Chicago's Famous Rat Hole Wasn't Made by a Rat

Chicago's famed "rat hole"—a rodent-shaped impression in a North Side sidewalk that drew crowds and offerings from locals—wasn't actually made by a rat, the New York Times reports. Dubbed "Splatatouille," the mysterious hole captured the city's imagination, with many believing a rat had wandered onto wet concrete, become trapped, and was later removed after it died, cementing its mark in the city Orkin has named America's "rattiest" 10 years running. The rat-shaped impression was believed to have been made years ago, but a comedian's social media photo of it brought new attention last year, the Guardian reports. However, a new analysis published in Biology Letters suggests it wasn't actually a rat that met its end there, though the lead researcher tells LiveScience that he, too, assumed the impression was made by a rat when he first saw it.

Unable to access the original concrete as it's since been replaced, evolutionary biomechanist Dr. Michael Granatosky and his team at the University of Tennessee turned to online photos and used objects left in the hole for scale. Comparing the dimensions to museum specimens of local rodents, they concluded with near 99% confidence that the imprint wasn't made by a rat, but likely by a tree squirrel—either an eastern gray or fox squirrel, both common in Chicago.

While perhaps disappointing to residents who once paid their respects to the dearly departed rodent by leaving offerings inside the hole, the squirrel scenario is more plausible, given squirrels are active during the day (when wet concrete would be much more likely, given construction workers' schedules) and squirrels often climb trees (there were no footprints around the animal-shaped impression, meaning the animal likely fell onto the slab from above).