02 June 2011

The penguin huddle. How to stay warm, along with a wave.

The Public Library of Science's international, peer-reviewed, open-access, online publication PLoS ONE has reported that Emperor penguins behave collectively to stay warm.  In a huddle. Abstract
Daniel P. Zitterbart1,2*, Barbara Wienecke3, James P. Butler4,5, Ben Fabry1
1 Department of Physics, University of Erlangen-Nuremberg, Erlangen, Germany, 2 Alfred Wegener Institute for Polar and Marine Research (AWI), Bremerhaven, Germany, 3 Australian Antarctic Division, Kingston, Australia, 4 Molecular Integrative Physiological Sciences Program, Harvard School of Public Health, Boston, Massachusetts, United States of America, 5 Division of Sleep Medicine, Department of Medicine, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts, United States of America

For Emperor penguins (Aptenodytes forsteri), huddling is the key to survival during the Antarctic winter. Penguins in a huddle are packed so tightly that individual movements become impossible, reminiscent of a jamming transition in compacted colloids. 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. Here we show that Emperor penguins move collectively in a highly coordinated manner to ensure mobility while at the same time keeping the huddle packed. Every 30–60 seconds, all penguins make small steps that travel as a wave through the entire huddle. Over time, these small movements lead to large-scale reorganization of the huddle. Our data show that the dynamics of penguin huddling is governed by intermittency and approach to kinetic arrest in striking analogy with inert non-equilibrium systems, including soft glasses and colloids.

Editor: Matjaz Perc, University of Maribor, Slovenia
Received: March 22, 2011; Accepted: April 21, 2011; Published: June 1, 2011
Zitterbart DP, Wienecke B, Butler JP, Fabry B, 2011 Coordinated Movements Prevent Jamming in an Emperor Penguin Huddle. PLoS ONE 6(6):e20260.doi:10.1371/journal.pone.0020260
There is an art, or rather a science, to keeping warm in a huddle. The more the merrier.

See also BBC News report (with an excellent time-lapse video)

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