Black rat  (Rattus rattus)

The black rat is classified as Least Concern (LC) on the IUCN Red List (). It is not legally protected in the UK. No conservation designations (3).

Also known as the ship rat (2), the black rat (Rattus rattus) 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).

This species was once widespread throughout Britain until the brown rat was introduced (4). The black rat 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).

You can view distribution information for this species at the National Biodiversity Network Gateway.

The black rat 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).

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; three to five litters can be produced in a year, each litter containing 1 to 16 young (although the average is seven). 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 to 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).

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 the black rat occurs (4).

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

There may be further information about this species available via the National Biodiversity Network Gateway.

View information on this species at the UNEP World Conservation Monitoring Centre.

For more on the black rat:

BBC WildFacts:
http://www.bbc.co.uk/nature/wildfacts/factfiles/272.shtml