Creating a routing backbone is a fundamental problem in both biology and engineering. The routing backbone of arboreal turtle ants ( Cephalotes goniodontus ) connects many nests and food sources using trail pheromone. Unlike species that forage on the ground, arboreal ants are constrained to form trail networks along branches and vines within the vegetation. We examined what objectives the ant networks meet by comparing the observed turtle ant trail networks with alternative networks of random, hypothetical trails in the same surrounding vegetation. We found that turtle ant trail networks favor coherence, keeping the ants together on the trails, rather than minimizing the distance traveled along edges in the graph. The ants’ trails minimized the number of nodes traversed, reducing the opportunity for ants to get lost at each node, and favored nodes with 3D configurations most easily reinforced by pheromone, reducing the opportunities for ants to diverge onto different paths. Thus, rather than forming the shortest paths, the ant networks take advantage of natural variation in the environment to promote the maintenance of a coherent trail that ensures that ants stay connected along the routing backbone.

Better tired than lost: turtle ant trail networks favor coherence over shortest paths