The presence of the Eurasian otter (Lutra lutra) is easiest to notice in the winter, when it leaves tracks by the edge of the ice. In mild winters, it roams extensively on the thin ice, looking for places by the edges of the reed beds from where it can dive in for a swim.
The first recorded sighting of an Eurasian otter in Helsinki was made in the spring of 1998 in the Vanhankaupunginkoski rapids. In the 21set century, the Eurasian otter has become an established resident of Vanhankaupunginlahti, and in the summer, otters can also be seen swimming in the ponds in Pornaistenniemi. The Eurasian otter feeds primarily on fish, but it can also eat frogs, small rodents and waterfowl.