Latent learning improves foraging efficiency in ants

Learning allows animals to react to changing environmental conditions and to respond to stimuli in an adaptive way, for instance by giving novel stimuli positive or negative value. However, there is a form of learning that does not require reward or punishment: latent learning. This knowledge is hidden at the time of learning but it manifests later when a suitable incentive appears. Latent learning helps animals to navigate their environments, thus improving foraging efficiency, especially when resources are unpredictably distributed. Although latent learning has been well documented in vertebrates, including humans, it remains relatively understudied in invertebrates. We investigated whether ants use latent learning during foraging in the species Aphaenogaster senilis, living in open and sunny environments. We compared the efficiency of two groups of ants navigating a maze to get food. One group of ants was previously exposed to an empty maze (experienced), while the other group was not (control). The ants with previous experience of the empty maze found the food faster than the control group when the food was present, consistent with a positive effect of latent learning on foraging efficiency. Moreover, experienced ants returned to the nest more rapidly after discovering the food for the first time than control ants, indicating that information acquired during unrewarded explorations subsequently facilitated goal-directed behaviour. We then characterized for exploratory activity individual ants that solved the maze and ants that did not, using an open-field test. We found that maze-solvers were less exploratory than non-solvers, suggesting a potential speed-accuracy trade-off. Taken together, our results show the use of latent learning during individual foraging in ants and highlight the role of inter-individual variability in foraging strategies.