In a remarkable study conducted in 2014, a group of Dutch researchers embarked on an intriguing experiment to observe animal behavior in a natural setting. They placed a hamster wheel outdoors to determine if wild mice would engage with it similarly to their captive counterparts.
Surprisingly, not only did the wild mice take to the wheel, but various other creatures such as frogs, rats, shrews, and even slugs showed interest. This suggests that the instinct to run on wheels may stem from a natural inclination to play, rather than merely being a behavior observed in captivity.
Creating Opportunities for Play
For many years, biologists believed that mice ran on wheels in captivity out of boredom or stress. However, researchers Johanna Meijer and Yuri Robbers from Leiden University questioned this assumption. They decided to test whether free-roaming animals would ignore the wheel or embrace it.
"If wheel running is a behavior linked to captivity, we wouldn't expect wild mice to use a running wheel in their natural habitat. To our knowledge, this had never been tested before. Our findings show that wild mice frequently engage with running wheels placed in nature," the researchers noted.
To gather data, the scientists set up a wheel in a backyard and used an infrared camera to monitor animal interactions. The wheel was designed with a small entrance to allow small animals in while keeping them safe from larger predators. Initially, they placed food near the wheel to attract wildlife but later removed it to see if animals would continue to use it.
The results were captivating: a variety of animals interacted with the wheel. Mice were the most enthusiastic participants, but shrews, rats, and frogs also engaged with it. Frogs occasionally activated the wheel by jumping, while slugs explored its surface rather than running. Nevertheless, the mice actively used the wheel for extended periods.
Encouraged by these results, researchers set up another wheel and camera in a nearby dune area, leaving it in place for a year and a half. Over three years, they recorded more than 200,000 animal visits and analyzed over 12,000 video clips of animals interacting with the wheels. Remarkably, one mouse was observed running for an impressive 18 minutes!
When the food was removed, the number of visits decreased significantly but did not drop to zero. Some young mice, who had never experienced food rewards, still used the wheel simply for the joy of it.
This raises intriguing questions about why animals engage in wheel running without any rewards. Researchers propose that this behavior might be linked to a metabolic reward system, acting as a response to hunger or other foraging-related stimuli. Additionally, it may satisfy their curiosity or innate desire to play. The fact that fewer animals visited the wheel when food was absent, but those that did were more likely to run, supports this theory.
The Motivation Behind Wheel Running
The study prompts an important inquiry: what drives animals to run on wheels when there's no obvious reward? One theory suggests a connection to a metabolic reward system, where movement serves as a natural stimulus related to foraging or hunger. Alternatively, it might fulfill a fundamental need to explore or play.
Interestingly, the research indicated seasonal variations in wheel usage, with mice being more active during warmer months, particularly in late spring and summer. This pattern aligns with the increased activity of young mice, suggesting that juveniles may be more curious or energetic.
Ultimately, it appears that multiple motivations influence this behavior. One thing is certain: mice utilize wheels not just in captivity but also in the wild, indicating that this behavior satisfies a natural instinct rather than creating an artificial need. This insight could have significant implications for pet owners and researchers working with lab mice.
This article was originally published in January 2023 and has since been updated with additional information.