Date of Graduation

Spring 2013


Master of Science in Biology



Committee Chair

Thomas Tomasi


tri-colored bats, hibernation, torpor, arousals, thermal gradient

Subject Categories



Hibernation is used by many animals to cope with seasonal fluctuations in temperature and food availability. Arousals during hibernation are energetically costly, and optimal ambient temperature (Ta) for energy conservation is different for aroused versus torpid animals. This study tested the hypothesis that bats provided with a large thermal gradient will minimize energy expenditure by selecting the coldest temperatures during torpor and the warmest areas during arousals, and will therefore lose less mass during hibernation than bats provided with a uniform, relatively cold Ta. Sixteen tri-colored bats (Perimyotis subflavus) were divided into two treatment groups (n = 8). Bats in the experimental treatment were housed individually in hibernation chambers with a thermal gradient (ca. 8 - 17 degrees C), and bats in the control treatment were similarly housed but at a uniform temperature (ca. 8 degrees C). Total mass lost, movement within chambers, and hibernation behavior were compared between treatments. Bats provided with a temperature gradient did not show an overall preference for colder temperatures while torpid and warmer temperatures while aroused. Bats in both treatments spent a similar amount of time aroused; however, since bats in the experimental treatment entered torpor in warmer ambient temperatures, they lost significantly more mass during hibernation. These results support empirical evidence that hibernators may select ambient temperatures warmer than those which minimize torpid metabolic rates. In certain circumstances, a preference for an elevated Ta may provide an adaptive advantage by counteracting some of the negative physiological effects associated with metabolic suppression during prolonged torpor.


© Risa Marie Wright

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