For More Information on Norway Rats:

University of Nebraska Cooperative Extension

University of California Extension

Origin:  
It is speculated that the Norway Rat may have originated from China, Japan, mainland Asia, India, and other Indo-Malayan countries.

Introduction to U.S.:  
The Norway Rat came to North America aboard ships around 1775.

Characteristics:  
Dark brown to black, 12-18 inches in length including the bald tail, stocky body, small hairy ears, small eyes and a blunt snout, adaptable to a wide range of conditions.  
Nocturnal and cautious, they do not travel far from their nest.  Norway rats can enter a structure through an opening as small as ½ inch. They nest in lower levels of buildings and basements and burrow outdoors in soil, under sidewalks, near streams and rivers and near garbage.  Norway rats have poor agility and sight but their other senses are excellent.  They are good swimmers.  Foods of choice are meat, fish, and cereals. Rats will chew through almost anything to get to food or water.

Reproduction:  
Adults usually live between 6 to 12 months, generally producing 3 - 6 litters, with an average of  7 - 8 young per litter. 

Impacts: 
Norway rats consume and contaminate foodstuffs and animal feed, cause structural damages to buildings and their foundations, road ways, railroad tracks and irrigation canals. Norway rats may also transmit the following diseases to humans or livestock:  murine typhus, leptospirosis, trichinosis, salmonellosis (food poisoning), and ratbite fever. 

Control Methods:  
There is a need for good sanitation in residential areas, including proper storage and handling of food materials and refuse.  Rodent proof construction, rodenticides, electronic devices, predators and trapping are other means of control.