Rats

Adapted from Funk & Wagnall's Encyclopedia, found in Infopedia. Funk & Wagnall's Encyclopedia © 1993, 1994 Funk & Wagnall's, Inc., Licensed to Future Vision Media. Infopedia © 1994 Future Vision Media, Inc.

Rat, common name for any large rodent of the family Muridae, smaller members of which are known as mice (see MOUSE). Rats are dull-colored, long-tailed creatures with large ears, pointed snouts, and coarse fur. Rats have extremely powerful teeth, with which they often gnaw through wooden planks to get at stores of food, and they have even been known to bite holes in lead pipes. They are usually nocturnal and live in human habitations, in forests, in deserts, and on seagoing ships. They are extremely prolific, breeding three to five times a year and usually producing 8 to 14 young in a litter. Most species are herbivorous, but some are omnivorous.Brown, Black, and White Rats. Two species of rats are found almost throughout the world. The brown rat, Rattus norvegicus, which is also known as the Norway rat, house rat, gray rat, barn rat, and wharf rat, is the larger of the two. It attains a length of about 40 cm (about 16 in), including the tail, which is about 19 cm (about 7.5 in) long. It is grayish-brown above and sooty white below. This common species is a pest that does much damage to foodstuffs in storehouses, carries fleas that transmit such diseases as plague and typhus fever, and attacks domestic animals, poultry, and occasionally humans. The brown rat was carried on ships from Europe to the U.S. in the late 1700s, and it has gradually displaced the black rat, R. rattus,a smaller, less aggressive species introduced into North America about the 1500s. The black rat, almost completely black in color, is now prevalent in tropical and subtropical America and in the southern U. S. Unlike most other rats, the black rat produces only five or six young in a litter. Like the brown rat, the black rat spreads disease and destroys property. Albino strains of both the black and brown rat are bred for use in biological study; these white rats have been extensively used for nutritional studies, and their use has helped scientists discover many essential dietary components and better understand the growth process.

Rats are controlled by the use of traps or poison. Most rat poisons are dangerous, however, and should be used only under professional supervision. Bush and Wood Rats. Unlike the dangerous rats of Rattus, the bush, or wood, rats, constituting the genus Neotoma of the family Cricetidae, are clean, edible animals that live far from human habitations. The bush rats, which almost equal the brown rat in size, are native to America and are found in wooded and desert areas throughout the U.S. They build characteristic dome-shaped nests, about a meter (about 4 ft) high, the exteriors of which are studded with needle-sharp thorns or bits of cactus for protection against natural enemies. Bush rats feed chiefly on green vegetation. The eastern wood rat, pack rat, trade rat, or bush rat, N. floridana, found along the South Atlantic and Gulf coasts, is slate-gray above and white below. The bushy-tailed wood rat, N. cinerea, differs from most other rats in that it has a hairy tail. This rodent, which is found west of the Rocky Mountains, is buff and black above and white below. The desert brush rat, N. lepida, is a short-tailed bush rat found in the deserts of the western U.S. The Pennsylvania wood rat, N. pennsylvanica, inhabits the eastern U.S. south of New York.

Another common rat of the southeastern U.S. is the cotton, or marsh, rat, Sigmodon hispidis, which is especially abundant around the edges of cotton fields. This aggressive, voracious rodent is about 25 cm (10 in) long, including the tail, which measures about 10 cm (4 in). The cotton rat is yellowish-gray, grizzled with black above and sooty white below. The animal is fond of cotton seeds and also feeds on green vegetation, and occasionally, on the flesh of poultry. It produces 8 to 11 young in a litter.Related Rodents. Several other rodents are popularly known as rats; among these are the bandicoot rat, the kangaroo rat, the ground rat, and the pocket rat. The hutia is frequently called the cane rat, and the gopher is also known as the pouched rat. Certain South and Central American octodont (eight-toothed) rodents are known as spiny rats or hedgehog rats; they constitute the genera Echimys and Proechimys, and are so called because their fur has long, sharp spines.