Galapagos Species Database

Taxon category: Accepted

Syn: Epimys norvegicus Miller, 1912, Mus decumanus Pallas, 1778, Mus hibernicus Thompson, 1837, Mus norvegicus Berkenhout, 1769

Taxon origin: Introduced - established

Preference for an altitude zone in Galapagos: Coastal zonera - humid zone

Habitat preferences: In Asia, R. norvegicus was native to forests. Nowadays, its most common habitat is near human dwellings. Almost every port city in the world has a substantial population of Norway rats. It adapts to any habitat except the desert and glaciers. Commensal of human settlements, especially rampant in big cities in the sewers, cellars, and stables. It is present often near water, agricultural areas, coastlines, natural forests, planted forests, rangelands, disturbed riparian zones, scrublands, wetlands, culverts, barns, farms, landfills, etc. When they build their nests on the ground, they build their galleries about 40 or 50 cm deep, whose entries are located easily due to accumulation of land forming piles on one side of the entrance. The Norway rat is territorial most of the year; but if food is scarce, it begins to migrate. They do not climb trees. In the Galapagos Islands, they prefer to move through underground cracks and crevices in the lava rocks. They are good swimmers, and they can even dive and swim comfortably up to 1 km, and up to 2 km in open water.

Feeding preferences: Omnivorous, opportunistic, and voracious animal. It may consume up to one third of its weight daily. If its diet is solid-based, they must drink 25 ml of water per day. Norway rats eat a variety of foods, including raw or cooked meat, vegetable matter, grains, seeds, berries, and roots; they also eat a variety of vertebrate and invertebrate species. It prefers foods high in protein and starches, such as cereals. Norway rats are excellent hunters - gatherers during the spring and summer, they prefer to feed on eggs and birds, small mammals, insects, frogs, and toads. Examination of the stomach of a wild R. norvegicus in Germany revealed the presence of four thousand different things, most of which were plants; although studies have shown that Norway rats prefer meat when given this option.

Trophic role: Omnivorous

Reproduction mode: Exclusively sexual

Reproductive biology: Females have multiple estrus and ovulate spontaneously. R. norvegicus reproduces throughout the year, but the reproduction rate tends to decrease during the colder months. The gestation period is 21-23 days, each litter has 2-14 offspring, a female may breed up to 12 litters per year. The young are born hairless and blind, they open their eyes at 14 days. They are weaned at 3 or 4 weeks old, and reach sexual maturity at 11 weeks after birth. Females experience a postpartum estrus about 18 hours after birth, and can mate again. This reproductive function is responsible for the huge birthrates of Norway rats, which can reach 60 young each year per female. A litter has numerous females forming a single nest where the offspring are cared for by females regardless of whether they are theirs or not. Parenting is determined by food availability. They have a life span of about 3 years.

Distribution origin: Native to the Palearctic, mainly of Northeast China, Southeast Siberia and parts of Japan.

Natural enemies: It is attacked by foxes, birds of prey, mustelids and cats.

Associated species in Galapagos: Humans

Economic Use: Norway rat is widely used in medical, genetic and cosmetic research. This research has led to significant advances in physiology, genetics, immunology, pathology, and epidemiology. They are also used for behavioral studies because of its ability to learn quickly. They are popular pets, because these animals are easy to maintain.

Disease vector: Rats are capable of transmitting a number of bacteria, viruses and parasites that cause diseases such as plague (Yersinia pestis), Salmonelosis (Salmonella typhimurinum), Tifus de las Malezas (Rickettsia tsutsugamushi), Tifo murino (Rickettsia typhi), Fiebre Botonosa (Rickettsia conorii), Rickettsiosis vesiculosa (Rickettsia akari), Triquinosis (Trichinella spiralis), Angiostrongyliasis (Angiostrongylus cantonensis), Toxoplasmosis (Toxoplasma gondii), fiebre aftosa (Aphtovirus), Leptospirosis (Leptospira interrogans), among others.

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: The impact of the Norway rat in the flora and fauna of the Galapagos has not been thoroughly evaluated. However, it is known to affect several species of birds and reptiles both marine and terrestrial. They also affect native plants. It is a nuisance in agricultural areas and in the houses of the Galapagos inhabitants.

Impact elsewhere: By predation or competition, R. norvegicus contributes annually to the reduction or extinction of many species of mammals, birds, reptiles, amphibians, plants, and invertebrates worldwide. This also generates hundreds of millions in losses in industries, destruction of crops and food stores, chewing of electric wires, walls, floors, ceilings, and pipes. They are a real and present threat to humans and other animals because it spreads and transmits several diseases.

Control History in Galapagos: Few control campaigns have been elaborated for this species in the Galapagos. In 2011, an eradication campaign was conducted at Rabida island where baits were applied systematically by helicopter to cover the entire island. The application was made at the end of the dry season to increase the likelihood of rats finding and eating the poison. In rural and urban areas, there have been made control programs using poison stations at regular intervals. Several institutions such as municipalities, Galapagos Biosafety Agency (ABG), Ministry of Agriculture, Livestock and Fisheries (MAGAP) and non-governmental organizations (NGOs) have had the rat control in their hands, alleviating this pest in populated places. However, the lack of resources to maintain this control and little collaboration of the community regarding waste management make these systems unsuccessful and this pest is increasing.

Control methods elsewhere: The use of anticoagulant poisons such as Brodifacoum is very common for the control of rats and it has been successful in eradicating these animals particularly on islands. However, when it comes to rats control in cities, any control method used should go along with good hygiene and anti rats preparation on the premises (houses, buildings, restaurants, schools, warehouses, etc.). In addition to this, you must control the rat population in the outer areas (banks of rivers, streams, water sources, vacant lands, landfills, etc.). Possible entries should be sealed in installations (electrical conduits, ventilation, water pipes). Rodent removal programs should be permanent to avoid reintroduction of rodents at sites where it has been eradicated. To control rats, people also use sticker traps and mechanical control devices such as snap traps.

Known Pest elsewhere: Widespread, Norway rats can be found on every continent of the world except Antarctica.

Prevention options: The population size of rats and their permanence depend on the amount of food available, so it is essential to restrict or prevent access to any food source. Maintaining and respecting the quarantine and phytosanitary rules.

Year of first record: 1983

Year of introduction: 1980

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

Distribution: Santa Cruz, San Cristóbal, Isabela, Floreana?, Baltra?, Rábida.

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