Harbor SealPhoca vitulina出会える場所と時期

The harbor seal is a compact true seal with a rounded head, expressive whiskers and a coat patterned with pale or dark spots. It occurs along temperate and subarctic Northern Hemisphere coasts, including Alaska and New England. Individuals rest ashore between feeding trips, making distant land-based observation possible where haul-outs are accessible. Global abundance masks substantial local differences, and some regional populations have experienced serious declines.

Size

1.2–1.9 m body length

Weight

60–150 kg

Lifespan

20–35 years

Status

Least Concern

Harbor seals gather at haul-outs but usually forage independently. Resting groups remain alert, lifting their heads at unfamiliar sounds or approaching people. Tides, weather and disturbance influence when they come ashore. Pups can swim shortly after birth and nurse for only a few weeks. During breeding, males advertise through vocal displays in the water, while the annual moult increases the importance of undisturbed resting time. Pups are born with an adult-like coat, enabling them to swim and dive within hours of birth, unlike many other seal species. They can often be seen 'bottling' or holding their heads vertically out of the water while resting, especially in calm waters. During the annual moult, which occurs in summer, seals spend significantly more time ashore to conserve energy and promote new fur growth.

• Each seal's spot pattern can help researchers recognize individuals.
• Pups normally shed their white fetal coat before birth.
• Their hind flippers cannot rotate beneath the body for walking.
• Whiskers can detect the water trails produced by moving fish.

In Alaska, late spring through summer combines practical access with pupping or moulting activity in many areas. New England supports year-round viewing at some sites, with strong winter concentrations elsewhere. Local tide schedules often matter more than a broad monthly recommendation. In New England, female seals give birth from late May to early July, making early summer a good time to potentially see pups. Alaskan populations typically pup slightly later, from June through August. The best viewing opportunities from cruise ships in both regions often coincide with lower tides, when more haul-outs are exposed.

Rocky skerries, tidal sandbars, sheltered beaches and estuaries provide resting habitat near feeding grounds. Some Alaskan seals also use floating glacial ice. Haul-outs may disappear beneath rising tides, so visible coastal habitat changes substantially over a single day. While typically coastal, some populations, like those in Alaska's Cook Inlet, can be found many miles upriver. They often return to the same haul-out sites year after year, demonstrating strong site fidelity. Harbor seals generally avoid open, exposed coastlines, preferring the protection of bays and coves.

Harbor seals eat varied fish, squid and crustaceans, adjusting to local prey supplies. Herring, sand lance, cod-like fishes and flatfish can be important. Sensitive whiskers help detect water movements left by prey, supporting hunting when visibility is poor. In New England, seals are known to target seasonally abundant fish like Atlantic mackerel during their migrations. Their diet varies significantly not just by location but also by season, reflecting opportunistic feeding habits. They are also known to consume crustaceans such as crabs and shrimp when fish are less available.

Common name

Harbor Seal

Scientific name

Phoca vitulina

Animal group

Mammals

Size

1.2–1.9 m body length

Weight

60–150 kg

Lifespan

20–35 years

Status

Least Concern

Identification

Compared with grey seals, harbor seals have a shorter, rounded muzzle and V-shaped nostrils rather than a long, heavy, horse-like head. Harbor seals display a wide range of coat colors, from silvery-grey to dark brown, often mottled with darker spots or rings. Their smaller, more compact size compared to grey seals is also a key differentiator, especially when seen side by side. They typically have a more rounded head profile than grey seals, lacking the pronounced 'Roman nose' of the larger species.