The effect of prior experience on nest site evaluation by the ant Temnothorax curvispinosus

Animals are expected to follow decision-making strategies that balance the benefits of choosing the best option with the costs of finding and assessing candidates. Because costs and benefits will vary across time and space, an animal may profit by adjusting its tactics according to recent experience. In particular, animals should be less selective when experience indicates that the average quality of options is low. We tested this prediction in the context of nest site selection by the ant Temnothorax curvispinosus. Colonies received prolonged exposure either to a good or to a poor nest and then were tested for their readiness to accept a mediocre nest. Previous studies have shown that colonies move more rapidly into nests that they rate more highly, as a result of faster recruitment initiation by individual ants. Hence, if exposure to a low-quality nest makes colonies more willing to accept a mediocre one, we predicted speedier moves into the mediocre nest after the poor treatment than after the good treatment. Our results showed a clear effect of treatment, but contrary to our prediction, ants moved more rapidly after living in a good nest than after living in a poor nest. We discuss three effects that may explain these results: (1) quality-dependent changes in colony condition, (2) quality-dependent changes in colony size and (3) differences in the urgency of emigration perceived by ants in the two nest types. Our finding illustrates that animal collectives, like individuals, use recent experience to tune their decision strategies.