During Antarctica's dark winter months, when the sun does not appear for months at a time, emperor penguins lead their most vulnerable lives—incubating eggs and raising chicks on sea ice. Until recently, these periods remained almost inaccessible to observation: conventional satellite imagery requires light, and ground expeditions at such times are nearly impossible.
Now researchers from Durham University have for the first time applied synthetic aperture radar (SAR) data from the European Space Agency's Sentinel-1 satellites. The radar sends microwave pulses and records their reflection, independent of sunlight and cloud cover. In the images, penguin colonies appear as bright, moving clusters of pixels against the smooth ice—this is how they managed to track the three largest colonies from 2017 to 2024, sometimes on a daily basis.
The observations showed that in winter the colonies are less mobile, while in spring and summer the birds travel long distances. In Atka Bay, for example, in seven out of eight years the colony moved from sea ice to a glacier in early spring, even though the sea ice remained stable. The reasons for this behavior have yet to be determined, but it is already clear that previous assumptions about the species' preferences need to be revised.
Earlier satellite observations during the light season led to the discovery of dozens of new colonies and radically changed our understanding of the species' abundance and distribution. Now SAR data fill the winter gap and make it possible to monitor the penguins' response to environmental changes throughout the entire breeding cycle.
Since 2016, Antarctic sea ice has noticeably declined and appears to have shifted to a new, less stable state. In 2026, emperor penguins were classified as an endangered species, mainly due to forecasts of further ice loss. The ability to monitor year-round using freely available satellite data is becoming especially valuable for assessing threats and planning conservation measures.
Combining radar and optical imagery allows not only counting the birds but also detecting signs of their activity, such as guano stains. This paves the way for more accurate population estimates and timely responses to climate shifts.
Freely accessible satellite data now offer a chance to better understand how emperor penguins are adapting to a changing Antarctica and help make informed decisions for their conservation.
