Illinois sits at the far northern edge of the cotton mouse’s range, and NatureServe now lists the state’s population as presumed extirpated, meaning it’s likely gone from Illinois even though the species remains numerous across the Southeast. The 15 historical records here, tied to Cache River State Natural Area, Chautauqua National Wildlife Refuge, and Upper Mississippi River refuge lands, are a thin trace of a population that may no longer exist.
What records there are cluster heavily in April, with a smaller handful in May and December. Given how few reports exist, and how easily this large-footed, nocturnal mouse gets confused with other Peromyscus deer mice, that pattern isn’t strong enough to describe a season, just a snapshot of when the historical sightings happened to occur.
The species is still classified as native to Illinois rather than introduced, a status that reflects its documented history in the state rather than a current, confirmed presence. Anyone hoping to find a cotton mouse in Illinois today would be looking for a species the record book already treats as functionally gone.
Full species profile
