Keen's bat 



c 1980 John [Jova The National Audutjon Society Collection/PR 



Other exterior coverings. Hundreds of females form 

 maternity colonies in which each female produces two 

 young. 



Big brown bats may hibernate in the same build- 

 ing they occupied during the summer, but more com- 

 mon winter quarters are caves and mines. They nor- 

 mally roost singly or in small clusters; however, un- 

 usually large clusters of several hundred individuals 

 were discovered in abandoned mines in Jo Daviess 

 County. 



Rafinesque's Big-eared Bat, Plecotus rafinesquii. As 



its name suggests, this species is easily distinguished by 

 its large, conspicuous ears. An attractive bat, it has 

 bi-colored gray dorsal fur and nearly white underparts. 

 Weighing 'A ounce, it is at home in dilapidated houses 

 and barns but probably uses hollow trees when aban- 

 doned structures are sparse. In Illinois, the distribution 

 of this bat is limited to a few extreme southern coun- 

 ties, where almost all records are from caves and mines 

 during winter. One nursery colony was discovered in a 

 dilapidated cabin in Johnson County, but the bats 

 abandoned this structure after human disturbance. 

 Very few big-eared bats were captured in mist nets set 

 over the Cache River during a statewide research 

 project. 



Big brown bat, 2-3 days old. oavraA saugey 



Females form nursery colonies with six to several 

 dozen adults, each producing a single pup. Males are 

 generally solitary during nursery season and can be 

 found behind loose bark, in hollow trees, or and in 

 buildings. Because of its vulnerability to disturbance, 

 the destruction of its habitat, and its limited distribu- 

 tion in the state, the big-eared bat has been designated 

 a state endangered species by the Illinois Endangered 

 Species Protection Board. FM 



Rafinesque's big-eared bat oavidA saugey 



15 



