Bumblebees Do Not Respond to Variance in Nectar Concentration

Authors

  • Keith D. Waddington

    Corresponding author
    1. Department of Biology, University of Miami, Coral Gables
      Department of Biology, University of Miami, Coral Gables, Florida 33124, USA.
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Department of Biology, University of Miami, Coral Gables, Florida 33124, USA.

Abstract

Worker bumblebees (Bombus fervidus) were given repeated binary choices between two colors of artificial flowers with the same associated mean nectar concentration (X̄ = 20%), but with different variances in nectar concentration. Flowers of one color, yellow or blue, rewarded a bee with 1 μl of 20% sucrose solution (low-variance flower type) on each visit (p = 1) and flowers of the other color rewarded a bee on each visit with 1 μl of either 10% or 30% sucrose (p = 0.5; high-variance flower type). Of the 10 bees tested, nine showed no preference for either the high- or low-variance flowers (indifferent or risk-insensitive). This result is similar to honeybee responses to variation in nectar concentration, despite differences in foraging ecology between bumblebees and honeybees. Flower-choice behaviour in the presence of variance in nectar concentration is a response to the expected concentration of the alternative flower types. Possible mechanisms of risk-sensitive foraging behaviour in bees are discussed.

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