Big Brown Bat {Eptesicus ftiscus) 



Description: This species is easily distinguished from other bats on the Northern Great Plains 

 by its large size (only the Hoary Bat is larger). Weighs 16-30 g. Pelage is brown, 

 with hair extending only slightly onto the wing and tail membranes. 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. Hibernacula include 

 caves and mines, buildings (attics) and other man-made structures. Maternity colonies 

 have been found in attics, barns (Swenson and Shanks 1979), and sometimes in tree 

 cavities. Mating occurs in fall and winter. Pregnant females have been collected in the 

 Long Pines, North Cave Hills, and Slim Buttes in late June; lactating females have 

 been collected in early July, and volant young have been collected in mid-July and 

 early August (Andersen and Jones 1971, Jones et al. 1973). 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 13 June at Road Draw Spring #1, Slim Buttes, on 14 June (a 

 lactating female and two adult males were netted) at Reva Gap, Slim Buttes, on 14 June 

 in Ekalaka Hills, on 15 and 16 June near Capitol Rock and in the SE corner of the 

 Long Pines, on 27 September at Pedalower Reservoir and Cabin Spring Reservoir, 

 North Cave Hills, and on 28 September at Dry Creek Reservoir and on the rim crest, 

 at South Cave Hills (Appendix B3). 



Status: Considered the most common bat in southeastern Montana (Jones et al. 1973) and a 

 common species in Harding County, South Dakota (Andersen and Jones 1971). 

 Present year-round in the Black Hills (Turner 1974) and probably the same on the 

 Sioux District. This species has been recorded from Chalk Buttes, Ekalaka Hills, the 

 Long Pines, North Cave Hills, South Cave Hills, and Slim Buttes (Appendix B4). Not 

 listed by any federal agency. 



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

 South Dakota. 



