Facts about the Eurasian Otter
The Eurasian otter is a semiaquatic mammal that belongs to the Mustelidae family of carnivorous mammals; along with ferrets, badgers and wolverines. Also known as the European otter, Eurasian river otter, Old World otter, and the elusive common otter. It is native to Eurasia and is the most widely distributed of all thirteen otter species.
Key identification features of the Eurasian otter
The Eurasian otter has a long slender body, short legs and a long thick tail that tapers off to a point. They have a broad flat head with small eyes and small rounded ears. Their coat is dark brown on their backs and cream on their underside and throat. An otter’s coat has two fur types, a waterproof outer layer and an inner layer for insulation. Males otters are larger and heavier than females with an average adult male measuring 130cm from head to tail and the female measuring 115cm from head to tail. Fully grown males can weigh up to 11kg while females normally weigh up to 7kg. Otters have webbed and clawed feet which allows them to dive for prey. Otters communicate with whistling sounds. Eurasian otters are very elusive, hence the ‘elusive’ moniker they’ve been given, so their presence is often identified by spraints, which is another term for their droppings. Eurasian otters use spraints to mark their territory by leaving them regularly in the same place, and these spraints can be used to identify age, sex and territory range.
Habitat of the Euarsian otter
The Eurasian otter can live near a variety of unpolluted water bodies, such as; streams, lakes, rivers, swamps, canals, ponds and along coastlines. However, when living along the coastline, Eurasian otters need access to freshwater to clean their fur of salt in order to maintain their insulating abilities. These otters can sometimes be called sea otters, but should not be confused with true sea otters, (Enhydra lutris). Eurasian otters require aquatic environments that have nearby vegetation or rock cover. The underground dens used by otters are called holts and aboveground nests are called couches, several of which can exist within one otter’s territory along a home range parallel to the waterbody. They build their nests on land, either along a bank or among a tree’s root system, or by using existing shelters such as caves or the vacated dens of other animals such as foxes or rabbits. The dens are lined with dried vegetation and can have multiple entrance points, some of which can be accessed from underwater.
Feeding habits of the Eurasian otter
The majority of the Eurasian otter’s diet comes from the water. They are nocturnal carnivorous hunters, which means they sleep during the day and are most active at night, and their diet consists of different types of meat. They eat a lot of fish and crabs, and sometimes other shellfish. Their diet is dependent on the local abundance of prey items and seasonal availability. Occupants of freshwater habitats typically consume fish such as salmon, trout, and pike. They will also hunt on land and consume frogs, small mammals and some waterfowl species. Otters in coastal areas will hunt crab, eel, molluscs and sea urchins. Foraging for food takes up a lot of their time and they will usually consume more than two pounds of food daily.
Reproductive life cycle of the Eurasian otter
For the most part, Eurasian otters live alone, except when a mother has cubs. In Ireland, otters can breed year-round, however, mating usually occurs in spring and summer. The male otter will remain with the female for up to two weeks after a successful courtship, which is not typical for other members of the Mustelidae family. Gestation lasts about two months and two to three cubs are born on average.
The cubs are nursed by the mother otter until they are able swimmers which usually occurs at fifteen weeks and will remain with the mother for up to a year. Survival rates are higher when the cubs are born in the summer months and in Ireland, they can expect to live for up to five years on average in the wild. In other countries, the Eurasian otter can live up to seventeen years in the wild, with some individuals in captivity living up to 22 years.
Current distribution and conservation status of the Eurasian otter
The Eurasian otter is native to 81 countries and its distribution ranges from Eastern China and Russia to as far west as Ireland. The Eurasian otter is classified as ‘Near Threatened’ on the IUCN Red List. Its declining population has led to a high rate of concern, which means it could be threatened in the future. In 2007, proposals were put forward to downgrade the status to ‘Least Concern’ on the basis that populations appeared to be recovering in Europe. However, the scale and speed of this population recovery has been largely exaggerated in the media. The main threats faced by Eurasian otters today are hunting, habitat loss and pollution (particularly by pesticides).
- Eurasian otters are agile swimmers and can only hold their breath for up to forty seconds when diving for prey. They can dive as deep as fourteen metres to reach their prey.
- Eurasian otters went extinct in the Netherlands in 1989 and a reintroduction programme in 2002 saw thirty otters (ten males and twenty females) reintroduced to a lowland peat marsh. The programme saw fifty-four offspring produced: twenty-three females and thirty-one males. The main cause of mortality was traffic accidents.
- Eurasian otters have long stiff vibrissae, or whiskers, protruding from their snout that they use as sensing organs underwater to monitor prey movement.
In the case of Eurasian otters predating on the common frog, Rana temporaria, it has been observed that they will only skin and consume the hind legs of the frogs and ignore the upper body to avoid the paratoid glands, which exudes a powerful toxin, that is situated behind the frog’s eyes.
By Aoife Cahill