Mouse

Mouse Temporal range: Late Miocene–Recent
House mouse (Mus musculus).
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Muridae
Subfamily:	Murinae
Genus:	Mus Linnaeus, 1758
Species
30 known species

A mouse (plural: mice) is a small rodent characteristically having a pointed snout, small rounded ears, a body-length scaly tail and a high breeding rate. The best known mouse species is the common house mouse (Mus musculus). It is also a popular pet. In some places, certain kinds of field mice are locally common. They are known to invade homes for food and shelter.

Domestic mice sold as pets often differ substantially in size from the common house mouse. This is attributable both to breeding and to different conditions in the wild. The most well known strain, the white lab mouse, has more uniform traits that are appropriate to its use in research.

The American white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus), as well as other common species of mouse-like rodents around the world, also sometimes live in houses. These, however, are in other genera.

Cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of arthropods have been known to prey heavily upon mice. Nevertheless, because of its remarkable adaptability to almost any environment, the mouse is one of the most successful mammalian genera living on Earth today.

Mice can at times be vermin, damaging and eating crops,^[1] causing structural damage and spreading diseases through their parasites and feces.^[2] In North America, breathing dust that has come in contact with mouse excrement has been linked to hantavirus, which may lead to hantavirus pulmonary syndrome (HPS).

Primarily nocturnal^[3][4] animals, mice compensate for their poor eyesight with a keen sense of hearing, and rely especially on their sense of smell to locate food and avoid predators.^[5]

Mice build intricate burrows in the wild. These burrows typically have long entrances and are equipped with escape tunnels or routes. In at least one species, the architectural design of a burrow is a genetic trait.^[6]

Reproduction

one-day-old pups

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.^[7]

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.^[7]

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 owing 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 0.5–1.5 g (0.018–0.053 oz) 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 10–12 g (0.35–0.42 oz). If the postpartum estrus is not utilized, the female resumes cycling 2–5 days post-weaning.^[7]

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.^[7]

Laboratory mice

Knockout mice

Mice are common experimental animals in laboratory research of biology and psychology fields primarily because they are mammals, and also because they 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. The mouse has approximately 2.7 billion base pairs and 20 chromosomes.^[8] They can also be manipulated in ways that are illegal with humans, although animal rights activists often object. A knockout mouse is a genetically engineered mouse that has had one or more of its genes made inoperable through a gene knockout.

Reasons for common selection of mice are small size, inexpensive, widely varied diet, easily maintained, and can reproduce quickly. Several generations of mice can be observed in a relatively short 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, with the difference of size.

Subgenera

Field mouse of the subgenus Mus.

All members of the Mus genus are referred to as mice. However, the term mouse can also be applied to species outside of this genus. Mouse often refers to any small muroid rodent, while rat refers to larger muroid rodents. Therefore, these terms are not taxonomically specific. For simplicity, only the rodent subgenera belonging to the Mus genus are listed here.

Genus Mus - Typical mice

• Subgenus Coelomys (East Asia)
• Subgenus Mus (Eurasia to North Africa, except for the house mouse which is worldwide.)
• Subgenus Nannomys (Sub-Saharan Africa)
• Subgenus Pyromys (East Asia)
• Subgenus and species Mus lepidoides

As pets

Pet mice

Many people buy mice as companion pets. They can be playful, loving and can grow used to being handled. Like pet rats, pet mice should not be left unsupervised outside as they have many natural predators, including (but not limited to) birds, snakes, lizards, cats, and dogs. Male mice tend to have a stronger odor than the females. However, mice are careful groomers and as pets they never need bathing. Well looked-after mice can make ideal pets. Some common mouse care products are:

• Cage – Usually a hamster or gerbil cage, but a variety of special mouse cages are now available. Most should have a secure door.^[9]
• Food – Special pelleted and seed-based food is available. Mice can generally eat most rodent food (for rats, mice, hamsters, gerbils, etc.)
• Bedding – Usually made of hardwood pulp, such as aspen, sometimes from shredded, uninked paper or recycled virgin wood pulp. Using corn husk bedding is avoided because it promotes Aspergillus fungus, and can grow mold once it gets wet, which is rough on their feet.

Diet

In nature, mice are largely herbivores, consuming any kind of fruit or grain from plants.^[10] However, mice adapt well to urban areas and are known for eating almost all types of food scraps. In captivity, mice are commonly fed commercial pelleted mouse diet. These diets are nutritionally complete, but they still need a large variety of vegetables. Food intake is approximately 15 g (0.53 oz) per 100 g (3.5 oz) of body weight per day; water intake is approximately 15 ml (0.53 imp fl oz; 0.51 US fl oz) per 100 g of body weight per day.^[7]

As food

"Pinkie" mice for sale as reptile food

Mice are a staple in the diet of many small carnivores. Humans have eaten mice since prehistoric times and still eat them as a delicacy throughout eastern Zambia and northern Malawi,^[11] where they are a seasonal source of protein. Mice are no longer routinely consumed by humans elsewhere.

Prescribed cures in Ancient Egypt included mice as medicine.^[12] In Ancient Egypt, when infants were ill, mice were eaten as treatment by their mothers.^[13][14] It was believed that mouse eating by the mother would help heal the baby who was ill.^{[15][16][17][18][19]}

In various countries mice are used as food^[20] for pets such as snakes, lizards, frogs, tarantulas and birds of prey, and many pet stores carry mice for this purpose.

Common terms used to refer to different ages/sizes of mice when sold for pet food are "pinkies", "fuzzies", "crawlers", "hoppers", and "adults".^[21] 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. Mice without fur are easier for the animal to consume; however, mice with fur may be more convincing as animal feed. These terms are also used to refer to the various growth stages of rats (see Fancy rat).

See also

• Genetically modified mouse
• List of fictional mice and rats
• Mousetrap
• Musophobia (fear of mice)
• Mouse brain development timeline
• Vacanti mouse

References

External links

• Fancy Mice: extensive information about breeding mice and keeping them as pets
• High-resolution images of cross sections of mice brains
• History of the mouse (with focus on their use in genetics studies)
• Mouse tracks: How to identify mouse tracks