Adaptive Drosophila Olfactory Navigation Across Flow Regimes Suggests an Underlying Universal Search Strategy

Flying organisms must navigate a wide range of flow environments when searching for food or mates. While prior research has shown that Drosophila zig-zag in laminar flow and circle in still air, their behavior in turbulent or unsteady flows remains poorly understood, largely due to the difficulty of replicating naturalistic wind conditions in a wind tunnel. To address this, we developed a modular, multi-fan-array wind tunnel capable of generating shear layers and unsteady flow structures that mimic the directional variability found in nature. By pairing this setup with optogenetic stimulation, we can present flies with precise fictive odor cues, effectively decoupling odor encounters from wind dynamics and isolating the effect of flow structure on search behavior.

Our experimental data demonstrates that in unsteady flow conditions, trajectories become highly variable, resembling a stochastic hybrid of casting and circling. Taken together with prior research, our findings support the idea that fluid structure plays a significant role in free flight search strategies. Inspired by all observed search strategies across flow regimes, we propose a unifying model which is capable of generating the full spectrum of experimentally observed behaviors: casting in laminar wind, circling in still air, and more stochastic trajectories in unsteady flow. This framework offers a mechanistic explanation for how insects could adapt their olfactory search strategy seamlessly across environments.