Just off the southernmost tip of South America, a cluster of small islands presents a huge puzzle for marine mammal experts.

The Falkland Islands, isolated in the far reaches of the southwest Atlantic Ocean, once boasted one of the world’s largest populations of southern sea lions. Now, they have one of the smallest. Hunting is the main reason for historical declines of seals and sea lions worldwide, but the Falklands population never recovered even though commercial hunts ended more than half a century ago.

That’s especially odd, because elsewhere around the globe, other populations of sea lions and seals that were hunted to near extinction have bounced back. For example, the neighboring Antarctic fur seals, with pelts so prized