Emperor penguins live in the coldest of cold climates on planet Earth, enduring wind chills that reach -60° Celsius (-76° Fahrenheit). Their black feathers can help them absorb the sun’s heat and the blubber in their bodies helps insulate them, but there’s nothing that replaces a good penguin huddle.

The center of a penguin huddle, a form of social thermoregulation, can reach temperatures of up to 37° Celcius (98.6° Fahrenheit). It’s so warm that the center penguins keep moving through the huddle so that they don’t overheat, while penguins on the outside move inward to get warm.

Liz Bonnin demonstrates the power of this tightly-knit swarm with a huddle of hot chocolates in the snow. A thermal imaging camera illuminates what’s going on.

Biologists and physicists from Germany’s University of Erlangen-Nuremberg created mathematical models from time-lapse camera footage of these ever-shifting huddles. From Live Science in 2013:

“Maintaining a massive huddle of thousands of penguins may sound fairly simple, but sticking together in a pack so large turns out to be quite complicated: When one penguin moves a single step, the rest must also move to accommodate the open space and stay warm. In this particular species of penguin, males play the unusual gender role of incubating eggs, so it is especially crucial that they maintain warmth during cold winters…

The team’s mathematical models showed that the huddles behave as waves instigated by any individual in the pack, no matter that individual’s location. If two waves travel toward each other, they merge, rather than passing one another. Gaps just 2 centimeters wide (0.8 inches) appear to instigate a reorganization, in order for the penguins to stay warm.”

Related reading: How Emperor Penguins Survive Antarctica’s Subzero Cold and more about temperature regulation strategies.

Related videos to watch next:
• Emperor Penguins keep warm in an ever-shifting huddle.
• Emperor Penguins Speed Launch Out of the Water.
• The Arctic vs. the Antarctic.