tree mouse: see mouse; vole.

sea mouse, marine worm of the genus Aphrodite with a short, broad, segmented body, found in moderately deep water. The upper, or dorsal, surface of a sea mouse bears 15 pairs of raised scales; the space between the scales and the body surface forms a channel for the flow of water carrying oxygen for respiration. The entire dorsal surface, including the scales, is covered by long, feltlike threads called setae, which produce a brilliant iridescence; heavier, bristlelike setae project through them. Sea mice commonly reach 6 to 8 in. (15-20 cm) in length and 2 in. (5 cm) in width. They are classified in the phylum Annelida, class Polychaeta, family Aphroditidae.

pocket mouse, small jumping rodent of W North America and as far south as N South America. More closely related to the squirrel than the true mouse, the pocket mouse gets its name from the fur-lined cheek pouches in which it carries its food. It varies in length from 3 to 12 in. (7.6-30.5 cm) according to the species and has hind legs elongated for jumping. Species of the genus Perognathus are soft furred; species of the genera Liomys and Heteromys have stiff, flattened spines mixed in with the fur. The pocket mouse is a solitary, nocturnal animal, living in grass-lined burrows in desert and semidesert regions; one Heteromys species lives in humid forests. The rodent feeds on seeds and other vegetable matter. It can live for long periods without free water by utilizing the moisture available from food and its own digestive processes and by secreting concentrated urine. Females give birth to several litters a year, each litter containing from one to eight young. Gestation takes from 24 to 33 days. Pocket mice have many natural enemies but in captivity have lived as long as five years. They are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia, family Heteromyidae.

mouse hare: see pika.

mouse deer: see chevrotain.

mouse, name applied to numerous species of small rodents, often having soft gray or brown fur, long hairless tails, and large ears. The chief distinction between these animals and the variety of rodents called rats is in size: mice are usually smaller. Many small rodents are adapted for leaping or hopping and are named accordingly, e.g., the North American kangaroo rat and Asian jumping mouse.

Types of Mice

Most, but not all, of the rodents called mice are members of the rodent subclass Myomorpha, or mouselike rodents. The approximately 1,100 species in this enormous group are classified in several families. The Old World family Muridae includes the now ubiquitous house mouse, as well as a great variety of wild-living Old World species, including the Old World field mouse, the tiny European harvest mouse (Micromys minutus) and the African tree mice. The cosmopolitan family Cricetidae includes the native New World mice, such as the deer mouse, American harvest mouse (Reithrodontomys), the carnivorous grasshopper mouse, the South American field mice, the pack rat, and the rice rat; it also includes the various Old and New World species of vole, hamster, lemming, muskrat, and gerbil. Still other families of the Myomorpha include the dormouse, jumping mouse, and jerboa. The pocket mouse and the kangaroo rats and mice are members of the suborder Sciuromorpha, or squirrellike rodents.

House Mouse

The house mouse, Mus musculus, found throughout the world, is the most familiar of the mice; many of its races live commensally with humans and are serious pests, while others live in the wild. It usually measures about 6 in. (15 cm) long and weighs under 1 oz (28 grams). It has gray to brown fur, large rounded ears, a pointed muzzle, and a naked scaley tail. An omnivorous feeder, it causes great destruction and contamination of food supplies. Its nests are built of available chewable materials, such as clothing and paper. It may carry human diseases, such as typhoid and spotted fever. Females produce litters of four to eight young after a gestation period of three weeks; under favorable conditions they breed throughout the year. The young mature in two months. House mice, particularly albino strains, are extensively used in biological and medical experimentation and are also sometimes kept as pets.

Field Mouse

Field mouse is a name applied to various wild-living mice in different parts of the world. The Old World field mice are species of the genus Apodemus, closely related to the house mouse and found throughout Eurasia and North Africa. The widely distributed long-tailed field mouse, Apodemus sylvaticus, is a nocturnal, burrowing creature that prefers succulent plant food and frequently invades gardens and houses. In North America the name field mouse (or meadow mouse) is applied to voles. South American field mice belong to the genus Akodon, with about sixty species distributed among a wide variety of habitats, including human dwellings. Most of these resemble long-tailed voles. The name tree mouse is likewise applied to various arboreal mice and voles in different parts of the world.

Classification

Mice are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia.

meadow mouse: see vole.

lemming mouse: see vole.

kangaroo mouse: see kangaroo rat.

jumping mouse, rodent slightly larger than the common mouse, found in North America and N Asia, also called the kangaroo mouse. Its long hind legs and tail enable it to leap distances up to 12 ft (3.7 m). Jumping mice have gray to brown fur and are white underneath. They can scurry as well as leap and are good swimmers. Solitary, nocturnal animals, they are found in marshes and on stream banks in coniferous and deciduous forests of both coasts of North America and also in fields and pastures. Two genera, Zapus and Napaeozapus, are North American, ranging from the Arctic Circle S to New Mexico and Tennessee; a related genus, with one species, Eozapus setchuanus, the Szechuan jumping mouse, is native to China. Jumping mice feed on a diet of grass seeds, fruit, and insect larvae. They gain weight in autumn and hibernate in fur-lined burrows during winter. Litters, containing from three to six young, are born in late spring. Jumping mice are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia, family Zapodidae.

hopping mouse: see mouse.

field mouse: see mouse; vole.

or wood mouse

In general, any mouse that normally lives in fields; more strictly, any of about seven species of small, long-tailed mice in the genus Apodemus (family Muridae). Field mice in this genus are found in fields, woodlands, and mountain meadows in the warm and temperate parts of Eurasia. They are grayish or light or reddish brown and are 2–5 in. (6–12 cm) long excluding the tail. They generally live in burrows and build nests of grass and other plants. They eat seeds, roots, and other plant material, occasionally damaging crops or young trees.

Learn more about field mouse with a free trial on Britannica.com.

Any of about 30 species of nocturnal North American rodents constituting the genus Perognathus (family Heteromyidae), having fur-lined, external cheek pouches that open alongside the mouth. Pocket mice are yellowish brown to dark gray and are 2.5–5 in. (6–13 cm) long, excluding a tail of about the same length. They are usually solitary and inhabit dry and desert regions. They carry food (mainly seeds) in their pouches and store it in their burrows. Spiny pocket mice (most in the genera Liomys and Heteromys; family Heteromyidae), found from Mexico through Central America, are gray, brown, or black nocturnal burrowers that inhabit wet, forested regions as well as dry country.

Learn more about pocket mouse with a free trial on Britannica.com.

or mouse deer

Any of several species (family Tragulidae) of small, delicately built ruminants of Asia and Africa. Resembling tiny deer, chevrotains stand about 12 in. (30 cm) at the shoulder and seem to walk on their hooftips. Their fur is reddish brown with spots and pale stripes. Males have small, curved tusks protruding downward from the upper jaw. Shy and solitary, they are active at night. Asiatic chevrotains are found in forests from India to the Philippines. The water chevrotain of western equatorial Africa inhabits thick cover on the banks of rivers and seeks escape in the water when disturbed.

Learn more about chevrotain with a free trial on Britannica.com.

Any of many species (family Muridae) of small, scampering rodents. They are distinguished from rats principally by their smaller size. Mice are basically Asian in origin, but species have been introduced worldwide. Species in other rodent families (e.g., deer mouse, pocket mouse) are called mice without scientific basis. Mice eat grains, roots, fruit, grass, and insects. They can become pests but are mostly beneficial; they are the main prey of most furbearers and of predators that might otherwise take more valuable prey. The white laboratory mouse is a form of house mouse. Seealso field mouse.

Learn more about mouse with a free trial on Britannica.com.

Common mouse species (Mus musculus, family Muridae), the mouse most often encountered in buildings. The house mouse has been distributed by humans from Eurasia to all inhabited areas of the world and usually seeks shelter and food in human dwellings. Brown or gray, it grows up to 8 in. (20 cm) long, including a 4-in. (10-cm) tail. It consumes almost anything edible, even sampling soap, paste, and glue. It matures quickly and is ready to mate two to three months after birth. In warm areas or heated buildings, it breeds throughout the year.

Learn more about house mouse with a free trial on Britannica.com.

or white-footed mouse

Any of about 60 species (genus Peromyscus, family Cricetidae) of small, delicate rodents that are active at night and are found in habitats from Alaska to South America. They often outnumber all other mammals in an area. Deer mice are 3–6.5 in. (8–17 cm) long (excluding the long tail) and have large eyes, soft fur, and relatively large ears. Colours range from white to brown or blackish, with white underparts and feet. They eat plant and animal matter and nest in burrows or trees. Clean, easily cared for, and prolific, they are often used as laboratory animals.

Learn more about deer mouse with a free trial on Britannica.com.