Unraveling a Mysterious Mark on West Roscoe Street
What began as a quirky urban legend—the so-called “Splatatouille” imprint—has now been given a scientific label. In a study published in Biology Letters, researchers from The University of Tennessee, Knoxville, argue that the famous hole in Chicago’s sidewalk was most likely made by an eastern gray squirrel, not a brown rat as once thought. The imprint, found on West Roscoe Street and nicknamed in a public contest, captivated attention when a comedian circulated a photo in early 2024. It was subsequently removed during pavement repairs, but the mystery endured in public imagination.
The Scientific Approach to a Serendipitous Track
Lead author Dr. Michael Granatosky and colleagues examined a curated list of 37 mammal species observed in Chicago. They whittled this down to eight plausible candidates that could account for the imprint’s features, including the brown rat, eastern gray squirrel, eastern chipmunk, and muskrat. With the physical artifact unavailable for study, the team relied on publicly available photographs of the imprint and compared them with measurements taken from prepared museum skins of the candidate species.
From Measurements to a Likely Culprit
Although no single species matched the imprint perfectly, the analysis found that eastern gray squirrels, fox squirrels, or muskrats had the closest anatomical proportions. Among these, the eastern gray squirrel emerged as the most probable victim. Their higher prevalence in Chicago compared with the other contenders provided additional support for this conclusion.
A New Name for a Well-Worn Tale
In their discussion, the researchers proposed rechristening the imprint as the “windy city sidewalk squirrel,” a title that better reflects its likely origin and the evidence at hand. They also considered how a wet concrete surface, coupled with a dropped squirrel, could yield a slightly larger footprint than one might expect, while daytime squirrel activity in wet conditions offered a plausible timing scenario for the event.
What Do the Footprints Tell Us About Tracing History?
Beyond the playful mystery, the study underscores a core principle of science: traces left by living beings can be ambiguous and are often shaped by the environment. The team noted that the lack of a visible tail or definitive hairs on the imprint is unsurprising—conservation of fine-scale features is rarely perfect in concrete, and some details are lost or dispersed over time. The investigation illustrates how paleontology and forensic science turn to indirect evidence, measurements, and comparative anatomy to reconstruct events from traces that are long since altered by weather, human intervention, and chance.
Why It Matters—And How It Highlights Scientific Process
While the topic may appear whimsical, the study highlights the rigor required to interpret traces. “When we step in mud, or concrete in this case, things spread out, there are many layers within the track, and it’s a hard science,” Granatosky notes. The research demonstrates that even lighthearted curiosities can illuminate broader scientific principles—from how to evaluate footprint data to understanding how urban wildlife interacts with human habitats.
Looking Ahead
The Chicago sidewalk imprint may be a relic of decades past, but its story continues to teach. The researchers’ method—comparing multiple candidates, using museum specimens, and accounting for environmental conditions—offers a blueprint for future trace-analysis puzzles. In an era of rapid urbanization and growing interest in urban ecology, such investigations remind us that even the smallest marks on a sidewalk can open a window into the natural history happening just outside our doorsteps.
