The last ice age was too cold even for emperor penguins

A group of emperor penguins near the Gould Bay, Antarctic. Image: Dr Tom Hart

The Ross Sea in the Antarctica could have acted as a refuge for emperor penguins during the last ice age, scientists say.

A study of how changing climate has affected emperor penguins over the last 30,000 years has found that only three populations may have survived in isolated colonies during the last ice age.

Researchers from the Universities of Tasmania, Southampton, Oxford and the Australian Antarctic Division examined the genetic diversity of modern and ancient emperor penguin populations in Antarctica to estimate how they had been changing over time.

Emperor penguins are highly cold-adapted, reliant on sea ice and vulnerable to climate change. The species breeds on sea ice during the Antarctic winter when temperatures can fall below -30°C.

However, the research found that conditions were too harsh even for emperor penguins during the last ice age.

The population then was roughly seven times smaller than today and split into three populations. And in the last 12,000 years the population increased as sea ice decreased.

The research, published today in the journal Global Change Biology, was jointly led by Jane Younger, a PhD student from the University of Tasmania’s Institute for Marine and Antarctic Studies and Gemma Clucas, a PhD student from Ocean & Earth Sciences at the University of Southampton.

Their research shows emperor penguin colonies spanning 8,000 kms of coastline are interbreeding, suggesting they migrate much farther around Antarctica than previously thought.

During the last ice age the three populations which managed to survive may have done so by breeding near polynyas, areas of ocean that are kept free of sea ice by wind and currents.

One of these polynyas was probably in the Ross Sea. The emperor penguins there today are genetically distinct from other emperor penguins around Antarctica.

University of Tasmania project leader, Dr Karen Miller, says emperor penguins in the Ross Sea do not interbreed with penguins from elsewhere. This is puzzling as there are no clear barriers isolating the Ross Sea colonies.

“It’s clear that the Ross Sea has been an important area for emperor penguins in the past and is likely to be in the future,” she says. “This alone emphasises the need for careful protection of this important part of the Antarctic ecosystem.”

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