Harp Seal

The mature harp seal has pure black eyes. It has a silver-grey fur covering its body, with black harp- or wishbone-shaped markings dorsally, accounting for its common name. 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). The harp seal pup has a white coat for the first 2–3 weeks until the first moult, when it is replaced by a black-dotted silver to grey coat. Pups acquire their characteristic pattern once they near sexual maturity. In males, the transition to the harp-pattern tends to be abrupt, while in females it may be gradual and span years. Some females may never lose all their spots or not fully develop the harp-pattern. Harp seals show little sexual dimorphism in size, with males being slightly larger.

Physiology. The harp seal is a modest diver. 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 m (66 ft) to over 500 m (1,600 ft). Dive duration ranges from less than two 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 50 m (160 ft). …

Global harp seal population estimates total around 4.5 million individuals. Due to their dependence on pack ice for breeding, the harp seal range is restricted to areas where pack ice forms seasonally. The western North Atlantic stock or population, 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 north coast of Russia below the Barents Sea. Breeding occurs between mid-February and April, and varies somewhat for each stock. The three stocks are allopatric and do not interbreed. Some individuals from the Greenland Sea sub-population have been observed to forage in the Barents Sea alongside the White Sea sub-population during late summer and fall. As of 2017 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% confidence interval (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. …

The harp seal is a fast ice breeder and is believed to have a promiscuous mating system. Breeding occurs between mid-February and April. While courtship starts on the ice, mating usually takes place in the water. Courtship peaks during mid-March and involves males performing underwater displays, using bubbles, vocalizations, and paw movements to court females. Females, who remain on the ice, will resist copulation unless underwater. Females become sexually mature between ages five to six. Annually thereafter, they may bear one pup, usually in late February. The gestation period lasts about 11.5 months, with a fetal development phase of 8 months. 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. Harp seal births are rapid, with recorded lengths as short as 15 seconds in duration. 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 behavioural responses such as shivering or seeking warmth in the shade or even water.

Newborn pups weigh 11 kilograms (24 lb) on average and are 80–85 cm (31–33 in) long. After birth, the mother feeds only her own pup. …

Harp seals spend relatively little time on land compared with time at sea. They are social animals and can be quite vocal in groups. Within their large colonies, smaller groups with their own hierarchies form. Groups of several thousand form during pupping and mating season. Harp seals can live over 30 years in the wild. On the ice, pups call their mothers by "yelling", and "mumble" while playing with other pups. Adults "growl" and "warble" to warn off conspecifics and predators. Underwater, adults have been recorded using more than 19 types of vocalization during courting and mating.

Reproduction and development. The harp seal is a fast ice breeder and is believed to have a promiscuous mating system. Breeding occurs between mid-February and April. While courtship starts on the ice, mating usually takes place in the water. Courtship peaks during mid-March and involves males performing underwater displays, using bubbles, vocalizations, and paw movements to court females. Females, who remain on the ice, will resist copulation unless underwater. Females become sexually mature between ages five to six. Annually thereafter, they may bear one pup, usually in late February. The gestation period lasts about 11.5 months, with a fetal development phase of 8 months. There have been reported cases of twin births, but singletons are vastly more common. …