Compromise Between Individual Rationality and Collective Rationality in Decision-Making in Schistocerca Gregaria (The Desert Locust)

Overview & Synopsis

Animals living in groups interact with their environment and base their decision-making on the reliability of information sources such as the "personal information" and the "social information". As such, we studied the manner in which the information choice is made, within a simple nonsocial animal model, by assessing the compromise between individual and collective rationality in decision-making in the Desert Locust Schistocerca gregaria during the appearance of a predator. We analyzed the relationship between response times (jumping and freeze), the quality of required personal information as a function of group size and we checked the relationship between the choice of use of information (personal vs. social) and arrangement of locusts. Results show that, in small groups, locusts behave by individual rationality and use personal information regardless of its quality. As the group expands, and when personal information is sketchy, locusts tend to share information and behave by collective rationality. However, when personal information is accurate locusts tend again to avoid sharing information adopting an individual rationality. This observed effect is due to the quality of required personal information and access to the information through congestion and distance between conspecifics. Results underline a recurrent individual rationality in locusts in decision-making. Furthermore, the strong adaptation capacity of this insect could lead to a collective rationality in large groups when the required personal information is imprecise, unreliable, or difficult to access, to provide streamlined decision-making.