For Antarctic Penguins, Molting Can Now Be Deadly

Emperor penguins have always depended on a yearly, full-body molt to survive—but new research suggests that this natural routine is becoming increasingly dangerous as Antarctic sea ice disappears.

According to reporting by BBC, adult emperor penguins must remain on solid sea ice for 30 to 40 days each year while they shed and regrow their thick, waterproof feathers. During this time, they cannot hunt and may lose up to half their body weight. Without their specialized feathers—essentially built-in wetsuits—even a brief swim can be deadly. Entering the ocean mid-molt can leave them vulnerable to predators, hypothermia, and extreme exhaustion.

Using satellite imagery collected between 2019 and 2025, scientist Peter Fretwell of the British Antarctic Survey identified large brown patches of discarded feathers in West Antarctica—clear evidence of molting colonies. However, when record-low summer sea ice struck from 2022 to 2024, both the feather patches and many of the penguins largely disappeared.

Researchers observed only 25 groups in regions that would normally host closer to 100 colonies, raising concerns about widespread deaths or forced migration. Fretwell described the discovery as an alarming moment.

Some penguins appear to be adjusting by molting on shallow ice shelves instead of traditional sea ice. But scientists warn this shift could interfere with feeding patterns and breeding cycles.

The findings, published in Communications Earth & Environment, suggest the species may face steeper challenges than previously thought—and could accelerate projections about the emperor penguin’s long-term survival.