Differences From Wild Rats
See also: Brown rat and Laboratory ratWhile domesticated rats are not removed enough from their wild counterparts to justify a distinct subspecies (compare Canis lupus familiaris), there are significant differences that set them apart, the most apparent is colouring. Random colour mutations may occur in the wild, but these are rare—most wild R. norvegicus are a dark brown colour, and fancy rats may be anything from white to cinnamon to blue.
Behaviourally, domesticated pet rats are tamer than those in the wild. They are more comfortable around humans, known to seek out their owners while roaming freely. They have decreased reactions to light and sound, are less wary of new foods, and have better tolerance to overcrowding. Fancy rats are shown to mate earlier, more readily, and for a longer period of time over their lifespan. Also, domesticated rats exhibit different behaviours when fighting with each other; while wild rats almost always flee a lost battle, caged rats spend protracted amounts of time in a belly-up or boxing position. These behavioural traits are thought to be products of environment as opposed to genetics. However, it is also accepted that there are certain underlying biological reasons for why some members of a wild species are more receptive to domestication than others, and that these differences are then passed down to offspring (compare Domesticated silver fox).
Domesticated rats have a longer lifespan than that of wild rats. Because domesticated rats are protected from predators and have ready access to food, water, shelter, and medical care, their average lifespan is around 2 years, in contrast to wild R. norvegicus, which average a lifespan of less than one year. However, wild rats generally have larger brains, hearts, livers, kidneys, and adrenal glands than laboratory rats. The fancy rat and wild rat also both face a multitude of differing health concerns—the former is at risk of developing a pneumococcal infection from exposure to humans, while the latter may harbour tapeworms after coming in contact with carriers like cockroaches and fleas.
Read more about this topic: Fancy Rat
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