Adult Norway rats are large and robust, reaching up to 16 inches from nose to tip of tail.
Norway rats are stocky and their tail length is less than their body length. Their tails are scaly and almost hairless. They range in color from white to brown to mottled, or blackish gray, reddish brown, and other variations. They have a blunt nose, small eyes, and small ears.
The Norway rat is primarily a ground dweller and prefers to live in burrows. It swims very well and often lives in sewers and other underground water systems. It can be found anywhere humans live. In suburban areas they live in and around residences, in cellars, warehouses, stores, slaughterhouses and docks. Although they can climb, Norway rats tend to inhabit the lower floors of multi-story buildings. This rat is primarily a nocturnal animal, and will usually only travel 20 to 30 feet from its home to find food and water. A normal life expectancy for this rat is one year or less.
Norway Rats are omnivores and opportunistic feeders, feeding on any natural or human foods available.
Norway rat litters average eight to nine pups, and a female may have several litters in her one year of life.
The Norway rat is neophobic; avoiding new objects placed in its environment for some time. Damage from gnawing can be extensive, as they chew on plastic or metal pipes, wires, wood, furnishings and walls, and they often bite humans. While not the primary reservoir of bubonic plague, Norway rats have the potential to spread this disease and several others.