Although it is possible that these bats over-winter in Reversine clinical trial hibernacula still unexposed to Pd or survived due to random factors, it is more likely that some bats have naturally higher survival rates when exposed to the fungus. This survival may result from immunological resistance to Pd, differences in physiology, or behavioral ecology that result in higher resilience. Studies of the little brown myotis demonstrate individual variability in both winter ecology and physiology, including differences in torpor patterns and energy use, and selection of microclimates within a hibernaculum, representing possible foundations for variation in survival. If individual variation in ecology and physiology relate to WNS mortality, then mortality should vary predictably. For example, male little brown myotis utilize their winter energy reserves more rapidly than females, potentially making them more vulnerable to the further depletion of fat reserves when exposed to Pd. Mortality may also vary among bats inhabiting different hibernacula or areas within a hibernaculum that have different microclimates. Higher population declines have been observed among populations of little brown myotis inhabiting warmer hibernacula, a trend possibly linked to the growth rate of Pd, which peaks between 12.5 and 15.8uC and declines at warmer and colder temperatures. Temperatures inside hibernacula of little brown myotis are typically below 10uC but range widely, including environmental conditions with varying suitability for Pd growth. Because temperature also affects the winter torpor behaviors and energy expenditure of bats, variables such as the temperature and individual behavior and physiology are likely to have interacting effects on fungal growth and WNS mortality. Thus, understanding whether or not some bats are better able to survive WNS requires an understanding of the interaction of the environment, host, and pathogen, a concept presented in the disease triangle. However, our current understanding of WNS mortality lacks such context because laboratory studies investigating the disease are conducted under a single environmental condition, typically exposing bats to 500 000 Pd conidia and hibernating them at 7uC, without consideration for individual variation in survival. Our purpose was to examine WNS mortality and survival in a captive population of little brown myotis in the context of this disease triangle. We hypothesized that the number of Pd conidia bats are initially exposed to affects fungal load at the end of hibernation, duration of torpor bouts, and mortality. We further hypothesized that bats hibernating at warm temperatures have higher Pd loads at the end of hibernation, exhibit shorter torpor bouts, and experience greater mortality. Finally, we hypothesized that mortality would be inversely related to body condition at the onset of hibernation, and that mortality would be greatest among males. We found that WNS mortality is influenced by the level of Pd exposure, characteristics of the host, and the environment, and that several variables have interacting effects.