South Dakota’s plains harvest mouse record is thin but wide: nineteen mapped reports scattered across eleven counties, from Harding in the far northwest to Clay and Union on the Iowa line. No place has more than a handful. For a small, quiet mouse of dense grassy cover, that scatter says more about how rarely anyone looks than about where the mouse lives, and a county without records shouldn’t be read as a county without mice.
Reports run from June into fall, with a modest midsummer crest and a small November rise when harvested fields leave both mice and their sign easier to find. A sample this size can’t bear much interpretation, but the broad calendar at least fits a mouse that stays active whenever the ground isn’t frozen.
NatureServe ranks the mouse S4, apparently secure in South Dakota, and its taste for tall and mixed grass gives it room across much of the state. The refuge country of the northeast, places like Sand Lake and Waubay, holds exactly the kind of dense grassland it wants, even though the mapped records so far tilt west. The gap between where it should be and where it’s been recorded is mostly an invitation to look.
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