page_title: Harbor seal
section_title: Behavior, survival, and reproduction
hierarchical_section_title: Harbor seal / Behavior, survival, and reproduction
caption_attribution_description: Phoca vitulina&#160;; Colony (Helgoland/Düne) Dansk: Spættet sæl Deutsch: Seehund English: Common Seal Esperanto: Ordinara foko Suomi: Kirjohylje Français&#160;: Phoque commun Magyar: Borjúfóka Íslenska: Landselur Italiano: Phoca vitulina 日本語: ゼニガタアザラシ Lietuvių: Paprastasis ruonis Nederlands: Gewone zeehond Norsk bokmål: Steinkobbe Polski: Foka pospolita Português: Foca-comum Svenska: Knubbsäl
context_page_description: The harbor seal, 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 pinniped, they are found in coastal waters of the northern Atlantic, Pacific Oceans, Baltic and North Seas.
  Harbor seals are brown, silvery white, tan, or gray, with distinctive V-shaped nostrils. An adult can attain a length of 1.85 m and a mass of up to 168 kg. Blubber under the seal's skin helps to maintain body temperature. Females outlive males. Harbor seals stick to familiar resting spots or haulout sites, generally rocky areas 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 16 kg 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 subspecies in certain habitats are threatened.
context_section_description: 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. 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. Both courtship and mating occur under water. 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.
  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 utilize non-harmonic vocalizations 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.
caption: Harbor seal colony in Helgoland, Germany
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