The Ermine is the smallest member of the genus in Oregon. It has a long, cylindrical neck and body and short legs, but the tail is relatively short. The head is flattened and somewhat triangular, the eyes are small and slightly protruding, and the ears are rounded. The summer pelage is brown dorsally, usually white or yellowish ventrally; in some individuals the throat and belly are splotched with brown or are entirely brown. In some populations east of the Cascade Range, ermines replace brown summer pelage with a white winter pelage. The tip of the tail remains black at all seasons, an adaptation to trick raptors into striking short.

In Oregon, most Ermine are found west of the Cascade Range, but a few are found in eastern Oregon. Ermines are active throughout the year. Male and female ermines do not associate except during the breeding season, a period when juveniles remain in nests under maternal care.

Photo by Fabio Bretto, Flickr