CRL: General Conservation Projects - Species Of Concern

CRL: Conservation Projects - Species Of Concern

Differential Response of a Native Arizona Gray Squirrel and an Introduced Abert’s Squirrel to a Mosaic of Burn Severities
  • Time Period: August 2011-Present

  • Student: Shari Ketcham

  • Location: Santa Catalina Mountains, AZ, U.S.A.

  • Project Details (click to expand/reduce)
  • Major Questions: What burn severities do tree squirrels use post fire regarding resources such as dreys, cavities, and food? How large are the patch sizes of the burn severities that tree squirrels choose to use? Are there any competition factors between tree squirrels for resources post fire? If so, what resources do tree squirrels compete for? What is the estimated abundance and distribution of tree squirrels on the Santa Catalina Mountains?

  • Major Findings: NA-Research in Progress

Occurrence and habitat use by Big Cypress fox squirrels on public lands
  • Time Period:August 2016 - May 2021

  • PhD student: Kira Hefty

  • Location: Southwest Florida, U.S.A.

  • Project Details (click to expand/reduce)

    Project Description & Bio:

    Kira and pupsIn Florida, native wildlife species face multiple threats including human development, habitat fragmentation, fire suppression, invasive species, and changes in the hydrologic regime. One of the greatest challenges to conserving species in this unique environment is a general lack of knowledge of species-specific habitat requirements and movement behavior. Big Cypress fox squirrels (Sciurus niger avicennia) are an endemic subspecies of fox squirrel in southwest Florida. Because so little is currently known about its extent of occurrence and landscape-level habitat requirements, S. n. avicennia has been declined listing as a federally protected species. Most studies involving this charismatic subspecies have been conducted in urban environments rather than in their natural habitat. In 2012, Big Cypress fox squirrels were named as a Species of Greatest Conservation Concern in Florida’s Wildlife Legacy Initiative Wildlife Action Plan. Kira will be working on public lands with multiple federal and state agencies to decrease knowledge gaps concerning this unique subspecies and provide science-based conservation and management recommendations. Kira is also interested in connecting with community members and establishing long-term outreach programs that will facilitate local interest in conserving Florida’s delicate and special ecosystems.

    Research Questions:

    1) What is the extent of occurrence of S. n. avicennia? 2) Which habitat features are associated with S. n. avicennia presence? 3) How has habitat degradation and fragmentation affected S. n. avicennia dispersal and movement patterns?

    Big Cypress fox squirrel

    Big cypress fox squirrel - photo courtesy of John Kellam


Noninvasive conservation techniques for monitoring spatial ecology and habitat use: conservation of the threatened narrow-headed gartersnake, Thamnophis rufipunctatus
  • Time Period: 2016 - 2021

  • PhD student: Brian Blais

  • Location: Central Arizona (Mogollon Rim region)

  • Project Details (click to expand/reduce)

    Project Description & Bio:

    Understanding ecological dynamics of a species is paramount to uncover life history traits and adaptations to environmental stimuli. One such field is spatial ecology and habitat selection. By tracking animal movements, we gain insight into their resource requirements, movement dynamics, and home ranges. Moreover, radio telemetry techniques can also investigate social and reproductive behaviors, activity, and physiological tolerances. This is warranted for species reintroductions and conservation translocations, especially since a data void exists regarding the viability of reintroductions. The success of conservation-driven translocations is dependent on the subsequent survival and reproduction among that given population.

    The narrow-headed gartersnake, Thamnophis rufipunctatus is a small, semi-aquatic snake endemic to lotic riparian areas of the Mogollon Rim region in Arizona and New Mexico. Due to population decline and habitat loss largely stemming from predation and competition by non-native species, T. rufipunctatus was listed as threatened in 2014. A multi-partnered conservation working group, including Arizona Game & Fish Department and U.S. Fish & Wildlife Service, joined to formulate T. rufipunctatus management and recovery objectives including: 1) establish a viable reintroduction program from an ex situ source; 2) identify biotic and abiotic characters associated with seasonal microhabitat usage; and 3) characterize terrestrial behavior to better inform potential conservation measures regarding projects in occupied habitat.

    My interests are broad but generally focus on wildlife conservation, especially applied non-invasive techniques that address ecological questions. I work directly with the Arizona Center for Nature Conservation — Phoenix Zoo’s conservation department to address objective #1 and provide science-based conservation and management recommendations towards the recovery of narrow-headed gartersnakes. Working collaboratively on ways to facilitate ex situ management as a robust tool for species recovery can be applicable across a wide variety of taxa. Part of my research takes advantage of a unique opportunity to study behavioral, physiological, and life history traits at the ex situ level to better understand and systematically address conservation questions at the in situ level. In 2016, KCRL, the Phoenix Zoo, and management agencies conducted the first conservation translocation of zoo-propagated T. rufipunctatus  into a site within its native range and devoid of non-native threats.

    Currently, I use a non-invasive radio telemetry technique (see Wylie et al. 2011 Herpetological Review) and other tools to monitor gartersnake populations. Many of these novel techniques are applicable to other taxa for conservation purposes. I’m also interested in connecting with outreach programs to facilitate all-around interest in wildlife conservation and management. This includes genomic techniques (e.g., phylogeography, eDNA), road ecology, and citizen-science initiatives. Often, I address my interests with herpetofauna as they provide excellent models for conservation and ecology.

    Major questions:

    1) What is the spatial and behavioral ecology of T. rufipunctatus and which characters influence microhabitat selection? 2) What can we learn from ex situ management and how can it be a tool for maximizing viability of in situ conservation translocations? 3) Can novel, non-invasive techniques generate the same information as status quo techniques, especially for population monitoring?

    Personal background:

    Brian has a background in ecology, evolution, and wildlife management gained from a blend of academics and employments. Originally from Connecticut, Brian spent several years working for their state wildlife agency partaking in a plethora of field work including bat population monitoring, imperiled shorebird conservation, amphibian disease ecology, and public engagement. Brian has also been on the road with studies or jobs in the Midwest, Australian, and Peru. Following a lifelong passion, Brian acquired a MSc degree studying the genomic phylogeography of the smooth greensnake before making his way to the American Southwest. For fun, Brian enjoys cooking, traveling, and leaping out of cars to help turtles cross roads.

    See more about my collaborative research endeavors here:


Current status, habitat use, and variables that influence human-bear conflict in Andean bears in Colombia
  • Time Period:August 2016 - May 2020

  • PhD student: Ivan Mauricio Vela-Vargas

  • Location: Chingaza National Natural Park, Colombia

  • Project Details (click to expand/reduce)

    Project Description & Bio:

    Located in the northernmost Andes, Colombia has a unique combination of natural conditions as the Andes split into 3 ranges that results in a complex combination of ecosystems and great biodiversity. High Andean forests and Paramos are the most biodiverse ecosystems in the world, yet are also where most of the human population in Colombia live. These areas are also the main habitat for the most unique bear species, the Andean bear (Tremarctos ornatus).
    Given the high degradation of most Andean ecosystems, the habitat and natural range of the Andean Bear has been severely fragmented and disturbed by human activities. Severe threats such as habitat loss, hunting, and human-bear conflicts are threats to the species across its distribution, and are especially relevant for the Chingaza massif, considered the most important stronghold for bear conservation in Colombia.
    The loss of natural habitats and hunting pressure are especially evident in Chingaza Massif and its National Natural Park (Chingaza National Natural Park), where within the protected 76600 ha, Andean bear occupancy has increased 100% in the last few years, where > 33 individuals have been identified. As presence of bears increases and habitat declines, conflicts with human settlements increase concomitantly, mostly near park boundaries. Conflict often translates into retaliation hunting of bears, promoted by landscape features, management practices, and hunting.

    My project is focused on three major questions that are: 1. Which is the real availability and the status of the natural habitats used by Andean bears in the Chingaza Massif and the east Cordillera of Colombia? 2. How do biotic and abiotic variables affect the movement and habitat use of Andean Bears in the Chingaza National Natural Park and its buffer zones? and 3. What variables are enhancing human – bear conflicts in the Chingaza Masiff.

    Major questions:
    My project is focused on three major questions that are: 1. Which is the real availability and the status of the natural habitats used by Andean bears in the Chingaza Massif and the east Cordillera of Colombia? 2. How do biotic and abiotic variables affect the movement and habitat use of Andean Bears in the Chingaza National Natural Park and its buffer zones? and 3. What variables are enhancing human – bear conflicts in the Chingaza Masiff.

    Personal background:

    Mauricio has worked in mammalian ecology and reproductive biology in agricultural landscapes in Colombia. His experience is focused on the effect of agricultural landscapes in species and community ecology and in seeking strategies to improve landscape planning. He is part of the Colombian Mammalogy board.



Conservation of the freshwater rivers of Nepal: Endangered dolphins as indicators of river system health
  • Time Period: January 2017 - December 2019

  • PhD student: Shambhu Paudel

  • Location: Nepal (Karnali, Sapta Koshi, and Narayani river systems)

  • Project Details (click to expand/reduce)

    Project Description & Bio:

    Ganges River dolphin, Platanista gangetica gangetic, is the only cetacean species recorded in Nepal. No considerable improvements on population status have been recorded for these small isolated upstream groups (especially in Nepal) in more than two decades, in fact the range of distribution has been reduced significantly as one of the four previously important river systems now have been abandoned and abundance have declined (Smith et al., 1993; Paudel et al., 2015). Less than 30 individuals were counted visually in three river systems of Nepal (Paudel et al., 2015). Large structures like dams, flood-control structures, and embankments for irrigation projects, agriculture and hydroelectric power have impacts on the river dolphins that have led to the loss of longitudinal and lateral connectivity of habitats (Vannote et al., 1980; Ward, 1998; Ward et al., 1999; Dudgeon, 2000; Bunn and Arthington, 2002; Nilsson et al., 2005). As a consequence, clear effects on distribution, gene flow, movement patterns, and behavior have been noticed. At the same time, immense pressure from artisanal fisheries have been documented and two dolphins were entangled in the recent two years (per.obs). Management and maintenance of adequate water flows and ecologically functional habitats is thus the most important challenge for river dolphin conservation in Nepal where only barely viable populations are remaining (Richter et al., 2003; Smakhtin et al., 2007; Paudel et al., 2015). To conserve freshwater ecosystems and their associated critical endangered species, additional research is needed to establish priorities efforts for the conservation and management.

    Surfacing river dolphin in Karnali river system of Nepal. Photo: S Paudel

    Development of meaningful specific conservation plans for river dolphins is always denied due to lack of data on population status, underwater behavioual patterns (diel activities) and interaction with water flow ecology. Many previous studies (Shrestha, 1989; Smith et al., 1993, Jnawali and Bhuju, 2000; WWF, 2007) have only focused on population abundance estimation using visual counts without detecting observation errors and with only superficial attempts on threats analysis. However, recent studies (Paudel et al., 2014; Paudel et al., 2015; Paudel et al., 2016) have put more emphasis on the cause of the population decline and proposal for solutions. Key elements required for an effective conservation or management strategy is a reliable estimate of population size, conservation ecology, genetic information and finding ways of mitigating conflicts with human activities.

    Study site, prepared by S Paudel

    This project aims to improve scientific knowledge on Ganges river dolphins to inform management and conservation efforts for freshwater rivers where endangered aquatic species has been survived. It is also hope that strategies that are applicable for Ganges river dolphin will protect other taxa that share the same habitats like the Gharial (endangered crocodile). Following research questions will be addressed by this project:

    1. How can survey techniques to provide robust estimates of abundance for Ganges river dolphin in Nepalese river systems be improved?

    2. How do underwater behaviors and diel activity patterns of Ganges river dolphins change spatially and temporarily?

    3. How do artisanal fishing communities affect the habitat use of Ganges river dolphins?

    4. Is currently available natural water flow (discharge) sufficient to conserve Ganges river dolphins in Nepalese waterways during the low water season?

    5. Is there a taxonomic and phylogenic relationship between isolated groups of Ganges River dolphins?

    Personal description:

    • Russell E. Train Fellow (World Wildlife Fund-USA) for Freshwater Conservation  in Nepal

    • Officially affiliated with Institute of Forestry, Tribhuwan University in Nepal as assistant professor

    • Worked for freshwater river conservation in Nepal focusing  river dolphin and other similar texa like Gharial to improve freshwater species conservation efforts

    • Aim to deliver and assist Government of Nepal to prepare “Dolphin recovery action plan” after the completion of PhD project

    Conservation research award/grants: OPCF-Hong Kong; Rufford Foundation-UK; Chicago Zoological Society/CBOT Endangered Species Grant, USA; IMATA-USA; Mohamed Bin Zayed Species Conservation Fund-United Arab Emirates; The EBS Award of the Society for Marine Mammalogy-USA.

    Selected journal papers:
    Shah KB, Paudel S (2016) Ecology of crocodile and dolphin in the Koshi Basin. Chapter 11 in: Doody TM, Cuddy SM, Bhatta LD (eds) Connecting flows and ecology in Nepal: current state of knowledge for the Koshi Basin. Sustainable Development Investment Portfolio (SDIP) project. CSIRO, Australia. pp 123–138

    Paudel S, Levesque JC, Saavedra C, Pita C, Pal P. (2016), Characterization of the artisanal fishing communities in Nepal and potential implications for the conservation and management of Ganges River Dolphin (Platanista gangetica gangetica). PeerJ 4:e1563; DOI 10.7717/peerj.1563

    Paudel S, Pal P, Cove MV, Jnawali SR, Abel G, Koprowski JL, Ranabhat R. (2015). The Endangered Ganges River dolphin (Platanista gangetica gangetica) in Nepal: abundance, habitat and conservation threats. Endangered Species Researc, 29(1):59-68. DOI: 10.3354/esr00702

    Paudel, S., Timilsina, Y. P., Lewis, J., Ingersoll, T., & Jnawali, S. R. (2015). Population status and habitat occupancy of endangered river dolphins in the Karnali River system of Nepal during low water season. Marine Mammal Science, 31(2), 707-719.

    Paudel, S., Raj Jnawali, S., & Ram Lamichhane, J. (2012). Use of geographic information system and direct survey methods to detect spatial distribution of wild olive (Olea cuspidata Wall.) from high mountain forests of northwestern Nepal. Journal of Sustainable Forestry31(7), 674-686.

    Paudel, S., Magranti, T., & Lamichhane, J. R. (2011). Antimicrobial activity of wild olive crude extracts in vitro. International Journal of Pharma Sciences and Research2(3), 110-113.

    Research in Media (related to PhD project):

    Nepal’s endangered river dolphins return (2015/09/12)

    Number of freshwater dolphins doubles in two decades: Study (2014/09/14)

    Endangered dolphin spotted (2014/04/02)

    Dolphin survey from Dec (2013/11/30)

    Prey dearth, habitat loss put Karnali river dolphins on ‘edge of extinction’ (2012/09/01)

Developing an ex situ propagation strategy of Mount Graham red squirrels (Tamiasciurus fremonti grahamensis) to positively affect their chances of survival after release into the wild
  • Time Period:Fall 2016 -Present

  • PHD student: Stuart Wells

  • Location: The Phoenix Zoo and Pinaleño Mountains AZ, U.S.A.

  • Project Details (click to expand/reduce)
  • Project Description & Bio:

  • I have always been drawn to science, in particular to science-based questions such as how and why. I am particularly interested in applying information gained from scientific exploration directly towards understanding how species function in ecological systems and developing or improving how we manage animals within those systems. The field of conservation biology lends itself to these direct inquiries of how and why especially towards understanding how to manage ex situ animals destined for reintroduction. Effective species conservation is of crucial importance because the anthropogenic activities prevalent in the world today negatively impact nearly every aspect of the natural world. The effect of these activities on species abundance and biodiversity is either direct as a result of harvesting or exploitation, such as over-hunting and illegal trade of animals, or indirect as a result of environmental and ecological changes, such as climate change and watershed manipulation. These intrusions ultimately cause species declines, and can lead to local extirpation, or without managed intervention, species extinction. Consequently, developing an understanding of how to manage animals ex situ to maximize the likelihood of their survival when introduced into the wild is a promising tool for enhancing species conservation programs. The pilot propagation and release program for Mt. Graham red squirrel (Tamiasciurus fremonti grahamensis) is an example of one such effort. This subspecies was listed as critically endangered in 1987, due to drastic population decline caused by forest wildfire and subsequent disease that severely impacted its habitat and resource availability. Although studied extensively in the wild, the Mt. Graham red squirrel has yet to reproduce in an ex situ setting, placing importance on developing an efficient propagation and release program, coupled with an active habitat improvement program, as an essential component of the conservation of this species.

  • Due to the imperiled nature of T. f. grahamensis, the future survival of this species may rely on augmentation of ex situ propagated individuals to replenish the wild population. Much is known about the habitat preferences, foraging requirements, and social structure of Mount Graham red squirrels in the wild (Brown 1984, Sanderson 2009, Steele 1998.) Both sexes are solitary and have are extremely territorial (Sanderson and Koprowski 2009.) They are larder hoarders and maintain a “midden” that also serves to demarcate their territory (Sanderson and Koprowski 2009.) Intense territorial aggression is relaxed during the breeding season when males seek out receptive females to breed. It is believed that the female estrus cycles occur only one per breeding season (Steele 1998), and female receptivity is thought only to occur within a four or six-hour window (USFWS 2015.) Although the Mount Graham red squirrels have been held ex situ successfully (Wells, 2012), ex situ reproduction has not yet occurred. My research will use known hormone markers to ascertain and validate physiological patterns indicative of estrus, and by examining the associated male to female behavioral responses. Behavior-physiological information will then be used to develop management techniques to determine when to introduce pairs for breeding while minimizing the likelihood of injury, or estrus disruption due to aggression. Finally, I will also investigate optimal methods for ex situ rearing to maximize survival of individual squirrel translocated to in situ by attempting to create ex situ rearing conditions indicative of ideal habitat, or by mimicking natal dispersal cues (Merrick and Koprowski, 2016.)

If you build it will they come? Artificial midden creation and settlement by Mt. Graham red squirrels

Time Period: January 2017 - May 2019

  • PhD student:Marina Morandini

  • Location: Pinaleño Mountains, Arizona, U.S.A.

  • Project Details (click to expand/reduce)
  • Project Description & Bio:

  • I am interested in which factors can regulate or limit population abundance. No population increases without limit, but understanding the factors that prevent this phenomenon is not easy. There are intrinsic and extrinsic factors that influence population size. Extrinsic factors influence populations by actions of other species, such as predators or competitors, and by physical-chemical factors such as climate or nutrient supplies. Intrinsic factors instead are internal to the population, such as sex, age, behavior and genetic traits. Understanding which factors could affect population dynamics of a particular animal or plant is the core of conservation, land management, fisheries and pest control and are crucial to developing specific management plans for individual species.

  • Research questions:
    Despite more than fifteen years of legal protection, Mt Graham Red Squirrel population plummeted after a peak of 562 squirrels in 1999 to approximately 250 individuals in the recent years.  Why is the population abundance not increasing? Are food resources a limited factor for this population? Can artificial midden help the settlement of squirrels during dispersal? Is there a high predator pressure on the squirrel population on Mt. Graham? Is it possible that parasites play a role in the regulation of this population?

  • Personal background:
    I completed my master’s degree in Italy where I studied the competition between the European Red Squirrel (Sciurus vulgaris) and the invasive species Pallas’s squirrels (Callosciurus erythraeus), whose  native range is in southeast Asia. In particular I analyzed the competition for food and space, using telemetry and live-trapping.
    I worked The University of Milan to control the invasive population of the Grey Squirrel near Milan. 

    I volunteered for six months for Kluane Red Squirrel project (Yukon, Canada) where I worked to collect data on populations dynamics of red squirrel and snowshoe hare.


Terrestrial ecology of the endangered Sonoran tiger salamander, Ambystoma mavortium stebbinsi
  • Time Period: August 2016 -Present

  • Master's student: Colin Brocka

  • Location: San Rafael Valley, Santa Cruz and Cochise counties, Arizona, U.S.A.

  • Project Details (click to expand/reduce)
  • Project Description & Bio:

  • The Sonoran tiger salamander (Ambystoma mavortium stebbinsi) is a subspecies of tiger salamander endemic to the San Rafael Valley (SRV) of southeastern Arizona. Historically, this species bred in naturally occurring ponds and springs, but arroyo cutting (the formation of deep, steep-sided, ravines by ephemeral waterways) and erosion in the area has caused most of the SRV to lose natural surface water. Cattle tanks created by ranchers have taken the place of natural springs and are now primary breeding sites for salamanders. Larvae can develop into either gilled aquatic adults called paedomorphs, or undergo metamorphosis into terrestrial salamanders without gills. The subspecies was listed as endangered in 1997 due to its highly restricted distribution, dependence on human-constructed environments, breeding site invasion by non-native fish and/or bullfrogs, and risk of frequent die-offs due to disease. The ecology of Sonoran Tiger Salamanders outside of breeding ponds, and their dispersal patterns are largely unknown. The terrestrial metamorph is the only life stage capable of re-populating cattle tanks that lose salamanders due to drying or disease, and thus this stage is critical to conservation and maintenance of metapopulation dynamics. Through the use of radio-telemetry and habitat measurements, this study will provide information on the spatial ecology and life history of the terrestrial morph, and facilitate the development of well-informed management practices needed to conserve this species.


    Major Questions:

    1. How does the Sonoran tiger salamander move in its terrestrial habitat?

    2. What habitat characteristics and refuge types do terrestrial Sonoran Tiger Salamanders use?

Space Use, Sociality, and Foraging Ecology of Antelope Jackrabbits
  • Time Period: May 2013-Present

  • Student: Maria Altemus

  • Location: Southeastern Arizona, U.S.A.

  • Project Details (click to expand/reduce)
  • Major Questions: The antelope jackrabbit (Lepus alleni) is a large hare found in southern Arizona south into Mexico that has not been intensely studied and about which little is known.  Early studies on antelope jackrabbits were conducted in the 1930’s, in relation to cattle grazing, but since then, very little has been published about these secretive and fast animals.  Antelope jackrabbits are so called because their white rump is displayed when they flee, similar to the pronghorn (Antilocapra americana).  These animals inhabit the shrubby grasslands that span the U.S.-Mexico border.  They are uniquely adapted to their desert environment, as they do not require free water to survive, but instead rely on their food sources (such as mesquite and succulents) and physiological specializations to persist.  One food that these animals eat is the fruit of the Pima pineapple cactus (Coryphantha scheeri var. robustispina).  This cactus is listed as endangered by the U.S. Fish and Wildlife Service as endangered and it is therefore important to learn about the ecology of this plant as well as the animals that depend on it. 

  • Through my research, I am hoping to examine more closely at the social structure and behavior of antelope jackrabbits, as they are sometimes seen in groups of up to 5 or 6.  I also hope to place radio or GPS collars on animals, as this has never been done, and learn more about habitat use and territoriality.   This aspect of my research will tie in with antelope jackrabbit’s use of Pima pineapple cactus and their role in the seed dispersal of this endangered cactus. 

  • Major Findings: NA-Research in Progress

Effects of Re-establishing Black-tailed Prairie Dog Colonies on Southeastern Arizona Grasslands
  • Time Period: January 2011-Present

  • Student: Sarah Hale

  • Location: Las Cienegas National Conservation Area, AZ, U.S.A

  • Project Details (click to expand/reduce)
  • The loss of biodiversity can have profound effects on an ecosystem, especially when a species lost is important to that ecosystem. The keystone species concept was introduced over 40 years ago, by Paine, referring to the role of the starfish Pisaster ochraceus and tritons Charonia spp. in the marine littoral zone (Paine 1969, Mills et al. 1993). A keystone species is exceptionally important in maintaining the organization and diversity of their community (Mills et al. 1993), and has been defined as a species whose impact on its community or ecosystem is large, and disproportionately large relative to its abundance (Power et al. 1996).

  • The black-tailed prairie dog (BTPD: Cynomys ludovicianus) is considered a keystone species, and was extirpated by humans from its historical range in Arizona by 1960. The BTPD is seen as a pest by many people, but these ecosystem engineers provide burrows for other species (e.g. burrowing owls [Athene cunicularia] and rattlesnakes [Crotalus sp.]), excavate nutrient rich soil that, in turn, provides rich vegetation for grazers, and serve as a food source for many carnivores and birds of prey. Between 2008 and 2011 Arizona Game and Fish Department translocated approximately 380 BTPDs from New Mexico and Sonora to 3 sites at Las Cienegas National Conservation Area in southeastern Arizona to improve grassland health and increase species diversity within the BTPDs’ historical range. In 2012 a fourth site was populated with prairie dogs from Las Cienegas.

  • Research Questions: 1) Why do colonies exhibit the survival and reproductive rates observed? 2) What is the fate of dispersers, and why do certain individuals disperse from colonies? 3) Do translocated BTPDs establish a role as a keystone species? My results will provide important information for future management decisions, reduce human-prairie dog conflicts by documenting the impacts of their presence, assess their keystone species status, and provide information about where to introduce new colonies.

Competition between native and introduced species
  • Time period: August 2010 – present

  • Student: Jonathan J. Derbridge

  • Location: Pinaleño Mountains, Arizona, USA

  • Project Details (click to expand/reduce)
  • Major Questions: I am studying mechanisms of competition between native and introduced species. Exploitation competition occurs when individuals have indirect negative effects on other individuals by restricting access to a common resource. Competition from introduced species for common food resources may force native species to forage more widely, and consume sub-optimal diets. Isolated populations of territorial species may, over time, become less adept at excluding ecologically similar competitors. I am using experimental removals of introduced Abert’s squirrels (Sciurus aberti) to test hypotheses on the impacts of dietary and spatial overlap with the Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis). I am also conducting tests of exploitation competition that relate to the relative abilities of an invader to succeed, and a native species to maintain its advantage. These tests include examining how Abert’s squirrels may take advantage of larder-hoarding by red squirrels, and comparing territorial behavior of Mount Graham red squirrels with individuals in other red squirrel populations.

  • Research Questions: What are the impacts of dietary overlap between native and introduced species occupying similar niches? Does syntopy with an introduced species incur fitness costs associated with changes in home range size and composition for native species? Do introduced non-hoarding species compete with larder-hoarding native species through kleptoparasitism? Does isolation from interspecific competition lead to weakening of territorial behavior and facilitate successful invasions?

Proximate cues and ultimate consequences for natal dispersal and settlement in an altered forest landscape: influence of experience, behavior, and habitat
  • Time Period: May 2010 - Present

  • Student: Melissa Merrick

  • Location: The Pinaleño Mountains, AZ, U.S.A.

  • Project Details (click to expand/reduce)
  • Major Questions: I am interested in factors influencing animal movements and habitat selection in the face of landscape alteration and fragmentation. Movement via natal dispersal is an important ecological mechanism contributing to gene flow, population structure and population dynamics, and guards populations against local extinction. Natal dispersal includes three stages: emigration, transience and exploration, and immigration and settlement. Whether an individual disperses, if it disperses how far it travels, how many places it explores, and where it settles is highly variable and is conditioned upon many factors including individual condition, local population density, sex ratios, resource abundance, experience in the natal area, habitat fragmentation, and individual behavior differences. Previous studies have shown that experience in the natal area provides individuals with important habitat cues which aid in deciding upon where to settle and also leads to variation in settlement patterns. Individual behavior differences may play a role in dispersal distance and settlement decisions, including decision rules individuals employ when selecting a place to settle. Local density of conspecifics and associated sex ratios may influence male settlement decisions, whereas female settlement decisions may be more driven by available food resources. Increasingly, habitat fragmentation is also becoming an external factor influencing dispersal decisions and evidence suggests that small mammals dispersing through a fragmented habitat matrix tend to disperse further and explore less than individuals in contiguous habitat. I am testing several hypotheses related to natal habitat preference induction, behavioral phenotypes, decision rules, and habitat fragmentation and their influence on natal dispersal, especially transience and immigration.

  • Some of my main research questions include: Do natal habitat cues (e.g. habitat structure, associated microclimate, and food availability) influence where settlement occurs? Do individual behavior differences (behavioral phenotypes) influence exploratory movements, decision rules, dispersal distance, and survival? Does forest fragmentation influence decision rules, settlement choices, and survivorship?

  • Major Findings To Date: Compared to non-peripheral red squirrel populations, dispersal in MGRS is sex-biased and exploration movements and settlement distances are far greater. Individual behavior differences explain variation in dispersal distances - active, aggressive individuals tend to disperse longer distances compared to less active, docile individuals. Natal habitat structure may play a role in cueing dispersers in on locations in which to settle. Forest structure derived from remotely sensed LiDAR data (e.g. canopy cover, basal area of live trees) in an individual’s natal area is more similar to forest structure at an individual’s settlement location compared to random locations. Further analyses are underway.

Road and traffic effects on movements and space use of red squirrels
  • Time Period: 2009 - present

  • Student: Hsiang Ling Chen

  • Location: Mt. Graham, AZ, U.S.A.

  • Project Details (click to expand/reduce)
  • Road ecology is a burgeoning field of inquiry as roadways expand in number, length and width. We know that roads fragment habitats, increase mortality, change microclimates, and can act as barriers…thus they present a challenge in the conservation of biodiversity. Roads may function as impermeable barriers to some species while being semi-permeable to others. We are examining the relative permeability of roads to two species in the Pinaleno Mountains of southeastern Arizona: federally endangered Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) and non-native Aberts squirrels (Sciurus aberti).

  • Major Questions: Do red squirrels avoid roads? If so, what factors are most influential to avoidance? Do they avoid forest edges created by roads, forest gaps, or traffic disturbances?

Competition for conifer cones as a potential mechanism of endangerment for the Mt. Graham red squirrel.
  • Time Period: 2007 - 2010

  • Student: Rebecca Minor

  • Location: Pinaleño (Graham) Mountains, Graham County, southeastern Arizona (Coronado National Forest).

  • Project Details (click to expand/reduce)
  • Major Questions/Objectives: Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. The sky island region of the southwestern US and northwestern Mexico supports many isolated endemic species that are restricted to high elevation forests and vulnerable to species invasions. One such range, the Pinaleño Mountains in southeastern Arizona, supports the entire population of the critically endangered Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) (MGRS). A second tree species, the Abert’s squirrel (Sciurus aberti) was introduced to the range in 1941 by Arizona Game and Fish Department for increased recreational hunting opportunities. Our field experiment quantified the impact of introduced Abert's squirrels on rates of food removal within the range of the MGRS. We placed single cones on 4m x 4m plots (1m spacing) at random locations in the forest and observed the rate of removal by both species of squirrel through direct observation and remote cameras. Then Abert’s squirrels were excluded from cone removal by placing cones in wire mesh tubes that were of small diameter, so that only MGRS could enter. burn severity? Does the landscape pattern (patchiness) of burn severity affect squirrel habitat use?

  • Major Findings: In the presence of Abert's squirrels, the time until 50% of cones were removed was significantly faster than when Abert's squirrels were excluded. The impact on food availability as a result of cone removal by Abert's squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. We suggest that a successful management approach for MGRS with target the impact of Abert’s squirrels on food availability. That a large proportion of cones available to both MGRS and Abert’s squirrels were removed before cones available only to MGRS suggests the importance of considering removal of the introduced Abert’s squirrel as a priority in conserving red squirrels in the Pinaleño Mountains.

Factors influencing habitat use by wildlife relative to landscape disturbance
  • Time Period: August, 2006 – December, 2010

  • Student: Sandy Doumas

  • Location: The Chiricahua Mountains, AZ, U.S.A.

  • Project Details (click to expand/reduce)
  • Major Questions: I am interested in factors influencing habitat use by wildlife relative to landscape disturbance, especially fire. Fire is a necessary and recurring disturbance in many ecosystems with profound effects over time on vegetation composition, structure, and landscape pattern. The effects of fire on ecosystems have been complicated by decades of fire suppression followed by reintroduction of fire into fire-deprived ecosystems. Historically, fire-adapted forests were relatively resilient to fire, and some current forest management techniques seek to restore forests to historical composition, structure, and landscape pattern to recreate fire-resiliency. I study habitat use by native wildlife to better understand the response of wildlife to alterations of vegetation structure and pattern following the reintroduction of fire. Specifically, I study habitat use of the Mexican fox squirrel, Sciurus nayaritensis chiricahuae, in conifer forests of the Chiricahua Mountains of SE Arizona, which have experienced several recent fires.

  • Some of my main research questions include: Does burn severity of recent fires and vegetation structure affect squirrel habitat use? How are the vegetation characteristics most important to habitat use related to burn severity? Does the landscape pattern (patchiness) of burn severity affect squirrel habitat use?

  • Major Findings: To Date: Mexican fox squirrels feed in forest with open understory and closed canopy cover. Vegetation within home ranges of squirrels is characterized by lower understory density, consistent with the effects of low-severity fire, and larger trees than random locations. These results suggest that return of low-severity fire can help restore habitat for Mexican fox squirrels and other native wildlife species with similar habitat affiliations in forests with a historical regime of frequent, low-severity fire. Habitat use by Mexican fox squirrels is positively associated with moderate burn heterogeneity, suggesting that small areas of severe burn incorporated within low-severity burn may be beneficial to Mexican fox squirrels and other native wildlife species.

Ecology of Neotropical Tree Squirrels
  • Time Period: May – July 2009 and June – July 2010

  • Student: Rosa Jessen

  • Location: Area de Conservacion Regional Tamshiyacu-Tahuayo, Loreto, Peru

  • Project Details (click to expand/reduce)
  • Major Questions: Does vegetation type affect density and habitat use of neotropical tree squirrels? What vegetation characteristics are influential to rainforest squirrels? What is the mammalian diversity associated with neotropical tree squirrels?

  • Rainforests are home to the greatest mammal diversity, but little is known about most of the rainforest species. Small mammals in the rainforest play important roles, providing ecological services such as seed dispersal and pollination. These species also drive the dynamics and complexity of biological communities by serving as predators and providing a prey base for a range of rainforest species. The Amazon Basin contains one of the world’s largest rainforests, much of which is found in Peru. Five species of tree squirrels are found in the Peruvian Amazon: northern Amazon red squirrel (Sciurus igniventris), southern Amazon red squirrel (S. spadiceus), Bolivian squirrel (S. ignitus), Amazon dwarf squirrel (Microsciurus flaviventer) and neotropical pygmy squirrel (Sciurillus pusillus) but there is a great lack of knowledge of neotropical tree squirrels and no one has examined their role in rainforests. Little is known about life history, ecological interactions, and distribution of these squirrels.

Response of the Mount Graham Red Squirrel (Tamiasciurus hudsonicus grahamensis) to Postfire Conditions
  • Time Period: 2006-2007 (field work) 2008-2012 (data analysis, writing, publication)

  • Student: Seafha Tuttle (Blount)

  • Location:Mt. Graham, AZ, U.S.A.

  • Project Details (click to expand/reduce)
  • Major Questions/Objectives: Our main objectives were to assess space use of Mount Graham red squirrels, vegetation characteristics associated with middens, and continued occupancy of middens, mountain-wide, by Mount Graham red squirrels in areas of various burn severity.

  • Major Findings: A main effect of season on both size of home ranges and core areas was apparent. No main effect of burn severity on size of home range or size of core area was detected. Slope, canopy cover, burn severity, and aspect were important variables for distinguishing middens from random locations. Dead trees, aspect, and total number of trees were important for distinguishing between occupied and unoccupied middens. Mountainwide, occupancy of middens was influenced by burn severity of middens and surrounding vegetation. Also, unburned middens were occupied more continuously than burned middens.

  • Citation: Blount and Koprowski. 2012. Response of the Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) to postfire conditions. The Southwestern Naturalist 57(1):8-15

What can endemics tell us? Space use and ecology of the endemic Arizona gray squirrel
  • Time period: August 2006 – December 2009

  • Student: Nichole Cudworth

  • Location: Huachuca Mountains, Arizona, USA

  • Project Details (click to expand/reduce)
  • Research questions: How does mating strategy influence the space use of Arizona gray squirrels? At what scale are Arizona gray squirrels selecting nest sites?

  • Major findings: Parental investment often differs between the sexes. For mammals, females invest heavily in reproduction, due to the high costs of pregnancy and lactation. Consequently, fitness of females is likely limited by the availability of food. Fitness of males, however, is more likely limited by the availability of mates. We investigated how these limiting factors would be predicted to influence the space use of Arizona gray squirrels. Arizona gray squirrels do not defend territories, and a female will only enter estrus for one day throughout the breeding season, thereby significantly reducing mating opportunities for males. We found that home ranges of Arizona gray squirrels are large (59 ha) and vary between sexes and seasons. Males had larger home ranges than females overall, and males increased home-range sizes during the breeding season, when males were traveling greater distances to locate receptive females. Females, however, maintained relatively constant home-range sizes throughout the year, although these home ranges were still large compared to other, closely related species, suggesting a system in which food availability is likely patchy and variable.

  • Tree squirrels are highly dependent upon nests to provide a place to rest, raise young, avoid predators, and escape inclement weather. However, the scale at which nest-site selection has been analyzed has not been consistent, despite the obvious management implications when designing habitat plans. Arizona gray squirrels use leaf nests, or dreys, extensively throughout the year. We evaluated nest-site selection at 4 spatial scales: forest-type, nest-site, nest-tree, and within-canopy placement. Arizona gray squirrels select nesting locations within all spatial scales, although the benefits provided within these spatial scales likely varies, including providing access to food and water, cover from predators, travel routes to and from nest trees, thermal protection, and stable nesting structures. Riparian areas and the availability of Arizona sycamores (Platanus wrighti) for nest sites were especially important, emphasizing the need to protect these unique forest types in the mountains of the southwestern United States.

Ecology of the endemic Mearns’s squirrel (Tamiasciurus mearnsi) in Baja California, Mexico
  • Time Period: August 2004 – May 2008

  • Students: Nicolas Ramos-Lara

  • Location: Sierra de San Pedro Mártir, Baja California, Mexico

  • Project Details (click to expand/reduce)
  • Major Questions: 1. What is the current situation of the arboreal squirrels of Mexico (review chapter) 2. Do Mearns’s squirrels have specific habitat requirements for nesting? 3. Do home-range dynamics and habitat use of Mearns’s squirrels differ from other congeners? 4. Do life-history and behavioral tactics of Mearns’s squirrels differ from other congeners?

  • Major Findings: 1. In Mexico, there are 14 recognized species of arboreal squirrels of which four are endemic, with the states of Chiapas and San Luis Potosi possessing the greatest diversity. 2. Presently, all species are listed under some category of risk by IUCN, seven by Mexico’s SEMARNAT, and only one by CITES. 3. Our literature survey yielded 37 publications revealing that a dearth of scientific information still exists on the arboreal squirrels of Mexico. 4. States with a greater diversity of arboreal squirrels also have higher annual wood productions, which may pose a serious threat to their persistence. 5. Mearns’s squirrels rely primarily on tree cavities for nests, with nest tree species, nest tree condition, nest tree size (DBH), canopy cover, and occurrence of white firs (Abies concolor) as important characteristics of the habitat for nesting. 6. Without larderhoards (middens), home-range dynamics of Mearns’s squirrels are similar to nonterritorial squirrels of the genus Sciurus, suggesting that middens played an important role in the evolution of territoriality in Tamiasciurus. 7. Using satellite imagery, I found that remote areas in the Sierra de San Pedro Mártir appear to have suitable habitat for the species. 8. Survival of adult Mearns’s squirrels was influenced by sex and body mass. 9. Mearns’s squirrels are heavier and apparently also larger than other congeners, possibly in part as an adaptation to feed on large pine cones (Pinus). 10. Interyear variation in weather and food supply strongly influenced fitness-related traits and behavior of Mearns’s squirrels.

Differential response to fire by an exotic and an endemic species complicate endangered species conservation
  • Time Period: May 2006 to Oct 2007

  • Student: Nate Gwinn

  • Location: Mount Graham (Pinaleño Mountains), Graham County, Arizona, USA

  • Project Details (click to expand/reduce)
  • Major Questions: The Nuttall Complex fire burned ~ 12029 ha in the Pinaleño Mountains of southeastern Arizona in summer 2004, including large areas of the upper elevation mixed conifer and spruce fir forests. Historically, mixed conifer forests in the Pinaleños experienced a low severity fire every 4 to 6 years, and spruce-fir forests experienced infrequent stand-replacement burns every 300 years. To investigate the effect of wildfire on exotic and introduced species, we looked at the differential use of burned and unburned areas by introduced Abert’s squirrels and the endemic and critically endangered Mount Graham red squirrel in the Pinaleños. We assessed effects of wildfire on habitat use of introduced Abert’s squirrels and native red squirrels by sampling species-specific feeding sign and employing radiotelemetry to reveal use of burned and unburned areas by both species. We document differential use of fire-impacted habitats that favors the introduced species thus complicating traditional conservation efforts used in forested environments.

  • Major Findings: Our study is the first to document the positive response of an exotic mammal and negative response of the native species to wildfire and suggests that fire must be used judiciously as a restoration tool. Abert’s squirrels thrive in mixed conifer forest, our study documented that Abert’s squirrels fed, moved and nested within mixed conifer forest affected by wildfire. Home ranges of Abert’s squirrels were smaller in burned than in unburned forest. This suggests that habitat created by wildfire was of higher quality than unburned areas. Abert’s squirrels selected sites that had more live trees, less logs, and higher canopy closure than random sites within the burned area, similar to characteristics of mature ponderosa pine forests that Abert’s squirrels prefer in native range. These characteristics include high basal area, mature trees with interlocking crowns, and an understory with little down and woody debris. Transect data on feeding sign also indicated that Abert’s squirrels remained in burned areas. In effect, wildfire may be improving habitat for Abert’s squirrels in mixed conifer forest by creating preferred structure.

Variation among red squirrel populations: Ecological differences at the edge of their range and response to fire.
  • Time Period: 2004 - 2006

  • Student: Katharine M. Leonard

  • Location: Pinaleño (Graham) Mountains, Graham County, southeastern Arizona (Coronado National Forest). White Mountains, Greenlee County, east-central Arizona (Apache-Sitgreaves National Forest).

  • Project Details (click to expand/reduce)
  • Major Questions/Objectives: Populations at the edge of their geographic range may inhabit areas with different habitat structure and resources than central populations, and thus may differ in population dynamics. Understanding these unique characteristics is especially important for populations of high conservation priority, such as the endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis). The Mt. Graham red squirrel (MGRS) is endemic to southeastern Arizona, represents the southernmost red squirrel population and is found at lower densities than conspecifics in the center of the range. To determine if differences are due to conditions at the southern periphery of the range, we compared habitat characteristics, demography, body mass, space use and nesting behavior with another subspecies located at the southern edge of the range, the Mogollon red squirrel (T. h. mogollonensis). In addition, we studied demography and behavior of MGRS inhabiting areas within and outside areas of low-intensity burn following the Nuttall fire complex in the Pinaleño Mountains (summer 2004).

  • Major Findings: We found that mean and minimum daily temperatures were higher at Mt. Graham whereas maximum temperatures were higher in the White Mountains, male Mogollon red squirrels were heavier than male Mt. Graham red squirrels in all seasons and female Mogollon red squirrels were slightly heavier than female Mt. Graham red squirrels in spring, proportion of squirrels in reproductive condition was lower in female Mogollon red squirrels, Mogollon red squirrels had smaller home ranges, used different types of nests and traveled less distance to nest than Mt. Graham red squirrels. There were no differences in annual rainfall, seedfall, habitat characteristics or survival between mountain ranges. Localized conditions appear to account for the disparity between populations. These differences demonstrate the importance of evaluating attributes of peripheral populations for maximizing persistence and intraspecific diversity.

  • Upon examining MGRS physical and behavioral traits between areas of no burn and low-intensity burn from the 2004 Nuttall fire, we found that body mass, proportion of individuals in reproductive condition, and distance squirrels traveled to nest did not differ between squirrels within and outside the perimeter of the fire. Within the perimeter, red squirrels had smaller home ranges and shifted territories less frequently and had shorter distances from their previously held territories than squirrels outside the perimeter. Mount Graham red squirrels evolved with patchy, low-intensity fires like those that burned in mixed-conifer forests in the Pinaleño Mountains and may be able to persist in areas affected by this level of disturbance.

Forest disturbance and the long term population persistence of the Mt. Graham red squirrel:  a spatially explicit modeling approach
  • Time Period: 2002 - 2006

  • Student: David Wood

  • Location: Pinaleño (Graham) Mountains, Graham County, southeastern Arizona.  (Coronado National Forest), U.S.A.

  • Project Details (click to expand/reduce)
  • Major Questions: Difficulties in conservation and management of forest ecosystems arise from dynamics of forests and challenges in understanding disturbance. Disturbances, especially fire and insect outbreaks, have increased in occurrence and severity due to climate change and forest management. 
    The Pinaleño Mountains of southeastern Arizona, USA have suffered catastrophic fire and large scale insect outbreaks in the last decade and are the only home of the federally endangered Mt. Graham red squirrel (MGRS:  Tamiasciurus hudsonicus grahamensis), therefore an understanding the impacts of forest disturbances on population dynamics is critical for conservation of this fragile species. We sought to develop and a spatially explicit population model to predict long-term population dynamics of MGRS and to combine this model with life-history data and high-resolution satellite imagery with the goal of examining effects of future disturbances on the population.

  • Major Findings: We tested model predictions using available range-wide red squirrel life-history data from the literature and fieldwork specific to the MGRS. An input data set using general mean life history values overpredicted MGRS abundance. However, we found significant correlation with known squirrel abundance using a general data set with curtailed fecundity and survival. A model with MGRS-specific data provided the best fit to observed population size. We investigated potential impacts of two major threats to the MGRS: competition from introduced Abert’s squirrels (Sciurus aberti) and increased levels of predation. Predation and particularly competition could have significant effects on the future population of the MGRS. Careful attention must be used to model the viability of fringe populations as peripheral populations can have a different life history than populations found in the range core.

  • We also modeled potential Mt. Graham red squirrel habitat by identifying characteristics of cover surrounding their centrally defended larderhoards to assess effects of forest disturbance on habitat. We classified high spatial resolution satellite imagery into ground cover classes and used logistic regression to determine areas used by squirrels. We also used midden locations in conjunction with slope, elevation, and aspect variables to create a predictive habitat map for Mt. Graham red squirrels. Squirrels selected areas of denser forest with higher seedfall for midden sites. Among active middens, those in the densest and least damaged forests were occupied in more seasons than those in more fragmented and damaged areas. The future conservation of red squirrels and the return of healthy old-growth forests to the Pinaleño Mountains will rely on management in mixed conifer zones of the mountain and active restoration of highly damaged upper elevation spruce-fir forests to return them to squirrel habitat. This model allows us to evaluate the spectrum of fine- to coarse-scale disturbance effects (individual tree mortality to the area wide boundaries of a disturbance) with high-resolution satellite imagery.

  • Lastly, we combined our spatially explicit population model with the spatial models of habitat heterogeneity. We parameterized the model with estimates of extent, frequency, and severity of insect outbreaks and fire and used the number of Mt. Graham red squirrel populations dropping below critical population thresholds to characterize the effects of these disturbances. We determined future disturbances, even at low levels, are likely to have a detrimental effect on Mt. Graham red squirrel population size. This model framework can be used to predict effects of future disturbance on habitat quality and population persistence for species in general.

Suitability of Potential Habitat for the Extirpated Arizona Black-tailed Prairie Dog
  • Time Period: 2002 - 2005

  • Student: Carol A. Coates

  • Location: Las Cienegas National Conservation Area and Ft. Huachuca Military Base, AZ, USA Upper San Pedro River Valley, Ejido Morelos, Sonora, Mexico

  • Project Details (click to expand/reduce)
  • Major Questions/Objectives: Study objectives were: 1) to determine if areas identified as potential re-introduction sites were suitable to support BTPD populations by comparing habitat characteristics with an occupied BTPD colony in northern Sonora, Mexico, 2) assess what pre-release management actions may be required in these areas, and 3) determine whether the presence of prairie dogs could potentially affect avian grassland species diversity in Arizona.

  • Major Findings: There was considerable overlap in habitat variables between the occupied BTPD colony in Sonora and potential re-introduction sites in Arizona. However, greater densities of grass, shrubs, and trees were found on the potential sites Arizona sites than on the occupied Sonora colony. Though grass species diversity did not differ between the Arizona and Sonora sites, grass species diversity was much lower on the Ft. Huachuca site, mainly due to large amounts of introduced Lehmann lovegrass. Management actions needed on the Arizona sites to render them more suitable for BTPD introduction include mowing grass and decreasing shrub and tree densities possibly through use of prescribed fire.

  • Using fixed-radius point counts, avian species diversity was determined to be higher on the Arizona sites that on the Sonora sites. The greater number of avian species on the Arizona sites can be attributed to higher shrub densities and wider range of physical and environmental features, such as ephemeral streams and mesquite thickets. The reintroduction of BTPD on the Arizona sites would likely alter plant species composition and structure and, therefore, the abundance of avian species, especially those species requiring trees and shrubs for nesting and foraging. However, avian species that require open spaces, such as shrikes and larks, or the presence of abandoned small mammal burrows for nesting, such as the burrowing owl, may increase on the Arizona sites due to BTPD habitat management practices.

  • Based on the vegetation characteristics, proximity to land protected from development, and historical presence of BTPD, the Arizona sites appear to be suitable locations for re-introduction of BTPD. Pre-release habitat management, such as mowing and prescribed fire, as well as a more fine-scale assessment of specific release sites (especially soil characteristics) will be required before attempting to return Black-tailed prairie dogs to southern Arizona.

Space use, ecology, & conservation of Chiricahua fox squirrels
  • Time Period: 2001 - 2004

  • Student: Bret S. Pasch

  • Location: Chiricahua National Monument (National Park Service), Chiricahua Mountains, southeast of Willcox, Cochise County, Arizona.

  • Project Details (click to expand/reduce)
  • Major Questions/Objectives: Chiricahua fox squirrels (Sciurus nayaritensis chiricahuae) are endemic to the Chiricahua Mountains of southeastern Arizona. A paucity of natural history information and uncertain conservation status served as impetus for us to initiate a descriptive ecological study of the species. In addition, we examined the impacts of human suppression of fire on patterns of habitat use and survival of Chiricahua fox squirrels in fire-suppressed and fire-prescribed areas of the Chiricahua Mountains. We used radiotelemetry techniques to elucidate space and habitat use, survivorship, and fire impacts in our investigation.

  • Major Findings: We found that Chiricahua fox squirrels differed in several capacities from more widespread species of tree squirrels. Females had a mean of 1.6 (range 1-2) offspring per litter and we found an overall population density of 0.07/ha, both parameters lower than other North American tree squirrels. Seasonal fluctuations in body mass and space use generally paralleled other species of tree squirrels with some notable exceptions. Male Chiricahua fox squirrels maintained a fairly constant body mass and large home range size throughout the year, in contrast to other tree squirrel species that typically show a reduction in both measures in non-mating seasons. Extreme spatial and temporal fluctuations of food experienced by Chiricahua fox squirrels might result in annual patterns in space use and body mass that differ from tree squirrels living in forests with a greater abundance of food.

  • We found differences in habitat use and survival of squirrels in areas of the Chiricahua Mountains with differing fire regimes (suppressed vs. prescribed). Core areas of squirrels within fire-suppressed areas were larger and contained more understory shrubs than core areas of squirrels in fire-prescribed areas. Shrub cover and canopy heterogeneity influenced core-area size and distance traveled, and squirrels that were depredated traveled farther than conspecifics that survived, but shrub cover and canopy heterogeneity were not directly associated with squirrel survival. Suppression-induced increases in understory vegetation might force squirrels to travel greater distances to meet energetic requirements and thereby increase predation risk. Retention of mature forested canyons and restoration of natural fire regimes will be important for the persistence of Chiricahua fox squirrels.