More than 1 million penguins who've been hiding in a remote part of Antarctica were recently discovered thanks to images taken from space and ... their own poop. A study in the Scientific Reports journal reveals the Danger Islands find of more than 750,000 pairs of Adélie penguins—a discovery researchers are calling a "total surprise," per the BBC. "It's a classic case of finding something where no one really looked," study co-author Tom Hart says. The detective work started in 2014, when satellite images taken from space showed enormous guano stains (guano being bird poop), per the Wall Street Journal. Those images spurred scientists to travel to the Danger Islands in 2015, where they realized the magnitude of their find. "I was amazed by the sheer number," study co-author Michael Polito says, per the Independent. "The water around the island boiled with penguins."
They counted the penguins by hand and with a drone that flew overhead snapping photos. It's a significant number, as this colony doesn't seem to have been as affected by population decline as other colonies on the Antarctic Peninsula. Researchers believe other colonies may have been adversely affected by a reduction in sea ice from climate change—krill, tiny crustaceans that are a staple in the penguin diet, live in the ice—an influx of fishermen, and other human disturbances. Because the archipelago where this new colony is located is so remote, the penguins there may have been protected from some of these factors. This group may have been around for decades, too: The scientists went back to satellite images taken in the late 1950s and, based on that evidence, they believe the penguin population there has been stable since that time. (A "catastrophic" breeding event among another Adélie colony.)