Galapagos Species Checklist

Rattus rattus Linnaeus, 1758

Rata negra, rata de barco, rata de tejado, rata común, pericote, rata de buque, Black Rat, Old World rats

Photo: Heidi Snell, CDF.
Photo: Heidi Snell, CDF.

It is a thin rodent. Its body measures 16 to 22 cm. long. Their average weight is 150 to 230 g. The coat is gray - black or gray, almost black back towards the tail and light gray, pale yellow or white on the underside. The tail is longer than the body and it measures from 17-24 cm. The tail is hairless but covered with scales that form rings. The ears are large, wide and thin; and the snout is pointy. They have a short life span from 3 to 5 years.

Taxonomy

Domain
Eukaryota

Kingdom
Animalia

Phylum
Chordata

Class
Mammalia

Order
Rodentia

Family
Muridae

Genus
Rattus

Species
rattus

Taxon category: Accepted

Ecology

Preference for an altitude zone in Galapagos: Dry zone - humid zone

Habitat preferences: : In Galapagos, R. rattus occupies vegetated habitats, from arid thorn scrubs to humid forests.

Feeding type: Polyphagous

Feeding preferences: As generalists, black rats exhibit a great deal of flexibility in their foraging behavior. Their diet is varied and includes arthropods, snails, worms, seeds, fruits, stems, rhizomes, leaves, fungi, terrestrial birds, seabird chicks and eggs of tortoises and turtles, and juvenile turtles. They prefer food with a high protein and nutritional content.

Trophic role: Omnivorous

Persistence mechanisms: They are predators adapted to different micro habitats. Their ability to forage selecting the most nutritious food makes them successful in the places where they settle. The reproductive capacity helps in their successful colonization, under favorable conditions, the female produces up to five litters per year, every six to twelve pups. Being so large crowds, they displace other species found in the areas they invade. They are very agile, with a keen sense of hearing, they can sense danger and evade predators easily

Reproduction mode: Exclusively sexual

Reproductive biology: Females are poliestric, their sexual cycles last four to six days, experiencing periods of heat from nine to twenty hours, and the gestation period is 21-23 days. The female produces up to five litters per year from six to twelve individuals. In Galapagos, the reproduction is seasonal and occurs in the warm season (January to June). Females can get pregnant within a period of 24 hours postpartum. When the young are born their eyes and ears are not open, the body lacks hair, their limbs are small. Pups move by crawling. The newborn ears open a week after birth and their eyes after two weeks, then they begin to eat solid food taken to them by the mother. The young go through a learning phasein close proximity of the mother at the age of three weeks are able to live without milk and begin to venture and subsequently become very active. They relate through sounds, little by little they become more independent from the parents until they reach sexual maturity and adopt an independent behavior.

Distribution origin: A native species to India, Rattus rattus has spread worldwide, on continental landmasses as well as islands and islets, in urban and rural areas as well as natural areas.

Natural enemies: Often, black rats fall prey to cats (Felis catus). In the wild, these rats are prey to weasels, foxes and various birds of prey. However, predation by these has little effect on numbers at the population level. Black rats are agile and fast climbers, managing to escape easily. They use their acute sense of hearing to avoid predators. In the Galapagos Islands they are prey to short-eared Owl (Asio flammeus), barn owl (Tyto alba), occasionally Galapagos hawks (Buteo galapagoensis). There is little information indicating that Feral cats (Felis catus) consume rats predominantly in the Galapagos islands.

Associated species in Galapagos: Humans

Economic Use: The albino or white rats are reared as pets in some countries, these do not have a high economic value, however they are sold in pet stores. White rats are also bred in great numbers to suoply the demand for research by labs, pharmaceutical industries and universities. In Australia R. rattus has been used in the work of truffle spore dispersal after the extinction of the rat bush (in English is Bush rat) (Rattus fuscipes), thus preventing the species of truffles from reducing drastically. For this reason it is considered that the total eradication of black rats could be harmful in this town, as the diversity of fungi would be reduced, and this would harm the local economy.

Disease vector: Rats are vectors for disease, they can carry bacteria and viruses in their body. The most common bacterial diseases in rats include Streptococcus pneumoniae, Corynebacterium kutsheri, Bacillus piliformis, Pasteurella pneumotropica and Streptobacillus moniliformis. They have caused pandemics such as bubonic plague transmitted through rat flea, and typhus and epidemics such as Weil's disease, toxoplasmosis and trichinosis, among the best known. All these bacteria and viruses cause disease in humans with some incurable and fatal.

Introduction

Introduction route: Accidentally introduced

Invasion risk score: High risk

Impact in Galapagos: In the Galapagos these rodents are responsible for the direct predation of eggs and hatchlings of tortoises on Pinzon Island (Chelonoidis ephippium), which for decades has restricted the recruitment of juveniles in the wild. In less intensity, they have attacked other species of tortoises in the islands where R. rattus occurs. It also feeds on eggs and juveniles of land and marine iguanas, land and marine birds, small reptiles, small invertebrates, mollusks and crustaceans, as well as seeds, fruits, buds, rhizomes, stems, leaves, grains. Many of these prey species have come to collapse, thereby causing other native and endemic species to move elsewhere or come to extinction as happened with the endemic rats that died on islands like Isabela, Santa Cruz, San Cristobal and Baltra.

Impact elsewhere: They cause losses in agriculture, destroy crops on a large scale. When they have availability of large amount of food, they gnaw on and destroy everything they find, even if they will consume it, they fill everything with urine and feces to damage food. The black rat is related to the disappearance of birds on islands, as well as reptiles, small mammals, amphibians, invertebrates and plants. They are a potential threat to the human species, due to the amount of viruses and bacteria that they can pass in their feces, urine or direct contact, or bite.

Control History in Galapagos: Since 1980, there have been made ten attempts to eradicate rats in the Galapagos Islands, and only five have been successful. In the initial phases of control, rats chronic rodenticide called Racumin 57 was used; these days an anticoagulant rodenticide called Brodifacoum is used. Weather conditions in the Galapagos Islands have a determining influence on the success and failure of eradication work. The Galapagos National Park, takes control campaigns in the Archipelago, in places where there is greater sensitivity of native species to these predators. Sites like Pinzon Island, Playa Tortuga Negra, Caleta Black, The Marielas, Punta Pitt, Gardner Islet Floreana island's Tintoreras, Seymour Island, among others. These sites are home to endemic species (Chelonoidis sp., Mangrove finch, Galapagos penguin, Galápagos petrel, Floreana mockingbird, Conolophus sp. Amblyrhynchus cristatus, Sula sula) whose population size is threatened.

Control methods elsewhere: There have been programs to control rats at a large scale to maintain a constant level of invasive predators to preserve native species in New Zealand (Kokako and Mohua). Pesticides, as pindone and 1080 (sodium fluoroacetate) are commonly distributed via helicopter aerial spraying as a method of crowd control in infested islands with populations of invasive rats. Bait such as brodifacoum was also used with colored dyes to kill rats and identify experimental and monitoring purposes. Another method to keep track of rats is to use wire cage traps, which are used with bait such as oatmeal and peanut butter, to label and track rats and determine the size of the population through methods such as mark-recapture and radio-tracking. Poison control methods are effective in reducing populations of rats to nonthreatening sizes but rat populations often increase in a few months. Besides its foraging behavior highly adaptable and fast reproduction, the exact mechanisms of recovery is uncertain and is still being studied. In 2010, the Puerto Rican Ornithological Society (Puerto Rico Bird Society) and the Yacht Club de Pesca Ponce launched a campaign to eradicate the black rat Mice and Isla Cardona islands of the municipality of Ponce, Puerto Rico. In 2013, the rat extermination campaign of Finch island in the Galapagos was performed, which directly affected the birth of tortoises (Chelonoidis ephippium) endemic to this island.

Known Pest elsewhere: Widespread worldwide

Prevention options: Una manera de prevenir su ingreso a sitios e islas donde aún no se encuentran es revisar constantemente los barcos, aviones y lanchas que arriban a sitios prístinos en Galápagos.

Year of first record: 1835

Year of introduction: 1600

Distribution

Distribution map of specimen collection localities or observation records for this species in our collections database.

Distribution: This species is widely distributed in the archipelago. It is found in Baltra, Bartholomew, Florena, Isabela, Santa Cruz, San Cristobal, North Seymour, Pinzón, and Santiago islands. Also present in the islets: Albany, Cousins, Eden, Sombrero Chino, Shark Cove North and South, Beagle Crater 1, 2, 3 an

References

  • Jiménez-Uzcátegui, G. Carrión, V., Zabala, J., Buitrón, P. & Milstead, B. (2007) Status of introduced vertebrates in Galapagos. Galapagos Report 2006–2007. Charles Darwin Foundation, Puerto Ayora, p. 136–141.
  • Jácome, M. (1989) Mamíferos introducidos en Galápagos. Informe técnico para la Fundación Charles Darwin y Servicio Parque Nacional. Galápagos. Puerto Ayora, Ecuador. 33 pp.
  • Harris, D.B. (2006) Introduced black rats abd endemic Galapagos rice rats: competition, coexistence and conservation. A thesis submitted for the degree of Doctor of Philosophy. Linacre College, Oxford.
  • Hickin, N. (1979) Animal life of the Galapagos. Ferundune Books, Faringdon, U.K., 236 pp.
  • Atkinson, I. A. E. Atkinson, T. J. (2000) Land vertebrates as invasive species on islands served by the South Pacific Regional Environment Programme. In: Invasive Species in the Pacific: A Technical Review and Draft Regional Strategy. South Pacific Regional Environment Programme, Samoa: 19-84.
  • Lovegrove, T. G. C. H. Zeiler, B. S. Greene, B. W. Green, R. Gaastra, and A. D. MacArthur. (2002) Alien plant and animal control and aspects of ecological restoration in a small 'mainland island': Wenderholm Regional Park, New Zealand. In Turning the tide: the eradication of invasive species: 155-163. Veitch, C.R. and Clout, M.N.(eds). IUCN SSC Invasive Species Specialist Group. IUCN. Gland. Switzerland and Cambridge. UK.
  • Merton., D, G. Climo, V. Laboudallon, S. Robert, and C. Mander. (2002) Alien mammal eradication and quarantine on inhabited islands in the Seychelles. In Turning the tide: the eradication of invasive species: 182-198. Veitch, C.R. and Clout, M.N.(eds). IUCN SSC Invasive Species Specialist Group. IUCN. Gland. Switzerland and Cambridge. UK.
  • Moors, P. J. Atkinson, I. A. E. and Sherley, G. H. (1992) Reducing the rat threat to island birds. Bird Conservation International 2: 93–114.
  • O'Connor, Cheryl E. and Charles, T. Eason (2000) Rodent baits and delivery systems for island protection. SCIENCE FOR CONSERVATION 150
  • Russell, James C. David R. Towns, Sandra H. Anderson and Mick N. Clout. (2005) Intercepting the first rat ashore. Brief communications Nature 437, 1107 (20 October 2005)
  • Thorsen, M. R. Shorten, R. Lucking and V. Lucking. (2000) Norway rats (Rattus norvegicus) on Frégate Island, Seychelles: the invasion; subsequent eradication attempts and implications for the island's fauna. Biological Conservation Volume 96, Issue 2, December 2000, Pages 133-138
  • Tompkins J. (2001) Eradication of Rattus norvegicus from Seabird habitat in Canada. CWS, British Columbia, Canada.
  • Bertram D. F. Nagorsen D. W. (1995) Introduced rats on Queen Charlotte Island: Implications for seabird conservation. Canadian Field-Naturalist 109: 6 – 10
  • Lattanzio, R. M. Chapman, J. A. (1980) Reproductive and physiological cycles in an island population of Norway rats. Bulletin of the Chicago Academy of Sciences 12: 1-68.
  • Moors P. M. (1985) Norway Rats (Rattus norvegicus) on the Noises and Motukawao Islands, Hauraki Gulf, New Zaland. New Zealand Journal of Ecology 8: 37 - 54.
  • Silver, J. (1927) The Introduction and Spread of House Rats in the United States. Journal of Mammalogy, 8/1: 58-60.
  • Buitrón, P. J. Zavala (2007) Revisión, compilación y evaluación de datos sobre Rattus sp. en el archipiélago de Galápagos. Informe sobre la base de datos de roedores introducidos y análisis de los datos en ella contenidos. Fundación Charles Darwin. Informe Técnico. Pp. 1-24.
  • Angel, A. Wanless, R, M. and Cooper, J. (2009) Review of the impact of the introduced house mouse on islands in the Southern Ocean: are mice equivalent to rats? Biological Invasions 11: 1743-1754.
  • Cayot, L.J Rassman, K. and Trillmilch, F. (1994) Are marine iguanas endangered on islands with introduced predators. Noticias de Galapagos 53: 13-15.
  • Cayot, L.J. Muñoz, E. and Murillo, G. (1996) Conservation of the tortoises of Pinzón Island. Charles Darwin Research Station Annual Report 1988-1989: 29-35.
  • Cayot, L.J. (2007) Project Pinzon: Ecosystem restoration of the Galapagos Islands through introduced rodent removal. Charles Darwin Foundation and Galapagos National Park Service, Puerto Ayora, Galapagos. 54 pp.
  • Cruz, F. Cruz, J.B. (1987) Control of black rats (Rattus rattus) and its effect on nesting dark-rumped petrels in the Galápagos islands. Vida Silvestre Neotropical 1: 3-13.
  • Cruz, J.B. Cruz, F. (1987) Conservation of the dark-rumped petrel Pterodroma phaeopygia in the Galapagos Islands, Ecuador. Biological Conservation 42: 303-311.
  • Clark, D. B. (1978) Population biology of two rodents of the Galapagos Islands. Ph. D. Thesis. The University of Wisconsin, Madison. U. S. A.
  • Clark, D.B. (1980) Population ecology of Rattus rattus across a desert-montane forest gradient in the Galapágos islands. Ecology 61: 1422-1433.
  • Clark, D.B. (1984) Native land mammals. In: Perry, R. (ed.). Key environments: Galápagos, pp. 225-231. Pergamon Press, Oxford.
  • Empson, R. A. Miskelly, C. M. (1999) The risks , costs and benefits of using brodifacoum to eradicate rats from Kapiti Island, New Zealand. New Zealand Journal of Ecology 23: 241-254.
  • Key, G. E. Muñoz, E. (1994) Distribution and current status of rodents in the Galápagos Islands. Noticias de Galápagos 53: 21-25.
  • Muñoz, E. (1990) Seguimiento de la campaña de erradicación de ratas en la Isla Pinzón. Carta Informata 30 (Estacion cientifica Charles Darwin, Servicio Parque Nacional Galápagos): 2.
  • Patton, J.L. Yang, S. Y. and Myers, P. (1975) Genetic and morphologic divergence among introduced rat populations (Rattus rattus) of the Galápagos Archipelago, Ecuador. Systematic Zoology 24: 296-310
  • Snell, H.L. Snell, H.M. and Stone, P. (1994) Accelerated mortality of Opuntia on Isla Plaza Sur: Another threat from an introduced vertebrate? Noticias de Galapagos 53: 19-20.
  • Towns, D. R. Atkinson, I. A. E. and Daugherty, C. H. (2006) Have the harmful effects of introduced rats on islands been exaggerated? Biological Invasions 8: 863-891.
  • Harper G. A. Carrion, V. (2011) Introduced rodents in the Galápagos: colonisation, removal and the future. Island invasives: eradication and management. Pages 63-66 In: Veitch, C. R.; Clout, M. N. and Towns, D. R. (eds.). 2011. Island invasives: eradication and management. IUCN, Gland, Switzerland.

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