Harbor Seal

The Common Seal

The Harbor Seal is a small seal, but the rounded, short-muzzled head and spotted coat are quite distinctive. The eyes are very large and the front flippers short. The nostrils form a wide “V” and the ear openings are inconspicuous, with no external pinnae ‘ears’ as seen on Otariids. There is no obvious sexual dimorphism.


Phocids like cold coastal waters. In the northern hemisphere Atlantic they range south to Cape Cod and France, and in the northern Pacific, to Baja California and Japan. Marine Harbor Seals are often seen great distances up coastal rivers. They prefer shallow water and sandy beaches. They only utilize areas of the Arctic that are free of ice in the winter. There is a fresh-water subspecies in Lower Seal Lake and some other lakes on the Canadian Ungava Peninsula, 150 km east of Hudson Bay, at an elevation of 250 meters (@ 750 feet) above sea level.


  • Wild – Various coastal fishes, cephalopods and crustaceans.
  • Zoo – Mackerel, sardines, squid or other fish, supplemented with vitamins and sea salt.


Light gray to gray-brown, Harbor Seals have rings or spots that may be light on dark or dark on light. Newborn Phocids generally have a white to yellow woolly coat, which is molted over their first few weeks. Harbor Seal pups, however, may molt their white woolly fur in utero or at birth, although the NW Pacific subspecies that births on drifting ice retains the woolly coat longer. The adult coat is stiff and short with no undercoat.


Seasonally monogamous, Harbor Seals are seldom seen in large groups. Spending most of their time in the water, all that is usually ever seen is their heads bobbing in the swells just outside the breaking waves in a behavior called ‘spy-hopping.’ Along California they like the kelp forests. Limited haul-out sites or an aggregation of food species may be the only reasons for group formation. If they do haul out together, they do not touch each other. They are very wary when on-shore. Little is known about their non-breeding socialization or other behaviors. Solitary species of pinnipeds, like Harbor Seals, are generally not very vocal. Harem-forming species, like Elephant Seals (Mirounga species) and Sea Lions, are exceedingly vocal.

Juvenile seals cannot swim well and must learn by emulation and practice. They will often frolic in tide pools and vernal rain pools, gaining skill. Both pups and adults may be seen, on haul-out sites, in the “banana” position, with both head and tail ends raised. This apparently aids in keeping cool.


When True Seals swim, they power with the hind limbs and their lumbar spine is unbelievably flexible. They steer with the short front flippers. Because their front flippers cannot reach the ground, True Seals motivate on land with the classic “inch-worm” action of stomach hunching called undulation. Despite the clumsy appearance, these seals are quite fast for short distances. The fore flippers are well furred and there are claws on the toes, which are used in grooming.

Blubber is a specialized fat-layer just under the skin. It serves as padding and insulation against the cold, as well as for buoyancy and a fat reserve against starvation. There is a rete mirabile, a “miracle net” of capillaries and larger blood vessels, in each flipper. Body-core heat is conserved when warm out-flowing arteriole blood passes through a capillary bed that wraps around the in-coming veins. The arteriole blood is cooled as it warms the chilled in-coming venous blood. The flippers are maintained at water temperature and very little body heat is lost. Blubber is, of course, a detriment on-shore and pinnipeds must regularly go into the sea to cool off.

True seals can go straight from lounging on the beach to a dive over a ¼ mile deep. They can stay down for over an hour. As with all marine-mammal divers, true seals have certain physiological adaptations. In a dive, the heart and metabolic rates are slowed, the body temperature drops and the lungs collapse, expelling almost all air. They have myoglobin, giving them the ability to store large amounts of oxygen in the muscle tissues, and they have an extreme tolerance for high carbon dioxide levels in the tissues. The large eyes are designed to change focus, adjusting to the different refractive indices of air and water.

Breeding & Growth

Fairly sedentary, these mostly solitary seals do no form harems. They do begin to gather in small, mixed groups in late summer. The loose groups show no hierarchy. Mature seals (about 5 years old) pair up and, in September, swim off to secluded areas where they generally breed in the water. “Monogamous” is sometimes applied to them, but it is miss-leading. The females mate with one male and are done with the breeding season, heading back to sea soon afterwards. The marginally larger males are opportunistically promiscuous but defend no territory or harem group. Harbor Seals winter at sea, the females coming in-shore again to give birth in spring. Delayed implantation can make the apparent gestation 11 months, but one pup (occasionally 2) is born after a 220-day gestation. Pups often enter the water within hours of birth. They are weaned at about 6 weeks, will disperse after following the mother for a time. Longevity is about 35 years for females, 25 years for males and longer with captive animals.

California Sea Lion

Adapted for Movement on Land and Water

Sea Lions show extreme sexual dimorphism. The lighter, longer hair of the crest and upper neck give males a maned appearance, hence sea LION. “Eared Seal” ears are small and cone-like around the ear openings. True seals have no pinnae. Eared Seals have long vibrissae and heavier muzzles than seals, and they are quadrupedal.

Appearing black when they are wet, Sea Lions are brown. During the molt, they are blotchy as the sun-bleached old hair is replaced by the true-color new pelage. The woolly pups are coffee-brown to black at birth, becoming their adult color with the 6-month molt.


California Sea Lions are found from the tip of Baja to the Alaskan Gulf, primarily along coastlines with sandy or rocky beaches. They predominantly forage the Continental Shelf.


  • Wild – Varied sea life, preferring fish, squid and octopus, but also take crustaceans and urchins.
  • Zoo – Squid and fish (during any time in freshwater, salt pellets/vitamins inserted in the fish).


Sea Lions are rarely more than 20 miles out to sea, concentrating activities in areas of cool-water upwelling, where food is the most plentiful. Their populations are greatly affected by the warming seen in severe El Niño years. They seem, however, to recover within 4 – 5 years.

They feed on whatever is abundant, and seldom deep-dive. Enemies include sharks, orcas and humans. Sea Lions haul out to rest and to sleep at night, and breakwaters are a favorite. They fold back the cartilaginous extensions on their hind flippers to use the strong claws on the three middle toes for scratching. The front claws are vestigial. Vocalizations are sharp barks, throaty chortles and honks.


The breeding strategy of pinnipeds like Sea Lions favors larger-sized males. Large males are better able to defend territories, they need less energy per unit of body weight and can survive long periods of fasting, a necessity since they cannot leave their territories to feed. Larger bulls are more successful, producing more offspring with the DNA for larger size. Sea Lions have no value as fur-bearers, their fur is very short. They are highly adapted to an aquatic life, their modified limbs mostly enclosed within the body. The hands and feet are long, flattened and fully webbed. They move surprisingly fast on land, traveling more easily than true seals because they can stand on sideways-turned hands and feet, actually walking. The structure of the shoulder and arm allows an easy figure-eight for powering the swimming. Steering is accomplished with the hind limbs. Swimming with ultimate grace, Sea Lions are agile, rapid swimmers, catching fast-moving prey.

Thick blubber beneath the skin smoothes the shape to the classic no-drag torpedo, provides buoyancy and insulates against cold. All diving pinnipeds show many physiological adaptations that conserve oxygen, including: slowed heart rate, slowed metabolism, dropped body temperature, high tolerance to carbon dioxide in the tissues, myoglobin (able to store large amounts of oxygen in muscle tissues) and collapsing the lungs before the dive. Expelling air from the lungs effectively limits gas-exchange in the lungs, avoiding the condition known as the bends (nitrogen bubbles in the blood) on ascent.

The nostrils are slits that are tightly closed and are forced open by special muscles. Incisors and canines are carnivore-like but premolars and molars are peg-like and interdigitated for grabbing and holding. Prey is swallowed whole. The hairless soles of the flippers are well-supplied with blood vessels and sweat glands. The flippers are waved when the animal is hot. Pinnipeds have large eyes and the shape of the lens adjusts for differences in light refraction in air and water. Very long vibrissae (whiskers) may help detect vibrations under water. They are quite stiff and definitely help balance the ball during circus tricks. Hearing is acute. California Sea Lions produce sounds both in and out of water and are known as one of the noisiest Otariids.

Breeding & Growth

Otariids are polygynous (“many females”) and bulls maintain a “harem” of 5 to 20 cows for the breeding season. A dominant bull uses the same rookery year after year but each year a new “harem” is established. Bulls arrive first to establish their territories. Cows regularly gather in groups. Dominant bulls defend access to a group of females, the cow chooses the group and the stretch of beach within which she wants to have her calf. A bull cannot actively pursue a cow without leaving his territory. He does his best to keep the cows in his territory from leaving.

Cows come ashore 2 to 3 weeks after the bulls, about 2 days before their pups arrive. As each pup is born, the cow will vocalize and sniff at the pup, which responds vocally. This immediate vocal and olfactory recognition is very important for maintaining the mother/pup bond. The suckling pup gets very rich milk (36% fat, 14% protein) and grows rapidly. Cows come into heat about 8 days after calving and leave for the sea to feed soon after breeding. When a cow leaves, her pup moves to the back of the breeding beach, with the other pups. This keeps them out of the way of still-ardent bulls.

Pups are often trampled in territorial and breeding scrambles. Bulls are unconcerned because the pups, conceived last breeding season, are probably not his. The mother returns weekly for 4 months, goes to the crèche of pups and calls. Answered with the birth-call, Mother confirms recognition with a sniff and leads the pup to a secluded place so it can nurse. The pups swim in tide pools at first and later go into the sea with their mothers. Cows begin to breed at 3 years of age, the bulls at 5 years or more. A fully crested Beach Master is closer to 10. Life expectancy is 12 to 15 years wild, and 30 in captivity.