Norway Rat Facts & How to Get Rid of the Rodents

General Information

What is a Norway rat?
Also known as brown rats or sewer rats, Norway rats live on every continent in the world except Antarctica. The widespread rodents are the species of pest rat most commonly found in the United States, where the vermin tend to inhabit urban and suburban neighborhoods like those established throughout New England. Scientifically named Rattus norvegicus, Norway rats frequently live among humans in populated areas where sources of food and water are plentiful. The common name, Norway rat, stems from the rodent first entering Europe on Norwegian ships in the middle of the 16th century. Norway rats successfully occupy all populated regions of the world by reproducing regularly, adapting easily to a wide range of environments and climate zones, and displacing indigenous rodent species of smaller size. An infestation of Norway rats can cause property damage, contamination of food, and the transmission of various diseases to humans and pets.

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Norway Rat

Appearance & Identification

What does a Norway rat look like?
Larger than mice and most other rats found in New England, the Norway rat boasts an average length of nearly 16 inches, which includes the tail. The rodents are stocky relative to mice and weigh as much as a pound when fully grown. Males typically grow larger than females. The head of the Norway rat is characterized by small ears, tiny eyes, and a blunt nose. The rats are covered in coarse, dark fur that transitions in color to gray or white on the underside of the rodents. The layer of fur does not extend to the ears or tail which remain hairless. Newborn Norway rats are completely bald and only begin growing fur at about two weeks of age.

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Highly adaptable, Norway rats inhabit a variety of different environments ranging from fields and woodlands to dumpsters and sewers. The rodents also reside in the basements of New England homes, particularly in spaces where garbage is permitted to accumulate. Natural burrowers, Norway rats often establish outdoor nests beneath trash heaps, woodpiles, and the concrete foundations of buildings. Indoors, the pest rodents live in wall voids as well as areas cluttered with undisturbed debris such as storage spaces. Norway rats tend to nest in close proximity to each other and form live in groups that function according to a clearly defined hierarchy. The rodents are nocturnal creatures that emerge at dusk to dig burrows, construct nests, and search for food.


What do Norway rats eat?
Like other omnivores, Norway rats adhere to a varied diet largely composed of proteins and carbohydrates like meats and grains. In urban and indoor areas, the foraging rodents primarily subsist on the remnants of food items discarded by humans. Norway rats also feed on seeds and nuts, fruit, leaves and roots, and even other animals like birds, fish, and mice. The omnivorous rodents boast the ability to consume roughly a third of their body weight in food in a single day and travel up to 150 feet from the nest when foraging.

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Prolific breeders, Norway rats mate throughout the year, with periods of increased breeding activity typically occurring during the warmer months. After a gestation period of about three weeks, mated females give birth to litters of eight to 12 offspring. Norway rats are born with closed eyes and hairless bodies. The eyes of newborn Norway rats open after two weeks, which is also the approximate length of time it takes the rodents to grow fur. Weaning takes place at three to four weeks of age, with newly weaned Norway rats leaving the nest about five weeks after birth. The rodents achieve sexual maturity and can begin mating at an age of three or four months. Sexually mature Norway rats retain the ability to breed for two years and produce up to seven litters annually.

Problems Caused by Norway Rats

The presence of Norway rats poses several threats to people, pets, and property. Norway rats living in indoor environments can spread salmonellosis and contaminate food consumed by humans. The rodents also facilitate the transmission of serious diseases like hantavirus, jaundice, plague, and rat bite fever. Norway rats frequently serve as host animals for fleas and lice, as well. Property damage occurs when the pest rodents gnaw through the pipes, wiring, furnishings, and foundations of homes. In fact, rats are estimated to cause an annual total of roughly $1 billion in property damage across the United States.

Signs of a Norway Rat Infestation

Wary of strangers and nocturnal by nature, Norway rats tend to remain out of sight during daytime hours. Nevertheless, the rodents often leave behind telltale signs of their presence. Evidence of a Norway rat infestation includes droppings, which typically measure between one-half and three-fourths of an inch long. The gnawing rodents may also leave holes or teeth marks in objects made of plaster, plastic, soft metal, and wood. Other indicators of an infestation include footprints and runways created by the tendency of Norway rats to travel the same path when outside the nest. Norway rats living within wall voids often produce audible squeaking noises and gnawing sounds.


New England residents can prevent Norway rat infestations by storing food securely, cleaning up spills thoroughly, disposing garbage properly, and removing piles of debris from around their home or building. Homeowners should also seal any holes around and keep outdoor vegetation away from the structural foundation of indoor structures to eliminate cover/harborage for foraging Norway rats. Severe infestations often prove difficult to handle and frequently require the services of a pest control professional with experience in dealing with Norway rats.