San Francisco’s Sea Lions, mostly adult and juvenile males, return to Pier 39 because it is a comfortable place to sleep, there is an abundant natural food supply (fish) nearby, and there are no predators like the great white sharks or killer whales. Sea Lions have ear flaps, long front flippers without claws, and can walk on land. All Seals have no ear flaps, long front flippers with claws, and crawl on land.