Emperor penguins spotted breeding on ice shelves for the first time

For the first time, a team of scientists has discovered Emperor penguins breeding on ice shelves in Antarctica where previously they were believed only to breed on much lower ice that floats on the ocean surface.

The members of the research team were from the British Antarctic Survey, the Australian Antarctic Division and the Scripps Institution of Oceanography at the University of California, San Diego.

In a report in the journal PLOS ONE the researchers say it is not clear whether the penguins are climbing onto the shelf ice because of a lack of their preferred sea ice, and if the behaviour will ultimately offer them a safe haven from climate change.

Satellite and aerial images revealed four colonies of the birds breeding on ice shelves that are formed by glaciers that flow over land towards the coast at a range of Antarctic locations. Two of the colonies have only been seen on shelf ice whereas the other two moved between sea and shelf ice from year to year.

The discovery is a surprise because Emperor penguins – which are up to 1.15 metres tall and can weigh 40 kilograms – were thought to be too clumsy to climb onto ice shelves that can tower up to 30 metres above the sea ice below.

One of the researchers, Dr Barbara Wienecke of the Australian Antarctic Division, says the penguins mainly climbed onto ice shelves that sloped more gently as a result of snowfall or weathering of old ice faces.

“Rather than having a steep, clean-cut cliff you have sometimes a rather gently sloping hill. They are certainly not able to climb up a 30-metre sheer cliff,” Wienecke says.

The scientists say the behaviour was first spotted in 2009 but that it is not yet certain if the discovery is genuinely new or has just never been noticed until now. Observations made so far suggest the two colonies that switched between sea ice and shelf ice did so in breeding years when the sea ice formed late.

Emperor penguins breed during the Antarctic winter and their chicks fledge the following summer. From April to December they need smooth, flat ice that is anchored to the shore to prevent floating away, with ready access to open water for catching fish. Males also need to eat snow to stay hydrated during the long months incubating their young.

“If the sea ice is insufficient to maintain the colony they have two choices: either they find an alternative or they just don’t breed at all,” Wienecke says.

It is possible, however, that the penguins could find themselves stranded if the gently sloping section breaks away to form an iceberg – leaving them literally high and dry with no food or water.

The Emperor penguin is listed as “near threatened” and some estimates predict its numbers will halve by the middle of this century as the sea ice recedes. The researchers say it is also not known if the penguins can take refuge on ice shelves as climate change takes hold, or whether they will have to retreat to higher-latitude coastlines such as the Ross Sea.

The newly observed colonies are modest in size, with between 3000 and 3800 adults. But the largest traditional colonies can number up to 40,000 adult penguins.

“I am really not quite sure what is going to happen to them, but I dare say that it is a species that is still very much under strife,” Wienecke says.