Evidence of associative blocking during foraging in the social wasp Vespula germanica.

Abstract

While foraging, Vespula germanica usually return to abundant food sites. During this relocation behavior, these wasps learn to identify contextual cues associated with food position. We analyzed associative blocking in this species, that is, how an association with a conditioned stimulus (CS1) blocks subsequent learning when a novel stimulus (CS2) is added on a second foraging visit. Three groups of wasps (A, B, and C; total 74 individual wasps) were observed while collecting meat during one or two consecutive visits. In group A, an environmental cue (CS1) was paired with food placed at a specific site, and on the second visit, a second cue (CS2) was added while food remained in the same position. In a subsequent testing phase, CS1 was removed and the food source displaced nearby. We then recorded the number of hovers performed over the empty dish (previously baited). Group A wasps appeared to ignore the addition of CS2 on their second visit because they performed fewer hovers over the learned site. For group A, the duration of the decision-making process to finally fly toward the baited dish was shorter than when CS1 and CS2 were presented together on their first visit (group B). This is the first study to demonstrate the occurrence of associative blocking in vespids, confirming that a prior foraging experience influences subsequent food relocation in V. germanica. Our findings reveal that first learning episodes block further associations with novel contextual cues, contributing to understanding of complex cognitive processes involved in V. germanica´s foraging behavior.