2014/10/14 by Alessandro Attanasi, Andrea Cavagna, Lorenzo Del Castello +7
Biochemistry, Genetics and Molecular Biology · Computer Science · Physics and Astronomy · #ALARM #Alarm signal #Animal Vocal Communication and Behavior #Biological dispersal #Collective behavior #Collective motion #Diffusion and Search Dynamics #Distributed Control Multi-Agent Systems #Flock #Flocking (texture) #Starling #cond-mat.stat-mech #physics.bio-ph #q-bio.PE
paper · pdf · doi:10.1098/rsif.2015.0319
published as Journal of The Royal Society Interface 12 (108), 20150319 (2015) · 18 pages, 2 Videos added
arxiv created 2014/10/14 · openalex publication_date 2015/07/01 · arxiv updated 2016/03/31 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
One of the most impressive features of moving animal groups is their ability to perform sudden coherent changes in travel direction. While this collective decision can be a response to an external alarm cue, directional switching can also emerge from the intrinsic fluctuations in individual behaviour. However, the cause and the mechanism by which such collective changes of direction occur are not fully understood yet. Here, we present an experimental study of spontaneous collective turns in natural flocks of starlings. We employ a recently developed tracking algorithm to reconstruct three-dimensional trajectories of each individual bird in the flock for the whole duration of a turning event. Our approach enables us to analyse changes in the individual behaviour of every group member and reveal the emergent dynamics of turning. We show that spontaneous turns start from individuals located at the elongated tips of the flocks, and then propagate through the group. We find that birds on the tips deviate from the mean direction of motion much more frequently than other individuals, indicating that persistent localized fluctuations are the crucial ingredient for triggering a collective directional change. Finally, we quantitatively verify that birds follow equal-radius paths during turning, the effects of which are a change of the flock's orientation and a redistribution of individual locations in the group.