Atlantic Grey Seals

Halicorus grypus, hook nosed sea pig

Ramsey boasts the largest breeding colony of Atlantic grey seals in southern Britain. Throughout most of the year it is home to a small population of approximately 100, often juvenile, seals. Twice annually these numbers will increase significantly, as the adults come to the area to moult from December to February/March, and to breed in late August to November. During the breeding season in particular, numbers can increase to in excess of a thousand seals around Ramsey alone.

As the British Isles are home to almost 50% of the world’s population of these seals, a colony of this size is of both national and international conservation importance. Surveys carried out on the island by the RSPB over the last few years have regularly recorded counts of between 500-700 pups born each autumn.

The average lifespan of an Atlantic grey seal is between 25 and 35 years old, though the oldest recorded female was 46, and an adult bull seal can reach 310kg/40 stone and 2m in length, females being somewhat smaller. The females will outlive the bulls by anything up to ten years, and this is generally attributed to the fact that, during the breeding season, each cove will have a dominant bull for the duration of the season. He will have to patrol his territory and fight to defend it from potential rivals if necessary.

During the breeding season the seals give birth to their pups on the beaches around the island. These pups are typically 90-105cm in length and weigh 10-18kg. The female will feed her pup for a sum total of three weeks before weaning and abandoning the youngster. In this short amount of time the pup will triple its birth weight, gaining an average of 2kg per day, fed on one of the richest mammal milks known to man at about 60% fat. Meanwhile, the female rapidly loses condition, dropping 4 kg per day and shedding as much as a third of her body weight. The pups are born with a white, fluffy, non-waterproof coat, which they will moult out in their third week when they are weaned.

Once weaned, pups are abandoned by the mother, who heads back out to sea to start feeding again. She mates with the dominant bull in the cove before she goes; however, she has lost so much weight feeding the pup that she is in no condition to become pregnant. To overcome this, seals have a clever system of delayed implantation whereby the fertilised egg will not implant in the womb for about 3 months allowing the female to head back out to sea and build up her reserves.

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