212 



NORTH AMERICAN FAUNA 



[No. 55 



General characters. Slightly smaller than arvicoloides; upper incisors less 

 projecting; colors much the same or slightly grayer. 



Measurements. Type, an adult female : Total length, 220 mm ; tail, 71 ; foot, 

 26; ear (dry), 12. Of adult male topotype: 218; 68; 29; 12. 



Distribution and habitat. These large mice are found in the 

 higher Kocky Mountains of Montana, Wyoming, Utah, Idaho, and 

 northeastern Oregon, in the Blue Mountain section. There are speci- 

 mens from the Wallowa Mountains, the Baker Range, and Straw- 

 berry Butte, all from Canadian and Hudsonian Zones (fig. 47). 

 They live mainly along mountain streams and in mountain meadows 

 or marshes. 



General habits. In no important manner do their habits differ 

 from those of arvicoloides, from which they are at best barely dis- 

 tinguishable. Their economic importance is not great and relates 

 mainly to mountain grazing problems. 



MICROTUS ORBGONI OREGONI (BACHMAN) 

 OREGON CREEPING MOUBE 



Arvicola- oregoni Bachman, Jour. Acad. Nat. Sci. Phila. 8 : 60, 1839. 



Type. Collected at Astoria, Oreg., by J. K. Townsend, in 1836. 

 General characters. Small, form rather slender ; ears short ; tail medium 

 length; fur short and smooth, without long hairs; side glands inconspicuous 



in males; tubercles on soles 

 only five ; color of upper parts 

 dusky brown from a mixture 

 of black and yellowish hairs ; 

 lower parts dusky, lightly 

 washed with dull buffy; feet 

 dusky ; tail blackish, but 

 slightly lighter below. 



Measurements. Adult male 

 topotype: Total length, 140 

 mm; tail, 42; foot, 17; ear 

 (dry), 9. 



Distribution and habi- 

 tat. These little groum 

 mice range west of the 

 Cascades from Pugei 

 Sound to northwest* 

 California and cover all oJ 

 Oregon west of the highei 

 part of the Cascade ranj 



(fig. 48) . They occupy the dense forests as well as the brushy and o 

 grassy areas of the uplands and dry slopes, seeming to avoid th< 

 marshes and wet bottoms. 



General habits. As the smooth fur, short ears, and little eye 

 suggest, these mice are largely burrowers, with habits similar to 

 those of the eastern pine mice. In the mellow woods soil where they 

 seem most at home they burrow just below the surface in Ion" 

 tunnels, often pushing up the surface in little ridges similar to those 

 made by moles, but smaller. Under a dense cover of old grass and 

 leaves they often merely push up the plant layer and make their tun- 

 nels as trails over the surface of hard ground but in all cases insist 

 upon ample protection from above. Some of their little burrows are 



FIGURE 48. Range of creeping and pygmy, mice in 

 Oregon : 1, Microtus oregoni oregoni; 2, M. o. 

 bairdi; 3, M. pauper rimus. Type localities circled. 



