Can Myrmica rubra Ants Use Tools or Learn to Use Them?

The aim of this study was to define the limit of ant cognition, and we examined whether Myrmica rubra ants could use tools or learn to use them. We presented the ants with 1) a piece of mealworm inserted into a small tube tied to a thread that had to be pulled for easy access to the mealworm; 2) a plug that closed the entrance of the ant sugar water tube provided with two push-pieces that had to be pushed to remove the plug from the entrance; and 3) a plug, closing the nest entrance, provided with a thread that had to be pulled to remove the plug. The ants could not use these “proto-tools”. After exposure to proto-tools having been used, some ants interacted with them, shortly, not efficiently. During the first experiment, the ants received the larva progressively inserted further into the tube, and interacted with the proto-tool more than during the two other experiments. Therefore, Myrmica rubra ants might be able to use some proto-tools following long-lasting habituation, imitation or conditioning processes, which would not be a strictly use of tools. Thus, ant cognition in this species extended up to but did not include the use of proto-tools, and at fortiori of sensu stricto tools.