Can ant colonies choose a far-and-away better nest over an in-the-way poor one?

Nest choice in the ant Temnothorax albipennis is a model system for investigating collective decision making. Previous research has demonstrated the sophistication of this decentralized system, yet such studies have focused on binary choices in which alternative nest sites are equidistant from the colony's original nest. In nature, for example, a poor nest might be closer than a better one. Hence, to investigate the collective decision-making system of these ants further, we challenged colonies with a choice between a distant high-quality nest and a much closer and collinear poorer one. Colonies successfully emigrated to the better nest when it was two, three or even nine times further away than the collinear poorer one. Most often, colonies started emigrating simultaneously to both nests, and then they redirected all traffic exclusively to the better, more distant one. We show that this is a good strategy for minimizing exposure and risk. In principle these ants might compensate for distance effects by increasing recruitment latencies and quorum thresholds at nearby poor nests so that they are better able to find and use distant better ones. However, the simplest explanation is that scouts are more likely to begin to look elsewhere, at all stages of the decision-making and emigration process, whenever and wherever they have initially found a low-quality nest. (c) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.