Harbor seals are commonly seen on the rocks and in the water off Piedras Blancas. Harbor seals are quiet and shy compared to their noisy relative, the California sea lion. Harbor seals are easily disrupted by human activity so be aware of the impact your presence is having on them. If they are looking at you it probably means you are disturbing them. If they enter the water you have definitely disturbed them.
Color: Harbor seals have spotted coats that blend in well with the rocks and sandy beaches they haul out on. At times you have to look carefully to see them because they blend in so well with the rocks. There are two basic color variations. Some have dark coats with light spots and some have light coats with dark spots. Their fur turns brown just before molting. They do not go through a “catastrophic molt” as the elephant seals do, rather, each individual takes 6-8 weeks to molt. During the summer and early fall look for harbor seals in the process of shedding the old, brownish coat in favor of a bright spotted coat. Usually the yearlings molt first, followed by the subadults, then the adult females, and lastly the adult males.
Harbor seal pups have a white (lanugo) coat that they usually shed prior to birth. Most pups are born with their adult coloration, although occasionally pups are born with a white lanugo coat that is quickly shed and replaced with adult fur. The adult coat provides better insulation in cold water.
Shape: Harbor seals are round and torpedo-shaped. They have large eyes, a short cat-like snout, short flippers with claws, and no external ears. They are listed taxonomically in the family Phocidae, the true seals or earless seals, as are elephant seals.
Weight and length: Mature harbor seals weigh between 250-350 pounds. Pups weigh between 15-25 pounds at birth and about 50 pounds when weaned. Males average 6 feet in length, females are slightly smaller. Pups are about 24 inches long at birth. A full grown harbor seal is about the size of a weaned elephant seal pup.
Feeding: Harbor seals are opportunistic feeders, eating a variety of fish and other prey including squid, octopus and crustaceans. Along the central coast of California they relish the spotted cusk eel, a nocturnal fish. They tend to feed more at night and swallow most food items whole. They may eat an average of 5-10% of their weight every day.
Breathing and diving: They can dive up to 600 feet or more and hold their breath for 20 minutes or longer.Most dives are about 5-8 minutes and are in shallow water. Harbor seals have closable nostrils that keep out the water while diving.
Movement/behavior: Harbor seals have a torpedo shaped body, perfect for moving efficiently through the water. When swimming they use a side-to-side movement of their rear flippers to propel themselves, steering with the front flippers. On land they inch along on their stomachs using their front flippers to pull themselves along.
Harbor seals spend about half their time resting on land but they also sleep in the water. They can be seen resting just below the surface, rising occasionally to take a breath. They can also rest with just their heads above water, noses pointed up, in a position called “bottling.” On rocks they sometimes assume a crescent-shaped, or “banana,” position with head and rear flippers raised.
They are usually shy of people on land and will dive into the water if disturbed, but they can be very inquisitive of people in the water. Many divers have stories about harbor seals approaching them underwater.
Harbor seals are solitary while foraging but come together in groups when they haul out. They don’t like to touch each other and there is usually some space between individuals. However, during the molting season they rest more closely together. That is also the time the greatest numbers can be seen hauling out. Basking in the sun helps warm the body, promote blood flow to the skin, and conserves energy.
Sounds: Harbor seals are the least vocal of the pinnipeds, but sometimes they make grunting, growling and belching sounds on land - thought to possibly warn neighboring seals to keep at least a flipper’s distance away. Pups make a sheep-like “baa-ing” call to attract their mother’s attention. It sounds like “maa-maa.” The mother may respond with a call.
Reproduction: Male harbor seals are sexually mature by 4-5 years of age and females around 3-4 years of age. Along the central coast of California most pups are born on land, or occasionally in water near land. In the Piedras Blancas area most births usually occur during March and April. Females nurse their pups for 4-6 weeks then wean them to find males and mate. During the pupping season males are usually found in separate areas from the mothers and pups. Males don’t interfere with nursing mothers. In the Piedras Blancas area the peak of harbor seal mating activity is in May.
Courtship and mating take place in the water. Both males and females may mate with more than one partner. Males attract females by slapping the surface of the water with a fore or hind-flipper. On land the males make vocalizations, growls or coughs, and thrust the head forward to warn off other males. They don’t form harems or fight over territory. Most sexually mature females bear a pup every year.
Gestation is 10-11 months, including a 1-3 month delay in the implantation of the fertilized egg. Impregnated females molt during the period of delayed implantation. Females can give birth to one pup every year.
Pups: Bonding between the mother and pup usually occurs within 1 hour of birth and includes visual, auditory, and odor clues.Harbor seal pups can swim immediately after birth, but when they are young they often ride on their mother’s back. Within two days they can make short dives. Pups nurse for around 4 weeks on milk that is about 40% fat. Toward the end of the nursing period pups start catching their own food.
Longevity: In the wild, harbor seals may live 20-30 years.
Distribution: Harbor seals do not migrate great distances, but they move about in response to prey distribution. They are widely distributed throughout the Northern Hemisphere in bays, estuaries and along rocky shores. They haul out on beaches, mud flats, sand bars, gravel bars, rocks, icebergs and sea ice. In the North Atlantic they are known as the “common seal.”
Predators: Sharks, orcas (killer whales), and man prey on harbor seals. In some regions eagles, bears, and coyotes prey upon pups. Harbor seals are very wary of domestic dogs because members of dog family are natural predators.
Status: Worldwide their population is estimated to be around 500,000. In the Eastern Pacific the population is about 330,000 with about 40,000 along the California coast. They are protected under the Marine Mammal Protection Act in the United States but subsistence hunting is allowed in Alaska , Greenland , Northern Canada , and the USSR . They are subject to diseases, parasite infestation, and the accumulation of pollutants and contaminants.
Off Piedras Blancas: At low tide harbor seals may frequently be seen hauled out on near shore rocks. Sometimes they haul out on the beaches.
Caution! Mothers leave their pups on land while they forage. Unfortunately, people sometimes react to a solitary pup on the beach by getting too close or even taking the pup believing it to be abandoned. It is important that people leave pups alone or the mother might not return and the pup will be needlessly orphaned. Harbor seals have been known to abandon pups and favorite haul-out sites if they are disturbed too often by people.