03 June 2011

Penguins make waves to keep warm

Emperor penguins in Antarctica.
Photo credit: StormPetrel1.
Some rights reserved.
ANTARCTICA - Penguin lovers are familiar with the images of male emperor penguins huddling together to survive the Antarctic winter while incubating their eggs. Outside the huddle, the temperature can drop below -50°C and gale-force winds can reach above 180 km/h, while inside the huddle, temperatures are above 0°C and can reach 37°C. But what has been discovered only recently is that penguins actually coordinate their movements to give all members of the huddle a chance to warm up.

The surprising finding was published by physicist Daniel Zitterbart from the University of Erlangen-Nuremberg, Germany, and his co-researchers biophysicist Ben Fabry from University of Erlangen-Nuremberg, physiologist James Butler Harvard University and marine biologist Barbara Wienecke from the Australian Antarctic Division on 1 June in the journal PLoS ONE.

The survival techniques of emperor penguins have long intrigued scientists. One unresolved question was how penguins move to the inside of a huddle when the birds stand packed so tightly that no movement seems possible.

"It is crucial, however, that the huddle structure is continuously reorganized to give each penguin a chance to spend sufficient time inside the huddle, compared with time spent on the periphery," the study authors wrote.

Zitterbart recently spent a winter at Dronning Maud Land in the Antarctic and made high-resolution video recordings of an emperor penguin colony that enabled the team to discover how penguins solve this problem. They found that the penguins moved together in coordinated periodic waves, movements which allow birds from the outside to enter the tightly packed huddle and warm up.

The time-lapse images were recorded every 1.3 seconds for a total of 4 hours, allowing the scientists to track the positions of hundreds of penguins in the colony. The periodic waves are invisible to the naked eye as they occur only every 30-60 seconds and travel with a speed of 12 cm/s through the huddle. Although small, over time they lead to large movements that are reminiscent of dough during kneading.

Zitterbart is currently developing a remote-controlled observatory to study penguins all year round. He hopes to witness the reversal of the dramatic decline in penguin colony sizes that is occurring in all areas of the Antarctic.

PLoS One citation

Zitterbart, D.P., Wienecke, B., Butler, J.P., Fabry, B. (2011) Coordinated movements prevent jamming in an emperor penguin huddle. PLoS ONE 6(6): e20260. doi:10.1371/journal.pone.0020260

Keeping warm: Coordinated movements in a penguin huddle, PLoS ONE, 1 June 2011, EurekAlert!

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