Antarctic emperor penguins on thicker ice
IMAGES FROM SATELLITES and aircraft have revealed a previously unknown breeding behaviour in emperor penguins – one which may help them better adapt to climate change.
Emperor penguins (Aptenodytes forsteri) are the largest and heaviest of all penguins and can reach up to 1.2m in height. Their population is estimated at near half a million, though the IUCN has classified them as near threatened.
Scientists had thought these birds formed breeding colonies exclusively on sea ice. This provides a flat surface for incubating eggs and easy access to the ocean for foraging, but is also predicted to diminish in extent and duration with rising temperatures.
Penguins on ice shelves and sea ice
Continental ice shelves are more robust structures with steep cliffs up to 60m high that form where glaciers flow out into the open ocean; however, it had been thought they were inaccessible to the birds.
Now, a new survey from the Australian Antarctic Division (AAD), the British Antarctic Survey (BAS), and the Scripps Institution of Oceanography in the USA, has found new colonies breeding on ice shelves at four locations across Antarctica.
“The first time we spotted a colony on the West Ice Shelf from a helicopter we had no idea how they could have gotten up there, since the cliff is 40m high,” says Dr Barbara Weinecke a co-author of the new study based at the AAD in Hobart, Tasmania.
Peter Fretwell, with the BAS, agreed it was puzzling. “Climbing up the sides of a floating ice shelf – which at this site can be up to 30m high – is a very difficult manoeuvre for emperor penguins. Whilst they are very agile swimmers they have often been thought of as clumsy out of the water.”
Emperor penguins adapting to climate change
It turned out that these birds had found a snow ramp that led from the sea ice onto the shelf. It was the discovery of this initial colony that led the researchers on to searching for more of them – four in total, all on different ice shelfs.
The experts says it’s not yet clear whether this behaviour is new or just hasn’t been previously observed.
“Breeding on ice shelves may be an adaptation employed by emperor penguins when sea ice conditions are poor, but this is only possible where emperor penguins have access to the top of an ice shelf. This is not the case at all colony sites,” Barbara says. “Of the four colonies we observed, three were located in areas with marginal sea ice conditions”
It may be that this kind of behaviour – relocating from sea ice to ice shelves – is not widespread among other penguin populations and only further research will tell.
Nevertheless, “emperor penguins are far more flexible than we give them credit for,” Barbara says.
The new findings are published in the journal PLoS One.