The two-million-strong king penguin colony on Ile aux Cochon in 1982.   | Photo Credit: HENRI WEIMERSKIRCH

The planet’s largest colony of king penguins has declined by nearly 90% in three decades, researchers have warned. The last time scientists set foot on France’s remote Ile aux Cochons — roughly half way between the tip of Africa and Antarctica — the island was blanketed by two million of the flightless birds, which stand about a metre tall.

But recent satellite images show the population has collapsed, with barely 2,00,000 remaining, according to a study published in Antarctic Science. While adults will set to sea for days at a time foraging for food, the species does not migrate.

Why the colony on Ile aux Cochon has been so decimated remains a mystery. “It is unexpected, and particularly significant since this colony represented nearly one third of the king penguins in the world,” said lead author Henri Weimerskirch, an ecologist at the Centre for Biological Studies in Chize, France, who first set eyes on the colony in 1982.

Climate change may play a role. In 1997, a particularly strong El Nino weather event warmed the southern Indian Ocean, temporarily pushing the fish and squid on which king penguins depend south, beyond their foraging range.

“This resulted in population decline and poor breeding success” for all the king penguin colonies in the region, Mr. Weimerskirch said.

Migration is not an option because there are no other suitable islands within striking range.

Other factors may be contributing to the decline of the Ile aux Cochon colony, including overcrowding.

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