Deborah M. Gordon

This study examines how an arboreal ant colony maintains, extends, and repairs its network of foraging trails and nests, built on a network of vegetation. Nodes are junctions where a branch forks off from another or where a branch of one plant touching another provides a new edge on which ants could travel. The ants’ choice of
edge at a node appears to be reinforced by trail pheromone. Ongoing pruning of the network tends to eliminate cycles and minimize the number of nodes and thus decision points, but not the distance traveled. At junctions, trails tend to stay on the same plant. In combination with the long internode lengths of the branches of vines in the tropical dry forest, this facilitates travel to food sources at the canopy edge. Exploration, when ants leave the trail on an edge that is not being used, makes both search and repair possible. The fewer the junctions between a location and the main trail, the more likely the ants are to arrive there. Ruptured trails are rapidly repaired with a new path, apparently using breadth-first search. The regulation of the network promotes its resilience and continuity.