At 116 records, Idaho has decent documentation of this tiny mouse, and the timing tells its own story. Reports climb through spring, peak at 30 in May, and stay strong through June before tapering off, tracking the animal’s busiest breeding and foraging months.
Western harvest mice are barely bigger than a thumb, and they build woven nests low in grass, moving along hidden runways under dense cover rather than crossing open ground. That habit makes them easy to miss, so the grassy edges around Deer Flat and Camas refuges and the Snake River corridor likely hold more mice than the record count alone suggests. One reliable way to tell this species from Idaho’s other small mice is the deep groove running down each upper front tooth, a feature deer mice and voles don’t share.
NatureServe lists it S4, Apparently Secure, in the state, consistent with a native species that’s widespread across the western half of the country.
Full species profile
