Thermoregulation and behavior of a peripheral population of evening bats (\u3ci\u3enycticeius humeralis\u3c/i\u3e)

I used temperature-sensitive radio transmitters to measure body temperatures of tree-roosting evening bats (Nycticeius humeralis) at the northern edge of their range in Lenawee Co., Michigan. Temperature at sunset, diurnal temperature, and nocturnal temperature significantly correlated with use of torpor, whereas ambient temperature at sunset of the previous night, temperature at sunrise, amount of precipitation, abundance of insects, roost type, number of roost-mates, reproductive condition, and age did not. An analysis of individuals roosting in the same tree on the same day suggested that additional factors might determine exactly how low and for how long bats adjust their body temperatures. I also recorded nocturnal activity at the roost with a video recorder and receiver-logger and constructed an ethogram of seven behaviors associated with entering or emerging. Evening bats spent only 144 ± 114 (SD) min foraging each night, which is less than other species of bats