Temporal and spatial pattern of trail clearing in the Australian meat ant, Iridomyrmex purpureus

Abstract

Many ant species use trails to connect important resources. In addition, some ants actively clear obstacles from their trails. Although trail clearing is thought to be beneficial in decreasing travel time, the physical process of clearing requires an investment of time and energy. Given that trail clearing is a decentralized process, how do colonies decide when to invest in clearing? In this study, we examined trail clearing in the Australian meat ant, using artificial semipermeable barriers mimicking grass. We tested the hypothesis that investment in clearing was influenced by the abundance and physical toughness of obstacles and that the selection of which grass blade to cut was a nonrandom process that decreases travel distance. We found that low abundance/low toughness treatments experienced the greatest amount of clearing and high abundance/high toughness the least. Although ants did not clear an optimally efficient trail, the results of our percolation analysis support the inference that the ants strategically deployed clearing, taking multiple factors into account when deciding to invest in this strategy. The resultant clearing patterns provided shorter travel routes for foraging ants than would be expected by the random removal of obstacles.