BUMBLE BEE (BOMBUS IMPATIENS) NECTAR FORAGING STRATEGIES: RESPONSES TO CHANGING NECTAR AVAILABILITY

Abstract

Nectar foraging bees utilize two primary tactics to extract nectar from flowers: legitimate visitation and nectar robbing. Legitimate visitation enables transfer of pollen and is beneficial for the plant, while nectar robbing fails to transfer much, if any, pollen and potentially harms plant reproduction. During foraging, a given bee will largely use a single foraging tactic throughout a given bout, choosing to visit similar flowers and extract nectar using the same handling tactic. We investigated the propensity of Bombus impatiens bumble bees to either switch the handling tactic they were initially using or to continue using the tactic but switch the type of flowers they preferred to forage on. To test this, we forced bees to switch either flower type or handling tactic in order to continue receiving a sucrose reward. We found that under most conditions bees preferred to switch flowers and retain handling tactic. However, when given previous experience in legitimate foraging and then given legitimate access to new flowers markedly different from those they had previous experience with, bees instead tended to switch to nectar robbing in order to continue using the same flower type. These findings suggest a difference in cost between switching flowers while foraging legitimately and switching while nectar robbing. Our results also suggest that the visual similarity of a new floral resource to the currently exploited resource plays an important role in decision making by foraging bumble bees.