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Species Description

Big Brown Bat

Eptesicus fuscus

Species Image


Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Order: Chiroptera
Family: Vespertilionidae


The long, glossy fur is chocolate-brown on the back and sides and paler on the belly. Relatively large for an American bat, measuring 10.3 - 13 cm (4.1 - 5.1 in) in total length. The flight membranes are thick and black. This bat has broad black ears.

Life Cycle

Mating takes place in the fall. Two young are born the following May or June. Beginning in May, pregnant females roost together in a "nursery colony." The average number of females in such colonies is from 40 - 100, but as many as 300 individuals have been recorded. The young are born naked and blind. Their eyes open on the second day and in 3 - 4 weeks they are capable of flying. They are fully weaned in 5 weeks.

Natural History

The Big Brown Bat is a solitary animal, except when in nursery colonies and at winter roosts. Hollow trees, slabs of loose tree bark, caves, and crevices in rock ledges provide natural roosting places for this bat, but human activities have provided many more potential roosts in the form of old mine shafts, buildings, and homes. The Big Brown Bat is largely crepuscular, becoming active at dark, when it feeds for a period of time. By midnight it retires to a night roost for a while, then feeds some more before returning to its daytime roost. This species feeds on beetles, flies, moths, and true bugs which it catches and eats while in flight. It forages for food by flying slow, straight courses over water, forest canopies, wooded clearings, and even around city lights. Predators of the Big Brown Bat include the Barn Owl and Great Horned Owl, and Rat Snakes. The Big Brown Bat has a recorded lifespan of 19 years.


Big Brown Bat Region Map This species ranges throughout the United States and southern Canada. The Big Brown Bat is a year-round resident that hibernates in the winter months either singly or in groups of up to 100 individuals in well-protected roosts such as caves, mines, or buildings. In the summer months it may live as much as 80.5 km (50 mi) from winter roosts. In Georgia this bat can be found statewide.

Conservation Status

The Big Brown Bat is considered uncommon to common, depending on the area.

Similar Species

The Evening Bat and several species of the Genus Myotis resemble the Big Brown Bat, but individuals in these species are noticeably smaller and have differences in ear and ankle anatomy.