MarLIN

information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Common or Harbour seal (Phoca vitulina)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.

Summary

Description

Common seals have a rounded head with eyes equidistant between the nose and the ears. The nostril slits form a characteristic 'v' shape when viewed from the front. Adult common seals grow up to 1.2 to 2 metres long, and weigh around 65-140 kg. Males are slightly bigger than females. The coat is grey to brownish-grey with a uniform pattern of small darker spots, although the pattern varies geographically. Individuals may live for 20-30 years (SMRU, 2004).

Recorded distribution in Britain and Ireland

The species is fairly evenly distributed around the coasts of Great Britain and Ireland, except for regions where there are extensive cliffs (Hewer, 1974). It is most commonly seen on the east coast of England, western Scotland and the northern isles.

Global distribution

Widely distributed in the North Atlantic and North Pacific from the subtropics to the Arctic. Common on Canadian and USA coasts. In Canada there are populations that live throughout the year in freshwater.

Habitat

The common seal lives mainly along shorelines and in estuaries. It is commonly seen resting on sandbanks, easily accessible beaches, reefs and protected tidal rocks.

Depth range

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Identifying features

  • Lacking external ear flaps.
  • Colouration variable but generally coat is grey or brownish grey with small spots.
  • Head rounded with nostrils forming 'v' shape when animal viewed head on.
  • Eyes equidistant between ear and nose.
  • 3 front teeth, one eye tooth and 5 cheek teeth in each half of upper jaw.
  • 2 front teeth, one eye tooth and 5 cheek teeth in each half of lower jaw.

Additional information

May be confused with the grey seal (Halichoerus grypus) that has a much longer muzzle and their nostril slits are nearly parallel.

Seals are highly adapted to live in water. Their limbs are modified into flippers and they have streamlined bodies. Phoca vitulina can dive to 450 m and remain submerged for up to 30 minutes. The common seal is a strong swimmer and can be seen leaping completely out of the water (porpoising) (Nowak, 2003). Only the head is usually seen when the seal is in water. As well as being fur-coated they have a thick layer of subcutaneous fat or blubber. This keeps them warm and enhances streamlining (SMRU, 2004). Seals are warm-blooded air-breathing mammals but spend a considerable amount of time below the water surface. Common seals give birth to pups in June and July and moult in August. The main threat to seals in the UK and Ireland is organochlorine compounds that may interfere with reproduction (SMRU, 2004).

The Common or harbour seal has been reported as non-migratory and littoral in distribution and as exhibiting a diurnal haul-out pattern (Evans & Raga, 2001). Common seals in Europe belong to a distinct sub-species. Britain holds around 40% of the world population of the European sub-species (Duck & Thompson, 2003).

The Conservation of Seals Act, 1970, provides a closed season for the Common seal during its pupping season. During this time, it is illegal to kill or take seals without a licence. There is also provision for giving complete protection to seals at al times, if neccesary. During the close season, a license is required to handle seals unless they are sick or injured (SMRU, 2004). The Baltic and Wadden Sea populations are listed under the Bonn Convention (Appendix II).

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Further information sources

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Bibliography

  1. Duck, C.D. & Thompson, D., 2003. The status of British Common Seal Populations. In Scientific Advice on Matters Related to the Management of Seal Populations. Special Committee on Seals (SCOS)., Sea Mammal Research Unit, University of St. Andrews., http://smub.st-and.ac.uk\pdfs\SCOS%2003_v7.pdf

  2. Evans, P.G.H. & Raga, J. A. (ed.), 2001. Marine mammals: biology and conservation New York: Kluwer Academic / Plenum Publishers

  3. Hewer, H.R. 1974. British Seals. London : Collins

  4. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  5. Kinze, C. C., 2002. Photographic Guide to the Marine Mammals of the North Atlantic. Oxford: Oxford University Press.

  6. Nowak, R.M., 2003. Walker's Marine Mammals of the World. Baltimore: John Hopkins University Press.

  7. SMRU (Sea Mammal Research Unit), 2004. Seals in Britain http://smub.st-and.ac.uk/GeneralInterest.htm/seals.htm, 2004-07-24

Citation

This review can be cited as:

Oakley, J.A. 2008. Phoca vitulina Common or Harbour seal. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/species/detail/2088

Last Updated: 17/04/2008