In the wheel of life, mice are really enjoying themselves.
Dutch researchers placed hamster wheels in natural settings to conduct an experiment into whether mice would actually run on the wheels for their own enjoyment. And it turns out, they did.
Johanna H. Meijer and Yuri Roberts, of Leiden University Medical Center in the Netherlands, placed the exercise wheels outdoors in a yard garden and dune area, and were surprised to find multiple mice who chose to run on the wheels as well as other animals.
"Mice and some shrews, rats and frogs were seen to leave the wheel and then enter it again within minutes in order to continue wheel running. This observation indicates that wheel running may well be intentional rather than unintentional for these animals," the pair wrote in their study, called "Wheel Running in the Wild."
They did not immediately respond to ABC News' request for comment.
The researchers said that they were inspired to look into whether mice enjoyed running on the wheels after controversy over mice being held captive for experiments at research universities.
"Wheel running is often used in the laboratory for triggering enhanced activity levels, despite the common objection that this behaviour is an artefact of captivity and merely signifies neurosis or stereotypy," they wrote.
"In a time when lifestyle in general and lack of exercise in particular are a major cause of disease in the modern world, research into physical activity is of utmost importance. Our findings may help alleviate the main concern regarding the use of running wheels in research on exercise," they said.