The New Zealand sea lions feed on octopus, small fish, crabs, mussels, and penguins. They swallow pebbles (gastroliths) to aid in digestion. Their intestines may contain numerous gastroliths of irregular shapes. They vomit these gastroliths, as many as 20 at a time, along with squid tentacles and small fish. These sea lions will not leave their territory to feed during the breeding season. They have learned to follow fishing vessels and take advantage of discarded or escaped fish.