Habitat
Washington: moist habitats with soft earth free of sod; lower elevation ravines with deep soils, much vegetative surface litter (logs, leaves), and big-leaf maple and other plants; less commonly in lakeshore willow thickets; rarely in drier habitats (Dalquest 1948). Oregon: most common in riparian alder and alder-salmonberry thickets; less commonly occurs in mature and immature conifer, riparian hardwood, sitka spruce-salal, skunkcabbage marsh, wet pasture, headland prairie, and headland scrub habitats (Maser et al. 1981); also montane areas with low cover of lichen and few snags, and Douglas-fir forest (see Carraway and Verts 1991). California: redwood, Douglas-fir, and yellow pine forests and forest edges, usually near streams (Ingles 1965). Constructs runways near surface of duff layer and deeper but shallow burrows, usually near streams. Less fossorial than other moles.
Ecology
Seems to be more social than other insectivores; may travel in loose bands (Dalquest and Orcutt 1942, Maser et al. 1981). Population density in favorable habitat estimated at 12-15/ha (but up to 247/ha after removal of all other small mammals) (Dalquest and Orcutt 1942).
Reproduction
Most breeding occurs from early March to mid-May, but even then only a few percent of specimens are in breeding condition. Length of gestation not known. Litter size varies from 1-4 young. Newborns altricial. Reported to have an XO system of sex determination.