First Verified Documentation of a Fisher in Illinois Since the American Civil War

Pekania pennanti Exerblen (Fisher) are mustelids that mainly occupy forested habitats across northern North America. After European colonization, Fisher distribution was halved due to extensive trapping, logging, and habitat conversion for agriculture. Now Fishers are expanding into many suitable portions of their historical distribution, aided by active reintroduction programs, albeit with uneven success. Illinois is one part of the midwestern U.S.A. in which Fishers have not yet reestablished themselves, with the last known individuals being documented in the 1850s. Here we report the first verified Fisher in Illinois since that time, killed by a vehicle collision in Rockford, Illinois. This three-year-old male is of unknown origin, but likely from the nearest self-sustaining population in Wisconsin (~190km away). We discuss this finding in the context of what is known of Fisher’s recent expansion and their ability to colonize other portions of midwestern North America.