MEADOW MOUSE 



the zone of dwarfed plants and thick mosses. The large 

 townsendii is abundant in the luxuriant river-bottom meadows 

 along the Willamette and Columbia rivers. Some of the 

 forms of californicus are found in regions of scanty rainfall, 

 but one must locate grass-land near streams before the Mouse 

 can be encountered in any abundance. 



In the forests of the Rocky Mountains and other ranges 

 species such as mordax may be encountered in scattered 

 localities where there are no meadows, and the Mice live in 

 the same situations as the White-footed Mice, under logs and 

 rocks. I have never encountered large colonies under these 

 conditions, however. 



The large members of the subgenus Aulacomys, living in the 

 higher zones of the Rocky and Cascade Mountains and in 

 Alberta, are not as abundant, if my experience with macropus 

 may be taken as a criterion, as the forms of the subgenus 

 Microtus. They are found about cold mountain streams and 

 are large enough to pull out of the average mouse-trap. 



On the open plains region east of the Rocky Mountains, 

 and on the sagebrush plains between these mountains and 

 the Cascade-Sierra system, one finds the Meadow Mice of 

 the subgenus Pedomys {Microtus) and genus Lagurus. Some 

 of these Mice are rare and very local, found only in small, 

 scattered colonies. Throughout most of this territory the 

 commoner species of the other groups of Meadow Mice are 

 found as well. 



The Meadow Mice of the subgenus Chilotus are more sub- 

 terranean in habit than their relatives. Microtus oregoni 

 oregoni, the only species of this group I have observed, makes 

 small runways just under the surface of the ground, under the 

 sod, and seldom comes out on top of the ground. During 

 several years of trapping in a region where they are found, 

 the only specimens taken were caught in traps set in these 

 subterranean paths. The close thick pelage of these Mice is 

 another indication of a highly modified, subterranean exist- 

 ence. 



Meadow Mice are very prolific and wherever conditions are 

 favorable doubtless have several litters of young annually. 

 The number of young to a birth varies somewhat with the 

 group and the subgenus, but is probably from four to eight. 

 Plagues of Meadow Mice have been recorded both in the 



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