Fine spot-patterned grey or brown fur; rounded head with no ears visible; 'V' shaped nostrils.
Head/body length: 140-185cm including flippers of about 20cm.
Weight: 8-16kg at birth; up to 130kg in adults.
Common seals feed at sea but regularly haul out on to rocky shores or inter-tidal sandbanks to rest, or to give birth and to suckle their pups. The most important haul-out areas are around the coast of Scotland, particularly in the Hebrides, Orkney and Shetland, and on the east coast of England in the Wash. Young seals may travel distances of several hundred kilometres but adults appear to remain faithful to favoured haul-out areas from year to year. The particular sites used may, however, vary with the seasons. Common seals travel up to 50km from haul-out sites to feed and may remain at sea for several days. Here they spend time diving, staying underwater for up to 10 minutes, and reaching depths of at least 50 metres.
The way in which common seals hunt is poorly understood, but they are known to eat a wide variety of fish, including herring, sandeels, whiting and flatfish. Shrimps and squid are also sometimes eaten.
Females give birth to a single pup in June or July each year. Pups are very well developed at birth and can swim and dive when just a few hours old. This enables common seals to breed in estuaries where sand-banks are exposed for only part of the day. Mothers feed their young with an extremely rich milk and pups grow rapidly, doubling their birth weight during the three or four weeks that they suckle. Males play no part in the rearing of pups but spend much of this period fighting amongst themselves in the water, attempting to increase their chances of breeding. Soon after breeding, common seals undergo the annual moult of their fur, during which they spend much of their time ashore.
A female common seal can reach 30 years of age, but males are unlikely to survive beyond 20 years.
The Conservation of Seals Act (1970) protects common seals during their breeding season, although seals causing damage to fishing gear, or taking fish from nets, may be killed under licence. The Act also allows seals to be fully protected when required. Following the 1988 seal plague, common seals in England, Wales and Scotland were given year-round protection.
Common seal pups used to be hunted for their skins, particularly in Shetland and in the Wash. This probably over-exploited populations in some areas and led to the seals being protected. There is continuing controversy over the impact that seals might have on fish stocks although, in Britain, grey seals have received more blame from fishermen than common seals.
In 1988 over 17000 common seals died during a disease outbreak in the North Sea. Seals on the coast of Denmark and Holland were worst affected. About 3000 deaths occurred in the British population. The disease is now known to be caused by the newly discovered phocine distemper virus, but its origin is unknown. Similar epidemics have periodically affected common seals in the past, suggesting that the 1988 plague was a natural phenomenon and that little could have been done to prevent it.
Seals are at the top of the food chain and so tend to accumulate pollutants such as heavy metals and polychlorinated biphenyls (PCBs) which are persistent in the environment. Female common seals feeding on fish with high levels of PCBs may fail to breed and pollution could thus hinder the recovery of some populations which have been reduced by disease.
What do I do if I find an injured or diseased seal?
In England or Wales telephone the RSPCA (0345 888999) and in Scotland telephone the local SSPCA office. Do not go too close to the seal - it may bite! Avoid disturbing seal pups as this could result in the mother abandoning them.
Do seals swim up rivers?
Yes, but this is unusual. Seals have been seen in the Thames in central London.
Where can I go to watch seals?
Boat trips can be taken to see seals at Blakeney Point, in Norfolk and at a number of haul-out areas in Scotland. They can often be observed from land around much of the Scottish coast.