Path minimization in a tandem running Indian ant in the context of colony relocation

The phenomenon of minimizing the path length to a target site in order to increase transport efficiency is described as path optimization, and it has been observed in many mammals, birds and some invertebrates such as honeybees and ants. It has been demonstrated that ants can optimize their foraging path through an emergent process, involving the trail pheromone concentration, without individual ants having to measure and compare distances. In the current study, we investigated whether ants that use only tandem running to recruit their nestmates can minimize their path while relocating their entire colony into a new nest. As colony relocation directly impacts the survival of the whole colony, it would be particularly important to optimize their path to the new nest. Using the ponerine ant Diacamma indicum, we conducted relocation experiments, in which ants had to choose between different defined paths, and contrasted our findings with open arena experiments, as they navigated to their new nest. After following 4100 unique transports by 450 different transporters, we found that these ants do minimize their path. Individual leaders, as well as colonies, chose the shorter path significantly more than the longer path, and they showed a significant preference for the shorter arm at multiple decision points on encountering a combination of paths. Thus, we concluded that tandem leaders are capable of path minimization based on the information they themselves collect. Further investigation into the proximate mechanisms by which they achieve this is required.