Deer mice show up across a wide slice of Illinois habitat, from Johnson County in the far south to the Cook and DuPage county preserves farther north. Few mammals in North America range this broadly or fit this many different landscapes, and Illinois’s spread of records reflects that flexibility rather than any single stronghold.
The 74 records logged since 2000 peak in March, April, and October, at 10 each, with the fewest in June. That pattern likely tracks the species’ spring and fall breeding pulses more than anything else, since deer mice can produce several litters a year outside the hottest months.
Most of the records, 65 of the 74, come from iNaturalist, even though this is a mouse that’s notoriously easy to confuse with the white-footed mouse at a glance and usually needs a hand or a trap to identify with confidence. NatureServe rates the species secure across Illinois.
Full species profile
