The otter is Europe's largest member of the marten family. It has a slender, elongated body, with short legs and reaches a mass of up to 11 kilograms.
The otter (Lutra lutra) is a carnivore belonging to the marten family (Mustelidae). It is Europe's largest marten. It has a slender, elongated body with short legs. The body can be from 100 to 120 cm in length, and its flat tail can be 35 to 55 cm long. It can reach a mass of up to 11 kg.
The fur on its back is dark brown, and somewhat lighter on the neck, chest and belly. It is adapted for life in the water, including the sea. It has small ears with a valve that closes off the entrance to the hearing canal, and webbed feet. The otter has a thick layer of fat under the skin, and its thick, fatty fur protects it from the cold water. It has an excellent sense of smell, and the tips of its whiskers are very sensitive to touch, helping it to find food in murky water. Its eyes are position near the top of its head, and it can see both above and below the water's surface when it swims just under the surface, even though its sense of sight and hearing are less developed. It calls out with a quiet but clear whistle, and also snorts, squeals and growls. It builds its den, with an entrance under water, near calm river banks covered with dense vegetation, or under old trees with massive submerged roots. It is active at dusk and at night. It feeds on fish, crabs, shellfish, frogs, small mammals and other aquatic animals. It can live from 12 to 20 years. All large carnivores are the natural enemies of the otter.
Today, this species is primarily threatened due to the destruction of favourable habitats, water pollution, disturbances and poaching. In Croatia, it has been protected since 1972 by the Act on the Protection of Rare and Threatened Species. The otter was included in the Red Book of Threatened Animal Species in Croatia (Mammals), and is also included in endangered species list at the European level. The Ordinance on damage compensation from 1995 prescribes a fine of HRK 30,000 for killing an otter.