Grey seal

Grey seal
Conservation status

Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Superfamily: Pinnipedia
Family: Phocidae
Genus: Halichoerus
Nilsson, 1820
Species: H. grypus
Binomial name
Halichoerus grypus
(Fabricius, 1791)
Approximate range of the grey seal (in blue)

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

Appearance

It is a large seal, with bulls reaching 2.5–3.3 m (8.2–10.8 ft) long and weighing 170–310 kg (370–680 lb); the cows are much smaller, typically 1.6–2.0 m (5.2–6.6 ft) long and 100–190 kg (220–420 lb) in weight. Individuals from the western Atlantic are often much larger, males reaching 400 kg (880 lb) and females weighing up to 250 kg (550 lb).[4] It is distinguished from the harbor seal by its straight head profile, nostrils set well apart, and fewer spots on its body. Bull Greys have larger noses and a less curved profile than common 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

In the United Kingdom and Ireland, the grey seal breeds in several colonies on and around the coasts. Notably large colonies are at Donna Nook (Lincolnshire), the Farne Islands off the Northumberland Coast (about 6,000 animals), Orkney and North Rona.[5] off the north coast of Scotland, Lambay Island off the coast of Dublin and Ramsey Island off the coast of Pembrokeshire. In the German Bight, colonies exist off the islands Sylt and Amrum and on Heligoland.[6]

In the Western North Atlantic, the grey seal is typically found in large numbers in the coastal waters of Canada and south to about New Jersey in the United States. In Canada, it is typically seen in areas such as the Gulf of St. Lawrence, Newfoundland, the Maritimes, and Quebec. The largest colony in the world is at Sable Island, NS. In the United States it's found year round off the coast of New England, in particular Maine and Massachusetts, and slightly less frequently in the Middle Atlantic States. Its natural range extends south to Virginia.

In recent years, the number of grey seals has been on the rise in the west and in Canada there have been calls for a seal cull.

An isolated population exists in the Baltic Sea,[1] forming the H. grypus balticus subspecies. One case of occurrence was registered in the Black Sea near the coasts of Ukraine[7]

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.

Diet

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[8] and skates[9] are also important locally. However, it is clear that the grey seal will eat whatever is available, including octopus[10] and lobsters.[11] 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.[12][13][14]

Reproduction

Cow and bull gray seals mating, Donna Nook, Lincolnshire, U.K. Nov 2007
A few days old pup.

The pups are born at around the mass of 14 kg.[15] They are born in autumn (September to November) 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.[15] 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 in the U.S.[16] and Canada[17] there have been calls for a seal cull.

Status

In the United States grey seal numbers are increasing rapidly. Up until 1962, Maine and Massachusetts had bounties on seals so that only a few isolated colonies of grey seals remained in Maine. Then in 1972 Congress passed the Marine Mammal Protection Act that prevented harming or harassing seals, and grey seal populations rebounded. For example there is a large breeding colony near Cape Cod, Massachusetts, where pups rebounded from a handful in 1980 to more than 2,000 in 2008. By 2009, thousands of grey seals there had taken up residence on or near popular swimming beaches when great white sharks started hunting them close to shore.[18] Also grey seals are seen increasingly in New York and New Jersey waters, and it's expected that they will establish colonies further south.

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 the drowning in fishing gear.[19]

Subspecies

There are two recognized subspecies of this seal:[20]

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 as separate subspecies.[21]

References

  1. ↑ 1.0 1.1 Thomspon, D. & Harkonen, T. (2008). Halichoerus grypus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 29 January 2009.
  2. ↑ 2.0 2.1 Соколов, Владимир (1984). Пятиязычный словарь названий животных. Млекопитающие. Москва.
  3. ↑ Mowat, Farley, Sea Of Slaughter, Atlantic Monthly Press Publishing, First American Edition, 1984.
  4. ↑ Gray Seal (marine mammals) . what-when-how.com
  5. ↑ Stewart, J.E. et al. (2014). "Finescale ecological niche modeling provides evidence that lactating gray seals (Halichoerus grypus) prefer access to fresh water in order to drink". Marine Mammal Science 30 (4): 1456–1472. doi:10.1111/mms.12126.
  6. ↑ Hahn, Melanie (13 January 2010). "Kegelrobben-Geburtenrekord auf Helgoland". Nordseewolf Magazin (in German). Retrieved 20 November 2011.
  7. ↑ Kovtun O.O. (2011) Rare sightings and video-recording of the grey seal, Halichoerus grypus (Fabricius, 1791), in coastal grottoes of the eastern Crimea (Black Sea). Marine Ecological Journal, 10(4):22. (in Russian)
  8. ↑ Stenman, Olavi (2007). "How does hunting grey seals (Halichoerus grypus) on Bothnian Bay spring ice influence the structure of seal and fish stocks?". International Council for the Exploration of the Sea. Retrieved 20 November 2011. 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.
  9. ↑ 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. Ecosystem Ecology Research Trends. Nova Science Publishers. p. 130. ISBN 978-1-60456-183-8.
  10. ↑ "Grey seal". Wales Nature & Outdoors. BBC Wales. 25 February 2011. Retrieved 20 November 2011.
  11. ↑ "The Grey Seal". Ask about Ireland. Retrieved 20 November 2011.
  12. ↑ Leopold, Mardik F.; Begeman, Lineke; van Bleijswijk, Judith D. L.; IJsseldijk, Lonneke L.; Witte, Harry J.; Gröne, Andrea. "Exposing the grey seal as a major predator of harbour porpoises". Proceedings of the Royal Society 282 (1798).
  13. ↑ van Neer, Abbo; Jensen, Lasse F.; Siebert, Ursula. "Grey seal (Halichoerus grypus) predation on harbour seals (Phoca vitulina) on the island of Helgoland, Germany". Journal of Sea Research 97.
  14. ↑ Hillmer, Angelika (16 February 2015). "Kegelrobben mit großem Appetit auf Schweinswale" [Grey seals with a great appetite for porpoises]. Hamburger Abendblatt (in German).
  15. ↑ 15.0 15.1 "Autumn spectacle: grey seal colonies". BBC Earth. 10 October 2014. Retrieved 3 January 2015.
  16. ↑ Bidggod, Jess (16 August 2013) Thriving in Cape Cod’s Waters, Gray Seals Draw Fans and Foes. New York Times
  17. ↑ Plan to cull 70,000 grey seals gets Senate panel's approval – Newfoundland & Labrador – CBC News. Cbc.ca. 23 October 2012.
  18. ↑ Once again, coastal waters getting seals’ approval Boston Globe. 3 October 2009.
  19. ↑ 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.
  20. ↑ Wozencraft, W. C. (2005). "Order Carnivora". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. ISBN 978-0-8018-8221-0. OCLC 62265494.
  21. ↑ 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.

External links

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