For animals to remain in groups, they must be able to maintain cohesion, coordinate actions, and reach consensus about where to go next, despite extensive within-group heterogeneity. Theoretical models have long suggested that groups can solve these challenges through simple social movement rules, leading to shared (or ‘democratic’) decision-making. However, testing how group- and population-level outcomes—including shared decision-making—arise from collective behaviour has been challenging. Working with baboons and vulturine guineafowl, I used whole-group, high-resolution GPS tracking in the wild to simultaneously capture the movement of all group members. These data show that baboons and guineafowl exhibit almost identical properties in their collective decision-making. Scaling-up GPS tracking in vulturine guineafowl to the population-level further reveals that guineafowl live in a multilevel society: plural- and cooperatively-breeding social units form stable and cohesive groups, and groups interact preferentially with other groups both during the day and at communal roosts. Using these findings as a platform, I am presently building the foundations for studying ‘the ecology of collective behaviour’ that investigates the drivers and consequences of collective behaviour spanning from physiology to environmental change.