Adelie Penguins: Satellite Images Reveal Colony Size and Diet
Satellite Images Shed Light on Penguin Poop
NASA-funded researchers are using satellite images to study Adelie penguins, one of the most well-known and least mysterious animals on Earth. The key to their research? Penguin guano.
The krill-heavy diet of Adelie penguins turns their guano a striking pink color, which shows up well in satellite images. By studying these images, researchers can find remote penguin colonies and even reconstruct the diet and history of the colonies over time.
Guano Reveals Colony Size
Satellite images don’t show individual penguins, but they can reveal the size of a colony by detecting the bright pink guano stains.
“We can use the area of the colony, as defined by the guano stain, to work back to the number of pairs that must have been inside the colony,” says Heather Lynch, an ecologist at Stony Brook University.
Algorithm Discovers Hidden Colony
Researchers spent 10 months poring over satellite images of Antarctic islands to create a global survey of Adelie penguin colonies. However, they realized they had missed a massive colony on Heroina Island in the remote Danger Islands.
They turned to an algorithm to help them find poop-peach colored pixels, and the algorithm discovered the hidden colony.
“We thought that we knew where all the [Adelie] penguin colonies were,” says Lynch. “We, I think, had missed it in part because we hadn’t expected to find them there.”
Satellite Images Track Population Changes
Researchers are reviewing satellite images dating back to 1982 to learn about the population rise and fall of individual Adelie colonies.
“It is interesting that no obvious trend in diet was seen over time, despite changes in the physical environment,” says Casey Youngflesh, a postdoc at the University of Connecticut. “This was a big surprise, since the abundance and distribution of Adelie penguins has changed dramatically over the last 40 years and scientists had hypothesized that a shift in diet may have played a role.”
Guano Analysis Confirms Diet Estimates
To test their idea, the team collected guano from the colonies. They found that their diet estimates from the satellite images correspond closely with what the penguins are actually eating.
No Link Between Diet and Population Size
However, when they compared the diet data with fluctuations in colony size, they were surprised to find no strong connection.
“This was a big surprise, since the abundance and distribution of Adelie penguins has changed dramatically over the last 40 years and scientists had hypothesized that a shift in diet may have played a role,” says Youngflesh.
Understanding Population Changes
Researchers would like to better understand the dramatic population changes seen in some Adelie penguin colonies. Getting a handle on the size of the colonies and their natural fluctuations over time is the first step to understanding what is happening.
That will help researchers manage and protect the penguins as more man-made threats, including climate change and krill fishing, put pressure on their nesting grounds.