The Grey Seal

    Halichoerus Grypus

    Atlantic Grey Seals in Britain number about 125,000, and account for around 40% of the world population. Off the Welsh coast there is a stable population of approx 6,000.

    Britain is home to two types of seal. Grey seals and the Common or Harbour seal. they can be told apart by their size, colour and shape of their face.

    Grey seals are larger and darker in colour with a distinct 'Roman' shaped nose, with parallel nostrils. The females (Cows) have unique blotches on the coats (Pelage), and these markings are used to identify individual females.
    Female Grey seals are smaller than the males (Bulls). The females grow to between 1.6 to 2 meters in length, and weigh up to 250 kg.
    Bull seals can grow over 2 meters, and can weigh up to 350 kg.

    Seals were the first mammals to be protected by law under the Grey Seals Protection Act of 1914. Atlantic Grey seals are protected under the Conservation of Seals Act 1970: Wildlife & Countryside Act 1981.

    Cwmtydu is in the Cardigan Bay Special Area of Conservation (SAC) protects the wildlife found in around 1000km2 of sea.
    The protection of these seals is of international importance.

    It is an offence to recklessly disturb these animals. 

    Grey Seals come ashore at various times; at 'Haul outs' between feeding or tides, at spring to moult, and in the autumn to give birth and mate.

    They are creatures of habit, and will return to the same sites every year.The females return to the same beaches to give birth to a single white-coated pup. They will stay together for a relatively short time. She will suckle the pup on fat rich milk for about 18 days. During this time the pup will triple it's birth weight, and the female will lose around 1/2 of her body fat as she doesn't feed herself. The female will then leave the pup to fend for itself. She will mate with the dominant Bull, and then head out to sea to feed.

    It's vital for the survival of the pup that there is no disturbance during these few weeks. The females depend on scent to find their pups, and if they feel threatened, they could abandon the pup. The pups can miss out on vital feeds if females can't return to feed, and they are at risk of being swept out to sea, where they can be lost.

    Dogs are especially a threat to both mother and pup. 

    Females do not always have a pup. It is thought that if they have put a lot of effort into raising the pup that their body can't conceive. They are also one of the mammals that have a 'suspended' pregnancy. They will mate shortly after giving birth and will delay implantation of the embryo for about three months. The true pregnancy is about eight and a half months. This delay ensures the pup is born the same time of year.

    Seals give birth on land. 

    Grey seals spend most of their time at sea, and are at their element there. They are opportunist feeders. Sand eels, Cod and Herring are important foods, but they will take whatever is available, and this has led to conflict with fishermen.

    Seals can capable of holding their breath when diving. Usual dives last about eight minutes. They are able to work without oxygen, by building up an 'oxygen debt'. Seals have a complex set of blood vessels, which under pressure can serve the brain alone, which must have a constant supply of oxygen.
    They can drop their heartbeat down to 40 beats or less per minute. Their muscles also contain large amounts of Myoglobin, a compound capable of carrying oxygen. This all goes to prepare seals to dive without the need to breathe for some time.

    Seals rest by hanging vertically in the water, with just the head showing above the water. 'Bottling' the only view most people get to see.


    There are various diseases that are infecting marine wildlife. The main one that has had the most impact on seals is; 

    This virus mainly affects Common seals, although Grey seals have also been lost by it.The outbreak in 1988 resulted in the death of 18,000 Common seals and 300 Grey seals. It took 4 months for the virus to reach the UK from Denmark.
    The last outbreak was in 2002, and the population of Common seals in the wash declined by 51%. Grey seals were also exposed to the virus but no large scale mortality was reported.

    Grey seals show immunity to PDV (Carter et al. 1992; Hick, Duck & Thompson 1993)
    The virus contains no treat to humans, but dogs may be affected. Most dogs are vaccinated against it. Please check with your vet.

    Do not approach or touch dead or sick seals, they can carry other germs.
    Seals can bite! Bites can become infected and prove fatal.
    For information on what to do if you find a sick, injured or dead seal, please see our contact page.