Hamster wheel



wheels are exercise toys used by hamsters and other rodents. Most of these toys are composed of a runged wheel held on a stand by a pair of stub axles. Hamster wheels allow rodents to run even when their space is confined. The earliest dated use of the term “wheel”, located by the Oxford English Dictionary, is in a 1949 newspaper advertisement.[1]

Preferences
Most wheels are constructed of steel or plastic, both with advantages and problems. Solid plastic wheels are safer for some types of pets, such as hamsters and hedgehogs, because the space between rungs is solid and the animal's feet or legs cannot get stuck between rungs, an injury risk in steel wheels. However, some rodents (such as gerbils) will quickly chew on and destroy plastic wheels, but not steel wheels.

Choice tests with Syrian hamsters (Mesocricetus auratus) have shown that they prefer larger wheels; the animals chose a wheel diameter of 35 cm (14 in) over 23 cm (9 in), which itself was preferred over 17.5 cm (7 in).[2] An arched back is not a natural position for a running hamster, and if a wheel is so small that the animal must arch its back while using it, then the wheel needs to be replaced with a bigger one although the younger Syrians can use a small wheel while they are still smal l.

Hamsters showed no preference between a relatively uniform running surface made of plastic mesh and a surface made of rungs spaced 9 mm apart, though they did prefer the mesh over rungs spaced 12 mm apart, most likely because the wider space between the rungs let the legs slip through sometimes. The hamsters neither preferred nor avoided wheels that had small "speed bumps" installed along the running surface to provide environmental enrichment.[3]

Choice tests with mice have also shown a preference for larger wheels (17.5 cm over 13 cm in diameter) and a preference for plastic mesh over rungs and over solid plastic as a running surface.[4] More acrobatic species, such as the canyon mouse, Peromyscus crinitus, and the deer mouse, Peromyscus maniculatus, can develop preferences for wheels that force the animals to jump, such as square wheels or wheels with hurdles along the running surface.[5] [6] [7]

Use by animals
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.[8] Hypotheses to explain such high levels of running in wheels include a need for activity, substitute for exploration, and stereotypic behaviour, but various experimental results strongly suggest that wheel running, like play or the runner's high, is rewarding in and of itself and highly valued by the animals (in the sense that they are willing to work for it - i.e. bar-press or lift weighted doors).[8] This makes running wheels a popular type of enrichment to the captivity conditions of rodents.

Hamsters keep on using wheels even in captivity conditions that include other kinds of enrichment. In one experiment, Syrian hamsters that could use tunnels to access a total of five cages, each containing a toy, showed no more than a 25% reduction in running-wheel use as compared to hamsters housed in a single cage without toys (except for the running wheel).[9] In another study, female Syrian hamsters housed with a nestbox, bedding, hay, paper towels, cardboard tubes, and branches were observed using a wheel regularly, and benefitted from it in showing less stereotypic bar-gnawing and producing larger litters of young as compared to females kept under the same conditions but without a wheel.[10]

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.[11] Such paw wounds rapidly scab over and do not prevent hamsters from continuing to run in their wheel.

Hamster ball
A mouse in green hamster ballA related toy, the hamster ball, is a plastic ball into which a pet can be temporarily locked. The ball allows the pet to freely roll around on the floor to explore and exercise, while preventing escape. Care must be taken to block off stairways, and time in the ball should be limited as more than an hour without access to water could impose dehydration on the animal.