Mice Run Wheels for Fun: Study

The next time you see a lab mouse going nowhere fast on an exercise wheel, don't feel so sorry for him. Recent research has found that mice actually enjoy running on the wheel, and even wild mice will do it.

A study recently published in the Proceedings of the Royal Society details how researchers set out to determine if wheel running is simply a behavioral "artefact of captivity" among lab mice, or if the animals will purposely seek out the activity even in the wild.

To determine this, researchers from Leiden University in the Netherlands set a number of exercise wheels outside in regions where wild mice are prevalent, and monitored them with motion-activated cameras. According to the study, they did not have to wait long before their first wild mouse discovered the "joy" of wheel running.

"When I saw the first mice, I was extremely happy," said Johanna Meijer, a brain electrophysiologist who studies biological rhythms in mice, the New York Times reports. "I had to laugh about the results, but at the same time, I take it very seriously. It's funny, and it's important at the same time."

The researcher took about 12,000 video clips of different wild mice running in all, showing even some return visitors to the wheels.

"If wheel running is indeed caused by captive housing, wild mice are not expected to use a running wheel in nature," the authors of the study write. "[Yet] here we show that when running wheels are placed in nature, they are frequently used by wild mice, also when no extrinsic reward is provided."

Some critics of the study argue that while wild mice might be curious about the wheels and run on them for a bit, captive lab mice are actually running the wheels as a necessity to resolve stress from captivity or to maintain an active body.

However, the report details how the researchers found even average bout lengths of wheel running among wild mice matched those of their captive counter-parts.

The study was published in the Proceedings of the Royal Society on May 21.