Otariidae Family of Eared Seals, Fur Seals and Sea Lions

One Sea Lion of the Otariidae Family can be found in this website:

California Sea Lion, Zalophus californianus. A representative of the Otariidae Family of Eared Seals, Fur Seals and Sea Lions.

Phylogeny: Eared Seals, Fur Seals and Sea Lions of the Otariidae Family are marine mammals. Like all mammals, they are in the phylum Chordata, the subphylum Vertebrata, the infraphylum Gnathostomata, the megaclass Tetrapoda, and the class Mammalia. They are in the subclass Theria of viviparous (live-bearing) mammals.  They are in the order Carnivora and are thought to be descendants of modern Bears. They are in the suborder Caniforma and the infraorder Pinnipedia.  Pinnipeds include Walrus, True Seals and Eared Seals. The Otariidae Family is one of three families in this infraorder. The Otariidae Family contains seven genera and fourteen species. The name Otariidae comes from the Greek word meaning “little ears”. This refers to their external ear flaps. This is also the source of the common generic name used for these species of Eared Seals.

Morphology: Pinnipeds are large mammals, adapted to an aquatic life. The name Pinniped comes from the Latin for fin-footed, feather-footed, or wing-footed because the fore and hind limbs are shaped like fins or paddles. Their limb bones are long and enclosed within the spindle-shaped body. The torso skeletal structure allows for efficient swimming and for land locomotion. They generally have relatively large eyes for improved vision in low light conditions, and whiskers for tactile sensation. All have a short tail. They have a blubber layer, and varying amounts of hair for warmth. Eared Seals differ from True Seals in that they have external ear flaps (pinnae). They have long fore-flippers that are leathery, lack hair, and are tipped with small claws that are utilized for swimming. The hind-flippers are used as a rudder for steering; they can also be rotated under the body, allowing the animal to lift its weight on land. Unlike True Seals, Eared Seals can walk, run, and climb on all fours. When resting on the surface of the water, Eared Seals often lift their flippers out of the water. Fur Seals differ from Sea Lions in that they have a dense undercoat which provides additional warmth. The sexes are dimorphic with males being 2.4 to 4.5 times larger than females. Adults in this family range in weight from 70 kg (150 Lbs.) Galapagos Fur Seals to 1,000 kg (2,200 Lbs.) Stellar Sea Lions.

Habitat and Distribution: Eared Seals may be found in open water well-offshore, nearshore, in the surf zone, or in bays. They may also be found on exposed rocky coastlines and sandy beaches. They are generally found in shallow water, but some species can dive deeper than 500 m (1,640 feet). While they are accomplished swimmers that feed and migrate in water, they must come to shore to rest, mate and nurse. Therefore, they are usually found near islands or coastal land. While Eared Seals are often encountered swimming alone, they are highly social animals that will form large herds during breeding season. Eared Seals have a worldwide, but discontinuous distribution. They are found globally in tropical to temperate seas, but are absent from the North Atlantic Ocean. Two species from this family are found along the Pacific Coast of Mexico. The California Sea Lion is also considered an Accidental or Vagrant species in the Gulf of Mexico, most likely as the result of human introduction.

Reproduction: As mammals, Eared Seals are gonochoric (male or female for life) and reproduce sexually with internal fertilization. The males are polygynous, mating with several females. Male establish territories and harems, which they defend aggressively. Females can delay implantation (embryonic diapause) of the fertilized egg until conditions are right. Females give birth to one pup per year, with 11 to 12 month gestation periods. Depending on the species, mothers nurse their pups for 4 to 30 months.

Ecosystem Roles: Eared Seals are predatory carnivores that consume cephalopods, crustaceans, fish, and penguins. They are prey for sharks and Killer Whales.