Brown Rat

Taxobox
name = Brown Rat
status = LR/lc
status_system = iucn2.3
status_ref =IUCN2006|assessors=Amori|year=1996|id=19353|title=Rattus norvegicus|downloaded=12 May 2006]


regnum = Animalia
phylum = Chordata
classis = Mammalia
ordo = Rodentia
familia = Muridae
subfamilia = Murinae
genus = "Rattus"
species = "R. norvegicus"
binomial = "Rattus norvegicus"
binomial_authority = (Berkenhout, 1769)
range_

---

range_map_caption = Brown Rat range

The brown rat, common rat, Hanover rat, Norway rat, Norwegian rat, or wharf rat ("Rattus norvegicus") is one of the best known and most common rats, and also one of the largest. Thought to have originated in northern China, this rodent has now spread to all continents, except Antarctica, and is the dominant rat in Europe and much of North America. It lives wherever humans live, particularly in urban areas. It is a brown or grey rodent, with a body up to convert|25|cm|in|0|abbr=on long, with the tail a similar length; the male weighs on average convert|350|g|oz|0|abbr=on and the female convert|250|g|oz|0|abbr=on.

Selective breeding of "Rattus norvegicus" has produced the laboratory rat, an important model organism in biological research, as well as pet rats. It is the most successful mammal on the planet, other than humans. [Fragaszy, Dorothy Munkenbeck; Susan Perry. (2003) "The Biology of Traditions: Models and Evidence." Cambridge University Press. pp. 165.]

Naming and etymology

Originally called the "Hanover rat" by people wishing to link problems in 18th century England with the House of Hanover, [Donaldson, Henry Herbert. (1915) The Rat. pp. 13.] it is not known for certain why the brown rat is named "Rattus norvegicus" (Norwegian rat) as it did not originate from Norway. However, the English naturalist John Berkenhout, author of the 1769 book "Outlines of the Natural History of Great Britain", is most likely responsible for the misnomer. Berkenhout gave the brown rat the binomial name "Rattus norvegicus" believing that it had migrated to England from Norwegian ships in 1728, although no brown rat had entered Norway at that time.

By the early to middle part of the 19th century, British academics were aware that the brown rat was not native to Norway, hypothesizing (incorrectly) that it may have come from Ireland, Gibraltar or across the English Channel with William the Conqueror. [Friends' Intelligencer. (1858) Volume 14. William W. Moore, publisher. pp. 398.] As early as 1850, however, a more correct understanding of the rat's origins was beginning to develop. [Chambers, William and Robert Chambers. (1850) "Chambers's Edinburgh Journal." pp. 132.] The British novelist Charles Dickens acknowledged the misnomer in the 2 June 1888 edition of his weekly journal, "All the Year Round," writing:

"Now there is a mystery about the native country of the best known species of rat, the common brown rat. It is frequently called, in books and otherwise, the 'Norway rat,' and it is said to have been imported into this country in a ship-load of timber from Norway. Against this hypothesis stands the fact that when the brown rat had become common in this country, it was unknown in Norway, although there was a small animal like a rat, but really a lemming, which made its home there." [Dickens, Charles. (1888) "All the Year Round." New Series. Volume XLII, Number 1018. pp. 517.]

Academics began to understand the origins and corrected etymology of the brown rat towards the end of the 19th century, as seen in the 1895 text "Natural History" by American scholar Alfred Henry Miles:

"The brown rat is the species common in England, and best known throughout the world. It is said to have travelled from Persia to England less than two hundred years ago and to have spread from thence to other countries visited by English ships." [Miles, Alfred Henry. (1895) "Natural History." Dodd, Mead & Company. pp. 227]

Though the assumptions surrounding this species' origins were not yet entirely accurate, by the 20th century it was established among naturalists that the brown rat did not originate in Norway, rather that the species came from central Asia and (likely) China. [Cornish, Charles John. (1908) "The Standard Library of Natural History." The University Society, Inc. Volume 1, Chapter 9. pp. 159] Despite this, this species' common name of "Norway rat" is still in use today.

Physical characteristics

The fur is coarse and usually brown or dark grey, while the underparts are lighter grey or brown. The length can be up to convert|25|cm|in|0|abbr=on, with the tail a further convert|25|cm|in|0|abbr=on, the same length as the body. Adult body weight averages convert|350|g|oz|0|abbr=on in males and about convert|250|g|oz|0|abbr=on in females, but a very large individual can reach convert|500|g|oz|0|abbr=on. Rats weighing over convert|1|kg|lb|1|abbr=on are exceptional, and stories of rats as big as cats are exaggerations, or misidentifications of other rodents such as the coypu and muskrat.

Brown rats have acute hearing, are sensitive to ultrasound, and possess a very highly developed olfactory sense. Their average heart rate is 300 to 400 beats per minute, with a respiratory rate of around 100 per minute. The vision of a pigmented rat is poor, around 20/600, while a non-pigmented (albino) has no melanin in its eyes, and has not only around 20/1200 vision, but also a terrible scattering of light within its vision. Brown rats are dichromates who perceive colours rather like a human with red-green colorblindness, and their colour saturation may be quite faint. Their blue perception, however, also has UV perceptors, allowing them to see ultraviolet lights that some species cannot. [cite web
last = Hanson
first = Anne
title = What Do Rats See?
work = Rat Behavior and Biology
publisher = ratbehavior.org
date = 2007-03-14
url = http://www.ratbehavior.org/RatVision.htm
accessdate = 2007-12-01 ]

Biology and behavior

The Brown Rat is usually active at night and is a good swimmer, both on the surface and underwater, but unlike the related Black rat ("Rattus rattus") they are poor climbers. Brown rats dig well, and often excavate extensive burrow systems. A 2007 study found brown rats to possess metacognition, a mental ability previously only found in humans and some primates. [cite web
url=http://www.sciencedaily.com/releases/2007/03/070308121856.htm
title=Rats Capable Of Reflecting On Mental Processes
date=March 9, 2007
publisher=Science Daily — sourced from university of Georgia
accessdate=2007-08-02]

Communication

Brown rats are capable of producing ultrasonic vocalizations. As pups, young rats use different types of ultrasonic cries to elicit and direct maternal search behavior, [Brunelli et al. (1994) Hypothermic vocalizations of rat pups (Rattus norvegicus) elicit and direct maternal search behavior. "Journal of Comparative Psychology." Volume 108, Number 3. pp. 298-303.] as well as to regulate their mother's movements in the nest. [White et al. (1992) Regulation of rat maternal behavior by broadband pup vocalizations. "Behavioral and Neural Biology." Volume 58, Number 2. pp. 131-137.] Although pups will produce ultrasounds around any other rats at 7 days old, by 14 days old they significantly reduce ultrasound production around male rats as a defensive response. [Takahashi, L. K. (1992) Developmental expression of defensive responses during exposure to conspecific adults in preweanling rats (Rattus norvegicus). "Journal of Comparative Psychology." Volume 106, Number 1. pp. 69-77.] Adult rats will emit ultrasonic vocalizations in response to predators or perceived danger, [Brudzynski, Stefan M. (January 2005) Principles of Rat Communication: Quantitative Parameters of Ultrasonic Calls in Rats. "Behavior Genetics." Volume 35, Number 1. pp. 85-92.] the frequency and duration of such cries depending on the sex and reproductive status of the rat. [Blanchard et al. (1992) Sex differences in the incidence and sonographic characteristics of antipredator ultrasonic cries in the laboratory rat (Rattus norvegicus). "Journal of Comparative Psychology." Volume 106, Number 3. pp. 270-277.] [Haney, M.; K.A. Miczek. (December 1993) Ultrasounds during agonistic interactions between female rats (Rattus norvegicus. "Journal of Comparative Psychology." Volume 107, Number 4. pp. 373-379.] The female rat will also emit ultrasonic vocalizations during mating. [Thomas, D. A.; R. J. Barfield. (1985) Ultrasonic vocalization of the female rat (Rattus norvegicus) during mating. "Animal Behaviour." Volume 33, Number 3. pp. 720-725.]

Chirping

Rats may also emit short, high frequency, ultrasonic, socially induced vocalization during rough and tumble play, before receiving morphine, or having sex, and when tickled. The vocalization is described as a distinct "chirping," has been likened to laughter, and is interpreted as an expectation of something rewarding. [ [http://www.sciencenews.org/articles/20010728/fob9.asp Science News 2001] ] . Like most rat vocalizations, humans cannot hear the "chirping" without special equipment.

In clinical studies, the laughter is associated with positive emotional feelings, and social bonding occurs with the tickler, resulting in the rats becoming conditioned to seek the tickling. However, as the rats age, there appears to be a decline in the tendency to laugh. [ [http://www.psych.umn.edu/courses/fall06/macdonalda/psy4960/Readings/PankseppRatLaugh_P&B03.pdf Panksepp & Burgdorf 2003] ]

Diet

The brown rat is a true omnivore and will consume almost anything, but cereals form a substantial part of its diet., macaroni and cheese, and cooked corn kernels. According to Schein, the least-liked foods were raw beets, peaches, and raw celery. [cite journal
quotes =
last = Schein
first = Martin W.
authorlink =
coauthors = Holmes Orgain
date =
year = 1953
month =
title = A Preliminary Analysis of Garbage as Food for the Norway Rat
journal = Am. J. Trop. Med. Hyg.
volume = 2
issue = 6
pages = 1117–1130
url = http://www.ajtmh.org/cgi/content/abstract/2/6/1117
accessdate = 2007-04-04
pmid = 13104820 ]

Foraging behavior is often population-specific, and varies by environment and food source. [Fragaszy, Dorothy Munkenbeck; Susan Perry. (2003) "The Biology of Traditions: Models and Evidence." Cambridge University Press. pp. 165.] Brown rats living near a hatchery in West Virginia catch fingerling fish. [Cottam, C. (1948) Aquatic habits of the Norway rat. "Journalof Mammalogy." Volume 29. pp. 299.] Some colonies along the banks of the Po river in Italy will dive for mollusks, [Gandolfi, G.; V. Parisi. (1972) Predazione su Unio Pictorum L. da parte del ratto, Rattus norvegicus (Berkenhout). "Acta Naturalia." Volume 8. pp. 1-27.] [Parisi, V.; G. Gandolfi. (1974) Further aspects of the predation by rats on various mollusc species. "Bollettino di Zoologia." Volume 41. pp. 87-106.] a practice demonstrating social learning among members of this species. [Galef, Jr., Bennett G. (1980) Diving for Food: Analysis of a Possible Caseof Social Learning in Wild Rats (Rattus norvegicus). "Journal of Comparative and Physiological Psychology." Vol. 94, No.3. pp. 416-425. [http://sociallearning.info/home/pdf/comp%20psych%2094(3),%20416-425.pdf] ] Rats on the island of Norderoog in the North Sea stalk and kill sparrows and ducks. [Steiniger, von F. (1950). Beitrage zur Sociologie und sonstigen Biologie der Wanderratte. "Zeitschrift fur Tierpsychologie." Volume 7. pp. 356-379.]

Reproduction and life cycle

The brown rat can breed throughout the year if conditions are suitable, a female producing up to five litters a year. The gestation period is only 21 days and litters can number up to fourteen, although seven is common. The maximum life span is up to three years, although most barely manage one. A yearly mortality rate of 95% is estimated, with predators and interspecies conflict as major causes.

When lactating, female rats display a 24 hour rhythm of maternal behavior, and will usually spend more time attending to smaller litters than large ones. [Grota, L. J.; Ader, R. (1969) Continuous recording of maternal behaviour in "Rattus norvegicus". "Animal Behaviour." Volume 17, Number 4. pp. 722-729.]

Brown rats live in large hierarchical groups, either in burrows or subsurface places such as sewers and cellars. When food is in short supply, the rats lower in social order are the first to die. If a large fraction of a rat population is exterminated, the remaining rats will increase their reproductive rate, and quickly restore the old population level.

Social behaviour

It is common for rats to groom each other and sleep together. [ [http://members.madasafish.com/~cj_whitehound/Rats_Nest/Norway_Rats/Social_behaviour.htm Social behaviour of fancy rat ] ] As with dogs, rats create a social hierarchy, and each rat has its own place in the pack. There is always a dominant rat. [ [http://www.petwebsite.com/rats/rat_behavior.htm Rats : Fancy Rat Behaviour ] ] Groups of rats tend to "play fight", which can involve any combination of jumping, chasing, tumbling, and boxing. Play fighting involves rats going for each other's necks, while serious fighting involves strikes at the others' back ends. [http://www.ratbehavior.org/norway_rat_ethogram.htm#PlayFighting Norway Rat Behavior Repertoire ] ]

Distribution and habitat

Likely originating from the plains of Asia, Northern China and Mongolia, the brown rat spread to other parts of the world sometime in the Middle Ages. [Tate, G.H.H. (1936) Some muridae of the Indo-Australian region. "Bulletin of the American Museum of Natural History. Volume 72. pp. 501-728.] [Silver, J. (1941) The house rat. "Wildlife Circ." Volume 6. pp. 1-18.] [Southern, H.N. (1964) "The Handbook of the British Mammals." Blackwell Scientific, Oxford.] The question of when brown rats became commensal with humans remains unsettled, but as a species they have spread and established themselves along routes of human migration and now live almost everywhere humans do. [Yoshida, T.H. (1980) "Cytogenetics of the Black Rat: Karyotype Evolution and Species Differentiation." University of Tokyo Press, Tokyo.]

The brown rat may have been present in Europe as early as 1553, a conclusion drawn from an illustration and description by Swiss naturalist Conrad Gesner in his book "Historiae animalium," published 1551-1558. [Freye, H.A., and Thenius, E. (1968) Die Nagetiere. "Grzimeks Tierleben." (B. Grzimek, ed.) Volume 11. Kindler, Zurich. pp. 204-211.] Though Gesner's description could apply to the black rat, his mention of a large percentage of albino specimens – not uncommon among wild populations of brown rats – adds credibility to this conclusion.Suckow et al. (2006) "The Laboratory Rat," 2nd ed. Academic Press. pp. 74. ISBN 0120749033] Reliable reports dating to the 18th century document the presence of the brown rat in England in 1730, France in 1735, Germany in 1750, and Spain in 1800, becoming widespread during the Industrial Revolution.cite book |editor= Mitchell-Jones, Anthony J.|author= Amori, G. & Cristaldi, M.|year=1999 |title= The Atlas of European Mammals|publisher= Academic Press|location=London|pages= 278-279|isbn= 0-85661-130-1] It did not reach North America until around 1750-1755. [Nowak, Robert M. (1999) "Walker's Mammals of the World." JHU Press. pp. 1521. ISBN 0801857899] [Freye, H.A., and Thenius, E. (1968) Die Nagetiere. "Grzimeks Tierleben." (B. Grzimek, ed.) Volume 11. Kindler, Zurich. pp. 204-211.]

In the absence of humans, brown rats prefer damp environments such as river banks. However, the great majority are now linked to man-made environments, such as sewage systems.

It is often said that there are as many rats in cities as people, but this varies from area to area depending on climate, living conditions, etc. Brown rats in cities tend not to wander extensively, often staying within convert|20|m|ft|0|abbr=on of their nest if a suitable concentrated food supply is available, but they will range more widely where food availability is lower. In New York City there is great debate over the size of the rat population with estimates from almost 100 million rats to as few as 250,000.cite web | title = New Yorkers vs. the Rat | url = http://www.gothamgazette.com/article/issueoftheweek/20071126/200/2356 | accessdate = 2008-03-15] Experts suggest New York is a particularly attractive place for rats because of its aging infrastructure, high moisture and poverty rates. Not surprisingly, there is a direct correlation between the degree of rat infestation among neighborhoods in New York City and the risk of residents of those neighborhoods getting bitten by rats. [Childs et al. (1998) Epidemiology of Rodent Bites and Prediction of Rat Infestation in New York City. "American Journal of Epidemiology." Vol. 148, No. 1. pp. 78-87. [http://aje.oxfordjournals.org/cgi/reprint/148/1/78] ]

In the United Kingdom some figures show that the rat population has been rising, with estimations that 81 million rats reside in the UK.cite web | last = Spanton | first = Tim | title = Britain plagued by 80 m rats | url = http://www.thesun.co.uk/sol/homepage/news/article757835.ece | accessdate = 2008-03-15] Those figures would mean that there are 1.3 rats per person in the country. High rat populations in the UK are often attributed to the mild climate, which allow them higher survival rates during the winter months.

The only brown rat-free zones in the world are the Arctic, the Antarctic, some especially isolated islands, the province of Alberta in Canada, [cite news |first=Brian |last=Handwerk |title=Canada Province Rat-Free for 50 Years |url= http://news.nationalgeographic.com/news/2003/03/0331_030331_rats.html|work=National Geographic News |publisher=National Geographic Society |date=March 31, 2003 |accessdate=2007-11-30 ] and certain conservation areas in New Zealand [http://www.beehive.govt.nz/node/16920 [http://www.beehive.govt.nz/node/16920] ] [Perrow, Martin and A. J. Davy. (2002) "Handbook of Ecological Restoration." Cambridge University Press. pp. 362-363. ISBN 0521791286]

Antarctica is almost completely covered by ice and has no permanent human inhabitants, making it uninhabitable by rats. The Arctic has extremely cold winters that rats cannot survive outdoors, and the human population density is extremely low making it difficult for rats to travel from one habitation to another. When the occasional rat infestation is noticed and eliminated, the rats are unable to re-infest it from an adjacent one. Isolated islands are also able to eliminate rat populations because of low human population density and geographic distance from other rat populations.

Legislation in Canada

Alberta is unusual in that rat infestation was eliminated by aggressive government action. [cite web
last = Bourne
first = John
title = The History of Rat Control In Alberta
work = Agriculture and Food
publisher = Alberta Department of Agriculture
date = 2002-10-01
url = http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3441
accessdate = 2007-12-01 ] Although it is a major agricultural area and has a fairly high human population density, it is far from any seaport and only a portion of its eastern boundary with Saskatchewan provides a favorable entry route for rats. They cannot survive in the boreal forest to the north, the Rocky Mountains to the west, nor the semi-arid High Plains of Montana to the south. The first brown rat did not reach Alberta until 1950, and in 1951 the province launched a rat-control program that included shooting and poisoning rats, and bulldozing, burning down, and blowing up rat-infested buildings. The effort was backed by legislation that required every person and every municipality to destroy and prevent the establishment of designated pests. If they failed, the provincial government could carry out the necessary measures and charge the costs to the landowner or municipality.

In the first year of the program, convert|64|t|ST|lk=on of arsenic trioxide were spread throughout 8,000 buildings on farms along the Saskatchewan border. In 1953 the much less toxic and more effective poison, Warfarin, was introduced. By 1960 the number of rat infestations in Alberta dropped to below 200 per year. [cite web
url=http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm3266
title=Keep Alberta Rat-free for another 50 years
publisher=Alberta Department of Agriculture
accessdate=2007-08-02]

Currently, only zoos, universities, and research institutes are allowed to own caged rats in Alberta, and possession of an unlicensed rat (including pet rats) is punishable by a $5,000 fine or 60 days in jail. The adjacent and similarly landlocked province of Saskatchewan initiated a rat control program in 1972, and has managed to reduce the number of rats in the province substantially, although they have not been eliminated. [cite web
title = Rat Control in Saskatchewan
publisher = Saskatchewan Agriculture, Food and Rural Revitalization
date = 2003-10-01
url = http://www.agriculture.gov.sk.ca/Default.aspx?DN=27cf4285-0e33-47b4-88c0-9de3c729eca7
format = PDF
accessdate = 2007-12-01 ]

New Zealand

First arriving before 1800 (perhaps on James Cook's vessels), [Atkinson, I.A.E. (1973) Spread of the Ship Rat ("Rattus r. rattus" L.) in New Zealand. "Journal of the Royal Society of New Zealand." Volume 2, Number 3. pp. 457-472.] brown rats have posed a serious threat to many of New Zealand's native animals. Rat eradication programmes within New Zealand have led to rat-free zones on offshore islands and even on fenced "ecological islands" on the mainland. Before an eradication effort was launched in 2001, the sub-Antarctic Campbell Island had the highest population density of brown rats in the world. [cite news
url=http://news.bbc.co.uk/2/hi/asia-pacific/2938612.stm
title=NZ routs island rats
date=26 May, 2003
publisher=BBC News
accessdate=2007-08-02]

Diseases

Brown rats carry some diseases, including Weil's disease, rat bite fever, cryptosporidiosis, Viral hemorrhagic fever (VHF), Q fever and hantavirus pulmonary syndrome. In the United Kingdom, brown rats are an important reservoir for "Coxiella burnetii," the bacteria that causes Q fever, with seroprevalence for the bacteria found to be as high as 53% in some wild populations. [Webster JP, Lloyd G, Macdonald DW. (January 1995) Q fever (Coxiella burnetii) reservoir in wild brown rat (Rattus norvegicus) populations in the UK. "Parasitology." Volume 110. pp. 31-55.]

This species can also serve as a reservoir for "Toxoplasma gondii", the parasite that causes toxoplasmosis, though the disease usually spreads from rats to humans when domestic cats feed on infected brown rats. [Dubeya, J. P. and J. K. Frenkel. (May 1998) Toxoplasmosis of rats: a review, with considerations of their value as an animal model and their possible role in epidemiology. "Veterinary Parasitology." Volume 77, Issue 1. pp. 1-32.] The parasite has a long history with the brown rat, and there are indications that the parasite has evolved to alter an infected rat's perception to cat predation, making it more susceptible to predation and increasing the likelihood of transmission. [Berdoy, M., J. P. Webster, D. W. MacDonald. (August 2000) Fatal attraction in rats infected with "Toxoplasma gondii". "Proceedings of the Royal Society of London: Biological Sciences." Volume 267, Number 1452. pp. 1591-1594. [http://journals.royalsociety.org/content/f2hh7806ddltrrqc/fulltext.pdf] ]

Surveys and specimens of brown rat populations throughout the world have shown that this species is often associated with outbreaks of trichinosis, [Samuel et al. (2001) "Parasitic Diseases of Wild Mammals." Blackwell Publishing. pp. 380-393. ISBN 081382978X.] [Leiby et al. (June 1990) Trichinella spiralis in an Agricultural Ecosystem: Transmission in the Rat Population. "The Journal of Parasitology." Vol. 76, No. 3. pp. 360-364.] but the extent to which the brown rat is responsible in transmitting "Trichinella" larvae to humans and other synanthropic animals is at least somewhat debatable. [Stojcevic et al. (June 2004) The Epidemiological Investigation of Trichinella Infection in Brown Rats (Rattus norvegicus) and Domestic Pigs in Croatia Suggests That Rats are not a Reservoir at the Farm Level. "Journal of Parasitology." Volume 90, Issue 3. pp. 666-670.] "Trichinella pseudospiralis", a parasite previously not considered to be a potential pathogen in humans or domestic animals, has been found to be pathogenic in humans and carried by brown rats. [Ranque et al. (September-October 2000) "Trichinella pseudospiralis" Outbreak in France. "Emerging Infectious Diseases." Volume 6, Number 5. pp. 543-547. [http://www.cdc.gov/ncidod/eid/vol6no5/pdf/ranque.pdf] ]

Brown rats are sometimes mistakenly thought to harbor bubonic plague, a possible cause of The Black Death. However, the bacteria responsible, "Yersinia pestis", incubates in only a few rodent species and is usually transmitted zoonotically by rat fleas - common rodents include ground squirrels and wood rats. In short, a brown rat may catch fleas that have plague, but cannot contract the disease itself, whereas other non-rodent species like dogs, cats, and humans can be bitten by diseased fleas or come in contact with an infected animal and then become infected themselves.cite-web|url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/51900.htm|title=Merck Veterinary Manual|accessdate=2007-02-14]

In captivity

Uses in science

Selective breeding of the brown rat has produced the albino laboratory rat. Like mice, these rats are frequently subjects of medical, psychological and other biological experiments and constitute an important model organism. This is because they grow quickly to sexual maturity and are easy to keep and to breed in captivity. When modern biologists refer to "rats", they almost always mean "Rattus norvegicus".

As pets

The brown rat, along with the black rat to a lesser degree, is kept as a pet in many parts of the world. Australia, the United Kingdom, and the United States are just a few of the countries that have formed fancy rat associations similar in nature to the American Kennel Club, establishing standards, orchestrating events, and promoting responsible pet ownership.

As pet food

Because of their quick reproduction, rats are also used as live food for captive animals, commonly large reptiles such as snakes.

Different views exist on the topic of feeding live rats, or other species, to captive animals. Some organizations feel there is a large potential for injury to the reptiles if they are fed live animals instead of prekilled. A captive animal that does not kill the rat quickly enough will often suffer injury, e.g., from being bitten or scratched. Even feedings supervised by the owner of the captive animal can result in an injured or dead animal, as rats in particular are faster than humans and many other animals. [cite web
url=http://www.anapsid.org/prekill.html
title=Feeding Prekilled vs. Live Prey
author=Melissa Kaplan
year=1995
publisher=Melissa Kaplan's Herp Care Collection]

Other groups view the practice of feeding live rats to reptiles as cruelty to animals because the rat is not guaranteed a quick or painless death, and equate it to rat baiting or cockfighting, which are illegal in most parts of the world. These groups feel that reptiles should be conditioned to accept dead rats, as is the rule with many zoos.

Some countries, such as South Africa, as well as various municipalities worldwide, have banned the feeding of live vertebrate animals (like rats) to predators because the practice is seen as inhumane. [cite news
url=http://www.int.iol.co.za/index.php?set_id=14&click_id=14&art_id=qw1121953501827B212
title= Guinea pig saved from being snake's snack
date=July 21, 2005
publisher=Independent Online, a wholly owned subsidiary of Independent News & Media
accessdate=2007-08-02]

References

External links

Overviews
* [http://www.ratbehavior.org/rats.html Rat behaviour and biology] A detailed set of pages by biologist Anne Hanson.
* [http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_norvegicus.html Rattus norvegicus] The University of Michigan Museum of Zoology
* [http://genomics.senescence.info/species/entry.php?species=Rattus_norvegicus Life cycle data sheet for Rattus Norvegicus] Written by biologist João Pedro de Magalhães
* [http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/171542.htm Rats and Mice: Overview] Online version of the Merck veterinary manual.
* [http://www.arkive.org/species/ARK/mammals/Rattus_norvegicus/ ARKive] Still photos. Videos.

Rattus norvegicus genome & use as model animal
* [http://www.nature.com/nature/focus/ratgenome/ Nature: Rat Genome]
* [http://rgd.mcw.edu/ Rat Genome Database]