Harp seal

Harp seal
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Clade:	Pinnipedia
Family:	Phocidae
Genus:	Pagophilus Gray, 1844
Species:	P. groenlandicus
Binomial name
Pagophilus groenlandicus Erxleben, 1777
Synonyms
Phoca groenlandica

The harp seal (Pagophilus groenlandicus), also known as Saddleback Seal or Greenland Seal, is a species of

The mature harp seal has pure black eyes. It has a silver-gray fur covering its body, with black

Compared to other phocid seals, the harp seal dives from shallow to moderately deep depths.[2] Dive depth varies with season, time of day and location. In the Greenland Sea sub-population, the average dive rate is around 8.3 dives per hour and dives range from a depth of less than 20 to over 500 m.^[3] Dive duration ranges from less than two minutes to just over 20 minutes.^[3] During the spring and summer when seals forage along the pack ice in the Greenland Sea, most dives are less than 50 m.^[3] In the late fall and winter, dive depth has been found to increase, particularly in the Denmark Strait, where the mean dive depth was found to be 141 m.^[3]

Lactating female harp seals spend about 80% of the time in the water and 20% of the time on the fast ice weaning or near their pups. However, almost half of the time spent in the water is at the surface, well beyond what is expected to recover from dives.^[4] This behavior allows the mother harp seal to conserve energy and avoid the harsh conditions of the fast-ice while remaining near her pup. As with most phocids, she requires vast amounts of energy to ensure sufficient mass transfer to her growing, weaning pup. Harp seals remain within their aerobic dive limit for 99% of dives.^[4]

Thermoregulation

Harp seal insulation changes over the course of a seal's lifetime. Young harp seals rely on a

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.^[2] They can also redirect blood flow from the periphery to minimize heat loss.^[10]

Senses

The harp seal's eyes are large for its body size and contain a large

Harp seals spend relatively little time on land compared with time at sea. They are

Reproduction and development

The harp seal is a fast ice breeder and is believed to have a promiscuous mating system.^[17] Breeding occurs between mid-February and April.^[16] Courtship peaks during mid-March and involves males performing underwater displays, using bubbles, vocalizations, and paw movements to court females.^[18] Females, who remain on the ice, will resist copulation unless underwater.^[18]

Females mature sexually between ages five to six.^[2] Annually thereafter, they may bear one pup, usually in late February.^[2] The gestation period lasts about 11.5 months, with a fetal development phase of 8 months.^[18] There have been reported cases of twin births, but singletons are vastly more common.^[19] 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.^[2]

Harp seal births are rapid, with recorded lengths as short as 15 seconds in duration.^[18] In order to cope with the shock of a rapid change in environmental temperature and undeveloped blubber layers, the pup relies on solar heating, and behavioral responses such as shivering or seeking warmth in the shade or even water.^[18]

Newborn pups weigh 11 kilograms (24 lb) on average and are 80–85 cm (31–33 in) long.

After abandonment, in the post-weaning phase, the pup becomes sedentary to conserve body fat. Within a few days, it sheds its white coat, reaching the "beater" stage.^[2] This name comes from the sound a beater's tail makes as the seal learns to swim.^[19] Pups begin to feed at 4 weeks of age, but still draw on internal sources of energy, relying first on energy stored in the body core rather than blubber.^[18] During this time the ice begins to melt 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.^[2]

Around 13–14 months old, the pups molt again, becoming "bedlamers".^[19] Juveniles molt several times, producing a "spotted harp", before the male adults' harp-marked pelt fully emerges after several years. In females, it does not emerge.^[2]

Seals congregate annually on the ice to

Global harp seal population estimates total around 4.5 million individuals.[20] The number of pups born in the traditional pupping area of the southern Gulf of St. Lawrence was greatly reduced, with an estimated pup production of only 18,300 (95% CI, 15,400-21,200 rounded to the nearest hundred). Another 13,600 (95% CI, 7,700-19,500) pups were born in the northern Gulf. An estimated 714,600 (95% CI, 538,800-890,400) pups were born off the northeastern coast of Newfoundland (Front); accounting for 96% of all pupping in 2017. Combining the estimates from all areas resulted in an estimated total pup production of 746,500 (95% CI, 570,300-922,700).^[21] Due to their dependence on pack ice for breeding, the harp seal range is restricted to areas where pack ice forms seasonally.^[2] The western North Atlantic stock, which is the largest, is located off eastern Canada.^[19] 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 north coast of Russia below the Barents ea. Breeding occurs between mid-February and April, and varies somewhat for each stock.^[16] The three stocks are allopatric and do not interbreed.^[22]

There are two recognised subspecies:^[22]

Image	Subspecies	Distribution
	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;^[23] one individual was located off the north Norwegian coast, 4,640 kilometres (2,880 mi) east northeast of its tagging location.^[24] Their navigational accuracy is high, with good eyesight an important factor.^[23][25] 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.^[26]

More recently, they reached

Harp seals can strand on Atlantic coasts, often in warmer months, due to dehydration and parasite load.^[29] In March 2020, a harp seal was spotted near Salvo, North Carolina.^[30] 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

All three populations are hunted commercially, mainly by Canada, Norway, Russia and Greenland.^[31]

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. Since 2000, harp seals that are targeted during the hunt are often found to be less than a year old, known as "beaters".^[32] In 2006, the St. Lawrence hunt officially started on March 25 due to thin ice caused by the year's milder temperatures. Inuit living in the region hunt mainly for food and, to a lesser extent, commerce.^[31]

In 2019, the Department of Fisheries and Oceans estimated sustainable harvest levels for the next five years. The identified annual Canadian Total Allowable Catch (TAC) levels were 425,000 assuming harvest age structures of 95% young of the year (YOY).^[33] In 2016, 66,800 harp seals and 1,612 grey seals were harvested in Atlantic Canada.^[34]

In 2005, the Independent Veterinarians' Working Group (IVWG) recommended a three-step process for hunters to kill the seals with little or no pain for the seals, as long as the process is completed in rapid succession.^[32] The process is as follows:

1. Stun the seal on the head using tools, such as a rifle or a club, to immediately kill the animal or cause it to permanently lose consciousness.
2. Ensure that step 1 was completed correctly, and the skull is irreversibly damaged.
3. Cut the axillary arteries along both armpits and cut along the belly to prevent blood from reaching the brain, confirming its death.

In 2009, this process was included in both the 'Conditions of License' for the Canadian hunt as well as the Canadian Marine Mammal Regulations.^[32]

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.

The annual quota off the coast of Greenland for 2017–2019 was set at 26,000 1+ animals, where two pups are equivalent to removing one 1+ animal. The total catches of harp seals were 2000 (including 1934 pups) in 2017, 2703 (including 1218 pups) in 2018, and 5813 (including 2168 pups) in 2019.^[35]

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.^[31] The 2004 White Sea TAC was 45,000. The catch was 22,474.^[31]

Population dynamics

Hunting has tremendously affected the population size of harp seals. Over the past 150 years, the harp seal population has fluctuated from over 9 million to as little as 1 million.^[36] As of 2019, the current population is estimated to be 7.6 million.^[37] The Northwest Atlantic populations was found to have decreased by at least 50 percent from 1952 to 1970 ^[38] but nowadays, seal populations all are hunted under quotas and other restrictions.^[39][40][41]

See also

•  Marine life portal
•  Mammals portal
• Paro, a medical robot pet based on the harp seal

References