Superefficient teamwork in weaver ants.

Abstract

Teamwork is often assumed to enhance group performance, particularly for physical tasks. However, in both human and non-human animal teams, the effort contributed by each member may, in fact, decrease as team size grows. This counterintuitive phenomenon, known as the Ringelmann effect,¹ is generally ascribed to poor coordination or differences in motivation.^2,3 Weaver ants (Oecophylla smaragdina) display some of the most impressive feats of teamwork in the natural world,^4,5 including self-assembly into pulling teams that fold leaves into nesting chambers.^6,7 Here, we investigated whether weaver ant pulling teams suffer from the Ringelmann effect by measuring the force that weaver ant teams of varying sizes produce during nest construction. The average force contribution per individual almost doubled as team size increased, demonstrating that weaver ants not only avoid the Ringelmann effect but achieve the opposite-they are "superefficient" team workers.^8,9,10 We propose that this superefficiency is facilitated by a division of labor within teams: "active pullers" work together to generate a pulling force that is stored in chains of "passive resisters," which capitalize on the remarkable frictional strength of weaver ant attachment organs; weaver ant teams thereby act as a "force ratchet." Our results highlight a novel mechanism of teamwork in a highly coordinated natural system and may inspire optimization algorithms for superefficient teams in distributed artificial systems, including swarm robotics. VIDEO ABSTRACT.