Animal
Brown rat
The brown rat is a clever rodent with a long tail and a twitchy nose. It first lived in Asia, and now it lives near people almost everywhere.
Brown rats are large rodents that came from East Asia and spread around the world with people, mainly on ships. They are smart, strong swimmers with a superb sense of smell. Wild rats can carry germs that make people sick, so they are best left alone.
Rattus norvegicus, despite its name, is native to temperate East Asia. Carried by human settlement and maritime trade, it now lives on every continent except Antarctica, where it is a costly pest, a carrier of zoonotic diseases and a predator of island seabirds, and also, in domesticated form, a key model organism in research.
Photo: Charles J. Sharp, CC BY-SA 4.0, via Wikimedia Commons
Meet the brown rat
The brown rat is a rodent, like a big cousin of the mouse.
It has brown fur, a pointed nose, bright dark eyes and a long tail with almost no fur. Brown rats are very clever.
The brown rat, also called the Norway rat, is a large rodent. Its body is 15 to 27 centimeters long, its almost bare tail is a little shorter than its body, and it weighs 140 to 500 grams. Males are usually bigger than females.
Wild brown rats have coarse brown or gray-brown fur that is paler underneath, a pointed snout and small, beady eyes. Pet rats and laboratory rats are tame forms of this same species.
Rattus norvegicus is a large murid rodent: the Woodland Trust gives a head-and-body length of 15 to 27 centimeters, and Animal Diversity Web a mass of 140 to 500 grams and an average nose-to-tail length of about 400 millimeters. Males are usually larger. Wild rats have coarse brown fur, sometimes flecked with black or white, shading to gray or tan below; the ears and tail are nearly hairless, and the tail is shorter than the body. ADW notes that its ears are shorter than those of related rats.
The name Norway rat is misleading: the IUCN considers the species native to temperate East Asia. Its domesticated form is kept as a pet, particularly in Europe and North America, and used as a model organism across the life sciences.
Quick facts
- Group
- Mammal
- Length
- 0.15 to 0.27 m
- Weight
- 0.14 to 0.5 kg
- Lifespan in the wild
- up to 4 years
From East Asia to everywhere
Brown rats first lived in Asia.
They traveled with people on ships, and now they live in most places where people live. They like spots near water.
Brown rats first lived in East Asia, probably in China and nearby lands. Over many centuries they spread with people, reaching most of Europe by the 1700s and then, mainly on ships, the Americas, Africa, Australia and many islands. Today they live on every continent except Antarctica.
Most brown rats live near people, in towns, farms and ports. They also live along rivers, lake shores and marshes. Our photo shows one at the water's edge in Drenthe, in the Netherlands.
The IUCN's 2025 global assessment places the ancestral range in eastern China and nearby northeastern Asia, including southeastern Siberia and Japan, though the original boundaries are uncertain. Genomic and archaeological evidence suggests the species left East Asia in the late Holocene, reached southeast and western Asia, spread through much of Europe by the 18th century and then, mainly via maritime trade, reached the Americas, Africa, Australasia and many islands. ADW records the first New World sightings in the 1770s.
The IUCN calls it one of the most widespread land mammals. It follows human settlement in temperate and tropical regions below about 3,250 meters, and in temperate areas also lives along riverbanks, lake shores, marshes and estuaries; in the tropics it is mostly restricted to human-altered places. The hero photo, from Drenthe in the Netherlands, shows a rat in its introduced range.
Continents
Its habitat
Where can you find this animal?
- Brought here by people · Countries and seas named by a scientific source
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
Brought here by people · Countries and seas named by a scientific source
Spread by people, mainly through settlement and sea trade, to Europe, the Americas, Africa, South and Southeast Asia, Australasia and many islands. These are the countries the IUCN lists as introduced.
Places: Afghanistan, Albania, Algeria, Angola, Azerbaijan, Argentina, Australia, Austria and 147 more places.
Source: iucn-red-list · checked October 2026
Lives here naturally · Countries and seas named by a scientific source
Temperate East Asia: probably eastern and northeastern China, southeastern Siberia and Japan, though the original boundaries are uncertain. Shading is by country, so it covers far more than the native area.
Places: China, Japan, Mongolia and Russia.
Source: iucn-red-list · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in Belgium, UK, Netherlands, France, Spain, United States, Germany, Switzerland and 131 more places.
Source: gbif · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
Eat almost anything
Brown rats eat lots of different foods.
They eat seeds, grain, fruit, eggs and bugs. In towns, they eat food that people throw away.
Brown rats are omnivores that eat almost anything. On farms, grain is an important part of their diet, and they also eat fruit, seeds, eggs, insects and other small animals. Some even dive into rivers to catch shellfish.
In towns and cities, much of their food is what people throw away, which is why they gather near bins and compost heaps. Rats use their sense of smell and touch to find food, and they often store food in their burrows.
The IUCN describes an omnivorous, opportunistic diet of plant and animal matter and human waste, with predation on invertebrates and small vertebrates including amphibians, reptiles, birds, hatchlings, eggs and even fish. The Woodland Trust notes that cereals are important on farmland and that rats can dive for molluscs in rivers where they are plentiful; in cities, discarded food dominates (ADW).
Rats find food mainly by smell and touch and cache it in burrow chambers. Their feeding has wider effects. ADW notes that foraging rats disperse seeds and their burrows aerate soil, while the IUCN reports that on oceanic islands, without predators or competitors, invading rats have caused significant harm to native animals such as seabirds.
Super sniffers and swimmers
A brown rat's best sense is smell.
Its whiskers and paws help it feel its way in the dark. It is a great swimmer, and it washes itself carefully for a long time every day.
Smell is the brown rat's best sense. Rats use it to find food and to recognize the members of their group. Their whiskers and paws let them feel their way in total darkness, and they can sense tiny vibrations in the ground.
Brown rats are excellent swimmers, which is why some people call them water rats. They are also very clean animals that spend hours grooming their fur, and they are fast learners that remember routes through complicated tunnels.
ADW describes scent as the brown rat's best sensory channel, used to find food and to tell group members apart, supported by good hearing, sensitivity to minute ground vibrations, and paws and whiskers that guide it through total darkness. Communication combines calls, body postures, pheromones and scent marks.
Brown rats are strong swimmers and divers. They learn quickly and remember complex routes through burrows and tunnel networks, and their learning has been studied in depth by psychologists. Contrary to their reputation, the Woodland Trust notes, brown rats keep themselves very clean and spend hours grooming.
Big families, shared nests
Baby rats are called pups.
They are born with no fur, and their eyes are closed. Mother rats often share a nest and help feed each other's babies.
Brown rats can have babies all year, and a female may have five or more litters a year. About three weeks after mating, she gives birth to a litter of usually 6 to 11 pups. Each newborn weighs about 5 grams and is blind and hairless.
The pups open their eyes at 14 to 17 days and stop drinking milk at 3 to 4 weeks. Often several mothers share one nest and care for all the pups together. Rats are grown up at 3 to 4 months.
Breeding continues year-round, with more mating in warmer months. Gestation is 22 to 24 days (ADW). Litters are typically 6 to 11 (Woodland Trust), averaging about 8 (ADW) within a range of 2 to 14. A postpartum estrus about 18 hours after birth lets a female breed again at once, and ADW gives up to about seven litters a year.
Newborns weigh about 5 grams and are altricial; their eyes open at 14 to 17 days and they are weaned at 3 to 4 weeks and independent at 4 to 5 weeks. Litters of several females often share a nest, and the females nurse young regardless of whose they are, so ADW describes the species as something of a cooperative breeder. Sexual maturity comes at 3 to 4 months. ADW says wild rats are thought to live upwards of 2 years, and gives a maximum of 4 years in captivity.
Night shift in the burrow
Brown rats are busy at night.
They live in groups and dig burrows with rooms for sleeping and storing food. They remember the paths to good food.
Brown rats are mostly active at night and at dusk. That is when they dig, look for food and build nests from leaves, twigs or anything soft they can find.
They live in groups, usually led by larger males, and dig burrows with tunnels and rooms for nesting and storing food, often near water. On their nightly trips they follow routes they have learned. They talk with squeaks, body postures and smells. Owls, foxes, cats and snakes hunt them.
Mostly nocturnal or crepuscular, brown rats dig, forage and build nests from leaves, twigs or refuse in the dark (ADW). Burrow systems with food-storage, nesting and escape chambers are usually dug in moist soil near water, waste or food stores, and are used communally (IUCN).
Rats live in loose colonies or larger groups dominated by bigger males, with hierarchies based on size; territories can be about 50 meters across. New groups begin when a pair nests in an unoccupied area. Foraging follows learned routes to rich food sources. Predators include dogs and foxes, owls, cats, and snakes and lizards, and people kill very large numbers as pests.
Did you know?
Some rats can catch fish with their paws.
Some brown rats living by the sea have been seen catching fish with their paws.
ADW reports coastal brown rats catching fish with their paws, and the Woodland Trust describes rats diving for molluscs in rivers.
Rats and people
There are lots of brown rats, and they are not in danger.
Wild rats can carry germs that make people sick. So we watch them from a distance and never touch them. Pet rats are a tame kind.
Brown rats are not in danger: the IUCN lists them as Least Concern. On some islands, rats brought by ships prey on seabirds, so people remove the rats to protect the birds.
Wild rats can carry germs that cause diseases in people, and a rat can carry them without looking sick. Health experts advise never touching wild rats, their nests or droppings. Tame rats are different: many people keep them as pets, and scientists study them to learn about health and medicine.
The IUCN assessed Rattus norvegicus as Least Concern in 2025 (published 2026), with a stable population, no major threats and no conservation action required. As an invasive pest it is targeted by control and eradication programs worldwide, including on islands where it preys on seabirds; the Woodland Trust notes eradications on UK islands to protect seabird colonies.
The IUCN identifies it as a problematic pest that damages stored food, infrastructure and electrical systems, and notes that wild populations are vectors and reservoirs of numerous zoonotic diseases. The CDC explains, for example, that rats and other rodents can carry rat-bite fever bacteria without showing signs of illness. Domesticated rats are kept as pets and are a model organism across many life sciences (IUCN).
IUCN Red List
How is the brown rat doing in the wild?
- Least Concern (this animal)
- Near Threatened
- Vulnerable
- Endangered
- Critically Endangered
- Extinct in the Wild
- Extinct
Least Concern
Not at risk of disappearing from the wild right now.
See the IUCN Red List assessment · The IUCN Red List of Threatened Species 2022.2
Amazing facts
-
Brown rats keep themselves very clean.
Brown rats spend hours grooming themselves and keep their fur very clean.
The Woodland Trust notes that brown rats keep themselves very clean and spend hours grooming.
-
The Norway rat did not come from Norway.
The brown rat is also called the Norway rat, but it first lived in East Asia.
Despite the name Rattus norvegicus, the IUCN considers the species native to temperate East Asia.
-
Mother rats help feed each other's babies.
Several mother rats often share one nest and nurse all the pups, not just their own.
Communal nesting, with females nursing young regardless of parentage, makes the brown rat something of a cooperative breeder (ADW).
-
Some rats can catch fish with their paws.
Some brown rats living by the sea have been seen catching fish with their paws.
ADW reports coastal brown rats catching fish with their paws, and the Woodland Trust describes rats diving for molluscs in rivers.
Words to know
- rodent
- a gnawing mammal with long front teeth, such as a rat, mouse or squirrel
- omnivore
- an animal that eats both plants and animals
- introduced
- brought by people to a place where it did not live before
- invasive species
- a living thing brought to a new place where it spreads and causes harm
- groom
- to clean and tidy fur
Discovery challenge
-
What is a brown rat's best sense?
Which sense does a brown rat rely on most?
Which is the brown rat's primary sensory channel?
- Sight
- Smell
- Taste
Show the answer
Smell
Smell! Rats have super noses.
Smell. Rats use it to find food and to recognize members of their group.
Olfaction, supported by touch, hearing and sensitivity to ground vibrations (ADW).
-
Where did brown rats first live?
The brown rat is also called the Norway rat. Where did it first live?
Where is Rattus norvegicus native?
- Norway
- Antarctica
- East Asia
Show the answer
East Asia
They first lived in Asia.
In East Asia, probably China and nearby lands. It reached Europe much later, carried by people.
Temperate East Asia, probably eastern China and adjacent northeastern Asia (IUCN).
-
How do mother rats help each other?
How do female brown rats often care for their pups?
Which behavior makes the brown rat something of a cooperative breeder?
- They share a nest and feed all the pups
- They leave the pups alone in trees
- They carry the pups on their tails
Show the answer
They share a nest and feed all the pups
They share a nest and feed each other's babies.
Several mothers often share one nest and nurse all the pups together.
Communal nesting, with females nursing young regardless of whose they are (ADW).
-
Why should we not touch wild rats?
Why do health experts say never to handle wild rats?
Why does handling wild brown rats carry a health risk?
- They are too heavy to lift
- They can carry germs that make people sick
- They are always asleep
Show the answer
They can carry germs that make people sick
Wild rats can carry germs. Watch them, but do not touch.
Wild rats can carry germs, even when they look healthy, so it is safest to leave them alone.
Wild populations are vectors and reservoirs of numerous zoonotic diseases (IUCN), and carriers may show no signs of illness (CDC).
Places where you might see it
-
Watch
Country
China
China is the largest country in Asia, almost as big as all of Europe. The land steps down from the high, cold Plateau of Tibet in the west to plains and coasts in the east, and about 1.4 billion people live there, along with giant pandas in the mountains of south-central China.
-
Watch
Country
Japan
Japan is an island country in East Asia. Most of its land is steep mountains and forest, Mount Fuji is its tallest peak, and about 124 million people live there, many of them in big cities such as Tokyo.
Explore next
-
Watch
3D
Animal
House mouse
House mice are small rodents that first lived in Europe, Asia and North Africa. By living alongside people, they have spread to every continent except Antarctica. They are quick runners and can have babies when only a few weeks old.
-
Watch
3D
Animal
Golden hamster
Golden hamsters, also called Syrian hamsters, are popular pets all over the world. But in the wild they live only in a small area of farmland on the border of Syria and Türkiye, and the IUCN lists them as Endangered.
-
Watch
Animal
Barn owl
The barn owl is a pale, ghostly owl with a heart-shaped face that works like a dish to collect sound. It hunts mice and voles at night over fields and grassland, finding them by hearing alone if it has to. Barn owls live on every continent except Antarctica.
-
Watch
Country
China
China is the largest country in Asia, almost as big as all of Europe. The land steps down from the high, cold Plateau of Tibet in the west to plains and coasts in the east, and about 1.4 billion people live there, along with giant pandas in the mountains of south-central China.
-
Watch
Country
Japan
Japan is an island country in East Asia. Most of its land is steep mountains and forest, Mount Fuji is its tallest peak, and about 124 million people live there, many of them in big cities such as Tokyo.
-
Watch
Animal
Naked mole-rat
Naked mole-rats are almost hairless rodents that spend their whole lives in tunnels under the dry lands of eastern Africa. They live in big colonies where only one female, the queen, has babies, and they can live for around 30 years.
-
Watch
Animal
Aardvark
The aardvark is a shy night digger of African savannas. It sniffs out ant and termite nests, rips them open with its spade-like claws and laps up the insects with a sticky tongue about 30 centimeters long. Its name means 'earth pig' in Afrikaans.
-
Watch
Animal
African buffalo
The African buffalo is a huge, cow-like grazer with heavy, curving horns. It lives in herds that can number in the thousands, and a herd will rush to protect a calf in danger. It lives across much of Africa south of the Sahara, from open savannas to rainforests.
For parents & teachers
What children will learn
- Explain that the brown rat is native to East Asia and spread worldwide with people.
- Describe the rat's senses, especially smell and touch.
- Describe the brown rat's life cycle and communal nesting.
- Explain why wild rats should not be handled, and how tame rats help research.
Recommended ages: 3 to 17 · About 15 minutes
Talk about it
- How might trading ships have carried rats around the world?
- Why might rats be a problem for seabirds on islands that never had rats before?
- Why do you think a rat's sense of smell matters more than its eyesight?
Try at home or in class
- Put a few foods with different smells in covered cups and try to identify them by smell alone, like a rat.
- On a world map, trace a possible trading-ship route from China to Europe and on to the Americas.
Key vocabulary: rodent, omnivore, introduced, invasive species, groom
Where these facts come from
- The IUCN Red List of Threatened Species , International Union for Conservation of Nature (IUCN terms of use (no redistribution of Red List data or range maps))
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Rattus norvegicus (global assessment, 2026) , IUCN Red List
- Rattus norvegicus (brown rat) , Animal Diversity Web, University of Michigan
- Brown rat , Woodland Trust
- About Rat Bite Fever (RBF) , U.S. Centers for Disease Control and Prevention
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 28, 2026. Spotted a mistake? Tell us.