Upwind flight partially explains the migratory routes of locust swarms
2024
Sorel, Maeva | Gay, Pierre-Emmanuel | Vernier, Camille | Cissé, Sory | Piou, Cyril | Centre de Biologie pour la Gestion des Populations (UMR CBGP) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [Occitanie])-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro Montpellier ; Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Montpellier (UM) | Département Systèmes Biologiques (Cirad-BIOS) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad) | Centre National de Lutte contre le Criquet pèlerin ; Partenaires INRAE | MESO@LR-Platform, University of Montpellier, France | ANR-18-CE32-0010,PEPPER,Etude de l'émergence du polyphénisme de phase et des risques associés(2018)
International audience
Show more [+] Less [-]English. To be efficient, locust swarm control must focus on the place where eggs are laid and hopper bands may appear. But swarms travel a lot and among all the places likely to host them, there is a need to predict to which exactly they will fly. It is then essential to consider movement dynamics to anticipate any displacement that may lead to a further reproduction of locust swarms. Swarms mostly fly downwind and sometimes upwind. We designed an agent-based model to explore swarm displacements depending on the direction of the wind and the possibility for the swarms to realise upwind flights. A primary objective was to assess how upwind flights can improve the replicationand predictionof documented migratory paths. We looked at the effects of using upwind flight on the swarm ratio arriving in expected (i.e. historically known) areas. Our simulations clearly showed that using upwind flight helped for a better replication of Schistocerca gregaria migrations than not using upwind flight. Not using upwind flight reduced swarm dispersion and reduced the range of migrations. Hence, prevailing winds alone cannot explain locust swarm migrations. Food intake must also be considered to regulate movement dynamics and vegetated areas seem to be more attractive to locusts than expected. Our simulations did not perfectly reproduce the general patterns of migrations in some scenarios, but this invites further investigations and the use of other types of field data to calibrate the model. Nonetheless, our results highlighted the importance of upwind flight and showed the major role of wind and temperature on swarm displacement.
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