Rats are medium-sized rodents that are commonly distinguished from mice by their larger size. The best known rat species are the black rat and brown rat, which originated in Asia. Rats can carry diseases and have caused epidemics like the Black Death. While some rats are considered pests, others are kept as pets or used in scientific research due to their intelligence and ability to learn. Rat meat is also consumed as a food in some cultures.

1. 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. Generally, when someone discovers a
large muroid rodent, its common name includes the term rat, while if it is smaller, the name includes
the term mouse. The muroid family is broad and complex, and the common terms rat and mouse are
not taxonomically specific. 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
A river rat
A rat in a city street
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 500 grams
(1.1 lb) in the wild.[citation needed]
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,

2. 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.[citation needed]
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.[1]
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.[citation needed]
Wild rodents, including rats, can carry many different zoonotic pathogens, such
as Leptospira, Toxoplasma gondii, and Campylobacter.[2]
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.[citation needed]
A rat in a suburb of Vancouver
The average lifespan of any given rat depends on which species is being discussed, but many only
live about a year due to predation.[citation needed]
The black and brown rats diverged from other Old World rats during the beginning of
the Pleistocene in the forests of Asia.[citation needed]
Pets
Main article: Fancy rat

3. A domesticated rat
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 from their wild counterparts depending on howmany generations they
have been kept as pets.[3]
Pet rats do not pose any more of a health risk than pets such
as cats or dogs.[4]
Tamed rats are generally friendly and can be taught to perform selected behaviors.
Subjects for scientific research
Main article: Laboratory rat
A laboratory rat strain, known as a Zucker rat, is 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 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 well-being 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.[5][6]

4. 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,[7]
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, andadaptability.
Their psychology, in many ways, seems to be similar to humans. Entirely new breeds or "lines" of
brown rats, such as the Wistar rat, have been bred for use in laboratories. Much of the genome
of Rattus norvegicus has been sequenced.[8]
Generalintelligence[improper synthesis?]
This section needs additional citations for verification. Please
help improve this article by adding citations to reliable sources.
Unsourced material may be challenged and removed. (January 2015)
Because of evident displays of their ability to learn,[citation needed]
rats were investigated early to see
whether they exhibit general intelligence, as expressed by the definition of a g factor and observed in
larger, more complex animals.[citation needed]
Early studies ca. 1930 found evidence both for and against
such a g factor in rat.[9][10]
Quoting Galsworthy, with regard to the affirmative 1935 Thorndike work:[11]
Robert Thorndike, for example, provided strong evidence for g in rats by the use of a variety of tests
such as mazes, problem-solving tasks, and simple avoidance conditioning... Performances tended to
correlate across tasks, with stronger associations found between mazes and problem-solving than
with simple avoidance tasks. Thorndike... also reviewed a dozen earlier studies which also
suggested that the highest correlations are found between more complex problem-solving tasks.
However, it should be noted that there were other contemporary studies that found split or near zero-
order correlation matrices for other populations of rats across cognitive batteries...[11]
However, some more contemporary work has not supported the earlier affirmative
view.[12]
Throughout the 1990s and into the 2000s, series of articles have appeared attempting to
address the question of general intelligence in this species, through measurements of tasks
performed by rats and mice, e.g., with statistical evaluation by factor analysis, and seeking to
correlate general intelligence and brain size (as is done with humans and primates),[medical citation needed][13][full
citation needed]
where the general conclusion was in the affirmative.[need quotation to verify][improper synthesis?][citation needed]

5. Socialintelligence[improper synthesis?]
A 2011 controlled study found that rats are actively prosocial.[citation needed]
They demonstrate apparent
altruistic behaviour to other rats in experiments, including freeing them from cages: when presented
with readily available chocolate chips, test subjects would first free the caged rat, and then share the
food. All female rats in the study displayed this behaviour, while 30% of the males did not.[14]
Food
Rat meat dishes in Yangshuo,Guangxi, China
Rat meat is a food that, while taboo[15][16]
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 diets.
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.[17]
Conversely,
the Musahar community in north India has commercialised rat farming as an exotic delicacy.[18]
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.[19]
In studying precontact
archaeological sites in Hawaii, archaeologists have found the concentration of the remains of rats
associated with commoner households accounted 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 the rats were eaten as food. The greater occurrence of rat remains
associated with commoner households may indicate the elites of precontact Hawaii did not consume
them as a matter of status or taste.[20]
Bandicoot rats are an important food source among some peoples in Southeast Asia, and the United
Nations Food and Agriculture Organization estimated 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

6. the American South were known to hunt wood rats (among other animals) to supplement their food
rations,[21]
and Aborigines along the coast in southern Queensland, Australia, regularly included rats
in their diet.[22]
Ricefield rats (Rattus argentiventer) have traditionally been used as food in rice-producing regions
such as Valencia, as immortalized by Vicente Blasco Ibáñez in his novel Cañas y barro. Along
with eeland local beans known as garrafons, rata de marjal (marsh rat) is one of the main
ingredients in traditional paella (later replaced by rabbit, chicken and seafood).[23]
Ricefield rats are
also consumed in the Philippines, the Isaan region of Thailand, and Cambodia. In late 2008, Reuters
reported the price of rat meat had quadrupled in Cambodia, creating a hardship for the poor who
could no longer afford it.
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
theShipibo people of Peru and Sirionó people of Bolivia have cultural taboos against the eating of
rats.[24][25]
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 are available to individual snake owners, as well as to
large reptile zoos, from many suppliers. 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 into place mainly because of the pressure of the RSPCA and
people who found it cruel.
Medicine
Rats can serve as zoonotic vectors for certain pathogens and thus cause disease, such as Lassa
fever, leptospirosis and Hantavirus infection.[citation needed]
Odor detection
Rats have a keen sense of smell and are easy to train. These characteristics have been employed,
for example, by the Belgian non-governmental organization APOPO, which trains rats
(specificallyAfrican giant pouched rats) to detect landmines and diagnose tuberculosis through
smell.[26]
Rats as pests

7. Rats have long been considered deadly pests. Once considered a modern myth, the rat
flood in India has now been verified. Indeed every fifty years, armies of bamboo rats descend upon
rural areas and devour everything in their path.[27]
Rats have long been held up as the chief villain in
the spread of the Bubonic Plague,[28]
however recent studies show that they alone could not account
for the rapid spread of the disease through Europe in the Middle Ages.[29]
Still, the Center for Disease
Control does list nearly a dozen diseases [30]
directly linked to rats. Most urban areas battle rat
infestations.Rats in New York City are famous for their size and prevalence. The urban legend that
the rat population in Manhattan equals that of its human population (a myth definitively refuted by
Robert Sullivan in his book "Rats") speaks volumes about New Yorkers' awareness of the presence,
and on occasion boldness and cleverness, of the rodents.[31]
New York has specific regulations for
getting rid of rats—multi-family residences and commercial businesses must use a specially trained
and licensed exterminator.[32]
Places to look for rat infestations are around pipes, behind walls and
near garbage cans. Effective rat control requires municipal workers and individuals to work
together.[citation needed]
Rats as invasive species
When introduced into locations where rats previously did not exist they can cause a huge amount
of environmental degradation. Rattus rattus, the black rat, is considered to be one of the world's
worst invasive species.[33]
Also known as the ship rat, it has been carried world-wide as
a stowaway on sea-going vessels for millennia and has usually accompanied men to any new area
visited or settled by human beings by sea. The similar but more aggressive species Rattus
norvegicus, the brown rat or wharf rat, has also been carried world wide by ships in recent
centuries.
The ship or wharf rat has contributed to the extinction of many species of wildlife including birds,
small mammals, reptiles, invertebrates, and plants, especially on islands. True rats are omnivorous
and capable of eating a wide range of plant and animal foods. True rats have a very high birth rate.
When introduced to a new area, they quickly reproduce to take advantage of the new food supply. In
particular, they prey on the eggs and young of forest birds, which on isolated islands often have no
other predators and thus have no fear of predators.[34]
Some experts believe that rats are to blame for
between 40 percent and 60 percent of all seabird and reptile extinctions, with 90 percent of those
occurring on islands. Thus man has indirectly caused the extinction of many species by accidentally
introducing rats to new areas.[35]
Rat-free areas

8. The only rat-free continent is Antarctica, due to its hostile climate which is too severe for rat survival,
and its lack of human habitation to provide buildings to shelter them from the weather. However, rats
have been introduced to many of the islands near Antarctica, and because of their destructive effect
on native flora and fauna, efforts to eliminate them are on-going. In particular, Bird Island (just off rat-
infested South Georgia), where breeding seabirds could be badly affected if rats were introduced, is
subject to special measures and regularly monitored for rat invasions.[36]
As part of island restoration some islands' rat populations have been eradicated to protect or restore
the ecology. Hawadax Island, Alaska was declared rat free after 229 years and Campbell Island,
New Zealand after almost 200 years. Breaksea Island in New Zealand was declared rat free in 1988
after an eradication campaign based on a successful trial on the smaller Hawea Island nearby.
In January, 2015 an international "Rat Team" set sail from the Falkland Islands for the British
Overseas Territory of South Georgia on board a ship carrying three helicopters and 100 tons of rat
poison with the objective of "reclaiming the island for its seabirds". Rats have wiped out more than
90% of the seabirds on South Georgia, and the sponsors hope that once the rats are gone, it will
regain its former status as home to the greatest concentration of seabirds in the world. The South
Georgia Heritage Trust, which organized the mission describes it as "five times larger than any other
rodent eradication attempted worldwide". [37]
That would be true if it were not for the rat control
program in Alberta (see below).
The Canadian province of Alberta (population 4.1 million) is notable for being the largest inhabited
area on Earth (bigger than any country in the European Union including France) which is free of true
rats. It has large numbers of pack rats, also called bushy-tailed wood rats, but they are native
species which are much less destructive than true rats. They are forest-dwelling vegetarians, and
their worst trait is that because of their attraction for shiny objects, they tend to sneak into cabins and
hotels and steal jewelry, silverware, and other valuable items.[38]
Alberta is one of only two Canadian provinces with no sea access, and was settled relatively late in
North American history. The black rat cannot survive in its climate at all, and brown rats must live
near people and their structures. They cannot evade the numerous predators in natural areas or
survive the winters in farm fields. It took until 1950 for invading rats to make their way to Alberta over
land from Eastern Canada.[39]
Immediately upon their arrival at the eastern border
with Saskatchewan, the Alberta government implemented an extremely aggressive rat control
program to stop them from advancing further. A systematic detection and eradication system was
used throughout a control zone about 600 kilometres (400 mi) long and 30 kilometres (20 mi) wide
along the eastern border of the province to eliminate rat infestations before the rats could spread

9. further into the province. Shotguns, bulldozers, high explosives, poison gas, and incendiaries were
used to destroy rats. Numerous farm buildings were destroyed in the process. Initially, tons
of arsenic trioxide were spread around thousands of farm yards to poison rats, but soon after the
program commenced the rodenticide and medical drug warfarin was introduced, which is much safer
for people (it is a commonly prescribed medicine), and more effective at killing rats than arsenic.[40]
Forceful government control measures, strong public support and enthusiastic citizen participation
continue to keep rat infestations to a minimum.[41]
The effectiveness has been aided by a similar but
newer program in Saskatchewan which prevents rats from even reaching the Alberta border. The
program still actively employs an armed rat patrol (in this case, not just a TV show) along Alberta's
borders, about ten single rats are found and killed per year, and occasionally a large localized
infestation has to be dug out with heavy machinery, but the number of rat infestations (two or more
rats) found in most recent years has averaged about three, and in many years has been zero.