Flower choice copying in bumblebees

Abstract

We tested a hypothesis originating with Darwin that bees outside the nest exhibit social learning in flower choices. Naive bumblebees, Bombus impatiens, were allowed to observe trained bees or artificial bees forage from orange or green flowers. Subsequently, observers of bees on green flowers landed more often on green flowers than non-observing controls or observers of models on orange flowers. These results demonstrate that bumblebees can change flower choice by observations of non-nest mates, a novel form of social learning in insects that could provide unique benefits to the colony.

Figure 1

Schematic of the experimental apparatus. (a) The observation box (A) was attached to the modelling arena (B). The observer bee in (A) could view the foraging array (C) that was located 25 cm from the observation box. The barrier separating A from B consisted of a Plexiglas wall bordered by fine wire screening. (b) A close-up view of the foraging array showing the arrangement of the coloured ‘flowers’. ‘Flowers’ were 2.5 cm and 5.5 cm apart vertically and horizontally, respectively, and consisted of coloured paper rings surrounding a central wick.

Figure 2

The proportion of landings on green flowers for bees that watched (a) live foraging bee models and (b) artificial models (± s.e.). Values within a panel indicated by different letters are significantly different. Pairwise-comparisons between model colours were made with Bonferroni adjustment: (a) GM/C, p<0.03; GM/OM, p<0.01; OM/C, p>0.90 and (b) GM/C, p=0.001; GM/OM, p<0.001; OM/C, p>0.90.