RAT

Kangaroo rat (Dipodomys). any of the more than 500 named forms of the genus Rattus, family Muridae (order Rodentia). Rats are commonly thought of as dark animals with pointed noses and naked feet and tails; they are similar to, but generally larger than, mice. The name rat is also applied indiscriminately to many moderate-sized rodents belonging to several families, such as the bamboo rat (Rhizomyidae), cane rat (Thryonomyidae), kangaroo rat (Heteromyidae; see photograph), and rice rat (Cricetidae). Ordinarily, rat refers to either the black rat (Rattus rattus) or the Norway rat (R. norvegicus). These are aggressive, active, omnivorous, adaptable, and fecund animals that live with man and have accompanied him almost throughout the world. The senses of these rats are highly developed, and their ability to climb, jump, burrow, or gnaw gains them entry to places inaccessible to many other small mammals. They are able to breed at three to four months and can produce up to seven litters a year, each containing 6 to 22 young. Black and Norway rats have destroyed quantities of valuable poultry, game, crops, and stored grain and have been implicated in harbouring or transmitting, directly or indirectly, more than 20 diseases. The black rat, also called roof, Alexandrine, climbing, or gray rat, has a head and body about 20 centimetres (8 inches) long and a tail somewhat longer. It has a pointed nose and ears about one-half the length of the head. Dark gray or brownish above and gray or whitish below, it is an excellent climber and jumper. The Norway rat, also known as barn, brown, sewer, or wharf rat, differs from the black rat in having proportionately smaller ears, a more robust body, and a tail shorter than the combined head and body length of 18 to 25 cm. Its colour is usually brown but may be gray, white, black, or pied. Laboratory rats are domesticated albino strains of the Norway rat. In contrast to the black rat, the Norway rat digs burrows and is an adept swimmer. It is larger and more adaptable than the black rat. When both species live in the same area, they occupy different habitats; in a building, for example, the Norway rat tends to occupy the lower levels, while the black rat lives on the upper floors. The most effective methods of rat control are adequate sanitation and ratproof construction; other methods include trapping, poisoning, and fumigation.