Rat, a small, furry rodent (gnawing animal) found all over the world. Rats range in length from about four inches (10 cm) to more than one foot (30 cm). Large rats weigh up to four pounds (1.8 kg). Most rats have pointed noses, coarse fur, and long, bare tails. Some kinds, however, have hairy tails, and others have no tails at all. Except for a few species, rats are relatively harmless to humans. They are closely related to mice, but are larger, and have a number of minor structural differences.

The kangaroo ratThe kangaroo rat roams the southwestern United States.

Several kinds of rats are native to the Western Hemisphere. Among these are the kangaroo rats of the southwestern United States; the rice rats and cotton rats of the southern United States, Mexico, and South America; the pack rats of Mexico and the United States; and the muskrats that live on the banks of ponds and rivers in nearly all parts of Canada and the United States.

Common Rats

The most common rats are the Norway, or brown, rat ; and the black, or roof, rat. Both are noted for being among mankind's worst enemies. They originated in Asia and spread to all parts of the world except some areas in the Arctic and Antarctic not inhabited by humans.

Description and Habits

The Norway rat averages about eight inches (20 cm) in length exclusive of the tail, which is shorter than he thickset body. The animal is brown on op with grayish underparts. The black rat is bout one inch (2.5 cm) shorter than the Norway rat. It is relatively slender, and the ail is longer than the body. The black rat is irown or black above and gray or white leneath. The white rat is the albino form of he Norway rat. It is used as an experimental nimal in scientific laboratories. It is often aised as a pet.

Common rats usually make their nests in or near the homes of human beingsā€”in barns, warehouses, basements, and attics. Rats are also found in sewers and garbage dumps, and on ships and trains. Rats have several litters a year, with as many as a dozen or more young in each litter. They are born blind and hairless.

Common rats are intelligent animals that an adapt to almost any environment. They at many kinds of food, including grains, vegetables, and meat. If there is no other food, they will eat each other.

Common Rats As Pests

Rats can transmit such diseases as bubonic plague and typhus. During the Middle Ages, bubonic plague, a devastating epidemic disease called the Black Death, killed hundreds of thousands of people. In one epidemic, one-fourth of the population of Europe died. Health authorities control rat-borne diseases through modern medical practices and by constant war gainst rats.

Norway and black rats destroy or contaminate stored grain and other foods, including eggs. They kill poultry, and have even injured and killed human infants. They are aggressive fighters and, when cornered, will attack humans.

Their intelligence and adaptability make these rats hard to get rid of. They soon learn to spring traps without getting caught and they avoid poisoned food that they have seen kill other rats. They can gnaw through wood and plaster, making it necessary to ratproof food-storage buildings with metal and concrete. It is sometimes necessary to fumigate buildings to rid them of rats.

Chemists have developed poisons that kill only rats, and poisons that act so slowly the other rats are not warned. But the chief method of controlling rats is to store all food in ratproof buildings or in closed containers. Garbage should be placed in tightly covered cans.

Common rats belong to the family Muridae. The Norway rat is Rattus norvegicus; the black rat, R. rattus.