Ant Cooperative Transport of Large Flexible Objects under Constraint

Collective behavior in animal groups is affected by local interactions, external constraints, and an influx of information. In the context of cooperative transport of food items by a group of ants, it was shown that a trade-off exists between the well-coordinated pull of uninformed individuals and the directional information brought in by informed leaders. The ants were modeled as binary Ising spins, representing the two roles – pullers and lifters - they perform during the transport of solid objects. The assumption of solid objects implies perfect communication with zero delays. Here, we test the existing model by allowing a group of ants to collectively transport a large flexible food item constrained at one end and free at the other. Constraining the system causes it to behave not only like a non-linear pendulum but also like a soft beam that bends due to the ants' pulling forces. The bending rigidity of the system interferes with the macroscopic dynamics of the mechanically coupled ants, delaying their force-sensing capability, and thus breaking coordination while constraining communication. Therefore, we question the validity of the existing model for the case of a large soft object and study how ants still manage efficient transport despite limited communication.