Foraging as an Exploratory Activity in Bees: The Effect of Patch Variability

Tamar Keasar, Uzi Motro & Avi Shmida

Foraging can be viewed as a dual activity: a food-collection process, and an exploration process, which enables foragers to sample and evaluate food resources. The exploratory role of foraging was studied in a series of two-stage laboratory experiments on naive bumblebees. In the first stage of the experiments the bees were allowed to forage on three types of artificial flowers, which were arranged in spatially distinct patches. The mean reward offered by the flowers, the variability in reward among feeding patches and the variability of rewards within patches were varied between experimental treatments. In the second stage a new feeding patch, containing non-rewarding flowers, was added. The bees' visits to this patch were recorded as a measure of exploratory activity, and were related to their previous foraging experience. Bees which had experienced within-patch reward variability explored the non-rewarding patch more than bees which had not been previously exposed to within-patch variability. On the other hand, variability in rewards between feeding patches led to lower exploration levels than in the control experiments, which had no between-patch variability. Exploration effort was not affected by the mean overall nectar volume offered to the bees. Some visits to the non-rewarding patch were recorded even when the other patches offered high nectar volumes on each foraging visit. Individuals within the same treatment varied considerably in exploration effort. Possible sources of this variation are discussed. We conclude that exploration effort in bees is independent of foraging experience to some extent. On the other hand, it is also affected by the variability of their food sources.

November, 1996
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