Time lapse shows how penguins huddle
1 June 2011 Last updated at 23:28 BST
The mystery of how penguins stay warm while they huddle has been revealed by an international team of scientists.
Emperor penguins survive the tough Antarctic winters by forming tightly packed clusters - but scientists thought they were so tightly packed any movement would be impossible.
Now time lapse video shows the birds move in almost imperceptible waves through the group, which, over time, drastically changes its structure - and allows some of the unlucky penguins on the outside a chance to get closer to the cosy centre.
The study appears in Plos One, a journal published by the Public Library of Science.