Harbor Seal

Harbor seals haul out or rest on rocks, sand bars, mud flats, sea ice, and a variety of human-made structures. They haul out to regulate their body temperature, molt, socialize with other seals, give birth, and nurse their pups. They stay close to the water in case they need to quickly escape from threats.

Males begin reproducing once they reach 4 to 6 years old while females begin reproducing when they reach 3 to 5 years old. Harbor seals mate in the water. Females are pregnant for about 10 months. The peak birth time varies by location from mid March to early September. While at sea, harbor seals are most often seen alone, but they are sometimes spotted in small groups. Females sometimes raise their pups in nurseries with groups of mothers and their young. In doing so they can better protect themselves and their young from predators.

Females give birth to a single pup. Pups can swim at birth and are able to dive for up to 2 minutes when they are only 2 to 3 days old. Pups rely on their mother’s milk for about 4 to 6 weeks. By the end of their first month, some young harbor seals may travel over 100 miles from their place of birth.

Harbor seals are largely considered non-migratory, staying within 15 to 31 miles of their place of birth. However, tracking data shows that they occasionally travel 62 to 486 miles in search of food or to give birth.

Following the mating and birthing season, harbor seals molt. They shed hair and whiskers in the mid-to-late summer for 1 to 2 months. During this time they spend more time out of the water.

In nature, harbor seals often live into their late twenties, with females living longer than males. Under human care, they can far surpass the lifespan of their wild counterparts.