Like other rodents, hamsters are highly motivated to run in wheels:
It is not uncommon to record distances of 9 km (5.6 mi) being run in one night. Other 24-h records include 43 km (27 mi) for rats, 31 km (19 mi) for wild mice, 19 km (12 mi) for lemmings, 16 km (9.9 mi) for laboratory mice, and 8 km (5.0 mi) for gerbils.
Hypotheses to explain such high levels of running in wheels include a need for activity, substitute for exploration, and stereotypic behaviour. However, free wild mice will run on wheels installed in the field, which speaks against the notion of stereotypic behaviour induced by captivity conditions. Alternatively, various experimental results strongly indicate that wheel-running, like play or the endorphin or endocannabinoid release associated with the ‘runner’s high’, is self-rewarding. Wheel use is highly valued by several species as shown in consumer demand studies which require an animal to work for a resource, i.e. bar-press or lift weighted doors. This makes running wheels a popular type of enrichment to the captivity conditions of rodents.
Captive animals continue to use wheels even when provided with other types of enrichment. In one experiment, Syrian hamsters that could use tunnels to access five different cages, each containing a toy, showed no more than a 25% reduction in running-wheel use compared to hamsters housed in a single cage without toys (except for the running wheel).
In another study, female Syrian hamsters housed with a nest-box, bedding, hay, paper towels, cardboard tubes, and branches used a wheel regularly, and benefited from it as indicated by showing less stereotypic bar-gnawing and producing larger litters of young compared to females kept under the same conditions but without a wheel. Laboratory mice were prepared to perform more switch presses to enter a cage containing a running wheel compared to several meters of Habitrail tubing or a torus of Habitrail tubing.
Running in wheels can be so intense in hamsters that it may result in foot lesions, which appear as small cuts on the paw pads or toes. Such paw wounds rapidly scab over and do not prevent hamsters from continuing to run in their wheel.
A hamster in a running wheel equipped with a generator can generate up to 500 mW electric power, enough for illuminating small LED lamps.
(Hat tip to our Slovenian Guest.)
Maybe someone has been selling them FitBits.
The Turnspit dog was a short-legged, long-bodied dog bred to run on a wheel, called a turnspit or dog wheel, to turn meat. The type is now extinct.