Starvation drives a threshold triggering communication.

The decision for an ant forager to launch recruitment is governed by an internal response threshold. Here, we demonstrate that this threshold (the desired volume) triggering trail-laying increases under starvation. As a consequence, highly starved foragers lay a recruitment trail and bring back to the nest higher quantities of food from large unlimited resources. In contrast, when the volume of the food source is under their crop capacity, the percentage of trail-communicating foragers is lower following a prolonged period of starvation. Such starvation-dependent changes in the "desired volume" threshold explain how ants optimize recruitment and select liquid food resources in order to prevent collective exploitation of low profitability.