The cinereus shrew, often called the masked shrew, is one of the most widely distributed shrews in North America, and its 173 Idaho records cluster around the Snake River Plain, Craters of the Moon National Monument, and the Morley Nelson Snake River Birds of Prey National Conservation Area. What stands out in Idaho’s data is how dated it is: the most recent confirmed record dates to September 2017, meaning nearly a decade has passed without a fresh confirmed sighting in the state.
Reports peak sharply in July, with 53 of the 173 records, tracking not when this shrew is most active (it hunts nearly nonstop, day and night, all year) but when small-mammal trapping surveys typically run.
NatureServe ranks the species S4, Apparently Secure, in Idaho, and it’s native throughout its mapped range here. Given how common and adaptable this shrew is elsewhere, the stale Idaho data likely reflects a lack of recent survey effort rather than any real decline.
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