COS 59-5
To follow or not? How animals in fusion-fission societies handle conflicting information during group decision-making
The evolutionary context underpinning movement decisions made by group-living animals is central to understanding socioecology and animal distribution patterns. When group members possess differing information about the environment, they may disagree on the best movement decision. Such conflicts jeopardize group cohesion, and are therefore a fundamental driver of fusion-fission group dynamics. Yet, the current paucity of empirical work hampers our understanding of how adaptive evolution has shaped plasticity in collective behaviors that promote and maintain fusion-fission dynamics. Our objectives were to 1) evaluate the role of individual knowledge during collective patch choice decisions, 2) determine under what circumstances animals might favor following, versus leaving the group, in situations where group member knowledge is conflicting, and 3) quantify the impact that following other group members to new places has on the spatial distribution of individuals. We examined these objectives using GPS radio-collar data collected between 2006 and 2014 from of 22 free-ranging plains bison (Bison bison bison) residing in Prince Albert National Park (Canada).
Results/Conclusions
We first establish a conceptual framework for understanding how personal information and other indirect conditions affect group membership during collective patch choice decisions, and how such processes ultimately influence animal distribution. Then, we demonstrate that through fusion-fission events bison are constantly associating with conspecifics possessing different spatial information, and this renewed information is key to consensus decision-making. Bison used group familiarity coupled with their knowledge of local foraging options and recent sampling experience of resource quality when deciding to follow or leave a group during conflict situations – a tactic that led to energy-rewarding movements. These results provide empirical evidence of an adaptive behavioral strategy for animals in fusion-fission societies to deal with conflict situations while simultaneously reducing uncertainty in energy intake rate. Finally, we demonstrate how the decision follow or leave a group during a given patch-to-patch movement plays a significant role in the annual home range size of a given individual. In conclusion, natural selection has shaped collective behaviors for coping with social conflicts and resource heterogeneity, which maintain fusion-fission dynamics and play an essential role in animal distribution.