For the past 40 years, the total number of Adélie Penguins, one of the most common on the Antarctic Peninsula, has been steadily declining – or so biologists have thought. With the help of a drone, a new study led by researchers from the Massachusetts-based Woods Hole Oceanographic Institution (WHOI), however, is providing new insights on this species of penguin.
In a paper released on March 2 in the journal Scientific Reports, scientists announced the discovery of a previously unknown “supercolony” of more than 1.5 million Adélie Penguins in the Danger Islands – a chain of remote, rocky islands off the Antarctic Peninsula’s northern tip, according to a press release from WHOI.
“Until recently, the Danger Islands weren’t known to be an important penguin habitat,” says co-PI Heather Lynch, associate professor of ecology and evolution at Stony Brook University, located in Stony Brook, N.Y.
These supercolonies have gone undetected for decades, she notes, partly because of the remoteness of the islands themselves and partly because of the treacherous waters that surround them. Even in the austral summer, the nearby ocean is filled with thick sea ice, making it extremely difficult to access, says WHOI.
In 2014, Lynch and colleague Mathew Schwaller from NASA discovered telltale guano stains (i.e., seabird excrement) in existing NASA satellite imagery of the islands – hinting at a mysteriously large number of penguins. To find out for sure, Lynch teamed with Stephanie Jenouvrier, a seabird ecologist at WHOI, Mike Polito at Louisiana State University (LSU) and Tom Hart at Oxford University to arrange an expedition to the islands with a goal of counting the birds firsthand.
When the group arrived in December 2015, they found hundreds of thousands of birds nesting in the rocky soil, and they immediately started to tally up their numbers by hand. Notably, the team also used a modified commercial quadcopter to take images of the entire island from above.
“The drone lets you fly in a grid over the island, taking pictures once per second. You can then stitch them together into a huge collage that shows the entire landmass in 2D and 3D,” says co-PI Hanumant Singh, a Boston-based Northeastern University professor of mechanical and industrial engineering, who developed the drone’s imaging and navigation system.
According to Northeastern, the drone flew roughly 30 meters above the surface of the islands – which was close enough for Singh’s machine learning algorithm to count each individual penguin autonomously, pixel by pixel.
“It’s unbelievable. We knew the colony existed, but we didn’t know how big it was,” says Singh.
He adds, “As soon as we did the first run, it became very obvious that counting penguins this way was more efficient than anything else we’ve ever thought of.”
Northeastern notes that the supercolony – which comprises 751,527 penguin pairs – includes the third- and fourth-largest Adélie penguin colonies in the world.
The accuracy that the drone enabled was key, according to LSU’s Polito. The number of penguins in the Danger Islands could provide insight not just on penguin population dynamics but also on the effects of changing temperature and sea ice on the region’s ecology, he says.
“Not only do the Danger Islands hold the largest population of Adélie penguins on the Antarctic Peninsula, they also appear to have not suffered the population declines found along the western side of Antarctic Peninsula that are associated with recent climate change,” says Polito.
Being able to get an accurate count of the birds in this supercolony offers a valuable benchmark for future change, as well, notes WHOI’s Jenouvrier.
“The population of Adélies on the east side of the Antarctic Peninsula is different from what we see on the west side, for example. We want to understand why. Is it linked to the extended sea ice condition over there? Food availability? That’s something we don’t know,” she says.
Funding for this research was provided by a grant to WHOI from the Dalio Ocean Initiative. Logistical support was provided by Golden Fleece Expeditions and Quark Expeditions.