Brown rat

The brown rat (Rattus norvegicus), also known as the common rat, street rat, sewer rat, Hanover rat, Norway rat, Norwegian rat, Parisian rat, water rat, or wharf rat, is one of the best known and most common rats. One of the largest muroids, it is a brown or grey rodent with a head and body length of up to 28 cm (11 in) long, and a tail slightly shorter than that. It weighs between 140 and 500 g (4.9 and 17.6 oz). Thought to have originated in northern China, this rodent has now spread to all continents except Antarctica, and is the dominant rat in Europe and much of North America, making it, by at least this particular definition, the most successful mammal on the planet alongside humans. With rare exceptions, the brown rat lives wherever humans live, particularly in urban areas. Selective breeding of the brown rat has produced the fancy rat as a pet, as well as the laboratory rat – rats used as model organisms in biological research. Originally called the 'Hanover rat' by people wishing to link problems in 18th century England with the House of Hanover, it is not known for certain why the brown rat is named Rattus norvegicus (Norwegian rat), as it did not originate from Norway. However, the English naturalist John Berkenhout, author of the 1769 book Outlines of the Natural History of Great Britain, is most likely responsible for popularizing the misnomer. Berkenhout gave the brown rat the binomial name Rattus norvegicus, believing it had migrated to England from Norwegian ships in 1728. By the early to middle part of the 19th century, British academics believed that the brown rat was not native to Norway, hypothesizing (incorrectly) that it may have come from Ireland, Gibraltar or across the English Channel with William the Conqueror. As early as 1850, however, a new hypothesis of the rat's origins was beginning to develop. The British novelist Charles Dickens acknowledged this in his weekly journal, All the Year Round, writing: Academics began to prefer this etymology of the brown rat towards the end of the 19th century, as seen in the 1895 text Natural History by American scholar Alfred Henry Miles: Though the assumptions surrounding this species' origins were not yet the same as modern ones, by the 20th century, it was believed among naturalists that the brown rat did not originate in Norway, rather the species came from central Asia and (likely) China. The fur is coarse and usually brown or dark grey, while the underparts are lighter grey or brown. The brown rat is a rather large murid and can weigh twice as much as a black rat (Rattus rattus) and many times more than a house mouse (Mus musculus). The head and body length ranges from 15 to 28 cm (5.9 to 11.0 in) while the tail ranges in length from 10.5 to 24 cm (4.1 to 9.4 in), therefore being shorter than the head and body. Adult weight ranges from 140 to 500 g (4.9 to 17.6 oz). Exceptionally large individuals can reportedly reach 900 to 1,000 g (32 to 35 oz) but are not expected outside of domestic specimens. Stories of rats attaining sizes as big as cats are exaggerations, or misidentifications of larger rodents, such as the coypu and muskrat. In fact, it is common for breeding wild brown rats to weigh (sometimes considerably) less than 300 g (11 oz).