Human disturbance impacts on wildlife sociality and group sizes

Human disturbances affect multiple aspects of wildlife ecology, including occupancy, density, and activity patterns. Animals also adjust their sociality, such as grouping behaviours, to adapt to humans and their disturbances. However, while animal sociality has been extensively studied from evolutionary perspectives, the role of humans has received less attention, particularly how responses vary across taxa and disturbance contexts. Here, for terrestrial mammals, we first conducted a systematic review comparing group sizes across different levels of human disturbances. Our synthesis encompassed 215 observations from 151 studies, covering 129 species and eight disturbance types. A meta-analysis of 71 effect sizes revealed that human disturbances reduced group size by an average of 14%, although responses were highly variable. We then developed a conceptual framework that outlines the pathways and mediators through which humans influence group size, including the interplay of species traits, habitat characteristics, and local human behaviours. This framework offers broad applicability for understanding the complex relationships between human disturbance and wildlife sociality. By integrating empirical evidence with conceptual synthesis, our work highlights the need to consider social dynamics in conservation and provides a foundation for future studies across mammals and other taxa.