Tuning regimes in ant foraging dynamics depend on the existence of bistability

Characterizing how behavior must be tuned to produce useful coordination is key to understanding the evolution and regulation of collective behavior. While computational models can answer this question for specific instances, recurring patterns in model dynamics hint at a more general means of classifying collective dynamics. Using ant foraging models as a foundational example, we investigate mechanisms that can produce symmetry-breaking transitions to bistability as a first basic classification of collective behavior. Collective transitions are functionally important: They lead to sudden changes in collective states, enhanced sensitivity to environmental inputs, and hysteresis. We use bifurcation theory to argue that the point at which discontinuous transitions merge at a continuous transition forms a codimension-2 bifurcation with universal properties, and that this point is functionally equivalent to the critical point of a phase diagram. We show how analogous bistable transitions appear across models of ant foraging with different mechanistic assumptions, and we explore how biologically relevant collective effects play out near the transition. This framework clarifies the difficulty of tuning collective behavior: locating a continuous transition typically requires tuning two parameters, while a discontinuous transition requires tuning only one. Finally, we explore conditions that degrade or destroy bistable transitions: heterogeneity blurs the transitions, while recruitment mechanisms that do not create a positive feedback loop do not display bistability at all.