Modelling Locust Foraging And Its Effect On Swarm Formation

Having plagued mankind for millennia, locust swarms continue to be a major threat to agriculture, effecting every continent except Antarctica and impacting the lives of 1 in 10 people. Locusts are short horned grasshoppers that exhibit two behaviour types depending on their local population density. These are; solitarious, where they will actively avoid other locusts, and gregarious, where they will actively seek them out. It is in this gregarious state that locusts can form massive and destructive swarms or plagues. These large scale group dynamics arise through simple individual and environment interactions. At longer time-scales, environmental conditions such as rain events synchronize locust lifecycles and can lead to repeated outbreaks. At shorter time-scales, changes in the distribution of food can have an effect on locust gregariazation. By modifying a multi-population aggregation equation to include locust-environment dynamics we are able to investigate the effect of different food distributions on locust swarming. Our results suggest that there is an optimal food width for locust swarm formation, and that as food becomes more densely packed gregarious locusts are able to outcompete their solitarious peers.