For nearly two years, Chicagoans and tourists have treated a small imprint in a Roscoe Village sidewalk like a sacred site. The so-called “Chicago Rat Hole,” which has existed for 20-30 years before becoming an internet sensation, inspired TikToks, fan art, and countless selfies.
Featured VideoHowever, a new study has finally ended the mystery, and the internet’s favorite rat is a rat no more.
In October 2025, researchers announced that the imprint wasn’t made by a rat at all.
AdvertisementInstead, they determined it came from a squirrel that likely slipped from a nearby tree and landed on wet concrete sometime in the early 2000s. Their findings, published by the Royal Society, relied on detailed comparisons between the imprint’s measurements and preserved specimens of eight rodent species.
@rubencordobajr blessing the grave of a god fearing Ratholic #chicagorathole #chicago #rat #rathole #ratpope #hole #fyp ♬ Ameno hatsune miku – Hybrid theorist
Forensic analysis overturns the viral rat myth
The team behind the study wrote, “The ‘Chicago Rat Hole’ is a remarkable full body impression ostensibly created by a brown rat […] crossing fresh concrete in Chicago’s Roscoe Village that became a viral sensation. While the public attributed the mark to a brown rat, no formal analysis had been conducted to confirm its identity.”
AdvertisementResearchers analyzed the imprint’s proportions and found that all of its proportions pointed to one mammal: tree squirrels. According to the study, “analysis indicated a 98.67% likelihood that the ‘Chicago Rat Hole’ was a squirrel.” It was about 50/50 whether it was an eastern grey squirrel or fox squirrel.
Because eastern grey squirrels are more common in the area, the scientists concluded that the species was the most probable match. As the paper explained, “Given local population densities, an eastern grey squirrel likely represents the most parsimonious species-level match.”
The study also reflected on how easily viral stories can blur fact and folklore. “This investigation underscores the challenges of attributing a trace to the tracemaker,” the authors wrote. They added that curiosity itself drives discovery, noting that “scientific inquiry begins with curiosity and observation: qualities that are not exclusive to professional scientists.”
The viral legacy of a concrete mystery
Back in January 2024, the “rat hole” became an overnight phenomenon. Comedian Winslow Dumaine’s tweet, saying he was making a “pilgrimage to the Chicago Rat Hole,” spread quickly, and the location became a quirky tourist stop and even a pseudo-religion, though locals complained.
AdvertisementEven before the new research, online communities debated its true origin. A 13-year-old Reddit post showed an older photo with clearer footprints, suggesting the animal had walked away. Some residents already suspected a squirrel had fallen from a tree in the original Reddit thread.
The internet is chaotic—but we’ll break it down for you in one daily email. Sign up for the Daily Dot’s newsletter here.
AU Deals: Big Price Drops Across All Platforms – Here’s What’s Worth Grabbing