Measuring Behavior 2005: Schmelzer and Kastberger

Use of image analysis to measure the impact of shimmering behavior in Giant honeybees on predatory wasps

E. Schmelzer and G. Kastberger

Department of Zoology, Karl-Franzens University of Graz, Austria

The nest of the Southeast-Asian Giant honeybee Apis dorsata consists of a single comb covered by several layers of bees forming a curtain. As these bees nest predominantly in the open, they are more exposed to predators than cavity-dwelling species. It is this predatory pressure that has induced the evolution of a series of defense strategies. One of these strategies is the so called shimmering behavior, which is evoked by approaching wasps and established by abdominal flipping of surface bees. This colony response can be termed more interpretatively as defense waving. The present paper proves the impact of the waving on predatory wasps. Natural wasps hover in front of the Giant honeybee nest and by that, they regularly elicit defense waves. In turn, the hovering wasps respond sensitively to such wavings. We videotaped the recurrent wasp attacks and the responses of the giant honeybee nest and transferred the video film into tif-images at a rate of 25 frames per s. We measured the responsiveness of the wasp by assessing their flight trajectories, its ground velocity and acceleration and its distance to the nest. The waving was quantified by image analysis (Optimas, Flir); in total, we analyzed 7727 images. Our data address the interplay between hunting, predator and self-defending prey. It provided evidence for the repellence effect of defense waving against predatory wasps. We show that the defense waving of giant honeybee forces the wasp to keep a distance of 53,7 ± 0,3 cm (mean and mean error; n = 4407 images) from the nest.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.