They seem to form relatively small breeding colonies of only about 200 animals. Males defend moving territories and will herd harems of about 4-6 females. Mating takes place about 10 days after birth. Females nurse their pups until the next pup is born. The diet is broad and includes cephalopods, fish and sometimes penguins.
Sharks are the main predators of the Australian sea lion.
Australian sea lions were hunted heavily during the 17th and 18th centuries and their distribution was reduced around certain areas. They were taken more for their oil than their pelts as sea lion pelts are not as valuable as fur seal pelts. Pinnipeds have been protected in different parts of Australia beginning in Western Australia in 1892 but did not receive full protection until 1987. Even with protection, some are caught in fishing nets and killed by direct shooting by fishermen. Disturbance due to recreational use of islands may also be impacting the sea lions.