Big brown bats are one of the most widely distributed of America's bats, ranging from Canada to northern South America and the Caribbean Islands.

Big brown bats are most often found in trees, attics, and bat houses in the summer. 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 or they will migrate.

Young ones (called pups) are born in nursery colonies where females congregate together. 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 well. Pups completely stop nursing from their mothers at about 9 weeks old, and at this time are able to eat insects on their own.

Of all the North American species of bats, this is the one most closely associated with humans because of its year-round use of buildings. Big brown bats are highly beneficial to humans because they consume extremely high numbers of insects.

Even though big brown bats are abundant throughout the United States, their populations are decreasing every year. The population is lowing because of human disturbance (the bats are especially vulnerable when hibernating), people killing bats (especially when bats accidentally fly into people's houses), and loss of habitat. We can help big brown bats by teaching people about them, and by putting bat houses up thereby giving them a home!

Photographs of big brown bats