Mt. Graham Biology Programs 

We are biologists interested in applying studies of animal behavior & ecology to conservation & management. We research & monitor the federally endangered Mt. Graham red squirrel (Tamiasciurus fremonti grahamensis) in the Pinaleño Mountains (dził nchaa si'an) & conduct other studies on & around the mountain to inform the biology & plight of squirrels. 

Long-term monitoring on population trends & food resources are shared with state & federal agencies, non-governmental organizations, & the general public through a website, annual reports, presentations, & publications. Initially started in 1989, the program is funded by The University of Arizona & grants from state & federal agencies. The program integrates ecological monitoring, basic & applied research, graduate & undergraduate education, & outreach.

Information on the project's history can be found on the former director's (Dr. John Koprowski, professor emeritus) page

Below please find current members, projects, & opportunities. 

Director & Associate Professor, School of Natural Resources & the Environment, Wildlife Conservation & Management

Bret Pasch

Interests: animal communication (mechanisms, function, evolution), mammalogy, long-term studies, natural history, sensory system-signal-environment interactions, sky islands, wildlife conservation & management

Projects: See below for a sample of current studies. We also collaborate with the Phoenix Zoo on captive breeding of Mt. Graham red squirrels for eventual release & the San Diego Zoo on biobanking.

Teaching: place-based, hands-on

Biology & Conservation of Mammals (WFSC 497/597): The study of mammalian biology & applications to conservation & management. Techniques used to study mammals, including species identification, observation, & live-animal trapping, with application to conservation & management; emphasis on Arizona species.

Conservation Bioacoustics (WFSC 451/551):  Applications of bioacoustics to wildlife conservation & management. This experiential course is organized thematically from the perspective of senders, receivers, & the environment & chronologically by seasonal opportunities to collect, analyze, & discuss data on species of conservation/management concern throughout diverse life zones of southern Arizona (e.g. sandhill cranes on playas, beavers in riparian areas, montane Mt. Graham red squirrels, & kangaroo rats in desert grasslands). Activities include learning how to record animals & the environment, application of analytical tools to visualize & quantify recordings, interpretation of data to inform conservation/management, & critical evaluation of the primary literature. Focus on biophony (collective sound of living organisms) is contextualized relative to other soundscape components (anthrophony, geophony) to broaden application to natural resource managers writ large. All students maintain a field notebook coupled to sound recordings that explore seasonal changes in biological communities of a particular location to foster sense of place. Graduate students conduct a group research project on a topic of their choice to be submitted for peer review. This course encourages cross-disciplinary dialogue & debate. Competencies developed are broadly transferable, including matching tools to questions, hands-on learning of emerging technologies relative to conservation, project design, regional autecology, & communication skills.


research scientists, post-docs, & affiliates

Henri Combrink

Interests: bioacoustics, conservation, machine learning, movement ecology, natural resource management

Projects: using BirdNET on UA's HPC to identify Mt. Graham red squirrel vocalizations from long-term passive acoustic recordings to supplement monitoring efforts; movement ecology of Mt. Graham red squirrels


Vicki Greer 

Interests: conservation, long-term data, squirrels, wildlife biology

Projects: updating Mt. Graham red squirrel historical database in collaboration with UA's Data Science;  data collection & curation


Sean Mahoney

Interests: animal communication, avian biology, conservation, museum studies, sensory ecology, wildlife biology 

Projects: integrating mammalian phylogenies with long-term data on Mt. Graham red squirrels to understand the factors influencing food caching strategies (larder vs. scatterhoarding) relative to climate past & future; bird-squirrel interactions 


graduate students

Ryan Almeida 

Interests: bioacoustics, bimodal communication, kangaroo rats, road noise

Projects: information content of airborne & seismic signals in territorial kangaroo rat footdrums & impacts of anthropogenic noise on animal communication


Ryan Brzozowski 

Interests: animal communication, bioacoustics, forest ecology

Projects: impacts of vegetation change & forest management (PERP) on Mt. Graham red squirrel acoustic communication, importance of sender & receiver geometries

Nikki Reck 

Interests: animal communication, bioacoustics, biotic communities of Arizona, conservation

Projects: individual variation in Mt. Graham red squirrel vocalizations; dear enemy effect


Ellie Tierney 

Interests: arthropods, elevational gradients, natural history, small mammals

Projects: Pinaleño elevational gradient- documenting small mammal communities at different life zones on Arizona's most prominent mountain as barometers for ecosystem change; assessing relationships between Mt. Graham red squirrel middens, arthropods, & shrews


undergraduate students

Julia Laurenzi 

Interests: bats, bioacoustics, bridges, conservation

Projects: quantifying the relationship between sound pressure levels & emergence counts of urban bat populations


August Walser 

Interests: wildlife biology   

Projects: assisting on all of the above


Recent writing

Mahoney, S. M. & B. Pasch. 2024. Evolutionary lability of food caching behavior in mammals. Journal of Animal Ecology. link   UA news 

Beauregard, N.D., Theimer, T.C., Sferra, S.J., & B. Pasch. Using autonomous recording units to identify and monitor western Yellow-billed Cuckoos in southwestern xeroriparian habitat. In revision

Griffiths, G.C., & B. Pasch. Variation in responses to conspecific and heterospecific advertisement vocalizations in sympatric grasshopper mice (Onychomys). In revision

Laurenzi, J., S.M. Mahoney, & B. Pasch. Sound pressure levels correspond to emergence counts in urban bat bridge roosts. In review

Brzozowski, R., Mahoney, S.M., Combrink, H.J., Hefty, K.L., & B. Pasch. Impact of forest management on the communication distance of an endangered tree squirrel. In review

Riede, T.R., Kobrina, A., & B. Pasch. 2023. Anatomy and mechanisms of vocal production in harvest mice. Journal of Experimental Biology. 227(5): jeb246553.

Brzozowski, R., Kobrina, A., Mahoney, S.M., & B. Pasch. 2023. Advertising and receiving from heights increases transmission of vocalizations in semi-arboreal mice. Behavioral Ecology and Sociobiology. 77:83

Quinn, C., Burns, P., Hakkenberg, C., Salas, L., Pasch, B., Goetz, S., & M. Clark. 2023. Soundscape components inform acoustic index patterns and refine estimates of bird species richness. Frontiers in Remote Sensing. 4:1156837.

Darwaiz, T. , Pasch, B., & T. Riede. 2023. Postnatal remodeling of the laryngeal airway removes body size-dependency of spectral features for ultrasonic whistling in laboratory mice. Journal of Zoology 318:114-126.

Kobrina, A., Letowt, M., & B. Pasch. 2022. Vocal repertoire and auditory sensitivity of white-throated woodrats (Neotoma albigula). Journal of Comparative Psychology 137(2):116-128.

Riede, T., Bone, L., Darwaiz, T., Kobrina, A., & B. Pasch. 2022. Mechanisms of sound production in deer mice (Peromyscus). Journal of Experimental Biology. 225: jeb243695.

Kobrina, A., Letowt, M., & B. Pasch. 2022. The influence of social context on pinyon mouse (Peromyscus truei) vocalizations. Journal of Mammalogy. 103:275-286.

Fernández-Vargas, M., Riede, T., & B. Pasch. 2022. Mechanisms and constraints underlying patterns of acoustic variation in rodents. Special Issue on “Constraints on animal displays and implications for signal function and evolution.” Animal Behaviour. 184:135-147.


from Mahoney & Pasch 2024 

Squirreling it away: examining past food hoarding behavior to predict future responses to environmental change

The scientific name for the genus of endangered Mt. Graham red squirrels (Tamiasciurus) translates from Greek into one who "stewards or hoards in the shadow of its’ tail." Food hoarding is a fundamental behavior that allows animals to access resources during periods of scarcity & has important implications for plant-animal interactions, community dynamics, & ecosystem health. However, understanding the factors that influence mammals to ‘squirrel it away’ has only been studied intensively in a small number of mammals. A recent publication in the Journal of Animal Ecology led by Sean Mahoney of the Mt. Graham Biology Programs explored the evolution of food hoarding behavior by integrating data on this busy behavior for nearly 40% of mammals representing 2 subclasses & 5 orders, & a nearly quarter century dataset on caching behavior on Mt. Graham red squirrels. Using phylogenetic comparative methods, the authors found that food caching strategies- whether one stores food in a single larder or scatters food about- are extremely flexible or labile, with many species transitioning between larderhoarding & scatterhoarding numerous times independently. Ancestral state reconstruction indicated that the first mammals (shrew-like Morganucodon from the late Triassic 237 million years ago) likely larderhoarded food, akin to modern-day shrews that have similar lifestyles in analogous forested habitats. The authors identified climatic features (temperature & seasonality) & population density as important factors that recurringly influenced food hoarding, with colder temperatures, more seasonal environments, & higher population densities being associated with larderhoarding. When the researchers zoomed in on Mt. Graham, they found that red squirrels tended to invest less in their larderhoards- termed middens- in years when population numbers were low, implicating competition for food & pilferage (petty theft) as important mechanisms. However, variation in mean annual temperature over the past 24 years- roughly 5º F- was not associated with changes in food hoarding behavior, likely because middens act like refrigerators & have buffered perishable food stores...for now. 

Beyond its contribution to basic science, the study has important implications for the conservation of imperiled species in a changing climate. By looking backwards over millennia of mammalia, the findings can help wildlife managers predict the factors that may push species toward different caching behaviors. Should disturbances resulting from climate change & alterations in population density decrease the benefits of larderhoarding, critical habitat designations may need to be refined to support changes in home range requirements & diet. More practically, biologists have historically used middens as a 1 to 1 index of squirrel population size. Changing conditions may promote squirrel scatterhoarding & necessitate alternative monitoring efforts. The research highlights how the study of animal behavior can be a powerful tool to address conservation challenges.



Kind, curious, & creative students & post-docs are encouraged to contact us about opportunities. 

Current open positions (April 2024): Funding is available for a PhD student to participate in a collaborative project with the Phoenix Zoo & National Forest Foundation to release & monitor captive-bred Mt. Graham red squirrels on a remote part of the mountain. 


Dr. Matthew Denman Smith Memorial Fellowship in Animal Behavior