Drone Observation for the Quantitative Study of Complex Multilevel Societies

SIMPLE SUMMARY: Multilevel societies are the most complex social structures in animals. They are social structures with nested levels of social organization, where stable “core units” gather to form higher-level groups. Such multiple-unit groups usually become very large (usually 100–1000 individuals), making it difficult to conduct observations. Most previous studies lack numerical definitions and descriptions; thus, it is largely unknown how and why animals, including humans, form multilevel societies. Aerial observation from unmanned aerial vehicles (drones) is a powerful method of capturing the spatial structures and movements of large animal groups. Recent advances in drone technology and its application have led to new discoveries, such as the spatial structure of multiunit groups and the underlying mechanisms of collective behavior. We review how previous studies have utilized drones and how drone applications have contributed to the understanding of multilevel societies. We will further discuss the potential opportunities and challenges with regard to drone observations in future studies. ABSTRACT: Unmanned aerial vehicles (drones) have recently been used in various behavioral ecology studies. However, their application has been limited to single groups, and most studies have not implemented individual identification. A multilevel society refers to a social structure in which small stable “core units” gather and make a larger, multiple-unit group. Here, we introduce recent applications of drone technology and individual identification to complex social structures involving multiple groups, such as multilevel societies. Drones made it possible to obtain the identification, accurate positioning, or movement of more than a hundred individuals in a multilevel social group. In addition, in multilevel social groups, drones facilitate the observation of heterogeneous spatial positioning patterns and mechanisms of behavioral propagation, which are different from those in a single-level group. Such findings may contribute to the quantitative definition and assessment of multilevel societies and enhance our understanding of mechanisms of multiple group aggregation. The application of drones to various species may resolve various questions related to multilevel societies.