Intermittent collective dynamics emerge from conflicting imperatives in sheep herds

Francesco Ginelli, Fernando Peruani, Marie-Helene Pillot, Hugues Chate, Guy Theraulaz, Richard Bon

Research output: Contribution to journalArticle

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Abstract

Among the many fascinating examples of collective behavior exhibited by animal groups, some species are known to alternate slow group dispersion in space with rapid aggregation phenomena induced by a sudden behavioral shift at the individual level. We study this phenomenon quantitatively in large groups of grazing Merino sheep under controlled experimental conditions. Our analysis reveals strongly intermittent collective dynamics consisting of fast, avalanche-like regrouping events distributed on all experimentally accessible scales. As a proof of principle, we introduce an agent-based model with individual behavioral shifts, which we show to account faithfully for all collective properties observed. This offers, in turn, an insight on the individual stimulus/response functions that can generate such intermittent behavior. In particular, the intensity of sheep allelomimetic behavior plays a key role in the group’s ability to increase the per capita grazing surface while minimizing the time needed to regroup into a tightly packed configuration. We conclude that the emergent behavior reported probably arises from the necessity to balance two conflicting imperatives: (i) the exploration of foraging space by individuals and (ii) the protection from predators offered by being part of large, cohesive groups. We discuss our results in the context of the current debate about criticality in biology.
Original languageEnglish
Pages (from-to)12729–12734
Number of pages6
JournalPNAS
Volume112
Issue number41
Early online date28 Sep 2015
DOIs
Publication statusPublished - 2015

Fingerprint

sheep
grazing
predators
shift
biology
stimuli
avalanches
animals
configurations

Keywords

  • sheep herds
  • collective behavior
  • self-organisation
  • computational modelling
  • allelomimetism

Cite this

Ginelli, F., Peruani, F., Pillot, M-H., Chate, H., Theraulaz, G., & Bon, R. (2015). Intermittent collective dynamics emerge from conflicting imperatives in sheep herds. PNAS, 112(41), 12729–12734. https://doi.org/10.1073/pnas.1503749112

Intermittent collective dynamics emerge from conflicting imperatives in sheep herds. / Ginelli, Francesco; Peruani, Fernando; Pillot, Marie-Helene; Chate, Hugues; Theraulaz, Guy; Bon, Richard .

In: PNAS, Vol. 112, No. 41, 2015, p. 12729–12734.

Research output: Contribution to journalArticle

Ginelli, F, Peruani, F, Pillot, M-H, Chate, H, Theraulaz, G & Bon, R 2015, 'Intermittent collective dynamics emerge from conflicting imperatives in sheep herds', PNAS, vol. 112, no. 41, pp. 12729–12734. https://doi.org/10.1073/pnas.1503749112
Ginelli F, Peruani F, Pillot M-H, Chate H, Theraulaz G, Bon R. Intermittent collective dynamics emerge from conflicting imperatives in sheep herds. PNAS. 2015;112(41):12729–12734. https://doi.org/10.1073/pnas.1503749112
Ginelli, Francesco ; Peruani, Fernando ; Pillot, Marie-Helene ; Chate, Hugues ; Theraulaz, Guy ; Bon, Richard . / Intermittent collective dynamics emerge from conflicting imperatives in sheep herds. In: PNAS. 2015 ; Vol. 112, No. 41. pp. 12729–12734.
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