Viral ‘Rat Hole’ Likely Actually Not from Rodent’s Body Trapped in Concrete, Researchers Say

The infamous “rat hole,” an apparent imprint of a critter etched into a stretch of concrete in Chicago’s North Side, was likely not created by a rat at all, a new analysis from researchers found.

The makeshift attraction drew scores of crowds — and even a wedding — to the city’s Roscoe Village neighborhood before local officials removed it back in April 2024.

But a research article published in Biology Letters on Wednesday, Oct. 15, states that another common creature, with a slightly bushier tail, was probably behind the iconic indentation.

“While the public attributed the mark to a brown rat, no formal analysis had been conducted to confirm its identity,” researchers wrote. “Using clear anatomical landmarks, we compared measurements from the ‘Chicago Rat Hole’ to eight sympatric rodent species.”

Their analysis “indicated a 98.67% likelihood” that the “rat hole” was actually created by a squirrel.

More specifically, the most likely contenders appear to be an Eastern grey squirrel, fox squirrel or muskrat.

Despite the misunderstanding about its origins, the hole itself transformed a regular piece of ground into a hot spot.

“This seemingly ordinary sidewalk hole quickly inspired a wave of visitors who made pilgrimages to the site, leaving offerings like coins, flowers, figurines and even medication,” researchers noted in Biology Letters. “Though the hole had existed for 20–30 years, it rapidly became a local icon, with a nearby softball team adopting the rat as its mascot. The hole was named ‘Splatatouille’ after a public naming contest.”

Perhaps Chicago residents will never know with complete certainty what local creature was commemorated in concrete, but the memory lasts: A Riot Fest Historical Society Plaque marks the original location, as noted by the Associated Press.

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“While we acknowledge the playful spirit of this investigation, our broader aim is to highlight that scientific inquiry begins with curiosity and observation: qualities that are not exclusive to professional scientists,” the researchers wrote, “but accessible to anyone with an interest in understanding the natural world.”