Socially driven negative feedback regulates activity and energy use in ant colonies

Despite almost a century of research on energetics in biological systems, we still cannot explain energy regulation in social groups, like ant colonies. How do individuals regulate their collective activity without a centralized control system? What is the role of social interactions in distributing the workload amongst group members? And how does the group save energy by avoiding being constantly active? We offer new insight into these questions by studying an intuitive compartmental model, calibrated with and compared to data on ant colonies. The model describes a previously unexplored balance between positive and negative social feedback driven by individual activity: when activity levels are low, the presence of active individuals stimulates inactive individuals to start working; when activity levels are high, however, active individuals inhibit each other, effectively capping the proportion of active individuals at any one time. Through the analysis of the system’s stability, we demonstrate that this balance results in energetic spending at the group level growing proportionally slower than the group size. Our finding is reminiscent of Kleiber’s law of metabolic scaling in unitary organisms and highlights the critical role of social interactions in driving the collective energetic efficiency of group-living organisms.Author summary: Similarly to how larger organisms use less energy per unit mass than smaller ones, eusocial insects like ant colonies become more energy efficient as colony size increases. The mechanism underneath this efficiency remains a mystery. Here, we seek to uncover its origin in socially contagious “deactivation”, which runs counter to more conventional ideas of excitatory social interactions. Beyond providing insight into the collective behavior of highly integrated social groups, our findings on activity regulation open the door to the design of engineered multi-agent systems, like robotic swarms or active matter, which may achieve efficient performance in both function and energy use.