California sea lions belong to the family, Otariidae, or "eared seals." This species is the most recognized of the seals, because they are often seen in shows at aquariums and zoos doing acrobatic tricks. These animals are known for their playfulness, intelligence, and noisy barking. Their color can range from chocolate brown for a male to a lighter, golden brown for a female. Their faces are "dog-like," and at about five years old, a male develops a bony bump on the top of his skull, known as a sagittal crest. Their external ears are obvious and they have long narrow forelimb flippers, which they use for very graceful swimming as well as “walking” on land.
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. A California sea lion is a very fast, agile swimmer and can often be seen wave riding and porpoising. Sometimes they are seen several miles offshore. Their dives typically last about two minutes, though they can last as long as ten minutes, and to average depths of between 26 and 98 meters, although they can go well below 200 meters.
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, 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. She spends the first week post birth with her pup and then begins alternating feeding trips out to sea (of two to three days) and suckling bouts on land (of one to two days), for ten to twelve months, until her pup is weaned. Mothers and pups will recognize each other by sound and smell after being separated. California sea lions are sexually mature when 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 the 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 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).