The western harvest mouse’s Washington record sits almost entirely east of the Cascades, 327 records led by Walla Walla, Grant, and Whitman counties and running through the Columbia Basin and the Palouse. Juniper Dunes Wilderness Area and the Columbia Basin Wildlife Area anchor its named places, all dry, open, grassy country.
A tiny mouse of grass and grain
Weighing less than a tablespoon of water, the western harvest mouse is one of the smallest rodents in the West, and it lives where grass grows thick. It weaves a ball-shaped nest of shredded blades, on the ground or just above it in dense cover, and feeds on seeds, green vegetation, and insects. That habitat tie explains a record that hugs the shrub-steppe and farm edges of the Columbia Basin, from the L.T. Murray Wildlife Area east toward Lake Roosevelt National Recreation Area.
Active in every month
Harvest mice do not hibernate, and Washington’s reports show activity in all twelve months, cresting in midsummer and again in late fall. Through winter the mice hold to their grass nests, emerging on milder nights to feed on standing and fallen seed.
Status in Washington
NatureServe ranks the western harvest mouse S4, Apparently Secure, in Washington. It is native to the state, and USGS NAS does not list it as nonindigenous here.
Full species profile
