Family CRICETIDAE 



159 



(125-150 mm.) ; hind foot H-}i inch (15-18 mm.) ; ear from 

 notch about y? inch (11-14 mm.). 



The skull is 22.0-24.5 mm. (about %-\ inch) long; it?; width 

 across the zygomatic arches just behind the infraorbital plate is 

 less than 12 mm. Dental formula: I 1/1, C 0/0. Pm 0/0 

 M 3/3. 



The deer mouse may usually be distinguished from the more 

 abundant white-footed mouse on the basis of the following com- 

 bination of characters: hind foot less than 19 mm. long, rather 

 than 19 mm. or more as in the white-footed mouse; tail less 

 than 60 mm. long, rather than more than 60 mm.; total length 



Fig. 89. — Deer mouse. 



of adults less than 155 mm., rather than more; width of skull 

 across zygomatic arches just behind the infraorbital plate less 

 than 12 mm., rather than more; length of skull 14.5 mm. or less, 

 rather than more. 



Life Histor>^ — The deer mouse is an inhabitant of the 

 prairie and is most abundant in areas of ungrazed and uncut 

 grass and forbs, such as grow along railroad and highway rights- 

 of-way, in extensive weedy fields, and along fencerows, fig. 2. 

 It is at home under a haystack or a corn shock, among dry 

 weeds along a fence, or under a rock or board. 



The nest, usually underground, is approximately the size of a 

 man's two cupped hands. It is formed of a coarse outer frame- 



