CHICAGO (WGN) A recent study has cast doubt on the long-held belief that the famous “Chicago Rat Hole” is the work of a rat, suggesting instead that it might not be a rat’s doing at all.

The research, published by The Royal Society, involved a detailed comparison of the “Chicago Rat Hole” dimensions against those of eight rodent species frequently found in the Chicago area.

The findings of the study indicate that the imprint is more likely to have been made by a squirrel.