Branching Angles of Ant Trunk Trails as an Optimization Cue

The branching angles of the ant Messor barbarus (L.) trunk trails are studied in relation to their intraspecific competitive environment and surrounding vegetation cover. Both factors appear to play a significant role in branching angle size. We propose that a principle of optimality acts to minimize foraging costs in terms of fighting risk or difficulties imposed on the mobility of the individual forager ants. Our results coincide with a compromise between the advantages of trunk trail and the shortest way of return to the nest.