Rats
Black Rat (Rattus rattus)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Rodentia Family: Muridae* Subfamily: Murinae Genus: Rattus
Species
50 species; see text Several subfamilies of Murids 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 300 grams.

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

Varieties

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

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. Generally, these lines are not transgenic, however, 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.

main article: Fancy rat

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.

Raising rats as a hobby is known as rat fancy; people who enjoy keeping rats as pets are often known as rat fanciers. Rat fanciers have bred many exotic rat varieties. Besides rats with unusual colouring, there have been rats bred that have bigger ears, no fur, no tails and oversized hind legs.

Fancy Rats have been exhibited in Britain for almost a hundred years. The originator of the first true domestic rats was Jack Black, official Rat Catcher and Mole Destroyer by appointment to Queen Victoria. His rats were bred from rattus norvegicus stock. Pet rats became very popular in the 1970s when the National Fancy Rat Society was founded. Other rat societies have since sprung up in other countries as pet rats have gained in popularity worldwide.

Pet rats live to around 2-3 years of age. Adult bucks weigh around 500g and adult does around 300g. Rats are naturally social animals, and, as pets, are much happier when kept in single sex pairs rather than on their own. Both bucks and does make good pets.

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 sterotyped as cute and bourgeois.

• 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 1865085197.