HOFFMEISTER b MOHR: ILLINOIS MAMMALS 7 



Species Not State-Wide in Occurrence. — Four kinds of 

 mammals — the masked shrew, pigmy shrew, least weasel, and 

 meadow vole — are essentially northern animals and seem to be 

 limited in Illinois to localities within the northern half of the 

 state. The red squirrel, which may still occur in Illinois, al- 

 though it is not listed among the species known to be in this 

 state, is also a typically northern mammal and, if present, would 

 be expected only near the northern border. 



Ten species of Illinois mammals are primarily southern in 

 distribution. Six of them — the southeastern bat, big-eared bat, 

 golden mouse, cotton mouse, rice rat, and wood rat — occur in 

 the southern fourth of the state. Two of them — the gray bat 

 and the swamp rabbit — occur a little farther northward, and 

 two others — the evening bat and the eastern pipistrel — occur 

 over most of Illinois. 



Six Illinois species are predominantly western in distribution. 

 If only the Illinois distribution of these mammals were consid- 

 ered, they might be regarded as northern animals. However, 

 these animals are prairie or plains species and follow the west- 

 ern prairie habitats which extend eastward across the northern 

 half of Illinois. Three species — the badger, the thirteen-lined 

 ground squirrel, and the Franklin's ground squirrel — occur in 

 Illinois in only the northern half, but two species — the western 

 harvest mouse and the white-tailed jackrabbit — are restricted 

 in this state to the northwestern corner. The sixth western 

 species — the plains pocket gopher — is unique among Illinois 

 mammals in that the remnant colony in the state is now geo- 

 graphically isolated and is distinct in color from its closest rela- 

 tives. This colony occurs in a few counties of Illinois and ad- 

 jacent counties of Indiana, in an area bounded on the north by 

 the Illinois and Kankakee rivers. 



For several species of mammals our knowledge of their total 

 range or their range in Illinois is scant. One of these species is 

 the introduced roof rat, which is common in the South but which 

 in the North is found sporadically in only a few areas, usually 

 in cities. Another species, the Indiana bat, is known from a 

 very few scattered localities, ami until more records become 

 available we will have no clear picture of its range. The south- 

 eastern shrew also has a poorly known distribution; it is re- 

 corded from southeastern United States and from a tew local: 

 ties in Illinois ami Indiana. 



