Grey Seal

The UK supports approximately 33% of the world population of grey seals (Halichoerus grypus), which represents 95% of the total EU population. Grey seals are a designated interest features of the Berwickshire and North Northumberland Coast SAC. The Farne Islands support a population of approximately 4000 individuals, with around 1000 pups produced each year, providing 3% of the annual pup production for the UK. Females give birth to a single, white coated pup from September to December, often selecting sites close to where they gave birth in the previous season. They suckle the pup for 17 to 23 days. Pups moult their white natal coat (also called “lanugo”) around the time of weaning and then remain on the breeding colony for up to two weeks before going to sea. Adult females mate at the end of lactation and then depart to sea and provide no further parental care. In general, female grey seals return to the same colony to breed in successive years and often breed at the colony in which they were born. Access to undisturbed pupping areas is a key requirement of the seals and the success of the Farne Islands colony is thought to be largely due to their isolated nature. Seals also use relatively inaccessible rocky beaches to the north of Fast Castle Head, on Coquet Island, south of Alnmouth and the sand flats of Lindisfarne for breeding and hauling out, while the whole SACis used as a passageway between colonies.

Grey seals are long-lived animals. Males may live for over 20 years and begin to breed from about age 10. Females often live for over 30 years and begin to breed at about age 5. They are the largest carnivores in our coastal waters. Adult males can weigh over 300kg while the females weigh around 150-200kg.

They are generalists, feeding mainly on the sea bed at depths up to 100m although they are probably capable of feeding at all the depths found across the UK continental shelf. Their diet varies both seasonally and geographically but comprises mainly small demersal fish species that live on or close to the seabed. The diet of the Farne Island seals is composed primarily of sandeels, whitefish (cod, haddock, whiting, ling), and flatfish (plaice, sole, flounder, dab). Food requirements depend on the size of the seal and fat content (oiliness) of the prey, but an average consumption estimate is 7 kg of cod or 4 kg of sandeels per seal per day.

Grey seals forage in the open sea and return regularly to haul out on land where they rest, moult and breed. They may range widely to forage and frequently travel over 100km between haulout sites. Foraging trips can last anywhere between 1 and 30 days. Compared with other times of the year, grey seals in the UK spend longer hauled out during their annual moult (between December and April) and during their breeding season (between August and December). Tracking of individual seals has shown that they can feed up to several hundred kilometres offshore although most foraging probably occurs within 100km of a haulout site. Individual grey seals based at a specific haulout site often make repeated trips to the same region offshore, but will occasionally move to a new haulout site, often several hundred kilometres away and begin foraging in a new region.