Brown rat reports around Cook County preserves and the Des Plaines River corridor sit within a heavily developed northeastern Illinois landscape. Midewin adds a more rural setting, but roads, buildings, stored food, and drainage routes can connect these sites as readily as natural habitat does.
November holds the largest share of reports, and observations span every month. Reporting effort around populated areas varies widely, so these records don’t measure the size of Illinois’s rat population.
Full species profile
