The Sidewalk Shrine That Honored the Wrong Rodent
Thousands of people walked out of their way to leave coins, cigarettes, candles, and even estradiol pills in front of a concrete pothole in Chicago’s Roscoe Village neighborhood. They were paying respects to a rat. A study published October 15, 2025 in the journal Biology Letters, led by evolutionary biomechanist Michael Granatosky of the University of Tennessee, Knoxville, puts the odds at 98.7 percent that whatever made the impression was a squirrel, either an eastern gray squirrel (Sciurus carolinensis) or a fox squirrel (Sciurus niger), not a brown rat (Rattus norvegicus) at all. The monument people built in their minds never matched the animal that made it.
How You Reopen a Case With No Body
By the time anyone thought to measure the hole properly, there was nothing left to measure. The city had removed the impression by April 2024, after crowds leaving coins, flowers, candles, cheese, and those estradiol pills turned the sidewalk into a neighborhood disruption. So Granatosky’s team worked the case backward, the way an investigator reads a crime scene after it has already been paved over. They pulled 25 photos from the internet, each one showing the hole next to some everyday object of known size, a coin, a bottle cap. Those objects became rulers. From them the team reconstructed the mold’s real dimensions: nose-to-tail length, forelimb length, the length of the third digit, head width, tail-base width. No guessing, just forensic arithmetic performed on photos nobody took for science. One detail fell into place on its own: the tail in the print reads as thin and ratlike simply because a squirrel’s tail hair is too fine to leave a mark in wet concrete.
The Lineup: Eight Rodents, One Winner
With real numbers in hand, the researchers needed something to measure them against. They examined roughly 50 museum specimens for each of eight candidate species: brown rat, house mouse, eastern gray squirrel, eastern chipmunk, muskrat, white-footed mouse, fox squirrel, and southern flying squirrel. Averaging that many specimens per species kept one oversized rat or one undersized squirrel from tipping the scale. They then ran a discriminant function analysis, a statistical method that sorts a set of measurements into its most probable category, essentially a multiple-choice test for body shape. Tested against the known specimens, the model was accurate 93.5 percent of the time. Run against the Chicago mold, it kept failing the brown rat: the forelimbs, third digits, and hindpaws came out longer than any rat in the collection. The eastern gray squirrel and the fox squirrel did not.
Why a Dying Rat Couldn’t Have Left This
The myth that sent people out with flowers and pills assumed a rat got stuck in wet cement and pressed its whole body in while it struggled and died there. Granatosky’s team argues the physics do not hold up. A rat fighting for its life in setting concrete would leave a mess around it, scattered footprints, drag marks, the record of a struggle, not one clean, undisturbed outline. There were no tracks anywhere near the impression, which points to something faster: a single fall, straight down, no fight at all. Fresh concrete is usually poured during the day, squirrel hours, while brown rats are nocturnal. City squirrels also rack up healed fall injuries at 4.5 times the rate of their rural relatives. A squirrel slipping off a branch and landing in wet cement, sometime in the early 2000s by the study’s rough estimate, stops sounding unlikely and starts sounding ordinary. The researchers have proposed a new name for the spot: the Windy City Sidewalk Squirrel.
What the Study Still Won’t Tell You
Ruling out the rat was the easy part. Choosing between the two squirrels was not. The discriminant analysis split the remaining probability almost evenly: 50.67 percent eastern gray squirrel, 48.00 percent fox squirrel. Both species live around Chicago in roughly similar body proportions, and the imprint held no fur pattern or claw detail fine enough to separate them. As Granatosky told the Chicago Sun-Times, the data could not pin down the exact type of squirrel. The paper points to the eastern gray squirrel as the likelier of the two, simply because it is the more common of the two species in the area, a reasonable lean sitting on top of a near-tie, not a second finding.
The Comedian Who Started It
None of this would exist without one tweet. On January 6, 2024, Chicago-based comedian and writer Winslow Dumaine posted a photo of the hole, and it spread fast enough to pull people across the city to stand over a patch of sidewalk and leave coins, flowers, candles, cigarettes, alcohol, children’s toys, and those estradiol pills. By mid-January, Chicago zoologist Seth Magle of Lincoln Park Zoo had already floated the squirrel theory in public, long before anyone ran a discriminant function analysis to prove it. It took a dead-serious research team until October 2025 to confirm what a local zoologist guessed within days: the squirrel was the correct answer all along. The rat was just the better story while it lasted.