title: Coordinated movements prevent jamming in an Emperor penguin huddle.
abstract: 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.
authors.affiliation: Department of Physics, University of Erlangen-Nuremberg, Erlangen, Germany. daniel.p.zitterbart@physik.uni-erlangen.de
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Zitterbart
authors.forename: Barbara
authors.initials: B
authors.lastname: Wienecke
authors.forename: James P
authors.initials: JP
authors.lastname: Butler
authors.forename: Ben
authors.initials: B
authors.lastname: Fabry
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D008956:Models, Chemical; D009068:Movement; D046429:Spheniscidae / Q000502:physiology*; D013997:Time Factors