The California sea lion is a highly gregarious species, hauling out in large groups, although tending to feed individually or in small groups, unless large quantities of food are present. They feed on a large number of different fish species (including some commercial species), such as northern anchovies, pacific whiting, mackerel and are known to also take some cephalopod species. Dives usually last about two minutes, but can last up to ten minutes, and average depths of 26 to 98 metres, although California sea lions have been known to dive to well below 200 metres (2).
The breeding season starts in May, at which time adult males begin to fight for a territory. Most males are unsuccessful and retreat to the sea, or to bachelor beaches nearby. Successful males guard their territory and maintain boundaries with routine displays and frequent barking. A male may maintain his territory for up to 45 days depending on other competitive males and on fat reserves. Females give birth to a single pup throughout May and June and are ready to mate again about 28 days after giving birth, although this interval is more variable among the population in Mexico. The mothers spend the first week after birth with their pup and then begin alternating feeding trips at sea (two to three days) with suckling bouts on land (one to two days), until the pup is weaned, at about ten to twelve months. The mothers and pups recognise each other after separation by sound and smell (2). The breeding season ends in August after which time most males migrate north and the females and juveniles disperse, but stay close to the breeding islands. Average lifespan is 15 to 24 years with the young reaching sexual maturity at about four to five years. However, males will generally fail to hold a territory until they are older (2).