Formation of branching angles at bifurcations of ant trail networks

Ants form dendritic trail networks around the nest to search for and exploit food sources located at the periphery of the network. Studies found these trail networks to be very efficient for the ants in terms of time and energy, which later was found stored in the bifurcation angle (θ) of the branches of these trail networks. It has been observed, that bifurcations are symmetrical when moving from the nest to the food source, while are asymmetrical when moving back towards the nest. The mean bifurcation angles have been found to be 50° - 80° for networks radiating out from the nest. This thesis focuses on the formation of the bifurcation angles and devising a model to illustrate their formation. It has been hypothesized that if the θ is small, the ants continue moving straight in the initial direction, and make the choice for an emerging branch after the bifurcation, thereby increasing θ, whereas it would decrease for large θ values, as the ants turn early to their choice of emerging branch. Also, for large θ values, it will be difficult for the ants to follow the trail. To test this, experiments with multiple individual ants were conducted on chemically marked ‘Y’ shaped paper strips with differing θ. Similarly in a model, simulated ants were run on ‘Y’ shaped trails with differing θ. Results show that the decision point (point at which ants turns for its emerging branch) moves away from the emerging branches with an increase in angle of bifurcation and the average maximum distance increases with the angle of bifurcation. Angles in the range of 20 °- 60° were found to minimize the above constraints, and provide a stable trail network