Rat

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This is an article about wild rats. For pet rats, see Fancy rat. For other uses, see Rat (disambiguation).
Rats
Fossil range: Early Pleistocene - Recent

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.

Rats are various medium sized rodents. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, R. norvegicus. Many members of other rodent genera and families are also called rats and share many characteristics with true rats. A rat has an average life span of 2-3 years[1].

Rats are distinguished from mice by their size; rats generally have bodies longer than 12 cm (5 inches). Squirrels of most species are about the same size as rats but are members of their own family, Sciuridae, and are usually more specialized than rats.

Contents

  • 1 The Rats
  • 2 Rats as pets
  • 3 Rats as subjects of scientific research
  • 4 Laughter in rats
  • 5 Rats as food
  • 6 Rats in culture
    • 6.1 Eastern cultures
    • 6.2 Western cultures
    • 6.3 Rats in pop culture
    • 6.4 Religion
  • 7 Taxonomy of Rattus
    • 7.1 Species of rats
  • 8 Further reading
  • 9 References and notes
  • 10 See also
  • 11 External links

[edit] The Rats

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. 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. 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 from poor diets and internal parasites and mites, but do not generally spread disease to humans.

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

[edit] Rats as pets

A domesticated rat, trained to stay on its owner's shoulder.
Main article: Fancy rat

Specially bred rats have been kept as pets at least since the late 19th century. Rats are intelligent animals and can be trained to use a litter box, come when called, and perform a variety of tricks. Pet rats are typically of variants of the species R. Norvegicus, or Brown rat, but Black rats and Giant pouched rats are also known to be kept. Pet rats behave differently than their wild relatives depending on how many generations they have been removed, and when acquired from reliable sources, they do not pose any more health risk than other, more common pets.

[edit] Rats as subjects of scientific research

Main Article: Brown rats in science

A domesticated rat, suffering from Diabetes mellitus a metabolic disorder being also a common disease among humans.

In 1895, Clark University in Worcester, Massachusetts (United States) established a population of domestic white brown rats to study the effects of diet and for other physiological studies. Over the years, rats have been used in many experimental studies, which have added to our understanding of genetics, diseases, the effects of drugs, and other topics that have provided a great benefit for the health and wellbeing of humankind. Laboratory rats have also proved valuable in psychological studies of learning and other mental processes (Barnett 2002). A 2007 study found rats to possess metacognition, a mental ability previously only found in humans and some primates.[1]

Domestic rats differ from wild rats in many ways. They are calmer and less likely to bite; they can tolerate greater crowding; they breed earlier and produce more offspring; and their brains, livers, kidneys, adrenal glands, and hearts are smaller (Barnett 2002).

Brown rats are often used model organisms for scientific research. When conducting genetic research rats are much rarer than mice. When it comes to conducting tests related to intelligence, learning and drug abuse rats are a popular choice due to their high intelligence, ingenuity, aggressiveness and adaptability. Their psychology, in many ways, seems to be similar to humans. Entirely new breeds or "lines" of brown rats like the Wistar rat have been bred for use in laboratories. Much of the genome of Rattus norvegicus has been sequenced.[2]

[edit] Laughter in rats

Brown Rat (Rattus norvegicus)

It was discovered that rats emit short, high frequency, ultrasonic, socially induced vocalization during rough and tumble play, and when tickled. The vocalization is described as a distinct “chirping”. Humans cannot hear the “chirping” without special equipment. It was also discovered that like humans, rats have “tickle skin”. These are certain areas of the body which generate more laughter response than other areas. The laughter is associated with positive emotional feelings and social bonding occurs with the human tickler, resulting in the rats becoming conditioned to seek the tickling. Additional responses to the tickling were those that laughed the most also played the most, and those that laughed the most preferred to spend more time with other laughing rats. This suggests a social preference to other rats exhibiting similar responses. However, as the rats age, there does appear to be a decline in the tendency to laugh and response to tickle skin. The initial goal of Jaak Panksepp & Jeff Burgdorf’s research was to track the biological origins of joyful and social processes of the brain by comparing rats and their relationship to the joy and laughter commonly experienced by children in social play. Although, the research was unable to prove rats have a sense of humor, it did indicate rats can laugh and express joy. Panksepp & Burgdorf 2003 Chirping by rats is also reported in additional studies by Brian Knutson of the National Institutes of Health. Rats chirp when wrestling one another, before receiving morphine, or having sex. The sound has been interpreted as an expectation of something rewarding. Science News 2001

[edit] Rats as food

Rats, like all mammals, are edible by humans and are sometimes captured and eaten in emergency situations. For some cultures, rats are considered a staple. Bandicoot rats are an important food source among some peoples in India and Southeast Asia. Among the reasons rat meat is not more widely utilized are the strong prohibitions against it in Islamic and Jewish dietary laws, the prohibition of all meat by many followers in Hinduism, and the rat's bad reputation in many cultures.

As a food, rats are often a more-readily available source of protein than other fauna. Some black slaves in the American South hunted wood rats (among other animals) to supplement their food rations.[3] The aboriginals that lived along the coast in what is currently South Queensland Province, Australia regularly included rats in their diet.[4] In the Mishmi culture of India, rats are essential to the Mishmi traditional diet, as Mishmi women may eat no meat except fish, pork, wild birds and rats.[5] The United Nations Food and Agriculture Organization estimates that rat meat makes up half the locally produced meat consumed in Ghana, where cane rats are farmed and hunted for their meat.

In some cultures, rats are (or have been) limited as an acceptable form of food to a particular social or economic class. In the traditional cultures of the Hawaiians and the Polynesians, rat was a common food. When feasting, the Polynesian people of Rapa Nui could eat rat, but the king was not allowed to due to the islanders' belief in a "state of sacredness" called tapu.[6] In studying pre-contact archaeological sites in Hawaii, archaeologists have found that the concentration of the remains of rats associated with commoner households counted for three times the animal remains associated with elite households. The rat bones found in all sites are fragmented, burned and covered in carbonized material, indicating that rats were eaten as food. The greater occurrence of rat remains associated with commoner households may indicate that the elites of pre-contact Hawaii did not consume them as a matter of status or taste. [7]

The taboo against consuming rats as food is not unique to the world's major religions or Western cultures. Both the Shipibo people of Peru and Sirionó people of Bolivia have cultural taboos against the eating of rats.[8][9]

[edit] 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).

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

[edit] Eastern cultures

A netsuke of a rat from Japan.

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."

The indigenous rats are allowed to run freely throughout the Karni Mata temple.

In Indian tradition rats are recognized as the vehicle of Lord Ganesh and a rat's statue is always found in a temple of Ganesh. 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.

[edit] Western cultures

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. However many people in Western cultures keep rats as pets and conversely find them to be tame, clean, intelligent, and playful. 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.

Describing a person as "rat-like" usually implies he is unattractive and suspicious. In contrast, mice are often stereotyped as cute and bourgeois, although the adjective "mousy" refers to a person who is plain or drab in appearance or timid in behavior.

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.

[edit] Rats in pop culture

[edit] Religion

According to one hadith in Islam, a group of Israelites were cursed and transformed into rats. [11]

[edit] 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:

The following list is alphabetical.

[edit] Species of rats

[edit] Further reading

[edit] References and notes

  1. ^ | Rats Capable Of Reflecting On Mental Processes
  2. ^ Genome project. www.ensemble.org. Retrieved on 2007-02-17.
  3. ^ Otto, John Solomon; Augustus Marion Burns III. (December 1983) Black Folks and Poor Buckras: Archeological Evidence of Slave and Overseer Living Conditions on an Antebellum Plantation. Journal of Black Studies, Vol. 14, No. 2. pp. 185-200
  4. ^ Hobson, Keith A.; Stephen Collier. (April 1984) Marine and Terrestrial Protein in Australian Aboriginal Diets. Current Anthropology, Vol. 25, No. 2. pp. 238-240
  5. ^ Mills, J. P. (January 1952) The Mishmis of the Lohit Valley, Assam. The Journal of the Royal Anthropological Institute of Great Britain and Ireland, Vol. 82, No. 1. pp. 1-12
  6. ^ Leach, Helen. (February 2003) Did East Polynesians Have a Concept of Luxury Foods? World Archaeology, Vol. 34, No. 3, Luxury Foods. pp. 442-457.
  7. ^ Kirch, Patrick V.; Sharyn Jones O'Day. (February 2003) New Archaeological Insights into Food and Status: A Case Study from Pre-Contact Hawaii. World Archaeology, Vol. 34, No. 3. pp. 484-497
  8. ^ Behrens, Clifford A. (September 1986) Shipibo Food Categorization and Preference: Relationships between Indigenous and Western Dietary Concepts. American Anthropologist, New Series, Vol. 88, No. 3. pp. 647-658.
  9. ^ Priest, Perry N. (October 1966) Provision for the Aged among the Sirionó Indians of Bolivia. American Anthropologist, New Series, Vol. 68, No. 5. pp. 1245-1247
  10. ^ Hollywood Rats
  11. ^ Sahih Bukhari 4:54:524