Publication Date


Document Type


Committee Members

Megan Rúa, Ph.D. (Committee Co-Chair); Lynn Hartzler, Ph.D. (Committee Co-Chair); Joe Johnson, Ph.D. (Committee Member); Lisa Cooper, Ph.D. (Committee Member); Volker Bahn, Ph.D. (Committee Member)

Degree Name

Doctor of Philosophy (PhD)


Disturbances in environment can lead to a wide range of host physiological responses. These responses can either allow hosts to adjust to new conditions in their environment or can reduce their survival, and can subsequently cause host traits to shift. Small mammals are particularly vulnerable to stochastic disturbances, like a pathogen introduction, because of their high energy demands. Studies examining host responses to pathogens often focus on species highly susceptible to infection that typically have high mortality rates, leading to a gap in understanding the responses of less susceptible species. My dissertation evaluates the energy balance of Eptesicus fuscus (big brown bats), a species considered less susceptible to the introduced fungal pathogen Pseudogymnoascus destructans (Pd) which causes white-nose syndrome in North American hibernating bats. I quantified changes in body mass, energy expenditures and the abundance of E. fuscus over long-term Pd exposure time. Using 30 years of data for 24,129 individual E. fuscus captures across the eastern US, I found E. fuscus body mass decreased with increasing latitude once Pd was established on the landscape (5+ years). When measuring whole-animal energy expenditures of 19 E. fuscus in lab settings using open-flow respirometry, I found that E. fuscus with long-term exposure to Pd have increases or no change to torpid metabolic rates across a wide range of ambient temperatures. Finally, the overall abundance of E. fuscus increased with Pd exposure, and lactating and post-lactating bats increased abundance with increasing latitude in the eastern US. Taken together, these results suggest that E. fuscus may have a combination of pathogen and intraspecific competitive pressures impacting their populations, particularly in northern latitudes. This dissertation highlights how introduced pathogens can cause spatially variable responses in less susceptible hosts over time, and other ecological pressures may contribute to those responses. Future efforts for understanding the degree of persistence of less susceptible wildlife host populations are critical for predicting how and why their populations change following emerging infectious disease outbreaks and epidemics.

Page Count


Department or Program

Department of Earth and Environmental Sciences

Year Degree Awarded