Trapline foraging by nectar-collecting hornets
Central place foraging bees, butterflies, birds and bats are known to develop routes in order to visit familiar plant resources in a stable and repeatable order called "traplines". Here we report a similar behaviour in a social wasp, the Japanese yellow hornet Vespa simillima. We monitored the foraging movements of individually marked wild hornets collecting sucrose solution on four artificial flowers placed in the field. After thirty foraging bouts, all the hornets had developed a repeatable flower visitation sequence. Using two different arrays of flowers, we show how hornets increase their foraging efficiency through time but do not always use the shortest path to visit all flowers, often favoring movements between nearest neighbor flowers over global path optimization. Our study adds nectar-foraging wasps to the growing list of animals developing traplines thereby opening new perspectives for comparative cognition research.