Few city rats have left their mark on the public consciousness — and the urban landscape — like the rats responsible for the famous “Chicago Rat Hole.” (Pizza Rat is a notable exception.)
But the Windy City’s “rat hole” may not be what it seems.
The new identities of the creatures that made an imprint on the sidewalk when they fell into the freshly poured cement suggest that the culprit is an entirely different resident of the city.
A lot of hype surrounds the Chicago Rat Hole, which was also dubbed “Splatatouille” in a public naming contest.
No one seems to know when the sign first appeared in Chicago’s Roscoe Village neighborhood, but it’s believed to have been there for at least two to three decades. But one tweet from Chicago artist, writer and comedian Winslow Dumaine in 2024. January 6 turned into a social media sensation: “Had to go on a pilgrimage to the Chicago rat hole,” he shared in a post on X along with a photo.
Winslow Dumain
It soon became Chicago’s hottest selfie spot, with people leaving coins and other items — the couple reportedly even tied the knot next to the sign. Complaints from neighbors prompted the Chicago Department of Transportation to remove and replace the sidewalk in 2024. in April
But the main question arose: did the rat really make the mark?
Public curiosity about the imprint prompted Dr. Michael Granatoski, an associate professor of ecology and evolutionary biology at the University of Tennessee at Knoxville, to undertake the study.
“What a great way to get the public interested in nature and the world around them,” he said.
Using a similar method that scientists use to identify the animals responsible for fossilized footprints, but with a high degree of levity, Granatoski and his colleagues conducted the first scientific analysis of the footprint, which was published Tuesday in the journal Biology Letters.
Based on their research, the team was able to completely rule out a rat and found that many signs point to a squirrel as the culprit.
“We wanted to show how difficult it is to draw really good conclusions from these imprints, even when presented with an almost perfect scenario,” Granatoski said.
Rodent line-up
When Granatoski began his research, the public assumption was that a brown rat, commonly found in Chicago, was responsible for the full-body impression. However, the city had already recovered the piece of cement, so it could not be examined directly.
Instead, Granatoski and his team took measurements of the rat’s burrow using images of it, including snout-to-tail, head width, base of tail, and length of recognizable fingers and claws.
The team collected museum specimens of the brown rat, house mouse, eastern gray squirrel, eastern chipmunk, muskrat, white-crowned mouse, fox squirrel and southern flying squirrel and took anatomical measurements of each for statistical comparison. The specimens were of various ages and sizes.
The team’s initial analysis narrowed the results down to an eastern gray squirrel, muskrat or fox squirrel, based on elongated forelimbs and hind paw length, as well as the third digit of each paw, all of which exceeded known brown rat measurements.
A squirrel is seen eating seeds at Crystal Cove State Park in California. – blickwinkel/Alamy Stock photo
A fluffy gray squirrel stops in a park in Maidenhead, Berkshire, England. —Maureen McLean/Shutterstock
“A lot of all the traits together sort of took us down squirrel alley,” Granatoski said. “Squirrels tend to have longer digits because they’re wooden, and that turned out to be a pretty strong trait.
For those wondering why the tail print looks so rat-like, the thin hairs on a squirrel’s tail are unlikely to leave any marks, the study authors said.
Eastern gray squirrels are more common in Chicago than muskrats or leaf squirrels, so the team found a 98.67% chance that the rat hole was actually a squirrel hole, and a 50.67% chance that it was an eastern gray squirrel hole.
A muskrat is pictured on the shore of a lake in Allgaeu, Germany. – Dieter Hopf/imageBROKER/Shutterstock.
Brown rats are commonly found all over the world. – Dieter Hopf/imageBROKER/Shutterstock.
A rat hole by any other name
The findings match what Dr. Seth Magle, senior director of the Urban Wildlife Institute at Chicago’s Lincoln Park Zoo, initially suspected about the imprint. Magle was not involved in the study but was one of the study’s reviewers.
“I mean, obviously, it’s one of the most important scientific studies of our lifetime,” Magle joked. “When I saw this paper, I was a little surprised that someone wanted to go to such lengths to really put this topic to rest, but maybe I shouldn’t, because I think this is the kind of research that really captures the public’s imagination.”
As the Chicago rat hole spread, Magle and his team wondered how the mark was made. They figured the animal had fallen or had to be dropped from a distance because there were no paw prints leading to the imprint, he said.
And there were no drag marks – the animal seemed to have fallen from the sky. Magle has seen many squirrels fall or jump from trees while walking around town. The team also considered that the concrete was likely to be wet during the day, after it had just been poured, and drier at night, hours later. Squirrels are active during the day, while rats are mostly nocturnal.
However, when Magle shared his thoughts with the media during the peak days of the rat hole’s viral fame, he caught fire with his theory, as many held on to the idea that it was a rat and nothing more.
“I feel vindicated that their much more analytical, much more quantitative and precise assessment was consistent with our ecological thinking about what could create such a sign,” Magle said.
The authors of the study suggest that the hole “should be re-christened the Windy City Sidewalk Squirrel,” a name more consistent with its likely origin and more consistent with the available evidence.
But the city may not be so ready to embrace this change.
“With great respect to the scientific community, the Rat Hole is now a part of Chicago history, much like the Sears (Willis) Tower and Comiskey Park (Rate Field),” Ryan Gage, director of public affairs for the City of Chicago’s Department of Streets and Sanitation, said in an email. “We’re not so sure the investigation will lead people to call it something else.”
Although not currently on display, the rat hole awaits a permanent home before it is available for public viewing, Gage said, adding that the concrete slab is safe and intact after it was removed from the sidewalk.
The print is not currently on public display. – Chicago Department of Streets and Sanitation
Dumaine, whose post X initially rallied people around the rat hole, said he agrees it’s a squirrel hole. He applauds the scientists who wrote the paper, though he doubts the discovery will change many people’s names.
“Marilyn Monroe wasn’t her real name, but Norma Jean still won the heart of the world,” Dumaine wrote in an email. “The rodent responsible for Chicago’s rat hole doesn’t have to be a rat to do the same.”
He said the name her in a rat hole, more like a pit of injustice than a cozy squirrel’s nest, made people resonate.
“I think the people who responded positively to the Chicago rat hole were probably caught off guard by the terrible news, the rising prices, the stagnant wages and the brutal winter cold,” Dumaine added. “I think there’s a kinship between the castaways, and celebrating the dead rat was a way of saying that like all reviled creatures, we deserve to be celebrated.”
Life in the urban jungle
Things like the paw prints left in cement and the Chicago rat hole are reminiscent of urban ecology, or the study of how animals, plants and people interact in urban environments, Granatoski said.
When Magle began working in urban ecology nearly two decades ago, he recalled that other scientists weren’t as interested in the field and questioned why he would want to study pigeons, rats and coyotes instead of wading through the Everglades or studying species deep in the forests. However, he often noticed public interest in animals and their behavior in cities.
“I thought, why not study the animals that are out there, where the people are, the animals that are doing things that are important to most people,” Magle said.
Dr. Elizabeth Carlen, a doctoral candidate in the Department of Biology at Washington University in St. Louis, said the imprint embodies the value of using science to answer questions. Carlen, who was not involved in the new study, said she thinks the authors “did a great job of identifying what species made that impression.”
The study reminded her of previous research in which scientists asked “where did this come from?” to determine the basis of the supposed yeti fur or spiral horns believed to belong to a new species of bull.
“While these studies may seem silly because they play into pop-science sensibilities, they give the public a glimpse into the scientific method,” Carlen said. “What if this impression was a fossil? Paleontologists would identify the organism that created the fossil in the same way.”
Meanwhile, the main question is the fate of the Chicago rat hole – the animal that made it.
There is no evidence that the squirrel that fell into the cement left. It was likely dropped by a bird of prey or fell from a tree, then carried away by a predator, removed by someone, or broken in situ – although no remains remain.
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