Adults are about 7-18 inches in length, the head and body uses up 7-9.5 inches of that length. The any where from a half pound to a pound. Their hair is course, 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 theses animals are social and tend to have more than one entrance hole. The opening will be of 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.
Norway rats prefer to eat meat and cereal, though they will eat anything. If the food material eaten proves to be disagreeable, they are quick to develop food/bait shyness. Once these rats find a food that they like they will eat their fill in one sitting and return for more time after time. They almost always require a nonfood or separate source of water. They will travel about 150 feet from their harborage for food and water. They will gnaw through almost anything to obtain food and water, even plastic or lead pipes.
Once Norway rats establish themselves, they tend to follow the same route between their homes and their food and water sources. As often as possible, they follow vertical surfaces which their long whiskers can contact. Runways along vertical surfaces will usually include dark rub marks on the vertical surfaces where their oily fur makes contact. Their runway will be free of debris, and outdoors, the grass will be worn away to the bare soil.
Norway rats reach sexual maturity in 2-5 months. pregnancy lasts an average of 21-25 days. The young are blind and naked (have no hair) at birth. The hair will start to appear in 7 days and the eyes open in approximately two weeks. They are weaned at after three weeks. The range numbered per year consist of is 3-6 litters, each containing a range of 6-22 young.
They have rather pour vision and are color blind, but the other senses they have are very keen. They are good runners, climbers, jumpers and swimmers. Norway rats require 3/4-1 oz. of food and 1/2-1 oz. of water each day, with the water coming from a nonfood source.
Rattus norvegicus Berkenhout
“Brown, House, Wharf or Sewer Rat”