Competition between honey bees (Apis mellifera) and bumble bees (Bombus spp.) foraging on lavender
Our previous research found the ratio of bumble bees to honey bee foragers was consistently ten to one on lavender flowers. Morphological analysis indicated that bumble bees had relatively long tongues, which enable more efficient handling of lavender's deep flowers. As there was no evidence of aggression between foraging bees, an obvious inference was that consumptive competition from bumble bees was deterring honey bee visitation.
We tested the prediction that excluding bumble bees from lavender would increase the number of honey bees, but not vice-versa. The results support the prediction: excluding bumble bees increased the number of honey bees approximately 20-fold and resulted in multiple changes to their foraging behaviour. Conversely, excluding honey bees had no effect on bumble bee numbers or behaviour. Changes in honey bee foraging strategy and flower-choice were presumably linked to an increase in lavender nectar availability observed with the exclusion of bumble bees.
Our results demonstrate competition between honey bees and wild pollinators can potentially influence their flower choice, foraging behaviour and cross-pollination services.
