Social Learning in Vespula Germanica Wasps: Do They Use Collective Foraging Strategies?

Vespula germanica is a social wasp that has become established outside its native range in many regions of the world, becoming a major pest in the invaded areas. In the present work we analyze social communication processes used by V. germanica when exploiting un-depleted food sources. For this purpose, we investigated the arrival pattern of wasps at a protein bait and evaluated whether a forager recruited conspecifics in three different situations: foragers were able to return to the nest (full communication), foragers were removed on arrival (communication impeded), or only one forager was allowed to return to the nest (local enhancement restricted). Results demonstrated the existence of recruitment in V. germanica, given that very different patterns of wasp arrivals and a higher frequency of wasp visits to the resource were observed when communication flow between experienced and naive foragers was allowed. Our findings showed that recruitment takes place at a distance from the food source, in addition to local enhancement. When both local enhancement and distant recruitment were occurring simultaneously, the pattern of wasp arrival was exponential. When recruitment occurred only distant from the feeder, the arrival pattern was linear, but the number of wasps arriving was twice as many as when neither communication nor local enhancement was allowed. Moreover, when return to the nest was impeded, wasp arrival at the bait was regular and constant, indicating that naive wasps forage individually and are not spatially aggregated. In conclusion, this is the first study to demonstrate recruitment in V. germanica at a distance from the food source by modelling wasps’ arrival to a protein-based resource. In addition, the existence of correlations when communication was allowed and reflected in tandem arrivals indicates that we were not in the presence of random processes.德国黄胡蜂（Vespula germanica）是一种社会性胡蜂，目前已在其原生分布范围之外的全球诸多区域成功定殖，并在入侵区域成为主要害虫。 本研究针对德国黄胡蜂在利用未被消耗殆尽的食物资源时所采用的社会通讯过程展开分析。为此，本研究调查了胡蜂抵达蛋白质诱饵的动态模式，并在三种不同情境下评估了觅食蜂（forager）是否会招募同种个体：一是觅食蜂可返回蜂巢（完整通讯情境），二是觅食蜂抵达后即被移除（通讯受阻情境），三是仅允许单只觅食蜂返回蜂巢（局部增强（local enhancement）受限情境）。 研究结果证实德国黄胡蜂存在招募行为（recruitment）：当允许有经验与无经验觅食蜂之间进行通讯交流时，观测到的胡蜂抵达模式与资源访问频率均存在显著差异。 本研究结果表明，除局部增强（local enhancement）效应外，德国黄胡蜂还可在远离食物源的位置开展远距离招募（distant recruitment）行为。当局部增强（local enhancement）与远距离招募（distant recruitment）同时发生时，胡蜂的抵达模式呈指数分布；若仅存在远距离招募（distant recruitment），抵达模式则呈线性分布，但抵达胡蜂的数量为无通讯且无局部增强（local enhancement）情境下的两倍。此外，当返回蜂巢的路径受阻时，胡蜂抵达诱饵台的过程呈现规律且稳定的特征，这表明无经验的胡蜂会单独觅食，不存在空间聚集现象。 综上，本研究首次通过对德国黄胡蜂抵达蛋白质基资源的过程进行建模，证实了该物种可在远离食物源的位置开展招募行为（recruitment）。此外，当允许通讯交流时，观测到的抵达模式存在相关性且体现为结伴抵达，这表明该过程并非随机过程。