American water shrews turn up across Idaho more often than most small mammals in this dataset, 174 mapped records concentrated near the Deer Flat and Camas national wildlife refuges and along the Snake River corridor, wetland and river habitat that matches the cold, clean streams this diving hunter depends on.
Reports build through late spring and peak sharply in July, with 58 records that month alone, before falling off by fall. Since this shrew is active in the water year-round, that midsummer spike more likely reflects when people are out along creeks and refuge trails than any seasonal surge in the animal itself.
USGS NAS treats the species as native to its mapped Idaho range. The relatively high count here, compared to sparse totals for many of Idaho’s other shrews, suggests refuge wetlands and the Snake River system offer some of the state’s more reliably surveyed habitat for this genuinely hard-to-spot swimmer.
Full species profile
