Rats

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

Rats are distinguished from mice by their size; rats generally have bodies longer than 12 cm (5 in).

Contents

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* 1 Species and description

* 2 As pets

* 3 As subjects of scientific research

* 4 Laughter in rats

* 5 As food

* 6 In culture

o 6.1 In Eastern cultures

o 6.2 In Western cultures

o 6.3 In religion

o 6.4 In popular culture

* 7 Taxonomy of Rattus

o 7.1 Species of rats

* 8 Further reading

* 9 References and notes

* 10 See also

* 11 External links

[edit] 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).[citation needed] Wild rats living in good environments are typically healthy and robust animals. Wild rats living in cities may suffer from poor diets and internal parasites and mites, but do not generally spread disease to humans.

The normal lifespan of rats ranges from two to five years, and is typically three years.

[edit] As pets

A domesticated rat, trained to stay on its owner's shoulder.

A domesticated rat, trained to stay on its owner's shoulder.

Main article: Fancy rat

Specially bred rats have been kept as pets at least since the late 19th century. Rats are 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.

[edit] As subjects of scientific research

Main Article: Brown rats in science

A laboratory rat strain known as a Zucker rat. These rats are bred to be genetically prone to diabetes, the same metabolic disorder found among humans.

A laboratory rat strain known as a Zucker rat. These rats are bred to be genetically prone to diabetes, the same metabolic disorder found among humans.

In 1895, Clark University in Worcester, Massachusetts (United States) established a population of domestic white brown rats to study the effects of diet and for other physiological studies. Over the years, rats have been used in many experimental studies, which have added to our understanding of genetics, diseases, the effects of drugs, and other topics that have provided a great benefit for the health and wellbeing of humankind. Laboratory rats have also proved valuable in psychological studies of learning and other mental processes (Barnett 2002). A 2007 study found rats to possess metacognition, a mental ability previously only found in humans and some primates.[1][2]

On January, 2008, Doris Taylor, director, Center 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