Eptesicus fuscus (Big Brown Bat)

Weight: 14-21 grams

Wingspan: 32-39 centimeters


Southern Canada through southern North America into South America, including many islands in the Caribbean.

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Ecology and Behavior:

These bats are closely associated with humans and are familiar to more people in the United States than is any other species of bat. Most summer roosts are located in attics, barns, bridges, or other man-made structures, where colonies of a few to several hundred individuals gather to form maternity colonies. They move into caves, mines, and other underground structures to hibernate only during the coldest weather. Where most of these bats winter remains unknown. It emerges at dusk and flies a steady, nearly straight course at a height of 6-10 meters (20-33 feet) in route to foraging areas. Its large size and steady flight make it readily recognizable. Apparently, some individuals use the same feeding ground each night, for a bat can sometimes be seen following an identical feeding pattern on different nights. After feeding, the bat flies to a night roost to rest; favored night roosts include garages, breezeways, and porches of houses.

Food Habits:

These bats consume beetles, ants, flies, mosquitos, mayflies, stoneflies, and other insects.

Reproduction and Longevity:

Mating occurs in autumn and winter, females store sperm, and fertilization takes place in spring. In the eastern United States, big brown bats usually bear twins in early June. In the western United States, usually only one baby is born each year.

Status of Populations:

Common throughout most of its range.

Text, in its original form, provided by T. L. Best, M. J. Harvey, and J. S. Altenbach. Printed spectrographs provided by M. J. O'Farrell. Distribution maps, call descriptions, and AnaMusic sound clips produced by W. L. Gannon. Accounts assembled by T. C. Sanchez-Brown.