1936] 



MAMMALS OF OREGON 



205 



grassland or dry meadows. Sometimes they are in wet places or 

 along creek banks, but generally are in drier situations than those 

 occupied by the larger, darker Microtus montanus from the lower 

 meadows. 



General habits. Except for their smaller size, grayer colors, and 

 ability to live in drier situations, these little mice are strikingly 

 similar to Microtus montanus. They are ground dwellers, with sum- 

 mer homes mainly underground in burrows and nest cavities, while 

 their little roadways mark the surface in all directions under cover 

 of grass and concealing vegetation. Often they are numerous in 

 meadows and fields, but rarely so excessively numerous as to do con- 

 spicuous damage to forage or crops, or to be frequently seen except in 

 harvest time. 



Breeding habits. The mammae are in four pairs, and embryos 

 show the young to number usually 6 to 8. Breeding continues 

 throughout a long season, 

 and reproduction is rap- 

 id if conditions are fav- 

 orable. 



Food habits. Their 

 food consists mainly of 



reen vegetation, roots, 

 ulbs, and seeds. Sec- 

 tions of cut grass and 

 fragments of plants cut 

 for food and remains of 

 grass tops are found 

 scattered about on their 

 feeding grounds, and the 

 stomachs usually contain 

 green food, mainly, with 

 smaller quantities of 

 white dough from seeds, 

 or soft gray root tissue or sometimes traces of bright-colored flow- 

 ers. They will eat others of their own kind found dead in traps, 

 and seem fond of fresh meat, but apparently do not eat insects. 



Economic status. Owing to their ranging over the dry grassy 

 uplands as well as in the meadows these little mice, when numerous, 

 must do considerable damage to the stock range, reducing its carry- 

 ing capacity in direct ratio to their abundance. They rarely become 

 very numerous, however, as cover is usually not very dense and they 

 are steadily preyed upon by a host of bird and mammal enemies. 



MICROTUS CANICAUDUS MILLER 

 GBAY-TAILED MEADOW MOUSE 



Microtus canicaudus Miller, Biol. Soc. Wash. Proc. 11 : 67, 189T. 



Type. Collected at McCoy, Polk County, Oreg., by B. J. Bretherton, in 1895. 



General characters. About the size and general appearance of nanus but more 

 yellowish with grayer tail. Upper parts in summer bright yellowish gray; 

 lower parts grayish white ; feet grayish ; tail mainly light gray or whitish with 

 a half concealed dusky dorsal line. 



Measurements. Average of typical adults: Total length, 141 mm; tail, 35; 

 foot, 20; ear (dry), 12. 



FIGURE 43. Range of gray-tailed and dwarf meadow 

 mice in Oregon: 1, Microtus canicaudus; 2, M. 

 nanus nanus. Type locality circled. 



