Nearly two years after the “Chicago Rat Hole” became a viral sensation, scientists have weighed in on the debate over what type of critter made the splat.
Researchers analyzed the famous imprint and found the creature responsible was not a rat, but most likely a squirrel.
There’s “a 98.67% likelihood that the ‘Chicago Rat Hole’ was a squirrel,” their paper published in the journal Biology Letters reads.
The rat hole briefly became the city’s hottest attraction in early 2024. People came from across the city to visit the splat in Roscoe Village. Some left offerings like spare change and shots of Malort. Others got engaged and married next to the rat hole. The image became a mascot for a 16-inch softball team and a popular tattoo choice. The hole was even filled in overnight in an act of “ratribution,” but neighbors quickly excavated it.
Michael Granatosky, the lead author of the study and an evolutionary biomechanist at the University of Tennessee, Knoxville, said he also thought it was a rat at first glance. But a closer look at the size of the hands and head made him question who was really responsible.
“It created a zoological mystery,” he told the Sun-Times.
When the image went viral, the Sun-Times spoke with longtime neighbors of the rat hole in Roscoe Village and they said a squirrel created the imprint after likely falling into wet cement from the trees above the sidewalk.
“I don’t want to burst anyone’s bubble or upset anybody, but it’s a squirrel,” said one resident who lived across the street from the imprint for over 20 years.
The imprint’s popularity and the debate over what it was sparked Granatosky’s curiosity.
When he started working on the paper, he planned to visit the rat hole and take a 3D scan of the imprint. But by then, city crews had removed the slab of sidewalk containing the rat hole in the 1900 block of West Roscoe Street. The city promised to preserve and display the imprint, but has yet to announce a permanent home for it.
Without a 3D image, Granatosky and his team compiled several photos of the rat hole from social media and news reports. They used the coins left at the rat hole as scale bars to calculate measurements of the animal. They also studied the most common species in the area and measured mammal specimens in museum collections.
The researchers then ran a statistical analysis that revealed the size and shape of the imprint was likely from a larger rodent, like a tree squirrel. They concluded the rat hole was left by either an eastern grey squirrel or a fox squirrel, both common in Chicago.
Their findings not only solved the mystery, but also told a cautionary tale for paleontology, Granatosky said.
“We can say a lot about dinosaur imprints, but some of those interpretations are filled with errors,” he said. “This imprint is from a couple decades back, we know all the species in the area, it’s really well-preserved, but we couldn’t narrow down to the exact type of squirrel. … Be careful when you make claims about traces.”
Granatosky, whose research focuses on animal locomotion and biomechanics, says he won’t win a Nobel Prize from researching the rat hole. But he hopes it encourages people to be more curious about their environment and the nature living around them. He also hopes his colleagues are inspired to have fun with their research.
“The scientific community shouldn’t be afraid to write these types of articles,” he said. “We should be having fun with science.”