rodent, member of the mammalian order Rodentia, characterized by front teeth adapted for gnawing and cheek teeth adapted for chewing. The Rodentia is by far the largest mammalian order; nearly half of all mammal species are rodents. They are worldwide in distribution and are found in almost every terrestrial and freshwater habitat, from the shores of the Arctic Ocean to the hottest deserts. They are variously adapted for running, jumping, climbing, burrowing, swimming, and gliding. Many of them have dexterous forepaws, which they use as hands while sitting on their haunches in a position characteristic of many rodents. The great majority are under a few inches in length; the largest, the
capybara capybara , mammal of Central and much of South America. It is the largest living member of the order Rodentia (the rodents) reaching a length of 4 ft (120 cm) and a weight of 75 to 100 lb (34–45 kg).
..... Click the link for more information. , is about 4 ft (120 cm) long and 20 in. (50 cm) high at the shoulder.
Characteristics of Rodents
Rodents have enlarged, chisel-shaped upper and lower front incisors that grow throughout their lives. These have hard enamel on the front surface and soft dentine on the back surface, so that unequal wear keeps the chisel edge sharp. There is a gap between the front teeth and the cheek teeth. When the lower jaw is in a forward position, for gnawing, the upper and lower incisors are in contact but the upper and lower cheek teeth are not; thus, wear on the cheek teeth is avoided. The cheeks are drawn in behind the incisors when the animal is gnawing, so that bits of hard material cannot be swallowed. When the lower jaw is pulled back into the chewing position, only the cheek teeth make contact.
Types of Rodents
The approximately 4,000 rodent species are divided on the basis of their anatomy into three well-defined groups, or suborders, and more than 30 families. The Sciuromorpha, or squirrellike rodents, include the various species of squirrel squirrel, name for small or medium-sized rodents of the family Sciuridae, found throughout the world except in Australia, Madagascar, and the polar regions; it is applied especially to the tree-living species.
..... Click the link for more information. , chipmunk chipmunk, rodent of the family Sciuridae (squirrel family). The chipmunk of the E United States and SE Canada is of the genus Tamias. The body of the common Eastern chipmunk, Tamias striatus, is about 5 to 6 in.
..... Click the link for more information. , marmot marmot, ground-living rodent of the genus Marmota, of the squirrel family, closely related to the ground squirrel, prairie dog, and chipmunk. Marmots are found in Eurasia and North America; the best-known North American marmot is the woodchuck, M.
..... Click the link for more information. , woodchuck woodchuck or groundhog, common name of a North American species of marmot, Marmota monax. This large rodent is found in open woods and ravines throughout most of Canada and the NE United States.
..... Click the link for more information. (or ground hog), prairie dog prairie dog, short-tailed, ground-living rodent, genus Cynomys, of the squirrel family, closely related to the ground squirrels, chipmunks, and marmots. There are several species, found in the W United States and N Mexico.
..... Click the link for more information. , gopher gopher or pocket gopher, name for the burrowing rodents of the family Geomyidae, found in North America and Central America. The gopher is gray, buff, or dark brown. Its combined head and body length is 5 to 12 in.
..... Click the link for more information. (or pocket gopher), pocket mouse 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.
..... Click the link for more information. , kangaroo rat kangaroo rat, small, jumping desert rodent, genus Dipodomys, related to the pocket mouse. There are about 20 kangaroo rat species, found throughout the arid regions of Mexico and the S and W United States.
..... Click the link for more information. , and beaver beaver, either of two large aquatic rodents, Castor fiber and Castor canadensis, known for their engineering feats. They were once widespread in N and central Eurasia except E Siberia, and in North America from the arctic tree line to the S United
..... Click the link for more information. . The Myomorpha, or mouselike rodents, include a great variety of mouse 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.
..... Click the link for more information. and rat rat, name applied to various stout-bodied rodents, usually having a pointed muzzle, long slender tail, and dexterous forepaws. It refers particularly to the two species of house rat, Rattus norvegicus, the brown, or Norway, rat and R.
..... Click the link for more information. species, as well as species of hamster hamster, Old World rodent, related to the voles, lemmings, and New World mice. There are many hamster species, classified in several genera. All are solitary, burrowing, nocturnal animals, with chunky bodies, short tails, soft, thick fur, and large external cheek
..... Click the link for more information. , lemming lemming, name for several species of mouselike rodents related to the voles. All live in arctic or northern regions, inhabiting tundra or open meadows. They frequently nest in underground burrows, particularly in winter, although they do not hibernate.
..... Click the link for more information. , vole vole, name for a large number of mouselike rodents, related to the lemmings. Most range in length from 3 1-2 to 7 in. (9–18 cm) and have rounded bodies with gray or brown coats, blunt muzzles, small ears concealed in the long fur, and short tails.
..... Click the link for more information. , muskrat muskrat, North American aquatic rodent. The common muskrats, species of the genus Ondatra, are sometimes called by their Native American name, musquash.
..... Click the link for more information. , gerbil gerbil , small desert rodent found throughout the hot arid regions of Africa and Asia. Also known as sand rats, gerbils have large eyes and powerful, elongated hind limbs upon which they can spring. Gerbils are 3 to 5 in. (7.6–12.
..... Click the link for more information. , dormouse dormouse, name for Old World nocturnal rodents of the family Gliridae. There are many dormouse species, classified in several genera. Many resemble small squirrels.
..... Click the link for more information. , and jerboa jerboa , name for the small, jumping rodents of the family Dipodidae, found in arid parts of Asia, N Africa, and SE Europe. Jerboas have extremely long hind feet and short forelegs; they always walk upright or hop like kangaroos.
..... Click the link for more information. . This is the largest rodent group. The Hystricomorpha, or porcupinelike rodents, include the porcupine porcupine, member of either of two rodent families, characterized by having some of its hairs modified as bristles, spines, or quills. The quills are loosely attached to the porcupines' skin and pull out easily, remaining imbedded in any predator that comes in
..... Click the link for more information. , capybara, nutria nutria or coypu , aquatic rodent, Myocastor coypus, of South America, introduced in the S United States for its fur, which is similar to that of beaver but not as thick or durable. The nutria resembles a small beaver with a ratlike tail.
..... Click the link for more information. (or coypu), agouti agouti , name applied to rabbit-sized rodents of the genus Dasyprocta, found in Central and South America and in the West Indies. They have slender limbs with five front and three hind toes, rudimentary tails, and coarse rough hair that varies from reddish to
..... Click the link for more information. , cavy cavy , name for 14 species of South American rodents of the family Caviidae, including the domestic guinea pig. The wild cavies are usually small, rounded, and tailless, with fur of a uniform shade of brown.
..... Click the link for more information. (including the domestic guinea pig guinea pig , domesticated form of the cavy, Cavia porcellus, a South American rodent. It is unrelated to the pig; the name may refer to its shrill squeal. Guinea pigs were raised by the Incas and have long been used as food in South America.
..... Click the link for more information. ), mara, and chinchilla chinchilla , small burrowing rodent of South America. It lives in colonies at high altitudes (up to 15,000 ft/4,270 m) in the Andes of Bolivia, Chile, and Peru. One of the costliest of all furs, its soft gray pelt has been valued since the days of the Inca.
..... Click the link for more information. , as well as many species whose common names include the term rat (e.g., the South American bush rat).
Rabbits and hares were once classified as rodents because of their large, chisel-shaped incisors. However, they are quite distinct anatomically and have a long, separate evolutionary history; they are now classified in an order of their own, the Lagomorpha. Using DNA analyses as evidence, some scientists believe that the some other groups of rodents have descended from different ancestors and should thus be placed in orders of their own.
See also mountain beaver mountain beaver, stout, short-limbed North American rodent, Aplodontia rufa, not closely related to the true beaver. Also called sewellel beaver after the Chinook word for a robe made from its pelts, it is among the most primitive of the rodents and the only
..... Click the link for more information. , ground squirrel ground squirrel, name applied to certain terrestrial rodents of the squirrel family. In North America the name refers to members of the genus Citellus and sometimes to the closely related genera Tamias (chipmunk), Cynomys (prairie dog), and
..... Click the link for more information. , flying squirrel flying squirrel, name for certain nocturnal tree squirrels adapted for gliding; they do not actually fly. Most are found in Asia, but one species of the genus Pteromys extends into SE Europe and the two species of Glaucomys are found in North America.
..... Click the link for more information. , pack rat pack rat, rodent of the genus Neotoma, of North and Central America, noted for its habit of collecting bright, shiny objects and leaving other objects, such as nuts or pebbles, in their place; also called trade rat or wood rat.
..... Click the link for more information. , bandicoot rat bandicoot rat, giant rat of southern Asia, unrelated to true bandicoots. It is an agricultural pest in the grain crops and gardens of India and Sri Lanka and is known for the piglike grunts it emits when attacked.
..... Click the link for more information. , and jumping mouse 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.
..... Click the link for more information. .
Bibliography
See Sir J. R. Ellerman, The Families and Genera of Living Rodents (2 vol., 1940, repr. 1965); B. S. Vindgradov and A. I. Argiropulo, Key to Rodents (tr. 1968).
rodent
Any member of the order Rodentia, which contains 50% of all living mammal species. Rodents are gnawing, mostly herbivorous, placental mammals. They have one pair of upper and one pair of lower, continuously growing, incisors. When the lower jaw is pulled back, the cheek teeth connect for grinding; when it is pulled forward and down, the incisors meet at the tips for gnawing. Rodent families include squirrels (Sciuridae); Old World mice (see mouse) and rats (Muridae); deer mice (see deer mouse), gerbils, hamsters, lemmings, muskrats, wood rats, and voles (Cricetidae); beaver (Castoridae); gophers (Geomyidae); guinea pigs (Caviidae); pocket mice (see pocket mouse) and kangaroo rats and mice (Heteromyidae); New and Old World porcupines (Erethizontidae and Hystricidae); and hutia (Capromyidae).
rodenta. any of the relatively small placental mammals that constitute the order Rodentia, having constantly growing incisor teeth specialized for gnawing. The group includes porcupines, rats, mice, squirrels, marmots, etc.
b. (as modifier): rodent characteristics
rodent [
′rōd·ənt]
(vertebrate zoology)
The common name for members of the order Rodentia.