A mouse is a small animal that belongs to one of numerous species of rodents. The best known mouse species is the common house mouse. It is also a popular pet. The American white footed mouse and the deer mouse also sometimes live in houses.
Although mice may live up to two and a half years in the lab, the average mouse in the wild lives only about four months, primarily owing to heavy predation. Cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of insects have been known to prey heavily upon mice. Nevertheless, because of its remarkable adaptability to almost any environment, and its ability to live with humans, the mouse is regarded to be the second most successful mammalian genus living on Earth today after humans.
The word mouse and the word muscle are related. Muscle stems from musculus meaning small mouse, possibly because of a similarity in shape. The word mouse is a cognate of Sanskrit mus meaning to steal, which is also cognate with mys in Old Greek and mus in Latin.
All species of mice are native to Eurasia and Africa, where they range from lowlands to mountaintops. The five species in the subgenus Pyromys are found in Sri Lanka, India, Pakistan, and mainland Southeast Asia. Much of their range originally consisted of open grasslands or grassy patches in forests.
Mice are common experimental animals in biology and psychology primarily because they are mammals. They are the most commonly used mammalian model organism, more common than rats. The mouse genome has been sequenced, and virtually all mouse genes have human homologs. They can also be manipulated in ways that would be considered unethical to do with humans. A knockout mouse is a genetically engineered mouse that has had one or more of its genes made inoperable through a gene knockout.
There are other reasons for why mice are used in laboratory research. Mice are small, inexpensive, easily maintained, and can reproduce quickly. Several generations of mice can be observed in a relatively short period of time. Mice are generally very docile if raised from birth and given sufficient human contact. However, certain strains have been known to be quite temperamental. Mice have the same organs in the same places, just different proportions.