For Antarctic Penguins, Molting Can Now Be Deadly

Emperor penguins can't skip their annual wardrobe change, and that may now be killing them. A new study finds the birds' once-routine full-body molt has turned into a high-stakes gamble as Antarctic sea ice rapidly retreats.

• Adult emperors must park on stable sea ice for 30 to 40 days each year while they shed and regrow their uniquely insulating, waterproof feathers, reports the BBC. During that stretch, they burn up to half their body weight and are effectively grounded, without food.

• A dip in the ocean without their built-in "wet suits," in fact, can be fatal. A release notes that penguins who venture into the sea risk a weakened fight with predators, as well as hypothermia and exhaustion from plowing through so much energy during molting.
• Using satellite images from 2019 to 2025, British Antarctic Survey scientist Peter Fretwell spotted huge brown patches of discarded feathers in West Antarctica—until record-low summer sea ice hit from 2022 to 2024.
• Then, the feather fields, and most of the birds, largely vanished. Only 25 groups were seen in areas that should have held closer to 100, suggesting mass deaths or migrations out of the area. "This was really an 'oh my God" moment,'" Fretwell says.
• Some penguins appear to be shifting their molt to shallow ice shelves, but that adaptation may carry its own costs in terms of breeding and eating. The findings, published in Communications Earth & Environment, could force scientists to move emperor penguins' projected extinction timeline closer.