Pinnipeds are organized into groups of animals that share similar physical, functional, and genetic characteristics. All pinnipeds belong to the Order Carnivora, which includes meat-eating animals with sharp teeth. The next classification is the Suborder Pinnipedia. The name pinniped comes from the Latin "pinnipes" and roughly translates to “wing or fin-footed.” These animals have paddle-shaped feet with claws. The suborder Pinnipedia is divided into three families: the Otariidae, the Phocidae and the Odobenidae, which are further divided into genus and species.
The Otariidaeare are characterized by having external ear flaps (pinnae) and are often referred to as the "eared seals". They have smooth whiskers (vibrissae), they can walk on all four limbs (quadrupedal), and they have nails on the rear flippers and small tails. The bottom surfaces (palmar surface) of the flippers are leathery rather than covered with fur. The Otariids swim primarily with their front flippers, using the rear flippers for steering. Adult males are much larger than females (sexual dimorphism) and develop a sagittal crest on the skull.
Of all the pinnipeds, only 10% are in the family Otariidae, yet, in Southern California, they constitute the majority of our patients. The California Sea Lion (Zalophus californianus) is the most commonly seen pinniped at the Marine Mammal Care Center at Fort MacArthur. Other members of the Otariid family seen at MMCC include the Northern Fur Seal (Callorhin usursinus) and the Guadalupe Fur Seal (Arctocephalus townsendi).
Don’t let the common names Northern Fur Seal and Guadalupe Fur Seal confuse you. These animals have all the characteristics of the sea lion family despite having the common name of fur seal. These animals eat fish and squid, travel long distances and can live 15-25 years. They breed and have their pups on islands or remote coastal rookeries. The California Sea Lion pups may stay with their moms on their natal beaches for a year or more. We often admit young sea lion pups at 6-12 months of age, if they separate early from their mothers.
The Phocidae account for 90% of all pinnipeds worldwide. They are often referred to as "true seals" and are characterized by having no external ear flaps, having fur on all flipper surfaces, and small, sharp nails on the front and rear digits. They cannot tuck their rear flippers under their bodies for walking as the sea lions do. They move on land by scooting and in the water the rear flippers move side to side, pushing the animal through the water.
The Phocidae are distributed around the world and in many habitats. The smallest pinniped, weighing up to 200 lbs, is the Baikal Seal (Pusa sibirica), which is found in Lake Baikal, Russia. This is the only freshwater seal. The largest pinniped is the Southern Elephant Seal (Mirounga leonina), which is found in Antarctica and weighs up to 11,000 lbs. Worldwide there are 13 genera and 18 species in the family Phocidae. Many are associated with the Arctic and Antarctic.
Coastal California is home to two phocid species; the Pacific Harbor Seal (Phoca vitulina) and the Northern Elephant Seal (Mirounga angustirostris) and both are routinely admitted to MMCC for injury, illness or malnutrition. Adult northern elephant seals are rarely observed on Southern California beaches and are rarely admitted for rehabilitation. Adult harbor seals are also rarely admitted for rehabilitation. Unlike sea lions, the Northern Elephant Seal and the Pacific Harbor Seal have short lactation periods of only about 30 days before the pups are weaned.
The Odobenidae, include the walruses. Walruses are found in coastal areas of Alaska and around the Arctic. They breed on pack ice and forage on mollusks, clams and other invertebrates on the bottom of the ocean. They are characterized by the continually growing upper canine teeth in adult males and females and can reach 40 years of age.