Pinnipeds: Seals and Sea Lions

December 1997 - January 1998

This is an article from WaveLength Magazine, available in print in North America and globally on the web.

Seals, Sea lions and Walruses are currently placed in a Sub-order, the Pinnipedia, of the Order Carnivora which also includes the bears, dogs, racoons, weasles (including otters), hyenas, cats, and mongooses. There have been many recent studies on the genetic and fossil history of these groups and their place in the scheme of mammalian classification may well change in the near future.

Three families of living pinnipeds are recognized, the Phocidae (hair seals or true seals), the Otaridae (fur seals and sea lions) and the Odobenidae (walrus). The term pinnipedia translates from Latin as "fin foot". All of these animals must come ashore to breed, give birth and nurse their young, though some species are at sea for several months at a time while others return to the shore every day.

Phocid seals include elephant seals, several species of ice seals (some are found in fresh water lakes) and the harbor seal of temperate coastlines. The monk seals are found in the Mediterranean Sea and Hawaii. Four phocid species inhabit the Antarctic ice pack. All of these seals have a vertical undulating motion when they move on land. The pelvic architecture does not provide a stable anchor point for the rear flippers to engage the ground for propulsion and the rear flippers are directed rearward.

The Otarids, fur seals and sea lions are found in temperate colder waters and are associated in tropical latitudes with cold water upwelling currents. They have external ear flaps. The arm pit or axilla encloses the forelimbs to about the level of the forearm. In all the pinnipeds the hind limbs (eg. rear legs) are enclosed to the level of the ankle. Sea lions and fur seals can rotate their hind feet forward and therefore use the pelvic architecture in propelling themselves forward with considerable speed.

The walruses, Odobenidae, are found in recent times in Arctic ice pack areas, both Pacific and Atlantic, but in colonial times were found as far south as Sable Island off Nova Scotia. They are very similar to the Otarids in locomotion.

There are currently four species of pinnipeds in the U.S. on the endangered species list. These include the Caribbean monk seal, the Guadalupe fur seal, the Hawaiian monk seal and the Steller sea lion. The Caribbean monk seal and the Hawaiian mink seal are listed as endangered, while the Guadalupe fur seal and Steller sea lion are currently listed as threatened.

Commercial hunting of seals in the 18th and 19th century, and in the early years of this century played a large role in pinniped population declines. Other factors involved have been coastal development and competition with man for prey species.

Steller sea lions

COLOUR: light to reddish brown; pups are silvery black turning lighter after several moults (approx. two years); skin is black.

SIZE: Males: average 9 feet long and weigh up to 2000 lbs.
Females: average 7 feet long and weigh approximately 600 lbs.
Pups: born approximately 3 feet long.

DISTINGUISHING FEATURES: external ear flaps; shape of head and shoulders is similar to a bear; males have a mane of thick, longer hair around their necks; can gallop surprisingly quickly on land.

VOCALISATIONS: deep throated growls and grunts.

BREEDING AND LIFE CYCLE: A dominant bull is polygamous. Mating occurs between May and July. After a one-year gestation period 1 pup is born around late June. Two weeks later the female will mate again with the territorial male. After birth the pups will learn to swim in tide pools then join their mother for short trips to sea at about one month old. Pups nurse for approximately one year. Females gain sexual maturity in 3-6 years, males between 4-7 years. When males reach maturity they can challenge the dominant bull for territorial rights. Can live up to 25 years.

FEEDING: primarily on schooling fish and mollusks; feed at night and haul out to rest and nurse during the day.

REACTION TO KAYAKS: Steller sea lions are not known to "attack" people.

California Sea Lions

COLOUR: dark chestnut brown; females may be lighter in colour; pups are black.

SIZE: Males: approx. 7 feet long and weigh 600-1000 lbs.
Females: approx. 6 feet and weigh 200-350 lbs.
Pups: born 12-14lbs.

DISTINGUISHING FEATURES: males sometimes have a bump or crest on their head and lighter hair on their muzzle. They may also have a mane but it is much less developed than the steller sea lion; external ear flaps; can rotate front flippers for increased agility on land; very flexible; can dive more than 300 feet.

VOCALISATIONS: a honking bark.

BREEDING AND LIFE CYCLE: Males are polygamous and mate with females in the spring. Gestation lasts approximately one year after which a single pup is born in May or June. Females will mate again approximately 10 days after giving birth. The pup may be weaned from 5 months to a year. Adults live to approx. 18 years.

FEEDING: not well known. Believed to be opportunist feeders, eating what is available during the day or night.

REACTION TO KAYAKS (people): have been known to bite if provoked.

NOTE: sealions performing in circuses or aquatic shows are usually the California Sea Lions.