I love simple, unusual experiments that lead to surprising results, especially if I get to watch films with wild animals in new situations.
The research I will describe below was more of an experiment in the colloquial meaning of the word – finding out what will happen if… we place a running wheel in the wild.
Running wheels are usually placed in the cages of small pets or lab animals like mice or hamsters (rats don’t like them very much) to provide them with some entertainment and an opportunity to exercise. Sometimes the wheels are also part of the experiment, for example when studying how exercise affects animal health. However, some people believe that running in wheels is an unnatural behaviour, a sign of stress and boredom or even mental illness resulting from life in a cage.
However, if that was true, wild animals wouldn’t use a running wheel. Right?
A couple of yours ago researchers from the Netherlands decided to check that. They placed one running wheel in a green urban area and one in an area in the dunes not accessible to the public. Next to each wheel they installed a movement sensor and a camera. All this was placed in a cage-like construction that prevented animals larger than rats from entering.
Can you guess what animals were caught on camera “running” on the wheel? They were mainly mice, but also rats and shrews and even frogs and slugs! And that is when only counting animals that made the wheel move consistently in one direction (snails usually caused haphazard movement of the wheel and they were not counted as “runners”).
If a slug was on a wheel, I guess that it was moving on it mainly because it didn’t know how to get off. But for mice the situation looks different.
Like in the laboratory, usually young mice ran in the wheel. And while in most recorded cases mice ran on the wheel for less than a minute, quite often (20% of the cases) it was longer. One mouse even ran for 18 minutes! Mice never walked on the wheel, but always ran, and the maximum speed was higher (5.7 km/h) than that of any mouse recorded in the laboratory (5.1 km/h). In addition, sometimes mice (but also rats, shrews and frogs) would leave the wheel only to re-enter it within minutes to continue running (or jumping).
Therefore, it seems that wheel running can actually be a voluntary behaviour that is likely internally rewarding.
This research reminds me of how much fun I had as a kid on a giant hamster wheel in an amusement park. Definitely more fun than on a treadmill in a gym, even though that was also a voluntary activity…
The recordings of the wild animals on the wheel can be found here.
Photos and information: Meijer and Robberts (2014)
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