The house mouse isn’t a Colorado native, but an introduced species that arrived with people and now lives alongside them statewide. Open occurrence databases hold 727 Colorado records, concentrated wherever there are buildings, farms, and towns.
A mouse that lives with people
Carried from the Old World, the house mouse lives closely with people. It thrives in homes, barns, granaries, and city lots and only marginally in wild habitat away from people, and that dependence shows plainly in the record. Sightings cluster in the Denver urban corridor and the settled Front Range of Larimer and Boulder counties rather than in the mountains or open range. Small, gray-brown, and quick, it is set apart from Colorado’s native mice by its near-total attachment to human structures and its faint musky smell.
An indoor season
Its records rise through autumn, into October and November, the time of year when cooling weather pushes mice indoors and into the outbuildings where they get noticed and reported. A prolific breeder that can raise many large litters in a single year, it holds high numbers wherever food and shelter stay steady, which around people they usually do.
Status in Colorado
NatureServe marks the house mouse SNA, not applicable, the standard designation for a non-native species outside the conservation-ranking system. It is neither tracked as a species of concern nor counted as part of the native fauna. It is simply here, and abundant, because we are.
Full species profile
