1936] 



MAMMALS OF OREGON 



211 



Distribution and habitat. This large form of the Richardson 

 meadow mouse inhabits the Cascade Range of Washington and 

 Oregon south to Crater Lake, mainly in Boreal zones (fig. 47). In 

 places they come down into Transition Zone but only along streams 

 of cold water from the mountains. They are rarely found far from 

 water and generally inhabit creek banks or flooded marshes. 



General habits. More than any other species of American meadow 

 mice these large, long-tailed, large-footed water voles are semi- 

 aquatic in habits, being excellent swimmers and divers, and depend- 

 ing in part on the water for protection. They generally live in 

 burrows along the banks of the streams or in wet places not far 

 away, and are often seen in daytime swimming across the streams. 

 Their large trails are conspicuous in the grassy places, and are 

 often strewn with stems of grass and sedges cut for food. High up 

 at timber line and along 

 the edges of permanent 

 snow banks they often 

 live in the beds or moun- 

 tain heather or any scant 

 cover that affords conceal- 

 ment. In winter they 

 spread out under the cov- 

 er of snow over slopes 

 that are dry in summer 

 and make bulky nests of 

 dry grass on the surface 

 of the ground in addition 

 to those in the burrows. 



Breeding habits. The 

 mammae are arranged 

 in 4 pairs 2 inguinal 

 and 2 pectoral. Embryos found in females usually number 4 

 to 7 ; 8 is probably the normal maximum. The length of breeding 

 season is not known. 



Food habits. Most of their food consists of the green leaves and 

 stems of grasses, sedges, mountain clovers, and numerous native 

 plants, including the seeds during the short seedtime of the mountain 

 summer. Roots and bulbs and bark form a part of their food, 

 especially under the deep winter snows. Sometimes they are eager 

 for rolled oats used as trap bait and again they will not touch any 

 bait and can be caught only by concealing traps in their runs. 



Economic importance. Fortunately these big mice are not very 

 widely distributed nor more than locally abundant, as they might 

 otherwise do serious damage to the stock range of the higher moun- 

 tain slopes. The open nature of their country generally exposes them 

 to numerous enemies, and their increase is restricted to a point of 

 little consequence. 



MICROTUS RICHARDSONI MACROPUS (MEBBIAM) 



LARGE-FOOTED MEADOW MOUSE ; WATER VOLE 

 Arvico.la (Mynomes) macropus Merriam, North Amer. Fauna No. 5, p. 60, 1891. 



Type. Collected in the Pahsimeroi Mountains, Idaho, at 9,700 feet, by 

 Merriam and Bailey, 1890. 



FIGURE 47. Range of water voles in Oregon : 1, Mi- 

 crotus richardsoni arvicoloides ; 2, M. r. macropus. 



