UK Seals

Two species of seal are permanent residents in Britain – the grey seal (Halichoerus grypus) and the common, or harbour, seal (Phoca vitulina). Both spend much of their time at sea, but come ashore to breed and moult. They can often be seen basking peacefully on beaches, sandbanks or rocks, and, being curious creatures, sometimes swim up to boats to see what is going on.

Common seal

Scientific name: Phoca vitulina
Common names: Harbor seal or Harbour seal

Common seals, as the name suggests, are very common, especially in the waters of the north Atlantic and north Pacific Oceans. They are the most widespread of the pinniped family, with the UK boasting five percent of the worlds population. Mostly solitary animals, small groups do form when they haul-out onto rocky shores and beaches to bask, mate and moult. At sea common seals

have much to fear from killer whales and great white sharks. Common seals don't chew their food, it is just torn into chunks or even swallowed whole.

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 suck.

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.

Common seal males reach sexual maturity earlier than grey seals, and are ready to mate between three to six years of age. They are usually strong enough to mate when they are about six or seven. Once mating is over, the bulls return to sea to feed, hauling out a few weeks later to moult. Like females, they haul out occasionally to rest between fishing forays.

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.

Grey seals

Scientific name: Halichoerus grypus meaning "hooked-nosed sea pig"

Grey seals are the largest living carnivore in Britain with around 36 per cent of the world population found around the UK coast. They also live around Iceland, northern Scandinavia and the Baltic Sea, and southeast Canada. Males grow to about 2.3 metres (7.5 feet), while females are smaller and average 1.8 metres (5.9 feet) in length.

The name ‘grey’ seal is rather misleading, since there is a lot of variation in colour from almost black bulls to creamy white cows and the gorgeous silky white fur of new-born pups. Usually both sexes have a lighter colouring on their stomachs than on their backs.

Grey seals breed from September to December around British shores. The female gives birth to a single pup on a shore (known as a rookery) crowded with hundreds of other seals. Grey seal pups weigh about 14kg at birth and have soft white fur. They remain on land where they suck from their mother for 18-21 days. A female's milk contains up to 60% fat, with pups gaining about 2kg in weight each day

The pup grows quickly on its mother's rich milk, and she abandons her offspring after three weeks, ready to mate again. The bulls (males) haul themselves onto the shore and fight each other to establish territories. The more mature, experienced bull usually wins any fight and he mates with all the females on his part of the beach.

After mating, the female returns to the sea leaving her pup on the beach, but the fertilised egg does not start developing until much later so the birth will be at the same time the following year. The pup will finally be driven into the sea by hunger where it will now have to fend for its self.

Grey seal males become sexually mature at about six years of age, although he is usually far too small to successfully compete with the dominant bulls, forcing him to prowl in the shallows, or fight his way onto a patch of land that no other bull wants until he is big and strong enough to be able to win his battles for a breeding territory. Most grey seals are more than 10 years of age before they can maintain a position on the breeding grounds long enough to mate.

Grey seals were the first mammals to be protected by modern legislation - the Grey Seals Protection Act of 1914. Today, the Conservation of Seals Act (1970) protects them during a closed season from 1st September to 31st December, although seals causing damage at fish nets can still be killed. The law also allows complete protection to be given. For instance, grey seals in England and Wales, though not Scotland, were fully protected following the outbreak of phocine distemper in 1988.

Recent research indicates that grey seals eat large quantities of sand eels, which are caught for use in fish meal but not for human consumption. Salmon does not appear to be an important part of the seal's diet, although other commercially important fish like cod are taken.

The Grey Seal Enigma

Grey seals have long been a common sight on the shores of Scotland - but now scientists are wondering whether a secret seal sanctuary somewhere on the South coast could be helping them breed in the South East. We're not talking about a man-made enclosure - but perhaps a natural cove or secluded bay where grey seal pups are born and learn to swim before heading out to sea.

Brett Lewis is one of a handful of scientists researching the number of grey seals in the region and along with an army of volunteers he's been monitoring the population along the coast since 1993.

There are relatively few grey seals on the English Channel coast, there's a colony at Ramsgate that we know about and probably two individuals in the Solent area near Chichester Harbour," he says.

"They can go off on their own and give birth in caves where it's nice and secure and there's no predators but I think it's probably very rare for large numbers of grey seals to be breeding in the English Channel.

"Obviously they are being born but I would imagine it is in low numbers and that the high numbers come from elsewhere, possibly Donna Nook in Lincolnshire, and are swimming down to Kent.

If they were breeding here regularly I think someone would have found them by now."

Seal Facts

The common seal is in fact less common in British waters than the grey seal, at about 55,000 compared with around 120,000 grey seals, but around Ireland the two species are more equally represented: about 3,000 common seals and 4,000 grey seals.

Both grey and common seals eat a variety of prey – fish, shellfish, squid and octopus. They are opportunistic feeders, and will eat whatever is available, including cod, herring, flounder, sculpin, salmon, mackerel, sandeel, shrimp and whelk. Their fishy diet often brings them into conflict with fishermen.

They are covered in fur could Pelage which is short and thick, consisting of coarse guard hairs and finer, denser underhairs.  Its pattern is similar to a human's fingerprint; unique to the individual.  The patterns range from light coats (white, silver, light gray) with dark rings or spots, to medium coats (beige, brown) with light or dark rings, or dark coats (dark gray, black) with light rings.

The hair itself provides no insulation.  Instead, glands in the skin secrete oils which protect the coat.  Because of this, harbor seals must molt annually.  Molting occurs after every breeding season.

In the arctic, pups will be born with a white coat called the lanugo and will molt this coat shortly after birth.  In regions where ice is not present, this coat will be shed in-utero such as our common seals. 

If they survive the dangers of being a pup, seals are relatively long-lived animals. Both species often live longer than 30 years and one female grey seal in the Shetland Islands was known to be 46 years old. Since many seals die at sea, it is difficult to know the major causes of death. Diseases caused by parasites, pollution, and drowning in fishing nets are some of the main reasons.

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.