Also found in: Dictionary, Thesaurus, Medical.
Carnivorous mammals of the suborder Pinnipedia, which includes 32 species of seals, sea lions, and walrus in 3 families. All species of the order are found along coastal areas, from the Antarctic to the Arctic regions. Although many species have restricted distribution, the group as a whole has worldwide distribution.
Pinnipeds are less modified both anatomically and behaviorally for marine life than are other marine mammals: Each year they return to land to breed, and they have retained their hindlimbs. They are primarily carnivorous mammals, with fish supplying the basic diet. They also eat crustaceans, mollusks, and, in some instances, sea birds. Their body is covered with a heavy coat of fur, the limbs are modified as flippers, the eyes are large, the external ear is small or lacking, and the tail is absent or very short.
The single species of the family Odobenidae is the walrus (Odobenus rosmarus); it grows to 10 ft (3 m) and weighs 3000 lb (1350 kg). It has no external ears but does have a distinct neck region. The upper canines of both sexes are prolonged as tusks which can be used defensively (illus. a). The walrus feeds on marine invertebrates and fish.
The family Otariidae, the eared seals, includes the sea lions and fur seals (illus. b), which are characterized by an external ear. The neck is longer and more clearly defined than that of true seals, and the digits lack nails. The California sea lion (Zalophus californianus) occurs along the Pacific coast, and is commonly seen in zoos and performing in circuses. The southern sea lion (Otaria byronia) is found around the Galapagos Islands and along the South American coast. Stellar's sea lion (Eumetopias jubatus) is a large species found along the Pacific coast. Minor species are the Australian sea lion (Neophoca cinerea) and the New Zealand species (Phocarctos hookeri).
Phocidae is the largest family of pinnipeds, the true seals. It includes the monk seals, elephant seals, common seals, and other less well-known forms. The family is unique in that the digits have nails, the soles and palms are covered with hair, and the necks are very short. Most species live in marine habitats; however, the Caspian seal (Pusa caspica) lives in brackish water. The only fresh-water seal is the Baikal seal (P. sibirica). It is estimated that there are between 40,000 and 100,000 Baikal seals in Lake Baikal. One of the best-known species is the Atlantic gray seal (Halichoreus grypus), a species fround in the North Atlantic along the coasts of Europe, Iceland, and Greenland. See Carnivora, Mammalia