Decisions made by foraging animals conform a complex process based on the integration of information from multiple external environmental stimuli and internal physiological signals,which in turn are modulated by individual experience and a detection threshold of each individual.For social insects in which foraging is limited to given age subcastes,individual foraging decisions may also be affected by ontogenetic shifts and colony requirements.We studied the short-term changes in foraging preferences of the generalist wasp Vespula germanica,focusing on whether the individual response to different resources could be influenced by the ontogenetic shifts and/or by social interaction with nestmates.We carried both laboratory and field experiments to confront worker wasps to a short-term resource switch between either protein or carbohydrate-based foods.We tested the response of(1)Preforager workers(no foraging experience nor interaction with other wasps),(2)Forager workers(experience in foraging and no colony feedback),and(3)Wild forager workers(foraging naturally and exposed to free interactions with nestmates).We evaluated the maxilla-labium extension response(MaLER)for laboratory assays or the landing response for field assays.We observed that for wasps deprived of colony feedback(either preforagers or foragers),the protein-rich foods acceptance threshold increased(and thus a lower level of foraging on that item was observed)if they had foraged on carbohydrates previously,whereas carbohydrates were accepted in all assays.However,wasps immersed in a natural foraging context did accept protein foods regardless of their first foraging experience and reduced the carbohydrates collected when trained on protein foods.We provide evidence that short-term changes in foraging preferences depend on the type of resource foraged and on the social interactions,but not on ontogenetic shifts.
The foraging strategy at abundant resources of the social wasp Vespula germanica includes scanning in the direction of the nest while memorizing resource-specific landmarks and contextual cues.In the present study,we sought to explore wasps'behavioral plasticity on foraging trips to resources whose location and composition changed after a single visit.We evaluated how contextual modifications of food displacement and replacements 60 cm apart from the original site,affect re-orientation for re-finding previously memorized food resources.The results showed that wasps detected and collected the resource faster when more changes were introduced on the following visit.If returning foragers discovered several modifications on both the location and the kind of resource,they collected food more rapidly from the displaced dish,than if only a single parameter in the environment had been changed.These findings illustrate the grade of behavioral plasticity in V.germanica while foraging on abundant resources,which may contribute to the understanding of the prodigious invasive success of this species in anthropized environments.
