Inhabit practically every part of the world.
Associated with farm buildings in rural areas; sewer systems, garbage dumps, refuse piles and grain silos. Easily adapts to various habitats worldwide.
Fur of this rat varies in color but is generally brown or grayish-brown with some black hairs, becoming paler on the underside. The tail is long and largely hairless. The naked ears are prominent and the eyes are relatively small.
These rats make a network of interconnecting tunnels 1.5 feet deep, 2-3 inches across and 6 feet long. These tunnels contain one or more chambers for nesting or feeding, one or more main entrances and several escape exits. It digs by cutting roots with its incisors, freeing dirt and pushing it under its body with its forefeet and out behind with its hind feet; then turns around and pushes the dirt out with its head and forefeet. Vocalizes with squeaks, whistles and chirps. It is a good climber and a good swimmer.
This rat is one of the most prolific of all mammals. Females become sexually mature at just 8-12 weeks. Gestation is between 21 and 23 days, and females are able to conceive while suckling a previous litter, often mating within 18 hours of giving birth. They can breed throughout the year if the weather is mild and there is plenty of food. Thirteen litters are possible each year, each one consisting of 7 - 9 young.
This rat is considered to be one of the most serious mammalian pests ever known. It is a supreme generalist. Their opportunistic lifestyle, coupled with agility and prolific breeding potential help it to do well in practically every part of the world.
: Throughout the world, introduced animals are disrupting natural food webs and causing native animals to become endangered or extinct. The Norway rat is an efficient predator of the eggs of ground-nesting birds, and has contributed to the decline of the Nene goose, the state bird of Hawaii.