There are dozens of different types of seal right across the planet, but there’s one thing they have in common – they’re all essentially saltwater creatures … all, that is, except one.

The Baikal seal or nerpa (Pusa sibirica) is a species of earless seal endemic to Lake Baikal in Siberia – the deepest lake in the world. One of the smallest true seals, it’s related to the Arctic ringed seal, and the only one to live exclusively in fresh water. It remains a mystery how the seals originally came to Lake Baikal, hundreds of kilometres from any ocean.

Recent estimates suggest that there are 80 000-100 000 animals living in Lake Baikal. They typically grow to 1.1–1.4 m in length and weigh 63 to 70 kg. They have a uniform, steely-grey coat on their backs and fur with a yellowish tinge on their abdomens. New-borns have coats of white, silky fur which is quickly shed and exchanged for a darker coat, much like that of the adults. The seals are estimated to have inhabited Lake Baikal for some two million years.

In winter, Lake Baikal is almost completely covered in ice, and in early spring, pregnant females build ice dens in which a single pup is usually born. In late winter and spring, both sexes haul themselves out and begin to moult their coat from the previous year, which is replaced with new fur. During this time, they refrain from eating and enter a lethargic state, during which time they often die of overheating from lying on the ice too long in the sun.

The only known natural predator of adult Baikal seals is the brown bear, although this is not believed to occur frequently. The pups are typically hidden in a den, but can fall prey to smaller land predators such as red fox, sable and white-tailed eagle.

Baikal seals can dive up to depths of 400 m and stay down for more than 40 minutes. However, most dives are much shorter, although they can stay underwater for up to 70 minutes if frightened or to escape danger. Interestingly, they can live to over 50 years old – exceptionally old for a seal.

Spring and summer are probably the best time to see the seals, when groups as large as 500 can form on the ice floes and shores of Lake Baikal. If you’d like to see them for yourself, probably the best option is to join one of our Trans-Siberian railway tours – see the website for details.