San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
Photo of California sea lion, Brad Hollingsworth, SDNHM

Zalophus californianus
California Sea Lion

OTARIIDAE (Eared Seals and Sea Lions)

Description

The California sea lion is probably the most commonly seen pinniped along our coast. It has distinct external ears, large eyes, and elongated front flippers. Its hind flippers can be turned forward under its body, allowing it to walk on land. In the water California sea lions swim with powerful strokes of the front flippers. The smaller hind flippers help in steering. The male's fur is usually dark brown, nearly black when wet, and the female's is often light brown or tan; there is no undercoat. The male has a thick neck, and the mature male has a protruding forehead formed by a bony crest on the skull roof. The California sea lion vocalizes with a continual honking bark that is familiar to most people who have seen animal acts in zoos or marine parks—this species is widely used in trained animal shows.

Size: California sea lions show an extreme degree of sexual dimorphism, with males much larger than females. A male sea lion may measure up to 2.4 meters (8 feet) and weigh 270 kg (600 lbs); a female may measure up to 1.8 meters (6 feet) and weigh 90 kg (200 lbs.)

Similar species: Steller's sea lion—larger and paler with a low forehead, seldom barks. Guadalupe Fur Seal—lower forehead and more pointed nose. Elephant seal—much larger, no external ears, usually quiet. Harbor seal—spotted.

Range and Habitat

As the common name suggests, this species occurs mainly in California's coastal waters, but is also found around the Galapagos Islands and Japan. This species ranges along the Pacific Coast, from British Columbia south to California and the coast of Mexico. Except in summer, the California sea lion, a temperate to subtropical species, overlaps its range with that of the Steller's sea lion, a subarctic to temperate species, which ranges from the Bering Sea south to the Channel Islands.

The breeding range of Zalophus extends from the Channel Islands off southern California south along the coast of Mexico, possibly to the Tres Marias Islands. A number of islands in the Sea of Cortez have breeding populations, but the major sites are San Miguel and San Nicolas islands in the Channel Island chain, along with several islands off the Pacific Coast of Baja California.

Towards the end of the breeding season, both adult and immature males start moving north from the west coast of Baja California and the Channel Island rookeries. This migration peaks in September along central and northern California.

Natural History

Behavior: Along the California coast, Zalophus can be seen on offshore rocks, quiet beaches, in bays, and sometimes on buoys. It's gregarious and curious, and will investigate swimmers and scuba divers. The sea lion is a proficient swimmer, using it large front flippers for propulsion and its hind flippers as rudders. It can swim up to 16 kmph (10mph) when after food.

Reproduction: : Females are ready to breed at three years, males at five. Only mature dominant males acquire females. The breeding season takes place between May and July. During the breeding season, dominant bulls gather harems of several cows, which they protect by barking at or moving aggressively towards intruding males. Occasionally, the bulls engage in combat. After a year-long gestation period, a single pup is born. The pups grow rapidly and will begin to gather in groups. They are weaned after several months, but may continue to nurse for up to a year.

Diet: California sea lions eat fish, mollusks, and crustaceans.

Predators: Orcas, great white sharks, and humans.

Conservation Status

Although the California sea lion is not considered an endangered species, it is included in the protection given in U.S. waters by the Marine Mammal Protection Act.


Text: Linda West in consulation with Dr. Thomas Deméré
Photographs: Bradford Hollingsworth

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