A new study in the journal Biology Letters finds a surprising twist in the viral “Chicago Rat Hole” found on a Roscoe Village sidewalk. Unsurprisingly, it’s not due to a rogue rat! The impression went viral earlier in 2024, enthralling members of the web with its rodent-ish form. To get to the bottom of it, researchers performed a forensic analysis to figure out where the hole came from. They eventually determined that it most likely comes from either an Eastern gray squirrel, a fox squirrel or a muskrat.
The study utilized statistical methods to compare the “Chicago Rat Hole” impression against museum specimens of eight local rodent species. By examining measurements from 25 different photographs of the hole, researchers sought to clarify its origins, taking into account various factors, including the unknown age of the creature that created the impression. After consideration of all of the evidence, the judge ruled against the Board’s first impression assumption that a rat made the hole. Rather, they propose that cumstier urban wildlife is to blame.
Examination of Measurements
They measured other important measurements, including snout-to-tail base length, forelimb length, length of the third digit, length of the hindpaw, head width, and width of tail base. For one, they studied a broader range of body sizes than previous studies. This strategy empowered them to include juvenile and adult animals of both sexes.
The physicochemical and isotopic analysis showed that the mineral proportions of the “Chicago Rat Hole” were virtually identical to those of local squirrels. In particular, Eastern grey squirrel proportions fit at 50.67%, and fox squirrel proportions fit at 48.00%. Regardless, these results seem to suggest an intriguing new contender for the culprit of the indentation – a squirrel, not a rat.
“To account for the unknown age of the ‘Chicago Rat Hole’ tracemaker, we specifically included specimens representing a broad range of body sizes to avoid prematurely dismissing the possibility of the tracemaker being a juvenile or particularly large adult. Individuals from both sexes were also tested, as the sex of the tracemaker was not known.” – study authors
Additionally, researchers noted that squirrels are more active during the day when concrete is typically poured, further supporting their conclusion. As you can see, the study took a rigorous approach. This approach to research developed a deep understanding of the qualities required to produce impressions in sidewalk concrete.
The Role of Environment in Impression Formation
That said, the research shed light on environmental aspects related to how these impressions develop in concrete. Even better, concrete can capture impressions—not just because it’s soft at first, but because concrete is stone. It fails spectacularly most of the time at keeping complex biological features—like fur—in tact. The authors noted that hair does not have the structural integrity that would allow it to create entrained deep and sharp impressions.
“Hair lacks the rigidity to create deep, well-defined impressions in substrates, making it less likely to leave discernible traces under typical depositional conditions. Sidewalk concrete, while capable of capturing impressions due to its initial plasticity, is not an ideal medium for preserving detailed biological features like hair.” – study authors
This was a key piece of information that helped rule out the theory that a rat had made its mark. Concrete, on the other hand, cures rapidly and is much more abrasive. This poses challenges in recovering the finer details often found on small mammals, including rats.
A Call for Curiosity in Scientific Inquiry
The scientists underscored that their study should act as inspiration for the general public to participate in valuable scientific research. They’re passionate about creating a world where everyone has the opportunity to discover and interpret the wonders of nature. Curiosity isn’t just for the professionals, it’s for all of us!
“Our broader aim is to highlight that scientific inquiry begins with curiosity and observation: qualities that are not exclusive to professional scientists but accessible to anyone with an interest in understanding the natural world.” – study authors
That’s what this research seeks to do – to explain the story behind the “Chicago Rat Hole” myth. It further challenges citizens to be active observers of their environment and question the status quo. The results are a healthy reminder of the value of even moderately silly-seeming phenomena to inspire serious scientific inquiry.