The outflyer rate as a usable field method for verifying defense strategies in western honeybees

G. Kastberger¹, R. Thenius¹ and R. Hepburn²

¹Department of Zoology, University of Graz, Graz, Austria
²Department of Zoology, Rhodes University, Grahamstown, South Africa

We investigated the responsiveness of 11 honeybee colonies of three African and European subspecies (Apis mellifera capensis, scutellata, carnica) to disturbances regarding the foraging and defense status. We used three stimulation regimes: the m-regime referred to mechanical shocks which were delivered to the bees in the hive. These shocks were set for 3 min, at a rate of one per 2 s; the p-regime exposed the colonies to alarm pheromones which were placed on cotton buds, doped with 10 natural stings, 10 cm in front of the hive, so that the bees had to fly from the hive entrance to reach it; the regime mp combined mechanical shocks and alarm pheromones. Each experiment comprised an initial pre-stimulation phase of 3 min reflecting the undisturbed condition, a stimulation phase of 3 min, and a post-stimulation phase of 10 min. Colonies were tested for 10 days at different ambient temperatures and times of day. We video-recorded the hive entrance throughout the experiments and observed three groups of bees: Crawlers represented ground traffic at the hive entrance, scanners faced the hive entrance either in straight or in hovering .ight, and outflyers which departed from the entrance plate of the hive. The outflyer rate under undisturbed conditions provided the baseline foraging level and the reference for the net outflyer rate which confers the responsiveness to stimuli; here, positive values signify the release of flying guards, negative rates the retreat of foragers to the nest. This field method is usable to prove the significance of anecdotal observations on genetic dispositions of colonies that some colonies are more docile, while others are more aggressive, and the further-going question whether one and the same colony may utilize the whole spectrum from docile to aggressive. On mechanical stimulation the colonies resolved irrespective to their membership to a respective subspecies into two defense response types of considerable constancy; releaser colonies increased the rate of outflyers, and retreater colonies reduced them on stimulation. Exposure to alarm pheromones alone evoked only weak responses; but under combined stimulation the colonies increased those behaviors exhibited under mechanical stimulation.

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.

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