The California sea lion (Zalophus californianus) is one of six species of sea lions. They mainly haul-out on sandy or rocky beaches, but they also frequent manmade environments such as marinas and wharves. California sea lions are particularly intelligent, can be trained to perform various tasks, and display limited fear of humans if accustomed to them. Because of this, California sea lions are a popular choice for public display in zoos, circuses, and oceanariums, and are trained by the United States Navy for certain military operations.
Females and juveniles of this species have a tawny brown pelage, although they may be temporarily light gray or silver after molting. The pelage of adult males can be anywhere from light brown to black but is typically dark brown. The face of adult males may also be light tan in some areas. Pups have a black or dark brown pelage at birth. Although the species has a slender build, adult males have robust necks, chests, and shoulders. Adult males also have a protruding crest which gives them a "high, domed forehead"; it is tufted with white hairs. They also have manes, which are less developed than those of adult male South American and Steller sea lions. Both sexes have long, narrow muzzles. The California sea lion relies on its foreflippers to propel itself when swimming. This form of aquatic locomotion, along with its streamlined body, effectively reduces drag underwater. Its foreflipper movement is not continuous; the animal glides in between each stroke. The flexibility of its spine allows the California sea lion to bend its neck backward far enough to reach its hindflippers. This allows the animal to make dorsal turns and maintain a streamlined posture. When moving on land, the California sea lion is able to turn its hindflippers forward and walk on all fours. It moves the foreflippers in a transverse, rather than a sagittal, fashion. In addition, it relies on movements of its head and neck more than its hindflippers for terrestrial locomotion.
California sea lions inhabit British Columbia in Canada and south to Baja, Mexico, including in the Gulf of California. Breeding mainly on offshore islands that run from the Channel Islands in southern California to Mexico, these sea lions typically live along coastlines but also occur in rivers along the coast of the northern Pacific. They often gather on man-made structures like jetties, piers, oil platforms, and offshore buoys.
Being very social animals, California sea lions form groups onshore of several hundred individuals. They typically haul out on rocky islets, buoys, and unused floating piers. Once hauled out, almost constantly they will make a barking sound distinctive to this species. In water, they float together in “rafts” on the ocean’s surface. They are able to travel some distance in search of their favorite foods, but they feed mostly in areas of upwelling. California sea lions mostly forage near mainland coastlines, the continental shelf, and seamounts. They may also search along the ocean bottom. California sea lions may eat alone or in small to large groups, depending on the amount of food available. They sometimes cooperate with other predators, such as dolphins, porpoises, and seabirds, when hunting large schools of fish. California sea lions sometimes follow dolphins and exploit their hunting efforts. Adult females feed between 10-100 km (6.2-62.1 mi) from shore. Adult males may forage as far as 450 km (280 mi) from shore when water temperatures rise. California sea lions are very fast, agile swimmers and can often be seen wave riding and porpoising. Sometimes they are seen several miles offshore. California sea lions can dive at depths of 274 m (899 ft) and for up to 9.9 minutes, though most dives are typically 80 m (260 ft) and last less than 3 minutes.
California sea lions are carnivores (piscivores and molluscivores), they eat a large range of different fish species (some commercial species included), such as Pacific whiting, northern anchovies, and mackerel, and they also eat some cephalopod species.
This species is polygynous, with a male establishing a breeding territory that may contain up to fourteen females. He defends his territory with vocalization and aggressive physical displays. The breeding season is from May to August, with most pups born between May and July. After a gestation of 11 months, a female gives birth to a single baby. Three weeks later, she is ready to mate again. The female spends the first-week post birth with her pup and then begins alternating feeding trips out to sea (of 2 to 3 days) and suckling bouts on land (of 1 to 2 days), for 10 to 12 months, until her pup is weaned. Mothers and pups will recognize each other by sound and smell after being separated. California sea lions become reproductively mature when they are 4-5 years old.
A number of threats face the California sea lion, most notably due to human-animal conflict and also climate change. Sometimes they are trapped legally (with a permit) to be displayed in circuses, zoos, and aquariums. They also cause problems for fishermen by stealing fish from the nets of commercial fishermen. Many of them have been killed by getting tangled up in discarded fishing gear. This species is also negatively affected by El Niño, which reduces the food supply and increases death rates. (El Niño is a natural phenomenon occurring every 4 to 12 years for several months, and which causes the ocean surface water to become warm.) Other causes of death include infection, disease, pollution, poisoning, and toxic phytoplankton blooms.
According to the IUCN Red List, the total California sea lion population size is approximately 387,646 individuals. This includes estimates of specific populations in these areas: the population on the Channel Islands and at haul-out sites between Point Conception and Point Reyes - 153,337 individuals; in the USA - 296,750 individuals; on the Pacific coast - 58,859 individuals; in the Gulf of California, 32,037 individuals. Overall, currently, California sea lions are classified as Least Concern (LC) and their numbers today are increasing.
California sea lions may have an influence on the fish population due to their diet. They are also important as prey for their natural predators (great white sharks, bull sharks, killer whales).
