Latest Developments

Scientists from the University of Tennessee, Knoxville, have concluded that the famous 'rat hole' imprint in Chicago's pavement was most likely created by an eastern grey squirrel, not a brown rat as widely assumed. The study, published on Wednesday, October 15, 2025, in the journal *Biology Letters*, used paleontological tools to analyse the decades-old impression.

Dr. Michael Granatosky, an evolutionary biomechanist and the lead author of the study, stated that the evidence strongly supports the eastern grey squirrel as the animal responsible for the imprint.

Historical and Political Context

The unusual imprint, publicly named 'Splatatouille,' gained significant global attention after a comedian shared a photo of it on social media in early 2024. While the imprint was thought to have been made decades ago on West Roscoe Street, it was removed later in 2024 by city officials due to pavement damage.

The long-standing debate over whether the victim was a brown rat or another animal has now been addressed through scientific inquiry.

Laws/Policy and Governance

While this specific case is an urban curiosity, the study's methodology underscores the importance of scientific rigor in identifying species, a practice crucial for wildlife management and conservation policies in Kenya. For instance, in Nairobi, which boasts a national park within its city limits, accurate identification of urban wildlife is vital for managing human-wildlife interactions and preserving biodiversity.

Stakeholders and Testimonies

Dr. Granatosky noted that the study, despite its lighthearted subject, demonstrates the power of science to address various questions and reveals the inherent difficulty in interpreting traces left by organisms, a fundamental aspect of palaeontology. Edwin Dickinson, an archaeologist at the University of Calgary and senior author of the study, highlighted that the scientific method can be applied to even seemingly frivolous topics.

Evidence/Data

• **Species Examined:** Researchers analysed 37 mammal species observed in Chicago, narrowing down to eight candidates including the brown rat, eastern grey squirrel, eastern chipmunk, and muskrat.
• **Methodology:** Publicly available photographs of the imprint were used to measure anatomical features, which were then compared to measurements from museum skins of the candidate species.
• **Conclusion:** Statistical analysis indicated a 98.7% likelihood that the imprint was made by either an eastern grey squirrel (*Sciurus carolinensis*) or a fox squirrel (*Sciurus niger*).
• **Supporting Factors:** The animal likely fell from a height, consistent with the presence of nearby trees, and the concrete was wet during the day, when squirrels are typically active.
• **Source:** *Biology Letters* journal, published Wednesday, October 15, 2025.

Risks/Implications

While eastern grey squirrels are native to North America, they are considered an invasive species in parts of Europe and South Africa, where they can displace native squirrel populations. In Kenya, brown rats (*Rattus norvegicus*) are a common pest in urban and residential areas, known for spreading diseases and damaging property. Understanding the distinct characteristics and behaviours of different urban rodent species is crucial for effective pest control and public health initiatives.

Unknowns and Controversies

Despite the strong evidence, some 'rat purists' may still question the findings, particularly given the absence of a bushy tail imprint. However, researchers explain that fine-scale details like hair are not typically preserved in concrete.

Timeline and Next Steps

The imprint gained viral fame in early 2024 and was removed later that year. The scientific study confirming its likely origin was published on Wednesday, October 15, 2025. There are no immediate next steps for the physical imprint itself, as it has been relocated to Chicago City Hall.

What to Watch

This study serves as a reminder of the ongoing scientific efforts to understand urban ecosystems. In Kenya, continued research into urban wildlife populations, including rodents and other adaptable species, will be important for managing public health, infrastructure, and conservation efforts in rapidly expanding cities.