Big Brown Bat {Eptesiciis fuscus) 



Description: This species is easily distinguished from other bats in the Northern Rocky 



Mountains by its large size (only the Hoary Bat is larger); weight range is 16-30 g. 

 Pelage is brown, with hair extending only slightly onto the wing and tail membranes. 

 The dark-colored ears are of medium size (12-19 mm); the tragus is less than half the 

 length of the ear and is blunt. Calcar is usually keeled. Tip of tail extends about 5 mm 

 beyond tip of uropatagium. 



Distribution: Widespread across all of the United States and southern half of Canada south to 

 northern South America. 



Habitat and Habits: Found in a variety of wooded and semi-open habitats. Colonial, often 



forming colonies in tree cavities, rock crevices and buildings. Hibemacula include caves 

 and mines, buildings (attics) and other man-made structures; winter records exist from 

 Alberta (Schowalter and Gunson 1979) and British Columbia (Nagorsen et al. 1993). 

 Maternity colonies have been found in attics, barns in northeastern Montana (Swenson 

 and Shanks 1 979), and sometimes in tree cavities. Mating occurs in fall and winter. 

 Pregnant females have been collected in Carter County, Montana in late June; lactating 

 females have been collected in early July, and volant young have been collected in 

 mid-July and early August (Jones et al. 1973); most young in Alberta are born in late 

 June (Schowalter and Gunson 1979). Emerges at twilight to hunt for an initial period of 

 about five hours, after which activity declines; often forages over meadows, around yard 

 lights, and along tree-lined streets. In 1994, this species was detected on the Kootenai 

 National Forest at one site in July, eight sites in August, and seven sites in September 

 (Appendix 3). 



Status: Considered less common in Montana than elsewhere in the United States (Hoffmann and 

 Pattie 1968); uncommon in Glacier National Park (Lechleitner 1967), but the most 

 common bat in Carter County, Montana (Jones et al. 1973). Present in the Idaho 

 panhandle (Groves and Marks 1985). This species was detected on all Districts of the 

 Kootenai National Forest in 1994 (Appendix 4). Not listed by any federal agency. 



Natural Heritage Program rank: G5; not on Species of Special Concern list in Montana. 



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