The Norway rat is the largest of the commensal rodents and the most common commensal rat in the temperate regions of the world. It not only damages/destroys materials by gnawing eats and contaminates stored food but it is also of human health importance as a vector or carrier of diseases. It is thought to be of central Asian origin but is now of worldwide distribution and found throughout the United States.
Adult with combined head and body length 7"-9.5" (18-25 cm) tail length 6"-8" (15-21 cm) usually weight about 7-18 oz (200-500 g) but up to 20.5 oz (620 g). Fur coarse shaggy brown with scattered black hairs with underside grey to yellowish white.
Rats are primarily nocturnal in habit and they are cautious. Although they constantly explore their surroundings they shy away from new objects and changes. Outdoors Norway rats prefer to nest in burrows in the soil along railroad embankments stream/river banks piles of rubbish under concrete slabs etc. The burrow will have at least 1 entrance hole and at least 1 bolt-hole or emergency exit which is often hidden under grass debris etc.