Emperor penguins may dominate Antarctica now, but even they had trouble during the last ice age. A new study is out this week and suggests just three populations may have survived during the last ice age.

Emperor penguins are known for their hardiness against Antarctica’s frigid cold. Temperatures regularly drop to -30 degrees Celsius. Yet, the emperor penguins have no trouble breeding during the cold winters.

The penguins can handle the cold, so why were only three populations able to survive?

Gemma Clucas, one of the lead authors of the paper, explains: “Due to there being about twice as much sea ice during the last ice age, the penguins were unable to breed in more than a few locations around Antarctica. The distances from the open ocean, where the penguins feed, to the stable sea ice, where they breed, was probably too far. The three populations that did manage to survive may have done so by breeding near to polynyas – areas of ocean that are kept free of sea ice by wind and currents.”

Researchers believe one of these three groups can be found today in the Ross Sea. Emperor penguins that breed here are genetically distinct from other emperor penguins across Antarctica.

While emperor penguins need ice sheets to breed on, access to open seas is a must for feeding.

Emperor penguins’ habitat is a delicate one. There needs to be a balance of sea ice and access to open seas for the penguins to flourish. A 2014 study from Woods Hole Oceanographic Institute says the entire population could fall by a third by the end of the century due to disappearing sea ice.

As the sea ice disappears, so does krill – a main food supply for emperor penguins.

Researchers believe climate change might affect the Ross Sea last compared to other regions in Antarctica. In fact, even with warmer temperatures around the globe, ice levels are increasing in the Ross Sea. Changes in wind patterns have led to increases in the extent of winter sea ice over the last few decades. But, this trend is expected to reverse by the end of the century.

Dr Tom Hart, who helped organize the study, said, “It is interesting that the Ross Sea emerges as a distinct population and a refuge for the species. It adds to the argument that the Ross Sea might need special protection.”

Image credit: Paul Nicklen/National Geographic

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