| Western Heather Voles live in mountains, near or above the timberline. Where high-elevation forests have been clear-cut, they have been seen at lower elevations. Like Eastern Heather Voles, they feed on a variety of vegetation, including leaves, seeds, berries, and the bark of willow and other shrubs. They build summer nests underground and winter nests at ground level, next to a bush, rock, or stump. The nests are made of twigs, leaves, and grass. As many as three litters of 2-9 young are produced a year. Males are aggressive toward each other during the mating season, but several Voles may nest together for warmth in winter. These Voles do not do well in captivity (if they survive trapping), which makes it hard to study them.
Merriam, C.H., 1889. Description of a new genus Phenacomys and four new species of Arvicolinae, p. 32. North American Fauna, 2:27-45.
Mammal Species of the World
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