1998).
USDA Forest Service RMRS-GTR-302. 2013. 77

Habitat:	
  Bald	
  Eagle	
  (Haliaeetus	
  leucocephalus)

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?

Breeds	
  near	
  aquatic	
  habitats	
  adjacent	
  to	
  forests	
  or	
  cliffs	
  

mostly	
  in	
  northern	
  North	
  America	
  (Buehler	
  2000).	
  

Reductions	
  in	
  aquatic	
  and	
  shoreline	
  habitats	
  may	
  be	
  

expected	
  with	
  sea	
  level	
  rise,	
  but	
  individuals	
  in	
  Arizona	
  

are	
  more	
  likely	
  breed	
  in	
  inland	
  in	
  Canada	
  and	
  the	
  Rocky	
  

Mountains	
  where	
  precipitation	
  is	
  expected	
  to	
  increase	
  

(www.climatewizard.com,	
  A2	
  emissions,	
  ensemble	
  GCM).	
  	
  

No	
  change	
  expected	
  for	
  interior	
  aquatic	
  breeding	
  areas.

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?

Winters	
  at	
  rivers,	
  reservoirs,	
  and	
  other	
  aquatic	
  habitats	
  

(Buehler	
  2000).	
  Inland	
  lakes	
  and	
  playas	
  nearby	
  to	
  Fort	
  

Huachuca	
  probably	
  reduced	
  by	
  reduced	
  precipitation	
  and	
  

evaporation	
  during	
  warmer	
  temperatures. 1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Requires	
  large	
  trees	
  for	
  nesting.	
  Breeding	
  grounds	
  for	
  

Arizona	
  individuals	
  are	
  not	
  known,	
  but	
  likely	
  that	
  large	
  

trees	
  will	
  remain	
  available	
  near	
  interior	
  aquatic	
  habitats	
  

in	
  northern	
  locations. 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?	
  

Roost	
  trees	
  are	
  generally	
  large	
  and	
  protected	
  from	
  winds.	
  

These	
  trees	
  may	
  be	
  susceptible	
  to	
  mortality	
  from	
  drought	
  

or	
  shoreline	
  fluctuations.	
  

1

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Factors	
  affecting	
  reproductive	
  success	
  not	
  well	
  known,	
  

but	
  most	
  discussion	
  is	
  related	
  to	
  association	
  with	
  DDT	
  

levels.	
  In	
  an	
  Alaska	
  study,	
  vegetative	
  characteristics	
  of	
  the	
  

habitat	
  were	
  only	
  weakly	
  related	
  to	
  reproductive	
  success	
  

(Hansen	
  1987).

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?

Arizona	
  individuals	
  may	
  move	
  through	
  intermountain	
  

region	
  to	
  breeding	
  areas	
  in	
  the	
  north.	
  

Use	
  transitional	
  habitats,	
  although	
  extent	
  of	
  reliance	
  on	
  

stopover	
  habitats	
  is	
  not	
  well	
  documented. 1
78 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Bald	
  Eagle	
  (Haliaeetus	
  leucocephalus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

No	
  known	
  limitations,	
  although	
  cold	
  limiting	
  conditions	
  

may	
  improve.	
  Cold	
  not	
  likely	
  limiting	
  in	
  Arizona.

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?	
  

Little	
  recorded	
  mortality	
  related	
  to	
  exposure	
  beyond	
  

indirect	
  effects	
  through	
  food	
  supply	
  (Buehler	
  2000).	
  

Reproduction,	
  however,	
  may	
  be	
  reduced	
  during	
  cold,	
  wet	
  

springs	
  (Buehler	
  2000).

Reproduction	
  reduced	
  during	
  cold	
  and	
  wet	
  springs.	
  

Warmer	
  temperatures	
  may	
  reduce	
  losses,	
  but	
  heavy	
  

precipitation	
  events	
  may	
  alone	
  be	
  detrimental	
  and	
  

become	
  more	
  common.	
  Overall,	
  no	
  anticipated	
  change.

0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

None	
  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.

0

Phenology:	
  Bald	
  Eagle	
  (Haliaeetus	
  leucocephalus)

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)?	
  

Leave	
  breeding	
  grounds	
  based	
  on	
  food	
  abundance	
  

(Buehler	
  2000).

0
USDA Forest Service RMRS-GTR-302. 2013. 79

Phenology:	
  Bald	
  Eagle	
  (Haliaeetus	
  leucocephalus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

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?

Migration	
  routes	
  and	
  timing	
  follow	
  salmon	
  runs	
  in	
  some	
  

regions.	
  Prey	
  availability	
  is	
  important.	
  In	
  some	
  

populations	
  peak	
  availability	
  of	
  spawning	
  fish	
  such	
  as	
  

salmon	
  may	
  change,	
  but	
  interior	
  populations,	
  where	
  

salmon	
  are	
  extirpated,	
  are	
  probably	
  most	
  closely	
  linked	
  

to	
  fish	
  populations	
  that	
  fluctuate	
  less.

-­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?

Movement	
  from	
  breeding	
  grounds	
  may	
  be	
  signaled	
  by	
  

declines	
  in	
  food	
  abundance.	
  Already	
  arrive	
  in	
  some	
  areas	
  

to	
  breed	
  while	
  waters	
  are	
  still	
  frozen,	
  but	
  earlier	
  arrival	
  is	
  

advantageous	
  to	
  securing	
  breeding	
  sites	
  (Buehler	
  2000).	
  

Cues	
  are	
  not	
  distant	
  from	
  migration	
  or	
  breeding. 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.

1

Biotic	
  Interactions:	
  Bald	
  Eagle	
  (Haliaeetus	
  leucocephalus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Wide	
  variety	
  of	
  prey	
  items,	
  including	
  birds	
  and	
  mammals,	
  

but	
  prefers	
  fish.	
  Often	
  scavenges	
  or	
  steals	
  prey	
  from	
  other	
  

predators	
  (Buehler	
  2000).	
  Probably	
  eats	
  both	
  warm-­‐	
  and	
  

cold-­‐water	
  fishes	
  in	
  Arizona.	
  No	
  anticipated	
  changes	
  in	
  

overall	
  prey	
  availability	
  in	
  existing	
  lakes.	
  Fish	
  are	
  stocked	
  

at	
  Fort	
  Huachuca	
  all	
  species	
  are	
  non-­‐native.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Predation	
  is	
  not	
  likely	
  a	
  major	
  factor	
  in	
  mortality.

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?	
  

No	
  known	
  diseases	
  that	
  affect	
  populations.	
  Most	
  deaths	
  

are	
  directly	
  or	
  indirectly	
  related	
  to	
  humans	
  (Buehler	
  

2000).

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Competes	
  with	
  other	
  scavengers	
  and	
  raptors,	
  but	
  little	
  

information	
  on	
  these	
  interactions.

Steals	
  prey	
  from	
  other	
  carnivores.	
  No	
  overall	
  change	
  in	
  

competitive	
  outcomes	
  anticipated.

0
80 USDA Forest Service RMRS-GTR-302. 2013.

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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Buehler, David A. 2000. Bald Eagle (Haliaeetus leucocephalus), The Birds of North America Online (A. 

Poole, Ed.). Ithaca: Cornell Lab of Ornithology. Available online from http://bna.birds.cornell.edu.

bnaproxy.birds.cornell.edu/bna/species/506. 

DellaSala, D. A., R. G. Anthony, T. A. Spies, and K. A. Engel. 1998. Management of Bald Eagle communal 

roosts in fire-adapted mixed-conifer forests. Journal of Wildlife Management 62:332–333.

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

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

6:16–17. 

Hansen, A. J. 1987. Regulation of bald eagle reproductive rates in southeast Alaska. Ecology 68:1.

Magrin, G., C. Gay García, D. Cruz Choque, [and others]. 2007: Latin America. Pages 581–615 in Climate 

Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth 

Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. 

Palutikof, P.J. van der Linden and C.E. Hanson, eds., Cambridge University Press, Cambridge, U.K.

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.

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.

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.

Rehfeldt, G.E., N.L. Crookston, M.V. Warwell, J.S. Evans. 2006. Empirical analyses of plant-climate relationships 

for the western United States. International Journal of Plant Sciences 167:1123–1150.

Seager, R., M. Ting, 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.

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

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

role of ecophysiology. Biological Invasions 2:123–140.
USDA Forest Service RMRS-GTR-302. 2013. 81

Northern Goshawk 

(Accipiter gentilis atricipillus)

SUMMARY

Northern goshawks were assessed to be somewhat vulnerable to declines associated with climate change. 

Mature forests with high canopy closure, which are prefered breeding habitats, will be vulnerable to drought 

mortality and fires. Goshawks are fairly flexible in movements, winter habitats, and prey selection, which will 

help to balance negative impacts that are anticipated. Management related to fire severity will be important 

and future changes in breeding timing in this species should be anticipated.

Introduction

The northern goshawk ranges widely in forests across most of North America. Goshawks in southern Arizona 

and Mexico are also sometimes identified as A. g. apache, but there is disagreement over the classification 

of the subspecies (Squires and Reynolds 1997). The Northern goshawk is a Federal species of concern and a 

species of greatest conservation need, Tier 1B, in the Arizona State Wildlife Action Plan or SWAP (AGFD 2006) 

and designated as a species at risk (SWESA 2006). It is also identified as sensitive by the USDA Forest Service.

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

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

section of the main document.

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

-5 0 5 

VULNERABILITY SCORE Uncertainty

Habitat 1.3 14%

Physiology -1.0 33%

Phenology 2.5 25%

Interactions 0.0 40%

Overall 2.4 27%
82 USDA Forest Service RMRS-GTR-302. 2013.

Other Threats and Interactions With Climate

Currently, there is no evidence that goshawk populations are declining in North America (Kennedy 2003). The 

largest current threat is generally considered to be logging of preferred habitats (Kennedy 2003).

Research Needs

Little is known about what level of fire occurrence is important for long-term sustainability of habitats at a 

landscape scale, which will be important in incurring resilience of forests as well as goshawk habitat to climate 

change. Information is also limited on physiological thresholds or timing of resources that affect breeding 

success.

Management Implications

Logging is often considered the greatest threat to this species and does not occur on Fort Huachuca. Fuel 

treatments may have negative impacts, but increasing fuels will be prone to high severity crown fires, which 

will leave habitats unsuitable for long periods. These and other actions related to fire management will be 

important as fire incidence is expected to increase with projected climate change. Additionally, dense stands 

will be more vulnerable to tree mortality during droughts than more open stands. Effective management 

planning for this species therefore needs to balance a number of impacts and benefits at a landscape scale. 

Management for this species often includes restriction of activities during the nesting season. Dates of activity 

restriction may need to be reevaluated as breeding phenology in this species may change.
USDA Forest Service RMRS-GTR-302. 2013. 83

Habitat:	
  Northern	
  Goshawk	
  (Accipiter	
  gentilis	
  atricipillus)

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?

Nests	
  in	
  various	
  mature	
  pine	
  and	
  mixed	
  pine-­‐oak	
  habitats	
  

(Squires	
  and	
  Reynolds	
  1997).	
  Mature	
  forests	
  are	
  

vulnerable	
  to	
  upward	
  elevation	
  shifts	
  and	
  increasing	
  high	
  

severity	
  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,	
  but	
  may	
  use	
  additional	
  non-­‐forested	
  

habitats.	
  Prey	
  abundance	
  may	
  be	
  more	
  important	
  than	
  

habitat	
  for	
  wintering	
  goshawks	
  (Squires	
  and	
  Reynolds	
  

1997).	
  No	
  change	
  in	
  overall	
  area	
  expected	
  for	
  the	
  broader	
  

range	
  of	
  winter	
  habitats.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Requires	
  large	
  trees	
  for	
  nesting	
  and	
  mostly	
  choose	
  

ponderosa	
  pines	
  in	
  the	
  Southwest	
  (Squires	
  and	
  Reynolds	
  

1997).	
  No	
  expected	
  changes	
  for	
  large	
  ponderosa	
  pines	
  

within	
  suitable	
  breeding	
  habitat.	
   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?	
  

In	
  Arizona,	
  choose	
  forests	
  with	
  60%	
  and	
  69%	
  canopy	
  

closure	
  (Squires	
  and	
  Reynolds	
  1997).	
  Association	
  with	
  

closed	
  canopy	
  forests	
  may	
  reduce	
  predation	
  in	
  this	
  

species	
  (Squires	
  and	
  Reynolds	
  1997).	
  Tree	
  mortality	
  

associated	
  with	
  droughts	
  and	
  insect	
  infestations	
  may	
  

decrease	
  canopy	
  closure.

1

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Moderately	
  dense	
  forests	
  may	
  be	
  best	
  foraging	
  habitats	
  

(Squires	
  and	
  Reynolds	
  1997)	
  and	
  may	
  be	
  prone	
  to	
  loss	
  

from	
  increasing	
  fires	
  as	
  well	
  as	
  insect	
  infestations.

1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

High	
  mobility.

-­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	
  required,	
  although	
  seasonal	
  

movements	
  are	
  not	
  well	
  known.

0
84 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Northern	
  Goshawk	
  (Accipiter	
  gentilis	
  atricipillus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Little	
  information,	
  but	
  thresholds	
  not	
  expected	
  to	
  be	
  

exceeded. 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?	
  

Cold	
  and	
  wet	
  conditions	
  result	
  in	
  nest	
  failures	
  although	
  

this	
  is	
  mostly	
  from	
  studies	
  in	
  Europe.	
  Severe	
  rainstorms	
  

may	
  increase	
  but	
  may	
  not	
  co-­‐occur	
  with	
  nesting,	
  which	
  is	
  

early	
  in	
  the	
  year.	
  No	
  anticipated	
  increases	
  in	
  disturbance	
  

mortality

0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Activity	
  is	
  generally	
  linked	
  with	
  prey	
  activity	
  periods	
  

(Squires	
  and	
  Reynolds	
  1997).	
  Although	
  these	
  periods	
  

may	
  change,	
  goshawks	
  appear	
  flexible	
  in	
  activity	
  timing.	
  

No	
  anticipated	
  changes	
  overall. 0

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

At	
  northern	
  latitudes,	
  this	
  species	
  sometimes	
  has	
  

irruptive	
  movements	
  related	
  to	
  resource	
  availability.	
  We	
  

assume	
  a	
  similar	
  flexibility	
  is	
  present	
  in	
  southern	
  

populations	
  and	
  may	
  allow	
  it	
  to	
  cope	
  with	
  fluctuating	
  

resources.

-­1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic.

0

Phenology:	
  Northern	
  Goshawk	
  (Accipiter	
  gentilis	
  atricipillus)

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?	
  

Eggs	
  laid	
  late	
  April	
  to	
  early	
  May	
  with	
  some	
  weather-­‐

associated	
  variability	
  (Squires	
  and	
  Reynolds	
  1997).	
  May	
  

be	
  timed	
  to	
  coincide	
  feeding	
  of	
  young	
  with	
  availability	
  of	
  

young	
  birds	
  and	
  mammals.	
  Phenology	
  of	
  these	
  events	
  is	
  

likely	
  to	
  change. 1
USDA Forest Service RMRS-GTR-302. 2013. 85

Phenology:	
  Northern	
  Goshawk	
  (Accipiter	
  gentilis	
  atricipillus)

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?

Breeding	
  does	
  not	
  occur	
  far	
  in	
  advance	
  or	
  at	
  distant	
  

location	
  from	
  wintering	
  areas.

0

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  brood	
  per	
  season	
  (Squires	
  and	
  Reynolds	
  1997).

1

Biotic	
  Interactions:	
  Northern	
  Goshawk	
  (Accipiter	
  gentilis	
  atricipillus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Opportunistic	
  carnivore.	
  Main	
  food	
  items	
  include	
  birds,	
  

rabbits,	
  and	
  squirrels.	
  Starvation	
  is	
  the	
  most	
  common	
  

cause	
  of	
  mortality	
  (Squires	
  and	
  Reynolds	
  1997).	
  Variety	
  

of	
  prey	
  items,	
  not	
  all	
  expected	
  to	
  decline	
  or	
  increase	
  

simultaneously.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Few	
  predators	
  for	
  adults,	
  but	
  some	
  predation	
  from	
  larger	
  

raptors	
  (Squires	
  and	
  Reynolds	
  1997).	
  No	
  expected	
  

change.

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?	
  

No	
  major	
  diseases	
  known	
  that	
  affect	
  populations.

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

May	
  compete	
  with	
  other	
  predators	
  for	
  food.	
  Will	
  attack	
  

and	
  kill	
  other	
  raptors,	
  including	
  red-­‐tailed	
  hawks.	
  No	
  

important	
  competitive	
  interaction	
  known. 0
86 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

AGFD (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. Web-based version 

available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/species-vulnerability/savs-climate-changetool. 

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

Garfin, G. and M. Lenart. 2007. Climate Change Effects on Southwest Water Resources. Southwest Hydrology 6:16–17. 

Kennedy, P. L. 2003. Northern Goshawk (Accipiter gentilis atricapillus): a technical conservation assessment. USDA Forest 

Service, Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/northerngoshawk.pdf.

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.

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.

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.

Robinett, D. 1994. Fire effects on southeastern Arizona plains grasslands. Rangelands 16:143–148.

Seager, R., M. Ting, 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.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. DoD Legacy 

Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/SWStrategy/FINAL%20SAR%20

REPORT.pdf.

Squires, J. R. and R. T. Reynolds. 1997. Northern Goshawk (Accipiter gentilis), The Birds of North America Online (A. Poole, 

Ed.). Ithaca: Cornell Lab of Ornithology. Available online from http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/

bna/species/298.

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

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

ecophysiology. Biological Invasions 2:123–140.
USDA Forest Service RMRS-GTR-302. 2013. 87

Northern Aplomado Falcon 

(Falco femoralis septentrionalis)

SUMMARY

The aplomado falcon, although not currently present on Fort Huachuca, has potential for future occurrence. 

This falcon could benefit if grasslands increase with a warming climate, but important habitat associates, such 

as woodlands and riparian forests, will be threatened by increased occurrence of high severity wildfires and 

declining water tables. Aspects of the future threats to this species, such as dependence on riparian areas or 

effects of drought, are poorly known and made assessing vulnerability uncertain.

Introduction

The northern aplomado falcon is a Federally endangered species, and although it is not known to occur on 

Fort Huachuca, potential habitat is present (ENRD 2006). Individuals were reintroduced in Texas in the 1990s 

and in New Mexico beginning in 2006. Southwestern populations are considered experimental and nonessential although they may not truly be isolated from wild populations. Aplomado falcon is subject to status 

review as of March 2010 (Federal Register: 75 FR 15454–15456). 

The Peregrine Fund reports more than 40 wild pairs nested in Texas in 2008. Individuals in the United States 

may be part of captive breeding programs but there is also evidence of migration from Mexican populations 

(Keddy-Hector 2000). Any individuals located at Fort Huachuca could be from those released in New Mexico, 

but could also migrate from wild populations in Mexico. Population status and trends are mostly unknown 

because of limited historic information and lack of contemporary population monitoring. 

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• 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 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY SCORE Uncertainty

Habitat -2.6 0%

Physiology 0.8 33%

Phenology 2.5 25%

Interactions 2.0 40%

Overall 1.2 23%
88 USDA Forest Service RMRS-GTR-302. 2013.

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

• CAM plants (succulents, 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

DDT and secondary lead poisoning are thought to be important sources of mortality (Keddy-Hector 1990). 

Populations in the United States are still contaminated with heavy loads of organochlorines, heavy metals, 

and PCBs, which has limited recovery efforts (Keddy-Hector 2000). Extirpation of prairie dogs from much of 

their range may also be a factor in declines (Keddy-Hector 2000). Low reproductive rates that limit expansion 

of populations from Mexico into the United States are thought to be linked to drought. To the extent that 

droughts are limiting to expansion of aplomado falcon, populations in the Fort Huachuca area may decline 

further in the future as droughts become more severe. Encroachment of grasslands by shrubs, often 

associated with overgrazing, has been cited as a cause of habitat losses along with loss due to agriculture and 

water diversions (Keddy-Hector 2000). Although for the purposes of this document we assumed a warmer 

climate would favor grasses over shrubs, season of precipitation, current vegetation, fires, and various other 

factors will interplay to affect the future vegetation trajectory. There is potential, however, that suitable 

grassland habitats will increase in the region. 

Research Needs

Information is needed on pesticide levels and interactions with falcons for various prey items (Keddy-Hector 

2000). This threat may interact with climate as relative prey availability is likely to fluctuate and, thus, 

exposure to these compounds may change. Invasive grasses are increasing in Arizona and may be encouraged 

by climate change, but information on their effect on aplomado falcon habitat is needed. In addition, drought 

and degradation of riparian areas are generally cited as responsible for declines, but the mechanism behind 

this response is unknown and needs to be elucidated to effectively manage this species.

Management Implications

Aplomado falcons are not currently protected under the Endangered Species Act because the origin of 

Arizona individuals is usually considered to be from the experimental population. Fires that accompany higher 

temperatures and more variable rainfall could help increase grasslands, thus increasing habitat for the falcon. 

An increasing proportion of these grasslands may be made up of non-native species, but this has an unknown 

effect on falcon populations. Use of prescribed fire is likely compatible with habitat preservation especially 

if intensities are low enough to not burn nesting substrates. A number of identified vulnerabilities were 

related to timing and quantity of prey. Management is unlikely to affect timing of peak prey availability, but 

protection of a variety of prey sources may help increase resilience. Larger areas of suitable habitat potentially 

could help this species survive drought conditions or variable prey populations. If falcons are present on Fort 

Huachuca then management measures such as timing of military activities and protection of stick nests may 

be necessary. These measures, if implemented, also need to anticipate phenological change in response to a 

warming climate.
USDA Forest Service RMRS-GTR-302. 2013. 89

Habitat:	
  Northern	
  Aplomado	
  Falcon (Falco	
  femoralis	
  septentrionalis)

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	
  aplomado	
  falcon	
  inhabits	
  various	
  desert	
  grasslands	
  

and	
  coastal	
  prairies	
  in	
  the	
  United	
  States-­‐Mexico	
  border	
  

region,	
  the	
  Gulf	
  Coast	
  of	
  Mexico,	
  and	
  parts	
  of	
  Central	
  

America.	
  Suitable	
  grassland	
  habitats	
  often	
  are	
  associated	
  

with	
  scattered	
  trees	
  and	
  shrubs	
  or	
  edges	
  of	
  riparian	
  

woodlands	
  (Keddy-­‐Hector	
  2000).	
  In	
  the	
  United	
  States,	
  

associated	
  with	
  scattered	
  mesquite	
  and	
  yuccas	
  (Keddy-­‐

Hector	
  1990).	
  Grassland	
  habitats	
  may	
  benefit	
  from	
  more	
  

frequent	
  fires	
  and	
  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?

Same	
  as	
  above.

-­1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  the	
  

associated	
  vegetation	
  

type?	
  

Nests	
  are	
  in	
  stick	
  platforms	
  built	
  in	
  trees	
  or	
  other	
  

structures	
  by	
  other	
  raptors	
  or	
  corvids.	
  They	
  are	
  also	
  

known	
  to	
  use	
  nests	
  in	
  cliffs	
  or	
  on	
  power	
  lines	
  (Keddy-­‐

Hector	
  2000).	
  Yuccas	
  are	
  often	
  used	
  for	
  nesting	
  in	
  the	
  

United	
  States	
  (Peregrine	
  Fund	
  website).	
  High	
  severity	
  

fires	
  may	
  threaten	
  plants	
  with	
  suitable	
  structures	
  for	
  nest	
  

platforms	
  such	
  as	
  yuccas	
  or	
  trees.

1

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  survival	
  during	
  

non-­‐breeding	
  periods	
  

expected	
  to	
  change	
  

within	
  the	
  associated	
  

vegetation	
  type?

None.

0

5.	
  Habitat	
  

quality	
  and	
  

reproduction

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Generally	
  associated	
  with	
  more	
  open	
  habitats,	
  which	
  are	
  

probably	
  improves	
  success	
  for	
  hunting	
  of	
  ground	
  feeding	
  

birds.	
  Increasing	
  droughts	
  and	
  fires	
  may	
  open	
  habitats.

-­1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  this	
  species’	
  

capacity	
  and	
  tendency	
  

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?

No	
  transitional	
  habitats	
  required.

0
90 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Northern	
  Aplomado	
  Falcon (Falco	
  femoralis	
  septentrionalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

U.S.	
  populations	
  are	
  at	
  the	
  northern	
  limit	
  of	
  current	
  range	
  

and	
  former	
  range	
  is	
  not	
  well	
  known	
  (Keddy-­‐Hector	
  

2000).	
  Occupies	
  various	
  habitats,	
  including	
  deserts.	
  No	
  

physiological	
  limitations	
  known.

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?	
  

None	
  known.

0

4.	
  Limitations	
  

to	
  active	
  period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Adults	
  are	
  most	
  active	
  at	
  dawn	
  and	
  dusk,	
  and	
  may	
  hunt	
  

well	
  before	
  or	
  after	
  dark	
  (Keddy-­‐Hector	
  2000).	
  Hunting	
  

activity	
  does	
  not	
  seem	
  to	
  be	
  strictly	
  limited	
  to	
  this	
  period.	
  

Spends	
  much	
  of	
  the	
  day	
  perched. 0

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

No.	
  Cache	
  prey	
  items	
  and	
  retrieve	
  them	
  to	
  feed	
  to	
  

nestlings	
  (Keddy-­‐Hector	
  2000).	
  Food	
  caching	
  behavior	
  is	
  

likely	
  limited	
  to	
  feeding	
  of	
  young. 1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Endothermic,	
  moderate.

0

Phenology:	
  Northern	
  Aplomado	
  Falcon (Falco	
  femoralis	
  septentrionalis)

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	
  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?	
  

In	
  the	
  United	
  States,	
  most	
  aplomado	
  falcons	
  lay	
  eggs	
  in	
  

April-­‐May,	
  but	
  in	
  eastern	
  Mexico, they	
  lay	
  eggs	
  in	
  January-­‐

June	
  during	
  the	
  dry	
  season	
  (Keddy-­‐Hector	
  1990).	
  Nesting	
  

may	
  be	
  timed	
  to	
  occur	
  just	
  before	
  nesting	
  of	
  resident	
  

birds	
  and	
  arrival	
  of	
  spring	
  migrants	
  (Keddy-­‐Hector	
  

2000).	
  Timing	
  of	
  breeding	
  to	
  fledgling	
  of	
  other	
  bird	
  

species	
  and	
  spring	
  emergence	
  of	
  insects	
  is	
  likely	
  

important.	
  Both	
  these	
  events	
  may	
  vary	
  with	
  changes	
  in	
  

temperature.

1
USDA Forest Service RMRS-GTR-302. 2013. 91

Phenology:	
  Northern	
  Aplomado	
  Falcon (Falco	
  femoralis	
  septentrionalis)

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?

Cues	
  to	
  initiate	
  breeding	
  are	
  not	
  known	
  but	
  species	
  is	
  

resident,	
  so	
  not	
  distant	
  from	
  breeding	
  grounds.

0

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Second	
  broods	
  are	
  possible,	
  but	
  not	
  documented	
  (Keddy-­‐

Hector	
  2000).	
  

1

Biotic	
  Interactions:	
  Northern	
  Aplomado	
  Falcon (Falco	
  femoralis	
  

septentrionalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Eats	
  mostly	
  small	
  birds	
  and	
  insects	
  (Keddy-­‐Hector	
  2000).	
  

Dominant	
  bird	
  prey	
  are	
  those	
  that	
  feed	
  on	
  the	
  ground	
  or	
  

in	
  short	
  direct	
  flights.	
  These	
  species	
  include	
  grackles,	
  

doves,	
  nighthawks,	
  and	
  meadowlarks	
  (Keddy-­‐Hector	
  

1990).	
  They	
  also	
  steal	
  kills	
  from	
  other	
  avian	
  predators	
  

(Keddy-­‐Hector	
  2000).	
  Diet	
  is	
  various,	
  but	
  birds	
  likely	
  

make	
  up	
  most	
  of	
  the	
  biomass	
  consumed.	
  Loss	
  of	
  riparian	
  

woodlands	
  is	
  thought	
  to	
  have	
  contributed	
  to	
  declines	
  

because	
  of	
  reductions	
  in	
  available	
  avian	
  prey	
  (Keddy-­‐

Hector	
  1990).	
  Further	
  loss	
  of	
  riparian	
  areas	
  and	
  

dependent	
  bird	
  populations	
  with	
  climate	
  change	
  may	
  

reduce	
  avian	
  prey.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Predators	
  of	
  nests	
  are	
  likely	
  various	
  and	
  larger	
  raptors	
  

may	
  prey	
  on	
  adults	
  (Keddy-­‐Hector	
  2000).	
  Predation	
  was	
  

a	
  major	
  cause	
  of	
  death	
  of	
  released	
  birds	
  in	
  Texas	
  (Keddy-­‐

Hector	
  2000),	
  but	
  susceptibility	
  of	
  captive-­‐raised	
  falcons	
  

may	
  differ	
  from	
  wild-­‐born.	
  No	
  important	
  predators	
  

known.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

Generally	
  dependent	
  on	
  other	
  birds	
  to	
  build	
  large	
  

platform	
  nests	
  (Keddy-­‐Hector	
  2000).	
  These	
  include	
  nests	
  

of	
  various	
  species	
  including	
  ravens	
  and	
  red-­‐tailed	
  hawks.	
  

Both	
  these	
  species	
  are	
  widespread	
  and	
  tolerant	
  of	
  human	
  

activities,	
  thus	
  perhaps	
  tolerant	
  of	
  changing	
  climate.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  in	
  

this	
  species	
  expected	
  

to	
  change?	
  

Prone	
  to	
  trichomoniasis	
  transmitted	
  by	
  dove	
  populations.	
  

There	
  is	
  some	
  potential	
  for	
  greater	
  transmission	
  as	
  doves	
  

concentrate	
  at	
  fewer	
  water	
  sources	
  and	
  with	
  increasing	
  

urban	
  development. 1
92 USDA Forest Service RMRS-GTR-302. 2013.

Biotic	
  Interactions:	
  Northern	
  Aplomado	
  Falcon (Falco	
  femoralis	
  

septentrionalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

May	
  compete	
  for	
  stick	
  nests,	
  but	
  no	
  information	
  on	
  this	
  

potential	
  issue.	
  Also	
  steals	
  prey	
  from	
  other	
  raptors	
  so	
  

apparently	
  a	
  strong	
  competitor. 0
USDA Forest Service RMRS-GTR-302. 2013. 93

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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

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

6:16–17.

Keddy-Hector, D. P. 2000. Aplomado Falcon (Falco femoralis), The Birds of North America Online (A. Poole, 

Ed.). Ithaca: Cornell Lab of Ornithology. Available online from http://bna.birds.cornell.edu.bnaproxy.birds.

cornell.edu/bna/species/549.

Keddy-Hector, D. P. 1990. Northern Aplomado Falcon Recovery Plan. USFWS Region 2, Albuquerque, 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.

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.

Seager,R., M. Ting, 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.

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

Ecology 65:643–651. 

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

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

role of ecophysiology. Biological Invasions 2:123–140.
94 USDA Forest Service RMRS-GTR-302. 2013.

American Peregrine Falcon

(Falco peregrinus anatum)

SUMMARY

Peregrine falcons are flexible in 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 if different aspects 

of timing relationships shift in synchrony or become mismatched. Although Arizona habitats are expected to 

remain suitable, peregrine falcons will be exposed to other climate change effects at wintering and stopover 

sites. Restriction of activities at nesting sites needs to adjust for future timing changes.

Introduction

Peregrine falcons have nested on Fort Huachuca in recent years (at least one pair), and there are other 

breeding territories in nearby surroundings (ENRD 2006). The species was Federally listed in 1970 and delisted 

in 1999. Peregrine falcons are a species of greatest conservation need, Tier 1B, in Arizona State Wildlife Action 

Plan or SWAP (AGFD 2006) and are designated as a species at risk (SWESA 2006).

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• Decreased annual rainfall in Central America (Magrin and others 2007)

• Conversion of tropical forest to savannah in northern South America (Magrin and others 2007)

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

section of the main document.

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

-5 0 5 

VULNERABILITY Score Uncertainty

Habitat -0.1 0%

Physiology 0.8 33%

Phenology 2.5 25%

Interactions 1.0 40%

Overall 3.5 23%
USDA Forest Service RMRS-GTR-302. 2013. 95

Other Threats and Interactions With Climate

Population declines in the past are thought to be primarily due to DDT and populations are currently 

recovering. Because this species is migratory, climate or land use changes in Mexico and Central America will 

affect populations at Fort Huachuca.

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. In addition, physiological thresholds as they relate to 

increasing temperatures in hot portions of their 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), which is 

probably relatively low in this region. Thus, it is unlikely that local 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. Restriction of activities at suitable nesting sites is important and managers should plan for shifts in 

breeding timing.
96 USDA Forest Service RMRS-GTR-302. 2013.

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	
  Fort	
  Huachuca	
  is	
  suitable	
  vegetation	
  and	
  should	
  

continue	
  to	
  remain	
  suitable	
  despite	
  proportional	
  changes	
  

in	
  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
USDA Forest Service RMRS-GTR-302. 2013. 97

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?

Limited	
  information.	
  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.

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,	
  and	
  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	
  directly	
  in	
  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
98 USDA Forest Service RMRS-GTR-302. 2013.

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	
  directly	
  in	
  

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	
  items	
  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	
  benefit	
  from	
  

developed	
  areas	
  of	
  the	
  Fort.	
  No	
  expected	
  overall	
  changes	
  

in	
  prey	
  available.

0

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).	
  May	
  increase	
  with	
  increased	
  

transmission	
  in	
  doves	
  from	
  crowding	
  at	
  artificial	
  feeders	
  

or	
  shrinking	
  water	
  sources. 1

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

No	
  major	
  competitors	
  known.

0
USDA Forest Service RMRS-GTR-302. 2013. 99

Literature Cited

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

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. Global Environmental 

Change 1:351–364. 

Magrin, G., C. Gay García, D. Cruz Choque, [and others]. 2007. Latin America. Pages 581–615 in Climate 

Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth 

Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. 

Palutikof, P.J. van der Linden and C.E. Hanson, eds. Cambridge University Press, Cambridge, U.K.

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.

Seager, R., M. Ting, 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.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

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

White, C. M., N. J. Clum, T. J. Cade and W. G. Hunt. 2002. Peregrine Falcon (Falco peregrinus), The Birds of 

North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology.
100 USDA Forest Service RMRS-GTR-302. 2013.

Western Yellow-billed Cuckoo 

(Coccyzus americanus occidentalis)

SUMMARY

Western yellow-billed cuckoos have small, fragmented populations and are likely to be subject to greater 

stress with projected climate change. Riparian habitats, which yellow-billed cuckoos rely on, have already 

greatly declined and are expected to be exposed to further degradation and loss. Physiological aspects as well 

as timing and reproduction were both identified as vulnerable areas for this species. Of potential benefit, periodical cicadas are an important food resource in some years and will likely be tolerant of projected changes. 

Facultative brood parasitism has the potential to increase populations during periods of high resource levels, 

but very little incidence of this behavior has been recorded. Overall, many life history aspects are poorly studied in this species, thus vulnerability prediction is relatively uncertain. 

Introduction

Historically, yellow-billed cuckoos bred throughout the United States but have now declined and, in the West, 

only occur in fragmented populations. The western population of the yellow-billed cuckoo is considered 

distinct from eastern populations and has been a candidate for Federal listing by the USFWS since 2001. 

Although there has been some disagreement over whether the there are valid eastern and western subspecies, USFWS (2001), citing Franzreb and Laymon (1993), recognized the western subspecies (C. a. 

occidentalis). Sufficient evidence was obtained for listing, but it was precluded by other higher priority listing 

actions (66 Federal Register 38611). It is also identified as a species of greatest conservation need, Tier 1A, in 

the Arizona State Wildlife Action Plan or SWAP (AGFD 2006) and a species at risk (SWESA 2006). Yellow-billed 

cuckoos occur at Fort Huachuca, although much larger numbers are present nearby on the San Pedro River. 

Primary riparian areas on the Fort are in Garden, Huachuca, and McClure Canyons (ENRD 2006).

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

-5 0 5 

VULNERABILITY Score Uncertainty

Habitat 1.3 43%

Physiology 2.5 50%

Phenology 3.8 50%

Interactions -1.0 40%

Overall 6.1 45%
USDA Forest Service RMRS-GTR-302. 2013. 101

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• Decreased annual rainfall in Central America (Magrin and others 2007)

• Conversion of tropical forest to savannah in northern South America (Magrin and others 2007)

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

In arid regions, yellow-billed cuckoos occur in riparian habitats. Continued loss and degradation of riparian 

habitats is a major concern, including invasion by salt cedar (Tamarix spp.). Without considering climate, water 

tables are likely to be lower on the Upper San Pedro even with conservation measures (Steinitz and others 

2005). Comparisons of salt cedar dominated versus cottonwood-willow-dominated habitats on the San Pedro 

indicate that surface flow permanence was the most important determinant of plant species dominance (Lite 

and Stromberg 2005); thus, with warmer temperatures and continued water table withdrawals (Stromberg 

and others 1996), we may expect greater dominance of salt cedar on the San Pedro River. Fires are also a 

concern in riparian habitats as cottonwoods are prone to fire mortality, but regrowth of shrubs following fire 

may attract cuckoos. Western populations are very small and fragmented, so they are more vulnerable to 

stochastic events, including those related to extreme climate events.

Water diversion will likely increase with hotter and drier conditions placing more stress on riparian systems. 

Pesticides have been implicated in mortality and population declines (Hughes 1999). The migratory habits of 

this species make coordinated conservation efforts that span the entire species’ range difficult. Also, many 

deaths due to collisions have been reported, which may be an issue if wind farm developments within the 

species’ range increase to create more sustainable forms of energy.

Historically, yellow-billed cuckoos nested in a wider range of habitats than today, including non-riparian 

habitats. One possible explanation for this pattern is that exposure to pesticides has increased moisture loss 

in eggs causing reduced hatchability and making drier habitats unsuitable (Laymon and Halterman 1987). 

Pesticide restrictions in the United States are limited in their protection for neotropical migrants. Hotter and 

drier conditions will exacerbate egg drying and restrict cuckoos further to moist riparian areas.

Research Needs

The effect of pesticides and interaction with increasing temperatures are potentially of importance with 

warming climate but have not been studied. More information is also needed on the role of brood parasitism 

(both intra- and inter- specific) in population dynamics. Effects of pesticides on egg hatching and interactions 

with a drier climate need more study and consideration.

Management Implications

Fort Huachuca has a wetlands management program specifically to protect wetland resources including 

riparian habitats (ENRD 2006). Fort Huachuca has implemented water conservation to reduce ground water 

pumping, which may help protect riparian habitats for yellow-billed cuckoo on Fort Huachuca, although the 

relation of ground water to San Pedro surface flows is unresolved (ENRD 2006). At the Fort, ground water 

levels are monitored (ENRD 2006). Some upland land manipulations can also increase surface flows, but these 

effects are usually temporary. Because cuckoos are restricted to riparian areas, military exercises probably 

have little direct impact on this species. Indirect negative impacts of military activities such as increases 

in ignition sources, invasive species spread, and water withdrawals should be limited when possible. Fire 

management and invasive species control will be important to preserve riparian forests.
102 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Western	
  Yellow-­billed	
  Cuckoo	
  (Coccyzus	
  americanus	
  occidentalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Area	
  and	
  

distribution:

breeding

Is	
  the	
  area	
  or	
  location	
  

of	
  the	
  associated	
  

vegetation	
  type	
  used	
  

for	
  breeding	
  activities	
  

by	
  this	
  species	
  

expected	
  to	
  change?

Yellow-­‐billed	
  cuckoos	
  prefer	
  open	
  woodlands	
  with	
  low,	
  

dense	
  shrubby	
  vegetation	
  at	
  elevations	
  up	
  to	
  1500 m	
  

(Hughes	
  1999).	
  	
  Proximity	
  to	
  water	
  appears	
  important,	
  

either	
  directly	
  or	
  indirectly,	
  in	
  all	
  preferred	
  habitats.	
  The	
  

majority	
  of	
  nests	
  were	
  found	
  by	
  Arizona	
  Breeding	
  Bird	
  

Atlas	
  (Corman	
  and	
  Wise-­‐Gervais	
  2005)	
  along	
  perennial	
  

drainages.	
  In	
  Arizona, the	
  species	
  prefers	
  desert	
  riparian	
  

forests	
  of	
  the	
  Sonoran	
  Zone,	
  comprised	
  of	
  willow,	
  

Fremont	
  cottonwood,	
  and	
  dense	
  mesquite	
  (Hughes	
  

1999).	
  For	
  2-­‐3	
  weeks	
  before	
  breeding,	
  they	
  may	
  occupy	
  

upland	
  vegetation,	
  including	
  pinyon,	
  oak,	
  juniper,	
  and	
  

manzanita	
  (Hughes	
  1999).	
  Associated	
  with	
  riparian	
  

habitats	
  with	
  willow	
  and	
  cottonwood,	
  which	
  are	
  expected	
  

to	
  decrease	
  with	
  reduced	
  stream	
  flows,	
  lower	
  water	
  

tables,	
  higher	
  temperatures,	
  and	
  changing	
  flood	
  regimes.	
  

Higher	
  temperatures	
  are	
  also	
  associated	
  with	
  an	
  increase	
  

in	
  fire,	
  which	
  generally	
  kills	
  cottonwoods,	
  although	
  there	
  

would	
  be	
  some	
  benefit	
  in	
  increasing	
  shrubby	
  habitats	
  if	
  

fire	
  area	
  is	
  not	
  too	
  extensive.

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?

It	
  is	
  thought	
  that	
  this	
  subspecies	
  winters	
  primarily	
  in	
  

northwest	
  South	
  America	
  (Hughes	
  1999).	
  Overall,	
  

wintering	
  birds	
  occupy	
  a	
  wide	
  variety	
  of	
  forests,	
  

woodlands,	
  and	
  scrubby	
  areas,	
  preferring	
  “woody	
  

vegetation	
  bordering	
  fresh	
  water	
  (Rappole	
  and	
  others

1983	
  and	
  Stotz	
  and	
  others	
  1996	
  in	
  Hughes	
  1999).	
  	
  Winter	
  

habitat	
  is	
  reported	
  as	
  mangroves	
  and	
  riparian	
  habitats	
  in	
  

Surinam	
  and	
  Guyana	
  (Tostain	
  and	
  others	
  1992,	
  

Haverschmidt	
  and	
  Mees	
  1994	
  in	
  Hughes	
  1999).	
  In	
  

Venezuela,	
  they	
  have	
  been	
  observed	
  in	
  open	
  woodlands,	
  

second	
  growth,	
  and	
  thickets	
  (Meyer	
  de	
  Schauensee	
  and	
  

Phelps	
  1978	
  in	
  Hughes	
  1999).

Not	
  well	
  known,	
  but	
  seem	
  to	
  be	
  associated	
  with	
  a	
  number	
  

of	
  scrub	
  and	
  woodland	
  habitats	
  in	
  South	
  America.	
  	
  In	
  

some	
  regions,	
  savannahs	
  are	
  expected	
  to	
  replace	
  tropical	
  

forest,	
  which	
  may	
  increase	
  wintering	
  habitats,	
  but	
  also	
  

associated	
  with	
  mangroves,	
  which	
  are	
  vulnerable	
  to	
  sea	
  

level	
  rise.	
  	
  Overall,	
  no	
  predicted	
  change	
  in	
  winter	
  habitat	
  

area.

0

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?

Cottonwoods	
  are	
  used	
  extensively	
  for	
  foraging,	
  and	
  nests	
  

are	
  often	
  placed	
  in	
  willows.	
  In	
  western	
  United	
  States,	
  

nests	
  in	
  Fremont	
  cottonwood,	
  mesquite,	
  hackberry,	
  

soapberry,	
  alder,	
  and	
  cultivated	
  fruit	
  trees,	
  but	
  trees	
  need	
  

to	
  be	
  large	
  enough	
  with	
  horizontal	
  branches	
  for	
  support	
  

(Laymon	
  1980	
  in	
  Hughes	
  1999).	
  Lowering	
  of	
  water	
  tables	
  

and	
  increases	
  in	
  fires	
  are	
  likely	
  to	
  reduce	
  trees	
  large	
  

enough	
  to	
  support	
  nests.

1
USDA Forest Service RMRS-GTR-302. 2013. 103

Habitat:	
  Western	
  Yellow-­billed	
  Cuckoo	
  (Coccyzus	
  americanus	
  occidentalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

4.	
  Habitat	
  

components:	
  

non-­breeding

Are	
  other	
  specific	
  

habitat	
  components	
  

required	
  for	
  survival	
  

during	
  non-­‐breeding	
  

periods	
  expected	
  to	
  

change	
  within	
  

associated	
  vegetation	
  

type?

No	
  information.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?

Cuckoos	
  typically	
  select	
  nest	
  sites	
  with	
  very	
  dense	
  cover,	
  

particularly	
  overhead.	
  Although	
  there	
  may	
  be	
  a	
  

relationship,	
  it	
  is	
  not	
  known	
  if	
  this	
  is	
  associated	
  with	
  

reproductive	
  success,	
  but	
  not	
  expected	
  to	
  change	
  within	
  

suitable	
  habitat.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Both	
  sexes	
  are	
  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?

Long-­‐distance	
  migrant	
  through	
  Mexico	
  and	
  Central	
  

America.	
  In	
  addition,	
  for	
  2-­‐3	
  weeks	
  before	
  breeding,	
  they	
  

may	
  occupy	
  upland	
  vegetation	
  including	
  pinyon,	
  oak,	
  

juniper,	
  and	
  manzanita. 1

Physiology:	
  Western	
  Yellow-­billed	
  Cuckoo	
  (Coccyzus	
  americanus	
  

occidentalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Southern	
  Arizona	
  is	
  in	
  the	
  southeastern	
  portion	
  of	
  the	
  

sub-­‐species	
  range	
  in	
  the	
  United	
  States.	
  Western	
  

populations	
  are	
  very	
  local	
  in	
  scattered	
  riparian	
  areas	
  

from	
  Montana	
  to	
  Mexico.	
  	
  	
  The	
  species	
  formerly	
  bred	
  

throughout	
  most	
  of	
  North	
  American	
  from	
  southern	
  

Canada	
  to	
  northern	
  Mexico	
  (USFWS	
  2001).	
  This	
  

subspecies	
  breeds	
  in	
  riparian	
  areas	
  in	
  western	
  	
  United	
  

States,	
  which	
  provide	
  shade	
  and	
  a	
  relatively	
  cooler	
  

microclimate.	
  Incubating	
  adults	
  and	
  nestlings	
  have	
  been	
  

observed	
  panting	
  on	
  hot	
  days	
  (Hughes	
  1999).	
  Some	
  have	
  

proposed	
  that	
  pesticide	
  use	
  has	
  made	
  eggs	
  prone	
  to	
  

detrimental	
  effects	
  of	
  drying	
  (Laymon	
  and	
  Halterman	
  

1987),	
  but	
  no	
  experimental	
  data	
  are	
  available.

Very	
  little	
  known.	
  Restricted	
  to	
  riparian	
  areas	
  in	
  hot	
  

regions,	
  which	
  are	
  cooler	
  and	
  more	
  humid	
  than	
  

surroundings.	
  Taken	
  together,	
  these	
  facts	
  may	
  indicate	
  a	
  

relative	
  intolerance	
  to	
  hot	
  dry	
  conditions,	
  which	
  are	
  

expected	
  to	
  increase	
  on	
  the	
  breeding	
  grounds.

1
104 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Western	
  Yellow-­billed	
  Cuckoo	
  (Coccyzus	
  americanus	
  

occidentalis)

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?	
  

Veit	
  and	
  Petersen	
  (1993,	
  in	
  Hughes	
  1999)	
  reported	
  that	
  

in	
  1954,	
  many	
  weakened	
  and	
  starving	
  yellow-­‐billed	
  

cuckoos	
  were	
  observed	
  in	
  northeastern	
  states	
  following	
  

the	
  passage	
  of	
  3	
  hurricanes.	
  Hurricane	
  intensity	
  is	
  

expected	
  to	
  increase	
  under	
  global	
  climate	
  change,	
  but	
  

hurricane	
  frequency predictions,	
  which	
  are	
  more	
  likely	
  to	
  

increase	
  mortality, are	
  inconsistent	
  (Emanuel	
  2005).	
  

Populations	
  migrating	
  to	
  Arizona	
  likely	
  remain	
  inland	
  

where	
  they	
  are	
  more	
  protected	
  from	
  hurricanes	
  than	
  

those	
  crossing	
  the	
  Gulf	
  of	
  Mexico.

Several	
  intense	
  rainfall	
  events	
  have	
  been	
  reported	
  for	
  

Venezuela,	
  which	
  may	
  also	
  result	
  in	
  mortality.	
  These	
  

occurred	
  in	
  September	
  (Columbia)	
  and	
  February	
  

(Venezuela),	
  and	
  thus	
  may	
  coincide	
  with	
  yellow-­‐billed	
  

cuckoo	
  presence.	
  May	
  be	
  increased	
  mortality	
  with	
  

increased	
  exposure	
  to	
  hurricanes,	
  but	
  exposure	
  is	
  

probably	
  not	
  high	
  for	
  western	
  populations.	
  More	
  intense	
  

rain	
  storms	
  are	
  also	
  predicted	
  for	
  South	
  America,	
  which	
  

may	
  increase	
  mortality	
  for	
  some	
  species,	
  although	
  effect	
  

on	
  cuckoos	
  is	
  largely	
  unknown

1

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

The	
  western	
  subspecies	
  breeds	
  in	
  riparian	
  areas,	
  which	
  

provide	
  shade,	
  thus	
  escaping	
  highest	
  temperatures.	
  No	
  

other	
  information	
  on	
  activity	
  in	
  relation	
  to	
  climate	
  

variables. 0

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Brood	
  parasitism	
  is	
  facultative	
  in	
  this	
  species.	
  Rates	
  of	
  

brood	
  parasitism	
  and	
  consequences	
  for	
  reproductive	
  

success	
  are	
  not	
  known.	
  There	
  is	
  some	
  suggestion	
  that	
  

periods	
  of	
  high	
  resource	
  availability	
  during	
  breeding	
  such	
  

as	
  emergence	
  of	
  cicadas	
  may	
  allow	
  for	
  larger	
  clutches	
  and	
  

increased	
  intraspecific	
  brood	
  parasitism	
  (Fleischer	
  and	
  

others 1985).	
  Resource	
  availability	
  might	
  then	
  also	
  be	
  

expected	
  to	
  be	
  related	
  to	
  interspecific	
  brood	
  parasitism	
  

as	
  well.	
  

Has	
  both	
  inter-­‐	
  and	
  intra-­‐specific	
  brood	
  parasitism.	
  May	
  

be	
  able	
  to	
  lay	
  larger	
  clutches	
  and	
  lay	
  extra	
  eggs	
  in	
  nests	
  of	
  

other	
  individuals.	
  This	
  behavior	
  has	
  the	
  potential	
  to	
  

increase	
  breeding	
  success	
  during	
  years	
  of	
  high	
  resource	
  

levels.	
  Increased	
  breeding	
  opportunities	
  through	
  brood	
  

parasitism	
  may	
  be	
  expected	
  to	
  increase	
  populations	
  

during	
  high	
  resource	
  years,	
  but	
  no	
  effect	
  of	
  this	
  behavior	
  

on	
  populations	
  has	
  yet	
  been	
  documented.	
  Rates	
  of	
  brood	
  

parasitism	
  are	
  also	
  not	
  well	
  known,	
  but	
  currently	
  there	
  

are	
  few	
  records	
  of	
  occurrence,	
  which	
  may	
  indicate	
  this	
  

behavior	
  is	
  too	
  rare	
  to	
  affect	
  populations.

1
USDA Forest Service RMRS-GTR-302. 2013. 105

Physiology:	
  Western	
  Yellow-­billed	
  Cuckoo	
  (Coccyzus	
  americanus	
  

occidentalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic.

0

Phenology:	
  Western	
  Yellow-­billed	
  Cuckoo	
  (Coccyzus	
  americanus	
  

occidentalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Cues Does	
  this	
  species	
  use	
  

temperature	
  or	
  

moisture	
  cues	
  to	
  

initiate	
  activities	
  

related	
  to	
  fecundity	
  or	
  

survival	
  (e.g.,	
  

hibernation,	
  

migration,	
  breeding)?	
  

No	
  information.	
  Assume	
  combination	
  of	
  external	
  and	
  

internal	
  signals	
  for	
  migration	
  and	
  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?	
  

Breeding	
  initiation	
  often	
  coincides	
  with	
  rainfall	
  and	
  is	
  

thought	
  to	
  be	
  related	
  to	
  food	
  availability	
  (Nolan	
  and	
  

Thompson	
  1975	
  in	
  Hughes	
  1995).	
  In	
  the	
  West,	
  yellow-­‐

billed	
  cuckoos	
  arrive	
  relatively	
  late	
  in	
  spring	
  (mid	
  May)	
  

compared	
  to	
  the	
  eastern	
  subspecies	
  or	
  many	
  other	
  

migratory	
  birds	
  (Hughes	
  1999).	
  Viet	
  and	
  Petersen	
  (1993)	
  

reported	
  that	
  birds	
  may	
  not	
  breed	
  in	
  years	
  when	
  food	
  

supply	
  is	
  low,	
  and	
  these	
  periods	
  may	
  increase	
  as	
  droughts	
  

become	
  more	
  frequent.	
  Breeding initiation may	
  be	
  

correlated	
  with	
  abundance	
  of	
  local	
  food	
  or	
  periods	
  of	
  

greatest	
  precipitation.	
  Changes	
  in	
  precipitation	
  and	
  

temperature	
  may	
  alter	
  timing	
  of	
  insect	
  emergence.

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?

Migration	
  and	
  breeding	
  separated	
  by	
  large	
  temporal	
  and	
  

spatial	
  gap.

1

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Populations	
  in	
  the	
  western	
  United	
  States are	
  believed	
  to	
  

raise	
  only	
  one	
  brood	
  per	
  season	
  and	
  breeding	
  season	
  is	
  

shorter	
  than	
  in	
  the	
  eastern	
  United	
  States	
  (Hughes	
  1999).	
  

Recent	
  information	
  indicated	
  that	
  yellow-­‐billed	
  cuckoos	
  

may	
  breed	
  a	
  second	
  time	
  in	
  western	
  Mexico	
  after	
  

migrating	
  from	
  the	
  north	
  (Rohwer	
  and	
  others	
  2009),	
  

which	
  may	
  allow	
  this	
  species	
  take	
  advantage	
  of	
  seasonal	
  

resources	
  in	
  multiple	
  locations.	
  Because	
  very	
  little	
  is	
  

known	
  about	
  this	
  second	
  breeding,	
  we	
  assume	
  only	
  one	
  

brood	
  per	
  year.

1
106 USDA Forest Service RMRS-GTR-302. 2013.

Biotic	
  Interactions:	
  Western	
  Yellow-­billed	
  Cuckoo	
  (Coccyzus	
  americanus	
  

occidentalis)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Cuckoos	
  feed	
  primarily	
  on	
  large	
  insects	
  such	
  as	
  

caterpillars,	
  grasshoppers,	
  crickets,	
  katydids,	
  cicadas,	
  and	
  

sometimes	
  on	
  small	
  lizards,	
  frogs,	
  eggs,	
  and	
  nestlings	
  

(Hughes	
  1999).	
  	
  Cuckoos	
  on	
  wintering	
  grounds	
  also	
  feed	
  

on	
  fruits	
  and	
  seeds	
  in	
  addition	
  to	
  insects	
  (Hughes	
  1999).	
  

Populations	
  fluctuate	
  greatly	
  with	
  food	
  availability	
  and	
  

can	
  increase	
  dramatically	
  in	
  years	
  of	
  highest	
  insect	
  

abundance	
  such	
  as	
  tent	
  caterpillar	
  infestations	
  and	
  cicada	
  

cycles	
  (Hughes	
  1999).	
  Cicadas	
  are	
  behaviorally	
  and	
  

physiologically	
  tolerant	
  of	
  high	
  temperatures	
  (Heath	
  and	
  

Wilkin	
  1970).	
  In	
  addition,	
  cuckoos	
  have	
  high	
  

reproduction	
  in	
  salt	
  cedar	
  (Glinski	
  and	
  Ohmart	
  1984)	
  

and,	
  thus,	
  may	
  be	
  expected	
  to	
  be	
  resilient	
  to	
  projected	
  

climate	
  changes	
  in	
  the	
  breeding	
  range.

-­1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Raptors	
  may	
  be	
  an	
  important	
  predator	
  during	
  migration	
  

and	
  upon	
  arrival	
  on	
  wintering	
  grounds	
  (Hector	
  1985	
  in	
  

Hughes	
  1999).	
  	
  Snakes,	
  mammals,	
  and	
  avian	
  predators	
  

depredate	
  nests	
  (Hughes	
  1999).	
  	
  Wide	
  variety	
  of	
  

predators	
  and	
  climate	
  influences,	
  thus	
  probably	
  no	
  

overall	
  change	
  in	
  predation	
  rate.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

Use	
  of	
  other	
  bird’s	
  nests	
  for	
  eggs,	
  but	
  brood	
  parasitism	
  is	
  

only	
  facultative	
  in	
  this	
  species	
  and	
  seems	
  to	
  only	
  occur	
  

rarely.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  in	
  

this	
  species	
  expected	
  

to	
  change?	
  

Numerous	
  diseases	
  and	
  parasites	
  have	
  been	
  documented,	
  

but	
  no	
  information	
  indicating	
  significant	
  negative	
  effects	
  

on	
  populations.	
  Seldom	
  subject	
  to	
  brood	
  parasitism	
  by	
  

brown-­‐headed	
  cowbird	
  (Molothrus	
  ater)	
  as	
  nesting	
  

duration	
  is	
  short	
  (Hughes	
  1999).	
  Also	
  lays	
  eggs	
  in	
  the	
  

nests	
  of	
  other	
  conspecifics	
  or	
  other	
  species,	
  but	
  there	
  are	
  

few	
  records	
  (Hughes	
  1999).

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

No	
  information	
  on	
  competitors.

0
USDA Forest Service RMRS-GTR-302. 2013. 107

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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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Corman, T.E. and C. Wise-Gervais, ed. 2005. The Arizona Breeding Bird Atlas. Albuquerque, New Mexico: 

University of New Mexico Press.

Emanuel, K. 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 436:686–688.

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

Fleischer, R. C., M. T. Murphy, and L. E. Hunt. 1985. Clutch size increase and intraspecific brood parasitism in 

the yellow-billed cuckoo. Wilson Bulletin 97:127–128.

Franzeb, K. E. and S. A. Laymon. 1993. A reassessment of the taxonomic status of the yellow-billed cuckoo. 

Western Birds 24:17–28.

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

6:16–17. 

Glinski, R. L. and R. D. Ohmart. 1984. Factors of reproduction and population densities in the Apache cicada 

(Diceroprocta apache). Southwestern Naturalist 29:73–79.

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.

Hamilton III, W. J. and M. E. Hamilton. 1965. Breeding characteristics of yellow-billed cuckoos in Arizona. 

Proceedings of the California Academy of Sciences 32:405–432.v

Heath, J. E. and P. J. Wilkin. 1970. Temperature responses of the desert cicada, Diceroprocta apache

(Homoptera, Cicadidae). Physiological Zoology 43:145–154.

Howe, W. H. 1986. Status of the Yellow-billed Cuckoo (Coccyzus americanus) in New Mexico. Rep. 516.6-75-

09. New Mexico Department of Game and Fish, Santa Fe.

Hughes, Janice M. 1999. Yellow-billed Cuckoo (Coccyzus americanus), The Birds of North America Online (A. 

Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Available online from http://bna.birds.cornell.edu/bna/

species/418.

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.

Laymon, S. A. 1980. Feeding and nesting behavior of the Yellow-billed Cuckoo in the Sacramento Valley. 

Wildlife Management Administrative Report 802. California Deptartment of Fish and Wildlife, Sacramento.

Laymon, S. A. and M. D. Halterman. 1987. Can the western subspecies of the yellow-billed cuckoo be saved 

from extinction? Western Birds 18:19–25.

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. Global Environmental 

Change 1:351–364. 

Lite, S. J. and J. C. Stromberg. 2005. Surface water and ground-water thresholds for maintaining Populus–

Salix forests, San Pedro River, Arizona. Biological Conservation 125:153–167.
108 USDA Forest Service RMRS-GTR-302. 2013.

Magrin, G., C. Gay García, D. Cruz Choque, [and others]. 2007. Latin America. Pages 581–615 in Climate 

Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth 

Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. 

Palutikof, P.J. van der Linden and C.E. Hanson, eds., Cambridge University Press, Cambridge, U.K.

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.

Nolan, V. and C. F. Thompson. 1975. The occurrence and significance of anomalous reproductive activities in 

two North American non-parasitic cuckoos Coccyzus sp. Ibis 117: 496–503.

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.

Rohwer, S., K. Hobson, and V. Rohwer. 2009. Migratory double breeding in neotropical migratory birds. 

Proceedings of the National Academy of Sciences 106:19050–19055.

Seager, R., M. Ting, 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.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

Steinitz, C., R. Anderson, H. Arita, [and others]. 2005. Alternative Futures for Landscapes in the Upper 

San Pedro River Basin of Arizona and Sonora. Pages 93–100 in Bird Conservation Implementation and 

Integration in the Americas: Proceedings of the Third International Partners in Flight Conference. Ralph, C. 

J. and T. D. Rich, eds. U.S. Dept. of Agriculture, Forest Service, Gen. Tech. Rep. PSW-GTR-191.

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.

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.

USFWS (United States Fish and Wildlife Service). 2001. 12-month finding for a petition to list the yellow-billed 

cuckoo (Coccyzus americanus) in the western continental United States. Federal Register 66: 38611–38626. 

Weiss, J. L. and J. T. Overpeck. 2005. Is the Sonoran Desert losing its cool? Global Change Biology 11:2065–

2077.

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role of ecophysiology. Biological Invasions 2:123–140.
USDA Forest Service RMRS-GTR-302. 2013. 109

Mexican Spotted Owl 

(Strix occidentalis lucida)

SUMMARY

Spotted owls were assessed to be vulnerable to declines associated with future climate change. Significant 

vulnerabilities are related to upward shifts of forest habitats, physiological thresholds, and fluctuations in prey 

populations. Management with climate change will depend on balancing various risks related to fire severity, 

cool microsites, drought mortality of trees, and factors that affect prey populations.

Introduction

Mexican spotted owls are geographically isolated and genetically distinct from the other two spotted owl 

subspecies: northern and California. The Mexican spotted owl was listed as a threatened species in 1993 

(USFWS 1995). It is a species of greatest conservation need, Tier 1A, in Arizona State Wildlife Action Plan 

or SWAP (AGFD 2006). Main threats to current populations have been identified as habitat alteration from 

silvicultural practices and catastrophic wildfires.

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

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

section of the main document.

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

-5 0 5 

VULNERABILITY Score Uncertainty

Habitat 1.3 29%

Physiology 0.8 0%

Phenology 2.5 50%

Interactions 1.0 40%

Overall 5.3 27%
110 USDA Forest Service RMRS-GTR-302. 2013.

Other Threats and Interactions With Climate

There have been considerable changes in fire regimes at Fort Huachuca since the 1870s (Danzer and others 

1996). Fires of varying intensities were common in the past, but fire-free intervals have been lengthened 

considerably through fire suppression (Danzer and others 1996). With fewer fires, recruitment has increased 

for shade-tolerant species such as Douglas fir and Gambel’s oak. Additional changes in forest composition 

occurred when the more accessible slopes were logged (Danzer and others 1996). Although fire-suppressed 

forests are suitable habitat for Mexican spotted owls, they are also more prone to high intensity, standreplacing fires, which will remove suitable habitat for long periods, as well as drought mortality. In the short 

term, owls remained on their territories and reproduced successfully following large fires in California, 

Arizona, and New Mexico (Bond and others 2002), thus this species may be at least partly resilient to 

increasing fires. Conversely, interactions of fire with drought mortality in trees and invasion by grass species 

will likely shift fire regimes and habitats outside the range of suitability for spotted owls. Hotter temperatures, 

especially during dry periods, will increase ignition of fuels. Variable rainfall (i.e., wet years followed by dry 

years) will also encourage fire. Fires more frequently occur at lower elevations where precipitation is lower 

and there is the additional interaction of invasive grass species that favor frequent fire. Fires can then spread 

upslope.

Research Needs

Interaction among drought, fire, vegetation, climate, and suitable owl habitat adds complexity to predicting 

the future of Mexican spotted owls. Dense vegetation and shade characterisitics of habitats are thought to be 

important for thermoregulation and may affect habitat selection but have not been studied in detail. Although 

studied to some extent, more detailed study and risk assessment are needed to assess how to best maintain 

dense forest habitats suitable for spotted owls as climate changes. Woodland and canyon habitats, which are 

additionally used by owls, also need more detailed study. A risk assessment of climate effects on spotted owl 

habitats should include landscape variables such as topography, adjacent vegetation types, and proximity of 

weed infestations.

Management Implications

Management related to fuels and fire is likely important to this species, particularly because a number of 

vulnerabilities to climate change are habitat related. Prescribed fire or thinning may be helpful to increase 

resilience of forests to stand-replacing fires that can encourage conversion to other vegetation types and 

resilience of large trees to drought mortality. Protection of cool microsites and canyon bottoms will be 

important as temperatures increase. Management that enhances prey populations through changes in forest 

debris or encourages understory vegetation may also enhance resilience.

Restrictions in activities during breeding are common management actions for this species. Changes in 

breeding timing should be anticipated and restrictions altered accordingly.
USDA Forest Service RMRS-GTR-302. 2013. 111

Habitat:	
  Mexican	
  Spotted	
  Owl	
  (Strix	
  occidentalis	
  lucida)

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?

Mexican	
  spotted	
  owls	
  occur	
  mostly	
  in	
  montane	
  forests	
  

and	
  canyons.	
  Preferred	
  forest	
  types	
  include	
  ponderosa	
  

pine,	
  mixed-­‐conifer,	
  and	
  pine-­‐oak	
  forests	
  with	
  highest	
  

densities	
  in	
  mixed-­‐conifer	
  forests	
  (USFWS	
  1995).	
  At	
  Fort	
  

Huachuca,	
  Mexican	
  spotted	
  owls	
  occur	
  in	
  canyons	
  with	
  

ponderosa	
  pine	
  and	
  Douglas	
  fir	
  although	
  they	
  probably	
  

also	
  use	
  oak	
  woodlands	
  particularly	
  in	
  winter.	
  Coniferous	
  

forest	
  types	
  are	
  limited	
  to	
  higher	
  elevations	
  (>7000	
  ft)	
  of	
  

Fort	
  Huachuca	
  where	
  precipitation	
  is	
  higher	
  (Wallmo	
  

1955).	
  Following	
  wildfires,	
  most	
  owls	
  remained	
  on	
  their	
  

territories	
  and	
  reproduced	
  successfully	
  (Bond	
  and	
  others

2002).	
  Projected	
  changes	
  in	
  climate	
  indicate	
  that	
  mixed	
  

conifer	
  and	
  pine-­‐oak	
  habitats	
  will	
  be	
  reduced	
  as	
  they	
  shift	
  

to	
  higher	
  elevations.

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	
  forage	
  in	
  a	
  wider	
  range	
  of	
  habitats	
  than	
  are	
  usually	
  

described	
  for	
  nesting	
  (Ganey	
  and	
  Balda	
  1994).	
  Coniferous	
  

forests	
  in	
  the	
  region	
  are	
  likely	
  to	
  be	
  reduced.

1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Nests	
  are	
  built	
  in	
  large	
  trees	
  or	
  in	
  cliffs	
  within	
  closed-­‐

canopy	
  forests	
  or	
  canyons.	
  The	
  most	
  common	
  nest	
  sites	
  

are	
  old	
  raptor	
  nests	
  and	
  witches	
  brooms	
  (USFWS	
  1995).	
  

Availability	
  of	
  nest	
  sites	
  within	
  forests	
  is	
  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?	
  

None	
  known.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Old	
  growth	
  forests	
  with	
  large	
  trees	
  and	
  complex	
  

structure	
  are	
  preferred	
  (Fletcher	
  and	
  Hollis	
  1994).	
  Use	
  of	
  

these	
  microsites	
  may	
  be	
  to	
  escape	
  high	
  temperatures	
  

(Ganey	
  and	
  others	
  1993).	
  Favorable	
  microsites	
  may	
  be	
  

reduced	
  with	
  tree	
  mortality	
  associated	
  with	
  drought,	
  

particularly	
  in	
  dense	
  stands.

1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Adults	
  generally	
  have	
  high	
  site	
  fidelity	
  with	
  most	
  

dispersal	
  by	
  juveniles	
  of	
  both	
  sexes	
  (USFWS	
  1995).	
  Some	
  

owls	
  also	
  migrate	
  to	
  lower	
  elevations	
  in	
  winter.	
  The	
  

recovery	
  plan	
  indicates	
  owls	
  may	
  have	
  very	
  few	
  

movements	
  to	
  adjacent	
  habitat	
  patches	
  but	
  are	
  more	
  

likely	
  to	
  disperse	
  within	
  patches	
  (USFWS	
  1995).	
  

Territorial	
  individuals	
  often	
  have	
  high	
  site	
  fidelity,	
  but	
  

juveniles	
  of	
  both	
  sexes	
  may	
  disperse	
  relatively	
  long	
  

distances.

-­1
112 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Mexican	
  Spotted	
  Owl	
  (Strix	
  occidentalis	
  lucida)

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?

Although	
  observed,	
  most	
  individuals	
  do	
  not	
  migrate	
  or	
  

use	
  specific	
  transitional	
  habitats.

0

Physiology:	
  Mexican	
  Spotted	
  Owl	
  (Strix	
  occidentalis	
  lucida)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Arizona	
  is	
  in	
  the	
  southern	
  portion	
  of	
  the	
  distribution,	
  but	
  

they	
  also	
  occur	
  farther	
  south	
  in	
  northern	
  and	
  central	
  

Mexico.	
  Mexican	
  spotted	
  owls	
  may	
  be	
  less	
  able	
  to	
  

dissipate	
  heat	
  than	
  great	
  horned	
  owls	
  and	
  thus	
  select	
  

cooler	
  microsites	
  (Ganey	
  and	
  others	
  1993).	
  Fairly	
  

intolerant	
  of	
  high	
  temperatures.	
  	
  Predicted	
  increases	
  in	
  

temperatures,	
  particularly	
  during	
  summer,	
  may	
  exceed	
  

thresholds.

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?	
  

Starvation	
  and	
  predation	
  are	
  the	
  most	
  common	
  mortality	
  

causes	
  (USFWS	
  1995).	
  No	
  records	
  of	
  large	
  mortality	
  

events	
  associated	
  with	
  storms	
  or	
  fire	
  were	
  found. 0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Primarily	
  nocturnal	
  when	
  temperatures	
  are	
  cooler.	
  

Activities	
  not	
  likely	
  to	
  be	
  limited.

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?

Moderate	
  endothermic.

0
USDA Forest Service RMRS-GTR-302. 2013. 113

Phenology:	
  Mexican	
  Spotted	
  Owl	
  (Strix	
  occidentalis	
  lucida)

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	
  initiate	
  breeding	
  based	
  on	
  photoperiod	
  with	
  

some	
  flexibility	
  with	
  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?	
  

Eggs	
  are	
  laid	
  in	
  late	
  March,	
  hatch	
  at	
  the	
  beginning	
  of	
  May	
  

with	
  young	
  fledging	
  around	
  mid-­‐June	
  (Ganey	
  1988).	
  

Breeding	
  and	
  nesting	
  likely	
  timed	
  to	
  prey	
  abundance,	
  

which	
  is	
  likely	
  to	
  have	
  changes	
  in	
  peak	
  abundance	
  related	
  

to	
  temperature.

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	
  not	
  distant	
  from	
  nesting	
  locations	
  but	
  not	
  in	
  

direct	
  response	
  to	
  resource	
  levels.

0

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Two	
  eggs	
  are	
  most	
  commonly	
  laid	
  though	
  most	
  pairs	
  do	
  

not	
  breed	
  every	
  year	
  (Ganey	
  1988).	
  

1

Biotic	
  Interactions: Mexican	
  Spotted	
  Owl	
  (Strix	
  occidentalis	
  lucida)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Spotted	
  owls	
  eat	
  a	
  wide	
  variety	
  of	
  prey,	
  but	
  a	
  large

portion	
  of	
  the	
  diet	
  is	
  from	
  small	
  to	
  medium-­‐sized	
  rodents.	
  

A	
  review	
  of	
  diet	
  studies	
  indicated	
  that	
  in	
  the	
  Fort	
  

Huachucua	
  region,	
  the	
  most	
  common	
  prey	
  item	
  was	
  

Peromyscus	
  species	
  followed	
  by	
  woodrats,	
  which	
  by	
  

weight	
  were	
  the	
  most	
  important	
  component	
  of	
  the	
  diet	
  

(USFWS	
  1995).	
  Small	
  rodent	
  abundance	
  generally	
  

fluctuates	
  with	
  rainfall	
  and	
  may	
  be	
  reduced	
  by	
  higher	
  

temperatures	
  and	
  more	
  variable	
  rainfall.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Predation	
  is	
  probably	
  low	
  in	
  adults.	
  Preyed	
  upon	
  by	
  a	
  

variety	
  of	
  raptors,	
  especially	
  great	
  horned	
  owls.	
  No	
  

expected	
  changes	
  in	
  predation	
  rates.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.

0
114 USDA Forest Service RMRS-GTR-302. 2013.

Biotic	
  Interactions: Mexican	
  Spotted	
  Owl	
  (Strix	
  occidentalis	
  lucida)

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?	
  

Little	
  information	
  is	
  available	
  on	
  disease	
  in	
  spotted	
  owls	
  

(USFWS	
  1995).

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Known	
  to	
  compete	
  with	
  barred	
  owls	
  but	
  do	
  not	
  occur	
  in	
  

this	
  region. 0
USDA Forest Service RMRS-GTR-302. 2013. 115

Literature Cited

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Bond, Monica L,. R. J. Gutierrez, Alan B. Franklin, William S. LaHaye, Christopher A. May and Mark E. Seamans. 

2002. Short-term effects of wildfires on spotted owl survival, site fidelity, mate fidelity, and reproductive 

success. Wildlife Society Bulletin 30:1022–1028.

Danzer, S. R., C. H. Baisan, and T. W. Swetnam. 1996. The influence of fire and land-use history on stand 

dynamics in the Huachuca Mountains of Southeastern Arizona. Pages 265–270 in Effects of fire on Madrean 

Province ecosystems: a symposium proceedings. U.S. Dept. of Agriculture, Forest Service, Rocky Mountain 

Forest and Range Experiment Station Gen. Tech Rep. RM-GTR-289.

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

Fletcher, K. W. and H. E. Hollis. 1994. Habitats used, abundance, and distribution of the Mexican Spotted Owl. 

U.S. Department of Agriculture, Forest Service, Region 3, Albuquerque, New Mexico. 86 pp.

Ganey, J. L., R. P. Balda, and R. M. King. 1993. Metabolic rate and evaporative water loss of Mexican spotted 

and great horned owls. Wilson Bull. 10S:64S–6S6.

Ganey, J. L. 1988. Distribution and habitat ecology of Mexican spotted owls in Arizona. M.S. Thesis, Northern 

Arizona Univ., Flagstaff. 229 pp.

Ganey, J. L. and R. P. Balda. 1994. Habitat selection by Mexican spotted owls in northern Arizona. Auk 

111:162–169.

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.

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.

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

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

Seamans, M. E., R. J. Gutiérrez and C. A. May. Mexican Spotted Owl (Strix occidentalis). 2002. Population 

dynamics: influence of climatic variation on survival and reproduction. Auk 119:321–334.

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

USFWS (United States Fish and Wildlife Service). 1995. Recovery plan for the Mexican spotted owl: Vol. 1. 

Albuquerque, New Mexico. 172 pp. 

Wallmo, O. C. 1955. Vegetation of the Huachuca Mountains, Arizona. American Midland Naturalist 54:466–

480

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

role of ecophysiology. Biological Invasions 2:123–140.
116 USDA Forest Service RMRS-GTR-302. 2013.

Elegant Trogon (Trogon elegans)

SUMMARY

Currently an uncommon migrant in Arizona, warmer winters may improve conditions for the elegant trogon, 

which could become a year-round resident at Fort Huachuca. Although abiotic conditions may improve, suitable forest habitats and trogon populations overall are vulnerable to declines. Management related to fire and 

invasive grasses will be important to preservation of suitable habitats. The possibility of year-round residency 

should also be anticipated in management plans.

Introduction

The elegant trogon has no Federal status but is a USFS sensitive species and a species of greatest conservation 

concern, Tier 1B, in Arizona (AGFD 2006). It is also designated as a species as risk (SWESA 2006). Breeding 

distribution in the United States is limited to a small area in southern Arizona and New Mexico. Overall 

population trend seems to be stable but may have large annual fluctuations in Arizona, although these may be 

related to variation in census methods (Kunzmann and others 1998). 

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• Decreased annual rainfall in Central America (Magrin and others 2007)

• Conversion of tropical forest to savannah in northern South America (Magrin and others 2007)

-5 0 5 

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 2.0 14%

Physiology -1.2 50%

Phenology 3.8 25%

Interactions 0.0 60%

Overall 4.1 32%
USDA Forest Service RMRS-GTR-302. 2013. 117

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

Fires, particularly those of high severity, can negatively impact vegetation types preferred by trogons as well 

as suitable substrates for nesting cavities. Where forests are adjacent to grasslands, fires can occur more 

frequently through fire spread. Wildfires are expected to become more frequent with projected increases in 

temperature and, in particular, may be more frequent in mesic environments where fire spread has generally 

been more limited (Rogers and Vint 1987, Swetnam and Betancourt 1990). In addition to temperature 

interactions, projected increases in climate variability will also increase fire occurrence when years of high 

rainfall are followed by dry/hot conditions, creating conditions conducive both to fire ignition and fuel 

accumulation. Buffelgrass (Pennisetum ciliare) is a native perennial of Africa introduced for livestock grazing 

that is rapidly expanding and becoming increasingly problematic in the Sonoran Desert. 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). Drought mortality in forests can also 

encourage fires but can increase snags available for nesting cavities.

Research Needs

Many life history aspects are not well known for this species, and there have been few studies outside Arizona 

(Kunzmann and others 1998). Basic life history information related to energetics and migration would be 

particularly relevant to climate change.

Management Implications

The potential for increasing impacts from invasive African grasses and increasing fires warrants inclusion 

in management planning and implementation of preventative actions. Prescribed fires and mechanical 

treatments, as well as invasive grass control, may increase forest resiliency to stand-replacing wildfires that 

would reduce habitat availability.

Like many secondary cavity nesters, elegant trogons may be limited by cavity availability. A study by Hakes 

(1983) showed trogons did not use any of 30 nestboxes in the Huachuca Mountains over 4 years. Nest boxes 

are not likely to alleviate this scarcity although competition would be reduced if competing species use nest 

boxes preferentially. Suitable substrates for cavity creation should be protected.

Populations of elegant trogons in southeastern Arizona are thought to be migratory because they are 

intolerant of cold winter temperatures. Winter temperatures are projected to increase and year-round 

populations occur in nearby northern Mexico. Thus, there is some potential that elegant trogons may begin 

to use habitats at Fort Huachuca year round. The prediction of shifting populations is supported by records of 

nesting in 2008 and 2009 at Montezuma Castle National Monument, far north of previous records. Mitigation 

measures based on assumption of seasonal presence, such as activities that are restricted by date, would then 

need to be reconsidered. 
118 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Elegant	
  Trogon	
  (Trogon	
  elegans)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Area	
  and	
  

distribution:

breeding

Is	
  the	
  area	
  or	
  location	
  

of	
  the	
  associated	
  

vegetation	
  type	
  used	
  

for	
  breeding	
  activities	
  

by	
  this	
  species	
  

expected	
  to	
  change?

In	
  Arizona,	
  reported	
  to	
  breed	
  regularly	
  in	
  Atascosas,	
  

Chiricahua,	
  Huachuca,	
  and	
  Santa	
  Rita	
  mountain	
  ranges	
  

(Kunzmann	
  and	
  others	
  1998).	
  In	
  United	
  States,	
  breeding	
  

habitat	
  includes	
  high	
  elevation	
  pine	
  and	
  pine-­‐oak	
  forests	
  

and	
  Arizona	
  sycamore	
  (Platanus	
  wrightii)	
  riparian	
  

woodland	
  (Hall	
  1996	
  in	
  Kunzmann	
  and	
  others	
  1998).	
  In	
  

Arizona,	
  abundance	
  is	
  greatest	
  in	
  canyons	
  with	
  riparian	
  

vegetation	
  dominated	
  by	
  sycamores,	
  pinyons,	
  junipers,	
  or	
  

pines	
  (Hall	
  1996	
  in	
  Kunzmann	
  and	
  others	
  1998).	
  Upland	
  

areas	
  also	
  used	
  and	
  are	
  often	
  dominated	
  by	
  mesquite	
  

(Prosopis	
  sp.)	
  (Hall	
  and	
  Mannan	
  1999).	
  Riparian	
  areas	
  

and	
  associated	
  vegetation	
  are	
  likely	
  to	
  decline	
  with	
  

higher	
  temperatures	
  and	
  reduced	
  winter	
  precipitation.

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?

Some	
  records	
  of	
  overwintering	
  in	
  Arizona,	
  but	
  generally	
  

winter	
  in	
  Mexico	
  and	
  Central	
  America	
  where	
  trogons	
  are	
  

also	
  year-­‐round	
  residents	
  (Kunzmann	
  and	
  others	
  1998).	
  

No	
  information	
  on	
  what	
  region	
  U.S.	
  individuals	
  migrate	
  

to.	
  Semiarid	
  pine-­‐oak	
  and	
  scrub	
  forests	
  to	
  high	
  elevation	
  

pine	
  forests	
  in	
  Mexico	
  and	
  Central	
  America	
  (Kunzmann	
  

and	
  others	
  1998).	
  High	
  elevation	
  forest	
  types	
  are	
  

expected	
  to	
  shift	
  upslope,	
  reducing	
  area,	
  and	
  woody	
  

species	
  in	
  semiarid	
  regions	
  will	
  likely	
  decline	
  with	
  higher	
  

temperatures	
  and	
  increased	
  fire	
  occurrence.

1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

They	
  nest	
  primarily	
  in	
  abandoned	
  woodpecker	
  cavities,	
  

preferably	
  in	
  large	
  sycamores,	
  but	
  also	
  in	
  oaks	
  or	
  pines	
  

within	
  300 m	
  of	
  water	
  (Kunzmann	
  and	
  others	
  1998).

There	
  are	
  old	
  reports	
  of	
  this	
  species	
  nesting	
  in	
  banks,	
  but	
  

Kunzmann	
  and	
  others	
  (1998)	
  found	
  no	
  reliable	
  evidence	
  

to	
  support	
  this.	
  Large	
  trees	
  take	
  a	
  long	
  time	
  to	
  regrow	
  

and	
  are	
  vulnerable	
  to	
  fire,	
  drought	
  mortality,	
  and	
  

declining	
  water	
  tables.

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?	
  

None	
  known.

0

5.	
  Habitat	
  

quality

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Higher	
  nest	
  success	
  was	
  observed	
  in	
  nests	
  in	
  cavities	
  in	
  

trees	
  with	
  larger	
  diameters	
  and	
  height	
  of	
  vegetation	
  to	
  

south	
  of	
  nest	
  tree	
  was	
  greater	
  (Hall	
  1996	
  in	
  Kunzmann	
  

and	
  others	
  1998).	
  Dense	
  understory	
  vegetation	
  was	
  also	
  

associated	
  with	
  greater	
  reproductive	
  success	
  (Hall	
  and	
  

Mannan	
  1999).

Dense	
  understory	
  vegetation	
  is	
  expected	
  to	
  remain	
  

unchanged	
  within	
  suitable	
  habitats.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Both	
  sexes	
  are	
  highly	
  mobile.

-­1
USDA Forest Service RMRS-GTR-302. 2013. 119

Habitat:	
  Elegant	
  Trogon	
  (Trogon	
  elegans)

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?

Most	
  of	
  the	
  U.S.	
  population	
  migrates	
  in	
  winter,	
  but	
  

unknown	
  migration	
  routes	
  and	
  distance.	
  Regardless,	
  the	
  

species	
  likely	
  uses	
  transitional	
  habitats	
  between	
  winter	
  

and	
  breeding	
  grounds. 1

Physiology:	
  Elegant	
  Trogon	
  (Trogon	
  elegans)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Members	
  of	
  the	
  Trogonidae	
  family	
  are	
  not	
  tolerant	
  of	
  cold	
  

temperatures,	
  which	
  likely	
  limit	
  their	
  northern	
  

distribution	
  (Kunzmann	
  and	
  others	
  1998).	
  When	
  migrant	
  

trogons	
  arrive	
  in	
  Arizona	
  to	
  breed,	
  mountain	
  ranges	
  used	
  

by	
  this	
  species	
  are	
  nearly	
  free	
  of	
  snow	
  (Kunzmann	
  and	
  

others	
  1998).	
  Low	
  resting	
  metabolic	
  rate	
  of	
  a	
  related	
  

species	
  (Trogon	
  rufus)	
  relative	
  to	
  other	
  bird	
  families	
  may	
  

reflect	
  low	
  ability	
  to	
  generate	
  heat	
  (Kunzmann	
  and	
  others

1998).	
  Warmer	
  winters	
  may	
  improve	
  winter	
  conditions,	
  

although	
  currently	
  no	
  trogons	
  present	
  in	
  Arizona	
  year-­‐

round.	
  Fort	
  Huachuca,	
  therefore,	
  may	
  become	
  more	
  

suitable	
  for	
  wintering	
  birds.	
  Use	
  of	
  semi-­‐arid	
  regions	
  

indicates	
  they	
  may	
  be	
  fairly	
  tolerant	
  of	
  hot	
  conditions,	
  but	
  

no	
  data	
  available.

-­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	
  on	
  mortality	
  related	
  to	
  storms,	
  but	
  they	
  

are	
  often	
  associated	
  with	
  mortality	
  in	
  birds.	
  	
  Central	
  

America	
  (wintering	
  grounds)	
  is	
  already	
  subject	
  to	
  

increased	
  hurricanes,	
  heavy	
  rains,	
  and	
  dry	
  periods.	
  

Drought	
  was	
  suggested	
  as	
  a	
  factor	
  behind	
  low	
  population	
  

numbers	
  in	
  the	
  1950s.	
  Increasing	
  drought	
  duration	
  is	
  

projected	
  for	
  the	
  southwestern	
  United	
  States.

1

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

No	
  limitations	
  known.

0

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

This	
  species	
  seems	
  to	
  have	
  flexible	
  migratory	
  behaviors,	
  

which	
  may	
  help	
  it	
  cope	
  with	
  regional	
  variability	
  in	
  

resources.	
  Extent	
  of	
  this	
  flexibility	
  in	
  the	
  population,	
  

however,	
  is	
  unknown.

-­1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic	
  (relative	
  to	
  other	
  vertebrates). 0
120 USDA Forest Service RMRS-GTR-302. 2013.

Phenology:	
  Elegant	
  Trogon	
  (Trogon	
  elegans)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Cues Does	
  this	
  species	
  use	
  

temperature	
  or	
  

moisture	
  cues	
  to	
  

initiate	
  activities	
  

related	
  to	
  fecundity	
  or	
  

survival	
  (e.g.,	
  

hibernation,	
  

migration,	
  breeding)?	
  

Cues	
  not	
  known.	
  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?	
  

Nesting	
  in	
  Alamos	
  in	
  the	
  Mexican	
  state	
  of	
  Sonora	
  is	
  

reported	
  to	
  be	
  timed	
  with	
  the	
  summer	
  rainy	
  season	
  

(Kunzmann	
  and	
  others	
  1998).	
  In	
  Arizona,	
  breeding	
  

initiation	
  dates	
  reported	
  variable	
  among	
  pairs	
  in	
  a	
  two-­‐

year	
  study,	
  with	
  nests	
  begun	
  in	
  May,	
  June,	
  and	
  July	
  (Hall	
  

and	
  Karubian	
  1996).	
  	
  Timing	
  of	
  breeding	
  to	
  rainy	
  season	
  

may	
  be	
  correlated	
  with	
  insect	
  abundance.	
  Timing	
  and	
  

quantities	
  of	
  summer	
  precipitation	
  in	
  the	
  future	
  are	
  

mostly	
  unknown,	
  but	
  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?

Migration	
  and	
  initiation	
  of	
  breeding	
  are	
  separated	
  

geographically	
  and	
  temporally.

1

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

In	
  Arizona,	
  most	
  pairs	
  rear	
  one	
  brood	
  per	
  season	
  

(Kunzmann	
  and	
  others	
  1998).	
  

1

Biotic	
  Interactions:	
  Elegant	
  Trogon	
  (Trogon	
  elegans)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Wide	
  variety	
  of	
  foods	
  taken,	
  but	
  mainly	
  fruit,	
  

grasshoppers,	
  and	
  other	
  insects	
  (Kunzmann	
  and	
  others

1998).	
  Less	
  likely	
  that	
  all	
  food	
  resources	
  will	
  be	
  

synchronously	
  reduced	
  or	
  enhanced.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Predation	
  on	
  adults	
  not	
  well	
  documented	
  and	
  may	
  be	
  

uncommon	
  (Kunzmann	
  and	
  others	
  1998)	
  but	
  likely	
  

includes	
  squirrels	
  and	
  raptors.	
  Nest	
  predation	
  is	
  fairly	
  

rare	
  (Hall	
  and	
  Kurubian	
  1996)	
  and	
  is	
  likely	
  opportunistic	
  

by	
  a	
  variety	
  of	
  species.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

They	
  require	
  other	
  species	
  to	
  excavate	
  cavities.	
  Often	
  nest	
  

in	
  cavities	
  excavated	
  by	
  woodpeckers.	
  No	
  evidence	
  that	
  

cavity	
  creating	
  birds	
  will	
  all	
  decline.

0
USDA Forest Service RMRS-GTR-302. 2013. 121

Biotic	
  Interactions:	
  Elegant	
  Trogon	
  (Trogon	
  elegans)

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	
  cause	
  widespread	
  mortality.

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Intra-­‐specific	
  competition	
  observed	
  in	
  apparent	
  

competition	
  for	
  nest	
  cavities.	
  Both	
  males	
  and	
  females	
  

defend	
  nest	
  cavities	
  against	
  other	
  species	
  of	
  primary	
  and	
  

secondary	
  cavity	
  nesters	
  (e.g.,	
  sulphur-­‐bellied	
  flycatcher,	
  

northern	
  flicker,	
  eared	
  trogon,	
  screech	
  owl)	
  (Kunzmann	
  

and	
  others	
  1998).	
  	
  Competes	
  with	
  other	
  species	
  for	
  

cavities,	
  but	
  no	
  evidence	
  that	
  this	
  is	
  limiting	
  for	
  trogon	
  

populations.

0
122 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

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. 

Hakes, W. E. 1983. Nest boxes as a coppery-tailed trogon management tool. Pages 147–150 in Snag habitat 

management: proceedings of the symposium. (Davis, J. W., G. A. Goodwin, and R. A. Ockenfels, Eds.) USDA 

Forest Service, Rocky Mountain Forest and Range Experiment Station, Gen. Tech. Rep. RM-GTR-99.

Hall, Linnea S. and Jordan O. Karubian. 1996. Breeding behavior of elegant trogons in southeastern Arizona. 

Auk 113:143–150.

Hall, L. S. and R. W. Mannan. 1999. Multiscaled habitat selection by elegant trogons in southeastern Arizona. 

Journal of Wildlife Management 63:451–461.

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.

Kunzmann, M. R., L. S. Hall, and R. R. Johnson. 1998. Elegant Trogon (Trogon elegans). In The Birds of North 

America, A. Poole and F. Gill, eds., No. 357. 

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. Global Environmental 

Change 1:351–364.

Magrin, G., C. Gay García, D. Cruz Choque, [and others]. 2007. Latin America. Pages 581-615 in Climate Change 

2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment 

Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van 

der Linden and C.E. Hanson, eds., 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.

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.

Rogers G. F. and M. Vint. 1987. Winter precipitation and fire in the Sonoran Desert. Journal of Arid 

Environments. 13:47–52.

Seager, R., M. Ting, 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.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

Stromberg, J., S. J. Lite, T. J. Rychener, L. R. Levick, M. D. Dixon, and J. M. 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.
USDA Forest Service RMRS-GTR-302. 2013. 123

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

States. Science 249: 1017–1021.

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

role of ecophysiology. Biological Invasions 2:123–140.
124 USDA Forest Service RMRS-GTR-302. 2013.

Southwestern Willow Flycatcher 

(Empidonax trailii extimus)

SUMMARY

The southwestern willow flycatcher is associated with riparian habitats, which have been largely degraded or 

lost in the Southwest. Climate change is expected to exacerbate the conditions associated with riparian area 

decline. Besides habitat use, we found vulnerability of willow flycatcher populations to decline was associated 

with timing of floods and insect emergence, thermal tolerances, and brood parasitism by brown-headed cowbirds. Management of water inputs for riparian habitats will be important along with control of exotic invasive 

plants, although any impacts originating from Fort Huachuca will be limited when considering the broad scope 

and scale of threats to this species.

Introduction

The southwestern willow flycatcher is one of four currently recognized subspecies and is classified as Federally 

endangered (USFWS 2003). Southwestern willow flycatchers do not occur on Fort Huachuca, but the nearby 

San Pedro River is designated critical habitat for the southwestern willow flycatcher. 

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• 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)

• Conversion of tropical forest to savannah in northern South America (Magrin and others 2007)

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 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 2.7 29%

Physiology 1.7 50%

Phenology 3.8 50%

Interactions 2.0 20%

Overall 9.9 36%
USDA Forest Service RMRS-GTR-302. 2013. 125

Other Threats and Interactions With Climate

Loss and degradation of dense riparian areas is generally cited as the main cause of population declines in 

the southwestern willow flycatcher (USFWS 2003). Degradation has been related to invasion by invasive nonnative species, changing hydrology, water diversions, and livestock grazing (USFWS 2003). Regional climate 

change is likely to exacerbate a number of these conditions, including drying of riparian areas and invasion 

by non-native species, particularly salt cedar. Willow flycatchers will nest in riparian areas dominated by salt 

cedar. Riparian stands with >90% exotics are considered unsuitable (USFWS 2003). It is speculated that salt 

cedar reduces reproductive success in hotter climates because it provides poor shade compared to more 

broad-leafed plants. Depending on the strength of this mechanism, warming in the region may increase the 

more drought tolerant salt cedar while simultaneously increasing the threat of thermal limits on nesting. 

Changes in flood regimes also may impact this species depending on timing.

Research Needs

A wide variety of topics have been investigated for this species. Thermal aspects of their biology and habitat 

will become increasingly important and need more thorough study. In addition, impacts of control measures 

for exotic plants, such as introduced bio-control agents, on willow flycatchers are not well known.

Management Implications

The ability of management actions on Fort Huachuca to mitigate climate change threats to the willow 

flycatcher is limited. Willow flycatchers breed on the San Pedro River and likely seldom encounter habitats on 

Fort Huachuca. Activities that affect hydrology have the potential to impact habitats on the San Pedro River. 

Water conservation measures, many of which are already implemented, are important to protecting area 

water tables. Vegetation management can further affect run-off. In light of the multitude of threats to water, 

including increasing droughts, warmer temperatures, declining water tables, and expansion of exotic plants, 

riparian habitats will likely decline. 
126 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Southwestern	
  Willow	
  Flycatcher	
  (Empidonax	
  trailii	
  extimus)

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?

Often	
  associated	
  with	
  shrubby	
  and	
  wet	
  habitats	
  

(Sedgwick	
  2000).	
  	
  Nests	
  in	
  flooded	
  areas	
  with	
  willow	
  

dominated	
  areas	
  but	
  also	
  with	
  non-­‐native	
  saltcedar	
  and	
  

Russian	
  olive.	
  Expected	
  reductions	
  in	
  water	
  availability	
  

due	
  to	
  high	
  evaporative	
  losses	
  in	
  the	
  Southwest	
  and	
  

increasing	
  demands	
  from	
  growing	
  human	
  populations.	
  

Lower	
  water	
  tables	
  will	
  favor	
  salt cedar	
  over	
  willow.	
  

Generally,	
  does	
  not	
  occupy	
  areas	
  dominated	
  by	
  exotics	
  

(Sogge	
  and	
  Marshall	
  2000),	
  but	
  can	
  successfully	
  nest	
  in	
  

some	
  saltcedar-­‐dominated	
  habitats	
  (Sogge	
  and	
  others

2006).	
  Fire	
  may	
  increase	
  shrubby	
  habitats,	
  but	
  Paxton	
  

and	
  others	
  (1996)	
  noted	
  that	
  fire	
  destroyed	
  habitat.

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?

Winters	
  in	
  southern	
  Mexico,	
  Central	
  America,	
  and	
  

northern	
  South	
  America	
  (Sedgwick	
  2000).	
  Wintering

habitat	
  dominated	
  by	
  shrubs	
  in	
  proximity	
  to	
  water.	
  	
  

Occur	
  mainly	
  in	
  lowland	
  areas	
  where	
  agricultural	
  and	
  

ranching	
  activities	
  occur	
  (Lynn	
  and	
  others	
  2003). Drying	
  

in	
  these	
  regions	
  will	
  likely	
  decrease	
  habitat	
  availability.

1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Shrubs	
  and	
  small	
  trees	
  used	
  for	
  nesting	
  substrates.	
  

Additionally,	
  willow	
  flycatchers	
  will	
  not	
  nest	
  if	
  water	
  is	
  

not	
  flowing (Johnson	
  and	
  others	
  1999).	
  	
  Stream	
  flows	
  

expected	
  to	
  be	
  reduced,	
  particularly	
  later	
  in	
  the	
  year	
  

when	
  nesting	
  occurs.

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?	
  

None	
  known.

0

5.	
  Habitat	
  

quality	
  

Within	
  habitats	
  

occupied,	
  are	
  features	
  

of	
  the	
  habitat	
  

associated	
  with	
  better	
  

reproductive	
  success	
  

or	
  survival	
  expected	
  

to	
  change?	
  

Increased	
  shrub	
  cover	
  associated	
  with	
  reproductive	
  

success (Bombay	
  and	
  others	
  2003).	
  	
  Low	
  fecundity	
  and	
  

starvation	
  in	
  nestlings	
  associated	
  with	
  low	
  snowpack	
  and	
  

drying	
  of	
  marshes	
  in	
  Oregon	
  (Sedgwick	
  2000).	
  Flooding	
  

may	
  be	
  associated	
  with	
  reduced	
  predation	
  by	
  mammalian	
  

predators	
  (Cain	
  and	
  others	
  2003).	
  Flooding	
  may	
  increase	
  

with	
  warmer	
  winter	
  temperatures,	
  but	
  expected	
  lower	
  

overall	
  water	
  output	
  and	
  advancement	
  of	
  flood	
  pulse	
  may	
  

shift	
  pulse	
  too	
  early	
  to	
  benefit	
  nesting.	
  Salt cedar,	
  while	
  

used	
  for	
  nesting,	
  may	
  be	
  limiting	
  for	
  nesting	
  in	
  hotter	
  

climates	
  because	
  it	
  does	
  not	
  provide	
  needed	
  shade

(Hunter	
  1988).	
  Decreased	
  streamflow	
  will	
  likely	
  drop	
  

water	
  tables	
  and	
  favor	
  salt cedar	
  over	
  willow,	
  which	
  will	
  

be	
  detrimental	
  to	
  the	
  extent	
  that	
  salt cedar	
  decreases	
  

quality.	
  This	
  decrease	
  seems	
  likely	
  because	
  of	
  the	
  lack	
  of	
  

microclimate	
  advantage	
  in	
  salt cedar,	
  which	
  will	
  be	
  more	
  

critical	
  as	
  temperatures	
  increase.

1

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Highly	
  mobile.	
  Fairly	
  high	
  site	
  fidelity	
  to	
  breeding	
  

grounds	
  (Sedgwick	
  2000),	
  but	
  known	
  cases	
  of	
  

recolonization	
  of	
  habitats.	
  Likely	
  has	
  a	
  good	
  capacity	
  to

shift	
  with	
  changes	
  in	
  habitat.

-­1
USDA Forest Service RMRS-GTR-302. 2013. 127

Habitat:	
  Southwestern	
  Willow	
  Flycatcher	
  (Empidonax	
  trailii	
  extimus)

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?

Long-­‐distant	
  migrant	
  through	
  a	
  variety	
  of	
  habitats.

1

Physiology:	
  Southwestern	
  Willow	
  Flycatcher	
  (Empidonax	
  trailii	
  extimus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Decline	
  of	
  willow	
  flycatchers	
  associated	
  with	
  spread	
  of	
  

tamarisk,	
  which	
  may	
  not	
  have	
  the	
  thermal	
  protection	
  of	
  

broadleaf	
  shrubs	
  (Hunter	
  1988),	
  although	
  flycatchers	
  

nest	
  successfully	
  in	
  tamarisk	
  in	
  many	
  areas (Sogge	
  and	
  

others	
  2006).	
  	
  Unknown	
  if	
  there	
  are	
  similar	
  thermal	
  

limitations	
  for	
  adults.	
  Moist	
  and	
  shady	
  microclimates	
  may	
  

be	
  associated	
  with	
  relatively	
  late	
  nesting	
  and	
  

accompanying	
  hot	
  temperatures	
  (Sogge	
  and	
  Marshall	
  

2000).	
  It	
  is	
  likely	
  that	
  this	
  species	
  will	
  be	
  exposed	
  to	
  

higher	
  temperatures	
  that	
  will	
  reduce	
  nesting	
  success.

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?

Not	
  expected	
  to	
  be	
  exposed	
  to	
  greater	
  storms	
  along	
  the	
  

interior	
  migration	
  routes	
  used	
  by	
  southwestern	
  willow	
  

flycatcher.	
  No	
  extreme	
  weather	
  mortality	
  recorded	
  

(except	
  for	
  nestlings—see	
  Habitat	
  Question	
  5). 0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

No	
  known	
  limits	
  to	
  diurnal	
  activity.	
  Activity	
  may	
  be	
  

somewhat	
  buffered	
  by	
  occurrence	
  in	
  moist	
  environments.

0

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

No.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic. 0
128 USDA Forest Service RMRS-GTR-302. 2013.

Phenology:	
  Southwestern	
  Willow	
  Flycatcher	
  (Empidonax	
  trailii	
  extimus)

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)?	
  

Photoperiod	
  likely	
  important	
  for	
  timing	
  migration.	
  No	
  

change	
  in	
  cue	
  expected.

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?	
  

Short	
  nesting	
  season	
  is	
  thought	
  to	
  be	
  limited	
  by	
  short	
  

duration	
  of	
  resource	
  availability (Sedgwick	
  2000).	
  Insects	
  

may	
  emerge	
  earlier	
  or	
  become	
  more	
  variable	
  with	
  more	
  

variable	
  rainfall. 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?

Potentially	
  large	
  difference	
  in	
  migration	
  cues	
  and	
  insect	
  

emergence—not	
  tightly	
  related	
  in	
  space	
  or	
  time.	
  	
  

1

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

Generally	
  single	
  brooded	
  with	
  a	
  fairly	
  short	
  breeding	
  

season	
  (Sedgwick	
  2000). 1

Biotic	
  Interactions:	
  Southwestern	
  Willow	
  Flycatcher	
  (Empidonax	
  trailii	
  

extimus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Willow	
  flycatchers	
  are	
  primarily	
  insectivorous (Sedgwick	
  

2000).	
  Years	
  of	
  low	
  rainfall	
  associated	
  with	
  reduced	
  food	
  

supplies	
  and	
  lower	
  reproductive	
  success.	
  Dry	
  periods	
  and	
  

rainfall	
  variability	
  both	
  expected	
  to	
  increase.

1

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Various	
  predators (Sedgwick	
  2000).	
  No	
  overall	
  changes	
  in	
  

predation	
  rates	
  expected. 0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

No	
  symbionts.

0
USDA Forest Service RMRS-GTR-302. 2013. 129

Biotic	
  Interactions:	
  Southwestern	
  Willow	
  Flycatcher	
  (Empidonax	
  trailii	
  

extimus)

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?	
  

Nests	
  are	
  parasitized	
  by	
  brown-­‐headed	
  cowbirds,	
  which	
  

mostly	
  cause	
  failure	
  of	
  the	
  genetic	
  young.	
  	
  Currently,

willow	
  flycatcher	
  reproduction	
  occurs	
  relatively	
  late,	
  

which	
  does	
  not	
  allow	
  for	
  breeding	
  attempts	
  too	
  early	
  

from	
  cowbird	
  brood	
  parasitism	
  (Robinson	
  and	
  others

1995).	
  	
  The	
  shorter	
  migration	
  distance	
  in	
  cowbirds	
  will	
  

likely	
  allow	
  cowbirds	
  to	
  keep	
  pace	
  with	
  any	
  advancement	
  

in	
  breeding	
  by	
  willow	
  flycatchers.	
  In	
  addition,	
  cowbirds	
  

possess	
  a	
  number	
  of	
  traits	
  that	
  will	
  incur	
  resilience	
  to	
  

climate	
  change.

1

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

None	
  known.

0
130 USDA Forest Service RMRS-GTR-302. 2013.

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

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

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eds., No. 533. 

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132 USDA Forest Service RMRS-GTR-302. 2013.

Northern Buff-breasted Flycatcher 

(Empidonax fulvifrons pygmaeus)

SUMMARY

The buff-breasted flycatcher was assessed as vulnerable to population declines associated with future climate 

change. Fire is an important factor in habitat suitability for this species; but climate-related fire parameters, 

such as intensity and frequency, make effective management actions difficult to identify albeit increasingly 

relevant. Management related to prescribed burning and post-fire rehabilitation will likely be important to 

sustaining populations of buff-breasted flycatcher.

Introduction

Northern buff-breasted flycatcher has retreated from formerly occupied habitats in Arizona (Bowers and 

Dunning 1994). It currently breeds at Fort Huachuca in the summer and is designated as Tier 1B in Arizona 

State Wildlife Action Plan or SWAP (AGFD 2006) as well as a species at risk (SWESA 2006). The rarity of this 

species in the United States also attracts birders to Fort Huachuca.

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• Decreased annual rainfall in Central America (Magrin and others 2007)

• Conversion of tropical forest to savannah in northern South America (Magrin and others 2007)

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 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 1.3 29%

Physiology 0.8 50%

Phenology 3.8 25%

Interactions 0.0 60%

Overall 5.3 41%
USDA Forest Service RMRS-GTR-302. 2013. 133

Other Threats and Interactions With Climate

Formerly, this species also occurred farther north in central Arizona (Bowers and Dunning 1994). Declines 

during the past century are thought to be due to fire suppression and overgrazing of mountain meadows 

(Bowers and Dunning 1994). Buff-breasted flycatchers have also been found in areas with evidence of high 

severity wildfires, suggesting that these types of fires may be needed to provide preferred habitat (Conway 

and Kirkpatrick 2007). Although cowbird populations could change in the future, brood parasitism may be rare 

because of nest placement in this species (Bowers and Dunning 1994). Overall population trends in the United 

States are unclear with declining trends in some survey areas (Conway and Kirkpatrick 2007) and increasing 

trends in some new or historic habitats (Bowers and Dunning 1994, Kirkpatrick and others 2007).

Research Needs

Despite being on the edge of the species’ distribution, most studies are from Arizona. Studies within more 

central portions of the range in Mexico may provide better information on fitness components and habitat 

requirements. Interaction of habitats with fire is thought to be key to habitat suitability but is not well 

studied. Further study is needed to identify fire frequencies and intensities that are important to sustainable 

populations.

Management Implications

Foraging habitats are thought to improve with clearing of the understory such as by low severity fires (Martin 

and Morrison 1999). Other studies have suggested that more intense fires are needed to provide sustainable 

habitats (Conway and Kirkpatrick 2007). The degree of fire severity seems to be an important variable in 

habitat suitability, but time since fire may also play a role. It has been suggested that prescribed fires will 

be unable to improve habitat for this species, and fires of higher intensity may be needed (Conway and 

Kirkpatrick 2007). High intensity wildfires that will be encouraged by very hot conditions and variable rainfall, 

along with large areas of continuous fuels, are likely to result in high tree mortalities and loss of habitat; thus, 

the relationship between sustainable populations and fire seems to be a matter of degree. Prescribed fires 

or mechanical treatments may help prevent very large and intense wildfires that would almost certainly be 

detrimental. Forests that have regrown following burning may be important habitats, at least in the short 

term, thus post wildfire management and restoration are important management considerations.
134 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Northern	
  Buff-­breasted	
  Flycatcher	
  (Empidonax	
  fulvifrons	
  

pygmaeus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Area	
  and	
  

distribution:

breeding

Is	
  the	
  area	
  or	
  location	
  

of	
  the	
  associated	
  

vegetation	
  type	
  used	
  

for	
  breeding	
  activities	
  

by	
  this	
  species	
  

expected	
  to	
  change?

Occupies	
  open	
  oak/pine	
  woodlands	
  and	
  riparian	
  areas	
  at	
  

higher	
  elevations	
  (Bowers	
  and	
  Dunning	
  1994).	
  In	
  

Arizona,	
  often	
  found	
  in	
  pine	
  forests	
  with	
  a	
  sparse	
  oak	
  

understory	
  (Martin	
  and	
  Morrisson	
  1999).	
  Oak	
  woodlands	
  

and	
  riparian	
  areas	
  will	
  likely	
  be	
  reduced	
  by	
  higher	
  

temperatures,	
  upslope	
  shifts,	
  and	
  increased	
  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?

Migratory	
  in	
  northern	
  part	
  of	
  its	
  range,	
  including	
  Arizona.	
  

Winter	
  habitats	
  in	
  Mexico	
  similar,	
  but	
  may	
  also	
  move	
  

downslope	
  into	
  canyons	
  and	
  more	
  low-­‐lying	
  riparian	
  

areas	
  (Bowers	
  and	
  Dunning	
  1994).	
  Wintering	
  grounds	
  in	
  

northern	
  Sonora	
  likely	
  subject	
  to	
  the	
  same	
  threats.

1

3.	
  Habitat	
  

components:	
  

breeding

Are	
  specific	
  habitat	
  

components	
  required	
  

for	
  breeding	
  expected	
  

to	
  change	
  within	
  

associated	
  vegetation	
  

type?	
  

Arizona	
  nests	
  are	
  usually	
  in	
  a	
  conifer	
  with	
  a	
  protective	
  

overhanging	
  branch	
  or	
  piece	
  of	
  bark	
  (Bowers	
  and	
  

Dunning	
  1994).	
  Not	
  expected	
  to	
  change	
  within	
  suitable	
  

woodlands. 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?	
  

Reproductive	
  success	
  is	
  higher	
  farther	
  from	
  edges	
  

(Martin	
  and	
  Morrison	
  1999).

Reduced	
  understory	
  vegetation	
  may	
  enhance	
  foraging	
  

opportunities.	
  Unclear	
  how	
  climate	
  may	
  influence	
  

landscape	
  patchiness	
  or	
  understory	
  vegetation.

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?

Arizona	
  populations	
  are	
  migratory	
  through	
  northern	
  

Mexico.

1
USDA Forest Service RMRS-GTR-302. 2013. 135

Physiology:	
  Northern	
  Buff-­breasted	
  Flycatcher	
  (Empidonax	
  fulvifrons	
  

pygmaeus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

None	
  known.	
  Most	
  of	
  this	
  species	
  range	
  is	
  in	
  Mexico	
  and	
  

Central	
  America.

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?	
  

None	
  known.

0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

None	
  known.

0

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

No.	
  

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic. 0

Phenology:	
  Northern	
  Buff-­breasted	
  Flycatcher	
  (Empidonax	
  fulvifrons	
  

pygmaeus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Cues Does	
  this	
  species	
  use	
  

temperature	
  or	
  

moisture	
  cues	
  to	
  

initiate	
  activities	
  

related	
  to	
  fecundity	
  or	
  

survival	
  (e.g.,	
  

hibernation,	
  

migration,	
  breeding)?	
  

Not	
  known,	
  but	
  likely	
  a	
  combination	
  of	
  internal	
  and	
  

external	
  signals.

0
136 USDA Forest Service RMRS-GTR-302. 2013.

Phenology:	
  Northern	
  Buff-­breasted	
  Flycatcher	
  (Empidonax	
  fulvifrons	
  

pygmaeus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

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?	
  

Nest	
  during	
  the	
  (current)	
  dry	
  season	
  in	
  Arizona,	
  May	
  

through	
  June	
  (Bowers	
  and	
  Dunning	
  1994),	
  but	
  no	
  known	
  

consequences	
  for	
  reproduction.	
  Availability	
  of	
  aerial	
  

insects	
  is	
  likely	
  important	
  to	
  nesting,	
  and	
  emergence	
  of	
  

these	
  insects	
  is	
  related	
  to	
  temperature.

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?

Migration	
  timing	
  and	
  cues	
  distant	
  from	
  breeding.

1

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

One	
  reproductive	
  period.

1

Biotic	
  Interactions:	
  Northern	
  Buff-­breasted	
  Flycatcher	
  (Empidonax	
  

fulvifrons	
  pygmaeus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Eats	
  aerial	
  insects	
  but	
  also	
  ants,	
  grasshoppers,	
  and	
  

spiders	
  (Bowers	
  and	
  Dunning	
  1994).

No	
  overall	
  changes	
  anticipated.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Likely	
  various.	
  No	
  overall	
  change	
  in	
  predation	
  levels.

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.	
  Not	
  prone	
  to	
  brood	
  parasitism.

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

None	
  known;	
  possibly	
  other	
  flycatchers	
  although	
  those	
  

are	
  likely	
  similarly	
  vulnerable	
  to	
  climate	
  change. 0
USDA Forest Service RMRS-GTR-302. 2013. 137

Literature Cited

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Bowers, Jr., R. K. and J. B. Dunning, Jr. 1994. Buff-breasted Flycatcher (Empidonax fulvifrons), The Birds of 

North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North 

America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/125.

Conway, Courtney J. and Chris Kirkpatrick. 2007. Effect of forest fire suppression on buff-breasted flycatchers. 

The Journal of Wildlife Management 71:445–457.

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. 

Kelly, A. and M. Goulden. 2008. Rapid shifts in plant distribution with recent climate change. Proceedings of 

the National Academy of Sciences 105:11823–11826.

Kirkpatrick, Chris, Courtney J. Conway, Dominic D. LaRoche. 2007. Range expansion of the buff-breasted 

flycatcher (Empidonax fulvifrons) into the Rincon Mountains, Arizona. Southwestern Naturalist 52:149–152. 

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. Global Environmental 

Change 1:351–364. 

Magrin, G., C. Gay García, D. Cruz Choque, [and others]. 2007. Latin America. Pages 581–615 in Climate 

Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth 

Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. 

Palutikof, P.J. van der Linden and C.E. Hanson, eds., Cambridge University Press, Cambridge, UK.

Martin, John A. and Michael L. Morrison. 1999. Distribution, Abundance, and Habitat Characteristics of the 

Buff-Breasted Flycatcher in Arizona. Condor 101:272–281

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.

Rehfeldt, G.E., N.L. Crookston, M.V. Warwell, J.S. Evans. 2006. Empirical analyses of plant-climate relationships 

for the western United States. International Journal of Plant Sciences 167:1123–1150.

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

climate in southwestern North America. Science, 316:1181–1184.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

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

role of ecophysiology. Biological Invasions 2:123–140.
138 USDA Forest Service RMRS-GTR-302. 2013.

Arizona Shrew (Sorex arizonae)

SUMMARY

Arizona shrews were assessed as vulnerable to declines associated with projected changes in climate. 

Vulnerability is related both to predicted physiological effects and to the species’ association with mesic 

environments, which are likely to dry with increasing temperatures. Preservation of riparian habitats and 

water tables will be key management areas. Many aspects of this species’ response are uncertain, so further 

research efforts will be beneficial.

Introduction

The Arizona shrew is known to occur at Fort Huachuca. Little information is available on this species, but there 

is potential for it to occur in more locations than those currently identified. Currently, it is only known from 

a few mountain locales in southeast Arizona and southwest New Mexico and the Sierra Madre Occidental 

in Mexico. It is a USFWS species of concern (last reviewed in 1994) and a species at risk (SWESA 2006). The 

Arizona shrew is designated as Tier 1B in Arizona State Wildlife Action Plan or SWAP (AGFD 2006) and as 

sensitive by the USDA Forest Service. 

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

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 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 2.1 57%

Physiology 2.5 33%

Phenology 1.3 75%

Interactions 0.0 60%

Overall 6.4 55%
USDA Forest Service RMRS-GTR-302. 2013. 139

Other Threats and Interactions With Climate

Potential threats to this species include removal of downed woody debris through understory clearing and 

firewood collection, intense ground-burning fires that removes ground structure, livestock grazing, and 

development of recreation sites (NatureServe 2009). Threats to understory debris are expected to increase as 

more fires burn under warmer temperatures and more variable precipitation regimes. Increases in invasive 

grasses may also carry more fires from lower elevations. 

Research Needs

Even basic life history traits are not well studied in this species. It is unknown how low severity fires may 

impact this species and its habitats. In addition, it is unknown how different fuel and fire management 

techniques, such as mastication or prescribed fire, affect this species, although they may be critical to reducing 

high severity fires, which remove key habitat elements.

Management Implications

Activities that disturb or remove ground cover, especially in canyons or riparian areas, are likely to negatively 

impact this species, but are generally well regulated because of the concentration of biodiversity in these 

areas. Protection of water sources and water tables will be important. Riparian areas may be particularly 

prone to drying with warmer temperatures and increased high severity wildfires. Activities that increase fire 

occurrence from surrounding areas could contribute to fire incidence. Management efforts to reduce forest 

fuels and manipulate fire severity, although increasing resiliency of some forest elements, may also reduce 

downed woody debris that this species is dependent on. Even low severity fires could remove important forest 

debris although patchy burning patterns may leave enough habitat intact. On the other hand, fire suppression 

efforts will eventually increase the risk of higher severity fires that will reduce availability of unburned patches 

and potential refugia for this species when fires inevitably occur. Management plans should include post-fire 

actions that can rehabilitate or protect shrew habitat.
140 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Arizona	
  Shrew	
  (Sorex	
  arizonae)

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	
  mesic	
  environments,	
  such	
  as	
  riparian	
  edges,	
  in	
  

dense	
  oak	
  woodlands	
  or	
  conifer	
  forest;	
  although	
  may	
  also	
  

be	
  adjacent	
  to	
  dry	
  environments	
  that	
  support	
  agave	
  and	
  

cactus	
  (BISON-­‐M).	
  Also	
  associated	
  with	
  boulders	
  and	
  

logs.	
  One	
  study	
  in	
  Garden	
  Canyon,	
  Arizona,	
  found	
  this	
  

species	
  in	
  riparian	
  habitats	
  above	
  1500 m	
  (Simons	
  and	
  

others	
  1990).	
  Generally	
  found	
  in	
  canyon	
  bottoms	
  and	
  

often	
  near	
  springs	
  or	
  along	
  dry	
  creek	
  beds.	
  Riparian	
  

edges,	
  dense	
  woodlands	
  are	
  likely	
  reduced	
  by	
  warming	
  

and	
  increased	
  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?	
  

Desert	
  shrews	
  (Notiosorex	
  crawfordi)	
  build	
  nests	
  of	
  bark	
  

and	
  leaves	
  in	
  protected	
  locations	
  for	
  reproduction	
  and	
  

torpor	
  (NatureServe	
  2009).	
  Specificity	
  of	
  materials	
  for	
  

this	
  species	
  is	
  unknown,	
  thus	
  effects	
  are	
  unknown. 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?	
  

Forage	
  in	
  and	
  under	
  litter	
  (BISON-­‐M),	
  but	
  no	
  known	
  

relationship	
  between	
  litter	
  quantity	
  and	
  foraging	
  success.	
  

Litter	
  should	
  remain	
  unchanged	
  in	
  suitable	
  habitats.

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Male	
  shrews	
  of	
  other	
  species	
  may	
  wander	
  widely	
  (Hawes	
  

1977),	
  but	
  dispersal	
  in	
  this	
  species	
  unknown	
  and	
  

potentially	
  limited	
  by	
  mesic	
  environments.	
  Small	
  Sorex

generally	
  have	
  high	
  dispersal	
  abilities	
  and	
  colonization	
  

rates	
  (Taylor	
  1998).	
  Limited	
  information.	
  Dispersal	
  is	
  

possibly	
  sex	
  biased	
  and	
  limited	
  by	
  patchiness	
  of	
  mesic	
  

habitats.

1

7.	
  	
  Migratory	
  or	
  

transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

No.

0
USDA Forest Service RMRS-GTR-302. 2013. 141

Physiology:	
  Arizona	
  Shrew	
  (Sorex	
  arizonae)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Soricines	
  (Soricidae)	
  are	
  thought	
  to	
  have	
  low	
  tolerance	
  

for	
  high	
  ambient	
  temperatures	
  (Taylor	
  1998).	
  Shrews	
  

generally	
  have	
  high	
  body	
  temperatures	
  and	
  low	
  critical	
  

thresholds.	
  Likely	
  to	
  be	
  exceeded	
  in	
  these	
  habitats	
  where	
  

temperatures	
  are	
  already	
  high.

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.

0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Desert	
  shrew	
  uses	
  torpor	
  to	
  escape	
  physiological	
  

extremes,	
  but	
  torpor	
  is	
  unknown	
  for	
  this	
  species	
  and	
  

generally	
  not	
  seen	
  in	
  Soricidae.	
  Buffered	
  from	
  extremes	
  

to	
  some	
  extent	
  by	
  use	
  of	
  mesic	
  and	
  fossorial	
  habitats. 0

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Desert	
  shrew	
  stores	
  paralyzed	
  insects	
  in	
  food	
  caches,	
  but	
  

only	
  in	
  the	
  short	
  term	
  (BISON-­‐M).	
  No	
  flexible	
  strategies.

1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Very	
  high	
  metabolic	
  requirements. 1

	
  	
  	
  	
  	
  	
  	
  Phenology:	
  Arizona	
  Shrew	
  (Sorex	
  arizonae)

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)?	
  

None	
  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?	
  

Breeds	
  in	
  the	
  spring,	
  but	
  unknown	
  resource	
  peaks.	
  

0
142 USDA Forest Service RMRS-GTR-302. 2013.

	
  	
  	
  	
  	
  	
  	
  Phenology:	
  Arizona	
  Shrew	
  (Sorex	
  arizonae)

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?

Active	
  throughout	
  the	
  year	
  (NatureServe	
  2009).	
  No	
  large	
  

separation	
  between	
  events	
  and	
  cues.

0

4.	
  Resilience	
  to	
  

timing	
  

mismatches	
  

during	
  

breeding

Is	
  reproduction	
  in	
  this	
  

species	
  more	
  likely	
  to	
  

co-­‐occur	
  with	
  

important	
  events?

No	
  information,	
  but	
  likely	
  to	
  have	
  one	
  breeding	
  event	
  per	
  

year.

1

Biotic	
  Interactions:	
  Arizona	
  Shrew	
  (Sorex	
  arizonae)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Shrews	
  eat	
  insects,	
  spiders,	
  and	
  other	
  invertebrates	
  

(BISON-­‐M).	
  No	
  overall	
  changes	
  in	
  invertebrates	
  are	
  

expected. 0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Likely	
  various.	
  No	
  overall	
  changes	
  in	
  predation	
  levels	
  are	
  

anticipated. 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
USDA Forest Service RMRS-GTR-302. 2013. 143

Literature Cited

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

BISON-M. Biotic Information System of New Mexico. New Mexico Game and Fish Department. Available online 

from 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. 

Hawes, M. L. 1977. Home range, territoriality and ecological separation in sympatric shrews, Sorex vagrans

and Sorex obscurus. Journal of Mammalogy. 58:354–367.

Kelly, A. and M. Goulden. 2008. Rapid shifts in plant distribution with recent climate change. Proceedings of 

the National Academy of Sciences 105:11823–11826.

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.

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. Available http://www.natureserve.org/explorer. (Accessed: June 17, 2010).

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.

Seager, R., M. Ting, 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.

Simons, L. H., R. C. Szaro and S. C. Belfit. 1990. Distribution of Notiosorex crawfordi and Sorex arizonae along 

an Elevational Gradient. Journal of Mammalogy 71:634–640.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

Stromberg, J., S. J. Lite, T. J. Rychener, L. R. Levick, M. D. Dixon, J. M. 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.

Taylor, J. R. E. 1998. Evolution of energetic strategies in shrews. In Evolution of Shrews, J. M.Wojcik and M. 

Wolsan, eds. Mammal Research Institute, Poland.

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

role of ecophysiology. Biological Invasions 2:123–140.
144 USDA Forest Service RMRS-GTR-302. 2013.

Cave Myotis (Myotis velifer)

SUMMARY

Vulnerability of this species to declining populations is increased by expected effects of climate change. 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, so eventual outcome in the future is unknown and periodic monitoring is recommended. Roosts and 

open water sources are important elements for this species that could be affected and should be considered 

in management planning.

Introduction

Cave myotis is a Federal species of concern (since 1994) and a species at risk (SWESA 2006) that occurs on Fort 

Huachuca. The USDA Forest Service also identifies it as sensitive. Despite being widespread, this species is 

threatened locally, particularly in western portions of its range. 

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

• 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 document.

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

-5 0 5 

VULNERABILITY Score Uncertainty

Habitat -1.1 14%

Physiology -0.2 33%

Phenology 3.8 25%

Interactions 1.0 60%

Overall 2.2 32%
USDA Forest Service RMRS-GTR-302. 2013. 145

Other Threats and Interactions With Climate

Patchy distribution of this species may be due to its reliance on caves, which are geographically limited. Recent 

population declines in cave myotis are thought to be related to local habitat loss (BISON-M). Additionally, cave 

myotis, like many other bats, is vulnerable to disturbance at roosts, especially maternity roosts. 

Research Needs

More information on suitable roost sites at a local level is needed as these features affect species’ presence. 

The threat of white-nosed fungus for Arizona bats will be important to the species overall, but this disease 

has, thus far, not been detected in Arizona. This disease is associated with cool temperatures and may 

threaten higher elevation sites on Fort Huachuca, but almost all aspects of this disease need more study. 

Importance of various foraging habitats is not well known, thus critical habitat elements are difficult to assess. 

Response of populations to drought conditions will be critical to predicting climate change effects and have 

not been studied in this species.

Management Implications

Most cave myotis winter outside of Arizona, and their affinity for cool, moist hibernacula is unlikely to increase 

winter presence at Fort Huachuca in the future. Maternity roosts may become more limited and suitability 

of current roosts may be altered over time. Potential roost sites should be checked periodically for species 

presence. Some monitoring of populations is warranted, as identified phenological vulnerability will have an 

uncertain outcome on populations because interactions of bats with critical 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 likelihood of population changes on Fort Huachuca and other parts of Arizona.
146 USDA Forest Service RMRS-GTR-302. 2013.

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	
  has	
  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	
  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
USDA Forest Service RMRS-GTR-302. 2013. 147

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	
  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).

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
148 USDA Forest Service RMRS-GTR-302. 2013.

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	
  vulnerable	
  similarly	
  to	
  cave	
  

myotis.

0
USDA Forest Service RMRS-GTR-302. 2013. 149

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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

BISON-M. Biotic Information System of New Mexico. New Mexico Game and Fish Department. Available 

online from 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. 

Hoffmeister, D. F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish Dept. 

602 pp.

Kelly, A. and M. Goulden. 2008. Rapid shifts in plant distribution with recent climate change. Proc Natl Acad 

Sci USA 105:11823–11826.

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. Global Environmental 

Change 1:351–364. 

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. Available http://www.natureserve.org/explorer. (Accessed: December 2, 

2009).

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.

Seager, R., M. Ting, 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.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

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

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

role of ecophysiology. Biological Invasions 2:123–140.
150 USDA Forest Service RMRS-GTR-302. 2013.

Lesser Long-nosed Bat 

(Leptonycteris yerbabuenae)

SUMMARY

Lesser long-nosed bats were assessed to have moderate vulnerability to declines related to global climate 

change. Vulnerability is increased by their 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. Current critical threats of roost disturbance and loss of foraging habitats may increase through growing international border activity and the 

interactive effects of fire occurrence and non-native invasive grasses. Additionally, changes in the timing of bat 

presence on Fort Huachuca should be anticipated and integrated into planning.

Introduction

Lesser long-nosed bats were listed in 1988 as endangered under the subspecies Leptonycteris curasoae 

yerbabuenae. Originally, they were listed as Leptonycteris sanborni (Sanborn’s bat) but were also sometimes 

identified as Leptonycteris curasoae. Lesser long-nosed bats inhabit the desert scrub habitats in Arizona and 

northwestern Mexico and are nectarivorous, closely associated with paniculate agaves and columnar cactus. 

Agaves on Fort Huachuca are primarily Palmer’s agave (Agave palmeri) with some Parry’s agave (Agave 

parryi).

Numbers of lesser long-nosed bats have increased in recent years or may not have been as low as reported 

when first listed. Only three maternity roosts and approximately 40 roosts overall are known in the United 

States (USFWS 2005). 

The five-year review by the 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. Occurrence of two female demes complicates population dynamics and species requirements (USFWS 

2005). In this account, we focus on the migratory group that lives from Arizona south to southern Sonora. 

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

-5 0 5 

VULNERABILITY Score Uncertainty

Habitat 0.5 0%

Physiology 0.7 33%

Phenology 0.8 0%

Interactions 1.0 0%

Overall 3.1 9%
USDA Forest Service RMRS-GTR-302. 2013. 151

Lesser long-nosed bats arrive in late summer at Fort Huachuca, Arizona, after giving birth and before 

continuing their migration south. Bats in this region may arrive from maternity roosts in western Arizona and/

or travel north from the Sierra Madre Occidental (Fleming and Nassar 2001). Over the past 10 years, lesser 

long-nosed bats have increased on Fort Huachuca from a few hundred to more than 14,000 (USFWS 2005). 

While some increases in numbers have been attributed to counting methodologies and newly discovered 

roosts, increases at the Fort are thought to represent population increases or at least increased use of known 

roosts on the Fort (USFWS 2005). 

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Upward shifts of montane plants (Kelly and Goulden 2008, Lenoir and others 2008)

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

• Warmer temperatures and decreased soil moisture in Mexico (Liverman and O’Brien 1991)

• CAM plants (succulents, 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

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 (USFWS 2005). Urban 

development, wind farms, and changing fire regimes are additional threats that have yet to be addressed 

as part of recovery planning. Climate change impacts were not specifically addressed in the five-year review 

(USFWS 2005).

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 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 threats to roosts. 

Lesser long-nosed bats use clumped concentrations of agaves rather than isolated individuals (Ober and 

Steidl 2004). Changing climate may allow expansion of agaves into new areas, although it is not expected 

that increasing temperatures will reduce current agave populations as they are well suited to survival 

under dry and hot conditions. Nectar availability, however, may be affected. The greatest threat to bat 

foraging areas at a landscape level is the likely expansion of invasive grasses and the concurrent increase in 
152 USDA Forest Service RMRS-GTR-302. 2013.

fire occurrence followed by subsequent reduction in agaves and cacti. Buffelgrass (Pennisetum ciliare), in 

addition to the already common Lehmann’s lovegrass (Eragrostis lehmanniana), is rapidly expanding and 

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). 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. 

Climate change has the potential to create timing mismatches between species and resources. A number 

of observations and studies have found there is currently 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 for earlier bat arrival, although advancement 

of blooming may be problematic if bat migration cannot advance equally (see Table A1). Observations of 

bat arrival and flowering timing, however, are limited and generally only over short time periods, so it is 

reasonable to assume annual variability in arrival, flowering, and, therefore, synchrony of these events. 

Elevational variation at the Fort may lengthen availability of blooming agave so the Fort may be a relatively 

small but important foraging site (ENRD 2006). 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 Fort Huachuca. Migratory and non-migratory demes probably make the 

species more resilient as a whole to flowering variability. More critical to populations is failure of flowering, 

particularly if synchronous across range. In one study, monsoons were found to be generally asynchronous 

between northern Mexico and the Southwest (Comrie and Glenn 1998), thus adequate flowering 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). It is also possible that 

there was greater synchronicity between bats and flowering in the past.

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 bats. 

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 bats were identified in the five-year review 

(USFWS 2005). These include 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. 

This assessment of vulnerability to climate change indicates additional research needs. 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, Fort Huachuca. In addition, little is known about how climate variability may 

affect flowering variability particularly across latitudes where the bat occurs and how flowering variables 

relate to survival. Studies of the interaction of warming climate, fire, and expansion of invasive grasses would 

help identify effective management actions. Information is also needed on bat mortality and wind turbines. 

Research on management options that reduce populations of African grasses and probability of spread is 

needed.
USDA Forest Service RMRS-GTR-302. 2013. 153

Management Implications

Because lesser long-nosed bats only spend a portion of the year on Fort Huachuca, factors that affect 

populations occur largely in other regions, including Mexico, and effects from military activities will be limited. 

Fort Huachuca has already undertaken important steps to protect roosting and foraging resources. The Fort 

Huachuca Agave Management Plan includes established areas for agave management and a monitoring 

program. Agave management should include a range of elevations to incur greater resiliency of flowering 

resources under climate change. The potential for increasing impacts from invasive African grasses and 

increasing fires warrants consideration in management planning and implementation of preventative actions. 

Management related to post-fire rehabilitation should also include actions that encourage agaves. 

Current activity restrictions to protect bats are in place from July 1 to October 31 (ENRD 2006). To protect 

bats, the Fort also has seasonal closing of mines and caves. Although this time period includes a buffer to 

known dates of bat presence, Fort Huachuca needs to anticipate timing changes in bat arrival and reevaluate 

time restrictions on activities that may disturb bats in the future. 
154 USDA Forest Service RMRS-GTR-302. 2013.

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	
  desert	
  scrub	
  

habitats	
  (primarily	
  Sonoran,	
  but	
  also	
  Chihuahuan)	
  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	
  there	
  are	
  

other	
  important	
  issues	
  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.	
  Some	
  evidence	
  for	
  

expansion	
  of	
  suitable	
  areas,	
  but	
  other	
  factors	
  such	
  as	
  fire,	
  

invasives,	
  and	
  human	
  developments	
  likely	
  to	
  limit	
  

expansion	
  and	
  threaten	
  current	
  range.

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?

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.	
  

Individuals	
  require	
  multiple	
  roost	
  types	
  at	
  different	
  

locations.	
  A	
  large	
  maternity	
  roost	
  is	
  located	
  

approximately	
  240	
  km	
  (150	
  miles)	
  from	
  the	
  Fort	
  in	
  

Organ	
  Pipe	
  Cactus	
  National	
  Monument	
  (ENRD	
  2006).	
  

Maternity	
  roosts	
  do	
  not	
  occur	
  on	
  Fort	
  Huachuca.	
  Use	
  

roosts	
  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.	
  Important	
  day	
  and	
  night	
  roosts	
  have	
  been	
  

identified	
  on	
  Fort	
  Huachuca,	
  although	
  there	
  are	
  likely	
  

unknown	
  roost	
  sites	
  as	
  well	
  (ENRD	
  2006).	
  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
USDA Forest Service RMRS-GTR-302. 2013. 155

Habitat:	
  Lesser	
  Long-­nosed	
  Bat	
  (Leptonycteris	
  yerbabuenae)

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?

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).	
  Individuals	
  follow	
  progressive	
  

flowering	
  of	
  columnar	
  cactus	
  and	
  paniculate	
  agaves.	
  

Although	
  highly	
  mobile,	
  they	
  avoid	
  crossing	
  high	
  density	
  

urban	
  housing	
  (USFWS	
  2005).

1

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	
  the	
  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.	
  Flood	
  risk	
  at	
  Fort	
  Huachuca	
  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?

They	
  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	
  individuals	
  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	
  

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	
  

1
156 USDA Forest Service RMRS-GTR-302. 2013.

Physiology:	
  Lesser	
  Long-­nosed	
  Bat	
  (Leptonycteris	
  yerbabuenae)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

multiple	
  years? non-­‐migratory	
  demes	
  related	
  to	
  resource	
  availability	
  and	
  

likely	
  helpful	
  with	
  fluctuating	
  resources.	
  All	
  individuals	
  at	
  

Fort	
  Huachuca,	
  however,	
  are	
  migratory,	
  so	
  these	
  

populations	
  do	
  not	
  possess	
  this	
  alternative	
  and	
  plasticity	
  

in	
  behavior	
  within	
  demes	
  is	
  unknown.

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic.

0

	
  	
  	
  	
  	
  	
  	
  	
  	
  

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	
  initiates	
  migration	
  based	
  on	
  

flowering	
  resources,	
  but	
  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	
  1	
  young	
  that	
  can	
  fly	
  at	
  about	
  4	
  weeks.	
  	
  Birth	
  is	
  not	
  

highly	
  synchronous	
  among	
  individuals	
  at	
  the	
  same	
  

maternity	
  cave,	
  with	
  pregnant	
  females	
  co-­‐occurring	
  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,	
  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
USDA Forest Service RMRS-GTR-302. 2013. 157

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	
  and	
  

also	
  may	
  eat	
  insects,	
  fruits,	
  and	
  have	
  been	
  observed	
  to	
  

use	
  hummingbird	
  feeders	
  (USFWS	
  2005).	
  Northern	
  

migrants	
  eat	
  almost	
  exclusively	
  CAM	
  plants	
  (agaves	
  and	
  

cactus).	
  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).	
  Agaves	
  on	
  Fort	
  Huachuca	
  are	
  primarily	
  

Palmer’s	
  agave	
  (Agave	
  palmeri)	
  with	
  some	
  Parry’s	
  agave	
  

(Agave	
  parryi).	
  Mostly	
  dependent	
  on	
  agave	
  at	
  Fort	
  

Huachuca.	
  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

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).	
  Potentially	
  large	
  impacts	
  of	
  

single	
  predators	
  at	
  small	
  roosts,	
  but	
  overall,	
  probably	
  has	
  

little	
  impact	
  on	
  populations.

0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

They	
  are	
  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	
  cactus	
  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	
  

0
158 USDA Forest Service RMRS-GTR-302. 2013.

Biotic	
  Interactions:	
  Lesser	
  Long-­nosed	
  Bat	
  (Leptonycteris	
  yerbabuenae)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

smaller	
  (e.g.,	
  moths,	
  birds)	
  so	
  probably	
  little	
  competition.	
  

Could	
  be	
  competition	
  with	
  other	
  nectarivorous	
  bats,	
  but	
  

Mexican	
  long-­‐tongued	
  bats	
  probably	
  exploits	
  additional	
  

flower	
  resources	
  with	
  its	
  longer	
  tongue.	
  Expected	
  to	
  be	
  

similarly	
  affected	
  by	
  climate	
  change.
USDA Forest Service RMRS-GTR-302. 2013. 159

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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. 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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Beatty, L. D. 1955. Autecology of the longnose bat, Leptonycteris nivalis (Saussure). Unpublished M.S. thesis, 

University of Arizona, Tucson. (primary document unavailable; as referenced in Scott 2004).

Blehert, David S., Alan C. Hicks, Melissa Behr, Carol U. Meteyer, Brenda M. Berlowski-Zier, Elizabeth L. Buckles. 

2008. Bat white-nose syndrome: an emerging fungal pathogen? Sciencexpress. Published online 30 October 

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.

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

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

6:16–17.

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.

Gillette, D. D., and J. D. Kimbrough. 1970. Chiropteran Mortality. In About Bats, B. Slaugher and D. Walton, 

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

Change 1:351–364. 

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

climate change impact studies, Eos Transactions, American Geophysical Union 88:504.

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 pp.

Rehfeldt, G. E., N. L. Crookston, M. V. Warwell, J.S. Evans. 2006. Empirical analyses of plant-climate 

relationships for the western United States. International Journal of Plant Sciences 167:1123–1150.

Robinett, D. 1994. Fire effects on southeastern Arizona plains grasslands. Rangelands 16:143–148.

Rojas-Martinez, Alberto, Alfonso Valiente-Banuet, Maria del Coro Arizmendi, Ariel Alcantara-Eguren, and 

Hector 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 

Chiricahua Mountains. Southwestern Naturalist 49:425–434.

Seager, R., M. Ting, 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.

Smith, S. D., B. Didden-Zopfy and P. S. Nobel. 1984. High-Temperature Responses of North American Cacti. 

Ecology 65:643–651.

USFWS (United States Fish and Wildlife Service). 2005. Lesser long-nosed bat five year review: summary and 

evaluation. Arizona Ecological Service Office, Tucson, AZ.

USFWS (United States Fish and Wildlife Service). 1995. Recovery Plan for the Lesser Long-nosed Bat, 

Leptonycteris curasoae yerbabuenae. U.S. Fish and Wildlife Service, Albuquerque, New Mexico. 45 pp.

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 2:123–140.
USDA Forest Service RMRS-GTR-302. 2013. 161

Mexican Long-tongued Bat 

(Choeronycteris mexicana)

SUMMARY

Populations of Mexican long-tongued bats that currently occur in Arizona are females migrating to maternity 

colonies. Like the lesser-long nosed bat, this species is expected to be vulnerable to changes in temperatures 

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.

Introduction

Mexican long-tongued bat is a USFWS species of concern, Forest Service sensitive species, and a species of 

greatest conservation need, Tier 1C, in Arizona SWAP (2010). It is also designated as a species at risk (SWESA 

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 as well (Balin 2009). These 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 longnosed bat, this species is nectivarous and migrates from U.S. locations to Mexico where it is generally resident 

year-round. This species is present at Fort Huachuca.

Fort Huachuca Climate and Projections

• Annual increase in temperature 2.5-4.5 °F by 2050 (www.climatewizard.org, A2 emissions, ensemble GCM) 

and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• Reductions in Madrean woodlands (Rehfeldt and others 2006)

• 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 

4

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat 1.3 14%

Physiology 0.7 67%

Phenology 0.8 0%

Interactions 1.0 20%

Overall 4.1 27%
162 USDA Forest Service RMRS-GTR-302. 2013.

• CAM plants (succulents, 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

Many historic locations for this species remain occupied in Arizona, including various locations in the Huachuca 

Mountains (Cryan and Bogan 2003). Thus, although rare, populations in Arizona may be relatively stable. 

Mexican long-tongued bats, however, are threatened by a number of factors that we expect to be exacerbated 

by future climate change.

Like most bats, Mexican long-tongued bats are vulnerable to roost disturbance (NatureServe 2009). Roost 

protection is complicated by disturbance at roost sites. It is unknown if they are sensitive to gate construction 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 and, subsequently, an increase in threats to roosts. 

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 Lehmann’s lovegrass (Eragrostis lehmanniana), 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 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. 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 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 it is assumed 

that this species may use a broader selection 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

The potential for increasing impacts from invasive African grasses and increasing fires warrants consideration 

in management planning and implementation of preventative actions. Management related to post-fire 

rehabilitation should also include actions that encourage agaves and cacti in suitable areas. 

Fort Huachuca has taken a number of measures to protect bats, including protecting agave in Agave 

Management Areas and seasonal closure of mines and caves. Although these primarily target the endangered 

lesser long-nosed bat, the Mexican long-tongued bat also benefits. Timing changes in bat arrival and presence 

at Fort Huachuca related to climate change indicate a need to reevaluate time restrictions on activities that may 

disturb bats. In addition, identification and monitoring of suitable caves or mines is warranted as conditions 

become more favorable for these bats.
USDA Forest Service RMRS-GTR-302. 2013. 163

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	
  bats	
  breed	
  

along	
  the	
  border	
  region	
  with	
  Mexico.	
  In	
  Arizona,	
  this	
  

species	
  to	
  inhabit	
  primarily	
  the	
  oak-­‐pine	
  belt	
  at	
  

elevations	
  ranging	
  from	
  4000–6000	
  ft	
  as	
  well	
  as	
  saguaro-­‐

paloverde	
  desertscrub	
  (BISON-­‐M).	
  Additionally,	
  they	
  are	
  

often	
  associated	
  with	
  Madrean	
  evergreen	
  woodlands	
  and	
  

semidesert	
  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,	
  if	
  

not	
  all,	
  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).	
  Also	
  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	
  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	
  2009).	
  Roosts	
  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
164 USDA Forest Service RMRS-GTR-302. 2013.

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?

Range	
  extends	
  from	
  southern	
  California,	
  Arizona,	
  and	
  

southwestern	
  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	
  though	
  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.	
  Flood	
  risk	
  at	
  Fort	
  

Huachuca	
  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.	
  Rest	
  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	
  currently	
  

migratory	
  and	
  it	
  is	
  not	
  known	
  if	
  they	
  would	
  not	
  migrate	
  

should	
  flowering	
  fail.	
  Possible,	
  but	
  too	
  little	
  information.

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.	
  Do	
  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
USDA Forest Service RMRS-GTR-302. 2013. 165

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	
  2009).	
  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	
  2009).	
  In	
  Arizona,	
  large	
  

numbers	
  of	
  bats	
  are	
  thought	
  to	
  rely	
  on	
  hummingbird	
  

feeders	
  before	
  and	
  after	
  agave	
  flowering	
  season	
  (BISON-­‐

M	
  2009).	
  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	
  expected	
  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, but,	
  

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,	
  birds),	
  so	
  

probably	
  little	
  competition.	
  Could	
  be	
  competition	
  with	
  

other	
  bats,	
  but	
  Mexican	
  long-­‐tongued	
  bat	
  probably	
  

exploits	
  additional	
  flower	
  resources	
  with	
  its	
  longer	
  

tongue.	
  Expected	
  to	
  be	
  similarly	
  affected	
  by	
  climate	
  

change.

0
166 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

Balin, 2009. Mexican Long-tongued bat (Choeronycteris mexicana) in El Paso, Texas. Southwestern Naturalist 

54:225–226.

BISON-M. 2009. Biotic Information System of New Mexico. New Mexico Game and Fish Department. Available 

online from http://www.bison-m.org.

Blehert, David S., Alan C. Hicks, Melissa Behr, Carol U. Meteyer, Brenda M. Berlowski-Zier, Elizabeth L. Buckles. 

2008. Bat White-Nose Syndrome: An Emerging Fungal Pathogen? SciencExpress. Published online 30 

October 2008; 10.1123/science.11638.

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 Bogan, M. A. 2003. Recurrence of Mexican long-tongued bats (Choeronycteris mexicana) at 

historical sites in Arizona and New Mexico. Western North American Naturalist. Vol. 63:314–319. 

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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, IL.

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 About Bats (B. Slaugher and D. Walton, 

eds.). 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., 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. Global Environmental 

Change 1:351–364. 

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. Available http://www.natureserve.org/explorer. (Accessed: July 12, 2010).

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.

Robinett, D. 1994. Fire effects on southeastern Arizona Plains grasslands. Rangelands 16:143–148.

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

climate in southwestern North America. Science, 316:1181–1184.
USDA Forest Service RMRS-GTR-302. 2013. 167

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

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.

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

role of ecophysiology. Biological Invasions 2:123–140.
168 USDA Forest Service RMRS-GTR-302. 2013.

Black-tailed Prairie Dog 

(Cynomys ludovicianus)

SUMMARY

Potential habitat exists on Fort Huachuca for this keystone species. Plague is considered to be the greatest 

current impact, and plague prevalence will likely be altered by climate change, but ultimate outcome for 

mortality rate in prairie dogs is unclear. Based on a broad suite of traits, we predict that prairie dog response 

to climate change will be somewhat resilient overall, thus population dynamics will largely depend on other 

factors. Potential for dispersal to Fort Huachuca should be evaluated.

Introduction

USFWS found that listing of the black-tailed prairie dog as threatened or endangered was unwarranted 

and that the proposed Arizona black-tailed prairie dog (Cynomys ludovicianus arizonensis) is not a distinct 

population or subspecies (Dec. 2009). Other analyses identified the arizonenis populations as a unique 

subspecies (BISON-M 2009). In 1960, the black-tailed prairie dog was considered extirpated in Arizona 

(ENRD 2006), but it was reintroduced to Arizona in 2008 via translocations. Reintroductions in and adjacent 

to Las Cienegas National Conservation Area began in 2008. USFWS included climate change as a potential 

threat when considering listing status and concluded that climate change does not threaten the species with 

extinction in the foreseeable future. Black-tailed prairie dogs are a species of greatest conservation need, Tier 

1A, in Arizona SWAP (AGFD 2006) and a species at risk (SWESA 2006). Fort Huachuca has potential habitat for 

this species (ENRD 2006).

Fort Huachuca Climate and Projections

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

GCM) and greater evaporation

• 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)

• Riparian habitats decline (Stromberg and others 2006, Serrat-Capdevila and others 2007)

• Grasses favored over shrubs (Esser 1992)

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

• CAM plants (succulents, cacti) will be resilient to increasing temperatures (Smith and others 1984)

-5 0 5 

Figure Key

Habitat

Physiology

Phenology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient

VULNERABILITY Score Uncertainty

Habitat -2.5 0%

Physiology -1.0 33%

Phenology 2.5 25%

Interactions 0.0 40%

Overall -2.4 23%
USDA Forest Service RMRS-GTR-302. 2013. 169

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

Prairie dogs have been widely poisoned and shot for interference with livestock, but sylvatic plague is 

considered to be the most important current impact (USFWS 2009). Spread of plague could be exacerbated 

by climate change (USFWS 2009). Plague is enhanced by cooler summer temperatures and by increased 

precipitation. Consequently, the extent to which plague may shift due to climate change versus expand 

or contract is unclear (USFWS 2009). Extinction of colonies generally follows ENSO events, but colony 

metapopulation dynamics are complex (Stapp and others 2004). Warmer and wetter winters may contribute 

to flea vector populations and also winter survival in prairie dogs, thus increasing the chances of transmission 

(Stapp and others 2004). In the Southwest, human plague outbreaks are higher during periods of higher 

rainfall but decrease with high summer temperatures (Parmenter and others 1999). 

Population declines in the Southwest have partly been attributed to the conversion of grasslands to 

shrublands (USFWS 2009). Climate change will have important interactions with grass and shrub species and 

may favor grasses in the Southwest. Incidence of fires and current vegetation will also be influential in future 

vegetation projections.

Research Needs

More complex analysis is needed to evaluate how plague and climate change interact with particular attention 

to regional differences. Plague interactions in Arizona may be quite different from those in the Midwest. In 

general, most studies on this species are from cooler climates; therefore, more specific information on habitat 

and population dynamics for the Southwest are needed.

Management Implications

Black-tailed prairie dog is not of current management concern for Fort Huachuca. We expect that climate 

change will not greatly impact this species. If other impacts are low enough to allow reintroduced populations 

to increase, there could be expansion of prairie dog towns. Dispersal onto Fort Huachuca will depend on a 

number of factors including dispersal barriers and land ownership. An evaluation of this potential would be 

useful in determining if prairie dogs need to be included in future planning documents.
170 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Black-­tailed	
  Prairie	
  Dog	
  (Cynomys	
  ludovicianus)

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	
  grasslands	
  with	
  flat	
  or	
  gently	
  sloped	
  

topography	
  (USWFS	
  2009).	
  In	
  Arizona,	
  occupies	
  desert	
  

grasslands	
  (BISON-­‐M	
  2009).	
  Desert	
  grasslands	
  in	
  

southwestern	
  United	
  States	
  are	
  probably	
  encouraged	
  by	
  

warmer	
  temperatures	
  and	
  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?	
  

Burrows	
  are	
  required	
  and	
  created	
  by	
  prairie	
  dogs.	
  No	
  

change	
  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?	
  

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?	
  

Shorter	
  and	
  less	
  dense	
  vegetation	
  is	
  generally	
  associated	
  

with	
  greater	
  predator	
  avoidance	
  in	
  prairie	
  dogs.	
  Although	
  

vegetation	
  height	
  will	
  be	
  more	
  variable	
  with	
  increasing	
  

variability	
  in	
  rainfall,	
  prairie	
  dogs	
  also	
  actively	
  clip	
  

vegetation.	
  No	
  effect	
  anticipated.	
  

0

6.	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  the	
  potential	
  

for	
  this	
  species	
  to	
  

disperse?

Known	
  to	
  disperse	
  long	
  distances	
  to	
  establish	
  new	
  

colonies	
  although	
  most	
  dispersal	
  is	
  between	
  colonies.	
  

Dispersal	
  rates	
  are	
  considered	
  generally	
  low	
  and	
  may	
  

contribute	
  to	
  interpopulation	
  genetic	
  variation	
  (Chesser	
  

1983).	
  May	
  expand	
  foraging	
  area	
  during	
  drought	
  (USFWS	
  

2009).

Dispersal	
  abilities	
  can	
  likely	
  keep	
  up	
  with	
  habitat	
  shifts.

-­1

7.	
  	
  Migratory	
  or	
  

transitional	
  

habitats

Does	
  this	
  species	
  

require	
  additional	
  

habitats	
  during	
  

migration	
  that	
  are	
  

separated	
  from	
  

breeding	
  and	
  non-­‐

breeding	
  habitats?

No.

0
USDA Forest Service RMRS-GTR-302. 2013. 171

Physiology:	
  Black-­tailed	
  Prairie	
  Dog	
  (Cynomys	
  ludovicianus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Physiological	
  

thresholds

Are	
  limiting	
  

physiological	
  

conditions	
  expected	
  to	
  

change?

Tolerant	
  of	
  a	
  wide	
  variety	
  of	
  conditions	
  including	
  hot	
  

daytime	
  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?	
  

None	
  known	
  and	
  generally	
  avoid	
  areas	
  prone	
  to	
  flooding.	
  

Fires	
  probably	
  do	
  not	
  result	
  in	
  direct	
  mortality.	
  Drought	
  

not	
  thought	
  to	
  be	
  a	
  limiting	
  factor	
  (USFWS	
  2009).	
   0

4.	
  Limitations	
  

to	
  daily	
  activity	
  

period

Are	
  projected	
  

temperature	
  or	
  

precipitation	
  regimes	
  

that	
  influence	
  activity	
  

period	
  of	
  species	
  

expected	
  to	
  change?

Less	
  active	
  in	
  summer	
  than	
  winter	
  (Tileston	
  and	
  

Lechleitner	
  1966),	
  but	
  no	
  known	
  effect	
  on	
  fitness.	
  

Although	
  this	
  species	
  may	
  avoid	
  the	
  hottest	
  parts	
  of	
  the	
  

day	
  in	
  burrows,	
  no	
  information	
  that	
  activity	
  periods	
  are	
  

limited.

0

5.	
  Survival	
  

during	
  resource	
  

fluctuation

Does	
  this	
  species	
  have	
  

flexible	
  strategies	
  to	
  

cope	
  with	
  variation	
  in	
  

resources	
  across	
  

multiple	
  years?

Facultative	
  torpor	
  has	
  been	
  observed	
  in	
  this	
  species	
  and	
  

was	
  associated	
  with	
  sudden	
  drops	
  in	
  ambient	
  

temperatures	
  but	
  not	
  precipitation	
  (Lehmer	
  and	
  others

2001).	
  Colonial	
  habits	
  and	
  flexibility	
  may	
  help	
  

populations	
  cope	
  with	
  resource	
  fluctuations.

-­1

6.	
  Metabolic	
  

rates	
  

What	
  is	
  this	
  species	
  

metabolic	
  rate?

Moderate	
  endothermic. 0

	
  	
  	
  	
  	
  	
  	
  	
  	
  

Phenology:	
  Black-­tailed	
  Prairie	
  Dog	
  (Cynomys	
  ludovicianus)

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	
  

factors.	
  Arizona	
  populations	
  do	
  not	
  go	
  through	
  

hibernation.

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	
  Colorado,	
  young	
  were	
  born	
  in	
  late	
  March	
  through	
  early	
  

April	
  (Tileston	
  and	
  Lechleitner	
  1966).

Breeding	
  in	
  the	
  spring	
  may	
  be	
  timed	
  with	
  new	
  growth	
  of	
  

vegetation.	
  Timing	
  of	
  new	
  growth	
  is	
  likely	
  to	
  change. 1
172 USDA Forest Service RMRS-GTR-302. 2013.

Phenology:	
  Black-­tailed	
  Prairie	
  Dog	
  (Cynomys	
  ludovicianus)

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?

Cues	
  not	
  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	
  litter	
  per	
  year.

1

Biotic	
  Interactions:	
  Black-­tailed	
  Prairie	
  Dog	
  (Cynomys	
  ludovicianus)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Food	
  

resources

Are	
  important	
  food	
  

resources	
  for	
  this	
  

species	
  expected	
  to	
  

change?

Eats	
  grasses	
  and	
  forbs.	
  Also	
  consumes	
  roots	
  (Tileston	
  and	
  

Lechleitner	
  1966).	
  Prefers	
  grass	
  species	
  in	
  desert	
  

grasslands	
  (BISON-­‐M	
  2009).	
  Food	
  preferences	
  vary	
  with	
  

phenology	
  and	
  diet	
  is	
  considered	
  specialized	
  opportunist	
  

(USFWS	
  1989).	
  Seeds,	
  woody	
  stems,	
  and	
  cactus	
  are	
  eaten	
  

in	
  winter	
  (USFWS	
  1989).	
  Variety	
  will	
  likely	
  result	
  in	
  no	
  

overall	
  change	
  in	
  quantity.

0

2.	
  Predators Are	
  important	
  

predator	
  populations	
  

expected	
  to	
  change?

Large	
  number	
  of	
  predator	
  species.	
  Major	
  predators	
  in	
  

Arizona	
  are	
  not	
  known.	
  Unlikely	
  to	
  change	
  overall. 0

3.	
  Symbionts Are	
  populations	
  of	
  

symbiotic	
  species	
  

expected	
  to	
  change?

Considered	
  a	
  keystone	
  species	
  but	
  is	
  not	
  dependent	
  on	
  

presence	
  of	
  other	
  species.	
  Interactions	
  with	
  other	
  prairie	
  

dogs	
  also	
  important.	
  Colonial	
  behavior	
  aids	
  predator	
  

detection,	
  rearing	
  of	
  young,	
  and	
  parasite	
  removal	
  (see	
  

Physiology	
  Question	
  5).	
  No	
  changes	
  in	
  colony	
  size	
  

predicted.	
  No	
  dependence	
  on	
  other	
  species.

0

4.	
  Disease	
   Is	
  prevalence	
  of	
  

diseases	
  known	
  to	
  

cause	
  widespread	
  

mortality	
  or	
  

reproductive	
  failure	
  in	
  

this	
  species	
  expected	
  

to	
  change?	
  

Plague	
  is	
  a	
  major	
  source	
  of	
  mortality	
  and	
  can	
  also	
  be	
  

transmitted	
  through	
  fleas	
  during	
  grooming	
  and	
  other	
  

contact.	
  Complex	
  interactions	
  with	
  climate	
  and	
  

metapopulations.	
  Could	
  increase	
  with	
  warmer	
  wetter	
  

winters,	
  but	
  precipitation	
  is	
  not	
  expected	
  to	
  increase	
  on	
  

average	
  and	
  hot	
  summers	
  are	
  associated	
  with	
  decreased	
  

incidence	
  of	
  plague.	
  Needs	
  more	
  complex	
  analysis.	
  No	
  

change	
  projected.

0

5.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Domestic	
  livestock	
  are	
  popularly	
  considered	
  competitors,	
  

but	
  livestock	
  grazing	
  may	
  also	
  favor	
  prairie	
  dogs	
  by	
  

reducing	
  vegetation	
  height	
  and	
  increasing	
  predator	
  

detection	
  (USFWS	
  2009).	
  Grazing	
  interactions	
  with	
  

domestic	
  or	
  native	
  species	
  is	
  limited	
  on	
  Fort	
  Huachuca.

0
USDA Forest Service RMRS-GTR-302. 2013. 173

Literature Cited

AGFD (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. 

Web-based version available at http://www.fs.fed.us/rm/grassland-shrubland-desert/products/speciesvulnerability/savs-climate-change-tool. 

BISON-M. 2009. Biotic Information System of New Mexico. New Mexico Game and Fish Department. Available 

online from http://www.bison-m.org.

Chesser, Ronald K. 1983. Genetic variability within and among populations of the black-tailed prairie dog. 

Evolution 37:320–331.

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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.

Garfin, G. and M. Lenart. 2007. Climate Change Effects on Southwest Water Resources. Southwest Hydrology 

6:16–17. 

Lehmer, E. M., B. Van Horne and G. L. Florant. 2001. Facultative torpor in free-ranging black-tailed prairie dogs 

(Cynomys lucovicianus). Journal of Mammalogy 82:551–557.

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.

Parmenter, R. R., E. P. Yadav, C.A. Parmenter, P. Ettestad, and K. L. Gage. 1999. Incidence of plague associated 

with increased winter-spring precipitation in New Mexico. American Journal of Tropical Medicine and 

Hygiene 61:814–821.

Seager, R., M. Ting, 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.

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

Ecology 65:643–651.

SWESA (Southwest Endangered Species Act Team). 2006. Species at Risk Report for New Mexico and Arizona. 

DoD Legacy Program Report. Available at http://www.fws.gov/southwest/es/arizona/Documents/

SWStrategy/FINAL%20SAR%20REPORT.pdf.

Stapp, P., M. F. Antolin, and M. Ball. 2004. Patterns of extinction in prairie dog metapopulations: plague 

outbreaks follow El Niño events. Frontiers in Ecology and the Environment 2: 235–240.

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

Tileston, J. V. and R. R. Lechleitner. 1966. Some comparisons of the black-tailed and white-tailed prairie dogs in 

north-central Colorado. American Midland Naturalist 75:292–316.

USFWS (United States Fish and Wildlife Service). 1989. Habitat Suitability Index Models: Black-tailed Prairie 

Dog. Biological Report 82.

USFWS (United States Fish and Wildlife Service). 2009. 12-Month Finding on a Petition to List the Black-tailed 

Prairie Dog as Threatened or Endangered. Federal Register 74(231).

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

role of ecophysiology. Biological Invasions 2:123–140.
174 USDA Forest Service RMRS-GTR-302. 2013.

Huachuca Water Umbel 

(Lilaeopsis schaffneriana var. recurva)

SUMMARY

The Huachuca water umbel is present only at locations that remain wet year round, thus is prone to future 

population declines as evaporation increases and precipitation patterns are altered. Flooding is important for 

dispersal, but also can threaten established populations. Similarly, fires can increase sedimentation but can 

also open canopy and increase surface water through run-off. Some intermediate level of disturbance is likely 

optimal for this species, although optimal levels may change as disturbance regimes are altered. Management 

related to hydrology and fire will be important with the biggest challenge being the retention of water in 

occupied wetlands.

Introduction

The Huachuca water umbel is a Federally endangered plant that has also been known as Lilaeopsis recurva. It 

is designated as sensitive by the USDA Forest Service and highly safeguarded under Arizona Native Plant Law 

(ENRD 2006). Huachuca water umbel occupies Garden Canyon and tributaries (ENRD 2006). Portions of this 

habitat are designated as critical (USFWS 1999). Some of these populations were identified after 1995 along 

with several populations outside of Fort Huachuca (ENRD 2006). It also occurs outside of the United States in 

northern Sonora, Mexico. 

Fort Huachuca Climate Projections Used for Assessment

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

GCM) and greater evaporation

• 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)

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 Change

The primary threat to the Huachuca water umbel is loss of water and degradation of wetlands (USFWS 1999). 

This threat will be intensified under warmer temperatures regardless of precipitation changes. High severity 

-3 0 3 

VULNERABILITY Score Uncertainty

Habitat 0.5 0%

Physiology 1.0 33%

Interactions 1.0 66%

Overall 2.8 30%

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient
USDA Forest Service RMRS-GTR-302. 2013. 175

wildfires, which are projected to increase, are likely to increase sedimentation, which negatively impacts 

habitat. Other sources of erosion such as recreation and flooding are also considered detrimental (ENRD 

2006). Flooding, however, is important for dispersal, thus the best habitats include locations that are both 

prone to floods and those that are refugia from floods (USFWS 1999). Irregular flood events may be beneficial 

to sustaining populations, although this will depend on a number of factors, including topography and flood 

intensity. This species should be resilient to changes in timing of floods.

Flowering may be reduced where cover of competing species is high, possibly from reduced light levels (Titus 

and Titus 2008). More open habitats, however, can dry out faster (Titus and Titus 2008) and dispersal seems 

to mostly be associated with flooding. 

Various activities are considered potentially detrimental to populations. The most important are those that 

reduce water for wetland habitats or otherwise alter or degrade wetland habitats or hydrology. Channelization 

also encourages unfavorable flooding (Titus and Titus 2008). Other potential threats include catastrophic fires, 

livestock grazing, logging, military activities, and recreation. Low to moderate severity fires may maintain 

suitable habitats by reducing competing canopy (Titus and Titus 2008), but, as previously noted, can also 

increase sedimentation. Fires may be additionally beneficial as run-off increases water inputs from burned 

upland areas, at least in the short term. The favorable environmental conditions of a more closed canopy will 

likely increase in importance with climate change. 

Research Needs

An assessment of future flood risk and potential impacts for Fort Huachuca would aid management of this 

species because it is associated with specific hydrological conditions and dispersal depends on flooding. 

Management Implications

Response to climate change in this species is difficult to project because of its complex relationship with 

flooding and other processes that remove vegetation, such as fire. Some balance of these disturbances is 

likely optimal, but detailed projections of fire and flooding are unavailable and depend on many factors. 

Management that affects hydrology and fire regimes will need to consider both the positive and negative 

influence of these activities. Planning should be in place for locations that are expected to dry to the point 

they are no longer suitable for this species. Inclusion of translocation options in planning may be warranted.
176 USDA Forest Service RMRS-GTR-302. 2013.

Habitat:	
  Huachuca	
  Water	
  Umbel	
  (Lilaeopsis	
  schaffneriana	
  var.	
  recurva)

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?

Occupies	
  cienegas	
  in	
  a	
  variety	
  of	
  arid	
  habitats	
  including	
  

grasslands,	
  desert	
  scrub,	
  oak	
  woodlands,	
  and	
  coniferous	
  

forests	
  (ENRD).	
  Locations	
  of	
  occurrence	
  have	
  permanent	
  

surface	
  water	
  or	
  are	
  seasonally	
  saturated	
  and	
  are	
  not	
  

prone	
  to	
  flooding	
  (USFWS	
  1999).	
  Current	
  elevational	
  

limits	
  are	
  855–2100 m	
  (2800–7000	
  ft)	
  (Titus	
  and	
  Titus	
  

2008).	
  

1

2.	
  Habitat	
  

elements

Does	
  this	
  species	
  

require	
  specialized	
  

microsites?

Also	
  needs	
  refugia	
  from	
  flooding	
  that	
  are	
  also	
  not	
  prone	
  

to	
  drying	
  and	
  a	
  moderately	
  open	
  canopy	
  (USFWS	
  1999).	
  

Flooding	
  will	
  likely	
  be	
  more	
  irregular	
  and	
  intense	
  while	
  

fires	
  will	
  become	
  more	
  frequent.	
  In	
  addition,	
  wetland	
  

areas	
  are	
  limited	
  in	
  the	
  region.

1

3	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  this	
  species	
  

dispersal	
  ability?

Perennial	
  species	
  with	
  creeping	
  rhizomes.	
  Reproduction	
  

can	
  be	
  sexual	
  through	
  flowers,	
  but	
  most	
  is	
  through	
  

asexual	
  through	
  spread	
  of	
  rhizomes	
  (USFWS	
  1999).	
  

Dispersal	
  can	
  also	
  occur	
  through	
  rooting	
  of	
  dislodged	
  

clumps	
  that	
  are	
  swept	
  downstream	
  (USFWS	
  1999).	
  Seeds	
  

are	
  buoyant	
  and	
  likely	
  dispersed	
  by	
  water	
  (Titus	
  and	
  

Titus	
  2008).

-­1

5.	
  Seedling	
  

conditions

Do	
  seedlings	
  require	
  

different	
  conditions	
  

from	
  mature	
  

individuals	
  (shade,	
  

moisture,	
  fires,	
  nurse	
  

plants,	
  etc.)?

Seedling	
  conditions	
  similar	
  to	
  mature	
  plants

0

Physiology:	
  Huachuca	
  Water	
  Umbel	
  (Lilaeopsis	
  schaffneriana	
  var.	
  recurva)

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?	
  

Wildfires	
  are	
  likely	
  to	
  increase	
  sedimentation	
  and	
  

negatively	
  impact	
  habitat	
  although	
  an	
  open	
  canopy	
  may	
  

increase	
  light	
  levels.	
  Other	
  sources	
  of	
  erosion	
  such	
  as	
  

recreation	
  and	
  flooding	
  are	
  also	
  considered	
  detrimental	
  

(ENRD).	
  Locations	
  of	
  occurrence	
  have	
  permanent	
  surface	
  

water	
  or	
  are	
  seasonally	
  saturated	
  and	
  where	
  not	
  prone	
  to	
  

flooding	
  (USFWS	
  1999).	
  Flooding	
  can,	
  however,	
  aid	
  

dispersal.	
  Overall,	
  increases	
  in	
  drought,	
  flooding,	
  and	
  

wildfires	
  will	
  have	
  at	
  least	
  some	
  detrimental	
  impacts.	
  

1

2.	
  Adaptations	
  

to	
  survive	
  

water	
  

limitations

Does	
  this	
  species	
  

possess	
  adaptations	
  to	
  

increase	
  survival	
  

during	
  droughts	
  (i.e.,	
  

waxy	
  leaves,	
  water	
  

storage,	
  cavitation,	
  

drought	
  deciduous)?	
  

Leaves	
  may	
  not	
  grow	
  from	
  rhizomes	
  during	
  droughts,	
  

saving	
  energy	
  and	
  exposure.	
  In	
  addition,	
  seeds	
  have	
  some	
  

ability	
  to	
  survive	
  droughts	
  (Titus	
  and	
  Titus	
  2008).

-­1

3.	
  

Photosynthetic	
  

pathway

Which	
  photosynthetic	
  

pathway	
  does	
  this	
  

species	
  use?

C3.

1

	
  	
  	
  	
  	
  	
  	
  	
  	
  
USDA Forest Service RMRS-GTR-302. 2013. 177

Interactions:	
  Huachuca	
  Water	
  Umbel	
  (Lilaeopsis	
  schaffneriana	
  var.	
  

recurva)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Pollination What	
  is	
  the	
  pollination	
  

vector?	
  	
  

Insect.

1

2.	
  Disease	
   Any	
  known	
  

diseases/parasites	
  

that	
  result	
  in	
  mass	
  

mortality	
  related	
  to	
  

temperature	
  or	
  

precipitation?	
  

No.

0

3.	
  Competitors Are	
  populations	
  of	
  

important	
  competing	
  

species	
  expected	
  to	
  

change?

Non-­‐native	
  plants	
  can	
  limit	
  occurrences	
  (USFWS	
  1999),	
  

although	
  no	
  information	
  on	
  problematic	
  species.	
  

Interaction	
  is	
  subject	
  to	
  changes	
  dependent	
  on	
  species	
  

and	
  disturbance	
  regimes.	
  Flowering	
  may	
  be	
  reduced	
  

where	
  cover	
  of	
  competing	
  species	
  is	
  high,	
  possibly	
  from	
  

reduced	
  light	
  levels	
  (Titus	
  and	
  Titus	
  2008).	
  No	
  

predictable	
  change	
  based	
  on	
  various	
  species	
  and	
  

interactions.

0
178 USDA Forest Service RMRS-GTR-302. 2013.

Literature Cited

ENRD (Environmental and Natural Resources Division). 2006. Programmatic 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. 

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., M. Ting, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

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

Titus, P. and J. Titus. 2008. Ecological monitoring of the endangered Huachuca water umbel (Lilaeopsis 

schaffneriana ssp. recurva: Apiaceae). Southwestern Naturalist 53:458–465.

USFWS (United States Fish and Wildlife Service). 1999.Endangered and threatened wildlife and plants:

Designation of Critical Habitat for the Huachuca Water Umbel, a Plant. Federal Register 64:37441–37453.
USDA Forest Service RMRS-GTR-302. 2013. 179

Lemmon Fleabane (Erigeron lemmonii)

SUMMARY

Additional vulnerability to population declines is predicted for this species with future climate change, but this 

is based on limited species information. Its presence in a single location alone is enough to increase vulnerability to any impact. Recruitment in particular may be vulnerable to changes in precipitation. Identification 

of other populations will be important and any translocation needs to consider future conditions of potential 

sites.

Introduction

Lemmon fleabane is a candidate for listing as a Federally endangered or threatened species. The only known 

location for this species is Scheelite Canyon on Fort Huachuca (USFWS 2001). 

Fort Huachuca climate projections used for assessment

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

GCM) and greater evaporation

• 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)

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 Change

Lemmon fleabane is highly prone to extinction as it is only known to occur at one location. The current 

location is relatively invulnerable to human impacts but is exposed to other impacts that may or may not be 

related to climate change. Its specialized habits, however, may help protect it from disturbance. Occurrence 

in shady habitats may reduce exposure to higher temperatures to some extent, but physiological tolerances 

are not known. Hairy leaves will likely help protect plants from increased solar radiation. Flowering occurs in 

August and October and thus may depend on summer rainfall (USFWS 2001). Flowering and recruitment are 

likely vulnerable to projected increases in rainfall variability and reduction in water availability.

-3 0 3 

VULNERABILITY Score Uncertainty

Habitat -0.3 50%

Physiology 2.0 66%

Interactions 1.0 66%

Overall 2.9 60%

Figure Key

Habitat

Physiology

Interactions

Overall

Most 

uncertain

Least 

uncertain

More 

vulnerable

More 

resilient
180 USDA Forest Service RMRS-GTR-302. 2013.

Research Needs

Research needs cover almost all aspects of this species’ biology. Little published information on any topic was 

found on this species making assessment and management difficult.

Management Implications

Potential habitats should be evaluated and surveys should be conducted to identify additional populations 

of this species. Possible threats to the current known population should be evaluated, including erosion 

and flooding. This species may be a good candidate for transplantation or propagation, but future climate 

will need to be considered for any transplant locations. Monitoring will be important and should examine 

recruitment to assure sustainable populations.
USDA Forest Service RMRS-GTR-302. 2013. 181

79

Habitat:	
  Lemmon	
  Fleabane	
  (Erigeron	
  lemmonii)

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?

Grows	
  on	
  vertical	
  cliffs	
  at	
  1900–2200	
  m	
  (USFWS	
  2001).	
  

Not	
  mesic.

0

2.	
  Habitat	
  

elements

Does	
  this	
  species	
  

require	
  specialized	
  

microsites?

Grows	
  in	
  crevices	
  on	
  vertical	
  faces	
  of	
  boulders	
  (USFWS	
  

2001). 1

3	
  Ability	
  to	
  

colonize	
  new	
  

areas

What	
  is	
  this	
  species	
  

dispersal	
  ability?

Wind	
  dispersal	
  of	
  seeds	
  assumed.

-­1

5.	
  Seedling	
  

conditions

Do	
  seedlings	
  require	
  

different	
  conditions	
  

from	
  mature	
  

individuals	
  (shade,	
  

moisture,	
  fires,	
  nurse	
  

plants,	
  etc.)?

Not	
  known.

0

Physiology:	
  Lemmon	
  Fleabane	
  (Erigeron	
  lemmonii)

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?	
  

No	
  known	
  response	
  to	
  disturbance.	
  Presumably	
  

protected	
  from	
  fires	
  on	
  vertical	
  cliffs.	
  May	
  be	
  prone	
  to	
  

erosion	
  following	
  intense	
  rainfall,	
  but	
  may	
  also	
  be	
  

minimal	
  in	
  crevices	
  of	
  rocky	
  cliffs	
  of	
  Scheelite	
  Canyon.	
  

Rock	
  slides	
  are	
  not	
  expected	
  to	
  change	
  with	
  climate.

0

2.	
  Adaptations	
  

to	
  survive	
  

water	
  

limitations

Does	
  this	
  species	
  

possess	
  adaptations	
  to	
  

increase	
  survival	
  

during	
  droughts	
  (i.e.,	
  

waxy	
  leaves,	
  water	
  

storage,	
  cavitation,	
  

drought	
  deciduous)?	
  

None	
  known.

1

3.	
  

Photosynthetic	
  

pathway

Which	
  photosynthetic	
  

pathway	
  does	
  this	
  

species	
  use?

C3.

1

	
  	
  	
  	
  	
  	
  	
  	
  	
  
182 USDA Forest Service RMRS-GTR-302. 2013.

80

Interactions:	
  Lemmon	
  Fleabane	
  (Erigeron	
  lemmonii)

Trait/Quality Question Background	
  Info	
  &	
  Explanation	
  of	
  Score Points

1.	
  Pollination What	
  is	
  the	
  

pollination	
  vector?	
  	
  

Presumably	
  insect	
  pollinated. 1

2.	
  Disease	
   Any	
  known	
  

diseases/parasites	
  

that	
  result	
  in	
  mass	
  

mortality	
  related	
  to	
  

temperature	
  or	
  

precipitation?	
  

None	
  known.

0

3.	
  Competitors Are	
  populations	
  of	
  

important	
  

competing	
  species	
  

expected	
  to	
  

change?

None	
  known	
  but	
  likely	
  limited	
  in	
  specialized	
  habitats.

0
USDA Forest Service RMRS-GTR-302. 2013. 183

Literature Cited

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., M. Ting, I. Held, [and others]. 2007. Model projections of an imminent transition to a more arid 

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

USFWS (United States Fish and Wildlife Service). 2001. Lemmon Fleabane. U.S. Fish and Wildlife Service, 

Southwest Region, Arizona Ecological Services Field Office. 

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