The main predators of Steller sea lions are killer whales, sharks and humans. They mate and give birth on land. During this time, the males establish a harem and mate with many females on their territories, demonstrating their polygamous nature. Females give birth to one pup annually, but do not give birth every year. Pups are able to crawl and swim after birth.
Females accept only their pups, recognizing their pup's vocal and olfactory cues.
Pups will approach other females, but are often bitten or thrown by females who have their own pups. Males defend territories for an average of two years. There is a high incidence of aborted Steller sea lion fetuses in the wild. Steller sea lions are mammals, so they need to come to the surface to breathe air. They spend a portion of their time on the land and venture out in the water to hunt for food.