A model-based approach to study ant energetics from trajectory data

Whether an insect belongs to a solitary or a social species, its survival depends on how it consumes available energy resources. The characterization of energy consumption has largely relied on flow respirometry, a technique that is difficult to implement on individuals in isolation and is ill-conceived to disaggregate energy costs among individuals in a colony. Toward addressing these issues, we introduce an integrative framework that combines the growing area of video tracking with rigorous biomechanical modeling to infer locomotion energetics in ants. Our approach rests upon a novel physics-based model for hexapedal locomotion in the sagittal plane, which predicts forward motion and vertical oscillations in terms of few model parameters that can be retrieved from the literature or mathematically constrained. We show that individual ants favor adaptability over energy efficiency by incorporating higher step frequencies and rely less on energy recovery. A mechanistic approach to input energy estimation, combined with biomechanical analysis, provides a valuable toolkit for biologists to investigate ant energetics and perform informative inter-species comparison, from trajectory data.