During the extreme cold of the Antarctic winter, male Emperor Penguins balance their single egg on top of their feet to keep it from touching the icy ground. And to survive the -35ºF or colder temperatures and 120-mph winds, the birds form tight huddles with thousands of individuals.
To maintain the huddles, the birds make stop-and-go movements like cars in a traffic jam, according to a new study.
By using a mathematical model that recreated the positions, movements, and interactions of individual penguins in a huddle, researchers have revealed that a single bird needs to move only two centimeters in any direction for its neighbor to react and also take a step to stay close to it.
The movements then flow through the entire huddle like a travelling wave. The wave keeps the huddle as dense as possible to protect the penguins from the cold, and it helps smaller huddles merge into larger ones.
Researchers from Germany and France published the study today in the Institute of Physics and German Physical Society’s New Journal of Physics. A previous study by the same research team showed that huddled penguins move every 30-60 seconds.
Here’s a time-lapse video from the scientists showing penguins in a moving huddle:
The researchers used a mathematical model, which has previously been used to study traffic jams, and compared the results with an analysis of video recordings of a real-life penguin huddle.
Unlike a traffic jam, the researchers found that the waves of movements in a huddle can originate from any bird and can propagate in any direction as soon as a sufficient gap, known as a “threshold distance,” develops between two penguins.
The threshold distance was estimated to be around two centimeters, which is twice the thickness of a penguin’s compressive feather layer, suggesting the penguins touch each other only slightly when standing in a huddle without compressing the feather layer. The birds therefore maximize huddle density without compromising their own insulation.
“We were really surprised that a travelling wave can be triggered by any penguin in a huddle, rather than penguins on the outside trying to push in,” says researcher Daniel Zitterbart of the Alfred Wegener Institute at the Helmholtz Centre for Polar and Marine Research. “We also found it amazing how two waves, if triggered shortly after each other, merged instead of passing one another, making sure the huddle remains compact.” — Matt Mendenhall, Managing Editor