Saimaa ringed seal

The Saimaa ringed seal ("Pusa hispida saimensis") is a subspecies of ringed seal ("Pusa hispida"). Usually seals live in the sea, but Saimaa ringed seals live in Lake Saimaa in Finland. There are only 320 Saimaa ringed seals in the world. They are among the most endangered seals in the world. 
After the last ice age was over, dry land was rising slowly. This isolated Lake Saimaa from the sea. Some seals were also isolated in Saimaa. Their successors become Saimaa ringed seals. 
Appearance.
An adult Saimaa ringed seal is between long and weighs between . Usually male seals are larger than females. Their colour is dark gray, with circular white ring patterns.
Reproduction.
Saimaa ringed seals give birth towards the end of February. They dig a nest in snow on top of lake ice. Snow nest gives shelter for young seal pups. If there is not enough snow, young seals do not survive. In 2010s, volunteers help seals by building artificial piles of snow on lake ice. Studies by the University of Eastern Finland showed the ringed seals would nest in man-made snowdrifts the same as natural snowdrifts.
Other websites.
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