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Wild County

A Brief Survey of Cook County Mammals


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From a distance it looked like a fawn-colored puppy, possibly dumped on the shoulder by a passing motorist. It wasn't until I drove past it that I realized it was a half-grown red fox, romping nonchalantly at the noon hour within feet of heavy traffic on the Kennedy Expressway near Wilson. I exited, backtracked, and drove past it again, easing onto the shoulder a couple dozen feet ahead of it. The fox dove like a kitten for something in the weeds. Only when I backed up to within ten feet of it did it finally scamper up the embankment and disappear into the brush.

"Red fox are not uncommon in Cook County, although it's a little unusual to see one in such an urban setting," says David McGinty, a biologist with the Cook County Forest Preserve District. "We get quite a few spottings out in the more open, less developed areas. Gray fox are also fairly common, although they tend to stay in the more wooded areas. Coyotes have become well established in some of the forest preserves, and you can sometimes hear them calling at night."

A live sighting of a red fox in the city was apparently a rare stroke of luck. Much of what McGinty and other area naturalists learn about Cook County's wild mammal population is gleaned from road kills. These crushed corpses probably provide the best clues to what mammals live in a region, which explains why motorists with an interest in animals often display what might seem a ghoulish interest in them.

"Right now the raccoon is the major road kill, but in the spring you'll see a lot of beaver road kills, particularly along the Des Plaines River and the other waterways," says Ed Lace, director of the Sand Ridge Nature Center, which is west of Calumet City. "This is when the young beavers start moving out in search of new water, where they can start colonies."

Long extinct in Cook County, beavers started showing up again in the early 1960s--neither McGinty nor Lace is quite sure whether they were reintroduced or simply came down the river on their own. Beavers are now found throughout the watercourses of the less developed parts of the county, and rank right up with garbage-eating raccoons and garden-browsing white-tailed deer as nuisances. "They like to chew on home owners' ornamental trees," says Lace.

Along the roads where road-kill beavers turn up, road-kill mink are sometimes encountered. The best adapted to developed areas of the Mustelidae, or weasellike mammals, the mink is holding up quite well here, says Lace. Any cattail marsh with muskrat, the mink's principal prey, will likely hold a mink or two. Lace adds that long-tailed and short-tailed weasels, which are also partial to roaming near water, are occasionally spotted.

Unlike the county's reptiles and amphibians, which are victims of overcollecting and loss of habitat, many mammals are doing pretty well. "Urban and suburban areas offer a more protected environment," says Lace. "Fewer dogs and cats run free now, so there are not many predators. People who landscape their homes provide protected habitat. The water-retention basins required for flood control also provide good habitat."

Deer are the most notorious exploiters of this protected suburban habitat. Woodchucks are also common near forest preserves and occasionally do damage to residential gardens. Striped skunks are also well established through most of the county, often denning under porches.

But the continuing destruction of habitat is taking its toll on some mammals. "Bats, of which we have several species, are becoming less common because their roosting sites are disappearing," says Peter Dring, director of the Little Red Schoolhouse Nature Center, in the middle of the Palos and Sag Valley forest preserves. "They like barns, which are being torn down; attics, which are no longer being built into houses; and dead trees. The polluting of ponds and spraying for mosquitoes is also robbing them of much of their food source."

The southern flying squirrel, which dens in standing dead trees, is also becoming more scarce, as is the Franklin's ground squirrel, which requires an open prairie habitat. Dring and Lace have both recorded scattered reports of road-kill badgers. The Mustelidae family's premier burrower, the badger was never common in Cook County, though it's still fairly common in the Indiana Dunes area.

Lace says the 13-lined ground squirrel, which superficially resembles the eastern chipmunk, is still fairly common here, though the fox squirrel is losing ground to the bigger, tawnier, and more aggressive gray squirrel. Harder to track because of their small size and secretiveness are moles and shrews. The eastern mole and the short-tailed shrew are abundant in spots, but several species--including the star-nosed mole and the least shrew--are probably present, although no sightings have been recorded recently.

The forest preserve naturalists I interviewed, a Northwestern University biology professor, and the field guides are unanimous in contending that otters have been extinct in this area since the 19th century. What, then, were the two large, sinuous creatures that I saw swimming, floating, and diving in the Northwestern University lagoon almost daily over several weeks during the summer of 1983? The creatures never came closer than 15 to 20 feet from shore, but seemed otherwise unconcerned with the activity on the banks. "Look, otters," I said to various bicyclists, strollers, and fishermen who happened by. Those who knew otters typically agreed the animals certainly weren't beavers or muskrats. Lace and Dring doubted my report but conceded they might have been released from captivity or escaped some zoo.

Notwithstanding the red fox on the Kennedy and whatever it was I saw in the lagoon, wild mammals do not typically present themselves to the casual observer, though even unobservant city dwellers are aware of the handful of urban mammals that are diurnal and relatively unafraid of people-- gray squirrels, eastern cottontail rabbits, eastern chipmunks. The nocturnal raccoons and opossum are commonly seen waddling away from Dumpsters, freezing in the glare of headlights, or facing down Fido during his nightly walk. During particularly cold winters, deer mice and white-footed mice enter houses if they can, sometimes turning up in traps set for house mice.

Those who want to spot the odder mammals should explore fields and woods just after a light snow. Following tracks in the snow may lead to a den or burrow, or even the animal itself. Lace believes the best time to see them is when the weather is bad. "Unusual weather, be it a rain or a snowstorm, brings out the seldom-seen mammals."

Art accompanying story in printed newspaper (not available in this archive): photos/Bruce Powell.

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