Bumblebee social learning can lead to suboptimal foraging choices

Bumblebees are influenced by socially acquired information when deciding on which flowers to forage. In some circumstances, however, this attraction towards conspecifics may lead to suboptimal foraging performance because the presence of multiple pollinators typically results in a faster rate of nectar depletion in the flower. We tested the capacity of bees to learn to avoid flowers occupied by conspecifics when they offered a lower reward than unoccupied similar flowers. Bumblebees were able to discriminate between poorly and highly rewarding flowers by using the presence of a nonsocial cue (a wooden rectangular white block). When poorly rewarding flowers were indicated by social cues (model bees), however, bees did not discriminate between the two flower types except when an additional cue was provided (flower colour). These findings indicate that bumblebees attach particular meaning to conspecific presence on flowers, even when this could lead to suboptimal foraging performance. The relatively lower flexibility in the use of social than nonsocial cues suggests a biased positive value of conspecifics as indicators of rewarded flowers.