rat (redirected from Wistar 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. rattus, the black, roof, or Alexandrine, rat. Both species originated in Asia, but have spread throughout the world, mostly on board ships. The black rat was common in Europe in the Middle Ages and was responsible for the spreading of plague. It has since been largely displaced in cooler regions by the brown rat, which reached Europe early in the 18th cent. and North America by 1775.

The brown rat is the larger of the two, growing up to 10 in. (25 cm) long excluding the naked, scaley tail and sometimes weighing more than a pound (.5 kg). It is commonly brown with whitish underparts and pink ears, feet, and tail. It is a poor climber, but an excellent burrower and swimmer; it is found in the damp basements and sewers of most temperate zone cities. The laboratory white rat is an albino strain of the brown rat.

The black rat is commonly dark gray. It reaches a maximum length of 8 in. (20 cm) and has a longer tail and larger ears than the brown rat. A good climber, the black rat inhabits attics and upper floors in warm areas; it is the common rat of the Mediterranean region, the SE United States, and Central and South America.

Rats are omnivorous, aggressive, intelligent, adaptable, and extremely fecund. Females produce as many as 8 litters each year with as many as 20 young per litter. The gestation period is three weeks, and the young reach sexual maturity in about two months. Rats may live as long as four years. They are social animals but sometimes fight among themselves.

Rats live mostly in and around human settlements, where they have few natural enemies and an abundant source of food. They invade food supplies and cause widespread destruction; they also spread human diseases such as typhus and tularemia. Despite human efforts to exterminate rats, the house rat population is probably equal to the human population.

Besides the house rats, the genus Rattus contains several hundred wild-living species. In addition, many other members of several different rodent families are called rats, e.g., the bandicoot rat, the wood rat, or pack rat, the rice rat, the muskrat, and the kangaroo rat. House rats are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia, family Muridae.

See also mouse.

Bibliography

See H. Zinsser, Rats, Lice and History (1935); S. A. Barnett, The Rat, a Study in Behavior (1963).

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rat

Norway rat (Rattus norvegicus).

(credit: John H. Gerard)

Any of more than 500 forms of Asian rodent (genus Rattus, family Muridae) that have been introduced worldwide. The black rat (Rattus rattus) and the Norway rat (R. norvegicus) are the aggressive, omnivorous animals commonly associated with the name. They prefer areas of human habitation, where they can easily find food. They have keen senses and can climb, jump, burrow, or gnaw their way into seemingly inaccessible places. They reproduce extremely rapidly (up to 150 offspring a year) and have few natural predators. Rats transmit numerous human diseases and have often destroyed grain supplies. The black rat is about 8 in. (20 cm) long, excluding the slightly longer tail. The Norway rat (also called the brown, barn, sewer, or wharf rat) has proportionately smaller ears and a shorter tail. Laboratory rats are strains of the Norway rat. The name rat is applied, without scientific basis, to other rodents (e.g., kangaroo rat, wood rat).

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(Remote Administration Trojan) A Trojan in a user's machine that is interactively controlled by the attacker. The attacker remotely configures and controls the Trojan in the infected machine just like a user with a Web browser requests data from a server. Back Orifice is an example of a RAT. See Trojan.