Editing Black rat

{{Short description|Species of rodent}}
{{About|the species of rodent}}
{{Use dmy dates|date=July 2021}}
{{Speciesbox
| name = Black rat
| fossil_range = [[Holocene]]
| image = Roofrat Hagenbeck 02.jpg
| image_caption = 
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Kryštufek, B. |author2=Palomo, L. |author3=Hutterer, R. |author4=Mitsainas, G. |author5=Yigit, N. |date=2021 |title=''Rattus rattus'' |volume=2021 |page=e.T19360A192565917 |doi=10.2305/IUCN.UK.2021-1.RLTS.T19360A192565917.en |access-date=19 November 2021}}</ref>
| genus = Rattus
| species = rattus
| authority = ([[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]])
| synonyms = ''Mus rattus'' {{small|Linnaeus,&nbsp;1758}}
| range_map = Rattus rattus.jpg
}}

The '''black rat''' ('''''Rattus rattus'''''), also known as the '''roof rat''', '''ship rat''', or '''house rat''', is a common long-tailed [[rodent]] of the stereotypical rat genus ''[[Rattus]]'', in the subfamily [[Murinae]].<ref name="iucn status 19 November 2021" /> It likely originated in the [[Indian subcontinent]], but is now found worldwide.<ref>{{Cite journal |last1=Baig|first1=M. |last2=Khan|first2=S. |last3=Eager|first3=H. |last4=Atkulwar|first4=A. |last5=Searle|first5=J. B. |name-list-style=amp |date=2019 |title=Phylogeography of the black rat ''Rattus rattus'' in India and the implications for its dispersal history in Eurasia |journal=Biological Invasions |volume=21 |issue=2 |pages=417–433 |doi=10.1007/s10530-018-1830-0|bibcode=2019BiInv..21..417B |s2cid=67790305}}</ref>

The black rat is black to light brown in colour with a lighter underside. It is a generalist [[omnivore]] and a serious [[Pest (organism)|pest]] to farmers because it feeds on a wide range of [[agricultural crops]]. It is sometimes kept as a pet. In parts of [[India]], it is considered sacred and respected in the [[Karni Mata Temple]] in [[Deshnoke]].

==Taxonomy==
''Mus rattus'' was the [[scientific name]] proposed by [[Carl Linnaeus]] in 1758 for the black rat.<ref>{{cite book |last=Linnæus |first=C. |year=1758 |title=Caroli Linnæi Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I |edition=Decima, reformata |location=Holmiae |publisher=Laurentius Salvius |language=la |page=61 |chapter=''Mus rattus'' |chapter-url=https://archive.org/stream/mobot31753000798865#page/61/mode/2up}}</ref>

Three subspecies were once recognized, but today are considered invalid and are now known to be actually [[Morph (zoology)|color morph]]s:{{Citation needed|date=January 2023}}
*''Rattus rattus rattus'' – roof rat
*''Rattus rattus alexandrinus'' – Alexandrine rat
*''Rattus rattus frugivorus'' – fruit rat

==Characteristics==
[[File:Rattus rattus 02 MWNH 748.jpg|frameless|right|alt=Skull]]
[[File:Comparison Black Rat Brown Rat EN.svg|thumb|Comparison of physique with a [[brown rat]] (''Rattus norvegicus'')]]
[[File:Black Rat skeleton.jpg|thumb|[[Museum of Osteology]]|alt=Black rat skeleton ([[Museum of Osteology]])]]
A typical adult black rat is {{cvt|12.75|to|18.25|cm}} long, not including a {{cvt|15|to|22|cm}} tail, and weighs {{cvt|75|to|230|g}}, depending on the subspecies.<ref>{{Cite web |url=http://www.waza.org/en/zoo/visit-the-zoo/rodents-and-hares/rattus-rattus |title=Black rat, House Rat, Roof Rat, Ship Rat (''Rattus rattus'') |website=[[WAZA.org]] |access-date=19 October 2016 |archive-url=https://web.archive.org/web/20161019212834/http://www.waza.org/en/zoo/visit-the-zoo/rodents-and-hares/rattus-rattus |archive-date=19 October 2016 |url-status=dead}}</ref><ref name="adw">{{cite web |url=http://animaldiversity.org/accounts/Rattus_rattus/|title=''Rattus rattus'' – house rat |website=[[Animal Diversity Web]] |last=Gillespie|first=H. |date=2004}}</ref><ref>{{cite book |author1=Schwartz, C. W. |author2=Schwartz, E. R. |year=2001 |title=The Wild Mammals of Missouri |publisher=University of Missouri Press |isbn=978-0-8262-1359-4 |url=https://books.google.com/books?id=uEWl0ZM6DfUC}}</ref><ref>{{cite book |author=Engels, D. W. |year=1999 |title=Classical Cats: The Rise and Fall of the Sacred Cat |location=London and New York |publisher=[[Routledge]] |chapter=Rats |pages=1–17 |isbn=978-0-415-21251-9 |chapter-url=https://books.google.com/books?id=VkqtGl7VN44C&pg=PA16}}</ref> Black rats typically live for about one year in the wild and up to four years in captivity.<ref name=adw/> Despite its name, the black rat exhibits several colour forms. It is usually black to light brown in colour with a lighter underside. In England during the 1920s, several variations were bred and shown alongside domesticated [[brown rat]]s. This included an unusual green-tinted variety.<ref>{{cite book |author=Alderton, D. |year=1996 |title=Rodents of the World |publisher=Diane Publishing Company |isbn=0-8160-3229-7}}</ref>

==Origin==
The black rat was present in prehistoric Europe and in the [[Levant]] during [[postglacial]] periods.<ref name=Rackham>{{cite journal |author=Rackham, J. |title=''Rattus rattus'': The introduction of the black rat into Britain |journal=Antiquity |volume=53 |issue=208 |year=1979 |pmid=11620121|pages=112–120 |doi=10.1017/s0003598x00042319|s2cid=46387899}}</ref> The black rat in the Mediterranean region differs genetically from its South Asian ancestor by having 38 instead of 42 chromosomes.<ref>{{cite journal |last1=Yosida |first1=T. H. |last2=Tsuchiya |first2=K. |last3=Moriwaki |first3=K. |title=Karyotypic differences of black rats, ''Rattus rattus'', collected in various localities of East and Southeast Asia and Oceania |journal=Chromosoma |date=1971 |volume=33 |issue=3 |pages=252–267 |doi=10.1007/BF00284943 |pmid=5088494 |s2cid=12454478}}</ref> Its closest relative is the [[Asian house rat]] (''R. tanezumi'') from Southeast Asia. The two diverged about 120,000 years ago in southwestern Asia. It is unclear how the rat made its way to Europe due to insufficient data, although a land route seems more likely based on the distribution of European haplogroup "A". The black rat spread throughout Europe with the [[Campaign history of the Roman military|Roman conquest]], but declined around the 6th century, possibly due to collapse of the Roman grain trade, climate cooling, or the [[Justinianic Plague]]. A genetically different rat population of haplogroup A replaced the Roman population in the medieval times in Europe.<ref>{{cite journal |last1=Yu |first1=He |last2=Jamieson |first2=Alexandra |last3=Hulme-Beaman |first3=A. |last4=Conroy |first4=C. J. |last5=Knight |first5=B. |last6=Speller |first6=C. |last7=Al-Jarah |first7=H. |last8=Eager |first8=H. |last9=Trinks |first9=A. |last10=Adikari |first10=G. |last11=Baron |first11=H. |last12=Böhlendorf-Arslan |first12=B. |last13=Bohingamuwa |first13=W. |last14=Crowther |first14=A. |last15=Cucchi |first15=T. |last16=Esser |first16=K.|last17=Fleisher |first17=J. |last18=Gidney |first18=L. |last19=Gladilina |first19=E. |last20=Gol’din |first20=Pavel |last21=Goodman |first21=S. M. |last22=Hamilton-Dyer |first22=S. |last23=Helm |first23=R. |last24=Hillman |first24=J. C. |last25=Kallala |first25=N. |last26=Kivikero |first26=H. |last27=Kovács |first27=Zsófia E. |last28=Kunst |first28=G. K. |last29=Kyselý |first29=R. |last30=Linderholm |first30=A. |last31=Maraoui-Telmini |first31=B. |last32=Marković |first32=N. |last33=Morales-Muñiz |first33=A. |last34=Nabais |first34=M. |last35=O’Connor |first35=T. |last36=Oueslati |first36=T. |last37=Quintana Morales |first37=E. M. |last38=Pasda |first38=K. |last39=Perera |first39=J. |last40=Perera |first40=Nimal |last41=Radbauer |first41=S. |last42=Ramon |first42=J. |last43=Rannamäe |first43=E. |last44=Sanmartí Grego |first44=J. |last45=Treasure |first45=E. |last46=Valenzuela-Lamas |first46=S. |last47=van der Jagt |first47=I. |last48=Van Neer |first48=W. |last49=Vigne |first49=J.-D. |last50=Walker |first50=T. |last51=Wynne-Jones |first51=S. |last52=Zeiler |first52=J. |last53=Dobney |first53=K. |last54=Boivin |first54=N. |last55=Searle |first55=J. B. |last56=Krause-Kyora |first56=B. |last57=Krause |first57=J. |last58=Larson |first58=G. |last59=Orton |first59=D. |title=Palaeogenomic analysis of black rat (''Rattus rattus'') reveals multiple European introductions associated with human economic history |journal=Nature Communications |date=2022 |volume=13 |issue=1 |page=2399 |doi=10.1038/s41467-022-30009-z|pmid=35504912 |pmc=9064997 |bibcode=2022NatCo..13.2399Y}}</ref>

It is a resilient [[Vector (epidemiology)|vector]] for many diseases because of its ability to hold so many infectious bacteria in its blood. It was formerly thought to have played a primary role in spreading bacteria contained in fleas on its body, such as the plague bacterium (''[[Yersinia pestis]]'') which is responsible for the [[Plague of Justinian]] and the [[Black Death]].<ref name=McCormick>{{cite journal |author=McCormick, M. |title=Rats, communications, and plague: Toward an ecological history |journal=Journal of Interdisciplinary History |volume=34 |issue=1 |year=2003 |doi=10.1162/002219503322645439 |pages=1–25 |s2cid=128567627 |url=http://dash.harvard.edu/bitstream/handle/1/3208221/McCormick_RatsPlague.pdf}}</ref> However, recent studies have called this theory into question and instead posit humans themselves as the vector, as the movements of the epidemics and the black rat populations do not show historical or geographical correspondence.<ref> url=https://www.history.com/news/rats-didnt-spread-the-black-death-it-was-humans</ref><ref> {{Cite news |date=2018-01-15 |title=Black Death 'spread by humans not rats' |language=en-GB |work=BBC News |url=https://www.bbc.com/news/science-environment-42690577 |access-date=2023-03-06}}</ref> A study published in 2015 indicates that other Asiatic rodents served as plague reservoirs, from which infections spread as far west as Europe via trade routes, both overland and maritime. Although the black rat was certainly a plague vector in European ports, the spread of the plague beyond areas colonized by rats suggests that the plague was also circulated by humans after reaching Europe.<ref>{{cite journal |journal=Proceedings of the National Academy of Sciences of the United States of America |date=2015 |last1=Schmid, B.V. |last2=Büntgen, U. |last3=Easterday, W.R. |last4=Ginzler, C. |last5=Walløe, L.| last6=Bramanti, B. |last7=Stenseth, N.C. |title=Climate-driven introduction of the Black Death and successive plague reintroductions into Europe |doi=10.1073/pnas.1412887112 |pmid=25713390 |volume=112 |issue=10 |pages=3020–3025 |pmc=4364181 |bibcode=2015PNAS..112.3020S|doi-access=free}}</ref>

==Distribution and habitat==
The black rat originated in India and Southeast Asia, and spread to the [[Near East]] and [[Egypt]], and then throughout the [[Roman Empire]], reaching Great Britain as early as the 1st century AD.<ref>{{cite book|author=Donald W. Engels|title=Classical Cats: The Rise and Fall of the Sacred Cat|publisher=[[Routledge]]|year=1999|isbn=978-0-415-21251-9|url=https://books.google.com/books?id=VkqtGl7VN44C&pg=PA111|page=111}}</ref> [[European ethnic groups|Europeans]] subsequently spread it throughout the world. The black rat is again largely confined to warmer areas, having been supplanted by the [[brown rat]] (''Rattus norvegicus'') in cooler regions and urban areas. In addition to the brown rat 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 [[Extreme weather|weather extremes]].<ref>{{cite web|author=Teisha Rowland|url=http://www.independent.com/news/2009/dec/04/ancient-origins-modern-pet-rats/?print|title=Ancient Origins of Pet Rats|archive-url=https://web.archive.org/web/20150924200319/http://www.independent.com/news/2009/dec/04/ancient-origins-modern-pet-rats/?print|archive-date=24 September 2015|website=[[Santa Barbara Independent]]|date=4 December 2009}}</ref>

Black rat populations can increase exponentially under certain circumstances, perhaps having to do with the timing of the fruiting of the [[bamboo]] plant, and cause devastation to the plantings of subsistence farmers; this phenomenon is known as ''[[mautam]]'' in parts of [[India]].<ref>{{cite episode|title=Nova: Rat Attack|network=[[PBS]]|series=[[Nova (American TV program)|Nova]]|date=7 April 2010}}</ref>

Black rats are thought to have arrived in Australia with the [[First Fleet]], and subsequently spread to many coastal regions in the country.<ref>{{cite web|title=Animal Species: Black Rat |last=Evans|first=Ondine|date=1 April 2010|work=Australian Museum website|publisher=Australian Museum|location=Sydney, Australia |url=https://australian.museum/learn/animals/mammals/black-rat/ |access-date=31 December 2010}}</ref>

Black rats adapt to a wide range of habitats. In urban areas they are found around warehouses, residential buildings, and other human settlements. They are also found in agricultural areas, such as in barns and crop fields.<ref>{{cite web |title=Black Rats|last1=Tech |first1=Texas |url=https://www.depts.ttu.edu/nsrl/mammals-of-texas-online-edition/Accounts_Introduced_Rodentia/Rattus_rattus.php |website=Natural Science Research Laboratory |access-date=15 February 2024}}</ref> In urban areas, they prefer to live in dry upper levels of buildings, so they are commonly found in wall cavities and false ceilings. In the wild, black rats live in cliffs, rocks, the ground, and trees.<ref>{{cite web |title=Rattus Rattus |url=https://www.pestsolutions.co.uk/pest-library/rodent-pest-species/black-rats-rattus-rattus |website=Pest Solutions |date=22 November 2022 |access-date=15 February 2024}}</ref> They are great climbers and prefer to live in palms and trees, such as pine trees. Their nests are typically spherical and made of shredded material, including sticks, leaves, other vegetation and cloth. In the absence of palms or trees, they can burrow into the ground.<ref name = black>{{cite web |url=http://www.the-piedpiper.co.uk/th1b.htm|title= The Black Rat (''Rattus Rattus'')|author=Bennet, Stuart M. |work=The Pied Piper|access-date=22 April 2011}}</ref> Black rats are also found around fences, ponds, riverbanks, streams, and reservoirs.<ref name = roof >{{cite web |title=Roof Rats|author=Marsh, Rex E.|year=1994 |work=Internet Center for Wildlife Damage Management |publisher=Prevention and Control of Wildlife Damage |url=http://icwdm.org/handbook/rodents/RoofRats.asp|access-date=22 April 2011|url-status=dead|archive-url=https://web.archive.org/web/20110521025949/http://icwdm.org/handbook/rodents/RoofRats.asp|archive-date=21 May 2011}}</ref>

==Behaviour and ecology==
It is thought that male and female rats have similarly sized [[Home range|home ranges]] during the winter, but male rats increase the size of their home range during the breeding season. Along with differing between rats of different sex, home range also differs depending on the type of forest in which the black rat inhabits. For example, home ranges in the [[Nothofagus|southern beech forests]] of the [[South Island]], New Zealand appear to be much larger than the non-beech forests of the [[North Island]]. Due to the limited number of rats that are studied in home range studies, the estimated sizes of rat home ranges in different rat demographic groups are inconclusive.

===Diet and foraging===
[[File:Rattus rattus 01.JPG|thumb|Black rat eating grain]]
Black rats are considered [[omnivore]]s and eat a wide range of foods, including seeds, fruit, stems, leaves, fungi, and a variety of invertebrates and vertebrates. They are [[generalist and specialist species|generalists]], and thus not very specific in their food preferences, which is indicated by their tendency to feed on any meal provided for cows, swine, chickens, cats and dogs.<ref name=roof/> They are similar to the tree squirrel in their preference of fruits and nuts. They eat about {{cvt|15|g}} per day and drink about {{cvt|15|ml}} per day.<ref name=black/> Their diet is high in water content.<ref name=roof/> They are a threat to many natural habitats because they feed on birds and insects. They are also a threat to many farmers, since they feed on a variety of agricultural-based crops, such as cereals, sugar cane, coconuts, cocoa, oranges, and coffee beans.<ref name=rattus>{{cite web |title=''Rattus rattus'' – Roof rat |url=https://www.pestsolutions.co.uk/pest-library/rodent-pest-species/black-rats-rattus-rattus |work=Pest Solutions |date=22 November 2022 |access-date=15 February 2024}}</ref>

The black rat displays flexibility in its foraging behaviour. It is a predatory species and adapts to different micro-habitats. It often meets and forages together in close proximity within and between sexes.<ref name=Dowding/> It tends to forage after sunset. If the food cannot be eaten quickly, it searches for a place to carry and hoard to eat at a later time.<ref name=roof/> Although it eats a broad range of foods, it is a highly selective feeder; only a restricted selection of the foods is dominating.<ref name=Clark>{{cite journal |author=Clark, D. A. |title=Foraging behavior of vertebrate omnivore (''Rattus rattus''): Meal structure, sampling, and diet breadth |journal=Ecology |volume=63 |issue=3 |year=1982 |doi=10.2307/1936797 |pages= 763–772 |jstor=1936797|bibcode=1982Ecol...63..763C }}</ref> When offered a wide diversity of foods, it eats only a small sample of each. This allows it to monitor the quality of foods that are present year round, such as leaves, as well as seasonal foods, such as herbs and insects. This method of operating on a set of foraging standards ultimately determines the final composition of its meals. Also, by sampling the available food in an area, it maintains a dynamic food supply, balance its nutrient intake, and avoids intoxication by secondary compounds.<ref name=Clark/>

===Nesting behaviour===
Through the usage of tracking devices such as radio transmitters, rats have been found to occupy dens located in trees, as well as on the ground. In Puketi Forest in the [[Northland Region]] of New Zealand, rats have been found to form dens together. Rats appear to den and forage in separate areas in their home range depending on the availability of food resources.<ref name=Dowding>{{cite journal |author1=Dowding, J.E. |author2=Murphy, E.C. |name-list-style=amp |title=Ecology of Ship Rats (''Rattus rattus'') in a Kauri (''Agathis australis'') Forest in Northland, New Zealand |journal=New Zealand Journal of Ecology |volume=18 |issue=1 |year=1994 |pages=19–28 |url=https://newzealandecology.org/nzje/1947.pdf}}</ref> Research shows that, in New South Wales, the black rat prefers to inhabit lower leaf litter of forest habitat. There is also an apparent correlation between the canopy height and logs and the presence of black rats. This correlation may be a result of the distribution of the abundance of prey as well as available refuges for rats to avoid predators. As found in [[North Head, New South Wales]], there is positive correlation between rat abundance, leaf litter cover, canopy height, and litter depth. All other habitat variables showed little to no correlation.<ref name= Cox>{{cite journal |author1=Cox, M.P.G. |author2=Dickman, C.R. |author3=Cox, W.G. |name-list-style=amp |title=Use of habitat by the black rat (''Rattus rattus'') at North Head, New South Wales: an observational and experimental study |journal=Austral Ecology |volume=25 |issue=4 |year=2000 |doi=10.1046/j.1442-9993.2000.01050.x |pages=375–385|bibcode=2000AusEc..25..375C }}</ref> While this species' relative, the brown (Norway) rat, prefers to nest near the ground of a building the black rat will prefer the upper floors and roof. Because of this habit they have been given the common name roof rat.

===Diseases===
Black rats (or their [[ectoparasite]]s<ref>{{cite journal|author=Hafidzi, M.N. |author2=Zakry, F.A.A. |author3=Saadiah, A. |name-list-style=amp |year=2007 |title=Ectoparasites of ''Rattus'' sp. from Petaling Jaya, Selangor, Malaysia |journal= Pertanika Journal of Tropical Agricultural Science |volume=30|issue=1 |pages=11–16}}</ref>) can carry a number of pathogens,<ref>{{cite journal |author=Meerburg, B.G. |author2=Singleton, G.R. |author3=Kijlstra A. |title=Rodent-borne diseases and their risks for public health|journal=Crit Rev Microbiology |volume=35 |issue=3 |pages=221–270 |year=2009 |doi=10.1080/10408410902989837|pmid=19548807|s2cid=205694138}}</ref> of which [[bubonic plague]] (via the [[Oriental rat flea]]), [[typhus]], [[Weil's disease]], [[toxoplasmosis]] and [[trichinosis]] are the best known. It has been hypothesized that the displacement of black rats by [[brown rat]]s led to the decline of the [[Black Death]].<ref>Last, John M. [http://www.enotes.com/public-health-encyclopedia/black-death "Black Death"], ''Encyclopedia of Public Health'', [[eNotes]] website. Retrieved 31 December 2010.</ref><ref>Barnes, Ethne (2007). ''Diseases and Human Evolution'', [[University of New Mexico Press]], {{ISBN|978-0-8263-3066-6}}, [https://books.google.com/books?id=wnlB7EMtqFYC&pg=PA247 p. 247].</ref> This theory has, however, been deprecated, as the dates of these displacements do not match the increases and decreases in plague outbreaks.<ref>Bollet, Alfred J. (2004). ''Plagues & Poxes: The Impact of Human History on Epidemic Disease'', [[Demos Medical Publishing]], 2004, {{ISBN|978-1-888799-79-8}}, [https://books.google.com/books?id=bHIj5PJdZbkC&pg=PA23 p. 23]</ref><ref>Carrick, Tracy Hamler; Carrick, Nancy and Finsen, Lawrence (1997). ''The Persuasive Pen: An Integrated Approach to Reasoning and Writing'', [[Jones and Bartlett Learning]], 1997, {{ISBN|978-0-7637-0234-2}}, [https://books.google.com/books?id=6miPAUtQUO4C&pg=PA162 p. 162].</ref><ref>Hays, J. N. (2005). ''Epidemics and Pandemics: Their Impacts on Human History'', [[ABC-CLIO]], {{ISBN|978-1-85109-658-9}}, [https://archive.org/details/epidemicspandemi0000hays/page/64 p. 64].</ref>

Rats serve as outstanding vectors for transmittance of diseases because they can carry bacteria and viruses in their systems. A number of bacterial diseases are common to rats, and these include ''[[Streptococcus pneumoniae]]'', ''[[Corynebacterium kutsheri]],'' ''[[Bacillus piliformis]]'', ''[[Pasteurella pneumotropica]]'', and ''[[Streptobacillus moniliformis]]'', to name a few. All of these bacteria are disease causing agents in humans. In some cases, these diseases are incurable.<ref name=bacterial>{{cite web |author=Boschert, K. |date=1991 |url=http://netvet.wustl.edu/species/rats/ratbact.txt|archive-url=https://web.archive.org/web/19961018162831/http://netvet.wustl.edu/species/rats/ratbact.txt|url-status=dead|archive-date=18 October 1996|title=Rat Bacterial Diseases|work=Net Vet and the Electronic Zoo|access-date=22 April 2011}}</ref>

===Predators===
The black rat is prey to cats and owls in domestic settings. In less urban settings, rats are preyed on by weasels, foxes and coyotes. These predators have little effect on the control of the black rat population because black rats are agile and fast climbers. In addition to agility, the black rat also uses its keen sense of hearing to detect danger and quickly evade mammalian and avian predators.<ref name=roof/>

==As an invasive species==

===Damage caused===
After ''Rattus rattus'' was introduced into the northern islands of New Zealand, they fed on the seedlings, adversely affecting the ecology of the islands. Even after eradication of ''R. rattus'', the negative effects may take decades to reverse. When consuming these seabirds and seabird eggs, these rats reduce the pH of the soil. This harms plant species by reducing nutrient availability in soil, thus decreasing the probability of seed germination. For example, research conducted by Hoffman et al. indicates a large impact on 16 indigenous plant species directly preyed on by ''R. rattus''. These plants displayed a negative correlation in germination and growth in the presence of black rats.<ref name= Grant-Hoffman>{{cite journal |author1=Grant-Hoffman, MN |author2=Mulder, CP |author3=Belingham, PJ |title=Invasive Rats Alter Woody Seedling Composition on Seabird-dominated Islands in New Zealand|journal=Oecologia|volume=163|issue=2|year=2009|doi=10.1007/s00442-009-1523-6 |issn=1442-9993|pmid=20033216  |pages=449–60|s2cid=25286223 }}</ref>
Rats prefer to forage in forest habitats. In the [[Ogasawara islands]], they prey on the indigenous snails and seedlings. Snails that inhabit the leaf litter of these islands showed a significant decline in population on the introduction of ''Rattus rattus''. The black rat shows a preference for snails with larger shells (greater than 10&nbsp;mm), and this led to a great decline in the population of snails with larger shells. A lack of prey refuges makes it more difficult for the snail to avoid the rat.<ref name=Chiba>{{cite journal |author=Chiba, S.|title=Invasive Rats Alter Assemblage Characteristics of Land Snails in the Ogasawara Islands|journal=Biological Conservation|volume=143|issue=6|year=2010|doi=10.1016/j.biocon.2010.03.040 |pages=1558–63|bibcode=2010BCons.143.1558C }}</ref>

===Complex pest===
The black rat is a complex pest, defined as one that influences the environment in both harmful and beneficial ways. In many cases, after the black rat is introduced into a new area, the population size of some native species declines or goes extinct. This is because the black rat is a good generalist with a wide dietary [[Ecological niche|niche]] and a preference for complex habitats; this causes strong competition for resources among small animals. This has led to the black rat completely displacing many native species in Madagascar, the Galapagos, and the Florida Keys. In a study by Stokes ''et al.'', habitats suitable for the native bush rat, ''[[Rattus fuscipes]]'', of Australia are often invaded by the black rat and are eventually occupied by only the black rat. When the abundances of these two rat species were compared in different [[micro-habitats]], both were found to be affected by micro-habitat disturbances, but the black rat was most abundant in areas of high disturbance; this indicates it has a better dispersal ability.<ref name=Vernes>{{cite journal |author1=Vernes, K |author2=Mcgrath, K | title=Are Introduced Black Rats (''Rattus rattus'') a Functional Replacement for Mycophagous Native Rodents in Fragmented Forests? | journal=Fungal Ecology | volume=2 |issue=3| year=2009 |doi=10.1016/j.funeco.2009.03.001 | pages=145–48|bibcode=2009FunE....2..145V }}</ref>

Despite the black rat's tendency to displace native species, it can also aid in increasing species population numbers and maintaining species diversity. The bush rat, a common vector for spore dispersal of [[truffles]], has been extirpated from many micro-habitats of Australia. In the absence of a vector, the diversity of truffle species would be expected to decline. In a study in New South Wales, Australia it was found that, although the bush rat consumes a diversity of truffle species, the black rat consumes as much of the diverse fungi as the natives and is an effective vector for spore dispersal. Since the black rat now occupies many of the micro-habitats that were previously inhabited by the bush rat, the black rat plays an important ecological role in the dispersal of fungal spores. By eradicating the black rat populations in Australia, the diversity of fungi would decline, potentially doing more harm than good.<ref name=Vernes/>

===Control methods===
Large-scale rat control programs have been taken to maintain a steady level of the invasive predators in order to conserve the native species in New Zealand such as [[kokako]] and [[Yellowhead (bird)|mohua]].<ref name = Pryde>{{cite journal |author1=Pryde, M. |author2=Dilks, P. |author3=Fraser, I. |title=The home range of ship rats (''Rattus rattus'') in beech forest in the Eglinton Valley, Fiordland, New Zealand: a pilot study|journal=New Zealand Journal of Zoology |volume=32 |issue=3 |year=2005 |pages=139–142 |doi=10.1080/03014223.2005.9518406 |s2cid=84513492}}</ref> Pesticides, such as [[pindone]] and 1080 ([[sodium fluoroacetate]]), are commonly distributed via aerial spray by helicopter as a method of mass control on islands infested with invasive rat populations. Bait, such as [[brodifacoum]], is also used along with coloured dyes (used to deter birds from eating the baits) in order to kill and identify rats for experimental and tracking purposes. Another method to track rats is the use of wired cage traps, which are used along with bait, such as rolled oats and peanut butter, to tag and track rats to determine population sizes through methods like mark-recapture and radio-tracking.<ref name=Dowding/> Tracking tunnels (coreflute tunnels containing an inked card) are also commonly used monitoring devices, as are chew-cards containing peanut butter.<ref>{{Cite journal |last1=Jackson |first1=M. |last2=Hartley |first2=S. |last3=Linklater |first3=W. |date=2016 |title=Better food-based baits and lures for invasive rats Rattus spp. and the brushtail possum ''Trichosurus vulpecula'': a bioassay on wild, free-ranging animals|journal=Journal of Pest Science |volume=89 |issue=2 |pages=479–488 |doi=10.1007/s10340-015-0693-8 |s2cid=13095387}}</ref> Poison control methods are effective in reducing rat populations to nonthreatening sizes, but rat populations often rebound to normal size within months. Besides their highly adaptive foraging behavior and fast reproduction, the exact mechanisms for their rebound is unclear and are still being studied.<ref name=Innes>{{cite journal|author1=Innes, J. |author2=Warburton, B. |author3=Williams, D. |title=Large-Scale Poisoning of Ship Rats (''Rattus rattus'') in Indigenous Forests of the North Island, New Zealand|journal=New Zealand Journal of Ecology |volume=19 |issue=1 |pages=5–17 |year=1995 |url=http://www.nzes.org.nz/nzje/free_issues/NZJEcol19_1_5.pdf |access-date=22 April 2011|archive-date=27 September 2011|archive-url=https://web.archive.org/web/20110927230417/http://www.nzes.org.nz/nzje/free_issues/NZJEcol19_1_5.pdf|url-status=dead}}</ref>

In 2010, the Sociedad Ornitológica Puertorriqueña (Puerto Rican Bird Society) and the [[Club Náutico de Ponce|Ponce Yacht and Fishing Club]] launched a campaign to eradicate the black rat from the [[Isla de Ratones (Ponce, Puerto Rico)|Isla Ratones]] (Mice Island) and [[Cardona (Ponce)|Isla Cardona]] (Cardona Island) islands off the municipality of [[Ponce, Puerto Rico]].<ref>Wege, David (4 August 2010) [http://www.birdlife.org/community/2010/08/restauran-habitat-del-lagartijo-del-seco-anolis-cooki-en-la-isla-de-cardona-y-cayo-ratones/ Restauran hábitat del lagartijo del seco Anolis cooki en la Isla de Cardona y Cayo Ratones] {{Webarchive|url=https://web.archive.org/web/20110814173530/http://www.birdlife.org/community/2010/08/restauran-habitat-del-lagartijo-del-seco-anolis-cooki-en-la-isla-de-cardona-y-cayo-ratones/ |date=14 August 2011 }}. birdlife.org.</ref>

==Decline in population==
Eradication projects have eliminated black rats from [[Lundy]] in the [[Bristol Channel]] (2006)<ref>{{Cite journal |last=Lock |first=J. |date=2006 |title=Eradication of brown rats Rattus norvegicus and black rats Rattus rattus to restore breeding seabird populations on Lundy Island, Devon, England |url=https://www.conservationevidence.com/reference/download/2241 |journal=Conservation Evidence |pages=111–113}}</ref> and from the [[Shiant Islands]] in the [[Outer Hebrides]] (2016).<ref>{{Cite book |url=https://portals.iucn.org/library/node/48358 |title=Island invasives : scaling up to meet the challenge |date=2019 |publisher=IUCN |isbn=978-2-8317-1962-7 |editor-first= |pages=138–146 |language=en |chapter=Scaling down (cliff s) to meet the challenge: the Shiants’ black rat eradication |doi=10.2305/iucn.ch.2019.ssc-op.62.en |hdl=1893/29131 |editor-last2= Clout|editor-first2= M.N.|editor-last3= Martin|editor-first3= A.R.|editor-last4= Russell|editor-first4= J.C.|editor-last5= West|editor-first5=C.J. |editor-last1=Veitch |editor-first1=C.R. }}</ref> Populations probably survive on other islands (e.g. [[Inchcolm]]) and in localised areas of the British mainland.<ref>{{Cite web|url=https://www.scotsman.com/heritage-and-retro/heritage/revealed-historic-scottish-island-home-black-rats-2463871|title = Revealed: Historic Scottish island home to black rats| date=31 December 2018 }}</ref> Recent National Biodiversity Network data show populations around the U.K., particularly in ports and port towns.<ref>{{Cite web|url=https://data.nbn.org.uk/Taxa/NHMSYS0000080213|title=NBN Gateway – Taxon |website=data.nbn.org.uk|access-date=2016-08-11}}</ref>

==See also==
* [[Karni Mata Temple]], Deshnoke, Rajasthan, India.
* [[Polynesian rat]]
* [[Urban plague]]

==References==
{{Reflist}}

==Further reading==
* [[List of books and articles about rats]]

==External links==
{{Commons category|Rattus rattus}}
*[https://web.archive.org/web/20080430202159/http://www.arkive.org/species/ARK/mammals/Rattus_rattus/ Photos and video] at ARKive

{{Murinae (Rattus)}}

{{Taxonbar|from=Q106133}}
{{Authority control}}

[[Category:Rattus]]
[[Category:Rodents of Asia]]
[[Category:Rodents of Europe]]
[[Category:Mammals of Azerbaijan]]
[[Category:Mammals of Nepal]]
[[Category:Stored-product pests]]
[[Category:Mammals described in 1758]]
[[Category:Taxa named by Carl Linnaeus]]
[[Category:Rodents of Borneo]]