Editor, Earth News
Emperor penguins make their mark
If you want to know where penguins go, then study their poo.
Emperor penguins sully the ice with so much guano that scientists are able to use these poo stains to locate new breeding colonies.
What's more, they can spot from space where the colonies have been, by scouring satellite images for the tell-tale stains left behind by the birds.
Scientists from the British Antarctic Survey have already used the technique to find 38 colonies of Emperor penguin.
"We can't see actual penguins on the satellite maps on the satellite maps because the resolution isn't good enough," says British Antarctic Survey (BAS) mapping expert Peter Fretwell. "But during the breeding season the birds stay at a colony for eight months."
Satellite image of guano smear left at Cape Washington, Antartica.
And when they do, they leave behind huge reddish brown patches of guano on the ice.
"The ice gets pretty dirty and it's the guano images we can see," says Fretwell.
In the journal Global Ecology and Biogeography, BAS scientists describe how they used satellite images to survey sea-ice around 90% of Antarctica's coast, in a bid to search for new colonies of Emperor penguins.
Images were downloaded from the Landsat Image Mosaic of Antarctica (LIMA), a collage of Landsat images of Antarctica created by the US Geological Survey, BAS and NASA.
In total, the survey discovered 38 colonies. Ten of those were new. Of previously known colonies, six had relocated and six were not found again.
A harsh life
Is the only penguin species to breed through the Antarctic winter
During their breeding season, temperatures fall to -50°C and winds reach 200km per hour
To cope with the cold, adults have a dense double layer of feathers and a large fat reserve
"This is a very exciting development," says BAS penguin ecologist Phil Trathan.
"Now we know exactly where the penguins are, the next step will be to count each colony so we can get a much better picture of population size. Using satellite images combined with counts of penguin numbers puts us in a much better position to monitor future population changes over time."
Studying Emperor penguin colonies is extremely difficult.
Emperor penguins spend a large part of their lives at sea. Then during the Antarctic winter they return to their colonies to breed on sea-ice, an inhospitable environment where temperatures drop to -50°C.
The new study also suggests that Emperor penguins may be feeling the affects of climate change.
The new, the old and the missing: a map of Emperor penguin colony locations
Previous research, based on over 40 years of population data from a long term study colony of emperor penguins in Terre Adélie in the Antarctic, has predicted that populations have a high probability of declining by 95% or more in the face of climate change.
These predictions are based on one colony that is located relatively far north at 66.6° South.
The six colonies of Emperor penguins that new survey could not locate were originally recorded north of 70° South.