Ecology presentation – population dynamics and management of the Senegalese grasshopper: A modelling approach at the interface between nutritional ecology and landscape ecology

Locusts are among the most destructive pest for agriculture in the world. Oedaleus senegalensis, the Senegalese grasshopper can swarm and migrate long distances, causing serious crop damage and food security problems throughout the Sahel region. Contrary to the protein-limitation paradigm which stipulates that low N-concentration in plants impairs herbivores fitness, recent experimental studies have shown that the Senegalese grasshopper selects food with high carbohydrate content relative to protein. Hence, soil amendments can negatively impact the performance of this pest. However, the extent to which soil amendment linked with the nutritional ecology of individuals may influence the emergence of collective behaviors and shape population dynamics at a landscape scale remains unknown. We developed an agent-based model to describe the life-cycle and feeding behavior of this migratory species in a virtual landscape akin to Senegal. The model examined the effect of soil amendment on the spatial dynamics of the population while considering other sources of seasonal and latitudinal variability, such as predation, climate, vegetation availability and composition. Our results showed that when farmers practice soil amendment in more than half of millet fields, the pest selects less and damages less this type of crop. We showed that such model can provide evidence-based management strategies to support farmers in their decision-making and keep the pest below a critical density threshod.