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B r o w n R a t , Rattus norvegicus Overview . Short description of Rattus norvegicus, B r o w n R a t The large size and long, thin, almost hairless tail distinguish rats from other grey-brown rodents. Confusion is possible with water vole, but these are smaller and darker brown, with shorter ears, a furry tail and a blunter snout. The ship rat is slimmer than the brown rat, with relatively longer ears and a tail that is longer than its body. The brown rat's tail is shorter than the body length and has a paler underside. Description of Rattus norvegicus, Brown Rat status in GB Author's name: The brown rat is very abundant in GB and almost ubiquitous in both urban and rural environments. The GB pre-breeding population was estimated to be at least 6.8 million animals in 1995. John Marchant Last updated: H a b i t a t s u m m a r y : Rattus norvegicus, B r o w n R a t March 12th, 2012 Brown rats are found in a very wide range of habitat types, typically in association with humans. We try to keep these factsheets up to date, however if you notice any issues please contact us Overview table Environment: Terrestrial Species status: Non-Native Native range: Middle Asia, China, Kazan-retto, Nansei-shoto, Ogasawara-shoto, Russia Central, Russia East, Russia North, Russia Northwest, Russia South Functional type: Omnivore Status in England: Non-Native Status in Scotland: Non-Native Status in Wales: Non-Native Location of first record: first record is unknown (ancient) Date of first record: 1720 Invasion history: Rattus norvegicus, B r o w n R a t Origin The species is believed to have originated on the steppes of central Asia and to have reached eastern Europe from the east in the early 1700s, possibly by natural dispersal. First Record The first brown rats in GB are reported to have arrived at English ports around 1728–29. Pathway and Method Brown rats can thrive on ships at sea and come ashore in ports or through shipwrecks. Species Status The brown rat is highly invasive and is regarded as a serious pest almost worldwide. Ecology & Habitat: Rattus norvegicus, B r o w n R a t Dispersal Mechanisms Brown rats have spread around the world through their readiness to travel in ships. They swim well and can disperse naturally to and from offshore islands. Reproduction The species breeds prolifically throughout the year. As many as 13 litters can be raised in a year, each of up to nine young, and females mature sexually after just 8–12 weeks. Known Predators/Herbivores Young rats fall prey to a variety of avian and mammalian predators, including owls, domestic cats and dogs, and foxes. Fully grown animals can escape predation through their large size and aggressiveness. Resistant Stages None known. Habitat Occupied in GB Brown rats are typically commensal with man in a wide range of urban and agricultural habitats. They are abundant in sewers, refuse tips, warehouses and storage barns, along water courses, and in hedge-bottoms on farmland. Populations also occur independently of humans in more natural habitats, such as saltmarshes. Distribution: Rattus norvegicus, B r o w n R a t Brown rats occur almost throughout GB, being absent only from exposed montane areas and from some smaller offshore islands. The species has spread almost worldwide, with the exception of some tropical and subtropical areas. I m p a c t s : Rattus norvegicus, B r o w n R a t Environmental Impact The abundance and ubiquity of brown rats mean they have considerable impact on ecosystems, for example as predator and prey, and as competitors for food, shelter and nest sites. The arrival of brown rats displaced ship rats, which had occupied a similar niche, from mainland GB. Their presence on islands can lead to extinction of seabird colonies. Worldwide, rats have contributed to many extinctions or near-extinctions of island endemic species. Health and Social Impact Brown rats can spread a number of diseases to humans through their bites and droppings, including leptospirosis (Weil's disease), and their ticks can carry Lyme disease. Weil's disease is a significant public health hazard to anyone entering fresh water in rat-infested areas, the causative bacteria L ( eptospira) being able to infect humans through broken skin. Inside buildings, rats can cause considerable nuisance through fouling surfaces and water tanks, gnawing timbers and wiring, and through their noise and aggression. Economic Impact Brown rats have major economic impacts. They consume and contaminate human food, both as growing crops and in storage, and damage grain storage bags. In buildings, they gnaw access holes in woodwork and pose electrical hazard by gnawing into cables and insulation. References & Links: Rattus norvegicus, B r o w n R a t Identification Harris, S. & Yalden, D.W. (2008) Mammals of the British Isles: Handbook. Fourth edition. The Mammal Society, Southampton. Biology, ecology, spread, vectors Clark, M. & Summers, S. (1980) Seasonal population movements of brown rats and house mice in Hertfordshire. Transactions of the Hertfordshire Natural History Society, 2 8, 17–19. Hilton, A.C., Willis, R.J. & Hickie, S.J. (2002) Isolation of Salmonella from urban wild brown rats (Rattus norvegicus) in the West Midlands, UK. International Journal of Environmental Health Research, 1 2 , 163–168. Management and impact Abdelkrim, J., Pascal, M., Calmet, C. & Samadi, S. (2005) Importance of assessing population genetic structure before eradication of invasive species: examples from insular Norway rat populations. Conservation Biology, 1 9, 1509–1518. Drummond, D.C. (1985) Developing and monitoring urban rodent control programmes. Acta Zoologica Fennica, 1 7 3, 145–148. Langton, S.D., Cowan, D.P. & Meyer, A.N. (2001) The occurrence of commensal rodents in dwellings as revealed by the 1996 English house condition survey. Journal of Applied Ecology, 3 8, 699–709. Lorvelec, O. & Pascal, M. (2005) French alien mammal eradication attempts and their consequences on the native fauna and flora. Biological Invasions, 7 , 135–140. General Harris, S. & Yalden, D.W. (2008) Mammals of the British Isles: Handbook. Fourth edition. The Mammal Society, Southampton. Lever, C. (2009) The Naturalized Animals of Britain and Ireland. New Holland Publishers, London. Twigg, G. (1975) The brown rat. David & Charles, Newton Abbot.