Using field data to test locust migratory band collective movement models.

Area of Science:

• Ecology
• Biophysics
• Animal Behavior

Background:

• Wingless locust nymphs form massive migratory bands.
• Coordinated movement in these bands arises from local interactions between individuals.

Purpose of the Study:

• To analyze the spatial distribution of locusts within natural bands.
• To infer the specific interaction rules governing individual locust movement using computer simulations.

Main Methods:

• Analysis of spatial distribution of locusts in naturally occurring bands.
• Comparison of empirical data with computer simulations using a 'zonal' self-propelled particles model.
• Utilizing neighbor density maps and pair correlation functions to identify interaction forces.

Main Results:

• Locusts display isotropic neighbor distribution, interacting with individuals in all directions.
• Evidence suggests a short-range repulsion force balanced by a clustering force (alignment/attraction) at approximately 3 cm.
• Simulations using various force combinations and interaction parameters yielded similar results, limiting precise rule determination.

Conclusions:

• Local interactions, characterized by short-range repulsion and clustering, are key to locust band coordination.
• The precise nature and range of these interaction rules remain difficult to pinpoint due to model degeneracy.
• Further research may be needed to refine models and fully elucidate the mechanisms of locust collective movement.