Montana’s western water shrew records cluster around cold mountain water, including streams inside Glacier National Park and the forested drainages of Custer-Gallatin National Forest, exactly the fast, clean creeks this diving shrew depends on. A smaller cluster reaches Upper Missouri River Breaks National Monument, showing the species also uses spring-fed tributaries where the prairie meets the river rather than only high alpine streams.
The state logged 140 GBIF records and no iNaturalist observations, in keeping with a shrew that’s genetically distinct from, but nearly identical in the field to, the American water shrew found farther east in Montana; the two overlap enough that geography does more identification work here than appearance. Reports peak in July with 32 records, a summer fieldwork spike rather than a true activity peak, since a metabolism this fast keeps the shrew hunting year-round. NatureServe rates the species Apparently Secure (S4) in Montana, a step below the Secure rank often seen in its more widespread relatives.
Full species profile
