On the tradeoff between the mean and the variance in foraging: Effect of spatial distribution and color preference
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An enclosed colony of bumblebees (Bombus pennsylvanicus) was restricted to foraging on two artificial flower types. The means and variances were adjusted in the two flower types in order to detect risk sensitivity. Both the mean and the variance contributed to the bees' foraging decisions. A series of experiments was designed to construct the bees' indifference curve under a variety of ecological conditions. The indifference curve represents combinations of mean and variance in nectar reward for which bees showed no preference. In three of the four experiments there was a positive tradeoff between the mean and the variance, i.e., a relatively more variable flower type could be compensated for by increasing its expected reward. The quantitative nature of the tradeoff is shown to be sensitive to ecological parameters (e.g., spatial distribution of flowers) and independent behavioral parameters (e.g., intrinsic color preference).