Influence of individuality in collective movements: an experimental approach in domestic horses (#649)
In many social species, moving together is essential to maintain group cohesion. Social groups being generally composed of individuals differing in many aspects (e.g. personality, social status), what could be the influence of individuality in collective decision-making? In domestic horses, studies showed that different group members can initiate collective displacements, discrediting the myth of “unique leader”. However, some horses appear to exert higher social influence, i.e. are more followed. We collected data in 2 groups of 6 mares to characterise individual levels of success based on initiations of movement expressed by each horse. We are especially interested about the group’s reaction to initiations (e.g. number of followers) that could enable us to determine an average success level per initiator. The innovative aspect here is that we aim to compare success levels between spontaneous and experimental contexts. Spontaneous initiations are evaluated within the observation of horses in their pasture (50h/group). Induced initiations are experimentally provoked within a protocol where only the tested horse is informed of the location of hidden food (4 initiations/horse). Experimental approach has two main assets since it allows 1/ inducing initiations in all horses even though some of them do not initiate spontaneously; 2/ limiting the possibility of the initiator’s recruitment (no pre-departure period) and thus focusing only on the influence of the initiator’s identity on its success. Comparing success levels between spontaneous and experimental contexts will allow us to settle between two hypotheses. If the initiator’s identity plays a major role in its success, success levels should be similar between spontaneous and experimental contexts. On the contrary, if other mechanisms are significantly involved, success levels should differ between contexts. Developing such an experimental approach in complex groups of mammals opens up new perspectives to determine which factors, either individual or anonymous, are determinant for moving collectively.