December 17, 2013
Staying Warm For Emperor Penguins Means Getting Into Traffic Jams
Lee Rannals for redOrbit.com - Your Universe Online
Researchers used mathematical models to recreate the positions, movements and interactions of individual penguins in a huddle, revealing that an individual penguin only needs to move less than an inch in any direction for its neighbor to react.
An individual penguin’s movements flow through the entire huddle like a traveling wave. This movement plays a vital role in keeping the huddle as dense as possible to protect the penguins from the cold while also helping smaller huddles merge into larger ones.
Previously, the same researchers studied time-lapse videos and showed how instead of remaining static, penguins in a huddle move every 30 to 60 seconds, causing all surrounding penguins to bump into them like stop-and-go movements in bumper-to-bumper traffic.
"Our previous study showed how penguins use traveling waves to allow movement in a densely packed huddle, but we had no explanation as to how these waves propagate and how they are triggered,” Daniel Zitterbart, co-author of the study from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), said in a statement.
The mathematical model used by the team had previously been used to study highway traffic jams. The team compared the results of the model with an analysis of video recordings of a real-life penguin huddle. They found the waves of movements in a penguin huddle can originate from any single penguin and can propagate in any direction as a sufficient gap, known as a “threshold distance.”
The threshold distance was estimated to be about 0.7-inch, which is twice the thickness of a penguin’s compressive feather layer. This finding suggests penguins touch each other only slightly when standing in a huddle without compressing the feather layer to help 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," said Zitterbart. "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."
Emperor penguins are the only vertebrate species that are able to breed during the severe conditions the Antarctic winter brings. During winter, temperatures can drop to as low as -58 degrees Fahrenheit, while wind can generate speeds up to 125 miles per hour.
Male penguins form dense huddles consisting of thousands of individuals to help maintain their body temperatures. These penguins are solely responsible for incubating their single egg during the winter, and they do so by covering it in an abdominal pouch above their feet while the female returns to the sea to feed.