The Neuroethology of Collective Decision-Making in the Desert Locust

Central to the formation of devastating locust swarms is crowding-induced plasticity, with social phenotypes swiftly changing from cryptic (solitarious) to swarming (gregarious). Such rapid density-dependent adaptations raise critical questions about neural processing in variable social environments, information use, and context-dependent decision-making. Across five chapters, my thesis combines various methods to show that locusts act as probabilistic decision-makers that combine different types of information to make decisions while on the move and during foraging.

In Chapter I (Günzel et al., 2023), behavioral assays and Bayesian modeling reveal that locusts effectively integrate private and social cues during foraging. Building on this, Chapters II-III (Petelski et al., 2024; Günzel et al., 2024) employ targeted functional calcium imaging to assess how these cues are processed, shedding light on sensory adaptations in changing social environments. Comparing neural activity in gregarious and solitarious animals, I found that synergistic interactions form the basis of a crowding-induced modulation of activity across the locust’s antennal lobe.

Next, Chapter IV (Sayin et al., 2025) describes sensory computations underlying directional decisions in moving swarms via a combination of field and virtual reality (VR) experiments that demonstrate how vision sustains marching coherence, best explained by a cognitive ring-attractor framework. Last, Chapter V (in prep.) offers preliminary electrophysiological and VR data indicating that looming-evoked and social cues jointly modulate escape responses, which propagate through the swarm as a complex contagion.

Overall, my work links neural adaptations to ecologically relevant behaviors, providing a general framework for sensory-guided social decision-making that extends well beyond locusts.