The genus Phenacomys is a group of North American voles. The genus name comes from the Greek for "imposter mouse."
These animals live in forested, alpine and tundra areas, which often include plants of the heath family. They are small rodents with long fur and short ears, legs and tails. They eat green plants, seeds and berries in summer and bark and buds of shrubs at other times. Predators include mustelids, owls and hawks.
Some sources include the tree voles, genus Arborimus, in this genus. At one time, the two species of heather vole were considered to be a single species.
Unusual features in the teeth of Phenacomys voles suggest that the genus may have arisen relatively early within the evolutionary history of voles, probably in early Pliocene Beringia, from an Asian ancestor. The earliest American fossils date from about 1.5 million years ago, and were discovered in present-day Idaho. Similarly aged fossils belonging to two extinct species, P. gryci and P. deeringensis, have been discovered in Yakutia. During the Ice Ages of the Pleistocene, Phenacomys voles lived as far south as Arkansas.
The range of western heather voles is restricted to the Pacific Northwest of North America, specifically Canada and they are the most common rodent in this area of the subfamily Microtinae. The range of western heather voles is not well known but their range is from west central British Columbia then south to California/New Mexico. There is an uncertainty of distribution such that they have even been found in parts of Alaska and this uncertainty is due to limited sample size of captured heather voles because they do not enter traps often.
They tend to use willow as their habitat the most and heather plants less. They also prefer wet meadows and the borders of forests as well as rock, grassland and herbfield habitats when available. There is a variety of habitats for this species but they tend to live in areas with more vegetation cover compared to rock cover. However, it has been reported that a mixture of medium to large rock cover was used as a habitat greater than equal sized or smaller rocks.