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By Matthew Steinway
Geographic Range
Phoca vitulina is the most widely distributed pinniped. This species is found in temperate, subarctic, and arctic coastal areas on both sides of the North Atlantic and North Pacific oceans. Five separate subspecies have been identified, each common to a specific coastal region.
Biogeographic Regions:
nearctic 
(native ); palearctic (native ); atlantic ocean (native ); pacific ocean (native ).
Other Geographic Terms:
holarctic .
Habitat
Harbor seals bask and sleep on coastal islands, ledges, and beaches and sandbars that are uncovered at low tide. They stay close enough to water to facilitate feeding and mating.
These animals are found in the following types of habitat:
temperate ; saltwater or marine .
Aquatic Biomes:
coastal .
Physical Description
(110 to 374 lbs)
(6.56 ft)
Harbor seals can be up to 6 feet long and weigh up to 375 pounds, males characteristically being slightly larger than females. The rounded, fusiform body is covered by a coat made of thick, short hairs that range from nearly white with dark spots to black or dark brown with white rings. The dorsal surface is usually more densely covered with spots or rings than the ventral surface.
The limbs of the harbor seal have been modified into flippers. The foreflippers (pectoral flippers) are composed of 5 digits of similar length and webbed together. Claws on the foreflippers are used for scratching, grooming, and defense. The hind flippers also have 5 digits; however, the first and fifth digits are long and stout, while the middle digits are shorter and thinner. The hind flippers propel the seal forward by moving side to side. On land, the harbor seal moves by undulating in a caterpillar-like motion.
Some key physical features:
endothermic ; bilateral symmetry .
Sexual dimorphism: male larger.
Reproduction
While the mating season varies between the different subspecies, it generally occurs from late spring through fall.
Pre-mating behavior is exhibited by both males and females, such as rolling, bubble-blowing, and mouthing each other's necks. This behavior ends once mating begins. Males initiate behavior by chasing, playfully biting, and embracing females. Females respond, and the act of copulation usually takes place in the water. One male may mate with multiple females. Harbor seals return to the same breeding grounds every year.
Mating systems:
polygynous .
It is believed that males become sexually mature once a weight of around 75 kg is achieved; females mature at about 50 kg. This occurs between 3 and 7 years of age for males and at 2 to 6 years for females. While the mating season varies between the different subspecies, it generally occurs from late spring through fall. About 6 weeks after they give birth to their previous year's pups, the females come into estrus. The gestation period lasts between 9 and 11 months, and usually only 1 pup is born each year.
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous ; delayed implantation .
Behavior
Harbor seals are usually solitary animals, with reproduction and "haul outs" being the only exceptions. Seals "haul out" onto land for various reasons including resting, thermoregulating, giving birth, nursing, molting, and facilitating digestion. Another possible reason for haul outs is protection from predators by being in a group. During haul outs, adult individuals do not make physical contact with each other and respond to touching angrily. Younger seals interact with each other along the edges of the group and stay away from the adults.
Aggression is shown by growling, snorting, threateningly waving a foreflipper, and head-thrusting, which is a sharp, rapid retraction of the neck. Vocalization occurs only when they feel threatened.
Key behaviors:
natatorial ; motile ; nomadic ; solitary .
Food Habits
The diet varies with the season and region. Their food consists of crustaceans, mollusks, squid, and a variety of fish. Harbor seals do not chew their food; they either tear it into chunks or swallow it whole. Their molars allow them to crush hard objects like shells and crustaceans. Adults consume around 4.5 to 8.2 kg of food per day, which is 5-6% of their body weight.
Primary Diet:
carnivore (piscivore , eats non-insect arthropods, molluscivore ).
Animal Foods:
fish; mollusks; aquatic crustaceans.
Predation
- great white sharks (Carcharodon carcharias)
- killer whales (Orcinus orca)
Harbor seals are eaten by great white sharks and killer whales.
Economic Importance for Humans: Negative
Harbor seals often interfere with commercial fisheries, eating the fish that have been caught in nets and becoming trapped in the nets themselves.
Economic Importance for Humans: Positive
Harbor seals are hunted primarily for their skins, oil, and meat. They can also be used in the production of jewelry and trinkets and as meat for mink feeding. Phoca vitulina can also serve as tourist attractions at aquariums and can be used in experimental research.
Ways that people benefit from these animals:
food ; body parts are source of valuable material; ecotourism .
Conservation Status
IUCN Red List: [link]:
Lower Risk - Least Concern.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
The U.S. Marine Mammal Protection Act of 1972 made it illegal to hunt or harass any marine mammal in U.S. waters. In Canada, Norway, and the United Kingdom, it is legal to shoot harbor seals to protect fisheries or fish farms. Many fish species eaten by harbor seals are also commercially fished, and the seals often become entangled and drown in fishing nets and gear.
Other Comments
The 5 subspecies and there habitats are: eastern Atlantic harbor seal (P. v. vitulina); western Atlantic harbor seal (P. v. concolor); eastern Pacific harbor seal (P. v. richardsi); western Pacific harbor seal (P. v. stejnegeri); and Ungava seal (P. v. mellonae).
Contributors
Matthew Steinway (author), University of Michigan.
Phil Myers (editor), Museum of Zoology, University of Michigan.
