Harp seal (Pagophilus groenlandicus)
|Also known as:||Greenland seal|
|Size||Male length: 171 - 190 cm (2)|
Female length: 168 - 183 cm (2)
Average male weight: 135 kg (2)
Average female weight: 120 kg (2)
The harp seal is classified as Least Concern (LC) on the IUCN Red List (1).
The adult harp seal (Pagophilus groenlandicus) is distinguished by the black markings on the upperside of its body, which create a harp or horseshoe shape, giving this species its common name (2) (3) (4). The scientific name for the harp seal, Pagophilus groenlandicus, means ‘ice-lover from Greenland’ (4).
The fur of the adult harp seal is silvery-grey, and may be mottled with black spots in the female. The male typically has a black band running down its sides (2). The wide face of the adult harp seal is black to just behind its closely-set eyes (2) (3) (4), and has well-developed, sensitive whiskers (4). The female harp seal is slightly smaller than the male (4) and has a somewhat paler, spotted face (2). The female harp seal is generally slightly smaller than the male (4). The fore and hind flippers of the harp seal bear black claws (3) (4).
Harp seals pups are known as ‘whitecoats’ due to their thick, white, insulating fur (1) (4), which becomes whiter in the first two weeks of life (3). After two weeks, this fur begins to moult (3), revealing the silver-grey and black fur beneath (1) (4).
The vocalisations of the adult harp seal include trills and clicks, as well as bird-like noises and threatening growls by older individuals, all of which are heard more distinctly during the breeding season (2) (5). Harp seal pups make bawling noises when they are hungry, as well as mumbling sounds while playing with each other (5).
Two subspecies of harp seal are sometimes recognised; Pagophilus groenlandicus groenlandicus and Pagophilus groenlandicus oceanicus, which differ in the location of their breeding grounds (4). However, little genetic variation has been identified between these two subspecies (1), and most scientists divide the harp seal into three distinct populations instead (4).
The harp seal is widespread throughout the North Atlantic and Arctic Oceans (3) (4), with its range stretching from the United States and Canada to Russia, including Greenland, Iceland, Norway, Svalbard and Jan Mayen (1) (2) (4). It is also sometimes found as a vagrant in Denmark, Finland, France, Germany, Spain, the UK and the Faroe Islands (1).
The harp seal inhabits the temporary pack ice of the Arctic for giving birth, moulting and resting (1) (2) (4). It will also forage close to the edge of the ice. The harp seal will preserve natural holes in the pack ice, known as ‘breathing holes’, which it will also use to enter and exit the sea (2). However, this mammal is highly migratory (1) (4) and spends most of its life at sea (4).
The female harp seal reaches sexual maturity between four and eight years old. The male reaches sexual maturity at around the same age as the female, but does not begin to mate until it is older (1). Mating usually occurs on the pack ice, with males fighting for access to females (2). This is followed by a period of delayed implantation, in which the embryo may remain within the female’s womb for up to three months before implanting in the uterus wall, ensuring the birth of pups is synchronised between females, when there is plentiful pack ice (1) (4). The total gestation period of the harp seal is around 11.5 months (1).
The harp seal gives birth between late February and April, with the exact timing varying between populations (1). Females haul out onto the pack ice in large groups (4), where they space themselves 1.5 to 2.5 metres apart (2). A few days after hauling out, the female gives birth to a single pup (2) (4), which generally weighs around 11 to 12 kilograms (2) (4) and is roughly 1 metre long (2). The female nurses the pup for around 12 days with fatty milk. During this time, the pup gains around 2.2 kilograms per day in weight, and will develop a thick blubber layer to protect it against the cold (1) (4). Pups are usually left alone on the ice for long periods, where they typically remain sedentary, and will occasionally melt the ice beneath them, creating an ‘ice cradle’ (1). While nursing, the female will spend up to 85 percent of the day in the water hunting for food (1). Towards the end of the nursing period, the female enters oestrus and mates again (1) (4).
When it is weaned, the pup weighs around 33 kilograms (2). It will remain on the ice for a further six weeks and will fast, losing around 50 percent of its body weight before the pack ice melts and the pup can enter the water and begin to hunt for itself (1) (2) (4). During this time, the pup also begins to moult, exposing its silver-grey juvenile fur (2) (4).
The harp seal is a highly migratory species (1), undergoing an annual migration of between 6,000 and 8,000 kilometres (2) (3). The migration north begins after the breeding season, with the seals returning to the breeding grounds around late autumn (1), in large, noisy groups (3). The migration north is paused for an annual moulting season in the spring, when harp seals haul out in large groups of tens of thousands onto the pack ice (2). This annual moult sees the harp seal develop the characteristic harp-shaped colouration on the upperside of the body, which develops further with each moult. After this period, migration begins once more to the summer feeding grounds (4).
The harp seal is able to move fast on ice, as well as being a powerful swimmer (2). It uses its flippers to propel itself through the water (4), while the hind and fore flippers are also used to fight for access to females, as well as for heat regulation (4). The fore flippers are held close to the body and the hind flippers are held together, reducing the exposed surface area of the body to retain heat. A thick blubber layer also helps the harp seal to insulate itself, as well as being used as a source of energy when prey is not readily available (4).
The diet of the harp seal is extremely variable and is dependent on age, location, season and year (4). Small fish are the main constituent of the adult harp seal’s diet, while pelagic crustaceans are also eaten (1) (2) (4). As a newly-weaned pup, the harp seal forages near the surface of the water, usually taking small crustaceans (2), with juveniles eating a similar invertebrate diet, including euphausiids (Thysanoessa spp.) and amphipods (Parathemisto spp.) (1). Natural predators of the harp seal include the polar bear (Ursus maritimus), orca (Orcinus orca) and Greenland shark (Somniosus microcephalus) (1) (4).
The harp seal has very sensitive ears and eyes, which are supplemented with well-developed whiskers, thought to respond to low frequency vibrations and used to detect prey. The large lens and mobile pupil of the eye give the harp seal its skilled vision, as well as enabling it to see in dark and bright light. The lack of tear ducts in the eyes of the harp seal ensure they are constantly lubricated, protecting the eyes from the seawater (4).
The harp seal’s sense of smell is not as acute as its other senses (2). However, the female is able to use its sense of smell to identify its own offspring while nursing, and may also use it to detect predators on the ice (4).
The accessible breeding grounds and abundant seasonal populations of the harp seal have resulted in heavy hunting of this species throughout history (2). The harp seal was initially hunted for oil, and then for its fur, particularly the white coat of the pup (1). Commercial demand and unregulated trade saw population numbers decrease (4), with reduced catches being reported around the late 1850s in some areas (1). Native people living in the North Atlantic still take a small quantity of harp seals for food and fur (1) (2), with this figure thought to be around 10,000 individuals per year (4). There is still a commercial harvest of harp seals in Canada, although this is not thought to constitute a threat to the future survival of this plentiful species (1).
Although it is now classified as one of the most abundant seal species, the harp seal still faces many threats. Global warming poses the biggest threat to the harp seal (6), as it requires pack ice for moulting, breeding and resting (1). As temperatures rise, pack ice is becoming less extensive and does not remain frozen for as long, reducing suitable habitat for the harp seal (1) (4) (7).
Some of the range of the harp seal is heavily fished, increasing the risk of harp seals being accidentally caught in nets (1) (2) (4). Fisheries have also recently intensified the catch of capelin (Mallotus villosus) and herring (Clupea spp.), reducing the amount of available food for the harp seal population (1) (2) (4). The culling of harp seals was performed in the false belief that they were responsible for the decline in Atlantic cod (Gadus morhua)populations (4), which have declined by 99 percent in the northwest Atlantic Ocean since the 1960s due to overfishing (8).
Environmental contaminants also pose a threat to the harp seal (4), especially oil spills. For example, a previous oil spill on the coast of Canada killed many harp seal pups. Oil development in the Barents Sea also poses a future threat to this species (1).
Quotas are set for the number of harp seals which can be sustainably caught, and hunting licenses and observer permits are issued for commercial hunting of this species in Canada. The quotas in Canada are set by the International Council for the Exploration of the Sea (ICES) (9) and the Northwest Atlantic Fisheries Organisation (NAFO) (10). Russia and Norway are responsible for the management of harp seal populations within the Barents and Greenland Seas (1).
Due to public concern, the commercial hunting of the harp seal has been curtailed in most areas (2). Although this species is not currently considered to be threatened, the IUCN has recommended that it is reassessed in the next decade due to the serious threat from climate change (1).
More information on the harp seal and its conservation:
BBC Wildlife Finder - Harp seal:
Seal Conservation Society:
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- Amphipods: a group of small shrimp-like crustaceans that includes sandhoppers, beach hoppers, and water lice.
- Crustaceans: diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
- Delayed implantation: the process of a fertilised egg remaining unattached in the uterus for a period of time, therefore delaying the start of development.
- Euphausiids: a group of shrimp-like marine crustaceans that includes krill.
- Genetic variation: the variety of genes within a particular species, population or breed causing differences in morphology, physiology and behaviour.
- Gestation: the state of being pregnant; the period from conception to birth.
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
- Moult: periodic shedding of (usually) the outermost body covering (such as feathers, fur or skin) during growth and development, or at specific times of the year.
- Oestrus: the time of ovulation (release of an egg from the ovary) in female mammals, when the female becomes receptive to males. Also known as ‘heat’.
- Pack ice: sea ice that floats on the surface of the water. Often formed from large pieces of ice that consolidate into a single ice mass, pack ice typically moves with currents, tides and wind.
- Pelagic: relating to or inhabiting the open ocean.
- Subspecies: a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
- Vagrant: an individual found outside the normal range of the species.
IUCN Red List (January, 2012)
- Nowak, R.M. (1999) Walker's Mammals of the World. Johns Hopkins University Press, Baltimore, Maryland.
- Burnie, D. (2001) Animal. Dorling Kindersley, London.
- Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (2008) Encyclopedia of Marine Mammals.Second Edition. Academic Press, San Diego, California.
- Kovacs, K.M. (1987) Maternal behaviour and early behavioural ontogeny of harp seals, Phoca groenlandica. Animal Behaviour, 35: 844-855.
- Johnston, D.W., Friedlaenger, A.S., Torres, L.G. and Lavigne, D.M. (2005) Variation in sea ice cover on the east coast of Canada from 1969 to 2002: climate variability and implications for harp and hooded seals. Climate Research, 29: 209-222.
- Macdonald, D. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.
- Hutchings, J.A. (2006) Ecological and fisheries sustainability: common goals uncommonly achieved. In: Lavigne, D.M. (Ed.) Gaining Ground: In Pursuit of Ecological Sustainability. International Fund for Animal Welfare, Guelph, Canada and the University of Limerick, Limerick, Ireland.
International Council for the Exploration of the Sea (February, 2012
Northwest Atlantic Fisheries Organization (February, 2012)