Harp seal
The Harp Seal (Pagophilus groenlandicus), also known as Saddleback Seal or Greenland Seal, 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 Greek, its scientific name translates to "ice-lover from Greenland," and its taxonomic synonym, Phoca groenlandica translates to "Greenlandic seal."[2]
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 to 309 lb).[3] 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 turns white and stays white for 2–3 weeks, until the first molt.[2] Adolescent harp seals have a silver-gray coat spotted with black.
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.[2]
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.[4] Dive duration ranges from less than two minutes to just over 20 minutes.[4] During the spring and summer when seals forage along the pack ice in the Greenland Sea, most dives are less than 50 m.[4] 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.[4]
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.[5] 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.[5]
Harp seals combine anatomical and behavioral approaches to managing their body temperatures, instead of elevating their metabolic rate and energy requirements.[6] Their lower critical temperature is believed to be under −10 degrees Celsius in air.[7] Blubber insulates the Harp seal's core but does not insulate the flippers to the same extent. Instead, the flippers have circulatory adaptations to help prevent heat loss.[8] A thick coat of blubber insulates its body and provides energy when food is scarce or during fasting.[9] 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.[2]
