Scientists have discovered that emperor penguins survive Antarctic conditions by huddling together in their thousands and making coordinated steps too small to see with the naked eye.
The steps, taken every 30 to 60 seconds, travel as a wave through the entire group and, over time, lead to large-scale reorganisation of the whole colony. This allows outlying birds to move inside the huddle and warm up.
The effect is similar to what occurs when dough is kneaded.
Dr Daniel Zitterbart, from the University of Erlangen-Nuremberg in Germany, and colleagues described penguins packed in a huddle so tightly that individual movements become impossible.
However, the huddle structure is continuously reorganised to give each penguin a chance to move inside the huddle and warm up.
The penguins were filmed during a winter at Dronning Maud Land in the Antarctic.
Dr Zitterbart is now developing a remote-controlled observatory to study penguins all year round.