A mouse (plural mice) is a small animal that belongs to one of numerous species of rodents. The best known mouse species is the common house mouse (Mus musculus). It is also a popular pet. The American white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus) 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 4 months, primarily due 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, due to its remarkable adaptability to almost any environment, and its ability to live commensally with humans, the mouse is regarded to be the second most successful mammalian genus living on Earth today, after humans.
Mice are sometimes considered harmful pests, damaging and eating crops and spreading diseases through their parasites and feces. In western North America, breathing dust that has come in contact with mouse feces has been linked to the deadly hantavirus. The original motivation for the domestication of cats is thought to have been for their predation of mice and their relatives, the rats.
De-coloration in mice was supposedly first noticed in China by 900 BC, where a white mouse was discovered.The white gene is a recessive gene wich arose from mutation.
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.
Breeding onset is at about 50 days of age in both females and males, although females may have their first estrus at 25-40 days. Mice are polyestrous and breed year round; ovulation is spontaneous. The duration of the estrous cycle is 4-5 days and estrus itself lasts about 12 hours, occurring in the evening. Vaginal smears are useful in timed matings to determine the stage of the estrous cycle. Mating is usually nocturnal and may be confirmed by the presence of a copulatory plug in the vagina up to 24 hours post-copulation. The presence of sperm on a vaginal smear is also a reliable indicator of mating.
Female mice housed together tend to go into anestrus and do not cycle. If exposed to a male mouse or the pheromones of a male mouse, most of the females will go into estrus in about 72 hours. This synchronization of the estrous cycle is known as the Whitten effect. The exposure of a recently bred mouse to the pheromones of a strange male mouse may prevent implantation (or pseudopregnancy), a phenomenon known as the Bruce effect.
The average gestation period is 20 days. A fertile postpartum estrus occurs 14-24 hours following parturition, and simultaneous lactation and gestation prolongs gestation 3-10 days due to delayed implantation. The average litter size is 10-12 during optimum production, but is highly strain dependent. As a general rule, inbred mice tend to have longer gestation periods and smaller litters than outbred and hybrid mice. The young are called pups and weigh at birth, are hairless, and have closed eyelids and ears. Cannibalism is uncommon, but females should not be disturbed during parturition and for at least 2 days postpartum. Pups are weaned at 3 weeks of age; weaning weight is . If the postpartum estrus is not utilized, the female resumes cycling 2-5 days postweaning.
Newborn male mice are distinguished from newborn females by noting the greater anogenital distance and larger genital papilla in the male. This is best accomplished by lifting the tails of littermates and comparing perineums.
Mice are common experimental animals in biology and psychology primarily because they are mammals, and so share a high degree of homology with humans. 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 (note Animal Rights). 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 (and rats) have the same organs in the same places, just different proportions.
There are hundreds of established inbred, outbred, and transgenic strains. In the United States, mice are not protected by the Animal Welfare Act (AWA) (administered by the United States Department of Agriculture (USDA), APHIS). However, the Public Health Service Act (PHS) administered by the National Institutes of Health (NIH) does cover their treatment.
Some benefits of having mice as pets are
Humans have eaten mice since prehistoric times. They are still eaten as a delicacy throughout eastern Zambia and northern Malawi, as well as in parts of east Asia, including Guangdong Province, China. They are an excellent seasonal source of protein. In most other countries, mice are no longer routinely consumed by humans. Across the U.S. pet owners keep exotic pets such as snakes, lizards, frogs, tarantulas, and birds of prey. Most US pet stores now carry mice for this purpose. Because they breed quickly, grow quickly, are easy to care for, and can be sold in a wide variety of sizes, this makes them suitable for consumption by animals of various sizes. Mice also seem to be a desirable food item for a very large variety of carnivores. For ethical reasons it may be considered questionable (and under German law, forbidden) to feed live mice (or any vertebrate for that matter) to carnivores. An exemption may be made for those carnivores that do not eat anything but live food, a claim particularly made by snake owners on behalf of their pets. It is especially unnecessary to feed "pinkies" to Tarantulas; their venom is about as strong as a bee's sting, and it takes a long time for the venom to overcome the prey's nervous system, suggesting a prolonged agony. Common terms used to refer to different age/size mice are pinkies, fuzzies, hoppers, and adults. Pinkies are newborn mice that have not yet grown fur; fuzzies have some fur but are not very mobile; hoppers have a full coat of hair and are fully mobile but are smaller than adult mice. These terms also refer to the various growth stages of rats (also see Fancy rat).