Seed choice by rodents:: learning or inheritance?

Learning plays a central role in animal life, and it has received special attention in the context of foraging. In this study, we have tested whether learning operates in seed choices by rodents using the Algerian mouse (Mus spretus) and Holm oak (Quercus ilex) acorns as a model. At the laboratory, those rodents captured in the field during the acorn fall period (experienced individuals) rejected weevil-infested acorns, presumably because of their lower energetic value. By contrast, rodents born in captivity and reared without any contact with acorns (naives) predated weevil-infested acorns at similar rates than sound ones. After exposing naives to infested and sound acorns during 15 days, they rejected infested acorns as the experienced individuals. In the field, predation on weevil-infested acorns was lower than on sound ones. Predation rates on infested acorns were lowest at the end of the acorn fall season, whereas predation rates of sound acorns increased along the same period. This might be explained by the improved ability to reject infested acorns because of the accumulated experience acquired by the initially naive rodents along the acorn fall season. We show that learning shapes strongly seed choices by rodents, and it may be advantageous over inherited behaviors in variable unpredictable situations, such as acorn infestation rates that vary strongly between years and trees. We consider that the role of learning has to be taken into account in future studies on seed predation by rodents.