Black (or Ship) rat

Black rats are one of the rarest mammals in Britain now, their numbers having diminished over the last fifty years as dockyards, which served as their last outpost, have been modernised. They reached Britain on trade ships in Roman times, having spread originally from India. Despite their name, their coats vary in colour from black to grey-brown. Ship rats are smaller than brown rats and have comparatively larger eyes and ears. They have longer, thinner tails and their ears are almost hairless, compared with the furry ears of brown rats. In towns, ship rats live only within buildings, such as dockside warehouses, while on islands, they occupy rocks and cliffs. They are mostly nocturnal and live in groups with a dominate male. Skilled and agile climbers, they can run along telephone wires, and prefer to make their nests high up in roof spaces, giving them their other name of roof rats. In the tropics, and reportedly on the Channel Islands, they also live in trees.

Head-body length: 10 – 24cm
Tail length: A little longer than head-body length
Weight: 150 – 200g
Lifespan: Up to 18 months

Reproduction

Up to five litters of on average 5 – 8 pups are born between March and November.

Diet

Seeds, fruit and grain.

Habitat

Often inside large storage buildings, but also in grassy fields.

Predators

Domestic cats in urban areas, and elsewhere, most mammalian and avian predators.

Threats

Black rats have been gradually displaced by the larger brown rat, which is better adapted to withstand the cold in temperate countries. Rat-proof food stores have also hastened their disappearance.

Status & conservation

Non-native; possibly extinct.

Population size & distribution

The last permanent population in the UK was on the Shiant Islands in the Hebrides, but this was eradicated in 2018. There may still be transient populations in Southwark in London, and Avonmouth, and some small populations on offshore islands. It is not known whether they are still present on the Channel Islands of Alderney and Sark.

Did you know?

The black rat was thought to carry the ‘black death’ plague, which killed around 40 percent of people in Europe in the 14th century. The disease is caused by a bacterium and was spread most commonly by the bite of fleas. A study in 2015, however, indicates that it was not rats that carried the fleas, but gerbils. After six centuries, black rats may have been exonerated.