Volume 12, Issue 4, Winter 1994


IN LATE SUMMER, big brown bats (Eptesicus fuscus) begin fattening up in preparation for hibernation, storing about a third of their body weight in fat— adequate to last until spring as long as they are not disturbed too frequently. These bats are hardier than most species in winter and often roost in cave or mine entrances in sub-freezing temperatures. Their body temperatures may fall as low as 29 degrees Fahrenheit. Males commonly form tight clusters, but females are most likely to hibernate alone, especially in warmer regions.

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