Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "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, ''Rattus norvegicus''. Many members of other rodent genera and families are also referred to as rats, and share many characteristics with true rats.
Rats are typically distinguished from mice by their size; rats are generally large muroid rodents, while mice are generally small muroid rodents. The muroid family is very large and complex, and the common terms ''rat'' and ''mouse'' are not taxonomically specific. Generally, when someone discovers a large muroid, its common name includes the term ''rat'', while if it is small, the name includes the term ''mouse''. Scientifically, the terms are not confined to members of the ''Rattus'' and ''Mus'' genera, for example, the pack rat and cotton mouse.
Species and description
The best-known rat
species are the
Black Rat (''Rattus rattus'') and the
Brown Rat (''Rattus 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 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''. Male rats are called ''bucks'', unmated females are called ''does'', pregnant or parent females are called ''dams'', and infants are called ''kittens'' or ''pups''. A group of rats is either referred to as a ''pack'' or a ''mischief''.
The common species are opportunistic survivors and often live with and near humans; therefore they are known as commensals. They may cause substantial food losses, especially in developing countries. However, 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.
Wild rodents, including rats, can carry many different zoonotic pathogens, such as Leptospira, Toxoplasma gondii, and Campylobacter. The Black Death is traditionally believed to have been caused by the micro-organism ''Yersinia pestis'', carried by the Tropical Rat Flea (''Xenopsylla cheopis'') which preyed on Black Rats living in European cities during the epidemic outbreaks of the Middle Ages; these rats were used as transport hosts. Other zoonotic diseases linked to pest rodents include Classical swine fever and Foot-and-mouth disease.
The average lifespan of any given rat depends on which species is being discussed, but many only live about a year due to predation.
As pets
Specially bred rats have been kept as pets at least since the late 19th century. Pet rats are typically variants of the species
brown rat, but
black rats and
giant pouched rats are also known to be kept. Pet rats behave differently than their wild counterparts depending on how many generations they have been kept as pets. Pet rats do not pose any more of a
health risk than pets such as
cats or
dogs. Tamed rats are generally friendly and can be taught to perform selected behaviors.
As subjects of scientific research
In 1895,
Clark University in
Worcester,
Massachusetts (
United States) established a population of domestic albino 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), as well as to understand
group behavior and overcrowding (with the work of
John B. Calhoun on
behavioral sink). A 2007 study found rats to possess
metacognition, a mental ability previously only documented in humans and some primates.
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 as model organisms for scientific research. Since the publication of the Rat Genome Sequence, and other advances such as the creation of a rat SNP chip, and the production of knockout rats, the laboratory rat has become a useful genetic tool, although not as popular as 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.
As food
Rat meat is a food that, while
taboo or even forbidden in some cultures, is a dietary staple in others. Taboos include fears of disease or religious prohibition, but in many places the high number of rats has led to their incorporation into the local diet.
In some cultures, rats are or have been limited as an acceptable form of food to a particular social or economic class. In the Mishmi culture of India, rats are essential to the traditional diet, as Mishmi women may eat no meat except fish, pork, wild birds and rats. Conversely, the Musahar community in north India has commercialised rat farming as an exotic delicacy. In the traditional cultures of the Hawaiians and the Polynesians, rat was an everyday food for commoners. When feasting, the Polynesian people of Rapa Nui could eat rat meat, but the king was not allowed to, due to the islanders' belief in his "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.
Bandicoot rats are an important food source among some peoples in Southeast Asia, and 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.
African slaves in the American South were known to hunt wood rats (among other animals) to supplement their food rations, and Aborigines along the coast in Southern Queensland, Australia regularly included rats in their diet.
Ricefield rats ''(Rattus argentiventer)'' have traditionally been used as food in rice-producing regions like Valencia, as immortalized by Vicente Blasco Ibáñez in his novel ''Cañas y barro''. Along with eel and local beans known as "''garrafons''", ''rata de marjal'' is one of the main ingredients in traditional paella (later replaced by rabbit, chicken and seafood). Ricefield rats are also consumed in the Philippines, the Isaan region of Thailand, as well as Cambodia. In late 2008, Reuters reported that the price of rat meat had quadrupled in Cambodia creating a hardship for the poor who could no longer afford it. Cambodia exports about a metric ton of rats daily to Vietnam as food.
Elsewhere in the world, rat meat is considered diseased and unclean, socially unacceptable, or there are strong religious proscriptions against it. Islam and Kashrut traditions prohibit it, while 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. Captive-bred ball pythons in particular, are fed a diet of mostly rats. Rats, as food items, are available from many suppliers who supply to individual snake owners as well as to large reptile zoos. In Britain the government in 2007 ruled out the feeding of any live mammal to another animal. The rule says the animal must be dead (frozen) then given to the animal to eat. The rule was put in to place mainly because of the pressure of the RSPCA and people who found it cruel.
In medicine
Rats can serve as
zoonotic vectors for certain pathogens and thus cause disease, such as
Lassa fever and
Hantavirus. ''Rattus rattus'', and the rat flea
Xenopsylla cheopis, are notorious for their role in epidemics of
bubonic plague.
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 (a dependency of the British Crown) there is a taboo against the word "rat." See ''Longtail (rat)'' for more information.
In Asian cultures
In Indian tradition rats are seen as the vehicle of
Ganesha 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 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, intelligence, 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 European cultures
European associations with the rat are generally negative. For instance, "Rats!" is used as a substitute for various vulgar
interjections in the English language. 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 some people in European cultures keep
rats as pets and conversely find them to be tame, clean, intelligent, and playful.
Rats are often used in scientific experiments; 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).
''Rat'' in terminology
Rats are frequently blamed for damaging food supplies and other goods, or spreading disease. Their reputation has carried into common parlance: in the
English language, ''rat'' is often an insult. ''Rat'' is generally used to signify an unscrupulous character. Writer/Director
Preston Sturges created the humorous alias "Ratskywatsky" for a soldier who seduced, impregnated, and abandoned the heroine of his
1944 film, ''
The Miracle of Morgan's Creek''. It is a term (
noun and
verb) in criminal slang for an
informant - "to rat on someone" is to betray them by informing the authorities of a
crime or misdeed they committed. Describing a person as "rat-like" usually implies he or she is unattractive and suspicious.
Among unions, "rat" is a term for non-union employers or breakers of union contracts, and this is why unions use inflatable rats.
In Judaism
In Leviticus 11:29, rats are prohibited as food. (See 'as food' above.)
In fiction
Depictions of rats in fiction are historically inaccurate and negative. The most common falsehood is the squeaking almost always heard in otherwise realistic portrayals (i.e. non-
anthropomorphic). While the recordings may be of actual squeaking rats, the noise is uncommon - they may do so only if distressed, hurt, or annoyed. Normal vocalizations are very high-pitched, well outside the range of human hearing. Rats are also often cast in vicious and aggressive roles when in fact it is their shyness which helps keep them undiscovered for so long in an infested home.
The actual portrayals of rats vary from negative to positive with a majority in the negative and ambiguous. The rat plays a villain in several mouse societies; from Brian Jacques's ''Redwall'' and Robin Jarvis's ''The Deptford Mice'', to the roles of Disney's Professor Ratigan and Kate DiCamillo's Roscuro and Botticelli. They have often been used as a mechanism in horror; being the titular evil in stories like ''The Rats'' or H.P. Lovecraft's ''The Rats in the Walls'' and in films like ''Willard'' and ''Ben''. Another terrifying use of rats is as a method of torture, for instance in Room 101 in George Orwell's ''Nineteen Eighty-Four'' or ''The Pit and the Pendulum'' by Edgar Allan Poe.
Selfish helpfulness —those willing to help for a price— has also been attributed to fictional rats. Templeton, from E. B. White's ''Charlotte's Web'', repeatedly reminds the other characters that he is only involved because it means more food for him, and the cellar-rat of John Masefield's ''The Midnight Folk'' requires bribery to be of any assistance.
By contrast, the rats appearing in the Doctor Dolittle books tend to be highly positive and likeable characters, many of whom tell their remarkable life stories in the Mouse and Rat Club established by the animal-loving doctor.
Some fictional works use rats as the main characters. Notable examples include the society created by O'Brien's ''Mrs. Frisby and the Rats of NIMH'', ''Doctor Rat'', Rizzo the Rat from The Muppets, and animated films like Pixar's ''Ratatouille''. ''Mon oncle d'Amérique'' ("''My American Uncle''"), a 1980 French film, illustrates Henri Laborit's theories on evolutionary psychology and human behaviors by using short sequences in the storyline showing lab rat experiments.
In Harry Turtledove's science fiction novel ''Homeward Bound'', humans unintentionally introduce rats to the ecology at the home world of an alien race which previously invaded Earth and introduced some of its own fauna into its environment. And A. Bertram Chandler pitted his space-bound protagonist, Commodore Grimes, against giant intelligent rats who took over several stellar systems and enslaved their human inhabitants. "The Stainless Steel Rat" is nickname of the (human) protagonist of a series of humorous science fiction novels written by Harry Harrison
The Pied Piper
One of the oldest and most historic stories about rats is ''
The Pied Piper of Hamelin'', in which a rat-catcher leads away an infestation with enchanted music—the piper is later refused payment, so he in turn leads away the town's children. This tale, placed in Germany around the late 13th century, has inspired the realms of film, theatre, literature, and even opera. The subject of much research, some theories have intertwined the tale with events related to the
Black Plague, in which
black rats may have played an important role. Fictional works based on the tale that focus heavily on the rat aspect include Pratchett's ''
The Amazing Maurice and his Educated Rodents'', and Belgian graphic novel ''
Le Bal du Rat Mort'' (''The Ball of the Dead Rat'').
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 64 extant species. A subgeneric breakdown of the species has been proposed, but does not include all species.
Species of rats
See also
Black rat
Brown rat
List of fictional mice and rats
Mouse
Oriental rat flea
Rat (zodiac)
Rat-baiting
Rat-catcher
Working rat
''Rattus Norvegicus'', a punk-rock album by the band The Stranglers which uses the Latin name for "Brown Rat".
East Timor giant rat
References and notes
Further reading
Barnett, S. Anthony (2002) ''The Story of Rats: Their Impact on Us, and Our Impact on Them'', Allen & Unwin, Crows Nest, NSW, 202 pages, ISBN 1-86508-519-7.
Hendrickson, R. (1983) ''More Cunning than Man: A Complete History of the Rat and its Role in Civilization'', Kensington Books. ISBN 1-57566-393-7.
Jahn, G. C., P. Cox, S. Mak, and N. Chhorn (1999) "Farmer participatory research on rat management in Cambodia", In G. Singleton, L. Hinds, H. Leirs and Zhibin Zhang [Eds.] ''Ecologically-based rodent management'' ACIAR, Canberra. Ch. 17, pp. 358–371. ISBN 1863202625.
Matthews, I. (1898). ''Full Revelations of a Professional Rat-Catcher, after 25 Years’ Experience''. 1st ed. Manchester: Friendly Societies Printing Co. ISBN 1-905124-64-3.
Musser, G. G. and M. D. Carleton. 1993. "Family Muridae" in D. E. Wilson and D. M. Reeder eds. "Mammal Species of the World a Taxonomic and Geographic Reference", Smithsonian Institution Press, Washington, D.C. pp. 501–755.
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.
Sullivan, Robert (2005). ''Rats: Observations on the History and Habitat of the City's Most Unwanted Inhabitants''. Bloomsbury USA. ISBN 1-58234-477-9.
External links
High-Resolution Images of the Rat Brain
National Bio Resource Project for the Rat in Japan
Rat Behaviour and Biology
Rat Genome Database
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Category:Scavengers
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