Habitat Geometry and the Development of Social Phenotypes in the Desert Locust

Desert locusts can shift between solitarious and gregarious phenotypes in response to changes in their social and physical environment. While crowding is known to drive this remarkable behavioural plasticity, less is understood about how the spatial structure of the environment itself contributes to the development of social behaviour. In my PhD, I investigated this by raising locusts in semi-natural environments where food and roosting resources were either concentrated in one location or distributed throughout the habitat. Using long-term population monitoring, individual and group behavioural assays, I followed how differences in social affinity emerged over development.

We found that habitat structure alone was sufficient to produce lasting differences in social behavior. Locusts developing around clumped resources showed stronger social affinity and a greater tendency towards coordinated collective movement, while those raised with distributed resources developed more solitarious-like behavioural characteristics. These behavioural differences were accompanied by a relatively focused set of changes in brain gene expression, including genes associated with neuromodulatory, metabolic and juvenile-hormone-related processes. Together, the findings show how the spatial organization of an animal’s environment can shape social experience over time, linking habitat structure to behavioural plasticity at both the collective and molecular levels.