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Emperor penguins have recently abandoned this major breeding site in Antarctica because of unsteady sea ice.

Christopher Walton

Emperor penguins flee unsteady ice after ‘unprecedented’ failure to breed

Antarctica's charismatic emperor penguins are thought to be particularly vulnerable to climate change, because warming waters are melting the sea ice where they live and breed. Now, the penguins have abandoned one of their biggest colonies after breeding pairs there failed to raise almost any new chicks in 3 years. Although the move cannot directly be attributed to climate change, researchers say it is an ominous sign of things to come for the largest of penguin species.

Emperor penguins need sea ice that remains solid for most of the year while they find mates, breed, and raise their chicks. This requirement has become a critical problem for their second-largest colony, in Halley Bay in the Weddell Sea. Starting in 2015, sea ice there has been disrupted by powerful storms driven a particularly intense El Nino, the periodic warming of the Pacific Ocean that alters global weather patterns.

To see how the colony was faring, remote sensing expert Peter Fretwell of the British Antarctic Survey in Cambridge analyzed high-resolution satellite imagery, which shows individual penguins and groups of the birds, from 2009 to 2018. Over that time, Fretwell estimated, the colony hosted between 14,000 and 25,000 adults and chicks. Since 2016, however, that population has dropped to nearly zero, Fretwell found—and he saw almost no chicks, an “unprecedented” period of reproductive failure for emperor penguins, he and co-author Phil Tranthan, a penguin ecologist with the British Antarctic Survey, report online in Antarctic Science.

“Since we know little about the population trends of emperor penguins in most colonies, this is not good news,” says Dee Boersma, a penguin ecologist at the University of Washington in Seattle who was not involved in the research.

The breeding failure might by itself not have a long-term impact on the species. “Since … some individuals [live] more than 30 years, these penguins should have other breeding opportunities,” Boersma says. Many of that colony’s penguins seem to be moving to the nearest adjacent colony, 55 kilometers away, which increased in population 10-fold as the population fell at Halley Bay.

But the change is still worrying, researchers say, because this part of the Weddell Sea was thought to be relatively insulated from the dramatic changes to ice happening elsewhere around the continent. “I thought the Weddell Sea would be one of the last places we would see this,” Tranthan says. “The fact that these penguins are still vulnerable is a surprise.”