Smithsonian National Zoological Park l Friends of the National Zoo



Norway Rat

(Rattus norvegicus)

Distribution and Habitat

The Norway rat, or brown rat, is found almost everywhere in the world, except for the Artic and Antarctic. The brown rat thrives wherever there are people, whether that is in a farm or in a city. Their flexible and highly adaptable nature makes them a perfect animal to exhibit in Think Tank.

Physical Characteristics

The Norway rat is a heavy-bodied animal with a scaly tail and coarse hair. Norway rats have incredibly sensitive hearing including the ability to hear ultrasonic frequencies, like those sounds a distressed rat pup makes. Though rats have fairly good vision and night vision, they rely more heavily on their whiskers, which allow them to determine what is in front of them. Because of their incredible sense of smell, a species of rat, called the giant pouched rat, has been trained to be able to pick out tuberculosis in laboratory test samples as well as to detect land mines underground, two very useful behaviors to ensure human safety and health. Selective breeding of albino (Norway or Brown ) rats has produced the ideal rat for the laboratory and pet trade.


The Norway rat is a true omnivore, which has made it highly successful in living among humans and their garbage. There is evidence of social learning in rats. In small populations of rats living near water, rats have learned through watching their peers, how to fish and to dive for mollusks. Another population of rats has even learned to hunt small ducks. Since rats eat just about anything, they tend to sample a small bit of food first, and if it makes them sick, they learn to avoid that food in the future.

Life Span

Most rats live only up to three years of age. There is almost a 95 percentmortality rate in rats under a year old due to predation by other animals.


Female rats can breed all year round, and produce up to five litters of pups a year. The typical gestation period of a rat is only 21 days, and they can have up to 14 pups in one litter!

Social Structure and Activity

Norway rats in the wild live in colonies consisting of small groups of females that raise young together. Once the pups are weaned, male pups leave their natal colony to find territory of their own. The social structure of male rats depends on the population density of rats in that area. They can live alone or in large social groups. Domesticated rats do very well in small groups of same sex animals. Since rats are social animals, they will maintain simple hierarchies within their group.


As you may have guessed, the Norway rat is not considered an endangered or threatened species. Our hope at the National Zoo, is to provide a better awareness of this often hated animal, and allow the public to see first hand how truly adaptable and intelligent they really are.