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Grey seals (Photo: Markus Vetemaa)
Grey seals (Photo: Markus Vetemaa)
The grey seal is the largest of the three Baltic seal species: adult males may reach over three metres in length and 300 kg in weight. 

There is a great variety in coat coloration and shading of grey seals. Males tend to have a dark brown-grey coat, sometimes nearly black, with a few light patches, while females are generally light grey-tan coloured, lighter on the front, with dark spots and patches. Adult males, and some older adult females to a lesser extent, have a recognisable long "Roman" nose with wide nostrils, giving the species its name "horsehead" in Canada and its Latin name that translates as "hooked-nose pig of the sea".

The grey seals reach sexual maturity in the age of 4-6 years. Females can live up to 35 years of age, males up to 25 years.

They feed mainly on Baltic herring, sprat, whitefish, cyprinids, viviparous blenny and flounder but also other fish species. The diet differs in different age classes and feeding areas. Grey seals are known to dive regularly to about 30-70 m while feeding. They can stay underwater for more than 20 minutes.

As active travellers, the grey seals inhabit the whole Baltic Sea. Their haul out areas are located mainly in the central and northern part of the sea. Differently from ringed seals, the grey seals are gregarious and gather together for breeding, moulting and hauling out at exposed areas.

It is mainly an offshore species, whose main haul out areas – low islets without vegetation or reefs -  are located far from shores and human settlements. They can be seen also in shallow coastal bays, river mouths and sometimes in harbours but mainly in spring and autumn when they are following fish moving to the spawning grounds.
The Grey Seal (Halichoerus grypus)
The main breeding season in the Baltic Sea is from February to March. Pupping in the Baltic Sea takes place mostly on drift ice although in warm winters when there is lack of ice the grey seals also give birth on small islands. There is usually one pup weighing 10-12 kg. The pup is born with a creamy-white woolly lanugo coat, which it will moult after 2-4 weeks for a shorter adult-like coat. The pup is nursed for about 18 days, gaining 30-40 kg in weight by the end of the nursing period. After weaning, the pup stays at the rookery until it has fully moulted, living off its blubber reserves. In about 1-4 weeks the pup eventually goes to sea to start feeding. The pups disperse in many different directions from the rookery and are known to wander widely - distances over 1,000 km are not uncommon.

The mating takes place towards the end of the nursing period. Generally the males enter the rookeries at about the time when the females start to pup and try to gain sole access to groups of females. The successful males are able to mate with 2-10 females. Neither lactating females nor dominant males feed during the breeding season, females usually for about 3 weeks and males sometimes for up to 6 weeks. After mating, the seals disperse and wander widely in order to feed, usually in the open sea. Grey seals in the Baltic Sea moult on land or ice from April-June.

Historically the grey seal has been very numerous in the Baltic Sea  - in the beginning of the 20th century the population was ca 80 000-100 000 animals - but as result of human activities (hunting, pollution) the number of grey seals decreased significantly, reaching the lowest level - ca 4000 animals - in 1970ies.

The grey seal is listed as a protected species under Annex II and Annex V of the European Community's Habitats Directive and several important sites for the species have been proposed in EC member countries as Special Areas of Conservation under the Directive. It is also protected by the Bern and Bonn Conventions and as endangered on the IUCN Red List.

Thanks to the protection measures and also due to the improved environmental status of the Baltic Sea, the Baltic population of the grey seal is now recovering fast - in 2008 there were about 23,000 individuals. Therefore also their hunting, which was banned throughout the Baltic Sea in 1988 by signatories to the Helsinki Convention, was recently re-opened in Finland and Sweden.
Population & Protection
Breeding