1936] 



MAMMALS OF OREGON 



183 



mustaches long, reaching tips of ears ; fur in summer close and dense, in winter 

 longer and softer. Color of adults in summer, upper parts rich cinnamon 

 brown, more or less darkened with dusky hairs ; top of tail dusky brown ; feet 

 and whole lower parts and lower half of tail white or whitish; in winter 

 slightly brighter colored ; immature, plumbeous above, whitish below. 



Measurements. Average of several typical adults : Total length, 193 mm ; tail, 

 96; foot, 21.5; ear (dry), 16. Adult male from Lagunitas, Calif.: Total length, 

 178 mm ; tail, 85 ; foot, 22 ; ear, from notch, 18. Weight, 21.6 g. 



Distribution and habitat. This very dark colored form of the 

 white-footed mouse inhabits the coast region from San Francisco 

 Bay, Calif., to the Columbia River, and east in Oregon to the west 

 slope of the Cascades, except in the upper Rogue River Valley (fig. 

 36). It is mainly an inhabitant of dense forest or chaparral in a 

 humid climate. 



General habits. Whatever is known of the habits of these little 

 forest dwellers has been chiefly gathered by collectors who find them 

 in the morning rounds of 

 their trap lines, usually 

 on or under old logs, on 

 stumps^ in old camps or 

 houses in the woods, or 

 among broken rocks. 

 Sometimes, however, they 

 are caught in traps set 

 under low vegetation, 

 in the marshes, or even 

 among driftwood on the 

 ocean beaches. While 

 primarily woods mice, as 

 often called, they are able 

 to adapt themselves to al- 

 most any habitat afford- 

 ing cover and a food sup- 

 ply. To what extent they 

 climb the tall forest trees is not well known, but they are good 

 climbers and are often caught well up on the branches and trunks 

 of trees, or in the hollows of trunks where they frequently make 

 their nests. In many cases also they build their nests under or in 

 the great fleeces of moss that drape the trees in the coastal forests. 



The mice are so strictly nocturnal as to be rarely seen except 

 when caught in traps or occasionally surprised in their nests in 

 camps or buildings. They can see fairly well in the daytime, but 

 their large, dark eyes are better adapted to the night. 



They do not accumulate fat or hibernate for winter and are active 

 all the year. 



Breeding habits. In this group the females have 3 pairs of mam- 

 mae 2 inguinal and 1 pectoral on 4 widely separated glands. The 

 young, as shown by sets of embryos usually number 4 to 6, but on 

 rare occasions as many as 8 or 9. They are found at all times of 

 year, but mostly from March to October. There are a few records of 

 embryos noted in December, January, and February. Under favor- 

 able conditions of food and protection several litters may be pro- 

 duced in a year, but under unfavorable conditions there may be none. 

 Usually the mice are common but not present in great numbers. 



FIGURE 36. Range of three subspecies of deer mice in 

 Oregon : 1, Peromyscus maniculatus rubidua; 2, P. 

 m. sonoriensis; 3, P. m. artemisiae. 



