Otters are restless, playful and secretive mammals that spend most of their time along riverbanks. They have stocky legs, a long, streamlined body, and a broad muzzle with prominent, sensitive whiskers. They are perfectly adapted to a semi-aquatic life. Their webbed feet and long, muscular tail enable them to swim comfortably at about one metre per second and they will dive to catch small fish or to avoid danger. Otters can see as well under water as they can above it, allowing them to hunt for fish. From a distance, they can be confused with mink, particularly as they are found in similar habitats, but otters are much larger and when they swim, they do so with just their head showing above the water, while mink swim with their heads and backs exposed.

Head-body length: 59 – 110cm (males are larger than females on average)
Tail length: 35 – 45cm
Weight: 7 – 11kg
Lifespan: Up to 10 years


Mating occurs at any time of the year and females give birth to 2 – 3 cubs, usually between May and August. Cubs are usually born in a holt in a bank, or between rocks or tree roots. Newborns are only about 12cm long but grow quickly and can swim at three months. They leave the protection of their mothers at 10 – 12 months and can breed at 2 years old.


Mostly fish such as eels, but also water birds, such as moorhens and ducks, frogs and rabbits.


Wide range of aquatic habitats including clean rivers, lakes and coastlines; less commonly, marshy areas.


Few natural predators.


Road traffic accidents; drowning in fish and lobster traps; and pollution such as oil and PCBs.

Status and conservation

Native and localised. They are a priority species in the UK Biodiversity Action Plan and are classified as Near Threatened on the IUCN Red List (2004). They are fully protected in the UK under Schedule 5 of the Wildlife and Countryside Act 1981.

Population size and distribution

GB population 11,000. GB IUCN: Least concern. But in Scotland and Wales, they are considered Vulnerable. The population has continually increased over the last 25 years and their range is expanding in England.

Did you know?

Otters mark their territory with their droppings, known as spraints, which they leave at conspicuous sites along the water’s edge, and surveys of these have been the primary way that otter populations have been monitored. The spraints have an unusual sweet, musky smell that has been compared to the smell of jasmine tea.

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