“Local regulation of trail networks of the arboreal turtle ant, Cephalotes goniodontus”

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Deborah M. Gordon

Turtle ants make resilient trail networks in the canopy of the tropical forest

Turtle ants in the tangled canopy of the tropical dry forest in western Mexico make a network of trails that builds on the network of vegetation. The nodes of the network are junctions from one branch, stem or vine to another, and the edges are the stems or branches that the ants move along. The ants lay pheromone as they go. This study asks how a colony, operating without central control, is able to use simple local cues to maintain, build and repair its highway system.

The trail network links nests and food sources, so ants must keep circulating around it to keep the colony together. But ants find baits away from the trail, showing that some ants occasionally choose a new path through a junction. This slight tendency to make an error allows the ants to repair trails as well as to find new food sources. Often branches are broken by the wind or animals passing through. In experiments in which stems along the path were cut, the ants quickly found new paths, using “breadth-first search” that starts from the nodes nearest the break.

The turtle ants’ resilient algorithm for maintenance and repair may be useful for engineered networks. The algorithm does not produce the shortest possible path, but instead the path that minimizes the number of nodes at which ants could take the wrong turn and get lost. It keeps the ants on coherent trails, while providing a way to repair ruptures quickly and explore for new resources. Read the Article