Washington’s occurrence databases hold 2,080 southern red-backed vole records, compiled from iNaturalist and GBIF, most frequently recorded from the state’s forested mountains rather than its dry interior. That data is shaped heavily by when and where small-mammal surveys have run, not a map of true abundance.
Forest everywhere but the dry middle
The southern red-backed vole occupies forest across nearly the whole state, from the Olympic Mountains through the Cascades and into the northeastern highlands, but it drops out of the dry Columbia Basin interior almost entirely. What it needs isn’t a particular mountain range so much as cool, damp ground: deep moss, rotting logs, and a shaded understory that keeps the soil surface moist even in summer. Cleared or sun-baked ground rarely holds the species for long.
A vole that spreads fungus through the forest floor
Much of this vole’s diet is fungus rather than green plants, including the below-ground truffles that many conifers depend on for a healthy root system. By digging up and eating those fungi, then moving on and depositing spores elsewhere, the vole helps spread the same fungal partners the forest’s own trees rely on. It’s a small, easy-to-overlook link between a mammal most hikers never see and the health of the timber around it.
Records cluster in summer field season
Reports jump sharply from June through September and peak in August, then drop to a trickle over winter. Red-backed voles stay active through the cold months under snow and leaf litter, so that summer spike says more about when field crews are out running trap lines than about the vole disappearing each winter.
Status in Washington
NatureServe ranks the species S5, Secure, in Washington, and USGS NAS doesn’t list it as nonindigenous here. It’s treated as native across its forested range, a small and rarely noticed part of the understory in the Olympics, Cascades, and northeastern mountains.
Full species profile
