Scientists Discover an Emperor Penguin Colony From Poop Stains in Satellite Images

Geospatial scientist Peter Fretwell was really studying sea ice loss. But as he pored over satellite images of Antarctica, he couldn’t help but notice a small, brown stain amid the otherwise pristine blue and white ice.

Fretwell, who works for the British Antarctic Survey, knew right away that he needed to investigate further, as brown stains in Antarctica typically mean only one thing: penguin poo.

He’d been looking at photos from the Copernicus Sentinel-2 satellites when he made the initial guano discovery. Fretwell then used high-resolution images of the same location, captured by the Maxar WorldView-3 satellite, to confirm his hunch that penguins were indeed living there.

And they weren’t just any penguins, either—he discovered a previously unknown colony of emperor penguins, the tall, black-and-white birds with yellow ear patches. Scientists estimate that roughly 500 penguins are living at the site, the British Antarctic Survey announced last month.

With this newly discovered rookery, which is located at Verleger Point in West Antarctica, scientists have now identified 66 total emperor penguin colonies along the coast of the White Continent.

Satellites have helped researchers discover half of all known emperor penguin colonies. Ground-based exploration is also needed, as Yan Ropert-Coudert, an ecologist not involved in the study, told the Associated Press after a similar find in 2020. But satellites have become an essential tool for studying the tuxedo-wearing birds, which live in remote, hard-to-reach areas of Antarctica.

“This is an exciting discovery,” says Fretwell in a statement. “The new satellite images of Antarctica’s coastline have enabled us to find many new colonies. And whilst this is good news, like many of the recently discovered sites, this colony is small and in a region badly affected by recent sea ice loss.”

Other species, like gentoos and Adélies, build nests out of pebbles on ice-free ground along the Antarctic coastline, primarily during the continent’s summer from roughly October to March. Emperor penguins, however, are the only group that reproduces during the frigid Antarctic winters. They also prefer to breed on sea ice, with males sheltering eggs from the cold by carefully holding them on their feet and covering them with a special brood pouch.

This preference for sea ice, however, means that emperor penguins are particularly vulnerable to warming temperatures brought on by human-caused climate change. The amount of sea ice in places like Antarctica and the Arctic is shrinking as the planet gets hotter.

Climate change risk to emperor penguins

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“Last year, we had the minimum ever sea ice extent in Antarctica, and this year is even worse, for two consecutive years,” Fretwell tells Live Science’s Tom Metcalfe.

Unless greenhouse gas emissions decrease, an estimated 70 percent of emperor colonies may face extinction by 2050. Nearly all colonies—some 98 percent—could become quasi-extinct by the end of the century, per a 2021 study. The International Union for Conservation of Nature categorizes emperor penguins “near threatened,” and the U.S. Fish and Wildlife Service has listed the birds as a threatened species under the Endangered Species Act.

“Most emperor penguins will never see a human in their lifetime, but what we’re doing on the other side of the world is slowly killing them,” says Fretwell to the Guardian’s Hannah Devlin.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.