Adults are about 7-18 inches in length, the head and body uses up 7-9.5 inches of that length. Anywhere from a half-pound to a pound. Their hair is coarse, shaggy, brown with scattered black hairs. The underside it grey to yellowish-white. The muzzle is blunt, eyes are small, and the ears are small and densely covered with short hairs. The tail is bicolored and scaly. Norway rats are nocturnal and are cautious. Although they constantly explore their surroundings, they shy away from new objects and changes.
They prefer to nest in burrows in the soil along railroad embankments, stream/river banks, piles of rubbish, under concrete slabs, etc. Their burrows will have a least one entrance and one escape hole, but these animals are social and tend to have more than one entrance hole. The opening will be greater than 1/2 inches. Indoors this rat will nest in basements and the lower portions of buildings in piles of debris or merchandise as long as it is not disturbed. On occasion, you can find this rat in the attics, roofs and other higher places.