On the Lookout for Fishers in Illinois

The day in mid-March started out like any other, until a Highway Department employee found something totally unexpected at the side of the road in Rockford. The discovery of a deceased fisher (Pekania pennanti) warranted a call to Conservation Police Officer Joseph D. Roesch who then contacted Illinois Department of Natural Resources (IDNR) District Wildlife Biologist Jeff Horn. Horn, Dr. Chris Jacques, IDNR Wildlife Disease and Invasive Species Manager, and Chris Anchor, Senior Wildlife Biologist at the Cook County Forest Preserve District, confirmed the identification of the fisher, which was a 16.9 pound male.

Anchor then sent the fisher to the Diagnostic Laboratory at the University of Illinois College of Veterinary Medicine for a full necropsy. The results confirmed that the fisher had been killed by blunt force trauma to the head and thorax, consistent with being struck by a vehicle. The necropsy report also noted that the animal was a young, reproductively active male in good body condition.

History of the Fisher in Illinois

Despite its untimely demise, the presence of this animal in Illinois is exciting. Why? This species has not been documented to live in Illinois for a very long time. According to the book Mammals of Illinois (Hoffmeister 1989), specimens of fisher from Illinois are not known to be in any collections, which means turning to historical records to determine if or where they occurred in the state. Hoffmeister noted that Robert Kennicott published a catalog of mammals of Cook County in 1855 that stated that fisher “used frequently to be seen in the heavy timber along Lake Michigan” and in 1859 he wrote that “It [fisher] has been found, within a few years, in northern Illinois, and appear to be an inhabitant of the woods, alone.” Going much further back, Hoffmeister documented that fisher bones were found in middens at the Cahokia Middle Mississippi Site (likely deposited 450 to 800 years ago) and a lower jaw of a fisher was recovered at a Middle Mississippi village archaeological site west of Clear Lake in Cass County.

Graham and Graham noted that both marten (Martes americana) and fisher remains were recovered from peat deposits in northwestern Illinois in Whiteside County. These bones were estimated to be from the earliest middle Holocene (6,000 to 8,000 years ago). Ancient skeletal remains of fishers were also found in other locations in central and southern Illinois, but the Grahams noted that those specimens were collected at or near archaeological sites. They concluded that human trade at the time, rather than natural occurrence in the area, better explained the presence of fisher in those parts of the state.

Where Do Fishers Live?

Most fisher references indicate that this forest-dwelling species lives throughout a broad swath of Canada, but was extirpated from most of their southern range (many of the northern U.S. states) by the late 1800s or early 1900s. They managed to hang on in some states such as California, North Dakota, Minnesota and Michigan and have been reintroduced in others, including Washington, Wisconsin, Pennsylvania and Tennessee.

According to the National Park Service, fishers use uncharacteristically large home ranges for an animal of their size (average sizes of 19 square miles in northern portions of its Pacific coast range), with male home ranges typically being twice as large as those of females. Other sources cite an average home range of about 10 square miles in other parts of its range.

A little closer to home, Wisconsin’s Snaphot Wisconsin project has documented several fisher in south-central Wisconsin. And in 2017, Iowa documented a fisher in Allamakee County in northeast Iowa in what is believed to be the first recorded fisher there since the late 1800s.

Fisher Identification

The fisher is the sole living species in the Pekania genus. Formerly named Martes pennanti, DNA studies in the 2000s indicated that fishers are more closely related to wolverines than to martens, and the name was subsequently changed. They are members of the weasel family Mustelidae, along with weasels, mink, martens and otters. Imagine what the hypothetical offspring of a domestic cat bred with a weasel would look like and you’d probably picture a fisher. Unsurprisingly, they are commonly called fisher cats.

Fishers have light brown to black fur, with white patches on the chest, and long, bushy tails. They have a wide head with a small, pointy snout, and rounded ears. Males are larger than females. On average fishers weigh between 3 to 13 pounds, although their size depends on genetics and the available food supply. They are about 3 to 3.5 feet long including the tail.

These medium-sized carnivores are found in forested areas and inhabit both coniferous and mixed coniferous-deciduous forests. Fishers commonly prey upon small and mid-sized mammals, such as hares, rabbits, squirrels, mice and voles. They also feed on carrion, fruit, insects and birds. Fishers are known for their ability to prey upon porcupines (Erethizon dorsatum). And historically, they likely hunted porcupines in Illinois before both species were extirpated by deforestation and population declines caused by unregulated hunting and trapping. Hoffmeister concluded that porcupines may have been present in Illinois based on early, unsubstantiated claims in Jo Daviess County, Whiteside County and along the Illinois River as well as from the remains of at least 10 porcupines found in a cave in Monroe County in 1967 estimated to be over 2,000 years old.

Reporting Fisher Sightings in Illinois

With fishers present in neighboring states, and with this confirmed fisher in Illinois in 2023, we are likely to see other fishers enter the Prairie State in the future. Over the years, IDNR has received reported sightings of fishers, but without photos, trail cam footage or other documentation sightings cannot be verified. The IDNR encourages people who may have seen a fisher in Illinois who have photos or other evidence to report the sighting to the IDNR. Evidence is necessary to validate the sighting…so don’t forget to send those photos.

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Laura Kammin is a Natural Resources Specialist with the National Great Rivers Research and Education Center. She formerly held positions at Illinois-Indiana Sea Grant, University of Illinois Extension, Prairie Rivers Network and the Illinois Natural History Survey. She received her master’s degree in wildlife ecology from the University of Illinois, Urbana-Champaign.