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 biotic 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, remote sensing
Projects: using BirdNET on UA's HPC to identify Mt. Graham red squirrel vocalizations from long-term passive acoustic recordings to supplement monitoring efforts; habitat & 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
Interests: animal communication, avian biology, conservation, comparative methods, 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 in the southwestern US & Mexico
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
Leighanna Olaker
Interests: art, arthropods, biodiversity
Projects: assessing arthropod diversity at Mt. Graham red squirrel middens
August Walser
Interests: wildlife biology
Projects: assisting on all of the above
Recent findings
Kohl, K.D., Barts, N., Peralta-Martinez, K., Lackey, A., Lyons, E., Maurer, M., Tripoli, D., Yawitz, T., Martínez-Mota, R., Pasch, B., Dearing, M.D., and B. K. Trevelline. In review. How consistent is ‘the dynamic gut’?: Complex physiological responses to dietary fiber and protein in three rodent species with different feeding strategies.
Barts, N., Trevelline, B., Dearing, M.D., Derting, T., Martínez-Mota, R., Pasch, B., and K.D. Kohl. In review. Gut bacterial and fungal communities respond uniquely to dietary fiber and protein manipulation in three rodent species.
Laurenzi, J., Mahoney, S.M., and B. Pasch. In review. Sound pressure levels correspond to emergence counts in urban bat bridge roosts.
Brzozowski, R., Mahoney, S.M., Combrink, H.J., Hefty, K.L., & B. Pasch. 2024. Impact of forest management on the communication distance of an endangered tree squirrel. Journal of Wildlife Management. e22689 link
Mahoney, S. M. & B. Pasch. 2024. Evolutionary lability of food caching behavior in mammals. Journal of Animal Ecology. 93: 862-875. link UA news
Beauregard, N.D., Theimer, T.C., Sferra, S.J., & B. Pasch. 2024. Using autonomous recording units to identify and monitor western Yellow-billed Cuckoos in southwestern xeroriparian habitat. Wildlife Society Bulletin. 48:e1546.
Griffiths, G.C., & B. Pasch. 2024. Variation in responses to conspecific and heterospecific advertisement vocalizations in sympatric grasshopper mice (Onychomys). Journal of the Acoustical Society of America. 156:524-533.
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.
Squirrel summaries
from Brzozowski et al. 2024 Journal of Wildlife Management
Forest restoration impacts on Mt. Graham red squirrel vocalizations
On the high peaks of the Pinaleño Mountains that harbor endangered Mount Graham red squirrels, fire suppression, insect outbreaks, & wildfire have drastically changed the shape of the forest & contributed to habitat degradation. Such structural changes can impact how sound moves through the environment to influence the social lives of vocal animals. Red squirrels commonly produce territorial rattle vocalizations to protect central food hoards termed middens. In some populations, rattles help neighbors tell each other apart, ultimately leading to increased survival & recruitment. Understanding the nature of vocal interactions, including how forest structure shapes their spread, is therefore important to red squirrel conservation & management. In a recent study led by graduate student Ryan Brzozowksi (MS, 2024) of the Mt. Graham Biology Programs, the team combined playback experiments from below the treetops, physiological models of squirrel hearing, & remote aerial imaging of the forest to study how recent restoration efforts affect the communication distance of Mt. Graham red squirrels. Across the entire study area, they found that rattles were most quickly absorbed in areas containing the highest density of trees, resulting in a halving of squirrel communication distance. In addition, rattles in thinned & fuel‐reduced areas traveled further through the forest, potentially facilitating the development of social neighborhoods that benefit squirrels. Importantly, the researchers found that remote aerial imaging (LIDAR) was an effective method to describe how forest structure influences sound, setting the stage for mountain-wide assessment of acoustic habitat quality. More broadly, their approach indicates that integration of signaling & sensory ecology with remote sensing can be a useful framework to inform forest management & wildlife conservation.
from Mahoney & Pasch 2024 Journal of Animal Ecology
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 exploring patterns that have emerged 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.
Opportunities
Kind, curious, & creative students & post-docs are encouraged to contact us about opportunities. Please include a description of how past experiences & present interests align with our studies & your future.
Current open positions: 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.
Dedication
Dr. Matthew Denman Smith Memorial Fellowship in Animal Behavior