Pollen collection by bumblebees (Bombus impatiens):: the effects of resource manipulation, foraging experience and colony size

To examine factors influencing pollen collection by bumblebees (Bombus impatiens), we compared pollen collection in free-foraging resource-manipulated colonies (i.e., pollen-and nectar-deprived vs. pollen-deprived only). Additional manipulations included prior foraging experience in Experiment I and colony size in Experiment 2. In Experiment I, colonies were either deprived of both resources or deprived of only pollen and were subsequently tested while deprived of both resources. Colonies that had experience in managing both foraging tasks subsequently collected more pollen and allocated greater foraging effort than did colonies that had experience only in collecting pollen. In Experiment 2, larger colonies collected more pollen although smaller colonies collected more pollen relative to their colony size. Results show that colonies collect more pollen when deprived of both resources, exhibit foraging efficiency depending on previous tasks, and allocate foraging effort according to nutritional and energetic demands. Because pollen collection is partly regulated by nectar availability, one practical implication for growers of bumblebee-pollinated crops is that pollination may be improved by causing colonies to forage for nectar as well as pollen.