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Emperor penguins breed in large colonies, but each pair raises just one chick per year.PETER FRETWELL/BRITISH ANTARCTIC SURVEY
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Emperor penguins need stable sea ice to reproduce and raise their chicks. But with the ocean waters warming around Antarctica, the ice is breaking up earlier and earlier in the season, causing widespread abandonment of penguin breeding colonies.
The finding, reported today in Communications Earth & Environment, “is bad news,” says Annie Schmidt, a seabird ecologist at Point Blue Conservation Science who was not involved in the work. Sea ice conditions vary from year to year, and colonies have failed to breed before. But if a whole region becomes unsuitable, penguins will find it difficult to locate an alternate spot, Schmidt says.
The sea ice in this area may become so unreliable that the colonies will disappear over the next few years, says Gerald Kooyman, a physiologist and ecologist. “I think we’re past the tipping point for these colonies,” says Kooyman, who spent his career at the Scripps Institution of Oceanography studying Antarctic penguins.
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The British Antarctic Survey has been monitoring penguin colonies in Antarctica by satellite for about 15 years. Last year, Peter Fretwell, a remote sensing expert and geographer at the organization, and colleagues noticed sea ice breaking up in places by late October. Emperor penguins arrive at their breeding colonies in March and April. Chicks, which hatch between August and September, only develop mature feathers in December and January. If sea ice breaks up before then, the younglings will drown or freeze. An October breakup, then, would almost certainly result in disaster.
Indeed, satellite images revealed that as the sea ice broke up in 2022, penguins abandoned one of the colonies starting in late October. Penguins from three other colonies fled by early December. Only one colony, on Rothschild Island in the far north, remained intact and successfully raised chicks.
The colonies in the Bellingshausen Sea —about 10,000 breeding pairs in total—represent just a small fraction of the total population, thought to be more than 250,000 breeding pairs. “This one event is not going to doom the species,” Schmidt says. Most of the penguins, which typically live about 20 years, will breed again the following season. But based on the current conditions of the sea ice, Fretwell expects that this year will be equally bad for the five colonies. “I’m quite worried,” he says.
