This paper intended to test whether would mice would run on a wheel if they found one, to try and determine if this was a natural behavior or a stress response in captivity. They put a wheel in a protected little box with a camera that took pictures any time the wheel turned, and tallied up how often it was used by what.
Mice were, happily, the most common users of the wheel, and their patterns of use indicated they were doing so voluntarily once they figured it out.
But the second most common users.
Those were slugs.
I would not have guessed this in a thousand years. I am delighted.
