Emperor penguins are known to thrive in the cold weather conditions of the Antarctic, but findings of a new study have revealed that even these highly cold-adapted flightless birds had difficulty surviving in the extreme condtions of the last ice age.

A group of researchers who looked at how climate change has impacted the Emperor penguins, the heaviest and the tallest of all species of penguins, over the past thousand years showed that only three populations of these flightless birds managed to survive during the last ice.

The conditions during the period were too harsh that the numbers of emperor penguins were reduced to about seven times less than their current number.

In a new study published in the journal Global Change Biology, Gemma Clucas, from the University of Southampton, and colleagues looked at the genetic diversity of the ancient and modern populations of emperor penguins in Antarctica to find out how they have been changing.

The researchers discovered that the conditions during the ice age were too extreme for the birds  with the last ice age being about 14 degrees colder than average.

The researchers said that the number of the birds likely dropped because there were less breeding locations and there were probably lesser number of prey that were available for them at the time. Clucas explained that the last ice age was marked by twice as much sea ice and this resulted in the penguins being able to breed in a limited number of locations around the region.  

Clucas likewise said that the distance between the breeding grounds of the penguins in the stable sea ice and the open ocean where they feed were also likely too far and that the three populations that survived may have bred near the polynyas, the areas in the ocean that were free from sea ice because of the currents and winds.

One of these was likely the Ross Sea as researchers have discovered that the emperor penguins that bred here are genetically unique from the other emperor penguins that thrive around Antarctica.

"We think the reason that they were able to survive there during the last ice age was that there was polynyas there," said study researcher Jane Younger, from the  Australian Institute for Marine and Antarctic Sciences. "So polynyas are areas within the sea ice that are kept free of ice by wind and currents so you have an area of open ocean and this is important for the penguins as they can use that to access the ocean for feeding."