Difference between revisions of "Rat" - New World Encyclopedia

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{{Taxobox
 
{{Taxobox
 
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| color = pink
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| image = Rattus rattus05.jpg
 
| image = Rattus rattus05.jpg
 
| image_width = 200px
 
| image_width = 200px
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| image_caption = [[Black Rat]] (''Rattus rattus'')
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| image_caption = Black Rat ''(Rattus rattus)''
 
| regnum = [[Animal]]ia
 
| regnum = [[Animal]]ia
 
| phylum = [[Chordata]]
 
| phylum = [[Chordata]]
 
| classis = [[Mammal]]ia
 
| classis = [[Mammal]]ia
 
| ordo = [[Rodent]]ia
 
| ordo = [[Rodent]]ia
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| superfamilia = [[Muroidea]]*
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| superfamilia = Muroidea
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| familia = [[Muridae]]
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| familia = Muridae
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| subfamilia = [[Murinae]]
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| subfamilia = Murinae
 
| genus = '''''Rattus'''''
 
| genus = '''''Rattus'''''
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| genus_authority = [[Johann Fischer von Waldheim|Fischer de Waldheim]], 1803
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| genus_authority = Fischer de Waldheim, 1803
 
| subdivision_ranks = [[Species]]
 
| subdivision_ranks = [[Species]]
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| subdivision = 50 species; see text<br/>
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| subdivision = 50 to 78 species<br/>
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<nowiki>*</nowiki>Several subfamilies of Muroids<br/>include animals called rats.
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Several families of rodents<br/>include animals called rats.
 
}}
 
}}
  
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'''Rats''' are various medium sized [[rodent]]s. "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. Most rats are [[omnivore]]s, eating both [[plant]] and [[animal]] foods, and generalists, not bound to one specialized way of life.
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'''Rats''' are various medium sized [[rodent]]s, similar in appearance to [[mouse|mice]], but larger. "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.'' This genus is part of the family Muridae (Old World rats and mice). However, many members of other rodent genera and families are also called rats and share many characteristics with true rats. Rodents referred to as both rats and mice can be found in the families Cricetidae, Nesomyidae, Spalacidae, and Muridae.
  
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Rats are distinguished from [[mice]] by their size; rats generally have bodies longer than 12 cm (5 inches). Most [[squirrel]]s are about the same size as rats but are members of their own family, Sciuridae, and are most often more specialized.
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Although often regarded as agricultural pests, general pests, and vectors of [[disease]]&mdash;indeed, rats have spread serious diseases, consumed substantial amounts of food crops, gnawed electrical wires, and so forth&mdash;rats in general play important roles in laboratory research, ecological [[food chain]]s, and as pets. Due to an incredible adaptability to almost any environment and a general ability to live [[symbiosis|symbiotically]] with humans, rats are regarded to be the most successful [[mammal]]ian species living on earth today, followed by the [[mouse]]. Part of the difficulty is that some rat species, notably the black rat, have been spread by humans as [[invasive species]] into non-native habitats.
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==General rat characteristics==
 
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==The genus ''Rattus''==
 
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==Rats as pests==
 
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==Domesticated rats==
 
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==The Rat==
 
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The best-known rat species are the [[Black Rat]] ''Rattus rattus'' and the [[Brown Rat]] ''R. norvegicus''. There is also one type of rat called ''Tars'', usually found on [[Mount Everest]]. 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 [[mouse|mice]], but seldom weigh over 500 [[gram]]s (1 [[Pound (mass)|lb]]) in the wild.  The common term "rat" is also used in the names of other small [[mammal]]s which are not true rats. Examples include the [[North America]]n [[pack rat]]s, a number of species loosely called [[kangaroo rat]]s, 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 [[Endemic (ecology)|island endemic]]s and some have become endangered due to habitat loss or competition with [[brown rat|brown]], [[Black Rat|black]], or [[Polynesian Rat|Polynesian]] rats.
 
  
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In [[Western countries]], many people keep domesticated rats as [[pet]]s. 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 rat]]s", 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.
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In the broadest use of the terms rat and mouse, going beyond the specific genera ''Rattus'' and ''Mus,'' the main distinction between these two groups is a matter of size. Rats generally have bodies longer than 12 cm (five inches), and mice are similar looking animals that are perhaps 12 cm or less in size. [[Squirrel]]s of most species are about the same size as rats but are members of their own rodent family, ''Sciuridae,'' and are usually more specialized than rats.  
  
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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 [[parasite]]s and mites, but do not generally spread disease to humans.
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As rodents, both rats and mice are characterized by dentition specialized for gnawing, including a single pair of upper incisors, a single pair of lower incisors, and a gap followed by one or more molars, as well as no canine teeth and nor more than one incisor in each quadrant (Myers 2000).  
  
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Rats have a normal lifespan ranging from two to five years, though three years is typical.
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==General rat characteristics==
  
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==Laughter in rats== 
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Like most smaller rodents, true rats and most other rats mature rapidly and only live for a short time. The black rat reaches sexual maturity in 80 days; its longest recorded life was four years and two months (Nowak 1986). Most rat species breed several times each year and have multiple offspring. This lets their populations rapidly expand to take advantage of changes in their environments and also replaces individuals lost to predators.
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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 respond 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. [http://www.psych.umn.edu/courses/fall06/macdonalda/psy4960/Readings/PankseppRatLaugh_P&B03.pdf 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. [http://www.sciencenews.org/articles/20010728/fob9.asp Science News 2001]
 
  
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== Rats in culture ==
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Most rats are [[omnivore]]s, eating both [[plant]] and [[animal]] foods, and generalists, not bound to one specialized way of life. Among the exceptions to this are the mole rats of [[Africa]] (Bathyergidae family), especially the naked mole rat ''(Heterocephalus glaber),'' which are highly specialized and live almost their entire lives underground eating [[bulb]]s, [[root]]s, and [[tuber]]s. The fish-eating rats of [[South America]] ''(Ichthyomys species)'' swim in streams to catch small [[fish]]. Kangaroo rats of [[North America]] ''(Dipodomys species)'' live in [[desert]] environments and do not need to drink; they get the water they need from the seeds and [[insect]]s they eat. The marmoset rat of southeast [[Asia]] ''(Hapalomys longicaudatus)'' feeds mainly on [[bamboo]] and builds its nests in the bamboo stems (Nowak 1986).
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[[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).
 
  
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On the [[Isle of Man]] (British Protectorate) there is a [[taboo]] against the word "rat."  See [[longtail]] for more information.
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Among the largest rat species are the [[muskrat]] of North America ''(Ondatra zibethicus)'', which weighs 700 to 1800 grams (1.5 to 4 lbs) and the giant tree rat of [[New Guinea]] ''(Mallomys rothschildi).'' which can weigh as much as 2000 grams (4.4 lbs) (Nowak 1986).
  
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=== Eastern cultures ===
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Rats typically have a four or five fingered hand, whiskers which serve as [[sense]] organs, and a long tail, which in most species is hairless. Like all rodents they have two incisors on the upper and on the lower jaw, which grow throughout the animal's life and must be ground down by gnawing. (The word rodent comes from the Latin word for gnawing.)
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[[Image:Netsukerat.jpg|left|thumb|A [[Netsuke]] of a rat from Japan.]]
 
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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."
 
  
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==The genus ''Rattus''==
  
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[[Image:Rat temple.jpg|thumb|right|The indigenous rats are allowed to run freely throughout the [[Karni Mata]] temple.]]
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The genus ''Rattus,'' true rats, is one of the largest genera of [[mammal]]s and includes as many as 78 species (Nowak 1986). True rats are native to southeast [[Asia]], [[Australia]], and the nearby islands. Some species build nests in trees, while others burrow into the ground. Most live in groups ranging from a few individuals to one hundred or more. Rats fight to establish dominance within the group, but rarely kill or injure each other. Sometimes females within a group will nurse each other's young (Barnett 2001).  
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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.
 
  
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=== Western cultures ===
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True rats are opportunistic feeders, eating [[seed]]s, [[fruit]], [[vegetable]]s, [[insect]]s, other small animals. Most true rats live in forests or near rivers or other bodies of water. In Australia, some species live in [[grassland]]s and desert environments.
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[[Western civilization|Western]] associations with the rat are generally negative. For instance, "Rats!" is used as a substitute for various vulgar [[interjection]]s. 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 [[Fancy rat|rats as pets]] and conversely find them to be tame, clean, intelligent, and playful. While undomesticated rats, dogs, and cats may all be [[pest (animal)|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.
 
  
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Describing a person as "rat-like" usually implies he is unattractive and suspicious.  In contrast, mice are stereotyped as cute and [[bourgeoisie|bourgeois]].
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==Rats as pests==
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[[Image:Rattus norvegicus 1.jpg|thumb|Brown Rat, ''Rattus norvegicus'']]
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Rat is also a term ([[noun]] and [[verb]]) in criminal (often [[Mafia]]) slang for a [[Informant|criminal informant]].
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Some [[species]] of rats, both true rats and rats of other genera, have become very successful by taking advantage of human activities. The black rat, ''Rattus rattus,'' which is naturally a tree dwelling species, has found nesting places and food in barns, houses, and other buildings and spread around the world with the the unwitting help of humans. The black rat was common in [[Europe]] by the time of the [[Roman Empire]]. It is also known as the roof rat and the ship rat.
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Rats are often used in scientific [[experiment]]s; 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.
 
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=== Rats in pop culture ===
 
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Mutant, man-eating rats are the monsters in [[James Herbert]]'s [[Horror fiction|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 (television series)|Ratz]]'', [[Rizzo the Rat]] from [[The Muppets]] and [[Terry Pratchett]]'s ''[[The Amazing Maurice and his Educated Rodents]]''.<ref>[http://www.hamiltonparanormal.com/rattery/hollywood.html Hollywood Rats]</ref> Rats also appear in numerous video and computer games as killable monsters. In many of these games, rats appear much larger than normal.
 
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== Rats as vermin ==
 
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[[Image:Rattus norvegicus 1.jpg|left|thumb|150px|[[Brown Rat]] (''Rattus norvegicus'')]]
 
  
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By most standards, rats are considered [[Pest (animal)|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[http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3441?opendocument]; it is even illegal to keep pet rats there.
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The brown rat, ''R. norvegicus,'' also known as the Norway rat and the sewer rat, is a ground dweller and naturally digs its burrows near water. It gradually spread out of [[Asia]] and reached [[Europe]] in the 1700s and North and South America soon after. Brown rats mostly live low to the ground, sometimes in city sewers. In some buildings, brown rats live in the basement and black rats in the attic (Barnett 2001).  
  
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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.[http://www.austinchronicle.com/gyrobase/Issue/story?oid=oid%3A75571]
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Other rat species that have come to live in close association with humans include the rice field rat ''(Rattus argentiventer)'' of southeast Asia; the Polynesian rat ''(R. exulans),'' native to southeast Asia and spread to the Pacific islands along with humans; the banicoot rats of [[India]] and Southeast Asia (''Bandicota bengalensis,'' ''B. indica,'' and ''B. savilei''); and the pest rat ''(Nesokia indica),'' which is found from [[Egypt]] to [[China]] (Nowak 1986).
  
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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]].
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These ''[[symbiosis|commensal]]'' (which means "sharing the same table") rat species do a tremendous amount of damage to human interests, mainly by eating crops and stored food and by spreading [[disease]]s. It is estimated that rats and mice consume one fifth of the food crops that humans grow each year, including 50 million tons of [[rice]] (Voelker 1986).
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[[Image:Jack Black.jpg|left|thumb|English ratcatcher, 1851]]
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Rats can carry over thirty different diseases dangerous to humans, including Weil's disease, [[typhus]], [[salmonella]], and [[bubonic plague]]. Bubonic plague is caused by the [[bacteria]] ''Yersinia pestis'' and spread through the bite of the [[flea]] ''Xenopsylla cheopis.'' The plague bacteria and the fleas are common on wild rodents and often seem to do them no harm. When the disease spreads to commensal rats, especially the black rat, humans can be infected. In the [[Middle Ages]] plague outbreaks were common in European cities and sometimes killed 25 percent or more of an area's population. In the early twentieth century, plague killed around a million people a year in [[India]] and continues to be a problem today (Barnett 2001).
  
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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 [[cat]]s and [[dogs]] have also been employed to hunt rats.  Professional [[rat-catchers]] can be found in many [[developing countries]].
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Other damage caused by rats includes damaging dams and irrigation works by burrowing, causing power outages and fires by gnawing electric wires, contaminating food, damaging furniture and many other things. About 14,000 Americans are bitten by rats every year (Voelker 1986).
  
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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. [http://www.austinchronicle.com/issues/dispatch/2000-01-21/xtra_feature.html] It is typically at this point that vermin control measures tend to increase.{{Clr}}
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Rats have also caused a lot of damage to natural environments to which they have been introduced. The black rat, which was introduced to many remote islands by early sailing ships, is listed as one of the world's 100 worst invasive species by the Invasive Species Specialist Group (ISSG 2007).
  
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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.[http://www.powells.com/biblio?isbn=1582343853]
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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 poison and traps. [[Cat]]s, [[dog]]s. [[ferret]]s, and even [[snake]]s have also been employed to hunt rats. Professional rat-catchers can be found in many developing countries and rat control is a big business world-wide.
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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.
 
  
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==Domestic rats and rats as food==
 
[[Image:MorrisWaterMaze.jpg|thumb|Laboratory rat in water maze experiment]]
 
[[Image:MorrisWaterMaze.jpg|thumb|Laboratory rat in water maze experiment]]
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==References and notes==
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[[Image:Cloudtherat1.jpg|thumb|Pet domestic brown rat.]]
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<references/>
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[[Image:Cricetomys emini.jpg|thumb|Pet pouched rat, ''Cricetomys emini'']]
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==See also==
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The domestication of rats started in [[England]] with the sport of rat-baiting, in which rats (mostly brown rats) were put into a pit and killed by dogs. Captive rats were bred to provide a constant supply of contenders. From time to time, a white or spotted rat would be born due to genetic [[mutation]]. These were bred with each other; changing their gene pool, allowing them to become popular as [[pet]]s.
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*[[Fancy rat]], Pet rats
 
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*[[Rat-baiting]]
 
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*[[Rat-catcher]]
 
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*[[Rat Park]]
 
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*[[Rat (zodiac)]]
 
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*[[List of fictional mice and rats]]
 
  
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==Taxonomy of ''Rattus''==
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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]], [[disease]]s, 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 2001).
  
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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]]''.
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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 [[brain]]s, [[liver]]s, [[kidney]]s, [[adrenal gland]]s, and [[heart]]s are smaller (Barnett 2001).
  
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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:
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Domestic rat young and adults are sometimes used as food for captive reptiles. Rats, like all mammals, are edible by humans and are sometimes captured and eaten in emergency situations. 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 [[Islam|Islamic]] and [[Judaism|Jewish]] dietary laws, the prohibition of all meat in [[Hinduism]], and the rat's bad reputation in many cultures, especially as a carrier of disease.
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*''norvegicus'' group
 
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*''rattus'' group
 
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*Australian native rat species
 
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*New Guinea native rat species
 
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*''xanthurus'' group
 
  
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The following list is alphabetical.
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Pet rats, also called "fancy rats" (from the expression "rat fancy," not because the rats themselves are fancy in appearance), continue to be very popular. They are inexpensive, fairly easy to care for, active, intelligent, and can be friendly with humans. Among the other rat species sometimes kept as pets are the wood rats or pack rats of North America ''(Neotoma species),'' the giant pouched rat of Africa ''(Cricetomys emini),'' and the white-tailed rat of Africa ''(Mystromys albicaudatus)'' (Nowak 1986).
  
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===Species of rats===
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==References==
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*Genus ''Rattus''
 
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**''[[Rattus adustus]]''
 
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**''[[Rattus annandalei]]''
 
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**''[[Rattus argentiventer]]''
 
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**''[[Rattus baluensis]]''
 
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**''[[Rattus bontanus]]''
 
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**''[[Rattus burrus]]''
 
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**''[[Rattus colletti]]''
 
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**''[[Rattus elaphinus]]''
 
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**''[[Rattus enganus]]''
 
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**''[[Rattus everetti]]''
 
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**''[[Rattus exulans]]''
 
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**''[[Rattus feliceus]]''
 
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**''[[Rattus foramineus]]''
 
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**''[[Rattus fuscipes]]''
 
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**''[[Rattus giluwensis]]''
 
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**''[[Rattus hainaldi]]''
 
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**''[[Rattus hoffmani]]''
 
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**''[[Rattus hoogerwerfi]]''
 
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**''[[Rattus jobiensis]]''
 
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**''[[Rattus koopmani]]''
 
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**''[[Rattus korinchi]]''
 
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**''[[Rattus leucopus]]''
 
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**''[[Rattus losea]]''
 
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**''[[Rattus lugens]]''
 
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**''[[Rattus lutreolus]]''
 
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**''[[Rattus macleari]]''
 
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**''[[Rattus marmosurus]]''
 
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**''[[Rattus mindorensis]]''
 
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**''[[Rattus mollicomulus]]''
 
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**''[[Rattus montanus]]''
 
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**''[[Rattus mordax]]''
 
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**''[[Rattus morotaiensis]]''
 
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**''[[Rattus nativitatis]]''
 
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**''[[Rattus nitidus]]''
 
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**''[[Rattus norvegicus]]''
 
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**''[[Rattus novaeguineae]]''
 
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**''[[Rattus osgoodi]]''
 
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**''[[Rattus palmarum]]''
 
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**''[[Rattus pelurus]]''
 
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**''[[Rattus praetor]]''
 
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**''[[Rattus ranjiniae]]''
 
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**''[[Rattus rattus]]''
 
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**''[[Rattus sanila]]''
 
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**''[[Rattus sikkimensis]]''
 
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**''[[Rattus simalurensis]]''
 
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**''[[Rattus sordidus]]''
 
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**''[[Rattus steini]]''
 
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**''[[Rattus stoicus]]''
 
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**''[[Rattus tanezumi]]''
 
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**''[[Rattus tawitawiensis]]''
 
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**''[[Rattus timorensis]]''
 
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**''[[Rattus tiomanicus]]''
 
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**''[[Rattus tunneyi]]''
 
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**''[[Rattus turkestanicus]]''
 
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**''[[Rattus villosissimus]]''
 
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**''[[Rattus xanthurus]]''
 
  
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== Further reading and references ==
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* Barnett, S. A. 2001. ''The Story of Rats: Their Impact on Us, and Our Impact on Them.''  Crows Nest, NSW, Australia : Allen & Unwin. ISBN 1865085197
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*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 .  
+
* Charles Darwin Research Foundation [http://www.darwinfoundation.org/files/species/pdf/rats-en.pdf.] Eradication of Invasive species Black rats. Retrieved October 10, 2007.
 +
* Invasive Species Specialist Group (ISSG). 2007. [http://www.issg.org/database/species/ecology.asp?si=19&fr=1&sts= Global invasive species database: ''Rattus rattus''] ''Invasive Species Specialist Group Website'' Retrieved March 19, 2007.
 +
* Myers, P. 2000. [http://animaldiversity.ummz.umich.edu/site/accounts/information/Rodentia.html Order Rodentia (rodents)]. Animal Diversity Web. Retrieved January 30, 2007.
 +
* Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. [[http://animaldiversity.ummz.umich.edu/site/accounts/classification/Muroidea.html Superfamily Muroidea (mice, rats, gerbils, and relatives]. ''The Animal Diversity Web'' (online). Retrieved January 30, 2007 at http://animaldiversity.org.
 +
* Nowak, R. M. 1999. ''Walker's Mammals of the World,'' 6th edition. Johns Hopkins University Press. ISBN 0801857899
 +
* Nowak, R. M., and J. L. Paradiso. 1983. ''Walker's Mammals of the World.'' Baltimore, Maryland: The Johns Hopkins University Press. ISBN 0801825253
 +
* Voelker, W. 1986. ''The Natural History of Living Mammals.'' Medford, New Jersey: Plexus Publishing, Inc. ISBN 0937548081
  
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*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.
 
  
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*Matthews, I. (1898) 1st ed. [http://www.gutenberg.org/files/17243/17243-h/17243-h.htm#startoftext Full Revelations of a Professional Rat-Catcher, after 25 Years’ Experience.] Manchester: Friendly Societies Printing Co. ISBN 1-905124-64-3
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{{credit|104753593}}
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*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.
 
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*Nowak, R. M. 1999. Walker's [[Mammal]]s of the World, Vol. 2. Johns Hopkins University Press, London.
 
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*Sullivan, Robert. 2004. Rats - A Year with [[New York]]´s Most Unwanted Inhabitants. Granta Books, London.
 
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*Sullivan, Robert. 2005. Rats: Observations on the History and Habitat of the City's Most Unwanted Inhabitants. Bloomsbury USA. ISBN 1-58234-477-9
 
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==External links==
 
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*[http://www.ratbehavior.org/rats.html Rat Behaviour and Biology]
 
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*[http://www.anim.med.kyoto-u.ac.jp/nbr/home.htm National Bio Resource Project for the Rat in Japan]
 
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*[http://rgd.mcw.edu/ Rat Genome Database]
 
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*[http://brainmaps.org/index.php?p=speciesdata&species=rattus-norvegicus High-Resolution Images of the Rat Brain]
 
  
 
[[Category:Life sciences]]
 
[[Category:Life sciences]]
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{{credit|104753593}}
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[[Category:Animals]]
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[[Category:Mammals]]

Latest revision as of 06:43, 17 July 2022

Rats
Fossil range: Early Pleistocene - Recent
Black Rat (Rattus rattus)
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 to 78 species
Several families of rodents
include animals called rats.

Rats are various medium sized rodents, similar in appearance to mice, but larger. "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. This genus is part of the family Muridae (Old World rats and mice). However, many members of other rodent genera and families are also called rats and share many characteristics with true rats. Rodents referred to as both rats and mice can be found in the families Cricetidae, Nesomyidae, Spalacidae, and Muridae.

Although often regarded as agricultural pests, general pests, and vectors of disease—indeed, rats have spread serious diseases, consumed substantial amounts of food crops, gnawed electrical wires, and so forth—rats in general play important roles in laboratory research, ecological food chains, and as pets. Due to an incredible adaptability to almost any environment and a general ability to live symbiotically with humans, rats are regarded to be the most successful mammalian species living on earth today, followed by the mouse. Part of the difficulty is that some rat species, notably the black rat, have been spread by humans as invasive species into non-native habitats.

In the broadest use of the terms rat and mouse, going beyond the specific genera Rattus and Mus, the main distinction between these two groups is a matter of size. Rats generally have bodies longer than 12 cm (five inches), and mice are similar looking animals that are perhaps 12 cm or less in size. Squirrels of most species are about the same size as rats but are members of their own rodent family, Sciuridae, and are usually more specialized than rats.

As rodents, both rats and mice are characterized by dentition specialized for gnawing, including a single pair of upper incisors, a single pair of lower incisors, and a gap followed by one or more molars, as well as no canine teeth and nor more than one incisor in each quadrant (Myers 2000).

General rat characteristics

Like most smaller rodents, true rats and most other rats mature rapidly and only live for a short time. The black rat reaches sexual maturity in 80 days; its longest recorded life was four years and two months (Nowak 1986). Most rat species breed several times each year and have multiple offspring. This lets their populations rapidly expand to take advantage of changes in their environments and also replaces individuals lost to predators.

Most rats are omnivores, eating both plant and animal foods, and generalists, not bound to one specialized way of life. Among the exceptions to this are the mole rats of Africa (Bathyergidae family), especially the naked mole rat (Heterocephalus glaber), which are highly specialized and live almost their entire lives underground eating bulbs, roots, and tubers. The fish-eating rats of South America (Ichthyomys species) swim in streams to catch small fish. Kangaroo rats of North America (Dipodomys species) live in desert environments and do not need to drink; they get the water they need from the seeds and insects they eat. The marmoset rat of southeast Asia (Hapalomys longicaudatus) feeds mainly on bamboo and builds its nests in the bamboo stems (Nowak 1986).

Among the largest rat species are the muskrat of North America (Ondatra zibethicus), which weighs 700 to 1800 grams (1.5 to 4 lbs) and the giant tree rat of New Guinea (Mallomys rothschildi). which can weigh as much as 2000 grams (4.4 lbs) (Nowak 1986).

Rats typically have a four or five fingered hand, whiskers which serve as sense organs, and a long tail, which in most species is hairless. Like all rodents they have two incisors on the upper and on the lower jaw, which grow throughout the animal's life and must be ground down by gnawing. (The word rodent comes from the Latin word for gnawing.)

The genus Rattus

The genus Rattus, true rats, is one of the largest genera of mammals and includes as many as 78 species (Nowak 1986). True rats are native to southeast Asia, Australia, and the nearby islands. Some species build nests in trees, while others burrow into the ground. Most live in groups ranging from a few individuals to one hundred or more. Rats fight to establish dominance within the group, but rarely kill or injure each other. Sometimes females within a group will nurse each other's young (Barnett 2001).

True rats are opportunistic feeders, eating seeds, fruit, vegetables, insects, other small animals. Most true rats live in forests or near rivers or other bodies of water. In Australia, some species live in grasslands and desert environments.

Rats as pests

Brown Rat, Rattus norvegicus

Some species of rats, both true rats and rats of other genera, have become very successful by taking advantage of human activities. The black rat, Rattus rattus, which is naturally a tree dwelling species, has found nesting places and food in barns, houses, and other buildings and spread around the world with the the unwitting help of humans. The black rat was common in Europe by the time of the Roman Empire. It is also known as the roof rat and the ship rat.

The brown rat, R. norvegicus, also known as the Norway rat and the sewer rat, is a ground dweller and naturally digs its burrows near water. It gradually spread out of Asia and reached Europe in the 1700s and North and South America soon after. Brown rats mostly live low to the ground, sometimes in city sewers. In some buildings, brown rats live in the basement and black rats in the attic (Barnett 2001).

Other rat species that have come to live in close association with humans include the rice field rat (Rattus argentiventer) of southeast Asia; the Polynesian rat (R. exulans), native to southeast Asia and spread to the Pacific islands along with humans; the banicoot rats of India and Southeast Asia (Bandicota bengalensis, B. indica, and B. savilei); and the pest rat (Nesokia indica), which is found from Egypt to China (Nowak 1986).

These commensal (which means "sharing the same table") rat species do a tremendous amount of damage to human interests, mainly by eating crops and stored food and by spreading diseases. It is estimated that rats and mice consume one fifth of the food crops that humans grow each year, including 50 million tons of rice (Voelker 1986).

English ratcatcher, 1851

Rats can carry over thirty different diseases dangerous to humans, including Weil's disease, typhus, salmonella, and bubonic plague. Bubonic plague is caused by the bacteria Yersinia pestis and spread through the bite of the flea Xenopsylla cheopis. The plague bacteria and the fleas are common on wild rodents and often seem to do them no harm. When the disease spreads to commensal rats, especially the black rat, humans can be infected. In the Middle Ages plague outbreaks were common in European cities and sometimes killed 25 percent or more of an area's population. In the early twentieth century, plague killed around a million people a year in India and continues to be a problem today (Barnett 2001).

Other damage caused by rats includes damaging dams and irrigation works by burrowing, causing power outages and fires by gnawing electric wires, contaminating food, damaging furniture and many other things. About 14,000 Americans are bitten by rats every year (Voelker 1986).

Rats have also caused a lot of damage to natural environments to which they have been introduced. The black rat, which was introduced to many remote islands by early sailing ships, is listed as one of the world's 100 worst invasive species by the Invasive Species Specialist Group (ISSG 2007).

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 poison and traps. Cats, dogs. ferrets, and even snakes have also been employed to hunt rats. Professional rat-catchers can be found in many developing countries and rat control is a big business world-wide.

Domestic rats and rats as food

Laboratory rat in water maze experiment
Pet domestic brown rat.
Pet pouched rat, Cricetomys emini

The domestication of rats started in England with the sport of rat-baiting, in which rats (mostly brown rats) were put into a pit and killed by dogs. Captive rats were bred to provide a constant supply of contenders. From time to time, a white or spotted rat would be born due to genetic mutation. These were bred with each other; changing their gene pool, allowing them to become popular as pets.

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 2001).

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 2001).

Domestic rat young and adults are sometimes used as food for captive reptiles. Rats, like all mammals, are edible by humans and are sometimes captured and eaten in emergency situations. 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 in Hinduism, and the rat's bad reputation in many cultures, especially as a carrier of disease.

Pet rats, also called "fancy rats" (from the expression "rat fancy," not because the rats themselves are fancy in appearance), continue to be very popular. They are inexpensive, fairly easy to care for, active, intelligent, and can be friendly with humans. Among the other rat species sometimes kept as pets are the wood rats or pack rats of North America (Neotoma species), the giant pouched rat of Africa (Cricetomys emini), and the white-tailed rat of Africa (Mystromys albicaudatus) (Nowak 1986).

References
ISBN links support NWE through referral fees

  • Barnett, S. A. 2001. The Story of Rats: Their Impact on Us, and Our Impact on Them. Crows Nest, NSW, Australia : Allen & Unwin. ISBN 1865085197
  • Charles Darwin Research Foundation [1] Eradication of Invasive species Black rats. Retrieved October 10, 2007.
  • Invasive Species Specialist Group (ISSG). 2007. Global invasive species database: Rattus rattus Invasive Species Specialist Group Website Retrieved March 19, 2007.
  • Myers, P. 2000. Order Rodentia (rodents). Animal Diversity Web. Retrieved January 30, 2007.
  • Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. [Superfamily Muroidea (mice, rats, gerbils, and relatives. The Animal Diversity Web (online). Retrieved January 30, 2007 at http://animaldiversity.org.
  • Nowak, R. M. 1999. Walker's Mammals of the World, 6th edition. Johns Hopkins University Press. ISBN 0801857899
  • Nowak, R. M., and J. L. Paradiso. 1983. Walker's Mammals of the World. Baltimore, Maryland: The Johns Hopkins University Press. ISBN 0801825253
  • Voelker, W. 1986. The Natural History of Living Mammals. Medford, New Jersey: Plexus Publishing, Inc. ISBN 0937548081


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