Tall trails: ants resolve an asymmetry of information and capacity in collective maintenance of infrastructure

Information asymmetry is common in many aspects of natural and economic systems. Collective self-organized behaviour in social insects may involve asymmetries in which an individual may possess information but only another individual is able to act on it. We examined this phenomenon on foraging trails of leaf-cutting ants (Atta colombica) to determine whether workers can resolve such an asymmetry. Cleared trails facilitate the transfer of resources and information but require constant maintenance to remove obstacles that arise in a dynamic environment. Overhead obstructions, which occur frequently along trails, present a specific asymmetry for collective behaviours. Returning foragers carrying leaf fragments above their heads may be hindered by such obstructions but must rely on unladen workers to remove them. Can leaf-cutting ants resolve this asymmetry? Do they do so in an indiscriminate or discriminate fashion? We created experimental overhead obstructions that hindered laden but not unladen ants. Clearing efforts by unladen workers were sensitive to the experience of their laden nestmates; they intensified attacks on a low barrier that impeded traffic but not on an equivalent barrier too high to strike leaf fragments. By contrast, a low barrier in the absence of laden ants or an ineffective visual 'barrier' did not elicit increased clearance attempts. Our results demonstrate that leaf-cutting ants can overcome an information asymmetry challenge, in which one group possesses the information that another must act upon. This allows the ants to adaptively modulate their trail-clearing efforts.