Colorado’s occurrence databases hold 17,785 records for the southern deer mouse, one of the largest tallies for any single species in the state’s dataset, and virtually all of it comes from GBIF-linked trapping and specimen data rather than casual observation. That volume says more about how thoroughly this mouse has been studied than about how many actually live here.
From shortgrass prairie to the Western Slope
Colorado records trace the same broad habitat range the species uses nationwide: grassland, woodland edge, brush, and farmland rather than one fixed setting. Counts reach from the eastern high plains, where Pawnee National Grassland and Comanche National Grassland preserve the shortgrass prairie cover the mouse favors, clear across the Continental Divide to Western Slope counties like Summit, Pitkin, and Gunnison. Few Colorado mammals turn up in county tallies from the flattest plains to the high country in the same dataset.
Why Boulder County carries a quarter of the state’s records
Boulder County alone holds roughly a quarter of every Colorado record, more than any other county by a wide margin. That imbalance reflects research effort more than mouse density: Boulder is home to long-running university and federal research plots in the foothills and alpine zone west of the city, where small-mammal trapping grids are standard fieldwork and deer mice are typically the species caught most often. Records climb sharply from spring into a peak in August, tracking the short, snow-free window when most Colorado high-country field surveys happen, then fall back through autumn.
Status in Colorado
NatureServe ranks the southern deer mouse S5, secure, and it’s native across its mapped Colorado range. It remains one of the state’s most broadly distributed small mammals, tracked here mostly through the trapping surveys and specimen collections that make its Colorado tally so large.
Full species profile
