The black rat is also known as the ship rat or roof rat. It is a different species from the more familiar brown rat.
Black rats are exceptionally rare in Britain. They are not a species Guardian expects to encounter in routine work in Somerset, so this page is here to explain an interesting part of rodent history and natural history.
What does a black rat look like?
Despite its name, a black rat is not always black. Its fur can range from black to grey-brown. It is usually smaller and more slender than a brown rat, with larger ears and eyes, a pointed muzzle and a thin tail that is usually longer than its head and body.
The tail is a useful identification clue, but colour or one feature alone cannot confirm the species. A close look at the animal and the other signs is needed.
For a quick mental picture, Hugh compares the brown rat to a Mini Maestro and the black rat to a GTI. It is not a scientific description, of course, but it captures the black rat’s slimmer build and agile way of moving.
A natural climber
Black rats are nimble climbers. They can use their balance and agility to move along pipes, beams and other raised routes, and they often nest in roof spaces or other high parts of a building. That is why they are sometimes called roof rats.
They are not restricted to the upper floors. Brown rats can also climb and may be found in lofts or other high areas. Where a rat is seen in a building is only one clue, not a reliable way to identify its species.
Black rats tend to eat seeds, fruit and grain, although they are omnivores and can eat other food when it is available. Their diet is generally more plant-based than that of brown rats.
How black rats reached Britain
Black rats are thought to have reached Britain on trading ships during Roman times. They were once much more widespread and became associated with ports, ships, warehouses and other large buildings.
Brown rats arrived in Britain much later, in the eighteenth century. Over time, they displaced black rats across much of the country.
The last known permanent black rat population in Britain was on the Shiant Isles in Scotland. It was removed in 2017 and 2018 to protect seabirds. Today, there are no known permanent populations, although occasional or transient animals may still be recorded.
Black rats and the plague
Black rats are often linked with the Black Death because rats can carry fleas, and infected fleas can transmit the plague bacterium, Yersinia pestis. That link is real, but the full story is less certain than the familiar account suggests.
The Black Death spread through Europe between 1346 and 1353. Estimates vary because records from the period are incomplete, but researchers commonly estimate that around 30 to 60 per cent of Europe’s population died. Some estimates put the number of deaths in Europe between 25 and 50 million.
The precise routes by which plague spread so rapidly are still debated. Infected fleas are a known route of transmission, but researchers disagree about how much black rats and their fleas contributed to the Black Death. Human fleas and body lice have also been proposed as possible contributors. It would be too definite to say that black rats alone caused the pandemic.
The Great Plague of London came much later, in 1665 and 1666. About 68,600 plague deaths were recorded in London, although the true number may have been closer to 100,000.
Plague today
Plague has not disappeared. It continues to circulate among wild animals and their fleas in some parts of the world. The US Centers for Disease Control and Prevention reports an average of about seven human cases a year in the United States in recent decades, mostly in rural areas of the West. In June 2026, New Mexico reported its first human case of the year, after three cases in 2025.
These cases are rare and occur in regions where plague is present in local wildlife. They do not mean that black rats or plague are a routine concern in Somerset.
A few facts worth remembering
- A black rat’s coat may be black, grey-brown or somewhere in between.
- Its tail is usually longer than its head and body.
- “Ship rat” and “roof rat” are both common names for the same species, Rattus rattus.
- Black rats reached Britain centuries before brown rats, but brown rats later became the much more familiar species.
- The plague bacterium is transmitted by infected fleas, but the role of black rats in the Black Death remains disputed.
