Times better hearing underwater
Length an adult can hold breath underwater
Eaten by adult seals per day
Harbour seals are found along the coast of the temperate Northern Hemisphere, often in coastal waters, estuaries and river systems. There are several subspecies, such as the Pacific harbour seal, Phoca vitulina richardsi, which inhabit the B.C. coast. The adult Pacific harbour seal may reach a length of 1.6 - 1.9 m and weigh from 60 - 120 kg, while ranging in colour from brownish to black with a speckled pattern.
Preliminary studies analyzing harbour seal scat (feces) for bones and hard parts, indicate that the majority of their diet consists of small reef or shallow dwelling fishes including rockfishes, greenlings, smelt, perch, and some herring and flatfishes. In the Strait of Georgia, a large component of their diet is hake, a deep-water fish. Seasonally, harbour seals eat salmonids as these fishes enter and leave the rivers. Adult seals typically eat 3-5 kg of food per day.
Mating generally occurs in late spring or summer, shortly after the previous year’s pup has been weaned. Each male harbour seal will mate with several females during the breeding season. Competition for mates and copulation usually occur in the water. In B.C., the seal pup is born on tidal reefs or on beaches between late June and September, peaking in July and August.
Between 1913 and 1970, the combination of a bounty implemented by Fisheries and Oceans Canada and extensive hunting of the harbour seal for its pelt lowered seal populations dramatically. Pacific harbour seal populations have recovered and are approaching historical records in B.C., with more than 127,000 individuals counted during a 1998 aerial survey. Harbour seals are the most common of all the temperate-water seals.
The harbour seal’s main predator is the killer whale, but they must also be on the lookout for some shark species and humans. They are protected against commercial exploitation, but is still hunted by some native populations and may be shot by fishermen. New threats to harbour seal populations are pollution and the reduction of their food stocks. Some seals die when they become entangled in fishermen’s nets, while parasites and disease are also an increasing threat to a growing population.
Following birth, the pup is nursed and protected by its mother for four to six weeks. Nursing time corresponds to the ocean tide cycles, and may occur at low tide. A harbour seal pup can swim and dive shortly after birth but requires practice to increase its skill and endurance. The pup grows rapidly during its first month of life, gaining extra fat to help it survive while developing its hunting skills.
Hearing and sight are highly developed in harbour seals. Large eyes, protected by oily “tears,” help the seal see in deep, dark waters. A harbour seal’s hearing is almost 14 times greater under water (160 kHz) than above the surface (12 kHz). Some scientists suspect that harbour seals may have the ability to echolocate. Whiskers can be extended forward to “feel” or inspect unfamiliar shapes and surfaces and are extremely important in low light situations. Blind harbour seals have been known to thrive in the wild. A harbour seal uses its sense of smell to locate a lost pup.
When the seal’s face is submerged, it automatically holds its breath, its heartbeat slows by up to 90% and its blood circulation is reduced, except to the most vital organs, the heart and brain. This allows seals to stay under water for long periods.
1. Grace, Eric S. and Fred Bruemmer. 1991. Seals. Toronto: Key Porter Books.
2. King, Judith E. 1983. Seals of the World. 2nd Ed. New York: Comstock Publishing.
3. Gordon, David George. 1994. Seals and Sea Lions. Monterey Bay, Ca.: Monterey Bay Aquarium.
4. Reeves, Randall R., Brent S. Stewart and Stephen Leatherwood. 1992. The Sierra Club Handbook of Seals and Sirenians. San Francisco: Sierra Club Books.
5. Harbour seal. 2007. MarineBio.
6. Harbour seal. 2001. Marine Mammal Centre.
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