Name
- English: Eastern Atlantic Harbour Seal, common seal
- Latin: Phoca vitulina vitulina
- Dutch: Europese zeehond, gewone zeehond
Family
Eastern Atlantic Harbour Seal
→ Harbour Seals
→ True Seals
| In average | Males | Females | Pups | |
|---|---|---|---|---|
| Length in meters | 1,50-1,80 | 1,20-1,50 | 0,70-0,90 | |
| Weight in kilogram | 55-130 | 45-105 | 9-11 | |
| Life expectancy in years | Max. 25 | Max. 35 | ||
| Number of animals nowadays | ||||
| Colour(s) | Grey, Brown with black spots | |||
| Habitat | Eastern part of the Atlantic Ocean, Baltic Sea and Wadden Sea: from Norway to France (Bretagne) |
Additional information
The Eastern Atlantic harbour seal belongs to the subfamily of harbour seals, which is probably the most wide-ranging subfamily of pinnipeds . There are five species included in the harbour seal family . The Eastern Atlantic harbour seal is very close related to the Western Atlantic harbour seal , the Pacific harbour seal , the insular seal and the Ungava seal.
harbour seals have a quite fat body and a narrow-pinched head. The nostrils are narrow and show a typical V-shape. The eyes are quite big and close set to each other. The seals' belly always is lighter coloured than its back. It is difficult to distinguish males from females. The seals' back usally shows varied spots.
The Eastern Atlantic harbour seals' fur colour varies from grey to brown. The animals have black spots on their body. The females reach sexual maturity in 3 of 4 years of age. Males reach sexual maturity at six years of age. These seals eat a variety of fish: place, sole, whiting, herring, inkfish, shrimps, mussels.
Eastern Atlantic harbour seals live along the western coast of Europe from Spitsbergen (Norway) to Bretagne (France) including the Kattegat and Skagerrak, Svalbard, Iceland, the Biritsh Isles and in southwestern Baltic sea. The seals like to haul out on flats that are uncovered at low tide. These seals are also seen in estuaries. Eastern Atlantic harbour seals spent about 80 percent of their lives in the water.
Unlike most other pinnipeds harbour seals are generally solitary. They rarely interact with one another. When hauling out they keep spaces of 1 meter or more to each other. These seals are not highly communicative, but when feel threatened they may respond by lunging, scratching, snorting, growling or other aggressive ways of communication.
Although harbour seals are quite solitary they mostly haul out in small groups. The reason is probably for protection from predators. The seals haul out to breed, moult and rest. They haul out on rocky shores, sand beaches, reefs, piers or ice.
Moult takes place in July and August. During the moulting period the seals' metabolism is reduced. They do not eat very much and so conserve energy usually expelled finding food.
During the summer time Eastern Atlantic harbour seals come together to give birth and nurse their young. Unlike most seal pups the pups moult in their mother's uterus. They are not born with the white pup fur, but have the characteristics of full grown harbour seals. Pups are weaned after 4 up to 6 weeks. Due to the high percentage of fat in the mother's milk (45%) the pups double their weight by the time they are weaned. The females give birth on flats which get flooded at high tide. From birth on the pups immediately can swim and dive. This is a must, as the flats they are born on are flooded at each high tide. After 2 days the pups can remain undermerged for about 2 minutes. The pups use to leave their place of birth to explore their new habitat.
Mating takes place after weaning. Unlike other mammalians the ovum becomes implantated in the wall of the uterus approximately three months after breeding. This makes it possible to both nurse pups and breed in the short period the seals are together.
During the mating season male seals can become very aggressive. They may fight each other when competing for a female. The males also display aquatic performances and vocalizations to attrack a female. Due to their activities male seals can lose up to 25 percent of their body weight.
Natural predators of the harbour seals are killer whales, sharks and polar bears.
Harbour seals usually remain in the vicinity of their traditional breeding area all year round. Due to this restricted range the viability of local harbour seal populations can be particular at risk. For instance the local harbour seal population in the Ontario Lake (Canada) has disappeared in the early 1980's, probably exterminated by human activities. The populations of harbour seals in Greenland (Western Atlantic harbour seal), the Baltic Sea (Eastern Atlantic harbour seal and Western Atlantic harbour seal) and the population in Hokkaido (Insular seal) are cureently under severe threat. The population in the Gulf of Alaska (Pacific harbour seal) has drastically declined in some areas within the last 20 to 30 years.
In some areas (Norway, Iceland...) people still hunt the Eastern Atlantic harbour seal. Hunting these seals is forbidden in The Netherlands since 1962. In some countires (e.g. the United Kingdom) fisher man may shoot seals, that became entangled or drown in fhsing netts, to protect their fisheries.
Hunting and water pollution with PCBS decreased the population of Eastern Atlantic harbour seals in the waters of The Netherlands drastically. In 1975 there were less than 500 seals of this species in the waters of The Netherlands, whereas there were about 3.000 of them once before. After 1975 the population recovered slowly. In 1987 about 1.000 seals were counted in the Dutch Wadden Sea. But in 1988 a viral epizootic break out and killed many seals. In 1989 only 500 seals were left in the Wadden Sea. From then on the population recovers again. In 1993 more than 1.070 Eastern harbour seals were counted.
Fishing nets (especially non-biodegradable nets), plastic wrapping bands and marine debris and threats for harbour seals. Pollutants decrease the productivity and may cause premature parturition. Oil and hydrocarbon are also threathening the harbour seal population. Some seals have been killed by being trapped in the intake pipes of power plants.