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Gregory R. Mann, Ph.D. {ret.}

Grey Seal

“Halichoerus grypus”

Grey Seals have a wide variety of coloring. Males tend to have a dark brown-gray to black coat with a few light patches. Females are generally light gray-tan, lighter on the chest with dark spots and patches. Adult males and some older adult females to a lesser extent, have a characteristically long nose with wide nostrils, which is why this species is called “Horsehead” in Canada and why its Latin name translates to “Hooked-nose Pig of the Sea”. Adult males in the eastern Atlantic population are smaller than those of the western Atlantic measuring between 1.95-2.5 meters in length and weighing 170-310 kilograms. Adult females measure 1.65-2.1 meters in length and weigh between 103-180 kilograms. The western Atlantic Grey Seals tend to be about 20% heavier. Grey Seals have been known to dive to depths up to 300 meters for as long as 20 minutes. Females live up to 35 years of age, males up to 25 years. Members of the western Atlantic population generally live longer. Their maximum recorded ages are 46 years for females and 29 years for males, although in captivity, males actually live longer into their 40’s such as the 42-year-old “Orkney”, a male Grey Seal at the San Francisco Zoo who died in 2013. Grey Seals are found in the north Atlantic Ocean separated into three distinct populations: the western Atlantic population is found off the coast of Canada from north Labrador down to New England occasionally as far south as Virginia. The eastern Atlantic population is found around the coasts of the United Kingdom and Ireland and on the coasts of the Faroe Islands, Iceland, Norway and northwestern Russia as far as the White Sea. Smaller populations are also found on the French, Dutch and German coasts and wandering individuals have been found as far south as Portugal. The third known population of Grey Seals is located in the Baltic Sea.

The total western Atlantic population is thought to be at least 150,000, mostly found on the coasts of Sable Island and the Gulf of St. Lawrence. Approximately 130,000-140,000 Grey Seals are estimated in the eastern Atlantic population, and about 7,500 in the Baltic Sea population making the total estimated world-wide total around 290,000-300,000. Grey Seals feed on a wide variety of fish, crustaceans and cephalopods. Sand Eels or Sand Lances are the preferred prey in many areas. Like other seal species, Grey Seals also consume seabirds occasionally. They typically dive to about 30-70 meters while feeding. Sharks prey on Grey Seals in the western Atlantic and Killer Whales have also been observed killing the these seals on both sides of the Atlantic. Grey Seals gather together for hauling out, breeding and molting. The breeding season varies between populations, generally taking place between mid-December and early February in Canada, late July to December in the U.K., February to April in the Baltic Sea and peaking in October in Iceland and Norway. Breeding territories also vary by population in the Atlantic and are established on rocky islands and coasts, in caves, sandy islands and beaches and in some areas of the Gulf of St. Lawrence on land-fast ice or ice floes. In middle of the Baltic Sea, pups are born on pack ice and some seals also pup on land near Estonia and the Stockholm archipelago. Pupping on pack ice varies according to the amount of ice formed in the Baltic Sea.

Females reach sexual maturity at 3-5 years, males at 4-6 years, although males may not attain territorial status until 8-10 years of age. Females usually give birth at the rookery about a day after coming ashore at the rookery, nursing for about 17-18 days during which time pups gain between 1.2-2 kilograms each day. Newborn pups measure about 90-105 cm in length and weigh between 10-18 kilograms. Pups are generally at the upper end of this range in the western Atlantic. Towards the end of the nursing period, the mother mates with one or more males. During this time her pup is weaned and left to fend for itself. Pups remain at the rookery until molting, living off blubber reserves. Prior to molting, the coat of Grey Seal pups is creamy-white in color and woolly in texture. A shorter coat is revealed when this coat is molted 2-4 weeks after pups are born. After molting, pups begin feeding at sea, usually about 1-4 weeks after weaning. Pups disperse in many different directions from the rookery and are frequently found over 1,000 km away. The mortality rate for pups in their first year can be as high as 30-55%; larger mortality rates tend to occur during the nursing period where rookeries are crowded or located on wave-swept beaches. Mating takes place on land on ice or in the water. Male Grey Seals enter the rookeries when the females start to pup trying to gain sole access to a group of about 2-10 females. Successful males will mate with 2-20 females however in areas such as sand or ice where the females are more spread out, males will often mate with only 1 female. Recent evidence revealed that females often have a greater degree of choice in partners than the males. Lactating female Grey Seals do not feed during the breeding season for about 3 weeks and dominant males do not feed for up to 6 weeks. After mating, the males and females return to pelagic waters to feed.

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