The Spotted seal (scientific name: Phoca largha) is one of nineteen marine mammal species within the family of true seals. Together with the families of eared seals and walruses, True seals form the group of marine mammals known as pinnipeds. As their name suggests, spotted seals have characteristic pelage markings of dark irregular spots on a lighter background.
Spotted seals are intermediate sized phocid seals. Males measure from 1.5 to 2.1 meters in total length and females from 1.4 to 1.7 meters. Males weigh from 85 to 150 kg and females from 65 to 115 kg. Average sizes vary among populations.
Spotted seal. Source:M. Cameron/NOAA
Kingdom: Animalia (Animals)
Like all true seals, they have no external ears. Instead, only a small ear opening behind the eyes is visible.
The furred hind flippers are short and extend behind their body to provide thrust when swimming. The smaller, front flippers act mainly as rudders and help with movement on land or ice. Each of the five digits on the front limbs has a claw, which also helps with short distance travel on land.
The fur is dense, but spotted seals rely on a heavy layer of blubber to keep them warm.
Reproduction and lifespan
Breeding takes place in the spring. Breeding pairs meet about 10 days before the pregnancy of the last season reaches term, then mate underwater.
Implantation of the embryo is delayed until after the current year's pup is born. Spotted seal pups are born between early April and early May. The peak of the pupping season is in the first part of April.
Newborns have body mass between seven to twelve kilograms, and measure from 75 to 90 centimeters in length. Pups are born with a dense coat of whitish hair that provides insulation until blubber is developed, this fur is shed by four to five weeks of age, the time at which pups are weaned. Pups can swim if forced to, but prefer not to until the time of weaning, at which time they can dive to depths of over 300 meters to feed. Sexual maturity is reached at three to four years of age in females, four to five years of age in males.
Females nurse and care for their young until they are weaned at four to five weeks of age. Spotted seals can live to at least 35 years, most average 25 years in the wild. Approximately 45% of all pups die before their first year of age.
Gregarious animals, spotted seals form large groups of up to several thousand when they haul out for pupping and molting season. At other times they may be more solitary. They are wary animals that crawl on ice floes and are difficult to approach in the open.
Distribution and habitat
Spotted seals are commonly found in habitats along the continental shelves of the North Pacific Ocean and Bering Sea. They are also found on the ice flows of the Beaufort, Chukchi, and Okhotsk Seas, where breeding mainly occurs. They migrate as far south as the northern parts of the Huanghai, and the western Sea of Japan.
Spotted seals are strongly associated with sea ice from fall until late in the spring when they gather among the remaining ice packs. They gather on land when no ice is available.
Predators and prey
When threatened by terrestrial predators, spotted seals take to the water in groups. They swim in flocks, like birds, turning, and twisting as a group in the water. Known predators of spotted seals include sharks, killer whales, walruses, Steller sea lions, polar bears, brown bears, wolves, foxes and some large birds.
The diet of spotted seals includes crustaceans, cephalopods, and fish (herring, capelin, cod, and especially pollock). Spotted seals can make vast feeding trips of hundreds of miles from the Chukchi Sea coast to the western Chukchi Sea, then returning.
Smaller seals feed mostly on small pollock (Theragra chalcogramma) while older seals also feed on larger fishes. Seal predation may affect pollock stocks, as well as those of other prey animals, but these effects may be complex and is not well understood.
Spotted seals are not considered endangered. Populations of spotted seals have remained relatively stable in the territorial waters of the North American continent countries due to conservation efforts. Activities such as those related to oil, gas, coal, and mineral resource development need to be regulated to reduce potential impacts on important spotted seal habitats. In China, spotted seals are listed as a nationally endangered animal.
Economic importance for humans
Spotted seals are an important species for the native Eskimo subsistence hunter, who use every bit of the animal for food, clothes, fuel, and for other purposes. Spotted seal pups may be hunted for their fur. Spotted seals are known to raid fishing nets in some incidences.
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