Island Sea Lions Offer Clues to Mysteriously Missing Mammals

The Falkland Islands population hasn’t bounced back despite an end to hunting over 50 years ago. Now scientists are closing in on the cause.

By Laura Parker

PUBLISHED AUGUST 11, 2016

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 that hunters had nearly wiped them out by the early 1900s, have rebounded to about three million individuals today.

For years, scientists blamed hunts off Argentina for the severe population decline in the Falklands. If the sea lions traveled from their island breeding grounds to the mainland while hunts were still happening, big commercial operations around the Argentine coast may have made too large a dent in their numbers.

But a new study based on sea lion genetics paints a much more complicated picture. For starters, it appears that the Falklands sea lions may not have been travelling to Argentina. Instead, a combination of changes to their habitat, including warmer waters due to climate change, has had a devastating impact that continues to ripple through the population.

“This realization is important, because it influences how we interpret threats to sea lion population persistence,” says Alastair Baylis, a marine ecologist with the Icelandic Seal Center and the South Atlantic Environmental Research Institute in the Falklands. “If we are correct, it suggests sea lions are more vulnerable than previously thought.”

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