mountain vole
Range: The mountainous regions of northwestern United States extending eastward to central Colorado and southward below the northern borders of Arizona and New Mexico.
Habitat: Valleys and grassy meadows seldom lower than the Transition Zone.
Description: A small sturdy rodent with short tail, total length 5½ to 7½ inches. Tail 1½ to 2½ inches. This is a very short tail for a rodent of this size, amounting to only about a fourth of the total length. Color, grayish brown to black above; underparts lighter to a silvery gray. This is but one of many species found in southwestern mountains. The Mexican vole and the long-tailed vole are two which share its range. They are quite similar in appearance and their life histories also are much the same.
In several ways this heavy-set rodent resembles the pocket gopher. The small ears and eyes as well as the short tail are all reminiscent of that animal. Like many other rodents, voles are quite prolific. From four to eight young are born in a litter. The number of litters each year depends to a great extent on the altitude. They have been recorded in the Canadian Zone, where the summers are too short to permit the rearing of more than one litter. In the Transition Life Zone they commonly bear two litters and sometimes more each year.
These are the small rodents which most people call “field” or “meadow” mice. In the prairie states this genus is well known for its habit of congregating under shocks of small grain and corn. Here they build their nests and temporarily live in peace and plenty. When the shocks are taken from the field, they are rudely evicted from their snug shelters to fall prey to the farmer’s dog or to face the prospect of building a new home before winter descends upon them. In the West, too, this “field mouse” makes itself at home in agricultural areas, but its native haunts are the natural meadows in mountain valleys. Here they build tunnels in the tangled growth of grass, and excavate shallow burrows in the soft earth. Marshy places are particularly to their liking, because they are quite at home in water. Too, the thick cover in these areas gives them considerable protection from their many enemies. A normally high reproduction rate (several litters per year with up to eight young in each litter) coupled with a secretive way of life insures their perpetuation. In cases where a natural balance has been upset, their population can soar to fantastic heights. In one agricultural district in Nevada a survey revealed an estimated 8,000 to 12,000 “field mice” per acre.
Voles do not hibernate. They are active night and day, summer and winter. During winter storms they may remain in their snug nests for a few days at a time, but with the return of clear weather, openings to their tunnels will soon appear in freshly fallen snow.
Western jumping mouse
Zapus princeps (Greek: za, intensive and pous, foot. Latin: princeps, chief)
Range: Western United States from central Arizona and New Mexico to Alaska.