The Norway rat probably first came from central Asia. It made its way on trading ships into Europe during the middle ages during which it played a key part in spreading the Bubonic Plague through the fleas it carried. The Norway rat prefers to live near people. There never were more of these rats in Norway than in other parts of Europe or Asia, but the name stuck. Some science books say that it was first collected for scientific studies in Norway.
 

The Norway rat is also called the common rat, sewer rat, brown rat, and water rat. In the wild it is brownish-gray on its back, and greyish on its belly, with a long scaly tail 5 to 10 inches long. It has small bulbous eyes like most rodents and large ears. They are usually 1 to 1.25 feet long and weigh anywhere between 1/4 and 3/4 lb. It is not native to North America but came over from Europe on ships along with settlers. It lives in all parts of the Northeastern United States and Canada, mostly where people live. It usually lives in buildings and sewers during the winter but builds its nests in fields where food and crops grow during the summer.
 

The Norway rat makes a network of interconnecting tunnels 2 to 4 inches across and up to 1.5 feet deep and 5 feet long. It usually lives alone with one or more rooms for nesting or eating as they are territorial, however, they can also be found living with other rats in a maze of tunnels, nests and rooms. It digs by cutting roots or other underground things that are in the way with its sharp incisors (front teeth), and then scrapes away loose dirt. It pushes the dirt under its body with its hind feet, then turns around and pushes the dirt down the tunnel with its head and forefeet. Rats can go through the hollow walls of houses, gnawing out wood and sheetrock.
 

The Norway rat adapts very well to all places where people live. It is omnivorous and eats anything people tend to eat and then throw away. In addition to "people food" it also eats insects, green plants, fruits, birds, rabbits, small snakes, mice, young pigs, soap, garbage, seeds, and grain. It kills chickens and eats their raw eggs as well. The Norway rat gnaws paper, wood, plastic, and cloth, however, it prefers grains, meats, and cheeses that contain much protein.
 

The Norway rat has enemies which include the raccoon and cat. Of course, man is responsible for curbing the populations of rats in cities and towns.
 

If not controlled by man or natural enemies, the Norway rat can easily have a population explosion. A female can mate with a male just hours after giving birth, and mating goes on between males and females all year round. The 7 to 11 young per litter are born hairless and blind but can open their eyes at two weeks of age. They are well enough developed to leave the nest at three to four weeks of age; Females can breed at three months of age. In a litter, a rat can have 2 to 22 young, but 7 to 11 is much more usual. Few Norway rats live out their full three years. At two years of age, females stop breeding and males are not as interested in mating. A female can have up to 12 litters a year if conditions are very good, but usually has five.
 

The Norway rat does have a use in science. Scientists breed the white rat for use in medical laboratories, and white rats also makes good pets! They are generally free of disease, very tame, and clean. The white (or albino) rat cleans itself by grooming with its tongue and forefoot, and in this way, it is very similar to a cat. In addition to making a nice pet, they are also used to test all kinds of food and medicine before they are given to people.