Gray Seals, Halichoerus grypus
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Description & Behavior
Gray seals, Halichoerus grypus (Fabricius, 1791), aka 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 m in length and weighing 170-310 kg. Adult females measure 1.65-2.1 m in length and weigh between 103-180 kg. The western Atlantic gray seals tend to be about 20% heavier. Gray seals have been known to dive to depths up to 300 m 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 40s such as the 42 year old "Orkney", a male gray seal at the San Francisco Zoo, who recently passed [RIP].
World Range & Habitat
Gray seals, Halichoerus grypus, are found in the north Atlantic Ocean separated into two main distinct populations (subspecies Halichoerus grypus grypus): 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. A third distinct population of gray seals is located in the Baltic Sea as subspecies Halichoerus grypus macrorynchus.
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 gray 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.
Feeding Behavior (Ecology)
Gray 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, gray seals also consume seabirds occasionally. Gray seals typically dive to about 30-70 m while feeding. Sharks prey on gray seals in the western Atlantic, and orca (killer whales) have also been observed killing the gray seals on both sides of the Atlantic.
Gray seals, Halichoerus grypus, 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 kg each day. Newborn pups measure about 90-105 cm in length and weigh between 10-18 kg. 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. Pup remain at the rookery until molting, living off blubber reserves. Prior to molting, the coat of 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. Males 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 2-10 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 females 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.
Conservation Status & Comments
Large-scale commercial hunting of gray seals has not taken place in recent years. Nova Scotia, however, requested permission from the Canadian government to kill 25,000 gray seals per year for the next 3 years to market seal products. Additionally, in 1999, the Canadian Fisheries Resource Conservation Council requested an experimental commercial seal hunt of up to 20,000 gray seals on Sable Island.
Since 1999, the Canadian government permitted the killing of a few hundred gray seals per year in areas other than Sable Island, and is considering additional proposals for gray seal hunts. In 2000 the Norwegian government gave permission for 400 gray seals to be hunted on the coast of Western Norway, in spite of the unknown population numbers. The purpose of this hunt was to determine whether interest in seal hunting exists.
In spite of a lack of scientific evidence, the fishing industry claims that seal predation is responsible for reduced fish stocks in Canada, the United Kingdom, and Ireland, and has requested that gray seal populations be "culled." Requests to cull gray seal populations have also been made because these seals can apparently act as hosts to the codworm parasite, and a seal population reduction is thought by some to help reduce codworm infestation in cod and flatfish stocks.
Additional threats to gray seals on both sides of the Atlantic include shooting to prevent seal damage to fishing nets, traps, and catches. In the United Kingdom, fishermen are not required to report seal shootings under the "Fisheries Defence Clause" of the Conservation of Seals Act, so little is known about the scale of such killing in the U.K.
Official statistics show that more than 60 gray, Halichoerus grypus, and harbor seals, Phoca vitulina, were legally shot in 2000 under license by the Scottish fishery, the highest number in more than a decade. However the official figures may not include large numbers of both species, estimated by some organizations at several thousand seals shot under the Fisheries Defence Clause each year in Scotland. The government in Finland also allows the hunting of gray seals claiming that hunting protects fish stocks. Conservation groups are promoting the development and use of humane non-lethal seal deterrence methods such as anti-predator nets on fish farms. Conservation groups also argue that blaming reduced fish stocks on seal predation is merely a way to deflect attention from the fact that overfishing is the real problem.
Gray seals are also shot illegally as demonstrated by the shooting of 25 pups at a breeding rookery in the Scottish Orkney Islands in 1996. These seals are also at-risk of marine pollution such as organochlorines and oil spills, the latter which can cause acute respiratory distress. Oil contamination of gray seals is a severe problem in the Froan breeding area off central Norway. Between 30-60% of pups have become oil-fouled during their first month of life there.
Entanglement in marine debris is also a problem throughout the gray seal's range. In the Gulf of Maine, an estimated average of 75 gray seals were killed by entanglement each year between 1994 and 1998. In Canada, gray seals are found entangled in nets of groundfish and salmon gillnet fisheries. Spanish deep water trawl fisheries off Canada have also entangled gray seals. The number of seals entangled decreased following the Greenland salmon gillnet and Atlantic Canada cod trap fisheries ended in 1993. Entanglement of gray seals in the nets of monkfish fishermen in Cornwall, England. The number of gray seals entangled in the area's monkfish nets is estimated to be higher than the number of gray seals born there each year.
In 2000, rescue centers in Ireland and Wales reported rescuing record numbers of gray seal pups. The pups suffered a variety of conditions such as milky white eyes, mouth ulcers, swelling in the lower jaw and gums, crumbling jaws, brittle bones, and flu-like symptoms. In 2001 increased sightings of various seal species, including gray seals, were reported along the eastern seaboard of the United States, including seals needing rescue and rehabilitation. Cleaner habitats and/or reduced hunting may be the reason for the increase in populations. Increased commercial fishing in northern waters has also been cited as the reason because it causes seals to travel further south for food. Many of the seals in need of rescue were undernourished pups, and injured adults.
The gray seal is listed as a protected species under Annex II and Annex V of the European Community's (EC) Habitats Directive. Several gray seal habitats have been proposed by EC member countries as Special Areas of Conservation under the Habitats Directive. The gray seal is also listed as an Appendix III species under the Bern Convention. The Scottish Wildlife Trust purchased Linga Holm, a 56-hectare uninhabited island in the Scottish Orkney Islands, to establish the world's 3rd largest island-based gray seal breeding colony as a sanctuary for gray seals. The Trust monitors the seals' progress, protects them from threats, including requests for culls, and is working to increase legal protection for the island's gray seal population.
Hunting and severe pollution in the Baltic Sea has drastically reduced gray seal populations, although the population appears to be recovering.
In 1998, hunting of gray seals was banned in the Baltic Sea by the Helsinki Convention, however Finland and Sweden have recently called for the ban to be lifted in spite of scientific data published in 1997 that showed any amount of hunting Baltic gray seal populations would not be sustainable.
This species remains threatened by the level of pollution in the Baltic Sea by organochlorines often found in seal blubber that can cause reproductive failure. The pollution in the Baltic Sea has improved over the last 2 decades, however pollution-related illnesses, such as severe intestinal ulcers, still affect these seals.
Gray seals, Halichoerus grypus, are listed as Least Concern (LC) with the IUCN Red List of Threatened Species:
LEAST CONCERN (LC) - A taxon is Least Concern when it has been evaluated against the criteria and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. Widespread and abundant taxa are included in this category.
References & Further Research
Research Halichoerus grypus » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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