Durham scientists track year-round movement of emperor penguins from space
For the first time scientists have used freely available satellite radar imagery to track emperor penguins through the polar winter giving a year-round view of their movements.
The research team, led by geographers at Durham University, UK, say monitoring the endangered birds through the Antarctic’s dark months is important because this is a key stage in their breeding cycle.
Knowing the penguins' movements during this period could help support future conservation efforts.
Emperor penguins rely on stable sea ice attached to the coastline for roughly nine months to breed and raise chicks.
They are threatened by climate change, and their population is predicted to decline rapidly this century due to the decreasing Antarctic sea ice.
Earlier this year the emperor penguin was classed as Endangered, according to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.
The research team also included the British Antarctic Survey, the University of Canterbury, New Zealand, and Woods Hole Oceanographic Institution, USA.
The findings are published in the journal Communications Earth & Environment.
Research lead author Dr Grant Macdonald, a postdoctoral research associate, in the Department of Geography, Durham University, said: “Emperor penguins live in one of the most inhospitable places on Earth so they can be difficult to monitor, especially during the polar winter when it’s dark for 24 hours a day.
“We’ve shown that satellite radar imaging is a very useful tool for understanding their behaviour during a key part of the breeding cycle and particularly their response to environmental change during winter.
“Gaining a year-round picture of their behaviours is important because we know the penguins are very vulnerable to climate change and changes in sea ice or the floating parts of the Antarctic ice sheet breaking up.”
The researchers used the European Space Agency’s (ESA) Copernicus Sentinel-1 synthetic aperture radar (SAR) mission to track the movements of emperor penguin colonies during winter between 2017 and 2024.
The birds, which have an average height of about four feet, stood out on radar against the flatter winter sea ice.
This meant the research team could track their movements throughout the year, even when it was not light.
The team combined the satellite radar imagery with medium resolution summer optical imagery to track the movement of colonies at Atka Bay, Coulman Island, and Cape Washington in Antarctica. Optical images came from ESA's Sentinel-2 and NASA's Landsat 8 satellites.
The radar imagery also picked up trails of the penguins’ guano (their poo) during late summer. This was confirmed by additional optical imagery, helping scientists to further piece together the birds’ movements.
Although emperor penguins are less mobile than during summer, all three colonies showed movement in winter, which varied between different years and colonies.
At times, different groups within the colonies were seen to move as one away from the sea ice edge despite its apparent stability.
Co-author Dr Peter Fretwell, of the British Antarctic Survey, said: “Winter is a critical time in the emperor penguins’ breeding cycle, but the optical satellites that we usually use to track the colonies are blind at this time due to the darkness of the polar night. The ability of these radar-based satellites, that can take imagery regardless of illumination, gives us a vital insight into the year-round behaviour of these endangered birds.”
The researchers acknowledged the European Space Agency and NASA for making the imagery, and Google Earth Engine for hosting.
The study was funded by the Natural Environment Research Council (NERC), UK, a Royal Society New Zealand Rutherford Discovery Fellowship and the US Department of Defense.