The Norway Rat

The Norway Rat is also known as the house rat, brown rat, wharf rat, sewer rat, and water

rat. It was first introduced into the United States by European settlers and trading ships around

1775. It is now the most widely distributed rat species in North America and can be

found in all states.

The Norway rat is larger, stronger, more aggressive, and better adapted for producing young

and surviving in colder climates than is the Roof rat or other rat species.

Identification of the Norway rat, is simple. This rat variety has a stocky body, weighing

between 12 and 16 ounces as an adult. The body fur is course and ranges from reddish to

grayish brown, with buff white under parts, but there are many color variations including the all

black Norway rat. The nose is blunt, the ears are small and close -set and do not reach the eyes

when pulled down. The tail is scaly and shorter than the combined length of the head and body.

Breeding periods for the Norway rat are normally in the spring and fall of the year, decreasing

during the hot months of summer and the cold of winter. After mating and a gestation period

of around 22 days, the mother gives birth to a litter consisting of from 8 to 12 pups. The

young are naked and blind at birth and open their eyes in about 9 to 14 days; they are weaned

10 to 15 days after that. The pups are curious at about this stage and begin to take short ex-

ploratory trips around their surroundings and are taught by the mother how to find food, water,

and how to hide from danger. The average female may have from 4 to 7 litters per year and

may successfully wean 20 or more pups annually.

Norway