The Online Encyclopedia and Dictionary







This is an article about wild rats; for pet rats, see Fancy rat


|- | style="text-align:center;" | Black Rat
Black Rat (Rattus rattus) |- style="text-align:center;" ! style="background: pink;" | Scientific classification |- style="text-align:center;" |

|- valign=top |Kingdom:||Animalia |- valign=top |Phylum:||Chordata |- valign=top |Class:||Mammalia |- valign=top |Order:||Rodentia |- valign=top |Family:||Muroidea* |- valign=top |Family:||Muridae |- valign=top |Subfamily:||Murinae |- valign=top |Genus:||Rattus |} |- style="text-align:center; background:pink;" !Species |- | 50 species; see text
*Several subfamilies of Muroids
include animals called rats. |} A rat is a small omnivorous rodent of the genus Rattus. Rats are mammals somewhat bigger than their relatives the mice, but seldom weighing over 500 grams.

The term rat is also used in the names of other small mammals which are not true rats. Examples include the wood or pack rat, a number of species loosely called kangaroo rats and the Bandicoot Rat , Bandicota bengalensis.

In Western countries, many people keep domestic rats as pets. Descendants of Norwegian rats bred for research, these animals are often called "fancy rats", "coloured rats" or "colour rats." Domesticated rats tend to be both more docile than their wild ancestors and more disease prone, presumably due to inbreeding.



There are over 50 species of rats, the most well-known of which are the Brown Rat, Rattus norvegicus; the Black Rat, Rattus rattus; and the Polynesian Rat, Rattus exulans.

These three common species often live with and near humans, share their food and spread disease. At least one of these three species occurs on over 80% of island groups around the world and they have caused about half of bird and reptile extinctions. The Black Plague is believed to have been spread by rat-borne parasites. Rats are also blamed for damaging food supplies and other goods. They have a very poor reputation; in the English language, "rat" is an insult and "to rat on someone" is to betray them by denouncing a crime or misdeed they committed to the authorities.

Rats might eat each other in stressful environments or when the number of rats in a space is very high, but cannibalism to prevent diseases from spreading is normal, where dead rats are eaten before they start spreading diseases.

Rats in the laboratory

Like mice, rats (especially albino Rattus norvegicus) are frequently subjects of medical, psychological and other biological experiments due to their rapid growth to sexual maturity and because rats are easily kept and bred in captivity. Scientists have bred many strains or "lines" of rats specifically for experimentation. However, these lines are generally not transgenic because the easy techniques of genetic transformation that work in mice do not work in rats. This has frustrated many investigators, who regard many aspects of behavior and physiology in rats as more relevant to humans and easier to observe than in mice, but who wish to trace their observations to underlying genes. As a result, many researchers have been forced to study questions in mice that might be better pursued in rats. In October 2003, however, researchers succeeded in cloning two laboratory rats by the problematic technique of nuclear transfer. This may lead to more rats being used as genetic research subjects.

Rats in culture

In imperial Chinese culture, the rat (sometimes referred to as a mouse) is the first of the twelve animals of the Chinese zodiac. Consequently every twelfth year is known as a "year of the rat" in the Chinese calendar. People born in such years 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 stereotypes associated with rats in Western civilization are less complimentary. Rats are seen as vicious, unclean, parasitic animals that steal food and spread disease. When anthropomorphized, rats are usually depicted as selfish, crude and untrustworthy, with the characters of The Secret of NIMH being the major exception. Describing a person as ratlike usually implies they are unattractive and suspicious. By contrast, mice are stereotyped as cute and bourgeois.

See also

Taxonomy of Rattus

The genus Rattus is a member of the giant subfamily Murinae. There are several other murine genera that are sometimes considered part of Rattus. These are: 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 natives
  • New Guinea natives
  • xanthurus group

The following list is alphabetical.

Species of Rats

  • Genus Rattus
    • Rattus adustus
    • Rattus annandalei
    • Rattus argentiventer
    • Rattus baluensis
    • Rattus bontanus
    • 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

Further reading and references

  • The Story of Rats: Their Impact on Us, and Our Impact on Them, S. Anthony Barnett, Allen & Unwin, Crows Nest, NSW, Australia, 2002, trade paperback, 202 pages, ISBN 1-86508-519-7.
  • Musser, G. G. and M. D. Carleton. 1993. Family Muridae. Pp. 501-755 in Mammal Species of the World a Taxonomic and Geographic Reference. D. E. Wilson and D. M. Reeder eds. Smithsonian Institution Press, Washington D.C.
  • Nowak, R. M. 1999. Walker's Mammals of the World, Vol. 2. Johns Hopkins University Press, London.

External links

  • Rat Genome Database

Last updated: 02-07-2005 02:52:08
Last updated: 05-03-2005 17:50:55