Chicago’s beloved sidewalk imprint, long hailed as the tragic splat of a rat in wet concrete, was almost certainly left by a squirrel instead.
The quirky landmark in Roscoe Village, which drew crowds, offerings, and even a plaque before its removal in April 2024, likely came from an eastern gray squirrel or fox squirrel that took an unlucky tumble. Researchers used measurements from photos of the hole and compared them to eight local rodent species, finding a 98.67% chance it’s squirrel-made. The work, published in Biology Letters, highlights how easy it is to misidentify animal traces — and turns a fun urban legend into a lesson in science.
The ‘Rat Hole’ exploded online in January 2024 after comedian Winslow Dumaine posted about it on X, formerly Twitter. For years, locals had passed the rodent-shaped dent without much fuss, but the viral fame brought pilgrims leaving coins, flowers, and tiny tributes. Dubbed ‘Splatatouille’ in a public contest, it became a city icon, complete with a nearby softball team mascot. But experts like Seth Magle from Lincoln Park Zoo’s Urban Wildlife Institute had early doubts, noting squirrels are daytime critters more likely to encounter fresh concrete than nocturnal rats.
To settle the debate, the team measured features like snout-to-tail length, head width, and digit size from 25 online photos of the imprint. They pitted these against museum specimens of brown rats, mice, chipmunks, muskrats, and squirrels. Statistical tests, including discriminant function analysis, showed the hole matched squirrels best — 50.67% eastern gray, 48% fox. Muskrats were a distant third at 1.33%. Key clues: longer limbs and digits than a rat’s, plus no bushy tail imprint, which is rare in concrete anyway.
The study suggests the squirrel probably fell from a nearby tree that once stood there, a common mishap for urban squirrels. “This investigation underscores the challenges of attributing a trace to the tracemaker,” the authors write. “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, but accessible to anyone with an interest in understanding the natural world.”
Citations: Biology Letters. DOI: 10.1098/rsbl.2025.0343
