In 2009, neurophysiologist Johanna Meijer set up an unusual experiment in her backyard. In an ivy-tangled corner of her garden, she and her colleagues at Leiden University in the Netherlands placed a rodent running wheel inside an open cage and trained a motion-detecting infrared camera on the scene. Then they put out a dish of food pellets and chocolate crumbs to attract animals to the wheel and waited.
Wild house mice discovered the food in short order, then scampered into the wheel and started to run. Rats, shrews, and even frogs found their way to the wheel—more than 12,000 animals over 3 years. The creatures seemed to relish the feeling of running without going anywhere.
Source: Even in the Wild, Mice Run on Wheels, an article by Emily Underwood.