Male harbor seals are slightly larger than females, weigh up to 245 pounds (110 kg), and measure anywhere from about 5.6-6.3 feet (1.7 to 1.9 m) in length. Harbor seals in Alaska and the Pacific Ocean are generally larger than those found in the Atlantic Ocean. Harbor seals' color varies but they often have a blue-gray back with light and dark speckling. They have short, concave, dog-like snouts and tend to haul out on land in a banana-like fashion with their head and rear flippers elevated. Harbor seals eat a variety of prey consisting mainly of fish, shellfish, and crustaceans. Researchers have found that seals complete both shallow and deep dives during hunting depending on the availability of prey (Tollit et al. 1997). Harbor seals mate at sea and females give birth during the spring and summer; although, the "pupping season" varies with latitude. Pups are nursed for an average of 24 days and are ready to swim minutes after being born.
Harbor seals live in temperate coastal habitats and use rocks, reefs, beach, and drifting glacial ice as haul out and pupping sites. Harbor seals haul out on land for rest, thermal regulation, social interaction, and to give birth. Seals also haul out to avoid predators. Studies have shown that seals in groups spend less time scanning for predators than those that haul out alone.
Harbor seals are generally non-migratory and occur on both the North American east and west coasts. On the east coast, harbor seals are found from the Canadian Arctic to southern New England, New York and occasionally end up in the Carolinas. On the west coast, harbor seals are found in the coastal and estuarine waters off Baja California, north to British Columbia, west through the Gulf of Alaska and in the Bering Sea.
The natural threats to harbor seals are sharks - principally the great white shark - orcas, and polar bears. Man is also a threat, as the seals are incidentally captured in fishing gear (gillnets, trawls, purse seines, and weirs), and are also victims of boat strikes, oil spill exposure, chemical contaminants, and power plant entrainment. On land, humans may "harass" and disturb hauled out harbor seals while the seals are resting.
Andre, a harbor seal found and adopted by residents in Rockport, Maine in 1961, spent his years migrating between Rockport and Boston's New England Aquarium, delighting thousands; his story was later made into major motion picture, albeit with a sea lion in the starring role. 
- New York Times article on the death of the harbor seal Andre
- Hoover, A.A. 1988. Harbor seal Phoca vitulina. Selected Marine Mammals of Alaska: Species Accounts with Research and Management Recommendations (J.W. Lentfer, ed), pp. 125-157. Marine Mammal Commission, Washington, DC.
- Tollit, DJ., S.PR. Greenstreet, and P.M. Thompson. 1997. "Prey Selection by harbor seals, Phoca vitulina, in relation to variation in prey abundance". Canadian Journal of Zoology 75, 1508-1518.
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