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Ringed seal pup on ice (Photo: Ivar Jussi)
The Ringed Seal (Phoca hispida botnica)
The Baltic ringed seal is the smallest seal in the world – its body length is 130-150 cm and weight 50-60 kg. The weight is varying depending on season, in autumn it can be up to 100 kg.
Characteristic for the ringed seal is the pattern of its fur: light ring-shaped blots on the back and dark ring-shaped blots on the belly.
The ringed seals reach the sexual maturity in the age of 3-6 years and can live up to 40 years of age, usually 20 – 25 years.
Baltic ringed seals feed mainly on pelagic fish such as herring and smelt, but also bottom-dwelling species like sculpin and viviparous blenny. Crustaceans also form part of their diet, especially isopods during the winter.
The ringed seals inhabit mainly northern parts of the Baltic Sea with three subpopulations in the Bothnian Bay, the Gulf of Finland and West-Estonian Archipelago. In the ice-free period they usually feeding on deep waters, between foraging trips associate in small social groups (up to ca 10 animals) gathering on certain reefs and underwater rocks.
During the winter the seals are found alone or in pairs, spread out in the ice fields, and are often aggressive to other individuals. They look for certain ice types (pack ice and ice ridges) where they can build nests and systems of breathing holes. Each female ringed seal has several breathing holes in the ice and moves between them in case of disturbance. They can keep their breathing holes open even when ice is several meters thick. Ice is very important for this arctic species as it breeds only on ice, differently from the grey seal whose pups can be born also on land.
The pups are born in lairs on the pack ice in late February - early March. Availability of the ice is absolutely essential for survival of the ringed seal pups, otherwise they will be born into water and die. Usually there is one pup weighing ca 4,5 kg. The fat content of the seal mother’s milk is ca 38%, so after the nursing period lasting 39 days the weight of the seal pup is already ca 20 kg.
The newborn ringed seals are very active. While grey seal pups are mainly immobile, the ringed seal pups spend 50% of the time in water and can dive for up to 12 minutes.
The ringed seal has been historically very numerous species in the Baltic Sea, inhabiting all its the northern and central parts having ice-cover in winter. It is estimated that there were up to 200,000 Baltic ringed seals at the start of the 20th century. Intensive hunting and pollution however have reduced their numbers considerably. Now hunting of this species is banned throughout the Baltic Sea. Currently approximately 6500 – 8000 ringed seals are living here.
The Baltic ringed seal is listed as vulnerable on the IUCN Red List and protected by the Bern Convention and the EU Habitats Directive as well as through national legislation by various countries within its range.