Rat

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This is an article about wild rats. For pet rats, see Fancy rat. For other uses, see Rat (disambiguation).
iRats
Fossil range: Early Pleistocene - Recent
Image:Rattus rattus05.jpg
Black Rat (Rattus rattus)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Superfamily: Muroidea*
Family: Muridae
Subfamily: Murinae
Genus: Rattus
Fischer de Waldheim, 1803
Species

50 species; see text
*Several subfamilies of Muroids
include animals called rats.

A rat is any one of about 56 different species of small, omnivorous rodents belonging to the genus Rattus.

Contents

The Rat

The best-known rat species are the Black Rat Rattus rattus and the Brown Rat R. norvegicus. The group is generally known as the Old World rats or true rats, and originated in Asia. Rats are bigger than most of their relatives, the Old World mice, but seldom weigh over 500 grams (1 lb) in the wild. The common term "rat" is also used in the names of other small mammals which are not true rats. Examples include the North American pack rats, a number of species loosely called kangaroo rats, and a number of others. Other rats such as the Bandicoot rat Bandicota bengalensis are murine rodents related to the true rats, but are not members of the genus Rattus. The widely distributed and problematic commensal species of rats represent a minority in this diverse genus. Many species of rats are island endemics and some have become endangered due to habitat loss or competition with brown, black, or Polynesian rats.

In Western countries, many people keep domesticated rats as pets. These are of the species R. norvegicus, which originated in the grasslands of China and spread to Europe and eventually, in 1775, to the New World. Pet rats are Brown Rats descended from those bred for research, and are often called "fancy rats", but they are still the same species as the common city "sewer" rat. Domesticated rats tend to be both more docile than their wild ancestors and more disease prone, presumably due to inbreeding.

The common species are opportunistic survivors and often live with and near humans. The Black Plague is traditionally believed to have been caused by the micro-organism Yersinia pestis, carried by the rat flea Xenopsylla cheopis which preyed on R. rattus living in European cities of the day; it is notable that these rats were victims of the plague themselves. It has recently been suggested that neither rats nor infected fleas would have spread fast enough through Europe to be a likely culprit, although this is controversial and research continues.[citation needed] Regardless, rats are frequently blamed for damaging food supplies and other goods. Their reputation has carried into common parlance: in the English language, "rat" is an insult and "to rat on someone" is to betray them by denouncing to the authorities a crime or misdeed they committed. While modern wild rats can carry Leptospirosis and some other "zoonotic" conditions (those which can be transferred across species, to humans, for example), these conditions are in fact rarely found.[citation needed] Wild rats living in good environments are typically healthy and robust animals. Wild rats living in cities may suffer themselves from poor diet and internal parasites and mites, but do not generally spread disease to humans.

The rat makes a fine pet, known for its intelligence, playfulness and sociability. They are extremely clean. Rats can be taught entertaining tricks, in the same way as many other domesticated animals. It has been observed that rats can actually last longer without water than camels.

Rats have a normal lifespan ranging from two to five years, though three years is typical.

Rats in culture

Ancient Romans did not generally differentiate between rats and mice, instead referring to the former as Mus Maximus (big mouse) and the latter as Mus Minimus (little mouse).

In Imperial Chinese culture, the rat (sometimes referred to as a mouse) is the first of the twelve animals of the Chinese zodiac. People born in this year are expected to possess qualities associated with rats. These include creativity, honesty, generosity, ambition, a quick temper and wastefulness. "Rats" (i.e. people born in a year of the rat) are said to get along well with "monkeys" and "dragons," and to get along poorly with "horses."

Image:Ganesha on mouse.jpg
Ganesh riding on his mouse. Note the flowers offered by the devotees. A sculpture at the Vaidyeshwara temple at Talakkadu, Karnataka, India

In India in the northwestern city of Deshnoke, the Karni Mata Temple, the rats are held to be destined for reincarnation as Sadhus, Hindu holy men. The attending priests feed milk and grain, of which the pilgrims also partake, to the animals. Eating food that has been touched by the animals is considered a blessing from god. In Hindu mythology, a rat is the vehicle of Ganesha.

Western associations with the rat are generally negative. For instance, "Rats!" is used as a substitute for various vulgar interjections. These associations do not draw, per se, from any biological or behavioral trait of the rat, but possibly from the association of rats (and fleas) with the 14th-century medieval plague called the Black Death. Rats are seen as vicious, unclean, parasitic animals that steal food and spread disease. While undomesticated rats, dogs, and cats may all be pests in urban areas, in Western countries poisoning rats is commonly accepted, while doing the same to feral dogs and cats would be an unpopular solution in the view of many people. Mutant, man-eating rats are the monsters in James Herbert's horror novel The Rats and its sequels. A phobia of rats is used as a torture device in the novel Nineteen Eighty-Four by George Orwell'. Rats are the most common enemy in Brian Jacques's Redwall series of anthropomorphic fantasy novels. There are obvious exceptions; for example, the characters of Mrs. Frisby and the Rats of NIMH, the television series Ratz and Terry Pratchett's The Amazing Maurice and his Educated Rodents. Describing a person as "rat-like" usually implies he is unattractive and suspicious. In contrast, mice are stereotyped as cute and bourgeois.

On the Isle of Man (British Protectorate) there is a taboo against the word "rat." See longtail for more information.

Rat is also a term (noun and verb) in criminal (often Mafia) slang for a criminal informant.

Rats are often used in scientific experiments; many animal rights activists allege that treatment of rats in this context is cruel. The term "lab rat" is therefore sometimes used, like guinea pig, to describe a person who is manipulated in a social experiment.

Rats as vermin

By most standards, rats are considered pests or vermin. They can be very destructive to crops and property. Rats can quickly overpopulate when they live in a place where they have no predators, such as in certain cities, and their numbers can become hard to contain. Because of this, the entire province of Alberta, Canada has upheld and maintained a rat-free status since the early 1950s; it is even illegal to keep pet rats there.

Rats have a significant impact on food production. Estimates vary, but it is likely that anything between one-fifth and one-third of the world's total food output is eaten, spoiled or destroyed by rats and other rodents.[1],[2]

Rats can carry over thirty different diseases dangerous to humans, including Weil's disease, typhus, salmonella and bubonic plague. Black rats are suspected to have had a role in the Black Death, an epidemic which killed at least 75 million people in Europe, the Middle East, and Asia in the mid-late 14th century.

A variety of rat control methods have been used throughout human history to either reduce or eliminate rat populations in homes, markets, farms, and industrial sites. The two most widely used methods are rat poison and rat traps, though cats and dogs have also been employed to hunt rats. Professional rat-catchers can be found in many developing countries.

Because rats are nocturnal, daytime sightings of rat activity can mean that their nesting areas have been disturbed or, more likely, that there is overpopulation of them in the local area. [3] It is typically at this point that vermin control measures tend to increase.

Rats often chew electrical cables. Around 26% of all electrical cable breaks are caused by rats, and around 18% of all phone cable breaks. Around 25% of all fires of unknown origin are estimated to be caused by rats.[4]

Rats, particularly roof rats (Rattus rattus), can enter the attics of homes where they mate and nest. This problem occurs commonly in coastal, temperate climates and affects even the cleanest, well-kept homes.

See also

Taxonomy of Rattus

The genus Rattus is a member of the giant subfamily Murinae. There are several other murine genera that are sometimes considered part of Rattus.  : Lenothrix, Anonymomys, Sundamys, Kadarsanomys, Diplothrix, Margaretamys, Lenomys, Komodomys, Palawanomys, Bunomys, Nesoromys, Stenomys, Taeromys, Paruromys, Abditomys, Tryphomys, Limnomys, Tarsomys, Bullimus, Apomys, Millardia, Srilankamys, Niviventer, Maxomys, Leopoldamys, Berylmys, Mastomys, Myomys, Praomys, Hylomyscus, Heimyscus, Stochomys, Dephomys, and Aethomys.

The genus Rattus proper contains 56 species. A subgeneric breakdown of the species has been proposed, but does not include all species. The five groups are:

  • norvegicus group
  • rattus group
  • Australian native rat species
  • New Guinea native rat species
  • xanthurus group

The following list is alphabetical.

Species of rats

Further reading and references

  • The Story of Rats: Their Impact on Us, and Our Impact on Them, S. Anthony Barnett, Allen & Unwin, Crows Nest, NSW, Australia, 2002, trade paperback, 202 pages, ISBN 1-86508-519-7 .
  • Leung LKP, Peter G. Cox, G. C. Jahn and Robert Nugent. 2002. Evaluating rodent management with Cambodian rice farmers. Cambodian Journal of Agriculture Vol. 5, pp. 21-26.
  • Musser, G. G. and M. D. Carleton. 1993. Family Muridae. Pp. 501-755 in Mammal Species of the World a Taxonomic and Geographic Reference. D. E. Wilson and D. M. Reeder eds. Smithsonian Institution Press, Washington D.C.
  • Nowak, R. M. 1999. Walker's Mammals of the World, Vol. 2. Johns Hopkins University Press, London.
  • Sullivan, Robert. 2004. Rats - A Year with New York´s Most Unwanted Inhabitants. Granta Books, London.

External links

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Rat

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