The cotton mouse’s body is about four inches long. The back has brown fur with black hairs intermixed. The belly fur is gray-white. The top of the tail is the same color as the back while the underside is the same color as the belly. The feet are white.
The cotton mouse may be found in the southern tip of Illinois. It lives in swampy woodlands and related brushy areas, bluffs and upland forests. This rodent consumes mostly insects, slugs, spiders and plant material. It climbs well and can swim. The cotton mouse is believed to breed throughout the year. The average litter size is three or four. The nest is placed above ground when possible. Young are born helpless but are ready to live on their own in about four weeks. Sexual maturity is attained about two months after birth. The status of this species in Illinois is unclear. It was not seen from 1909 until the early 1990s when populations were again discovered. It may have been present but misidentified during this time period, or it may have moved into the state again in the early 1990s.