Brown Rat Animal

(Mammal)

The brown rat is considered to be a pest throughout most of its range. Still it rarely lives in occupied houses or buildings but, rather, makes its home in areas uninhabited by people. The brown rat inhabits all parts of the world populated by humans and breeds rapidly in colonies located in sewers and garbage dumps. It arrived in the Americas by way of ships belonging to early European explorers and settlers.

Brown Rat Baby

The brown rat is found worldwide, with the exception of the polar regions. It can survive in almost any environment, but it is most commonly found near farms, in garbage dumps, and in sewers. It likes dense cover, where it will dig a series of linking burrows in sloping ground in the side of a ditch. It also prefers to live near water and is a good swimmer. The brown rat lives in colonies where every member recognizes each other by smell. There is a social structure in a colony, but the dominant rats are tolerant of others. Where there is plenty of food available, the rat may need to colonize only small areas no more than several yards in length. In large colonies, such as those found sewers and garbage dumps, the highest-ranking rat will live in the choice spot, close to the food source. The low-ranking rats must often struggle to survive.

The brown rat can be seen scavenging for food near garbage dumps or abandoned buildings. In the country sloping ground is often the site of a rat burrows that are 2-3 inches in diameter. Narrow, well-used paths are often signs that a rat colony is nearby. In buildings, the rat leaves dark, greasy trails near food sources. Rats can also be spotted swimming across canals or rivers.

Brown Rat Communication

Brown rats are capable of producing ultrasonic vocalizations. As pups, young rats use different types of ultrasonic cries to elicit and direct maternal search behavior, as well as to regulate their mother's movements in the nest. Although pups will produce ultrasounds around any other rats at 7 days old, by 14 days old they significantly reduce ultrasound production around male rats as a defensive response. Adult rats will emit ultrasonic vocalizations in response to predators or perceived danger; the frequency and duration of such cries depends on the sex and reproductive status of the rat. The female rat will also emit ultrasonic vocalizations during mating.

Rats may also emit short, high frequency, ultrasonic, socially induced vocalization during rough and tumble play, before receiving morphine, or mating, and when tickled. The vocalization, described as a distinct "chirping", has been likened to laughter, and is interpreted as an expectation of something rewarding. Like most rat vocalizations, the chirping is too high in pitch for humans to hear without special equipment. Bat detectors are often used by pet owners for this purpose.

Brown Rat Breeding

A female brown rat is ready to breed when she is 11 weeks old and weighs four ounces. After mating, the male plays no part in rearing the young.

The female builds a round nest of loose material such as straw. The nest is often located in an underground burrow. After 21-24 days, 6 to 11 young are born blind and hairless. They are totally dependant on their mother, who suckles them for three weeks. At the end of this time, they are ready to leave the nest. A female may sometimes give birth to three to five litters a year. A large colony is often started by a single pregnant female. The black rat, or ship rat, is rarer and can produce almost as many litters as the brown rat, but its females are not ready to breed until they are four months old.

Brown Rat Food & Feeding

The brown rat feeds at night and sleeps through the day. It is most active at dawn and dusk. Although its eyesight is poor, the brown rat has a very keen sense of smell which it uses to locate food. The rat prefers to eat stored or cultivated cereal grains but also eats meat. It eats various types of poultry, including ducklings.

Food is usually carried in its mouth to a safe place where it is eaten. Large items are dragged to a hiding place. The food the rat leaves uneaten is left behind since, unlike many rodents, the brown rat does not hoard food.

Brown Rat Key Facts

Size

Height: Length: Up to 12 in. Tail length: Slightly shorter than body

Weight: Variable: 3-21 oz. Males slightly heavier than females

Breeding

Sexual maturity: Females, 11 weeks

Mating: Throughout the year

Gestation: 21-24 days

Number of young: 6-11, depending on size of mother. Up to 5 litters per year

Lifestyle

Habit: Mostly nocturnal, living in colonies

Diet: Prefers food rich in protein and starch, but will eat anything

Lifespan: 1-2 years, but very few live longer than 1 year

DID YOU KNOW?

It is considered a pest because it is the carrier of many diseases, man has tried for centuries to exterminate it without success. The rat's successful breeding habits and its ability to survive on any food and in most habits ensure its survival.
The brown rat is also called the sewer rat, the barn rat, and the Norwegian rat. Its species name is derived from the later name.
The rat needs a large amount of food to survive and eats the equivalent of a third of its body weight in food every day.
The black rat, a brown rat relative, is thought to have been responsible for transmitting bubonic plague in fourteenth-century Europe.
A single female brown rat can give birth to more than forty young in one year.