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The harbor (or harbour) seal ( Phoca vitulina), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinnipeds (walruses, eared seals, and true seals), they are found in coastal waters of the northern Atlantic Ocean and Pacific Ocean oceans, Baltic Sea and North Sea seas.
Harbour seals are brown, silvery white, tan, or grey, with distinctive V-shaped nostrils. An adult can attain a length of 1.85 m (6.1 ft) and weigh up to . Blubber under the seal's skin helps to maintain body temperature. Females outlive males (30–35 years versus 20–25 years). Harbor seals stick to familiar resting spots or haulout sites, generally rocky areas (although ice, sand, and mud may also be used) where they are protected from adverse weather conditions and predation, near a foraging area. Males may fight over mates under water and on land. Females bear a single pup after a nine-month gestation, which they care for alone. Pups can weigh up to and are able to swim and dive within hours of birth. They develop quickly on their mothers' fat-rich milk, and are weaned after four to six weeks.
The global population of harbor seals is 350,000–500,000, but the freshwater subspecies Ungava seal in Northern Quebec is endangered. Once a common practice, Seal hunting is now illegal in many nations within the animal's range.
Seals in the United Kingdom are protected by the 1970 Conservation of Seals Act, which prohibits most forms of killing. In the United States, the Marine Mammal Protection Act of 1972 prohibits the killing of any , and most local ordinances, as well as NOAA, instruct people to leave them alone unless serious danger to the seal exists.
Reproduction 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 (orcas) and . Haul out sites in California include urban beaches and from time to time they can be seen having a nap on the beach in all of San Francisco Bay, which would include the conurbation of Richmond, Oakland, and San Francisco, the Greater Los Angeles area, which would include Santa Barbara, the city of Los Angeles itself, and Long Beach, and all of San Diego Bay, most famously beaches near La Jolla.
Considerable scientific inquiry has been carried out by the Marine Mammal Center and other research organisations beginning in the 1980s regarding the incidence and transmission of diseases in harbor seals in the wild, including analysis of phocine herpesvirus.Goldstein, T., Mazet, J.A.K., Gulland, F.M.D., Rowles, T., Harvey, J.T., Allen, S.G., King, D.P., Aldridge, B.M., Stott, J.L. (2004). The transmission of phocine herpesvirus-1 in rehabilitating and free-ranging Pacific harbor seals ( Phoca vitulina) in California. Veterinary Microbiology; 103:131–141. In San Francisco Bay, some harbor seals are fully or partially reddish in colour, possibly caused by an accumulation of trace elements such as iron or selenium in the ocean, or a change in the hair follicles.
Although some of the largest harbor seal pupping areas are found in California, they are also found north along the Pacific Coast in Oregon, Washington, British Columbia and Alaska. Large populations move with the season south along the west coast of Canada and may winter on the islands in Washington and Oregon. Pupping is known to occur in both Washington and Oregon as of 2020. People are advised to stay at least 50m (164 ft) away from harbor seals that have hauled out on land, especially the pups, as mothers will abandon them when there is excessive human activity nearby.
As of 2020, however, the seals have returned. They never were extirpated from Canada and certain pockets of the Maine coast, and thus an important mother population was created from whence the species could reclaim the home of their ancestors. Currently, they are sighted as far south as the barrier islands of North Carolina on a regular basis, with Massachusetts being the southernmost point of known pupping areas along the Atlantic Coast. Harbor seals move south from eastern Canadian waters to breed along the coast of Maine, Cape Cod, and the South Shore in Massachusetts in May and June, and return northward in fall. Others will head south from these areas to "vacation" in warmer waters, particularly young seals unable to compete with adults for food and territory; they do not return north until spring.
One park ranger in New York City, which is in the centre of its West Atlantic range, says that "New York is like their Miami resort". This refers to the habit of young seals leaving Cape Cod and even some Arctic waters to inhabit the harbor in winter. In 2018 the New York Post reported that the harbor is now "cleaner than it has been in 110 years", and since the first decade of the 21st century, the harbor seal has found the old turf of its ancestors to be a land of plenty and the water to be livable. Within sight of the New York skyline, known colonies of harbor seals are found on Hoffman Island and Archived at Ghostarchive and the
target="_blank" rel="nofollow"> Wayback Machine: as well as portions of Red Hook and Staten Island, readily hauling out every from October until very early May. Known favourite foods of the seal are returning in grand numbers to New York Harbor as well as nearby New Jersey, from Raritan Bay all the way down the entire Jersey Shore, with schools of mossbunker regularly attracting harbor seals, their cousins the grey seals, dolphins and, most recently, whales. Both the northern and southern shores of Long Island have a reliable population of harbor seals as well as greys, where they will take sand lance as well as some species of crab as part of their diet.
| Europe and northwestern Asia. |
| inhabit eastern North America. The validity of this subspecies is questionable, and not supported by genetic evidence. They might be part of the Eastern Atlantic subspecies. |
| found in eastern Canada in Freshwater seal |
| western North America. |
| Eastern Asia. Currently not recognised as a separate subspecies, but part of P. v. ricardsi |
Birthing of pups occurs annually on shore. The timing of the pupping season varies with location,Temte, J. L. (1994). Photoperiod control of birth timing in harbour seal ( Phoca vitulina). Journal of Zoology (London) 233: 369–384. 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.Daryl Boness and W. Don Bowen, "The Evolution of Maternal Care in Pinnipeds", BioScience. 46(9):645-654. 1996. 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 kg, 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 life cycle, and can be disturbed when substantial human presence occurs.Patrick Sullivan, Gary Deghi and C.Michael Hogan, Harbor Seal Study for Strawberry Spit, Marin County, California, Earth Metrics file reference 10323, BCDC and County of Marin, 23 January 1989. The timing of onset of molt depends on the age and sex of the animal, with yearlings molting 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, and if necessary managed, in known locations of seal haul out.
In comparison to many pinniped species, and in contrast to otariid pinnipeds, harbor seals are generally regarded to be more vocally reticent. However, they do use non-harmonic vocalisations to maintain breeding territories and to attract mates during specified times of year, and also during mother and pup interactions.
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.
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