Learning about larceny: experience can bias bumble bees to rob nectar

How do nectar-feeding animals choose among alternative flower-handling tactics? Such decisions have consequences not only for animal fitness (via food intake) but for plant fitness as well: many animals can choose to "rob" nectar through holes chewed in the base of a flower instead of "legitimately" collecting it through the flower's opening, thus failing to contact pollen. Although variation within a species in these nectar-foraging tactics is well documented, it is largely unknown why some individuals specialize (at least in the short term) on robbing, others on legitimate visitation, and others switch between these behaviors. We investigated whether the tendency to rob nectar through previously-made holes (secondary robbing) is influenced by prior foraging experience. In a laboratory experiment, we trained groups of bumble bees (Bombus impatiens) either to visit artificial flowers legitimately or to secondary-rob; a third group received no training. On subsequent visits to flowers, all bees had the opportunity to use either foraging tactic. We found that experience did affect bees' tendency to secondary-rob: trained bees were more likely to adopt the tactic they had previously experienced. Untrained bees initially sampled both tactics, but over time preferred to secondary-rob. Experience also increased bees' success at gaining nectar from flowers, but only when visiting flowers legitimately (the less preferred tactic). Overall, these findings highlight the importance of experience in animals' choices of alternative handling tactics while foraging and help explain long-standing observations of variation in nectar-robbing behavior among individuals of the same population.