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Through the winter months, emperor penguins lay their eggs, hatch their chicks, and huddle together for warmth. They do much of this in darkness, as the Antarctic sun disappears below the horizon for months on end.
That has made them surprisingly difficult to watch. Most satellite images rely on sunlight, so until recently scientists could track emperor penguin colonies only in the brighter months of the year.
But when when Grant Macdonald and his colleagues looked at images of Antarctic sea ice in winter, they spotted something unexpected: a “bright white splodge of pixels” moving across otherwise dark, smooth ice.
It turned out to be a penguin colony.
Macdonald, a geographer at Durham University, and his team soon identified several other colonies, and confirmed their findings with satellite images taken when the sun returned in September. For them, this new knowledge of what a penguin colony looks like from space, in the dark, opened an “exciting opportunity” to track them “throughout the whole breeding cycle”, using years of accumulated satellite images.
One colony particularly surprised them: penguins in Atka Bay repeatedly moved onto glacier ice each winter even though their preferred sea ice was still stable.
How much ice is just right?
The discovery shows how closely emperor penguins’ lives are tied to breeding in precise conditions. Dana M. Bergstrom, an ecologist at the University of Wollongong in Australia, describes this as a kind of Goldilocks zone. Too far from the ice edge and adults will take too long to return with food. Too close, and the ice may break up before the chicks have developed the waterproof plumage that keeps them safe in cold seas.
Leaping out of the water, and into the Goldilocks zone. Stuart Holyroyd / Alamy
That Goldilocks zone, says Bergstrom, now “appears to be reducing” as the world warms and sea ice retreats. She cites research that tracked 16 emperor penguin colonies from 2009 to 2024 and noted an average 22% fall in numbers.
This is part of a trend across Antarctica, one of the world’s fastest-warming regions. Earlier this year, Haosu Tang, a climate scientist at the University of Sheffield, wrote about a period of extraordinary warming even by Antarctic standards.
This was a heatwave in July and August 2024 – the middle of winter – when temperatures rose by “up to 28°C above average” and remained high for weeks. “To put that in perspective,” notes Tang, “a similar anomaly in the UK would push January temperatures into the mid-30°Cs.”
Climate change made the 2024 winter heatwave both stronger and more likely. In fact, if greenhouse gas emissions remain high, Tang and colleagues note an extreme on this scale could become “up to 20 times more frequent by the end of the century”.
Satellites are also revealing climate-driven changes across the food web of the frozen continent – such as what penguins are eating.
Pink poo from space
Casey Youngflesh of Clemson University in the US says the “colour of penguin poop, as seen from space” is showing us how Antarctica is changing.
His research focuses on Adélie penguins, a species that lives in enormous colonies on rocky outcrops all around the continent. They leave behind enough guano (poo) to be seen from space.
Adélie penguins on rocks stained pink by krill-heavy guano. Steven J Kazlowski / Alamy
Youngflesh and his colleagues realised this could provide a record of what the penguins were eating: krill have pinkish shells that are only partly digested, so the more krill the penguins eat, the pinker the guano. They checked this relationship by collecting samples and analysing them in a small makeshift lab on a ship in the Antarctic, “which likely smells of penguin guano to this day”.
Researchers then examined about 4,000 satellite images stretching back to the 1980s and found a clear relationship to sea ice. When there was more sea ice, Adélie penguins tended to eat more fish, but when there was less, they instead ate more krill.
Less sea ice and fewer fish are “bad news for penguins”, writes Youngflesh. “Adélie penguin chicks are typically heavier when fed fish as opposed to krill, and heavier chicks are more likely to survive into adulthood.”
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There is something remarkable about being able to view global changes play out in somewhere so remote, in such detail.
Emperor penguins were first recorded scientifically by Robert Falcon Scott on the Discovery expedition in 1902. Just over a century later, they’re in real trouble.
In early 2026, emperor penguins, along with Antarctic fur seals, were officially listed as endangered. A “swift arc from discovery to extinction risk”, note Mary-Anne Lea and her colleagues at the University of Tasmania.
The new designation reflects a combination of threats: warming seas, changes in krill, extra competition from recovering whale populations, bird flu and more. But sea ice is the main factor, and emperor penguins are especially vulnerable because their entire breeding cycle depends on it.
Lea and colleagues argue the new classification makes continued monitoring urgent. The satellites that are now letting us watch these colonies through the dark winter may therefore become even more important: helping scientists see the effects of climate change in the Antarctic on the animals who live there.
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