House mice are from 65 to 95 mm long from the tip of their nose to the end of their body, their tails are 60 to 105 mm long. Their fur ranges in color from light brown to black, and they generally have white or buffy bellys. They have long tails that have very little fur and have circular rows of scales. House mice tend to have longer tails and darker fur when living closely with humans. They range from 12 to 30 g in weight. Many domestic forms of mice have been developed that vary in color from white to black and with spots.
House mice may originally be from Europe and Asia, from the Mediterranean region to China, but they are now distributed throughout the world by humans and live as a human commensal.
House mice generally live close to humans, in places like houses and barns. Some individuals spend the summer in fields and move into barns and houses with the onset of cool autumn weather. Because house mice take advantage of human shelters and food, they have been able to live in areas like deserts where, without humans, they would not be able to live.
House mice have a polygynous mating system, where each male mates with multiple females. Males sing when they smell females who are ready to mate, which might attract females.
House mice are able to reproduce throughout the year, often having 5-10 litters each year when conditions are favorable. Pregnancy lasts for 19 to 21 days and 5 to 6 young are born per litter, though there can be as many as 12. Young weigh about 1 gram at birth and are naked, blind, and helpless. At 10 days old they have fur and at 14 days old they open their eyes. The young are nursed for 21 days and reach adulthood at 5 to 7 weeks old.
Young mice are cared for in their mother's nest until they reach 21 days old. Soon after this most young mice leave their mother's territory, though young females are more likely to stay nearby.
If a house mouse is a pet, the average life span is about 2 years, but mutant and calorie-restricted captive individuals have lived for as long as 5 years. Wild-derived captive Mus musculus individuals have lived up to 4 years in captivity. In the wild, most mice do not live beyond 12-18 months.
In the wild, house mice generally live in cracks in rocks or in walls or make underground tunnels. Their homes usually have several "rooms" for nesting and storage, and three or four exits. When living with humans, house mice nest in roofs, in woodpiles, storage areas, or any hidden spot near a source of food. They make their nests from rags, paper, or other soft substances. House mice are generally most active at night, although some are active during the day. House mice are quick runners (up to 8 miles per hour), good climbers, jumpers, and also swim well. Despite this, they rarely travel far from their homes. House mice are generally considered both territorial and colonial when living near humans. Within a group that lives together, there is usually one male with several females and their babies. Among the females, there is a ranking system with one being at the top and the others below her. Family members tend to be kind to each other, but will defend their home against outsiders.
House mice have excellent vision and hearing, a keen sense of smell, and use their whiskers to feel air movements and surface textures. House mice often squeak to each other in the nest. They use pheromones and other smells to communicate with each other about social dominance, family composition, and reproductive readiness. It was recently discovered that male mice produce complex, ultrasonic songs in response to female sex pheromones. (Holy and Guo, 2005)
In the wild, house mice eat many kinds of plant matter, including seeds, roots, leaves, and stems. They will also eat insects (beetles, caterpillars, and cockroaches) and meat if it is available. If house mice live near humans, they will eat any human food that is available as well as glue, soap, and other household materials. Many mice will gather and then store their food for later use.
House mice are eaten by a wide variety of small predators throughout the world, including cats, foxes, weasels, ferrets, mongooses, large lizards, snakes, hawks, falcons, and owls. House mice try to avoid predation by keeping out of the open and by being fast. They are also capable of reproducing very rapidly, which means that populations can recover quickly from predation.
Where house mice are abundant they can consume huge quantities of grains, making these foods unavailable to other (perhaps native) animals. House mice are also important prey items for many small predators.
House mice contribute to the spread of several human and animal diseases, including bubonic plague. They also carry a virus that may contribute to breast cancer in humans. Where abundant, house mice consume large quantities of crops and contaminate foods with their droppings. They can destroy woodwork, furniture, upholstery, and clothing.
House mice have been widely used as research animals in medicine and genetics, and they have contributed to advances in these areas. They are also popular pets and may sometimes act to control insect pests.
There are no problems with the numbers of house mice in the world. In some areas, there can be as many as 10 mice per square meter. Overall, populations are doing extremely well, this is helped by human construction of houses, barns, and other structures.
Waltzing, shaking, and singing mice are other names for certain types of house mice. Some are known as singing mice because of the twitterings they emit while in the nest. Some forms, known as shaking or waltzing mice, move erratically, which is how they get their name.
Allison Poor (editor), University of Michigan-Ann Arbor.
Liz Ballenger (author), University of Michigan-Ann Arbor.
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