Norway Rat

Rattus norvegicus

The Norway Rat is a large rodent, growing up to 18 inches long, including the tail. Males are larger than females. The rat's color is grayish-brown with a pale gray belly. Ears and tail are bald.

Norway Rats are found anywhere there are people. This rat, originally from Asia, has followed people around the world, and it is now found throughout the United States. Common places Norway Rats live are ditches, basements, sewers, old buildings, barns, dumps, woods, fields, ponds, and marshes.

Norway Rats are almost always found near water. They are very good swimmers and climbers.

Copyright 2002,

Copyright, Dr. Antonio J. Ferreira, California Academy of Science

Boise State University

Norway Rats always live in large groups in burrows. Rat burrows are actually a large network of passageways, runways, and chambers.

A rat pack hunts together, breeds together, and defends the burrow together.

Rats breed often and each female may have seven litters in a year. Each litter has 2 to 14 young. A rat is full grown in about four weeks. Rat nests are made of leaves, twigs, and trash.

Norway Rats only live two or three years.

Norway Rats will eat just about anything. Natural foods include seeds, grains, fruits, stems, leaves, nectar, flowers, roots, bark, wood, sap, insects, spiders, crayfish, earthworms, frogs, salamanders, fish, lizards, birds, eggs, and fungus.

Rats are very good at catching fish with their paws. They will also eat carrion (dead animals).

The main food of rats, though, is supplied by people. Norway Rats will eat anything that is edible from human garbage. They often build their burrows where they know there is a reliable human trash source nearby. This is why places with lots of people, especially cities, also have lots of rats.

Like most rodents, these rats cache their food. This means they store it in piles in some of the chambers in their burrows.

Norway Rats will swim, climb, and even crawl across telephone wires to get to food. Rats use their very strong sense of smell to find food. They do most of their hunting at night.

E. J. Taylor, ASM Slide Laboratory

Rats have many predators, including snakes, fox, skunks, weasels, owls, hawks, cats, and dogs. These predators are very important since they control rat populations.

Norway Rats disperse seeds when they eat them and poop them out in new places. This helps plants spread.

Rats also help plants grow by aerating soil. This means they put oxygen into the soil when they dig. This makes plants healthier in those areas.

Rats communicate with one another using squeaks, whistles, and chirps.

Copyright, Ray Hamblett 2003-2004

Relationships in Nature:


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Striped Skunk

Common Reed

Meadow Vole EC

Eastern Forest Snail

Barred Owl

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Common Black Ground Beetle

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Common Cattail

Field Cricket

Black Rat Snake

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Differential Grasshopper

Red-tailed Hawk

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Marsh Bulrush

Five-lined Skink


Pennsylvania Smartweed

Least Shrew

Virginia Opossum

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Wood Frog

Domestic Dog

Lamb's Quarters


Blue Jay


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Great Horned Owl

Common Elderberry

Black Oak


Mockernut Hickory

Bracken Fern

Red Maple

Black Willow

Chinese Mantid

Wild Grape

Kentucky Bluegrass

Relationship to Humans:

The lives of Norway Rats are tied very closely to the lives of people. Humans and rats have formed a type of relationship known as Commensalism. This is when one species helps another species, but doesn't get help in return. People help rats without trying when they provide large amounts of food in their garbage. Rats make their burrows and nests near people.

Sometimes Norway Rats cause great damage. They poop on stored food which contaminates it (makes it unsafe to eat). They cause fires when they chew on wires or matches. They have caused flooding by tunnelling through dams.

Rats are also known to carry diseases. Some of these diseases have caused the deaths of many people.

Humans do use Norway Rats in science experiments when studying diseases and medicines.


Rattus norvegicus


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