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Harp seal

Harp seal
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Clade:	Pinnipedia
Family:	Phocidae
Genus:	Pagophilus Gray, 1844
Species:	Pagophilus
Binomial name
Pagophilus Erxleben, 1777
Synonyms
Phoca groenlandica Saddleback seal

From Wikipedia, the free encyclopedia

The harp seal or saddleback seal, Pagophilus groenlandicus 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 Latin, its scientific name translates to "ice-lover from Greenland," and its taxonomic synonym, Phoca groenlandica translates to "Greenlandic seal."

Description

Whitecoated pup

The harp seal pup often has a yellow-white coat at birth due to staining from amniotic fluid, but after one to three days, the coat whitens and remains white for 2–3 weeks, until the first molt. Adolescent harp seals have a silver-gray coat and are spotted with black marks. The mature harp seal has pure black eyes. It has a silver-gray fur covering its body, with black harp or wishbone-shaped markings dorsally. Adult harp seals grow to be 1.7 to 2.0 m (5 ft 7 in to 6 ft 7 in) long and weigh from 115 to 140 kg (254-308 lbs).

Physiology

Harp seals are considered sexually dimorphic, as the males are slightly larger, and more decorated . Males weigh an average of 135 kg (298 lbs.), and reach a length up to 1.9 meters (6.2 ft.), while females weigh an average of 120 kg (264 lbs.) and reach up to 1.8 meters (5.9 ft.). Males generally have a more defined dorsal harp marking and a darker head, while some females never develop the marking and remain spotted.

Thermoregulation

Harp seals combine anatomical and behavioral approaches to managing their body temperatures, instead of elevating their metabolic rate and energy requirements . A thick coat of blubber insulates its body and provides energy when food is scarce or during fasting. Blubber also streamlines its body for more efficient swimming. Brown fat warms blood as it returns from the body surface as well as providing energy, most importantly for newly-weaned pups.

Flippers act as heat exchangers, warming or cooling the seal as needed. On ice, the seal can press its fore-flippers to its body and its hind-flippers together to reduce heat loss. They can also redirect blood flow from the periphery to minimize heat loss.

Senses[edit]

Seal showing hydration rings around the eyes due to lacrimal gland secretions. (Note: the animal pictured is Halichoerus grypus rather than Pagophilus groenlandicus.)

The harp seals' eyes are large for its body size and contain a large spherical lens, which improves its focusing ability. Its pupil is mobile to help it adapt to the intense glare of the Arctic ice. Its retina is rod-dominated and backed by a cat-like and reflective tapetum lucidum, enhancing its low light sensitivity. Its cones are most sensitive to blue-green spectra, while its rods help sense light intensity and may provide some color discrimination. Its cornea is lubricated by lacrimal glands, to protect the eye from sea water damage. The lack of tear glands to drain secretions to the nasal passages contribute to the harp seals "eye rings" on land. This can be an indication of the hydration level of the seal.

On ice, the mother identifies her offspring by smell. This sense may also warn of an approaching predator. Underwater, the seal closes its nostrils and smells nothing.

Its whiskers, called vibrissae, lie in horizontal rows on either side of its snout. They provide a touch sense with labeled line coding, and underwater, also respond to low-frequency vibrations, such as movement.

Diet

The harp seal is carnivorous. They have a diverse diet which includes several dozen species of fish and invertebrates.

Life history

Harp seals spend relatively little time on land compared with time at sea. These are social animals and can be quite vocal in groups. They form large colonies, within which, smaller groups with their own hierarchy are believed to form. Groups of several thousand form during pupping and mating season. Harp seals are able to live over 30 years in the wild.

On the ice, pups call their mothers by "yelling," and "mumble" while playing with others. Adults "growl" and "warble" to warn off conspecifics and predators. Underwater, adults have been shown to use more than 19 types of vocalization.

Reproduction

The harp seal is believed to have a promiscuous mating system. Breeding occurs between mid-February and April.

Females mature sexually between ages five to six. Annually thereafter, they bear one pup, usually in late February. There have been reported cases of twin births, but singletons are vastly more common. The fertilized egg grows into an embryo which remains suspended in the womb for up to three months before implantation, to delay birth until sufficient pack ice is available.

Newborn pups weigh 11 kilograms (24 lbs) on average and are 80–85 centimetres (31–33 in) long. After birth, the mother feeds only her own pup. During the approximately 12-day long nursing period, the mother does not hunt, and loses up to 3 kilograms (7 lb) per day. Harp seal milk contains nearly 60% fat, and pups gain over 2.2 kilograms (4.9 lb) per day while nursing, quickly thickening their blubber layer. During this time, the juvenile's "greycoat" grows in beneath the white neonatal coat, and the pup increases its weight to 80 pounds (36 kg). Weaning is abrupt; the mother turns from nursing to promiscuous mating, leaving the pup behind on the ice. While courtship starts on the ice, mating usually takes place in the water.

The stranded pup cries out for its mother, then becomes sedentary to conserve body fat. Within a few days, it sheds its white coat, reaching the "beater" stage. This name comes from the sound a beater's tail makes as the seal learns to swim. Pups are unable to swim or find food until seven to eight weeks old, around the same time at which the ice melts leaving them vulnerable to polar bears and other predators. This fast can reduce their weight up to 50%. As many as 30% of pups die during their first year, due in part to their early immobility on land.

Juvenile harp seal- a "bedlamer."

Around 13–14 months old, the pup molts again, becoming a "bedlamer". Juveniles molt several times, producing a "spotted harp", before the adults' harp-marked pelt fully emerges after several years (or not all in females).

Seals congregate annually on the ice to molt, pup and breed before migrating to summer feeding grounds. Their lifespan can be over 30 years.

Distribution

The harp seal population is found in three distinct stocks, each of which uses a specific breeding site. The western North Atlantic stock, which is the largest, is located off eastern Canada. This population is further divided into two separate herds based on the breeding location. The Front herd breeds off the coast of Labrador and Newfoundland, and the Gulf herd breeds near the Magdalen Islands in the middle of the Gulf of St. Lawrence. A second stock breeds on the "West Ice" off eastern Greenland. A third stock breeds on the "East Ice" in the White Sea, which is off the coast of Russia. Breeding occurs between mid-February and April, and varies somewhat for each stock. The three stocks are allopatric and don't interbreed.

There are two recognised subspecies:

• Pagophilus groenlandicus groenlandicus – Eastern Canada to Norway
• Pagophilus groenlandicus oceanicus – White and Barents seas

Migration and vagrancy

Harp seals are strongly migratory. The northwest population regularly moves up to 4,000 kilometres (2,500 mi) northeast outside of the breeding season; one individual was located off the north Norwegian coast, 4,640 kilometres (2,880 mi) east northeast of its tagging location. Their navigational accuracy is high, with good eyesight an important factor. They are occasionally found as vagrants, south of their normal range. In Great Britain, a total of 31 vagrants were recorded between 1800 and 1988, (PLAIGARIZED) http://eol.org/pages/1052720/hierarchy_entries/57450874/details

More recently, they reached Lindisfarne in Northumberland in September 1995, and the Shetland Islands in 1987. The latter was linked to a mass movement of harp seals into Norwegian waters; by mid-February 1987, 24,000 were reported drowned in fishing nets and perhaps 30,000,000 (about 10% of the world population) had invaded fjords as far south as Oslo. The animals were emaciated, likely due to humans competing for their prey. (PLAIGARIZED) http://eol.org/pages/1052720/hierarchy_entries/57450874/details#cite_ref-nhsn_12-0 (original articles not found)

Harp seals can strand on Atlantic coasts, often in warmer months, due to dehydration and parasite load. Harp seals often consume snow to stay hydrated, but in mild winters may not have enough available. Several centers are active in seal rescue and rehabilitation, including IFAW, NOAA, and the New England Aquarium. Harp seals are protected by the Marine Mammal Protection Act in the United States.

Seal hunting

Main article: Seal hunting

When threatened, harp seals defense is to freeze, becoming rigid and immobile, essentially making them easy targets for humans.

All three populations are hunted commercially, mainly by Canada, Norway, Russia and Greenland.

In Canada, commercial hunting season is from November 15 to May 15. Most sealing occurs in late March in the Gulf of St. Lawrence, and during the first or second week of April off Newfoundland, in an area known as "the Front". This peak spring period is generally what is referred to as the "Canadian seal hunt". Hunting Canadian whitecoats has been banned since 1987. In 2006, the St. Lawrence hunt officially started on March 25 due to thin ice caused by the year's milder temperatures. Inuit people living in the region hunt mainly for food and, to a lesser extent, commerce. (PLAIGARIZED) https://www.marinemammalscience.org/facts/pagophilus-groenlandicus/

In 2003, the three-year quota granted by the Department of Fisheries and Oceans was increased to 975,000, with a maximum of 350,000 in any two consecutive years. In 2006, 325,000 harp seals, as well as 10,000 hooded seals and 10,400 grey seals were killed. An additional 10,000 animals are allocated to First Nations hunters. (PLAIGARIZED) http://earthsendangered.com/article.asp?ID=4

The Canadian seal hunt is monitored by the Canadian government. Although approximately 70% of the hunt occurs on "the Front", most private monitors focus on the St. Lawrence hunt, due to its more convenient location. (PLAIGARIZED) http://earthsendangered.com/article.asp?ID=4

About 70,000–90,000 animals are taken from the population off the coast of Greenland.

The 2004 West Ice total allowable catch (TAC) was 15,000, almost double the sustainable catch of 8,200. Actual catches were 9,895 in 2004 and 5,808 in 2005. The 2004 White Sea TAC was 45,000. The catch was 22,474. (PLAIGARIZED) https://www.marinemammalscience.org/facts/pagophilus-groenlandicus/

References

Kovacs, K.M. (2015). Pagophilus groenlandicus. The IUCN Red List of Threatened Species doi:10.2305/IUCN.UK.2015-4.RLTS.T41671A45231087.en (in species box)

Original References

1. Jump up ^ Kovacs, K.M. (2015). Pagophilus groenlandicus. The IUCN Red List of Threatened Species doi:10.2305/IUCN.UK.2015-4.RLTS.T41671A45231087.en
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3. Jump up ^ "Nationalgeographic.com". Animals.nationalgeographic.com. Retrieved 2012-09-07.
4. Jump up ^ Miller, Edward H. and Burton, Lauren E. (2001). "It's all relative: allometry and variation in the baculum (os penis) of the harp seal, Pagophilus groenlandicus (Carnivora: Phocidae)" (PDF). Biological Journal of the Linnean Society. 72 (3): 345–355. doi:10.1111/j.1095-8312.2001.tb01322.x.
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8. ^ Jump up to: ^{a b} Ronald, K., & Healey, P. J. (1981). Harp Seal. Chapter 3 in Ridgeway, S. H., & Harrison, R. J., eds. Handbook of Marine Mammals, vol. 2 Seals. Academic Press, London.
9. Jump up ^ Sergeant, D.E. (1973). "Transatlantic migration of a Harp Seal, Pagophilus groenlandicus". Journal of the Fisheries Research Board of Canada. 30: 124–125. doi:10.1139/f73-020.
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