The related term squirrel cage may also refer to:

• a squirrel cage rotor
  Squirrel cage rotor
  A squirrel cage rotor is the rotating part used in the most common form of AC induction motor. An electric motor with a squirrel cage rotor is termed a squirrel cage motor.- Structure :In overall shape, it is a cylinder mounted on a shaft...
  
  
• a squirrel cage fan or blower
  Centrifugal fan
  A centrifugal fan is a mechanical device for moving air or other gases. It has a fan wheel composed of a number of fan blades, or ribs, mounted around a hub. As shown in Figure 1, the hub turns on a driveshaft that passes through the fan housing...
  
  

Hamster 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.

Most wheels are constructed of steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 or plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

, 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. The earliest dated use of the term “hamster wheel” located by the Oxford English Dictionary

Oxford English Dictionary

The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

 is in a 1949 newspaper advertisement.

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). If a hamster is arching its back when it runs on a wheel, the wheel needs to be replaced with a bigger wheel.
The 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

Environmental enrichment (neural)

Environmental enrichment concerns how the brain is affected by the stimulation of its information processing provided by its surroundings . Brains in richer, more stimulating environments, have increased numbers of synapses, and the dendrite arbors upon which they reside are more complex...

. 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

Canyon mouse

Canyon Mouse , is a gray-brown mouse found in many states of the Western United States and northern Mexico. Its preferred habitat is arid, rocky desert. It is the only species in the Peromyscus crinitus species group....

, 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.

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 (26.7 mi) for rats, 31 km (19.3 mi) for wild mice, 19 km (11.8 mi) for lemmings, 16 km (9.9 mi) for laboratory mice, and 8 km (5 mi) for gerbils. 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.. This makes running wheels a popular type of enrichment (even an essential one, in the view of some ) to the captivity conditions of rodents.

The reliability with which hamsters and other rodents will use a running wheel has made wheel-running one of the most widely used markers of activity and wake time in circadian rhythms research.

A related toy, the hamster ball

Hamster ball

Hamster balls are hollow spheres made of clear plastic into which hamsters, gerbils, degus and other small rodent pets are placed, allowing them to run around outside their cages without the risk of running away, getting lost under furniture or in walls...

, 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.

External links

Information about hamster wheels