Eurasian Otter (Lutra lutra): Facts, Diet and Habitat

Appearance

The Eurasian otter is built for swimming. It has a long, low, streamlined body, short legs, a broad flat head and a thick, muscular tail that tapers to a point. All four feet are webbed, and small ears and nostrils close when the otter dives.

The fur is brown to dark brown on the back and paler, often cream or gray, on the throat and chest. It has two layers: a very dense underfur that traps a layer of air next to the skin, and longer waterproof guard hairs on top. Otters do not have a thick layer of blubber like seals, so this fur is what keeps them warm in cold water, and they spend a lot of time grooming it.

The muzzle carries long, stiff whiskers, called vibrissae, which are very sensitive to touch and water movement. Eurasian otters look much like the North American river otter, but have a shorter neck, a broader face and a longer tail, and the two never meet in the wild.

How big is a Eurasian otter?

Males, called boars, are clearly larger than females, called sows or bitches. A big male can be about one-third longer and much heavier than an adult female. Including the tail, a large otter can measure well over 1.2 m (4 ft).

Habitat and range

Eurasian otters live in a wide range of wet places: fast upland streams, slow lowland rivers, lakes, marshes, canals, estuaries and rocky sea coasts. What they need most is a good supply of fish, clean water and plenty of cover along the banks for resting and breeding.

On coasts, such as in Shetland, western Scotland, western Ireland and Norway, otters hunt in the sea but still need regular access to fresh water to wash the salt out of their fur.

The species has a huge range. It lives across most of Europe, from Ireland and Portugal to Russia, in North Africa from Morocco to Tunisia, and across Asia through the Middle East, Central Asia, Siberia, China and Korea, south to India, Sri Lanka and parts of Southeast Asia. It is the only otter in most of Europe.

What does the Eurasian otter eat?

The Eurasian otter is a carnivore and above all a fish-eater. Studies of its droppings show that fish usually make up most of the diet, especially eels, salmon and trout, perch, carp-family fish and, on coasts, bottom-living fish such as rocklings and butterfish.

It also eats crayfish and crabs, frogs and toads, water birds such as ducks and moorhens, small mammals such as water voles and rabbits, and sometimes insects. The diet shifts with the seasons. Frogs and toads become important in late winter and spring, when they gather to breed. An adult otter needs roughly 1 kg (2.2 lb) of food a day.

Otters hunt mostly by sight in clear water and by touch with their whiskers in murky water or at night. They swim by pushing with their webbed hind feet and sweeping the body and tail up and down, and they can turn sharply in pursuit of a fish. Most hunting dives are short, often 15–30 seconds, and the otter surfaces between dives to breathe and look around.

Small prey is usually eaten in the water, with the otter floating on its back or holding the food in its forepaws. Larger fish, eels and crabs are carried to a bank or rock and eaten there, often starting from the head. Toads have poisonous skin, so otters often skin them before eating, leaving the skins behind as a clue for naturalists. For more detail, see what do otters eat?

Behavior

Eurasian otters are mostly solitary. A mother lives with her cubs, but adults otherwise live alone and meet mainly to mate. In much of Europe they are active at dusk and at night, partly to avoid people. On quiet coasts, such as in Shetland, otters often hunt by day, especially in the hours around low tide.

Each otter uses a long stretch of river or coast. On rivers, a home range can run for 20 km (12 mi) or more, and a male’s range may overlap those of several females. Otters move between many resting places: holts, which are dens in banks, tree roots or rock piles, and couches, which are open resting spots among reeds or brambles.

Otters communicate mainly by smell. They leave droppings called spraints, along with a sticky jelly from their scent glands, on prominent rocks, logs, grassy banks and under bridges. Spraints tell other otters who passed, how recently and whether a female is ready to breed. Otters also make high-pitched whistles, especially between mother and cubs.

Young otters are famously playful, sliding down banks and chasing each other, which helps them build hunting skills.

Reproduction and life cycle

Unlike many European mammals, Eurasian otters in Britain and much of western Europe can breed at any time of year, although local peaks occur. After a pregnancy of about 60–64 days, the female gives birth in a well-hidden breeding holt, usually to two or three cubs, sometimes one to four.

Cubs are born blind and covered in fine fur. Their eyes open at about one month old, and they first leave the holt at about two to three months. Their mother has to teach them to swim and catch prey. The cubs stay with her for about 10–13 months, longer than the young of most similar-sized mammals. The male plays no part in raising them.

Lifespan

Wild otters live surprisingly short lives. Many die in their first year, and studies of dead otters in Europe suggest that the average adult lives only about 3–4 years. A few reach 10 years or more in the wild. In captivity, Eurasian otters have lived to about 22 years.

Predators and threats

Adult otters have few natural predators in Europe, although foxes, birds of prey and stray dogs may take cubs. Most otter deaths today are caused by people, directly or indirectly:

• Road traffic is the biggest recorded cause of death in Britain and many other countries, especially where rivers pass under roads.
• Pollution: pesticides and industrial chemicals poisoned otters in the past, and water pollution still reduces fish stocks.
• Drowning in fish traps and nets, and illegal killing near fish farms.
• Habitat loss, including drained wetlands and cleared riverbanks.

Conservation status and recovery

The IUCN lists the Eurasian otter as Near Threatened worldwide. In Asia, many populations are declining because of illegal trade in otter skins, habitat loss and pollution.

In western Europe the story is one of recovery. From the late 1950s, otters crashed across Britain and much of western Europe. The main cause was organochlorine pesticides such as dieldrin, used in seed dressings and sheep dips, which built up in fish and poisoned otters. After these chemicals were restricted and banned in the 1960s to 1980s, water quality improved and otter hunting ended, otters slowly returned. By 2011 they had been recorded again in every county of England. Read more about this comeback in are there otters in the UK?

Otters are now strictly protected under the EU Habitats Directive and national laws, and they are often used as a sign of healthy rivers.

Otters and people

People have had a mixed relationship with otters. For centuries, otters were killed for their fur and because anglers and fish-pond owners saw them as competitors. In Britain, otter hunting with packs of hounds was a traditional sport until the otter was given legal protection in England and Wales in 1978 and in Scotland in 1981.

Attitudes changed during the 20th century. Henry Williamson’s novel Tarka the Otter (1927) followed the life of a wild otter in Devon and is still widely read. Today otters are among the most popular wild animals in Europe, and otter-watching brings visitors to Shetland, the Scottish islands and many river reserves.

Some conflict remains. Otters can take large numbers of fish from garden ponds, fish farms and stocked fisheries, and owners often protect them with otter-proof fencing. In most of Europe it is illegal to kill, injure or disturb an otter or damage its holt without a licence.

Eurasian otter vs sea otter

Eurasian otters along European coasts are sometimes called “sea otters”, but they are a different species. The true sea otter lives only in the North Pacific, spends almost its whole life in the sea and is about two to four times heavier. Eurasian otters rest, breed and groom on land. For the full comparison, see sea otter vs river otter.