Chicago’s infamous ‘rat hole’ likely caused from another critter, researchers say

Oh no, not the rats!

A team of researchers believes they have dispelled the myth surrounding the infamous “rat hole” of Chicago, a quirky landmark in the Windy City.

But wait—this rat hole isn’t what it seems. It wasn’t some gloomy bar from the Prohibition era catering to the city’s legendary gangsters, nor was it a cluttered tenement overflowing with debris.

In reality, it was the full-body imprint of a hapless animal that became stuck in freshly poured sidewalk concrete in the Roscoe Village neighborhood roughly 20 or 30 years ago. The mark bears a striking resemblance to a splayed rat, complete with detailing such as small claws, limbs, and even a tail.

The rat hole gained widespread attention early last year when comedian Winslow Dumaine shared a photo on X that went viral. Tourists began flocking to the site, leaving coins and various eccentric items around the impression as offerings.

This influx of visitors raised eyebrows among local residents, leading to complaints. By April 2024, someone decided to fill the impression with what appeared to be plaster. The city later removed the cement and transported it to City Hall-County Building, leaving behind a plaque to commemorate the rat hole at its original location.

Researchers from the University of Tennessee, New York Institute of Technology College of Osteopathic Medicine, and the University of Calgary published their findings in the journal Biology Letters, concluding the rat hole likely originated from a squirrel or muskrat rather than a rat.

To reach their conclusions, the researchers examined images of the rat hole online and compared its measurements with specimens from museums of animals typically found in Chicago.

The presence of forelimbs, hind legs, and a tail ruled out birds, snakes, frogs, and turtles, narrowing it down to mammals. The delineation of claws further whittled the possibilities down to rats, mice, squirrels, chipmunks, and muskrats, according to the study.

The creature’s elongated forelimbs, third digits, and hind feet were too substantial for a rat, yet aligned with measurements of Eastern gray squirrels, fox squirrels, and muskrats. The researchers posited that the Eastern gray squirrel is the most plausible culprit, given that it is commonly found in the Chicago area.

Other experts had already hinted at the possibility of a squirrel being behind the imprint. Given that cement is usually wet during daylight hours and that rats are nocturnal, the lack of any tracks suggests that a squirrel may have miscalculated a jump or slipped from a branch, landing in the wet cement, as speculated in the study.

Furthermore, while the imprint showed no evidence of a bushy tail, the researchers explained that hair often doesn’t retain enough stiffness to leave a deep, well-defined impression, making it rather unexpected to find such an outline.

“We therefore advocate for renaming the specimen the ‘Windy City Sidewalk Squirrel’ — a title that better reflects its likely origins and aligns with the evidence we have gathered,” the study authors stated.