The Chicago Rat Hole is many things: a site of pilgrimage, a city landmark, and perhaps even an artwork that shows how we coexist with nature. But primarily, it is a rat-shaped indent printed into a slab of concrete in North Chicago’s Roscoe Village neighborhood.
Now, a new scientific analysis led by the presumably well-tenured ecologist Michael C. Granatosky at the University of Tennessee, Knoxville, has shown that the Rat Hole is, in fact, a squirrel imprint. Having been dubbed “Splatatouille” in homage to the 2007 Pixar rat animation, the Rat Hole may need a new name. “Splat by Scrat,” perhaps.
The Real History of the Rat Hole
The Rat Hole had, according to local residents, been marked into the sidewalk for several decades, but after being shared online in early 2024, hole-related fervor hit fever pitch.
Passersby dropped coins, figurines, and, for some reason, estrogen pills into a makeshift shrine that built up from the hole. Sadly, for pilgrims and pedestrians alike, the slab containing the hole was removed by city authorities later in the year, although council officials have suggested it will be displayed elsewhere.
The interest and passion about the Rat Hole had never extended to sober academic analysis. But the authors of the new study, published in Biology Letters, thankfully saw it as “a rare neoichnological analogue for interpreting trace-producing behaviours” (which roughly translates as ‘a good opportunity to study how animals splat themselves into concrete’). This analysis revealed the true culprit behind the Rat Hole.
Read More: Medieval Squirrels Served as First Ancient Hosts of Leprosy
Who Made The Rat Hole?
The team used images of local Chicago wildlife saved using the app iNaturalist in their analysis. They narrowed the list of potential street artists down to 37 species, after ruling out candidates that lacked the four limbs and tail clearly visible in the rat hole. The team further cut out feral hogs (too rare), bats (too many wings), and beavers (too large).
With obvious false tracemakers removed, the team turned to careful anatomical measurement to winnow their list further. Using the analysis tool ImageJ, they processed internet images of the Rat Hole to extract measurements of the culprit’s snout-to-tail base length, forelimb length, third digit length, hindpaw length, head width, tail base width, and 2.5 cm from tail base width.
Next, they derived these measurements from prepared museum skins of potential animals, making sure to include specimens from a range of ages and from both sexes.
The team then fired a salvo of statistical firepower at their paving slab problem. This testing showed that the only three species whose body plans matched the Rat Hole were the Eastern grey squirrel, the fox squirrel, and the muskrat. Further interrogation of the model used to analyze the hole’s shape showed that the likelihood of the Rat Hole being left by an Eastern grey squirrel was 50.67 percent, the chance it had been left by a fox squirrel was 48.00 percent, and the remainder (1.33 percent) suggested a muskrat marker.
Not a Rat but a Squirrel
The team noted that, although they didn’t incorporate density modeling into their analysis (presumably the relevant academic budgetary authorities intervened), Eastern grey squirrels are far more common than either muskrats or fox squirrels in Chicago. This factor makes the former species the most likely creator of the Rat Hole. They added that the squirrel’s bushy tail would likely not have been imprinted into the concrete, explaining why the hole’s author remained misidentified for so long.
Ultimately, the team hopes their analysis will have an impact beyond the neoichnological community.
“We hope this work — in spite of (or perhaps more specifically, because of) its inherent frivolity — resonates with both the public and the scientific community,” they wrote.
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