- Scientists have discovered new sites in Antarctica where emperor penguins gather for their annual molt, a vulnerable life stage when they shed and replace all their feathers.
- Through satellite data, they also discovered that many of these sea ice sites might have melted from under the penguins.
- The discovery suggests that the threats posed by global warming to emperor penguins might be more dire than previously thought.
The plight of the emperor penguin might be more dire than previously thought.
For the first time, scientists have used satellite data to discover new locations in Antarctica where the birds go to shed and replace their feathers every year, an event known as molting. However, they also found that these molting sites might have melted from under the penguins, potentially causing fatalities.
Emperor penguins (Aptenodytes forsteri), native to Antarctica, are the biggest of the penguin species. Since they heavily rely on sea ice for their survival, global warming is one of the major threats to their existence. A 2021 study estimated that the birds could lose 98% of their colonies and become “quasi-extinct” by the end of the century if sea ice continues to decline at projected rates.
Every year, around late January, emperor penguins move to stable sea ice attached to a coastline to molt. It’s a life stage that scientists dub “catastrophic molting” because, unlike other animals, penguins shed all their feathers at once. Molting, however, is a vulnerable life stage. For one, the process of shedding and growing new plumage consumes a lot of energy. Over the four to five weeks of molting, the birds also lose 40-50% of their body weight.
“Because the penguin is not waterproof during that period, they can’t go out into the sea to forage and hunt,” Peter Fretwell, senior geographic and remote-sensing scientist at the British Antarctic Survey, who discovered the new molting sites, told Mongabay in a video interview. “So it has to stay on the ice being very hungry.”
Despite molting being a critical life stage, it’s severely understudied because the penguins go deep into the ice mass while seeking out stable locations, making them hard to spot and get to. Additionally, they often congregate in small groups distributed over thousands of square kilometers of frozen sea.
In fact, Fretwell discovered the new molting sites by chance. He was analyzing satellite images for breeding sites when he came across a location with “strange brown stains which looked like penguins.” Since the images were captured in February, when penguins usually shed their feathers, he could confidently infer that those penguins were not breeding but were indeed molting. “One of the reasons we saw them in such numbers, rather than just one or two brown specimens, was because the sea ice had retreated in its extent and concentrated all the penguins into one small area,” Fretwell said.
As he looked through satellite data from previous years from the same location, Fretwell observed that sea ice cover had declined while the penguins were molting on them. “What we saw was that, over three years, the ice had gone out from under them when they’d been molting.”
While he can’t say with certainty how many penguins might have died, it’s clear that if they go into the water without their waterproof feathers, especially in a weakened state, they can suffer hypothermia. “We know this could be fatal for them,” Fretwell said. “It’s likely that the extinction horizon will suddenly get a lot closer than previously thought.”
For now, Fretwell said, the discovery has brought up more questions than answers. How many birds were affected? How many survived? Where else is this happening across the continent?
Finding answers to these questions will form the crux of further research, Fretwell said. He and his team also plan to use the data as evidence to further advocate for the protection of emperor penguins.
“Their only threat really is global warming and it’s purely climate change that’s driving the populations down,” Fretwell said. “We can now see what’s happening to them but it’s probably happening to many other species.”
Banner image: Emperor penguins rely heavily on sea ice and are estimated to lose 98% of their colonies by 2100 if sea ice continues to decline. Image courtesy of Niel Osborne.
Abhishyant Kidangoor is a staff writer at Mongabay. Find him on 𝕏 @AbhishyantPK.
Citation:
Jenouvrier, S., Che‐Castaldo, J., Wolf, S., Holland, M., Labrousse, S., LaRue, M., … Trathan, P. N. (2021). The call of the emperor penguin: Legal responses to species threatened by climate change. Global Change Biology, 27(20), 5008-5029. doi: 10.1111/gcb.15806
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