Ants build transportation networks that optimize cost and efficiency at the expense of robustness

Like modern human societies, many biological systems are dependent on transportation networks for the efficient distribution of resources and information. Network builders face the daunting challenge of optimizing conflicting network criteria such as robustness, efficiency, and cost, which cannot be optimized simultaneously. Here, we use graph and network theory to examine the trail networks of the polydomous meat ant Iridomyrmex purpureus. Meat ants build and maintain physical trails that connect their multiple nests to each other and to food resources. The resulting transportation network is used to distribute workers, brood, and food resources. We found that meat ants built low-cost trail networks that were relatively efficient. However, networks were less robust than comparable simulated networks, suggesting that meat ants prioritize cost and efficiency over robustness. Populous nests had higher connectivity than did less populous nests, implying they play a key role in resource distribution throughout the network. We propose that meat ant networks are an ideal model system for the development of network optimization heuristics.