Biology Letters study claims to solve mystery behind Chicago Rat Hole

CHICAGO (WLS) -- The mystery of that infamous Chicago Rat Hole on the sidewalk may be solved!

There was actually research done about it just published in Biology Letters.

Scientists believe that outline is not of a rat - but more likely, a squirrel.

Using the measurements of the imprint, they say the impression resembles a squirrel - stocky and semi-aquatic with webbed feet.

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The Chicago Rat Hole was located near Roscoe Street and Damen Avenue before it was removed.