Ants adjust attribute weights according to prior experience

Evolutionary theory predicts that animals act to maximize their fitness when choosing among a set of options, such as what to eat or where to live. Making the best choice is challenging when options vary in multiple attributes, and animals have evolved a variety of heuristics to simplify the task. Many of these involve weighing attributes according to their importance. However, importance can vary across time and place, hence animals might benefit by adjusting weights accordingly. Here we show that colonies of the ant Temnothorax rugatulus learn to place greater weight on more informative attributes when choosing a nest site. These ants choose their rock crevice nests on the basis of multiple features, including entrance size and interior brightness. After exposure to an environment where one attribute better differentiated options than the other, colonies increased their reliance on the more informative attribute. Although many species show experience-dependent changes in selectivity of a single feature, this is the first evidence in animals for changes in the weighting of multiple attributes. We discuss how this collective-level flexibility emerges from individual behavior.