About the European Otter

Species: Lutra lutra (Linnaeus, 1758)
Genus: Lutra
Subfamily: Lutrinae
Family: Mustelidae
Superfamily: Arctoidea
Order: Carnivora
Superorder: Placentalia
Subclass: Theria
Class: Mammalia

The European otter is a freshwater otter, and is found in Europe and northern Africa as well as parts of Asia. They are said to very playful animals, and have been observed seeming to take great enjoyment from such pastimes as sliding down muddy banks and playing in the snow although some of this behaviour may also be entirely practical in terms of efficiency and economy of movement rather than real 'play'.

The diet of the European otter consists mainly of fish (about 75% in freshwater animals but this rises to around 85% in coastal dwelling otters) but it will also eat birds, insects, crustaceans and amphibians. It might occasionally also prey on other small mammals such as voles. In River otters research undertaken in the UK in the 1980s (Wise et al. 1981) indicates that otters eat fish of any size according to its availability but that the most common types taken are Trout, Eel, Roach and Perch but this will depend largely on the abundance of different species of prey.

Otters are uniquely adapted to aquatic life. Otters are part of the mustelid family, which also includes animals like weasels, stoats, ermines and North American Mink. Often sightings of Otters turn out to be mink which in some locations are more common.The otter has the basic mustelid shape of a long, slim body. However, it shows numerous adaptations to life in the water, such as webbed toes with well developed claws and a powerful, rudder-like tail that it uses to propel and steer itself through the water. Even its teeth have special adaptations. Whist the canines are used for gripping and slicing wriggling prey they also have small notched incisors which are thought to be used in grooming. The molars of river otters also reflect adaptions being much broader than in other carnivores, this is thought to reflect a compromise between slicing and crushing thus allowing them to tackle a wider range of prey from the soft flesh of slippery fish to the hard exoskeletons of molluscs and crustaceans.

Otters have well developed senses. Hearing is very well developed and is believed to be more important than smell for detecting danger. Their eye sight has also been adapted to work well in both air and water. This is achieved by the otter changing the shape of the lens to make it more spherical in water to account for the different refractive index of water. However in dim or turbid conditions vision is not so good so other senses play a more important role such as the arrangement of whiskers (vibrissae) on the face of the otter which help it locate prey in poor conditions and of course its very agile hands and fingers which it used to search through silt and mud.

European otters are strongly territorial and tend to live alone, avoiding contact with other otters except for reproduction. The range of an individual European otter varies between 1 – 25 miles (1 – 40 km) with the average range usually being around 11 miles (18 km). The size of an otter’s territory depends on the availability of food so can be much smaller if conditions allow. Male otters often have a much larger range than females their territories often crossing that of several females.

Heat regulation is a big issue for Otters. Without their thick pelts they would soon cool down in water. Even with it they need a very high metabolic rate to compensate for rapid heat loss, it is about 50% faster than most land animals of a similar size. Otters consequently spend a lot of time out of the water in order to dry their fur to ensure its insulating properties are maintained and to maintain their energy levels for the demanding task of hunting. They can dive for upto 2 minutes but they are naturally quite buoyant due to their think pelt which traps air making it hard work to submerge and to stay under water.

One of the main threats to the European otter is pollution and degradation of its aquatic habitat. Activities such as damming rivers, draining of wetlands, and vegetation removal along river banks can all have a significant negative impact on otter populations. Otters also suffer from food contamination caused by water-borne pollutants such as mercury, DDT/DDE, and others. These toxins can be absorbed by the fish otters feed upon. Otters that live close to coastal areas are also highly vulnerable to oil spills.

The population numbers of the European otter have declined due to these and other threats. Because of this population decline, the European otter has been categorised by the International Union for Conservation of Nature (IUCN) as Near Threatened, meaning that the species is likely to qualify for a threatened category in the near future. On the upside otter numbers in the UK have begun to increase due to a combination of better water management, less use of toxic chemicals and a reintroduction programme started in the 1980s.