|Where the harbor seal lives|
The harbor seal (Phoca vitulina), also called the common seal, is a true seal. They are found in coastal waters of the northern Atlantic and Pacific ocean as well as Baltic and North Seas making them the most wide-ranging of the pinnipeds (walruses, eared seals, and true seals).
The females live longer than the males and females usually live to be 30 to 35, while males usually live up to 20 or 25 years old.
Individual harbor seals possess a unique pattern of spots, either dark on a light background or light on a dark. They vary in color from brownish black to tan or grey; underparts are generally lighter. The body and flippers are short, heads are rounded. Nostrils appear distinctively V-shaped. As with other true seals, there is no pinna (ear flap). An ear canal may be visible behind the eye. Including the head and flippers, they may reach an adult length of 1.85 meters (6.1 ft) and a weight of 55 to 168 kg (120 to 370 lb). Females are generally smaller than males.
There are an estimated 350,000–500,000 harbor seals worldwide.
Habitat and diet
Harbor seals prefer to frequent familiar resting sites. They may spend several days at sea and travel up to 50 km in search of feeding grounds, and will also swim 100+ miles upstream into fresh water in large rivers. Resting sites may be both rugged, rocky coasts, such as those of the Hebrides or the shorelines of New England, or sandy beaches.
Harbor seals frequently congregate in harbors, sandy intertidal zones, and estuaries in pursuit of prey fish such as salmon, menhaden, anchovy, sea bass, herring, mackerel, cod, whiting and flatfish, and occasionally shrimp, crabs, mollusks, and squid. Atlantic subspecies of either Europe or North America also exploit deeper-dwelling fish of the genus Ammodytes as a food source and Pacific subspecies have been recorded occasionally consuming fish of the genus Oncorhynchus. Although primarily coastal, dives to over 500 m have been recorded. Harbor seals have been recorded to attack, kill and eat several kinds of duck.
Behavior, survival, and reproduction
Harbor seals are solitary, but are gregarious when hauled out and during the breeding season, though they do not form groups as large as some other seals. When not actively feeding, they haul to rest. They tend to be coastal, not venturing more than 20 km offshore. Both courtship and mating occur under water. The mating system is not known, but thought to be polygamous. Females give birth once per year, with a gestation period around nine months. Females have a mean age at sexual maturity of 3.72 years and a mean age at first parturition of 4.64. Pregnancy rate of females was 92% from age 3 to age 36, with lowered reproductive success after the age of 25 years.
Birthing of pups occurs annually on shore. The timing of the pupping season varies with location, occurring in February for populations in lower latitudes, and as late as July in the subarctic zone. The mothers are the sole providers of care, with lactation lasting 24 days. Researchers have found males gather under water, turn on their backs, put their heads together, and vocalize to attract females ready for breeding. The single pups are born well developed, capable of swimming and diving within hours. Suckling for three to four weeks, pups feed on the mother's rich, fatty milk and grow rapidly; born weighing up to 16 kilograms, the pups may double their weight by the time of weaning.
Harbor seals must spend a great deal of time on shore when moulting, which occurs shortly after breeding. This onshore time is important to the lifecycle, and can be disturbed when substantial human presence occurs. The timing of onset of moult depends on the age and sex of the animal, with yearlings moulting first and adult males last. A female mates again immediately following the weaning of her pup. Harbor seals are sometimes reluctant to haul out in the presence of humans, so shoreline development and access must be carefully studied in known locations of seal haul out.
Annual survival rates were calculated at 0.91 for adult males, and 0.902 for adult females. Maximum age for females was 36 and for males 31 years.
Harbor seals in North America
The California population of subspecies P. v. richardsi amounted to about 25,000 individuals as of 1984. Pacific harbor seals or Californian harbor seals are found along the entire Pacific Coast shoreline of the state. They prefer to remain relatively close to shore in subtidal and intertidal zones, and have not been seen beyond the Channel Islands as a pelagic form; moreover, they often venture into bays and estuaries and even swim up coastal rivers. They feed in shallow littoral waters on herring, flounder, hake, anchovy, codfish, and sculpin.
Breeding occurs in California from March to May, with pupping between April and May, depending on local populations. As top-level feeders in the kelp forest, harbor seals enhance species diversity and productivity. They are preyed upon by killer whales (orcas) and white sharks.
Although some of the largest pupping areas harbor seals are found in California, they are found north along the Pacific Coast of the US in both Oregon and Washington. Large populations move with the season south along the West Coast of Canada and may winter on the islands in Washington and Oregon.
Harbor seals are normally found along the Atlantic Coast and islands from Maine southward to Massachusetts. Occasionally, areas further south in Connecticut, Long Island, New Jersey, and even North Carolina have reported small populations or stranded seals have been found in and near islands or on beaches. Harbor seals move south from eastern Canadian waters to breed along the coast of Maine in May and June, and return northward in fall. Massachusetts is the southernmost point of known pupping areas along the Atlantic Coast.
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Harbor seal in Svalbard
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