MEADOW MICE OR FIELD MICE. 



The group or family of mammals known as Field Mice, Meadow Mice, 

 or Voles is of wide distribution, being found over practically the whole of 



No. 10. Nest of Mountain Rat; found on sill under a building, removed 

 to outside and placed on steps in same position with respect to the 

 boards as in its original location; composed almost entirely of 

 shredded sunny sacks. 



the northern hemisphere outside of the tropical regions. Technically it is 

 known as the subfamily Microtiiue, and it is represented in Colorado by 

 four genera, Microtus, comprising what may for convenience be termed 

 the true Meadow Mice; Evotomys or the Red-backed Mice; Phenacomys, 

 the Mountain Voles or False Lemming Mice; and Fiber or Ondatra, the 

 Muskrats. 



Except the Muskrats these are all small, heavy-bodied, short-tailed 

 animals, leading terrestrial lives in grassy places, usually damp by prefer- 

 ence, or in the woods, among fallen logs or about the brush, and in Colo- 

 rado at all elevations from the plains to above 14,000 feet. Their food is 

 largely vegetable, consisting of grasses and other green stuff, as well as 

 seeds and bark. It is by gnawing the bark of fruit trees that much dam- 

 age to orchards is done by these mice. None of the species is known to 

 hibernate. 



Of these four genera the Muskrats are easily distinguished by their 

 large size and general adaptation to a semiaquatic life; and the Red-backed 

 Mice, as their name suggests, by the reddish color of the back. The two 

 remaining genera are more difficult to distinguish from one another, and 

 as a matter of fact the Mountain Voles were for a long time confused 

 with the other Field Mice until Dr. C. H. Merriam discovered that their 

 molar teeth had root^ while the molars of the others were always rootless. 

 The Colorado species of Mountain Voles have a proportionately much 



18 



