Emperor Penguins Face Death From Hypothermia During Molt As Sea Ice Disintegrates

Each year for millennia, emperor penguins have molted on coastal sea ice that remained stable until late summer—a haven during a span of several weeks when it’s dangerous for the mostly aquatic birds to enter the ocean to feed because they are regrowing their waterproof feathers. But as overall Antarctic sea ice extent dwindled to record lows in recent years, some of the frozen penguin platforms melted earlier than ever, forcing the weakened birds into smaller areas and possibly to a premature death in the icy ocean, according to British Antarctic Survey geographer Peter Fretwell, who helped pioneer counting emperor penguins from space.

“The sea ice wasn’t just breaking up into floes. In some years, it just disintegrated,” said Fretwell, author of a paper published Wednesday that matched the fate of the molting penguins against the ice records for seven years. “If they go into the water half-moulted, they’re really in trouble because they just aren’t very strong,” he said, adding that the birds lose up to half their body weight during molt. If they enter the water before they’re ready, they can get hypothermia and become easy prey for leopard seals.

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A series of satellite images shows how sea ice used by molting emperor penguins disintegrates before the birds have finished replenishing their feathers. Credit: CopernicusA series of satellite images shows how sea ice used by molting emperor penguins disintegrates before the birds have finished replenishing their feathers. Credit: Copernicus


Studying satellite images from 2018 to 2024, Fretwell mapped moulting emperor penguin groups along about 200 kilometers of the Marie Byrd Land coast, using the birds’ characteristic guano stains to pinpoint the groups. The analysis showed that in low-ice years the coastal ice platform shattered before molting ended. The impacts may already be tangible. Before 2022, over 100 groups of penguins had been identified in the same region, but in 2025, only 25 small groups were visible in satellite images, despite more favorable sea ice conditions.

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“There has been very little good news for emperor penguins recently, and they appear to be under great pressure through the changes to their sea ice environment,” she said. Ship-based surveys over many years suggest that penguins have historically chosen areas with high sea ice concentrations as their redoubts for molting. “If the sea ice becomes less reliable,” she said, “the birds will need to adapt and change their behaviours to survive.” Over the past three million years, emperor penguins have survived by adapting to huge sea ice variations, but they need somewhere to go, as well as time to adapt. That process typically unfolds over millennia during slow planetary climate cycles. But the speed of human-caused warming is a new and different shock to Earth’s climate and to emperor penguins, Fretwell said. “They’re probably the slowest-adapting bird species genetically, and unless they’ve got it in the locker already, they’re not going to adapt.”


A high-resolution satellite image showing clusters of molting emperor penguins. Credit: Vantor

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https://insideclimatenews.org/news/26022026/antarctic-ice-loss-threatens-emperor-penguins/