Rat
2008/9 Schools Wikipedia Selection. Related subjects: Mammals
| Rats Fossil range: Early Pleistocene – Recent |
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 Black Rat (Rattus rattus)
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50 species; see text |
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Stenomys Thomas, 1910 |
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 .
Rats are distinguished from mice by their size; rats generally have bodies longer than 12 cm (5 in).
Species and description
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 Old World mice, which are their relatives, but seldom weigh over 500 grams (1 lb) in the wild.
The 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 others. Rats such as the Bandicoot rat Bandicota bengalensis are murine rodents related to true rats, but are not members of the genus Rattus. The widely distributed and problematic commensal species of rats are 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 the Brown, Black or Polynesian rat.
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 are 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; these rats were victims of the plague themselves.
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 (not true in neotropical countries). 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.
The normal lifespan of rats ranges from two to five years, and is typically three years.
As pets
Specially bred rats have been kept as pets at least since the late 19th century. Rats are sociable, 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.
As subjects of scientific research
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.
On January, 2008, Doris Taylor, director, Centre for Cardiovascular Repair, University of Minnesota used the core procedure of decellularisation to let hearts from animal cadavers beat by infusing live cells. The research used dead rats heart (stripped with detergents) and then new cells from baby rats are injected, and the dead heart beat after 8 days. Stem cells from humans can be removed from the recipient of the donated organ, thereby eliminating rejection by the immune system. The resultant transplanted bioartificial organ will benefit many heart patients.
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.
Laughter in rats
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": certain areas of the body that 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 included: 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 in the response to tickle skin. The initial goal of Jaak Panksepp and 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, and before receiving morphine or having sex. The sound has been interpreted as an expectation of something rewarding. Science News 2001
A video about this research is available here
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 Southeast Asia. Reasons why rat meat is not more widely eaten include 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 African captives in the American South hunted wood rats (among other animals) to supplement their food rations. The Aboriginals along the coast in Southern Queensland, Australia regularly included rats in their diet. 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. 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. 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.
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.
Rats are a common food item for snakes, both in the wild, and as pets. Ball pythons in particular, are fed a diet of mostly rats, approximately one rat each week being a typical diet. Rats, as food items, are available from many suppliers who supply to individual snake owners as well as to large reptile zoos like Reptilia, Reptile Rain Forest, etc..
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.
In Eastern cultures
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, including creativity, honesty, generosity, ambition, a quick temper and wastefulness. 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."
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 the northwestern Indian city of Deshnoke, the rats at the Karni Mata Temple are held to be destined for reincarnation as Sadhus ( Hindu holy men). The attending priests feed milk and grain to the rats, of which the pilgrims also partake. Eating food that has been touched by rats is considered a blessing from god.
In 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 behavioural 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 behaviour.
Rat is also a term ( noun and verb) in criminal (often Mafia) slang for a criminal informant. Among unions, "rat" is a term for nonunion employers or breakers of union contracts, and this is why unions use inflatable rats.
Rat Poker Tours are Poker tournaments where common courtesy rules are banned. Chip stealing, insults, physical violence are common and accepted as part of the game in those tournaments.
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 used, typically in a self-effacing manner, to describe a person whose job function requires that they spend a majority of their work time engaged in bench-level research (i.e. a scientist or research assistant).
In religion
- In Leviticus 11:29, rats are prohibited as food.(see 'as food' above)
- According to one hadith in Islam, a group of Israelites were cursed and transformed into rats.
In popular culture
- The Wind in the Willows by Kenneth Grahame features literature's most famous 'rat', Ratty. Ironically, the character is not actually a bona fide rat, but rather a European Water Vole - otherwise known as a water rat, hence Ratty's given name.
- Suzanne Collins's series The Underland Chronicles is about a land underneath the surface of the earth where rats are about 6 feet tall and are generally evil.
- Roland Rat was a major TV personality in 1980s Britain.
- 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.
- In Robin Jarvis's Deptford Mice trilogy of books, many of the villains are sewer rats.
- There are obvious exceptions; for example, the characters of Mrs. Frisby and the Rats of NIMH, the television series Ratz, Rizzo the Rat from The Muppets and Terry Pratchett's The Amazing Maurice and his Educated Rodents.
- Rats also appear in numerous video and computer games as killable monsters. In many of these games, rats appear much larger than normal. Examples of games where rats and giant rats are found as monsters include Baldur's Gate (I and II) and Everquest. In these games rats are the lowest form of threat faced by new characters and are used as a form of combat training.
- Splinter of Teenage Mutant Ninja Turtles fame is a mutated rat.
- Templeton of E. B. White's children's book, Charlotte's Web, is a Brown rat, devoid of morals, that lives on the farm, underneath Wilbur's food trough.
- A media frenzy developed in New York City 23 Feb. 2007, when a dozen rats invaded a Taco Bell, and ran unimpeded.
- A Transformers character called Rattrap can transform into a rat.
- Malevolent rats in H. P. Lovecraft's short story " The Rats in the Walls"
- In DreamWorks and Aardman Animations' 2006 film, Flushed Away, a pet rat is flushed down the toilet into a city in the London sewer populated by other rats.
- Disney's Pixar release, Ratatouille, features a rat named Remy seeking to become a fine chef.
- In the 1971 film Willard and the 2003 remake Willard (2003 film).
- In Peanuts, Charlie Brown's favorite utterance is "Rats!", shouted after suffering yet another personal reversal.
- Spike aired Gary the Rat, an animated series revolving around a debauched attorney named Gary Andrews who mysteriously transforms into an anthropomorphic gray rat.
- In early episodes of South Park, Kenny McCormick's corpse was frequently gnawed upon and dragged away by rats after he died.
- In the TV series House, House has a pet rat named Steve McQueen that he caught at his ex-girlfriend, Stacy Warner's home. He's first seen in the episode, Hunting, and later appears in Euphoria, Part 2.
- In the Belgian comics book Le Bal du rat mort , which means the ball of the dead rat, police inspector Jean Lamorgue is like a pied piper who has to deliver the city of Ostend of thousands of invading rats who attack people and kill them, but in the end he fails because he is possessed by his own demons.
- In the Deltora Quest series there is a city called Hira, nicknamed the "City of Rats" because its rat population grew so much that it's people were forced to flee. These rats were used by the villains to feed a giant snake monster that took control of the city.
- In the Harry Potter books, a character named Peter Pettigrew can transform at will into a rat, for which he is nicknamed Wormtail.
- In the Disney movie Lady and the Tramp, a rat craws into the baby`s room, and Tramp runs into the house to save the child. The rat also squeaks in pain when Tramp bites him, like a real rat does when hurt.
- In Thomas Pynchon's novel V., a female rat named Veronica is introduced in chapter five as part of a sub-plot in which Father Linus Fairing lives in the sewers and preaches to a congregation of rats.
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
- Genus Rattus
- Rattus adustus
- Rattus annandalei
- Rattus argentiventer
- Rattus baluensis
- Rattus bontanus
- Rattus boulos
- Rattus burrus
- Rattus colletti
- Rattus elaphinus
- Rattus enganus
- Rattus everetti
- Rattus exulans
- Rattus feliceus
- Rattus foramineus
- Rattus fuscipes
- Rattus giluwensis
- Rattus hainaldi
- Rattus hoffmani
- Rattus hoogerwerfi
- Rattus jobiensis
- Rattus koopmani
- Rattus korinchi
- Rattus leucopus
- Rattus losea
- Rattus lugens
- Rattus lutreolus
- Rattus macleari
- Rattus marmosurus
- Rattus mindorensis
- Rattus mollicomulus
- Rattus montanus
- Rattus mordax
- Rattus morotaiensis
- Rattus nativitatis
- Rattus nitidus
- Rattus norvegicus
- Rattus novaeguineae
- Rattus osgoodi
- Rattus palmarum
- Rattus pelurus
- Rattus praetor
- Rattus ranjiniae
- Rattus rattus
- Rattus sanila
- Rattus sikkimensis
- Rattus simalurensis
- Rattus sordidus
- Rattus steini
- Rattus stoicus
- Rattus tanezumi
- Rattus tawitawiensis
- Rattus timorensis
- Rattus tiomanicus
- Rattus tunneyi
- Rattus turkestanicus
- Rattus villosissimus
- Rattus xanthurus