Harp Seal

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

Harp Seals are extremely agile swimmers, able to catch a wide variety of fish and crustaceans. They can stay underwater for 15 minutes. Their thick coats of blubber not only keep them warm but also serve as a source of nutrition when food resources are thin. They have proportionally large eyes, giving it excellent vision. Underwater, its nostril slits close so it can’t smell anything, but this is made up for by the use of its vibrissae (whiskers) which are sensitive to touch and possibly to vibrations caused by the movement of prey. They are able to dive as deep as 270 metres.

## Physiology

Harp seals are considered sexually dimorphic, as the males are slightly larger, and more decorated. Males weigh an average of 135 kg (298 lb), and reach a length up to 1.9 m (6.2 ft), while females weigh an average of 120 kg (260 lb) and reach up to 1.8 metres (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.

**Diving**

Compared to other phocid seals, the harp seal dives from shallow to moderately deep depths. 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 500m. Dive duration ranges from less than 2 minutes to just over 20 minutes. During the spring and summer when seals forage along the pack ice in the Greenland Sea, most dives are less than 50m. 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 141m.

Lactating female harp seals spend about 80% of the time in the water and 20% of the time on the fast-ice weaning or in close proximity to their pups. However, almost half of the time spent in the water is at the surface, which is well beyond what is expected to recover from their dives.[5] This behavior allows the mother harp seal to conserve energy and avoid the harsh conditions of the fast-ice while remaining in close proximity to its pup. As with most phocids, the mother harp seal requires vast amounts of energy to ensure sufficient mass transfer to the growing, weaning pup, however they still remain within their aerobic dive limit for 99% of dives.

**Senses**

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.

Similar to most pinnipeds, the harp seal exhibits a carnivorous diet. They have a diverse diet which includes several dozen species of fish and invertebrates. The White Sea population migrates northward in the summer to forage extensively in the Barents Sea, where common prey items include krill, capelin (*Mallotus villosus),* herring (*Clupea harengus),* flat fish and Gadiformfish. Harp seals are known to exhibit some preference for prey, though the driving force behind the composition of their diet is prey abundance. Diet and abundance analysis of the Svalbard population found that this population feeds predominantly on krill, followed closely by polar cod (*Arctogladus glacialis)*. Some individuals from the Greenland Sea sub-population have been recorded to forage in the Barents Sea alongside the White Sea sub-population during the late summer and fall. The diet of the Barents Sea population is dominated by herring and polar cod but these seals show a negative preference towards krill and amphipods, which is thought to be a result of their tendency towards deeper dives. In the western N. Atlantic population segment, foraging takes place both near and offshore of Newfoundland. The most preferred prey items include Arctic cod (*Boreogadus saida)*, capelin, Greenland halibut (*Reinhardtius hippoglossoides)*and American plaice (*Hippoglossoides platessoides*). As in other populations and foraging areas, diet varies with distance from shore. Arctic cod yields a higher diet percentage nearshore, while capelin is more prominent offshore. However, capelin is understood as the preferred prey item in both locales.

## Behavior

Harp Seals are very social come mating season, forming huge colonies on land. They also often travel and hunt in large pods spaning from dozens to hundreds. They have a wide variety of calls, some for warning other seals off, others used to attract a mate.

## Reproduction

Harp Seals migrate south when the winter months start rolling in. While males court females on land, the actual mating occurs in the water. Males fight for mating rights by biting and beating each other with their flippers. Dominant males will mate with several different females. The pregnancy lasts about 11 months, the pups being born around February. The pups, born with white fur, are about 11 kg in weight and around 80 centimetres in length. The nursing period only lasts about 10 days during which the mother does not feed herself and the pup grows quickly, fattening up to nearly 40 kg. The mother then abruptly leaves to commence mating, leaving the pup behind. The pup will become sedentary to conserve its stores of fat. They can lose up to half of their body weight during this period of 7 or 8 weeks, until they have learned to properly swim and hunt for themselves.