Imagine if your community pooped so much it was visible from space. A supercolony of 1.5 million Antarctic Adélie penguins has bragging rights to this achievement, after scientists discovered the birds thanks to satellite images of their pink guano.
Despite its large population, the colony has managed to remain off the maps since it first took roost on the Danger Islands some 3,000 years ago. The archipelago, which is named for the dangerous ice cover that surrounds it even in the summer, sits near the tip of the Antarctic Peninsula, and has barely been explored.
But when scientists developed an algorithm for detecting penguin guano in NASA Landsat imagery, the Danger Islands showed up as an untapped hotspot.
"We thought that we knew where all the penguin colonies were," said Heather Lynch, a Stony Brook University ecologist, at a news conference during the American Geophysical Union (AGU) meeting last week. “But in fact, this small archipelago, that measures only 15 kilometers from one end to the other, [has] more Adélie penguins than the entire rest of the Antarctic peninsula combined.”
Lynch and her colleagues presented new findings about these penguins at the AGU meeting, including evidence that the population peaked in the 1990s, and has declined by about 10 to 20 percent over the past 20 years.
But the story of the colony’s detection stretches back to 2014, when Lynch and Mathew Schwaller, her colleague at NASA’s Airborne Science Program, first noticed pinkish stains of guano in satellite images of the archipelago.
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To follow up on the ground, researchers embarked on the Danger Islands Expedition in December 2015. On the trip they surveyed the full island chain for the first time in history, with the help of aerial drones. The findings were published in Scientific Reports in March.
“Our results validate the use of Landsat medium-resolution satellite imagery for the detection of new or unknown penguin colonies and highlight the utility of combining satellite imagery with ground and [aerial drone] surveys,” the team wrote in the paper.
Researchers plan to continue studying the Danger Islands supercolony, both to better understand its history and to protect it from future threats, such as climate change. For instance, monitoring the color of the guano can reveal the colony’s primary diet—white poop means fish-heavy meals, and pink poop means a mostly krill menu.
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