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
, 5th International Conference on Methods and Techniques
in Behavioral Research, 30 August - 2 September 2005, Wageningen, The
Netherlands.
© 2005 Noldus
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