San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
Phoca vitulina, Harbor Seal, Photo by Don Senda

Phoca vitulina
Harbor Seal

Phocidae (Hair Seals, Earless Seals)

Description

The harbor seal is a relatively small member of the Phocidae family. The head is large, the body short, and the front limbs relatively small. Like other phocids, the ears are indicated by small openings in the skin; there are no pinnae (cartilaginous projecting portions of an external ear). The seal's large hind flippers cannot be turned forward under the body as in sea lions. Consequently, on land the harbor seal can't walk, but must rely on a wriggling style locomotion using its forelimbs to pull it along in quick caterpillar-like jerks. In the water, the harbor seal is a graceful swimmer. They propel themselves by lateral undulations of the hind flippers, which expand when swimming. The front flippers are used for an occasional guiding stroke.

The harbor seal's fur is stiff, with no undercoat in the adults. The color is quite variable: pale silver-gray with black to dark brown spots, brown with gray spots, uniform silver-gray, or brownish black with spots that are barely visible.

Size: Harbor seals lack the extreme sexual dimorphism common to many species of pinnipeds. The males tend to be only slightly larger than females with average body lengths of 1.7 and 1.5 meters (6 and 5 feet), respectively. Average male and female body weights are 94 and 78 kg (209 and 172 pounds), respectively.

Similar species: Sea lions and fur seals—these have no spots, but do have external ears and can rotate hind flippers forward. Elephant seal—this species is larger and has no spots. Ringed seal— has spots, but is also streaked along the back.

Range and Habitat

Range: Harbor seals inhabit temperate and subarctic waters of the North Atlantic and North Pacific oceans. In the North Pacific Ocean, harbor seals can be found from Alaska south along the coast of North America to Cedros Island off the west coast of Baja California and along the Asiatic coast to China. In the North Atlantic they are present from Greenland south to North Carolina and from Iceland south to the shores of the Netherlands and occasionally France.

Habitat: Harbor seals are littoral in distribution and can often be seen on protected tidal rocks and reefs.Harbor Seals in La Jolla, photo by Don Senda

Natural History

Behavior: Although common along the California coast, harbor seals are rarely found in large numbers. Groups may range from a few individuals to as many as two or three hundred, but they do not exhibit the sort of social behavior characteristic of sea lions, fur seals, and elephant seals. Harbor seals often come into bays and estuaries and may be seen resting on sandbars at low tide. Along the outer coast they also tend to haul out on protected tidal rocks and reefs (as at the Children's Pool in La Jolla). Because their movements on lands are clumsy, they seldom venture far from the water, where they take refuge at the first sign of danger. They can remain underwater for as long as 20 minutes. Unlike other pinnipeds, harbor seals make little noise. Occasionally, they will slap the surface of the water with their flippers, producing a loud noise that can be heard for some distance. They are considered non-migratory.

Reproduction: Harbor seals, unlike many other seal species, do not form harems but mate promiscuously. Sexual maturity occurs in females when three or four years old and in males at five years. Mating usually takes place in September, and after a gestation period of slightly more than nine months, a single pup is born. Although the pups are born with a dark coat, a white prenatal pelage (hairy coat) is shed in the uterus, just before birth. The young are usually born on a reef or sandbar and are able to swim almost immediately. Weaning occurs within four to six weeks.

Diet: The harbor seals feed on fish, molluscs, squid, and octopus found along the shore and in bays and estuaries

Conservation Status

Harbor seals are protected in U.S. coastal waters by the Marine Mammal Protection Act. The eastern North Pacific (Alaska to California) population is estimated at around 300,000 individuals.

Explore More

La Jolla Friends of the Seals—This website has general information about the harbor seals inhabiting Casa Beach in La Jolla, and guidelines for observing the seals. During summer 2000, the installation of a SealCam will provides 24-hour viewing of the La Jolla Harbor seals.


Text: Linda West in consulation with Dr. Thomas Deméré
Photo credits: Don Senda, SDNHM

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