Rattus rattus

Rattus rattus, is found on all continents of the earth. Although the species is believed to be native to India and possibly other Indo-Malayan countries, it has been introduced through human travel overseas to all continents. It is most common in coastal areas because it is a rodent that flourishes in areas inhabited by humans as well as on large ships. For this reason, these animals are often called ship rats. Some other common names for this species include house rat, black rat, and roof rat. Rattus rattus thrives in tropical regions but has been largely driven out of more temperate regions by Noway rats, R. norvegicus. Norway rats, are closely related to black rats, but are more successful in colder climates. However, some data show that R. rattus has been able to adapt to more extreme cold and harsh climate conditions.

Biogeographic Regions: nearctic (Introduced ); palearctic (Introduced ); oriental (Native ); ethiopian (Introduced ); neotropical (Introduced ); australian (Introduced ); antarctica (Introduced ); oceanic islands (Introduced )

Other Geographic Terms: cosmopolitan

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Global Distribution

South Asia, China. Introduced to all parts of the world.

Western Ghats Distribution

INDIA Gujarat: Dangs: Ahwa: Valod; Karnataka:? Kerala: Idukki: Eravikulam NP; Palakkad: Thiruvazhamkunnu Maharashtra: Pune: Manjri, Pashan Tamil Nadu

Known Presence in Protected Areas

Kerala; Eravikulam NP, Periyar Tiger Reserve. Tamil Nadu; Kalakad Mundanthurai Tiger Reserve, Indira Gandhi Wildlife Sanctuary Maharashtra: Chandoli National Park, Nagrhole National Park, Goa; Bhagwan Mahaveer Wildlife Sanctuary,

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Widespread.

Originally an Indomalayan species, Rattus rattus was widely introduced across the globe as a result of human activities. In Europe, it has been present since ancient times, and is found in most countries. The species is widespread and common throughout the Mediterranean region. The list of countries of occurrence where the species is introduced is incomplete.

Still found throughout south-east Asia; includes a complex of at least four distinct species; Rattus rattus sensu strictu originally from Western India and Pakistan, spread worldwide thence.

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Native to the Indian Peninsula; introduced worldwide in the temperate zone and parts of the tropical and subantarctic zones (Musser and Carleton, in Wilson and Reeder 2005).

This species was once widespread throughout Britain until the brown rat was introduced (4). It originates from Asia, and today is widely distributed around the globe (4). It has been restricted to largely transient populations in Southwark, London and Avonmouth since 1884, and has undergone a drastic decline in range since the 1950s (4). It also persists on Lundy Island in the Bristol Channel and the Shaint Islands in the Outer Hebrides (4).

The black rat is nocturnal, although it may become more active in the day in undisturbed areas (4). It is an omnivore, but tends to prefer plant matter (4) such as fruits and seeds, although it will also feed on insects, carrion, refuse and faeces (2). On Lundy Island these rats feed on crabs along the shore (4). This rat lives in groups called 'packs', consisting of several males and two or more dominant females (4). They are skilled climbers and can also swim well (2). Nests are constructed from grass and twigs, often in roof spaces, a habit which earned the species the further common name of 'roof rat' (2). Breeding takes place between March and November; 3 to 5 litters can be produced in a year, each litter containing 1-16 young (although the average is 7). A single female can therefore produce a huge number of offspring; 56 young were recorded on a London ship for a single female (4). At 12-16 weeks of age, females are capable of breeding; they are also able to conceive whilst still suckling the previous litter, which further maximises their reproductive capability (1).Maximum lifespan in the wild is less than 18 months; populations have very high mortality rates, mainly as a result of widespread pest control measures (4). The black rat is a notorious pest, and was the host of the fleas that carried bubonic plague (2). It also carries a host of other diseases and is damaging to property and food stores (1).

Also known as the ship rat (2), the black rat was introduced to Britain with the Romans (4). Generally smaller than the brown rat (Rattus norvegicus), the black rat is typically a uniform black to tawny brown colour, with lighter underparts (1). The tail, which is longer than the head and body, is hairless, and is used for balance (2).

Rattus rattus is a medium sized rat with relatively large ears and a tail that is nearly always longer than the body. Individuals weigh between 70 and 300 g, and are between 16 and 22 cm in head and body length and a tail length of 19 cm or longer. Males are longer and heavier than are females.

Many members of the species are black in color with a lighter colored ventral belly. The species is often divided into subspecies based upon color patterns which can occur in any combination of black, white, grey, and agouti.

The skull and nasal bones are relatively narrow. One of the main ways to differentiate between R. rattus and R. norvegicus is that R. rattus has a finer covering of hair, a lighter skull, and a slightly differently shaped upper first molar.

Range mass: 70 to 300 g.

Average mass: 200 g.

Range length: 16 to 22 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

Average basal metabolic rate: 0.77 W.

Length: 46 cm

Weight: 350 grams

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Habitat

Tropical dry deciduous forests, subtropical dry deciduous forests, tropical mangrove forest, subtropical mangrove forests, tropical and subtropical scrub, tropical grasslands, arable lands, urban areas, rural gardens, human settlements, found in all habitats except cold deserts

Niche

Various niches

Habitat Status

Quantitative and qualitative increase in favourable habitat due to expansion of human habitation

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Habitat and Ecology

Systems

• Terrestrial

Rattus rattus is most often found in large numbers in coastal areas because of the way the species is spread through human sea faring. It is generally found in any area that can support its mainly vegetarian diet. Because R. rattus is an agile climber, it often lives in high places, such as top floors of buildings in populated areas or trees in forested areas. Even though it can be found near water, this species rarely swims and unlike its close relatives, rarely finds a home in sewers or in aquatic areas. Although it was formerly common in towns and farms of temperate regions, it has been largely driven out by the more aggressive Norway rat as well as killed off by increasing chemical pest control programs. Data have shown that R. rattus can reach elevations up to 250 m above sea level.

Range elevation: 0 to 250 m.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: savanna or grassland ; chaparral ; forest ; rainforest ; scrub forest

Other Habitat Features: urban ; suburban ; agricultural

Comments: Often associated with humans; buildings, sewers, seaports. In natural habitats in some areas (e.g., Pacific islands [wooded gulches, sugar cane fields, dry and wet forests, coconut palms] and West Indies). In Hawaii (western Mauna Kea), preferred dense tree stands and tall grass over open areas (Amarasekare 1994); abundant in mesic to wet native forest on Maui (Sugihara 1997). Often arboreal. Young are born in nests in protected sites in buildings or within other cover (e.g., ricebird nests in Hawaii, Van Riper 1974; coconut shells, Twibell 1973).

This species is closely associated with buildings around the world, although in Britain it tends to inhabit rocky shores and cliffs. On the islands it occasionally occurs on rubbish dumps and around buildings (4).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Rattus rattus generally feeds on fruit, grain, cereals, and other vegetation. It is an omnivore, however, and will feed on insects or other invertebrates if necessary. It consumes about 15 g/day of food and 15 mL/day of water. Because it consumes and destroys the food source during feeding, it can cause devastating damage to farms and livestock. Not only does it gnaw through many materials but it ruins more than that by excreting on the remains of its foraging efforts.

Animal Foods: insects

Plant Foods: leaves; wood, bark, or stems; seeds, grains, and nuts; fruit

Primary Diet: herbivore (Granivore )

Comments: Very opportunistic feeder on plant/animal foods; partial to grain.

Impact of these animals on their ecosystems has not been studied. However, we may infer from their feeding habits that they have some impact on plant communities. As a prey species, they may impact populations of those animals which feed upon them. Also, they compete with other species of rodents, such as Rattus norvegicus. Rattus rattus is a disease vector, responsible for bubonic plague outbreaks and other diseases. This cosmopolitan species hosts a wide variety of internal and external parasites, up to 18 species of gastrointestinal helminths in some areas.

Mutualist Species:

• Homo sapiens

Commensal/Parasitic Species:

• Oriental rat flea (Xenopsylla cheopis)
• rat flea (Nosopsyllus fasciatus)
• cestodes (Hymenolepis diminuta)
• cestodes (Taenia taeniaeformis)
• cestodes (Raillietina sp.)
• nematodes (Mastophorus muris)
• nematodes (Trichuris muris)
• nematodes (Syphacia sp.)
• nematodes (Nippostrongylus brasiliensis)
• acanthocephalan (Moniliformis moniliformis)
• trypanosomes (Trypanosoma lewis)

Known predators of R. rattus vary depending on environment. In urban or suburban areas, house cats are the main threat to its survival. In less populated areas, birds and other carnivorous animals prey upon it. One possible anti-predator adaptation is the array of color patterns found in this species. Some evidence suggests that color is related to geographical location and therefore ability to remain less conspicuous in the local environment. Also, rats are often aggressive toward other rats. Captive studies have shown R. norvegicus will kill R. rattus. Rattus rattus has a typical threat pose in which it stands on its hind feet and bares its teeth.

Known Predators:

• domestic cats (Felis silvestris)

Anti-predator Adaptations: cryptic

Rattus rattus is prey of:
Buteo jamaicensis
Buteo platypterus
Epicrates inornatus
Felis silvestris catus
Otus nudipes
Herpestes auropunctatus
Diptera
Calodium hepaticum
Secernentia nematodes

Based on studies in:
Puerto Rico, El Verde (Rainforest)

This list may not be complete but is based on published studies.

Rattus rattus preys on:
Eleutherodactylus coqui
Eleutherodactylus richmondi
Eleutherodactylus portoricensis
Eleutherodactylus wightmanae
Eleutherodactylus eneidae
Eleutherodactylus hedricki
fruit
seeds

Based on studies in:
Puerto Rico, El Verde (Rainforest)

This list may not be complete but is based on published studies.

Home range less than an acre. Summer density estimated at 72/ha and 346/ha on two grids in Puerto Rico (Zwank and Layton 1989).

"Nocturnal, fossorial to semi-arboeal, ruderal"

Rattus rattus is a somewhat vocal animal, producing squeaks when threatened or socializing. It also produces oil smears that are left along particular areas to illustrate territorial boundries. Hierarchy in groups is determined using aggressive threat postures and physcial contact. Vision, hearing, touch, and smell are all used in sensing the environment.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: pheromones ; scent marks

Perception Channels: visual ; acoustic

Comments: Active mainly at night. Diurnal activity is common on some West Indies islands.

Rattus rattus tends to live for about a year in the wild with an annual mortality rate of 91 to 97%. In captivity, it has been reported to live for up to 4 years.

Range lifespan
Status: wild: 1 (high) years.

Range lifespan
Status: captivity: 4 (high) years.

Typical lifespan
Status: wild: 1 (high) years.

Typical lifespan
Status: captivity: 1 (low) years.

Maximum longevity: 4.2 years (captivity) Observations: One captive specimen lived for 4.2 years (Richard Weigl 2005).

Social groups of R. rattus are often formed of multiple males and multiple females. One male is dominant and a linear male hierarchy may form. Two to three females are often dominant to all other group members except the dominant male. Females are generally more aggressive than males. The species is polygynous, and generally, the dominant male is the most successful breeder. Territories and mates are defended through aggressive behavior. If environmental conditions allow it, successful breeding may occur all year.

Mating System: polygynous

Rattus rattus is able to breed throughout the year if conditions allow. The peak breeding seasons are summer and autumn. Females can produce up to 5 litters in one year. The gestation period ranges between 21 and 29 days, and young rats are able to reproduce within 3 to 5 months of their birth. Neonates are altricial, like most rodents, and their eyes do not open until 15 days of age. Young remain hairless for much of their nursing period. Weaning and independence from the mother occur at about 3 to 4 weeks of age.

Breeding interval: R. rattus breeds year-round producing up to five litters in that time.

Breeding season: R. rattus mates throughout the year if environmental conditions permit, however peak times are summer and autumn seasons.

Range number of offspring: 6 to 12.

Average number of offspring: 8.

Range gestation period: 21 to 29 days.

Range weaning age: 3 to 4 weeks.

Range time to independence: 3 to 4 weeks.

Range age at sexual or reproductive maturity (female): 3 to 5 months.

Range age at sexual or reproductive maturity (male): 3 to 5 months.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 4.55 g.

Average number of offspring: 7.3.

Because male members of R. rattus copulate with one female and then move on to the next, they don't contribute much to the care of the young. The young remain relatively helpless for about 2 weeks, until they begin to grow a pelage, their eyes open, and they are able to move around more. Weaning is accompanied by increased independence from the mother. Until these rats reach their full adult size, they stay in the nest built by their mother. Young rats are capable of reproducing by about 3 to 5 months of age.

Parental Investment: no parental involvement; altricial ; female parental care ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female)

Breeds throughout the year. Gestation lasts 21 days. Produces several litters of 6-22 (average around 8-9) young per year; average reported as 6.5 in Hawaii (see Kramer 1971).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 10
Specimens with Barcodes: 90
Species With Barcodes: 1

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 17 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 1996
  Lower Risk/least concern

Rattus rattus has no special conservation status. They are widespread and abundant, especially in areas where humans live.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Non-native, resident.

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: G5 - Secure

Not legally protected in the UK. No conservation designations (3).

Population

Population Trend

"Pest control practices, natural calamities like fire, rise of temperature, pathogens or parasites affecting the individuals, used in research for human disease investigations, hunted for local consumption"

Major Threats

The future of this once devastating pest in Britain is now uncertain. Improved hygiene and control measures on ships makes further introductions highly unlikely, and control measures such as poisoning with rodenticides are ever-prevalent, particularly close to human habitation, where this species occurs (4).

"India Schedule V of the Indian Wildlife (Protection) Act, 1972, amended up to 2002."

Conservation Actions

Management Requirements: Scowcroft and Sakai (1984) recommended control of rats during first 5 years of koa planting or regeneration in Hawaii.

The question as to whether this species should now receive a level of protection due to its poor status is a highly contentious issue (4).

Although not generally viewed fondly by humans, Black Rats are welcome at the Karni Mata Temple in northern India, where the rats are treated as sacred.

Rattus rattus is a pest and is dangerous to humans in several ways. First, these animals are severely destructive to crops, farms, and fruit trees. Not only do they feed on these but they tend to destroy what they are unable to consume. By urinating and defecating on remains of their meals, they ruin grain, cereals, and other food sources. This species is famous for its role in spreading the bubonic plague (Yersinia pestis) that took millions of lives in the middle ages. The fleas that live on these rats carry a number of diseases that can seriously harm humans, livestock, and other animals.

Negative Impacts: injures humans (causes disease in humans , carries human disease); crop pest; causes or carries domestic animal disease ; household pest

There are no known benefits of R. rattus for humans. Norway rats, the closest related species, is often used for research and as pets.

Comments: Often a severe pest; destructive to stored crops, coconuts, and to native flora on Pacific Islands (Scowcroft and Sakai 1984, Baker and Allen 1978, Twibell 1973), damages sugarcane in southern Florida (Lefebvre et al. 1989); public health menace.

Species Impact: Implicated in decline of native fauna in Hawaii (Atkinson 1977), though Amarasekare (1994) found no evidence that this species is an important predator on honeycreepers on western Mauna Kea. Rat control reduced predation on dark-rumped petrel on Maui (Buxbaum 1973). Implicated as a contributor in the decline of the ancient murrelet and other burrow-nesting seabirds (see Bertram and Nagorsen 1995).