California Sea Lion

The California sea lion (Zalophus californianus) is a member of the "eared seal" family, Otariidae. They are the most recognized pinniped species, commonly seen doing acrobatic tricks in shows at zoos and aquariums, as well as appearances in film and television.

Description[edit]

California sea lions are sexually "dimorphic" with males reaching average lengths of 7.5 ft (2.25 m) and weighing about 700 lbs (315 kg). Some large males exceed 1,000 lbs (455 kg). Females are much smaller, reaching average lengths of 6 ft (2 m) and weighing about 240 lbs (110 kg). They have a lifespan of 20 to 30 years. Their coats are dark brown with females being slightly lighter in color.

California sea lions are social animals and form groups of several hundred individuals onshore. They are fast, agile swimmers and are often seen porpoising and wave riding. Unlike true seals, they use their large front flippers as their means of propulsion in the water. The deepest dive ever recorded for a California sea lion is 1,760 ft (535 m); the longest dive was 12 minutes.

Males are "polygamous" establishing breeding territories that may include up to fourteen females. They defend their territories with aggressive physical displays and vocalization. Sea lions reach sexual maturity at 4–5 years old. Breeding season lasts from May to August while most pups are born from May through July. Three weeks after giving birth, females are ready to mate again. Pups are weaned at 10 months old.

California sea lions feed mainly in upwelling areas on a variety of prey such as squid anchovies, mackerel, rockfish, and sardines. They also take fish from commercial fishing gear, sport-fishing lines, and at fish passage facilities at dams and rivers.

Habitat and distribution[edit]

California sea lions reside in the Eastern North Pacific Ocean in shallow coastal and estuarine waters. Sandy beaches are preferred for haul out sites. In California, they haul out on marina docks as well as jetties and buoys.

California sea lions range from the Pacific coast of Central Mexico north to British Columbia, Canada. Their primary breeding range is from the Channel Islands in Southern California to Central Mexico.

The population is estimated to be 238,000 sea lions, and has been increasing since at least 1975, with an estimated annual growth rate from 1983 to 2003 of about 6.5%; however, the growth rate has decreased since the 1990s as the population approaches the carrying capacity of its environment.

Threats[edit]

The leading source of human-caused mortality is incidental catch and entanglement in fishing gear, such as gillnets. Estimated and reported levels of fishery-related mortality are so low that they likely have an insignificant impact on the population. California sea lions are sometimes viewed as a nuisance by commercial fishermen and there are records of stranded sea lions with gunshot wounds and other human-caused injuries.

Natural threats include great white sharks and orcas. Recently, mortalities have been linked to biotoxins as a result of harmful algal blooms. [1]