Females stay with their pups for about 9 days before beginning a regular routine of foraging trips to sea. Females mate 11 to 14 days after giving birth. Implantation takes place in late September or early October, after a 3-4 month delay. Weaning is not sharply defined as it is for most other pinniped species, but probably takes place gradually during the winter and spring prior to the following breeding season. Steller sea lion are distributed across the North Pacific Ocean rim from northern Hokkaido, Japan, through the Kuril Islands, Okhotsk Sea, and Commander Islands in Russia, the Aleutian Islands, central Bering Sea, and southern coast of Alaska, and south to the Channel Islands off California.
Sea lions continue to gather at both rookeries and haul-out sites outside of the breeding season.
The stock differentiation is based primarily on differences in mitochondrial DNA, but also on differing population trends in the two regions. Steller sea lions are opportunistic predators, feeding primarily of a wide variety of fishes and cephalopods. Prey varies geographically and seasonally. Steller sea lions have been known to prey on harbor seal, fur seal, ringed seal, and possibly sea otter pups, but this would represent only a supplemental component to the diet. The number of Steller sea lions in most areas has shown a continuous decline since the 1970s.