Galapagos Species Checklist

Mus musculus (Linnaeus, 1758)

Ratón, pulpero, ratón casero, House mouse

House Mouse (Mus musculus). Photo: Heidi Snell, CDF.
House Mouse (Mus musculus). Photo: Heidi Snell, CDF.

Mice are small rodents that do not exceed 20 cm in total length, and its tail (6 to 10.5 cm) is longer than the body (6 - 9.5 cm). It has an approximate weight of 12-30 g, prominent black eyes, round ears and a pointed snout with long whiskers. Fur color varies from brown to black with white belly and gray, and the tail has a lighter color than the body. Its sense of sight is poorly developed, but their hearing and smell are very sensitive, to help it escape danger and find food. Adults have sexual dimorphism that is not visually detectable in plain sight, but detectable with direct manipulation of the animals. The testes of the male are large in proportion to the body. Females have five pairs of mammary glands with nipples, males lack these. Mus musculus is active at dusk or at night, it avoids bright lights. It is territorial and lives in colonies.










Taxon category: Accepted

Syn: Mus abbotti Waterhouse, 1837, Mus domesticus Rutty, 1772. Includes domesticus as a subspecies (Wilson and Reeder 2005). All Philippine populations of Mus are now placed in the species M. musculus (subspecies castaneus) and the species is considered to be non-native (Marshall 1977).


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

Habitat preferences: In the wild, mice live in underground burrows. These are a complex network of tunnels and storage chambers for nesting with three or four outputs. They also associate with man living in homes, farms, buildings, farmland, pastures, forests, bushes, woodpiles or anywhere near a feeding source. They build their nests with paper, cloth or any soft material they can find. They reach a high number of individuals in some habitats, particularly those with dense vegetation cover. Mice are also on sub-antarctic islands, where they are a major concern for conservation.

Feeding type: Polyphagous

Their diet is mainly based on cereals, fruits, grains, seeds, wood, stems, roots, leaves; but they may also eat carrion, insects, arthropods and dairy products.

Feeding preferences: In nature, mice eat many kinds of vegetable matter such as seeds, roots, leaves and stems. They also feed on insects (beetle larvae, caterpillars and cockroaches) and meat (carrion) when available. In association with humans, they consume any food to which they have access, even soft materials such as paper, textiles, waxes, etc. They prefer cereals with high proportions of fat or protein. Much of the water needs are met by the moisture content of food and their ability to concentrate urine. This has allowed them to colonize semi-desert areas. They can survive without water if they consume seeds with 12% protein, but above this level they require 3-13 g of water per day.

Trophic role: Omnivorous

Persistence mechanisms: Their reproductive success makes them very successful in addition to its speed and ability to escape predators. Another feature that promotes their persistence is that they can be fed and adapted to a variety of substances that are available in the environment in which they live.

Reproduction mode: Exclusively sexual

Reproductive biology: If the nutritional conditions are favorable for M. musculus, it can reproduce all year round, while wild mice breeding seasons may be influenced by a combination of day length and nutrition. It is a polygamous animal, its estrous cycle is four to six days, and the heat lasts less than a day. Females experience an estrus after 12 to 18 hours of delivery. Under optimal conditions, a female may have five to ten litters per year, each of 3-12 offsprings. Gestation lasts 19 to 21 days and if the female is lactating, it may extend a few more days. The young are born naked and blind, on the tenth day they have hair, at 14 days they and open their eyes. They are weaned at three weeks and reach sexual maturity between at five and seven weeks old. The average life expectancy is about two years in captivity, and in nature most mice live 12 to 18 months.

Distribution origin: Mus musculus was originally a Palaearctic species (including Europe, Asia north of the Himalayas, northern Africa and northern and central parts of the Arabian peninsula). Because of their association with humans, it has been introduced worldwide.

Natural enemies: Mice are eaten by a variety of small predators worldwide, which includes cats, foxes, weasels, ferrets, mongoose, lizards, snakes, hawks and owls.

Associated species in Galapagos: Humans

Economic Use: Domestic forms and albinos are used as pets and laboratory animals. Mice are sold as pet food (usually for large reptiles), and they even have a small role as a depredator of insects, but this role is minimal.

Disease vector: Mice spread diseases like murine typhus, exanthematous and vesicular rickettsiosis, tularemia, salmonella, bubonic plague (Yersinia pestis), toxoplasmosis, lymphocytic choriomeningitis and Lassa fever. Recent research shows that they bear the same mammary tumor virus that can contribute to human breast tumor.


Introduction route: Accidentally introduced

Invasion risk score: Moderate risk

Impact in Galapagos: Introduced rodents in the Galapagos are producing an adverse effect on a number of endemic and native species, and a general negative impact on many others. Because M. musculus shares habitat with R. rattus and R. norvegicus, the direct impact of mice is very difficult to measure, but in South Plaza islands, where they are the only introduced rodents, it has been possible to detect its impact on flora and fauna. For example, mice make holes in the ground between the root systems of Opuntia, causing the fall of adult cactus; they also eat and destroy the seeds of Opuntia, this prevents the regeneration of plants from seed. They disturb the nests of land and sea birds. It is not known if they have an effect on existing reptiles on the island.

Impact elsewhere: M. musculus is less harmful than Rattus norvegicus and Rattus rattus in terms of health and economic problems. They are agricultural pests, they consume and contaminate human food with their droppings. They also destroy wood, furniture, upholstery, clothes, papers and everything they may crack. Mice produce negative impacts on plants, invertebrates, lizards, land and sea birds, they have caused the extinction of indigenous species in the ecosystems they have invaded and colonized. When mice are the only species introduced into an island, their behavior is more similar to that of rats and they have a much greater impact on the native ecosystem. When mice are part of a complex of invasive species, their densities are suppressed and their impacts are lower.

Control History in Galapagos: Programs had not implemented to control or eradicate M. musculus in the Galapagos Islands until 2012, when a mass poisoning was made with the idea of eradicating mice in South Plaza Island (waiting for results). Before this date, control methods had not target to M. musculus, however, was a non-target prey in Rattus sp controls.

Control methods elsewhere: Mice are controlled by poisoning, spraying, traps and repellents. Thirty eight percent of eradication attempts on islands around the world have failed due to operational flaws: good planning and knowledge of the species in the area to be treated is important. There are some points to consider before starting a control or eradication project: 1) Ensure that the chosen control method contemplates that each mouse in the island has access to the poison, 2) Consider the pressure that other mammals have on mice, this will prevent them from accessing the poison, 3) Conduct tests to check whether the mice like the taste of the poison or reject it, and 4) Consider that there are areas that require extra poison due to weed density, because dense grasslands tend to have greater abundance of mice and require more poison. Mice have been eradicated in 28 islands in the world with the use of chemical anticoagulants (Brodifacoum). Pindona, Warfarin, and Floccoumafen Bromodiolone have also been used. It is advisable to eliminate rats and mice simultaneously by an integrated invasive species management. Mice abundance increases when rats are removed in an area, because the food supply improves and predation pressure is freed.

Known Pest elsewhere: The species is widespread over all continents, except Antarctica. Established in America, Africa, Australia, and many oceanic islands.

Prevention options: To prevent entry to sites and islands where mice have not established yet, managers should thoroughly review the ships, planes, and boats arriving in pristine areas, and the materials being transported.

Year of first record: 1979


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

Distribution: It has been reported on the islands Santiago, Santa Cruz, Isabela, San Cristóbal, Florena, Baltra, North Seymour, South Plaza, North Plaza. It has also been reported in the islets Eden, Champion, Mosquera, Venice, Punta Bowditch North and South. In South Plaza Island, mice poisoning was performed. T


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