The Eurasian otter is a small animal that lives on the banks of rivers and lakes, and only where the water is very clean. It is considered one of the rarest and most endangered mammals in the continent. It is an important health indicator of mountain water so it is strictly protected by all the countries of the EU. The otter's diet consists 80% of fish, but also of amphibians, reptiles (water snakes), invertebrates (mostly crabs), birds and small mammals. According to estimations, in Greece exists one of the densest and greatly expanded otter populations. In central Greece occurs a small splitting of the populations, while some isolated populations appear in Corfu and in Evia.