A new study of Antarctic emperor penguin colonies suggest that unexpected breeding behaviour may be a sign that the birds are adapting to environmental change. But their new behaviour is considerably riskier.
Analysis of satellite observations reveals that penguin colonies moved from their traditional breeding grounds during years when the thin layer of ice (sea ice) formed later than usual to the much thicker floating ice shelves that surround the continent.
The birds tend to breed on sea ice because it gives them easy access to waters where they hunt for food. In 2011 and 2012, when sea ice did not form until a month after the breeding season began, the birds moved up onto the neighbouring floating ice shelf to raise their young, explained Peter Fretwell of the British Antarctic Survey.
While it is encouraging that the emperor penguins appear to be adapting to climate change, their behaviour is risky. According to Fretwell, “climbing up the sides of a floating ice shelf – which at this site can be up to 30 metres 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.”
Whereas sea-ice is frozen salt water, ice shelves are made up of glacial ice that has flowed from the land onto the sea. At the outer edge of an ice shelf ice cliffs can form and these can be anything up to 60 metres high.
The emperor penguins’ reliance on sea ice as a breeding platform coupled with recent concern about changing patterns of sea ice has led to the species being designated as ‘near threatened’ by the IUCN red list.