Adélie penguin populations have been declining in Antarctica — at least, that’s what scientists thought. An international team recently discovered a mega-colony of over 1.5 million penguins on the Danger Islands, according to the Woods Hole Oceanographic Institution (WHOI). Although evidence shows penguins are declining on the West Antarctic Peninsula, this mega-colony 100 miles away is thriving. According to the University of Oxford, the contrast suggests penguins are better off in undisturbed environments, lending credence to calls for a marine reserve.

Satellite and drone imagery and ground counts helped this team uncover the previously unknown penguin supercolony. It turns out 751,527 pairs of Adélie penguins make their home on the Danger Islands; according to Oxford, this is “the largest population on the Antarctic Peninsula.” The third and fourth biggest Adélie penguin colonies on the planet are part of this figure — sitting next to each other, according to the university. And it seems these penguins haven’t suffered the population decline neighboring colonies have in Antarctica.

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Related: The world’s largest wildlife sanctuary proposed for Antarctica

Oxford researcher Tom Hart said, “Scientifically, while this is a huge number of ‘new’ penguins, they are only new to science. Satellite imagery going back to 1959 shows they have been here all along. It puts the East Antarctic Peninsula in stark contrast to the Adélie and chinstrap penguin declines that we are seeing on the West Antarctic Peninsula. It’s not clear what the driver of those declines is yet; the candidates are climate change, fishing and direct human disturbance, but it does show the size of the problem.”

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Hart said the work lends support for including the Danger Islands in a proposed Weddell Sea marine protected area, describing the islands as a hotspot, but he also said their discovery underscores the need for enhanced protection in Antarctica’s west.

The journal Scientific Reports published the research online today. Scientists from institutions around the United States and France also contributed.

+ University of Oxford

+ Woods Hole Oceanographic Institution

+ Scientific Reports

Images via Michael Polito, © Louisiana State University and Rachael Herman, Louisiana State University, © Stony Brook University