Project co-financed by the EEA Financial Mechanism 2009-2014

Grey seal


The grey seal is the largest seal in the Baltic Sea. Females grow up to 2 meters in length with weight up to 200 kg. Males are larger and grow up to 3 meters in length, reaching a weight of 300 kg. The fur of seals is diverse in terms of coloring, from dark brown to light grey. Males are always uniformly dark, while females have light grey backs and whitish bellies with dark spots. The snout of adult males is elongated, resembling a snout of the dog.

Seals conduct amphibious lifestyle and they are herd animals at the same time. Seals can rest for many hours without moving, just basking in the sun. They are great swimmers, though they move awkwardly ashore. They swim on their bellies and on their backs, as well as they dive frequently and in case of foraging they can dive to a depth of over 200 meters while under water for up to 20 minutes. They are able to sleep both on the land and by floating on the surface of the water, and even under water. The seal ascents for breath of air almost unconsciously, without interrupting the sleep.  The grey seal is a migratory species. Juveniles take solitary trips of up to a thousand kilometers.

Seals eat mainly fish, which is their dominant food in a given place and at a given moment, as well as clams and crustaceans. One specimen can eat from 5 to 9 kg of fish per day, mainly herrings, sprats, sows and also cod and salmon to a lesser extent.

Seals join the mating season most commonly in March, after the release of progeny. Female seals reach sexual maturity at the age of 4-7, whereas males at the age of 6. Males take mating fights and the strongest of them choose the most suitable territories, while gathering harems of females around him. After the insemination, the so called pre-pregnancy begins with embryo waiting approx. 3 months, and then it embeds itself in the wall of the uterus. After another nine months of proper pregnancy a small seal is born. Grey seals of the Baltic Sea are born both on the ice, as on the shore.   Young seals are born with an average of 75 cm in length and weigh 6-10 kilograms. Their baby fur (lanugo) is creamy-white and they change it after two or three weeks of life. During this time, the seal pup feeds on its mother fat milk, gathering energy stocks for the first weeks of its independent life. Then, the mother leaves and the pup stays on shore for the next two or three weeks. Grey seals can live up to 45-50 years.

The main threat to grey seals is the lack of peace in places of their natural habitat. The intense tourist traffic causes a displacement of seals from their natural habitat and their breeding sites. Those places on the Polish coast are: Mewia Łacha, Ryf Mew and Cypel Helski. The beaches of national parks due to much smaller tourist traffic in those areas can become habitats of the seal. A common cause of death of seals is an accidental entanglement in the fishing nets set up for fishery, in which mostly juveniles are being caught. Another danger is the pollution which manifests itself mainly by concentration of halogenated compounds (PCBs) in the tissues of grey seals causing pathological changes of female reproductive organs. As a result of these diseases, seals may not get pregnant, fetuses are sick, there are miscarriages and the younglings are often stillborn.

At the end of the nineteenth century the number of grey seals in the section of Gdansk Pomerania and East Prussia was estimated to be about 1,000 individuals. Being as common, they were treated as pests, damaging nets and competing with fishermen in fishery. That was one of the reasons why they were commonly hunted in the Gulf of Gdańsk. In the years 1912-1919 almost 520 of seals were killed in the waters.

The size of the Baltic grey seal population is currently estimated at approx. 30 thousand of individuals which represents only 30% of natural population state from a hundred years ago.

The largest populations of grey seals are present along the western coast of Estonia, the south-west coast of Finland and northern Sweden. On the south coast of the Baltic Sea (Germany, Poland, Russia and Lithuania) the animals were exterminated by the man before even they were hit by the effects of environmental pollution. Today only individuals would arrive here from other parts of the Baltic Sea.

Based on information from Institute of Marine Station of Oceanography at the University of Gdańsk (IMSOUG) and WWF Poland.

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