Wild mice, rats, shrews, and even frogs voluntarily use running wheels in natural habitats without any food reward, according to a study published in the journal Proceedings of the Royal Society B. Researchers Johanna Meijer and Yuri Robbers from Leiden University installed 24-centimeter running wheels in a green urban area and a closed dune location, recording over 200,000 animal visits via night-vision cameras and motion sensors to challenge decades of assumptions that captive rodents run on wheels purely due to cage-induced stress or boredom.
Challenging Assumptions About Captive Rodent Behavior
For decades, biologists operated under the assumption that captive mice ran on wheels simply because cramped cages made them bored, stressed, or crazed. According to Leiden University researchers Johanna Meijer and Yuri Robbers, who published their findings in the journal Proceedings of the Royal Society B, this hypothesis had never actually been tested in the wild. To find out if free-roaming animals would ignore running wheels, the team placed a 24-centimeter wheel inside a small, open structure in a green urban area.
The structure featured motion sensors and a night-vision camera to record how local wildlife responded. While food was initially placed near the wheel to attract animals, the researchers later removed the food entirely to test whether the creatures would still use the apparatus. The setup allowed animals up to the size of a rat to freely enter and leave the enclosure.
Three-Year Field Results From Urban and Dune Locations
Following the initial success in the urban green space, researchers installed a second wheel in a nearby dune area that was closed to the public. According to NBC News coverage of the experiment, these two field sites operated for more than three years, resulting in a dataset of over 200,000 animal visits and more than 12,000 analyzed video clips. Wild mice proved to be the most enthusiastic participants, accounting for 88 percent of all recorded wheel-running events.
Other species also interacted with the equipment. Shrews, rats, and frogs set the wheel spinning during the observation period. NBC News noted that while snails and slugs triggered movement, their haphazard crawling was excluded from formal analysis. Some individual mice demonstrated remarkable endurance, with one recorded running continuously for an astonishing 18 minutes.
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Some young mice observed using the wheels during the study were too young to have ever experienced the initial food rewards placed near the setup, indicating they used the equipment purely for the activity itself.
Why Wildlife Runs Without Food Rewards
When researchers removed the food source from the testing stations, total visits dropped significantly, but the fraction of visits that included actual wheel running increased. According to the study authors, this shift implies that wheel running can be experienced as rewarding even without an associated food reward. Seasonal variations also emerged in the data, with wild mice running more frequently during warmer months and peaking in late spring and summer when young, energetic mice are most active.
In 2016, behaviorists Georgia Mason and Hanno Würbel noted that a natural behavior in wild animals does not preclude an exaggerated version of that same behavior from becoming abnormal in captivity, much like pacing can grow out of normal locomotion. Subsequent research, including a 2019 review and a 2025 study on male mouse neural circuitry, has continued to examine how rodents are motivated to run and play.
Frequently Asked Questions
Do wild animals actually use hamster wheels?
Yes. Research published in the Proceedings of the Royal Society B demonstrated that wild mice, rats, shrews, and frogs voluntarily use running wheels placed in natural environments.
Why do mice run on wheels if there is no food?
According to researchers Johanna Meijer and Yuri Robbers, wheel running can be experienced as rewarding on its own, independent of food incentives.
Did scientists only study mice?
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