1936] 



MAMMALS OF OREGON 



215 



are undoubtedly eaten when obtainable and may furnish an im- 

 portant part of the food within the tunnels. 



Economic status. In a desert country with scant cover and food 

 these mice can rarely attain even local abundance. They are not 

 likelv to come in contact with agricultural interests and can have 

 but little effect on abundance of native forage plants. 



FIBER ZIBETHICUS OSOYOOSENSIS LORD 

 ROCKY MOUNTAIN MUSKBAT; PAMUSE of the Piute 



Fiber osoyoosensis Lord, Zool. Soc. London, Proc., p. 97, 1863. 



Type. Collected at Osoyoos Lake, British Columbia, by J. K. Lord, in 1861 

 or 1862. 



General characters. Large ; ears and eyes small ; hind feet large and heavily 

 margined with bristles; front feet small; tail long, laterally compressed and 

 nearly naked ; fur dense and 

 soft when prime, half con- 

 cealed by long, coarse, shiny 

 guard hairs. Upper parts in 

 fresh pelage, glossy dark 

 brown ; hips blackish ; sides 

 russet brown ; belly cinnamon, 

 paler on throat and anal re- 

 gion. In worn pelage often 

 faded and much paler. Young 

 more sooty brown than adults. 



Measurements. Average of 

 10 adults: Total length, 589 

 mm; tail, 271; foot, 83; ear 

 (dry), 18. Weight of adults 

 approximately 2 to 3 pounds. 



Distribution and habi- 

 tat. This large, dark, 



northern muskrat ranges, FIGURE 49. Range of two subspecies of muskrats in 

 -P armfV>oT.r, "Rr>if ioVi Pr* Oregon : 1, Fiber zibethicus occipitaUs; 2, F. z. 



irom SOUtnern rJritlSn CO- osoyoosensis. Type locality circled. 



lumbia to northern New 



Mexico, including in its range northeastern Oregon east of the Cas- 

 cades (fig. 49). Specimens from the Malheur Valley are clearly 

 referable to it rather than to mergens of Nevada, while those south 

 of the Malheur Valley are perhaps nearer to the paler mergens, al- 

 though not typical. For present purposes, all of the specimens 

 examined from east of the Cascades in Oregon can be treated under 

 the single form osoyoosensis, rather than to include only intermedi- 

 ates in a form not typical in the State. 



Muskrats are more or less common in the Columbia, Snake, Des- 

 chutes, John Day, Malheur, and Owyhee drainages and also in the 

 isolated Malheur Lake Basin, and one was taken in 1896 by C. P. 

 Streator at Shirk, west of the Steens Mountains. They have not been 

 taken in the Klamath or Pit River Valleys nor in Summer, Abert, or 

 Warner Lake Valleys, although these great lakes and tule marshes 

 seem admirably adapted to their requirements and very similar to 

 the Malheur Lakes where they abound. Altitude and zonal condi- 

 tions seem to have little influence on these aquatic mammals, while 

 food supply and suitable habitat are the main factors in their 

 original distribution and abundance. 



General habits. Muskrats are mainly aquatic in habits, swimming 

 and diving with great skill, getting most of their food from under 



