For nearly two decades, scientists have counted emperor penguins from space using ordinary satellite photographs — images that work beautifully in the summer sun but go completely dark when winter arrives. It was a frustrating limitation for researchers trying to understand one of the most climate-sensitive birds on Earth. Now, a team from Te Whare Wānanga o Waitaha | University of Canterbury has found a way to see them even in the perpetual night of Antarctic winter, and the implications for conservation are significant.
Led by Professor Michelle LaRue, the research team used high-resolution Synthetic Aperture Radar (SAR) imagery to track emperor penguin colonies during the months when traditional satellite photography becomes useless. SAR works differently from ordinary cameras: it sends radar signals down to Earth's surface and measures what bounces back. The commercial imagery used in the study, provided by Umbra, achieved a pixel resolution of just 25 to 30 centimeters — sharp enough for penguins to stand out against the ice. Because emperor penguins create a slightly rougher surface on the otherwise smooth fast ice, they appear as distinct signatures in the radar data.
"Because the fast ice is very smooth, there is little scattering, but the penguins are rough on a smooth surface, so they stand out nicely," Professor LaRue explains.
The timing matters enormously. Emperor penguin males spend the brutal Antarctic winter incubating eggs while females journey to sea to feed. Being able to count those winter huddles gives scientists a direct measure of breeding pairs — a far more meaningful indicator of population health than spring counts that come after months of potential losses. The team examined eight colonies, including seven in the Ross Sea and one at Atka Bay, and found they could distinguish between loose early-season gatherings, dense mating clusters, and the male huddles that form during egg incubation.
Crucially, the researchers validated their satellite observations against ground truth recorded by a documentary film crew working at one of the colonies. When Professor LaRue compared her radar interpretations with what the crew observed on the ice, the patterns matched closely — a finding that gives the team confidence their space-based counts are reliable.
Emperor penguins were recently added to the IUCN Red List of Threatened Species, and their breeding success depends entirely on stable sea ice that is increasingly threatened by warming temperatures. The ability to monitor them through winter offers a new window into how quickly conditions are changing and what that could mean for the species. Professor LaRue's team is now working toward what could become the first-ever breeding population estimate derived from winter SAR imagery, and they hope to link those observations with spring data to understand what happens between the critical count periods.
"We have seen fewer birds in springtime imagery over the last 10 to 15 years in many places, and we are still trying to figure out why that is," Professor LaRue says. "If we can estimate breeding pairs in winter, we can get a much better metric for understanding population change."