208 



NORTH AMERICAN FAUNA 



[No. 55 



General habits. These rather large, coarse-furred mice, while oc- 

 casionally found in marshes and wet places, seem to prefer the drier 

 uplands and to require less cover than the regular marsh species. 

 Often their little roadways may be seen through the short dry grass 

 or their little heaps of fresh earth where thrown out of their 

 burrows on dry ground. In other respects they are similar in habits 

 to Microtus montanus and townsendii. 



Breeding habits. The mammae of females are arranged as usual 

 in this group in 4 pairs, and the young are usually 4 to 8. Breeding 

 apparently continues throughout the year, since embryos are noted in 

 specimens collected in winter as well as at all other seasons. 



Food habits. Green vegetation, grass, tules, young or ripe grain, 

 roots, bulbs, bark, and a great variety of vegetable foods are eaten. 

 Rolled oats or any grains are eagerly taken as trap bait, and fre- 

 quently the mice caught in traps are eaten by their more fortunate 

 relatives. 



Economd status. In Oregon these mice are not very widely dis- 

 tributed nor generally very numerous, so their economic importance 

 is slight, but they inhabit fertile valleys where favorable conditions 

 of food and coyer might at any time result in great increase of 

 numbers and serious injury to crops and fruit trees. 



MICROTUS MORDAX MORDAX (MEBBIAM) 

 ROCKY MOUNTAIN MEADOW MOUSE 



Arvicola (Mynomes) mordax Merriam, North Arner. Fauna No. 5, p. 61, 1891. 



Type. Collected at Sawtooth (or Alturas) Luke, on east slope of the 

 Sawtooth Mountains, Idaho, (altitude 7,200 feet), by Merriam and Bailey, 

 1890. 



General characters. Size medium; tail long; ears conspicuous above fur; 

 hip glands rarely noticeable even in old males; fur long and soft in winter 

 pelage, thin and harsh in summer; color in summer coat, back brownish gray, 

 sides olive gray ; lower parts whitish ; feet gray ; tail indistinctly bicolor, dusky 

 above, soiled whitish below. In winter lighter gray above, with clear gray 

 sides ; whiter below with light gray feet and sharply bicolor tail. 



Measurements. Average of typical adults: Total length, 382 mm; tail, 66; 

 foot, 22; ear (dry), 13. 



Distribution and habitat. These long-tailed meadow mice, which 

 inhabit practically the whole Rocky Mountain region, reach their 

 western limit in Oregon along the east slope of the Cascades and in 

 the Siskiyous and occupy all of the mountains of the eastern part 

 of the State high enough for a trace of Canadian Zone (fig. 46). 

 Along the banks of cold streams they descend with other species of 

 mammals and many plants as intrusions into Transition Zone, but 

 primarily they are mountain animals. They live mainly along 

 stream banks or in mountain meadows where for most of the summer 

 there is an abundance of water. 



General habits. While partial to creek banks and cold water 

 when available, these little mountain dwellers will remain for con- 

 siderable time in grassy places that have become thoroughly dried 

 out in summer. In winter they scatter out under cover of snow with- 

 out regard to water and seek their food in the thickets and woods 

 and seem to delight in the cover and protection of old logs and brush 



