Editing Brown rat (section)

== Distribution and habitat ==
[[File:NYC Rat in a Flowerbox by David Shankbone.jpg|thumb|A brown rat in a flower box in the [[East Village, Manhattan|East Village]] of New York City]]

Possibly originating from the plains of northern China and Mongolia, the brown rat spread to other parts of the world sometime in the Middle Ages.<ref>{{cite journal |last1=Tate |first1=G.H.H. |year=1936 |title=Some muridae of the Indo-Australian region
|journal=[[Bulletin of the American Museum of Natural History]] |volume=72 |pages=501–728 |hdl=2246/834}}</ref><ref>{{cite journal |last1=Silver |first1=J. |year=1941 |title=The house rat |journal=Wildlife Circ. |volume=6 |pages=1–18}}</ref><ref>{{cite book |last1=Southern |first1= H.N. |year=1964 | title=The Handbook of the British Mammals |publisher=Blackwell Scientific |location=Oxford |url=https://books.google.com/books?id=1akyAAAAMAAJ}}</ref> 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 are.<ref>{{cite book |last1=Yoshida |first1=T.H. |year=1980 |title=Cytogenetics of the Black Rat: Karyotype Evolution and Species Differentiation |publisher=University of Tokyo Press |isbn=978-0-8391-4131-0 |url=https://archive.org/details/cytogeneticsofbl0000yosi }}</ref>

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.<ref name="Freye, H.A. 1968 pp. 204-211">Freye, H.A., and Thenius, E. (1968) Die Nagetiere. ''Grzimeks Tierleben''. (B. Grzimek, ed.) Volume 11. Kindler, Zurich. pp. 204–211.</ref> 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.<ref name=Suckow>Suckow et al. (2006) ''The Laboratory Rat'', 2nd ed. Academic Press. pp. 74. {{ISBN|0-12-074903-3}}.</ref> Reliable reports dating to the 18th century document the presence of the brown rat in Ireland in 1722, England in 1730, France in 1735, Germany in 1750, and Spain in 1800,<ref name="Suckow"/> becoming widespread during the [[Industrial Revolution]].<ref name=AoEM>{{cite book |editor=Mitchell-Jones, Anthony J. |author1=Amori, G. |author2=Cristaldi, M. |name-list-style=amp |year=1999 |title=The Atlas of European Mammals |publisher=Academic Press
|location=London |pages=278–279 |isbn=978-0-85661-130-8}}</ref> It did not reach North America until around 1750–1755.<ref name="Freye, H.A. 1968 pp. 204-211" /><ref>Nowak, Robert M. (1999) ''Walker's Mammals of the World.'' JHU Press. pp. 1521. {{ISBN|0-8018-5789-9}}.</ref>

As it spread from Asia, the brown rat generally displaced the black rat in areas where humans lived. In addition to being larger and more aggressive, the change from wooden structures and thatched roofs to bricked and tiled buildings favored the burrowing brown rats over the arboreal black rats. In addition, brown rats eat a wider variety of foods, and are more resistant to weather extremes.<ref>Rowland, Ta . [http://www.independent.com/news/2009/dec/04/ancient-origins-modern-pet-rats/?print "Ancient Origins of Pet Rats"] {{Webarchive|url=https://web.archive.org/web/20150924200319/http://www.independent.com/news/2009/dec/04/ancient-origins-modern-pet-rats/?print |date=24 September 2015 }}, ''[[Santa Barbara Independent]]'', 4 December 2009.</ref>

In the absence of humans, brown rats prefer damp environments, such as river banks.<ref name="AoEM"/> 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. It is difficult to determine the extent of their home range because they do not utilize a whole area but rather use regular runways to get from one location to another.<ref>{{cite journal |last1=Davis |first1=D.E. |last2= Emlen |first2=J.T. |last3=Stokes |first3=A.W. |title=Studies on Home Range in the Brown Rat |journal=Journal of Mammalogy |date=1948 |volume=29 |issue= 3 |page=207 |doi=10.2307/1375387 |jstor=1375387}}</ref> There is great debate over the size of the population of [[rats in New York City]], with estimates from almost 100 million rats to as few as 250,000.<ref name="Gotham_1107">{{cite web |title=New Yorkers vs. the Rat |work = Gotham Gazette|url= http://www.gothamgazette.com/article/issueoftheweek/20071126/200/2356 |date = 26 November 2007}}</ref> Experts suggest that New York is a particularly attractive place for rats because of its aging infrastructure and high poverty rates.<ref name="Gotham_1107"/> In 2023, the city appointed [[Kathleen Corradi]] as the first [[Rat Czar]], a position created to address the city's rat population. The position focuses on instituting policies measures to curb the population such as garbage regulation and additional rat [[trapping]]. In addition to sewers, rats are very comfortable living in alleyways and residential buildings, as there is usually a large and continuous food source in those areas.<ref>{{cite book |last1=Sullivan |first1=Robert |title=Rats: observations on the history and habitat of the city's most unwanted inhabitants |location=New York |publisher=Bloomsbury |year=2003 |isbn=978-1-58234-385-3 |url=https://archive.org/details/ratsobservations00sull }}</ref>

In the United Kingdom, some figures show that the rat population has been rising, with estimations that 81 million rats reside in the UK<ref>{{Cite book|last=Harris|first=S.|title=A review of British mammals: Population estimates and conservation status of British mammals other than cetaceans|publisher=Joint Nature Conservation Committee|year=1995|isbn=1-873701-68-3|location=United Kingdom}}</ref> 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. With the increase in global temperature and glacier retreat, it is estimated that brown rat populations will see an increase.<ref>{{cite journal |last1=Cook |first1=A.J. |last2=Poncet |first2=S. |last3=Cooper |first3=A.P.R. |last4=Herbert |first4=D.J. |last5=Christie |first5=D. |name-list-style=amp |title=Glacier retreat on South Georgia and implications for the spread of rats |journal=Antarctic Science |date=2010 |volume=22 |issue=3 |pages=255–263 |doi=10.1017/S0954102010000064 |bibcode=2010AntSc..22..255C |s2cid=128488414 |url=https://www.researchgate.net/publication/231799807}}</ref>

In tropical and desert regions, brown rat occurrence tends to be limited to human-modified habitats.<ref name=iucn /> Contiguous rat-free areas in the world include the continent of Antarctica, the [[Arctic]],<ref>{{cite journal |last1=Puckett |first1=Emily E. |last2=Park |first2=Jane |last3=Combs |first3=Matthew |last4=Blum |first4=Michael J. |last5=Bryant |first5=Juliet E. |last6=Caccone |first6=A. |last7=Costa |first7=F. |last8=Deinum |first8=E.E. |last9=Esther |first9=A. |last10=Himsworth |first10=C.G. |last11=Keightley |first11=P.D. |last12=Ko |first12=A. |last13=Lundkvist |first13=Å. |last14=McElhinney |first14=L.M. |last15=Morand |first15=S. |last16=Robins |first16=J. |last17=Russell |first17=J. |last18=Strand |first18=T.M. |last19=Suarez |first19=O. |last20=Yon |first20=L. |last21=Munshi-South |first21=J. |name-list-style=amp |title=Global population divergence and admixture of the brown rat (''Rattus norvegicus'') |journal=Proceedings of the Royal Society B: Biological Sciences |date=2016 |volume=283 |issue=1841 |page=20161762 |doi=10.1098/rspb.2016.1762 |pmid=27798305 |pmc=5095384}}</ref><ref name="IEM"/> some isolated islands,<ref>{{Cite news |url=https://www.bbc.co.uk/news/science-environment-44046472|title=Rodents driven from South Georgia|last=Amos|first=J. |date=2018 |work=BBC News|access-date=2018-05-10}}</ref> the [[Canada|Canadian]] province of [[Alberta]],<ref>{{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 |archive-url= https://web.archive.org/web/20030402054037/http://news.nationalgeographic.com/news/2003/03/0331_030331_rats.html |archive-date= 2 April 2003 |work=National Geographic News |publisher=National Geographic Society |date=31 March 2003 |access-date=30 November 2007}}</ref> and certain conservation areas in New Zealand.<ref>{{cite web |url=http://www.beehive.govt.nz/node/16920|title=beehive.govt.nz – Campbell Island conservation sanctuary rat free|work=beehive.govt.nz}}</ref><ref>Perrow, Martin and A. J. Davy. (2002) ''Handbook of Ecological Restoration.'' Cambridge University Press. pp. 362–363. {{ISBN|0-521-79128-6}}.</ref> Most of Australia apart from the eastern and south-eastern coastal areas does not have reports of substantial rat occurrences.<ref>{{cite web|url=https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:c0f62baa-5df3-4383-a96b-16162e72d1a1|title=Rattus norvegicus (Berkenhout, 1769)|website=Atlas of Living Australia|access-date=6 November 2020}}</ref>

Antarctica is uninhabitable by rats.<ref>{{cite web |url=https://www.britannica.com/animal/brown-rat |title=Brown rat |accessdate=2025-05-13 |publisher=Encyclopædia Britannica, Inc.}}</ref> 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, although they have arrived in many coastal areas by ship. When the occasional rat infestation is found 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 the geographic distance from other rat populations.{{citation needed|date=March 2022}}

=== Rats as invasive species ===
Many parts of the world have been populated by rats secondarily, where rats are now important invasive species that compete with and threaten local fauna. For instance, Norway rats reached North America between 1750 and 1775<ref>{{Cite book|last=Nowak|first=R.M. |title=Walker's Mammals of the World |date=1999 |publisher=Johns Hopkins University Press |isbn=0-8018-5789-9|edition=Sixth |location=Baltimore |oclc=39045218}}</ref> and even in the early 20th century, from 1925 to 1927, 50% of ships entering the port of New York were rat infested.<ref name=":6">{{Cite journal|last=Caten|first=J.L. |date=1968 |title=Human Plague in the United States 1900–1966 |url=http://jama.jamanetwork.com/article.aspx?doi=10.1001/jama.1968.03140320027008|journal=JAMA: The Journal of the American Medical Association |volume=205 |issue=6|pages=333–336|doi=10.1001/jama.1968.03140320027008 |pmid=5694975}}</ref>

====Faroe Islands====
The brown rat was first observed on the [[Faroe Islands]] in 1768. It is thought that the first individuals arrived on the southernmost island, [[Suðuroy]], via the wreck of a Norwegian ship that had stranded on the Scottish [[Isle of Lewis]] on its way from [[Trondheim]] to [[Dublin]]. The drifting wreck, carrying brown rats, drifted northwards until it reached the village of [[Hvalba]]. Dispersion afterwards appears to have been fast, including all of Suðuroy within a year. In 1769, they were observed in [[Tórshavn]] on the southern part of [[Streymoy]], and a decade later, in the villages in the northern part of this island.
From here, they crossed the strait and occupied [[Eysturoy]] during the years 1776 to 1779. In 1779, they reached [[Vagar]]. Whether the rats dispersed from the already established population in Suðuroy, or they were brought to the Faroe Islands with other ships is unknown. The Northern islands were invaded by the brown rat more than 100 years later, after Norwegians built and operated a whaling station in the village of [[Hvannasund]] on [[Borðoy]] from 1898 to 1920. From there, the brown rat spread to the neighbouring islands of [[Viðoy]] and [[Kunoy]].<ref name="Jensen and Magnussen 2015">{{cite journal |last1=Jensen |first1=J.-K. |last2=Magnussen |first2=E. |year=2015 |title=Occurrence of fleas (Siphonaptera) and lice (Phthiraptera) on Brown rats (''Rattus norvegicus'') on the Faroe Islands |journal=Norwegian Journal of Entomology |volume=62 |pages=154–159 |url=http://www.entomologi.no/journals/nje/2017-1/pdf/nje-64-no1-2017-22-27-jensen.pdf}}</ref> A recent genomic analysis reveals three independent introductions of the invasive brown rat to the Faroe Islands.<ref>{{cite journal |last1=Puckett |first1=E.E. |last2=Magnussen |first2=E. |last3=Khlyap |first3=L.A. |last4=Strand |first4=T.M. |last5=Lundkvist |first5=Å. |last6=Munshi-South |first6=J. |name-list-style=amp |title=Genomic analyses reveal three independent introductions of the invasive brown rat (''Rattus norvegicus'') to the Faroe Islands |journal=Heredity |date=2020 |volume=124 |issue=1 |pages=15–27 |doi=10.1038/s41437-019-0255-6 |pmid=31399718 |pmc=6906366 |bibcode=2020Hered.124...15P |s2cid=199512255}}</ref>

Today the brown rat is found on seven of the eighteen Faroese islands, and is common in and around human habitations as well as in the wild. Although the brown rat is now common on all of the largest Faroese islands, only sparse information on the population is available in the literature. An investigation for infection with the [[spirochaete]] ''[[Leptospira interrogans]]'' did not find any infected animals, suggesting that ''Leptospira'' prevalence rates on the Faroe Islands may be among the lowest recorded worldwide.<ref name="Jensen and Magnussen 2015b">{{cite journal|last1=Jensen|first1=P.M. |last2=Magnussen|first2=E. |year=2015 |title=Is it too cold for ''Leptospira {{as written|interr|rogans'' [sic]}} transmission on the Faroese Islands? |name-list-style=amp |journal=Infectious Diseases |volume=48 |issue=2|pages=156–160 |doi=10.3109/23744235.2015.1092579 |pmid=26442766 |s2cid=20516399}}</ref>

====Alaska====
[[Hawadax Island]] (formerly known as Rat Island) in Alaska is thought to have been the first island in the Aleutians to be invaded by Norway rats (the Brown rat) when a Japanese ship  went  aground in the 1780s. They had a devastating effect on the native bird life. An eradication program was started in 2007 and the island was declared rat-free in June 2009.<ref>{{cite web|title=Preliminary ecosystem response following invasive Norway rat eradication on Rat Island, Aleutian Islands, Alaska |publisher=ISSG |url=http://issg.org/pdf/publications/Island_Invasives/pdfHQprint/3Buckelew.pdf |access-date=1 May 2020 |archive-date=25 July 2021 |archive-url=https://web.archive.org/web/20210725065014/http://issg.org/pdf/publications/Island_Invasives/pdfHQprint/3Buckelew.pdf}}</ref>

====Alberta====
[[Alberta]] is the largest rat-free, human-populated area in the world. Rat invasions of Alberta were stopped and rats were eliminated by very aggressive government rat control measures, starting during the 1950s.<ref>{{cite web |url=http://www.issg.org/database/species/distribution_detail.asp?si=159&di=37410&sts=&lang=EN |title=''Rattus norvegicus'' (mammal) – Details of this species in Alberta |publisher=Global Invasive Species Database |access-date=18 October 2014 |archive-date=26 October 2014 |archive-url=https://web.archive.org/web/20141026081724/http://www.issg.org/database/species/distribution_detail.asp?si=159&di=37410&sts=&lang=EN }}</ref><ref>{{cite web |title=Rat Control in Alberta |publisher=Government of Alberta – Department of Agriculture and Rural Development |url=http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex816 |access-date=18 October 2014 |archive-date=26 September 2014 |archive-url=https://web.archive.org/web/20140926013539/http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex816 }}</ref><ref>{{cite web |url=http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3441 |title=The History of Rat Control in Alberta |publisher=Government of Alberta – Department of Agriculture and Rural Development |access-date=18 October 2014 |archive-date=25 September 2014 |archive-url=https://web.archive.org/web/20140925063521/http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3441}}</ref>

The only ''[[Rattus]]'' species that is capable of surviving the [[Alberta#Climate|climate of Alberta]] is the brown rat, which can only survive in the [[Canadian prairies#Prairies|prairie region]] of the province, and even then must overwinter in buildings. Although it is a major agricultural area, Alberta is far from any seaport and only a portion of its eastern boundary with [[Saskatchewan]] provides a favorable entry route for rats. Brown rats cannot survive in the wild [[boreal forest]] to the north, the [[Rocky Mountains]] to the west, nor can they safely cross the semiarid [[High Plains (United States)|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, poisoning, and [[poison gas|gassing]] rats, and bulldozing or burning down some 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.<ref>{{cite web |last=Bourne |first=J. |title=The History of Rat Control in Alberta |work=Agriculture and Food |publisher=Alberta Department of Agriculture |date=2002 |url=http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3441 |access-date=1 December 2007 |archive-date=25 September 2014 |archive-url=https://web.archive.org/web/20140925063521/http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3441
}}</ref>

In the first year of the rat control program, {{cvt|64|t|ST}} of [[arsenic trioxide]] were spread throughout 8,000 buildings on farms along the Saskatchewan border. However, in 1953 the much safer and more effective [[rodenticide]] warfarin was introduced to replace arsenic. Warfarin is an [[anticoagulant]] that was approved as a drug for human use in 1954 and is much safer to use near humans and other large animals than arsenic.<ref name=Holbrook2005>{{cite journal |vauthors=Holbrook AM, Pereira JA, Labiris R, McDonald H, Douketis JD, Crowther M, Wells PS |title=Systematic overview of warfarin and its drug and food interactions | journal=  Archives of Internal Medicine|volume=165 |issue=10 |pages=1095–1106 |date=2005 |pmid=15911722 |doi=10.1001/archinte.165.10.1095 |doi-access=free}}</ref> By 1960, the number of rat infestations in Alberta had dropped to below 200 per year. In 2002, the province finally recorded its first year with zero rat infestations, and from 2002 to 2007 there were only two infestations found.<ref>{{cite encyclopedia
|date=2011 |url=http://www.thecanadianencyclopedia.ca/en/article/rat-control-in-alberta/ |title=Rat Control in Alberta |author1=Bourne, J. |author2=Merril, P. |encyclopedia=[[The Canadian Encyclopedia]] |access-date=30 March 2014}}</ref> After an infestation of rats in the [[Medicine Hat]] landfill was found in 2012, the province's rat-free status was questioned, but provincial government rat control specialists brought in excavating machinery, dug out, shot, and poisoned 147 rats in the landfill, and no live rats were found thereafter.<ref>{{cite web
|url=http://www.producer.com/daily/alberta-eradicates-rat-infestation-near-medicine-hat/ |title=Alberta eradicates rat infestation near Medicine Hat |author=Barb, G. |publisher=The Western Producer |date=2012 |access-date=29 March 2014}}</ref> In 2013, the number of rat infestations in Alberta dropped to zero again. Alberta defines an infestation as two or more rats found at the same location, since a single rat cannot reproduce. About a dozen single rats enter Alberta in an average year and are killed by provincial rat control specialists before they can reproduce.<ref>{{cite web |url=http://www.prairiepost.com/news/alberta/item/5547-alberta-maintains-its-rat-free-status-for-another-year.html |title=Alberta maintains its rat-free status for another year |author=Sanchez, R. |publisher=Prairie Post |date=2014  |access-date=29 March 2014 |archive-url=https://web.archive.org/web/20170622050525/http://www.prairiepost.com/news/alberta/item/5547-alberta-maintains-its-rat-free-status-for-another-year.html |archive-date=22 June 2017 }}</ref>

Only zoos, universities, and research institutes are allowed to keep caged rats in Alberta, and possession of unlicensed rats, including [[fancy rat]]s by anyone else is punishable by a penalty of up to C$5,000 or up to 60 days in jail.<ref>{{cite web |url=http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/acts6008 |title=Agricultural Pests Act and Regulation |author1=Alberta Agriculture |author2=Rural Development |name-list-style=amp |publisher=Government of Alberta |date=2002 |access-date=30 March 2014 |archive-url=https://web.archive.org/web/20140325212034/http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/acts6008 |archive-date=25 March 2014 }}</ref>
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. The Saskatchewan rat control program has considerably reduced the number of rats trying to enter Alberta.<ref>{{cite web |title=Rat Control in Saskatchewan |publisher=Saskatchewan Agriculture, Food and Rural Revitalization |date=2003 |url=http://prep.sarm.ca/+pub/File/PREP/Rat%20Control%20In%20Saskatchewan%28PREP.July2012%29.pdf |access-date=18 October 2018 |archive-date=19 May 2016 |archive-url=https://web.archive.org/web/20160519040357/http://prep.sarm.ca/+pub/File/PREP/Rat%20Control%20In%20Saskatchewan(PREP.July2012).pdf
}}</ref>

====New Zealand====
First arriving before 1800 (perhaps on [[James Cook|James Cook's]] vessels),<ref>{{cite journal |last1=Atkinson |first1=I.A.E.
|year=1973 |title=Spread of the Ship Rat (''Rattus r. rattus'' L.) in New Zealand |journal=[[Journal of the Royal Society of New Zealand]] |volume=2 |issue=3 |pages=457–472 |doi=10.1080/03036758.1973.10421869|bibcode=1973JRSNZ...3..457A
|doi-access=free}}</ref> brown rats pose a serious threat to many of [[New Zealand animals|New Zealand's native wildlife]]. Rat eradication programmes within New Zealand have led to rat-free zones on offshore islands and even on fenced [[Ecological island|"ecological islands"]] on the mainland. Before an eradication effort was launched in 2001, the sub-Antarctic [[Campbell Island, New Zealand|Campbell Island]] had the highest population density of brown rats in the world.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/asia-pacific/2938612.stm |title=NZ routs island rats |date=2003 |work=BBC News |access-date=2 August 2007}}</ref>