The Big Brown Bat Eptesicus fuscus Back to Meet Some Bats Big brown bats are one of the most widely distributed of American bats, ranging from Canada to northern South America and the Caribbean Islands. Big brown bats enjoy roosting in buildings and tree cavities in summer. These bats are most often found in trees, attics, and bat houses.
Maternity colonies can consist of hundreds of females, although smaller colonies are more common.
Big browns usually enter caves or buildings where they will hibernate safely throughout the winter months. The usual litter size is two bats in the eastern United States, and one pup in the western U.S. Pups are born without any fur and with their eyes closed. Immediately after the pups are born, they begin to squeak, and within 24 hours their eyes are open. For the first two weeks of life, while the mother bat is at rest the young stay nestled under her wing. During the third week they are able to fly, and practice until they can negotiate their own turns, land, and hang from the walls.