Hamster wheel

Hamster wheels or running wheel are exercise devices used primarily by hamsters and other rodents, but also by other cursorial animals when given the opportunity. Most of these devices consist of a runged or ridged wheel held on a stand by a single or pair of stub axles. Hamster wheels allow rodents to run even when their space is confined. The earliest dated use of the term "hamster wheel", located by the Oxford English Dictionary, is in a 1949 newspaper advertisement.

Most wheels are constructed of steel or plastic, both of which have advantages and disadvantages. Solid plastic wheels are safer for some types of animals, such as hamsters and hedgehogs, because the animal's feet or legs cannot get trapped and injured between rungs. However, some rodents (e.g. gerbils) will quickly chew and destroy plastic wheels but not steel versions.

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).

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

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. 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.

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