Norway Rat

Description: The Norway rat is the largest commensal (i.e., living in close association with humans) rodents. The head and body are seven to ten inches long and the tail is an additional six to eight inches. It has a stocky body and weighs seven to 18 ounces. The fur is coarse, shaggy and brown with some black hairs. The muzzle is blunt, eyes and ears are small, and the tail which is bi-colored is shorter than the head and body combined. Norway rat droppings are up to 3/4 inch long with blunt ends.

Biology: Adults are sexually mature in two to five months. Females produce three to six litters per year, each averaging to seven to eight young. Adults live from six to twelve months. They have poor sight but keen senses of smell, taste, hearing and touch.

Habits: Rats are nocturnal. They are shy about new objects and very cautious when things change in their environment and along their established runs. Outdoors, Norway rats prefer to nest in burrows in the soil, e.g., under sidewalks and concrete pads, stream/river banks, railroad track beds, next to buildings, on low ground cover.

Control: The keys to a successful program of rodent control are identification, sanitation, elimination of harborage and rodent-proofing. The inspection should identify signs of infestation, e.g., gnaw marks, droppings, tracks, burrows, rub marks. Sanitation consists of removing food, water and materials which provide harborage.