brown rat, (Rattus norvegicus), species of rat found on every continent except Antarctica. The alternate name “Norway rat” came from a false hypothesis widely believed in 18th-century England  that the rats were native to Norway. Research has confirmed, however, that the brown rat is native to Asia, specifically northern China or Mongolia. Outside its native region the brown rat is a largely disliked pest and an invasive species, though the animal is widely used in biomedical research and is sometimes kept as a pet.

The brown rat may weigh up to 0.5 kg (about 1 pound), twice as much as the average house rat (Rattus rattus), with males typically weighing more than females. The fur is most often gray or brown with a lighter face and underside; domesticated brown rats can also be white or mottled. Their long tails are covered in a thin layer of fur and are thus frequently mistaken as bald. The length of the tail often comes close to the length of the body.

It is thought that as agriculture  developed in China, brown rats began living close to farms, where a consistent source of food was present. From there, the species likely spread gradually to southeastern Asia, then north to Japan and Russia, before moving westward to Europe by the mid-1500s. Scientists have theorized that as Western Europe colonized other parts of the world, the brown rat followed. The animals likely reached North America about 1750. According to recent research on rats in New York City, most brown rats living in the eastern United States, South America, Africa, and New Zealand descended from the rats of Western Europe. Scientists were surprised by the lack of genetic diversity in the New York City rats; it seemed as though even if brown rats were arriving from elsewhere on ships and other transport, the established population of rats were rejecting the newcomers aggressively enough that these foreign communities could not thrive. This aggression has likely aided brown rats in their global spread as an invasive species.

Brown rats are widely considered to be the first mammal domesticated for laboratory research. It was in 19th century Europe that brown rats were first used for research purposes; they were a suitable choice for research due to their abundance and negative reputation. Since then, laboratory rats have become integral to biomedical research. They differ in appearance from wild brown rats—laboratory rats are often albino, or white with red eyes—and in behavior, as laboratory rats are more docile than the wild brown rat.

Rats are members of the rodent family and the genus Rattus. Currently, there are more than 60 species of rats around the world, and the most common is the brown rat (Rattus norvegicus), also known as the Norway rat.

While rats are met with revulsion in most parts of the world, some communities put rodents pride of place on the dinner menu.
Before going to sleep, you ought to make sure no food is left forgotten somewhere on the floor or table. Otherwise, you may end up with some familiar and unwelcome guests: rats. Just a glimpse of a furry rodent is enough to inspire revulsion and complaints to authorities – for example, New York has recently renewed efforts to solve a ‘rat crisis’ in the city. But such guests are not despised everywhere. In fact, in some places around the world, rats are considered a delicious delicacy.
On 7 March every year, in a remote village in the hills of north-east India, the Adi tribe celebrates Unying-Aran, an unusual festival with rats as the culinary centrepiece. One of the Adi’s favourite dishes is a stew called bule-bulak oying, made with the rat’s stomach, intestines, liver, testes, foetuses, all boiled together with tails and legs plus some salt, chili and ginger.
Rodents of all kind are welcomed in this community, from the household rats often seen around the house to the wild species that dwell in the forest. The rat's tail and feet are particularly appreciated for their taste, says Victor Benno Meyer-Rochow, at Oulu University, Finland, who interviewed several members of the Adi tribe for a recent study into rats as a food resource.

https://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Hoplomys_gymnurus2.jpg/1600px-Hoplomys_gymnurus2.jpg?20101111150922

Thrinacodus albicauda = Olallamys albicauda

Echimyidae is the family[2] of Neotropical  spiny rats and their fossil relatives.[3] This is the most species-rich family of hystricognath  rodents. It is probably also the most ecologically diverse, with members ranging from fully arboreal to terrestrial to fossorial to semiaquatic habits.[4] They presently exist mainly in South America; three members of the family also range into Central America, and the hutias are found in the West Indies in the Caribbean. Species of the extinct subfamily Heteropsomyinae formerly lived on Cuba, Hispaniola, and Puerto Rico in the Antilles.

Rats are members of the rodent family and the genus Rattus. Currently, there are more than 60 species of rats around the world, and the most common is the brown rat (Rattus norvegicus), also known as the Norway rat.