Whole group tracking reveals that relatedness drives consistent subgrouping patterns in white-nosed coatis

The formation of subgroups can allow group-living animals flexibility to balance the costs and benefits of sociality over time. Subgrouping dynamics emerge from individual decisions about whether and with whom to maintain cohesion, with these decisions potentially influenced by ecological, physiological and social factors. We GPS-tracked the movements of nearly all members of three wild white-nosed coati, Nasua narica, social groups that differed in their demographic profiles to better understand how these highly social, frugivorous carnivores weight the relative importance of these different factors in their grouping decisions. Quantifying group movements and subgrouping patterns, we found that two of the three groups we tracked exhibited fission–fusion behaviours, with groups splitting into subgroups that persisted over varying time spans from minutes to days. In contrast, the third group remained together across the entire observation period. When groups split, they did not do so randomly; instead, individuals tended to form subgroups with the same individuals consistently over time. Assessing the drivers of subgrouping patterns revealed that subgroup membership was associated with genetic relatedness, but not physiological similarity as quantified by age and sex homophily. Our results demonstrate great variation in subgrouping patterns within a single species, while also highlighting a consistent role of relatedness in driving social preferences when subgroups form.