The western water shrew is the largest of Colorado’s shrews and one of its most rarely recorded. Open occurrence databases hold only 18 Colorado records for it, mostly museum and survey captures rather than photographs of so aquatic and secretive an animal.
A diver in cold mountain streams
Unlike its dry-land cousins, this shrew makes its living in and around fast, cold water. It dives after aquatic insects, larvae, and tiny fish along clear mountain streams and their banks, and stiff fringes of hair on its hind feet trap enough air that it can briefly skitter across the surface. Colorado’s 18 records are scattered across 12 counties, with Mesa County holding the most and the rest in ones and twos through Gunnison, Eagle, Larimer, and the western and southern mountains wherever suitable streams run.
Bound to water, active all year
The handful of records fall in midsummer, when streamside survey work happens, but the water shrew neither migrates nor hibernates. It holds to its cold streams straight through the winter, and the seasonal gaps in the record are gaps in observation, not in the animal’s presence.
Status in Colorado
NatureServe ranks the western water shrew S4, apparently secure, in Colorado, and it is native here. In photographs it is nearly identical to the American water shrew, so which drainage an animal is found along is usually the first clue to which of the two it is.
Full species profile
