Collective decision making during group movements in European bison, Bison bonasus
Résumé
Group coordination and the synchronization of activities are essential to maintain group cohesion during
collective movements. Collective decisions arising from this synchronization are influenced by both
ecological and sociodemographic factors. The spatial heterogeneity and temporal predictability of resources
not only affect fissionefusion dynamics and patterns of movement, but also influence leadership
processes. However, herd movements may also be affected by the propensity of certain individuals to
initiate movements through individual characteristics such as sex and dominance. In this study, we
examined how members of a European bison herd living in fissionefusion dynamics decide to move, and
how they synchronize their nonforaging movements. Adult females appeared to initiate the majority of
movements, while juveniles rarely did so. The number of followers for a collective movement was
directly influenced by the sex and age of the initiator. Other factors also influenced the number of followers,
such as the orientation and dispersion state of the herd. The initiator was more likely to be
followed if it went in the direction indicated by the majority of individuals, suggesting a voting process.
Subgroups of individuals joined movements using a mimetic process, confirming the fissionefusion
dynamics of this species. The results of this study put a new slant on our understanding of the ecology
and sociality of the European bison. In view of recent conservation studies suggesting that human
ewildlife conflict could be avoided by controlling animal groups and particularly their leaders, our study
could be an effective tool in the management of this species after reintroduction.