Beyond the dyad: uncovering higher-order structure within cohesive animal groups
Revealing the consequences of social structure in animal societies is largely determined by our ability to accurately estimate functionally relevant patterns of social contact among individuals. Of particular relevance are social contacts that drive and maintain the cohesion of moving animal groups. To date, studies have predominantly built up social structure from dyadic connections, which while effective in open societies--where groups are ephemeral--may not be sufficient to characterise the fine-grained structure within more cohesive animal groups. This is because associations or interactions can involve more than two individuals participating together, which current approaches cannot distinguish from independent sets of dyadic connections. Here we apply higher-order temporal network approaches to high-resolution GPS data from every group member in two cohesive groups of vulturine guineafowl (Acryllium vulturinum). By quantifying moment-by-moment association dynamics, we reveal clear sex-biased contributions to the group cohesion. Specifically, males form the cohesive core of the group as they participate in temporally consistent sub-groups and tend to occupy forward positions when in movement. Females instead remain peripheral and are more likely to leave sub-groups, while also occupying rear positions in moving sub-groups. These results reveal how the cohesion among males, which were previously found to be more likely to lead group movements, allows them to more often form a majority, confirming that self-organisation within the group can drive leadership patterns independently of dominance. Our study thus demonstrates that sub-group association dynamics derived from high-resolution GPS data can provide insights in how the fine-scale spatial and social organisation of cohesive groups, and their temporal dynamics, can explain key processes like leadership.