By analysing satellite images of penguin guano, scientists found diets of Adélie penguins are shifting as sea ice melts in Antarctica
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Scientists have used NASA satellite images of penguin poop (guano) to determine how Adélie penguins’ diets are shifting in the wake of climate change.
The new study, published in Current Biology, found satellite images to be the best way of studying penguin colonies across the Antarctic continent to figure out their diets. Scientists used measurements of the colour of guano across visible and infrared wavelengths to infer what penguins had been eating.
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‘Antarctica has experienced rapid environmental change in recent decades, and this approach gives us a new and powerful tool to learn how it has affected penguins,’ said co-author Michael Polito.
Their findings were concerning: over a 30-year period, Adélie penguins in places with sea ice ate more fish – but in regions and years with less sea ice, they relied more heavily on krill.
Populations with more krill-based diets were likely to be declining faster than colonies with fish-based diets. Previously, research has found that chicks fed more fish become larger and have better chances of survival than chicks fed more krill.
Adélie penguins depend on a relatively small number of prey species to survive, such as Antarctic silverfish and krill. Apart from being less nourishing than fish, krill is becoming less abundant in parts of Antarctica due to both climate change and increased consumption by recovering whale and seal populations.
The study marks the first time that satellites have been used to capture food-web dynamics at both a continental scale and across decades.
‘Satellites enabled us to do something that would otherwise be impossible,’ said researcher on the study and assistant professor Casey Youngflesh.
‘The innovation wasn’t the satellite technology itself, but the ability to leverage these decades of satellite imagery with modern geochemical, statistical and computational tools. No one intended for these satellites to be used to monitor penguins, but now we’re able to use them in these novel ways.’
Until now, studying the diet of Adélie penguins has been difficult, largely due to the continent’s vast, icy terrain, which makes fieldwork logistically challenging. Researchers can visit some penguin colonies and collect samples, but it remains almost impossible to sample every colony repeatedly across decades.
