Galapagos Species Database

The Galapagos Species Database shares the information about the species from our Natural History Collections.

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.










Taxon category: Accepted

Taxon origin: Introduced - established


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.


Mode of introduction: Accidental

Introduction Pathway: Stowaway

Subpathway: Hitchhiker on boats

Introduced status: Naturalized

Invasive status: Invasive

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: 1600

Year of introduction: 1600


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


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You are welcome to download and use the information found in this page, acknowledging the origin of the data.
This page should be cited as follows:
"Galapagos Species Database, Rattus rattus", dataZone. Charles Darwin Foundation, Accessed 19 April 2024.