Black rat

The black rat (Rattus rattus), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus Rattus, in the subfamily Murinae.[1] It likely originated in the Indian subcontinent, but is now found worldwide.[2]

The black rat is black to light brown in colour with a lighter underside. It is a generalist omnivore and a serious pest to farmers because it feeds on a wide range of agricultural crops. It is sometimes kept as a pet. In parts of India, it is considered sacred and respected in the Karni Mata Temple in Deshnoke.

A typical adult black rat is 12.75 to 18.25 cm (5.0 to 7.2 in) long, not including a 15 to 22 cm (5.9 to 8.7 in) tail, and weighs 75 to 230 g (2.6 to 8.1 oz), depending on the subspecies.[4][5][6][7] Despite its name, the black rat exhibits several colour forms. It is usually black to light brown in colour with a lighter underside. In England during the 1920s, several variations were bred and shown alongside domesticated brown rats. This included an unusual green-tinted variety.[8] The black rat also has a scraggly coat of black fur, and is slightly smaller than the brown rat.

Black rat bone remains dating to the Norman period were discovered in Great Britain. The black rat occurred in prehistoric Europe and in the Levant during postglacial periods.[9] The specific origin of the black rat is uncertain due to its disappearance and reintroduction. Evidence such as DNA and bone fragments also indicate that it did not originate in Europe, but migrated from Southeast Asia, possibly Malaysia. It probably spread across Europe in the wake of the Roman conquest. Possibly, speciation occurred when it colonized southwestern India, which was the primary country from which Romans obtained their spices. Since the black rat is a passive traveler, it could have easily traveled to Europe during the trading between Rome and the Southwest Asian countries. The black rat in the Mediterranean region differs genetically from its Southeast Asian ancestor by having 38 instead of 42 chromosomes. It is a resilient vector for many diseases because of its ability to hold so many infectious bacteria in its blood. It played a primary role in spreading bacteria contained in fleas on its body, such as the plague bacterium (Yersinia pestis) which is responsible for the Plague of Justinian and the Black Death.[10]

A study published in 2015 indicates that other Asiatic rodents served as plague reservoirs, from which infections spread as far west as Europe via trade routes, both overland and maritime. Although the black rat was certainly a plague vector in European ports, the spread of the plague beyond areas colonized by rats suggests that the plague was also circulated by humans after reaching Europe.[11]