Grey seal

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Grey seal
Donna Nook NNR - Grey Seal pupping and breeding season - 38804871202.jpg
Male
Grey Seal Mother & Pup (158097807).jpg
Female with pup
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Family: Phocidae
Genus: Halichoerus
Nilsson, 1820
Species:
H. grypus
Binomial name
Halichoerus grypus
(O. Fabricius, 1791)
Grey Seal Halichoerus grypus distribution map.png
Grey seal range [1]

The grey seal (Halichoerus grypus) is a large seal of the family Phocidae, which are commonly referred to as "true seals" or "earless seals". The only species classified in the genus Halichoerus, it is found on both shores of the North Atlantic Ocean. In Latin, Halichoerus grypus means "hook-nosed sea pig". Its name is spelled gray seal in the US; it is also known as Atlantic seal [2] and the horsehead seal. [2] [3]

Contents

Taxonomy

There are two recognized subspecies of this seal: [4]

ImageSubspeciesDistribution
Two seals in the water.jpg Halichoerus grypus grypusFabricius, 1791Baltic Sea
Farne Grey seal.jpg Halichoerus grypus atlanticaNehring, 1886western North Atlantic stock (eastern Canada and the northeastern United States), the eastern North Atlantic stock (British Isles, Iceland, Norway, Denmark, the Faroe Islands, and Russia) [5]

The type specimen of H. g. grypus (Zoological Museum of Copenhagen specimen ZMUC M11-1525, caught in 1788 off the island of Amager, Danish part of the Baltic Sea) was believed lost for many years but was rediscovered in 2016, and a DNA test showed it belonged to a Baltic Sea specimen rather than from Greenland, as had previously been assumed (because it was first described in Otto Fabricius' book on the animals in Greenland: Fauna Groenlandica). The name H. g. grypus was therefore transferred to the Baltic subspecies (replacing H. g. macrorhynchus), and the name H. g. atlantica resurrected for the Atlantic subspecies. [6]

Molecular studies have indicated that the eastern and western Atlantic populations have been genetically distinct for at least one million years, and could potentially be considered separate subspecies. [7]

Description

A juvenile grey seal swims in the Farne Islands, UK. Juvenilegreysealswimmingfarneislands.jpg
A juvenile grey seal swims in the Farne Islands, UK.

This is a fairly large seal, with bulls in the eastern Atlantic populations reaching 1.95–2.3 m (6 ft 5 in – 7 ft 7 in) long and weighing 170–310 kg (370–680 lb); the cows are much smaller, typically 1.6–1.95 m (5 ft 3 in – 6 ft 5 in) long and 100–190 kg (220–420 lb) in weight. [8] Individuals from the western Atlantic are often much larger, with males averaging up to 2.7 m (8 ft 10 in) and reaching a weight of as much as 400 kg (880 lb) and females averaging up to 2.05 m (6 ft 9 in) and sometimes weighing up to 250 kg (550 lb). Record-sized bull grey seals can reach about 3.3 m (10 ft 10 in) in length. [9] [10] A common average weight in Great Britain was found to be about 233 kg (514 lb) for males and 154.6 kg (341 lb) for females whereas in Nova Scotia, Canada, adult males averaged 294.6 kg (649 lb) and adult females averaged 224.5 kg (495 lb). [8] [11] [12] It is distinguished from the smaller harbor seal by its straight head profile, nostrils set well apart, and fewer spots on its body. [13] [14] Wintering hooded seals can be confused with grey seals as they are about the same size and somewhat share a large-nosed look but the hooded has a paler base colour and usually evidences a stronger spotting. [15] Grey seals lack external ear flaps and characteristically have large snouts. [16] Bull greys have larger noses and a less curved profile than harbor seal bulls. Males are generally darker than females, with lighter patches and often scarring around the neck. Females are silver grey to brown with dark patches.

Ecology and distribution

Group of grey seals on sands at Stiffkey, Norfolk Grey seals, Stiffkey, Norfolk.jpg
Group of grey seals on sands at Stiffkey, Norfolk
A dead grey seal that drowned after being caught in a fishing net in Ystad Grasal (Halichoerus grypus) - Ystad -2018.jpg
A dead grey seal that drowned after being caught in a fishing net in Ystad
Grey seals on the Jokulsarlon glacial lake, Iceland Phoques communs sur le Jokulsarlon en Islande.jpg
Grey seals on the Jökulsárlón glacial lake, Iceland

In the United Kingdom and Ireland, the grey seal breeds in several colonies on and around the coasts. Notably large colonies are at Blakeney Point in Norfolk, Donna Nook in Lincolnshire, the Farne Islands off the Northumberland Coast (about 6,000 animals), Orkney and North Rona. [17] off the north coast of Scotland, Lambay Island off the coast of Dublin in the Irish Sea, the Isle of Man, Ramsey Island (off the coast of Pembrokeshire, Wales). In the German Bight, colonies exist off the islands Sylt, Amrum and on Heligoland. [18]

In the western North Atlantic, the grey seal is typically found in large numbers in the coastal waters of the Maritime Provinces of Canada and south to Nantucket in the United States. In coastal Canada, it is typically seen in areas such as the Gulf of St. Lawrence, Newfoundland, Prince Edward Island, and Quebec. The largest colony in the world is at Sable Island, Nova Scotia. In the United States, it is found year-round off the coast of New England, in particular Maine and Massachusetts. It has also been observed in the waters around Connecticut, New York and Rhode Island. Archaeological evidence confirms grey seals in southern New England with remains found on Block Island, Martha's Vineyard, and near the mouth of the Quinnipiac River in New Haven, Connecticut. [19] Its natural range now extends much further south than previously thought, with confirmed sightings off of North Carolina. Also, there is a report by Farley Mowat of historic breeding colonies as far south as Cape Hatteras, North Carolina. [3]

An isolated population exists in the Baltic Sea, [1] forming the H. grypus balticus subspecies.

Besides these very large colonies, many much smaller ones exist, some of which are well-known tourist attractions, despite their small size. Such colonies include one on the Carrack rocks, Cornwall.

During the winter months, grey seals can be seen hauled out on rocks, islands, and shoals not far from shore, occasionally coming ashore to rest. In the spring, recently-weaned pups and yearlings occasionally strand on beaches after becoming separated from their group.

Grey seals are vulnerable to typical predators for a pinniped mammal; their primary predator would be the orca or killer whale, but certain large species of sharks are known to prey on grey seals in North American waters, particularly great white sharks and bull sharks but also, upon evidence, additionally Greenland sharks. Some grey seal carcasses have washed ashore with visible “cookie cutter” bite marks, a telltale sign of attack by a Greenland shark (also called the sleeper shark). [20] [21] In the waters of Great Britain, grey seals are a fairly common prey species for killer whales. [22] [23] Apparently, grey seal pups are sometimes taken from beach colonies by white-tailed eagles, and golden eagles, as well. [1]

Diet

Grey seal food web in the Baltic Sea Grey seal food web.png
Grey seal food web in the Baltic Sea
A short video on monitoring and conservation of grey seals at Skomer Island
Captive grey seal being fed, showing snout shape Grey seal feeding Skansen.jpg
Captive grey seal being fed, showing snout shape

The grey seal feeds on a wide variety of fish, mostly benthic or demersal species, taken at depths down to 70 m (230 ft) or more. Sand eels (Ammodytes spp) are important in its diet in many localities. Cod and other gadids, flatfish, herring, [25] wrasse [26] and skates [27] are also important locally. However, it is clear that the grey seal will eat whatever is available, including octopus [28] and lobsters. [29] The average daily food requirement is estimated to be 5 kg (11 lb), though the seal does not feed every day and it fasts during the breeding season.

Recent observations and studies from Scotland, The Netherlands, and Germany show that grey seals will also prey and feed on large animals like harbour seals and harbour porpoises. [30] [31] [32] In 2014, a male grey seal in the North Sea was documented and filmed killing and cannibalising 11 pups of his own species over the course of a week. Similar wounds on the carcasses of pups found elsewhere in the region suggest that cannibalism and infanticide may not be uncommon in grey seals. Male grey seals may engage in such behaviour potentially as a way of increasing reproductive success through access to easy prey without leaving prime territory. [33]

Communication

While it was originally understood that marine mammals communicate vocally, new research conducted by researchers at Monash University shows that grey seals clap their flippers as another form of communication. They clap their flippers underwater to deter a predator from attacking. If done during the mating season, the clapping can be used as a way to find a potential mate. The Monash researchers point out that seals are typically known for clapping, so this behavior may not be a surprise, but the clapping we know typically occurs in captivity. Clapping seals are associated with aquariums and zoos, but were never observed in the wild for this behavior. They were astonished at how loud these marine mammals were able to clap underwater, but it is logical for the reasons they do this. [34]

Reproduction

Cow (l) and bull (r) grey seals mating, Donna Nook, Lincolnshire, U.K. GreySealMating.jpg
Cow (l) and bull (r) grey seals mating, Donna Nook, Lincolnshire, U.K.

Grey seals are capital breeders; they forage to build up stored blubber, which is utilised when they are breeding and weaning their pups, as they do not forage for food at this time. They give birth to a single pup every year, with females' reproductive years beginning as early as 4 years old and extending up to 30 years of age. All parental care is provided by the female. During breeding, males do not provide parental care but they defend females against other males for mating. [35] The pups are born at around the mass of 14 kg. [36] They are born in autumn (September to December) in the eastern Atlantic and in winter (January to February) in the west, with a dense, soft silky white fur; at first small, they rapidly fatten up on their mothers' extremely fat-rich milk. The milk can consist of up to 60% fat. [36] Grey seal pups are precocial, with mothers returning to the sea to forage once pups are weaned. Pups also undergo a post-weaning fast before leaving the land and learning to swim. [37] Within a month or so they shed the pup fur, grow dense waterproof adult fur, and leave for the sea to learn to fish for themselves. In recent years, the number of grey seals has been on the rise in the west and the U.S. [38] and Canada [39] there have been calls for a seal cull.

Seal pup a few days after birth Juvenile Grey Seal.jpg
Seal pup a few days after birth

Seal pup first-year survival rates are estimated to vary from 80–85% [40] [41] to below 50% [42] depending on location and conditions. Starvation, due to difficulties in learning to feed, appears to be the main cause of pup death. [42]

Status

After near extirpation from hunting grey seals for oil, meat, and skins in the United States, sightings began to increase in the late 1980s. Bounties were paid on all kinds of seals up until 1945 in Maine and 1962 in Massachusetts. [43] One year after Congress passed the 1972 Marine Mammal Protection Act preventing the harming or harassing of seals, a survey of the entire Maine coast found only 30 grey seals. [43] At first grey seal populations increased slowly but then rebounded from islands off Maine to Monomoy Island and Nantucket Island off of southern Cape Cod. The southernmost breeding colony was established on Muskeget Island with five pups born in 1988 and over 2,000 counted in 2008. [44] According to a genetics study, the United States population has formed as a result of recolonisation by Canadian seals. [44] By 2009, thousands of grey seals had taken up residence on or near popular swimming beaches on outer Cape Cod, resulting in sightings of great white sharks drawn close to shore to hunt the seals. [45] A count of 15,756 grey seals in southeastern Massachusetts coastal waters was made in 2011 by the National Marine Fisheries Service. [46] Grey seals are being seen increasingly in New York and New Jersey waters, and it is expected that they will establish colonies further south.

Human noise pollution continues to affect marine-life communication but remains an understudied facet of marine conservation efforts. In more recent years, the potential negative effect of human noise has been highlighted with the discovery of seals using clapping as a form of communication. [34]

In the UK seals are protected under the Conservation of Seals Act 1970; however, it does not apply to Northern Ireland. In the UK there have also been calls for a cull from some fishermen claiming that stocks have declined due to the seals.

The population in the Baltic Sea has increased about 8% per year between 1990 and the mid-2000s, with the numbers becoming stagnant since 2005. As of 2011 hunting grey seals is legal in Sweden and Finland, with 50% of the quota being used. Other anthropogenic causes of death include drowning in fishing gear. [47]

Captivity

Grey seals have proved amenable to life in captivity[ citation needed ] and are commonly found in zoo animals around their native range, particularly in Europe. Traditionally they were popular circus animals and often used in performances such as balancing and display acts.

Related Research Articles

<span class="mw-page-title-main">Pinniped</span> Taxonomic group of semi-aquatic mammals

Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae, with 34 extant species and more than 50 extinct species described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage. Pinnipeds belong to the suborder Caniformia of the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.

<span class="mw-page-title-main">Steller sea lion</span> Species of carnivore

The Steller sea lion is a large, near-threatened species of sea lion, predominantly found in the coastal marine habitats of the northeast Pacific Ocean and the Pacific Northwest regions of North America, from north-central California to Oregon, Washington and British Columbia to Alaska. Its range continues across the Northern Pacific and the Aleutian Islands, all the way to Kamchatka, Magadan Oblast, and the Sea of Okhotsk, south to Honshu's northern coastline. It is the sole member of the genus Eumetopias, and the largest of the so-called eared seals (Otariidae). Among pinnipeds, only the walrus and the two species of elephant seal are bigger. The species is named for the naturalist and explorer Georg Wilhelm Steller, who first described them in 1741. Steller sea lions have attracted considerable attention in recent decades, both from scientists and the general public, due to significant declines in their numbers over an extensive portion of their northern range, notably in Alaska.

<span class="mw-page-title-main">Ringed seal</span> Species of carnivore

The ringed seal is an earless seal inhabiting the Arctic and sub-Arctic regions. The ringed seal is a relatively small seal, rarely greater than 1.5 m in length, with a distinctive patterning of dark spots surrounded by light gray rings, hence its common name. It is the most abundant and wide-ranging ice seal in the Northern Hemisphere, ranging throughout the Arctic Ocean, into the Bering Sea and Okhotsk Sea as far south as the northern coast of Japan in the Pacific and throughout the North Atlantic coasts of Greenland and Scandinavia as far south as Newfoundland, and including two freshwater subspecies in northern Europe. Ringed seals are one of the primary prey of polar bears and killer whales, and have long been a component of the diet of indigenous people of the Arctic.

<span class="mw-page-title-main">Bearded seal</span> Species of Arctic dwelling marine mammal

The bearded seal, also called the square flipper seal, is a medium-sized pinniped that is found in and near to the Arctic Ocean. It gets its generic name from two Greek words that refer to its heavy jaw. The other part of its Linnaean name means bearded and refers to its most characteristic feature, the conspicuous and very abundant whiskers. When dry, these whiskers curl very elegantly, giving the bearded seal a "raffish" look.

<span class="mw-page-title-main">Harbour porpoise</span> Species of mammal

The harbour porpoise is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar porpoise to whale watchers. This porpoise often ventures up rivers, and has been seen hundreds of kilometres from the sea. The harbour porpoise may be polytypic, with geographically distinct populations representing distinct races: P. p. phocoena in the North Atlantic and West Africa, P. p. relicta in the Black Sea and Sea of Azov, an unnamed population in the northwestern Pacific and P. p. vomerina in the northeastern Pacific.

<span class="mw-page-title-main">Leopard seal</span> Macropredatory species of Antarctic seal

The leopard seal, also referred to as the sea leopard, is the second largest species of seal in the Antarctic. Its only natural predator is the orca. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, fish, and birds, particularly penguins. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of Lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "thin-clawed".

<span class="mw-page-title-main">Northern elephant seal</span> Species of marine mammal

The northern elephant seal is one of two species of elephant seal. It is a member of the family Phocidae. Elephant seals derive their name from their great size and from the male's large proboscis, which is used in making extraordinarily loud roaring noises, especially during the mating competition. Sexual dimorphism in size is great. Correspondingly, the mating system is highly polygynous; a successful male is able to impregnate up to 50 females in one season.

<span class="mw-page-title-main">Hooded seal</span> Species of carnivore

The hooded seal is a large phocid found only in the central and western North Atlantic, ranging from Svalbard in the east to the Gulf of St. Lawrence in the west. The seals are typically silver-grey or white in color, with black spots that vary in size covering most of the body. Hooded seal pups are known as "blue-backs" because their coats are blue-grey on the back with whitish bellies. This coat is shed after 14 months of age when the pups molt. It is the only species in the genus Cystophora.

<span class="mw-page-title-main">Harp seal</span> Species of mammal

The harp seal, also known as Saddleback Seal or Greenland Seal, is a species of earless seal, or true seal, native to the northernmost Atlantic Ocean and Arctic Ocean. Originally in the genus Phoca with a number of other species, it was reclassified into the monotypic genus Pagophilus in 1844. In Greek, its scientific name translates to "ice-lover from Greenland," and its taxonomic synonym, Phoca groenlandica translates to "Greenlandic seal." This is the only species in the genus Pagophilus.

<span class="mw-page-title-main">Hawaiian monk seal</span> Species of carnivore

The Hawaiian monk seal is an endangered species of earless seal in the family Phocidae that is endemic to the Hawaiian Islands.

<span class="mw-page-title-main">Monk seal</span> Tribe of earless seals

Monk seals are earless seals of the tribe Monachini. They are the only earless seals found in tropical climates. The two genera of monk seals, Monachus and Neomonachus, comprise three species: the Mediterranean monk seal, Monachus monachus; the Hawaiian monk seal, Neomonachus schauinslandi; and the Caribbean monk seal, Neomonachus tropicalis, which became extinct in the 20th century. The two surviving species are now rare and in imminent danger of extinction. All three monk seal species were classified in genus Monachus until 2014, when the Caribbean and Hawaiian species were placed into a new genus, Neomonachus.

<span class="mw-page-title-main">Antarctic fur seal</span> Species of carnivore

The Antarctic fur seal is one of eight seals in the genus Arctocephalus, and one of nine fur seals in the subfamily Arctocephalinae. Despite what its name suggests, the Antarctic fur seal is mostly distributed in Subantarctic islands and its scientific name is thought to have come from the German vessel SMS Gazelle, which was the first to collect specimens of this species from Kerguelen Islands.

<span class="mw-page-title-main">Subantarctic fur seal</span> Species of carnivore

The subantarctic fur seal is a species of arctocephaline found in the southern parts of the Indian, Pacific, and Atlantic Oceans. It was first described by Gray in 1872 from a specimen recovered in northern Australia—hence the inappropriate specific name tropicalis.

<span class="mw-page-title-main">Galápagos fur seal</span> Species of carnivore

The Galápagos fur seal is one of eight seals in the genus Arctocephalus. It is the smallest of all eared seals. It is endemic to the Galápagos Islands in the eastern Pacific. The total estimated population as of 1970 was said to be about 30,000, although the population has been said to be on the decline since the 1980s due to environmental factors such as pollution, disease, invasive species, and their limited territory. Due to the population having been historically vulnerable to hunting, the Galápagos fur seal has been protected by the Ecuadorian government since 1934

<span class="mw-page-title-main">Brown fur seal</span> Species of carnivore

The brown fur seal, also known as the Cape fur seal, South African fur seal and Australian fur seal, is a species of fur seal.

<span class="mw-page-title-main">South American sea lion</span> Species of carnivore

The South American sea lion, also called the southern sea lion and the Patagonian sea lion, is a sea lion found on the western and southeastern coasts of South America. It is the only member of the genus Otaria. The species is highly sexually dimorphic. Males have a large head and prominent mane. They mainly feed on fish and cephalopods and haul out on sand, gravel, rocky, or pebble beaches. In most populations, breeding males are both territorial and harem holding; they establish territories first and then try to herd females into them. The overall population of the species is considered stable, estimated at 265,000 animals.

<i>Arctocephalus forsteri</i> Species of carnivore

Arctocephalus forsteri is a species of fur seal found mainly around southern Australia and New Zealand. The name New Zealand fur seal is used by English speakers in New Zealand; kekeno is used in the Māori language. As of 2014, the common name long-nosed fur seal has been proposed for the population of seals inhabiting Australia.

<span class="mw-page-title-main">Weddell seal</span> Species of mammal

The Weddell seal is a relatively large and abundant true seal with a circumpolar distribution surrounding Antarctica. The Weddell seal was discovered and named in the 1820s during expeditions led by British sealing captain James Weddell to the area of the Southern Ocean now known as the Weddell Sea. The life history of this species is well documented since it occupies fast ice environments close to the Antarctic continent and often adjacent to Antarctic bases. It is the only species in the genus Leptonychotes.

<span class="mw-page-title-main">Southern elephant seal</span> Species of marine mammal

The southern elephant seal is one of two species of elephant seals. It is the largest member of the clade Pinnipedia and the order Carnivora, as well as the largest extant marine mammal that is not a cetacean. It gets its name from its massive size and the large proboscis of the adult male, which is used to produce very loud roars, especially during the breeding season. A bull southern elephant seal is about 40% heavier than a male northern elephant seal, which is nearly twice the weight of a male walrus, or 6–7 times heavier than the largest living mostly terrestrial carnivorans, the Kodiak bear and the polar bear.

<span class="mw-page-title-main">Harbor seal</span> Species of mammal

The harborseal, also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped, they are found in coastal waters of the northern Atlantic and Pacific oceans, Baltic and North seas.

References

  1. 1 2 3 4 Bowen, D. (2016). "Halichoerus grypus". IUCN Red List of Threatened Species . 2016: e.T9660A45226042. doi: 10.2305/IUCN.UK.2016-1.RLTS.T9660A45226042.en . Retrieved 19 November 2021.
  2. 1 2 Sokolov, Vladimir (1984). Пятиязычный словарь названий животных. Млекопитающие. Moscow.{{cite book}}: CS1 maint: location missing publisher (link)
  3. 1 2 Mowat, Farley (1984). Sea of Slaughter (First American ed.). Atlantic Monthly Press Publishing. ISBN   0871130130.
  4. ↑ Wozencraft, W. C. (2005). "Order Carnivora". In Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. ISBN   978-0-8018-8221-0. OCLC   62265494.
  5. ↑ "Gray Seal". NOAA. 8 July 2019. Retrieved 5 January 2021.
  6. ↑ Olsen, Morten Tange; Galatius, Anders; Biard, Vincent; Gregersen, Kristian; Kinze, Carl Christian (April 2016). "The forgotten type specimen of the grey seal [Halichoerus grypus (Fabricius, 1791)] from the island of Amager, Denmark". Zoological Journal of the Linnean Society. 178 (3): 713–720. doi: 10.1111/zoj.12426 .
  7. ↑ Boskovic, R.; et al. (1996). "Geographic distribution of mitochondrial DNA haplotypes in grey seals (Halichoerus grypus)". Canadian Journal of Zoology. 74 (10): 1787–1796. doi:10.1139/z96-199.
  8. 1 2 Working Party on Marine Mammals (1978). Mammals in the Seas, Volume 4. Rome: Food & Agriculture Org. p. 257. ISBN   9251005141.
  9. ↑ Naughton, D. (2014). The Natural History of Canadian Mammals: Opossums and Carnivores. University of Toronto Press.
  10. ↑ Bjärvall, A.; Ullström, S. (1986). The mammals of Britain and Europe. London: Croom Helm. ISBN   0709932685.
  11. ↑ Lidgard, D. C.; Boness, D. J.; Bowen, W. D. (2001). "A novel mobile approach to investigating mating tactics in male grey seals (Halichoerus grypus)". Journal of Zoology. 255 (3): 313–320. doi:10.1017/S0952836901001418. hdl:10088/343.
  12. ↑ Baker, S. R.; Barrette, C.; Hammill, M. O. (1995). "Mass transfer during lactation of an ice-breeding pinniped, the grey seal (Halichoerus grypus), in Nova Scotia, Canada". Journal of Zoology. 236 (4): 531–542. doi:10.1111/j.1469-7998.1995.tb02730.x.
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  15. ↑ Hall, Ailsa; Thompson, David (2009). "Grey Seal (Halichoerus gryphus)". In Perrin, W. F.; Würsig, B.; Thewissen, J. G. M. (eds.). Encyclopedia of marine mammals. Academic Press. pp. 500–502. ISBN   9780080919935.
  16. ↑ Schuster, Marreno; Glen, Megan (2011). Marine Science: The Dynamic Ocean. US Satellite Laboratory: Pearson. p. 107. ISBN   978-0-13-317063-4.
  17. ↑ Stewart, J.E.; et al. (2014). "Finescale ecological niche modeling provides evidence that lactating grey seals (Halichoerus grypus) prefer access to fresh water in order to drink" (PDF). Marine Mammal Science. 30 (4): 1456–1472. Bibcode:2014MMamS..30.1456S. doi:10.1111/mms.12126.
  18. ↑ Hahn, Melanie (13 January 2010). "Kegelrobben-Geburtenrekord auf Helgoland". Nordseewolf Magazin (in German). Archived from the original on 31 March 2016. Retrieved 20 November 2011.
  19. ↑ Waters, Joseph H. (February 1967). "Gray Seal Remains from Southern New England Archeological Sites". Journal of Mammalogy. 48 (1): 139–141. doi:10.2307/1378182. JSTOR   137818.
  20. ↑ Brodie, Paul; Beck, Brian (1983). "Predation by Sharks on the Grey Seal (Halichoerus grypus) in Eastern Canada". Canadian Journal of Fisheries and Aquatic Sciences. 40 (3): 267–271. doi:10.1139/f83-040.
  21. ↑ Lucas, Z. N.; Natanson, L. J. (2010). "Two shark species involved in predation on seals at Sable Island, Nova Scotia, Canada". Proceedings of the Nova Scotian Institute of Science. 45 (2): 64–88. doi:10.15273/pnsis.v45i2.3987 (inactive 31 January 2024).{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link)
  22. ↑ Weir, C. R. (2002). "Killer whales (Orcinus orca) in UK waters". British Wildlife. 14 (2): 106–108.
  23. ↑ Bloc, D.; Lockyer, C. (1988). "Killer whales (Orcinus area) in Faroese waters". Rit Fiskideildar.
  24. ↑ Karlson, A.M.; Gorokhova, E.; Gårdmark, A.; Pekcan-Hekim, Z.; Casini, M.; Albertsson, J.; Sundelin, B.; Karlsson, O.; Bergström, L. (2020). "Linking consumer physiological status to food-web structure and prey food value in the Baltic Sea". Ambio. 49 (2): 391–406. Bibcode:2020Ambio..49..391K. doi:10.1007/s13280-019-01201-1. PMC   6965491 . PMID   31168701.
  25. ↑ Stenman, Olavi (2007). "How does hunting grey seals (Halichoerus grypus) on Bothnian Bay spring ice influence the structure of seal and fish stocks?" (PDF). International Council for the Exploration of the Sea . Retrieved 23 January 2017. Analysis of fish otolithes and other hard particles in the alimentary tract showed clearly that the herring (Clupea harengus) was the most important item of prey.
  26. ↑ Ridoux, Vincent; Spitz, J.; Vincent, Cecile; Walton, M. J. (2007). "Grey seal diet at the southern limit of its European distribution: combining dietary analyses and fatty acid profiles" (PDF). Journal of the Marine Biological Association of the United Kingdom. 87 (1): 255–264. Bibcode:2007JMBUK..87..255R. doi:10.1017/S002531540705463X. S2CID   55465507 . Retrieved 24 January 2017.
  27. ↑ Savenkoff, Claude; Morissette, Lyne; Castonguay, Martin; Swain, Douglas P.; Hammill, Mike O.; Chabot, Denis; Hanson, J. Mark (2008). "Interactions between Marine Mammals and Fisheries: Implications for Cod Recovery". In Chen, Junying; Guo, Chuguang (eds.). Ecosystem Ecology Research Trends. Nova Science Publishers. p. 130. ISBN   978-1-60456-183-8.
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  31. ↑ van Neer, Abbo; Jensen, Lasse F.; Siebert, Ursula (2015). "Grey seal (Halichoerus grypus) predation on harbour seals (Phoca vitulina) on the island of Helgoland, Germany". Journal of Sea Research . 97: 1–4. Bibcode:2015JSR....97....1V. doi:10.1016/j.seares.2014.11.006.
  32. ↑ Hillmer, Angelika (16 February 2015). "Kegelrobben mit großem Appetit auf Schweinswale" [Grey seals with a great appetite for porpoises]. Hamburger Abendblatt (in German).
  33. ↑ Gabbatiss, Josh (15 February 2016). "First video footage of seal drowning and eating a pup". New Scientist.
  34. 1 2 "Grey seals discovered clapping underwater to communicate". ScienceDaily. Retrieved 19 March 2021.
  35. ↑ Bubac, Christine M.; Coltman, David W.; Don Bowen, W.; Lidgard, Damian C.; Lang, Shelley L. C.; den Heyer, Cornelia E. (June 2018). "Repeatability and reproductive consequences of boldness in female gray seals". Behavioral Ecology and Sociobiology. 72 (6). doi:10.1007/s00265-018-2515-5. ISSN   0340-5443. S2CID   46975859.
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  39. ↑ "Plan to cull 70,000 grey seals gets Senate panel's approval". CBC News. Newfoundland & Labrador. 23 October 2012.
  40. ↑ Ailsa j, Hall; Bernie j, Mcconnell; Richard j, Barker (2008). "Factors affecting first-year survival in grey seals and their implications for life history strategy". Journal of Animal Ecology. 70: 138–149. doi: 10.1111/j.1365-2656.2001.00468.x .
  41. ↑ Baker, J. R. (1984). "Mortality and morbidity in Grey seal pups (Halichoerus grypus). Studies on its causes, effects on the environment, the nature and sources of infectious agents, and the immunological status of pups". Journal of Zoology. 203: 23–48. doi:10.1111/j.1469-7998.1984.tb06042.x.
  42. 1 2 "Homepage". Friends of Horsey Seals. Retrieved 19 March 2021.
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  44. 1 2 Wood, S.A.; Frasier, T.R.; McLeod, B.A.; Gilbert, J.R.; White, B.N.; Bowen, W.D.; Hammill, M.O.; Waring, G.T.; Brault, S. (2011). "The genetics of recolonization: an analysis of the stock structure of grey seals (Halichoerus grypus) in the northwest Atlantic". Canadian Journal of Zoology. 89 (6): 490–497. doi:10.1139/z11-012.
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  46. ↑ Gray Seal (Halichoerus grypus grypus): Western North Atlantic Stock (PDF) (Report). NMFS, NOAA. April 2014. pp. 342–350. Retrieved 15 June 2015.
  47. ↑ Bäcklin, Britt-Marie; Moraeus, Charlotta; Kunnasranta, Mervi; Isomursu, Marja (2 September 2011). "Health Assessment in the Baltic grey seal (Halichoerus grypus)". HELCOM Indicator Fact Sheets 2011. HELCOM. Archived from the original on 3 November 2011.
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