In zoological environments, successful mating has been observed in males as young as two years. In the wild, social factors greatly influence a male's breeding success. Males may not successfully reproduce until about nine years of age, when they attain full size and are able to compete for females.
California sea lions tend to breed on the same section of beach year after year. Sea lions generally favor beaches on the windward side of islands.
California sea lion bulls establish breeding territories on the beach from May to August. The peak of mating activity is in late June and early July. Galápagos sea lions may mate from May to January.
A male with an established territory breeds with an average of 16 females in one season.
Female California sea lions come into estrus ("heat") about three to four weeks after giving birth. Studies show that mating generally takes place about 20 to 30 days after giving birth.
Females initiate courtship and copulation by displaying submissive postures in front of the male. They rarely breed more than once in a single season.
Copulation has been observed on land and in shallow and deep water.
Courtship and copulation may last from a few minutes to a few hours. The female terminates copulation by raising her head and shoulders and biting the male’s neck.