Decision-making in a changing environment: A look at the foraging behavior of honeybees and bumblebees as they respond to shifts in resource availability

As any animal moves through its environment seeking resources it is continually faced with the challenge of how best to allocate its time and energy among available options. In natural environments, animals must continually choose among a suite of behavioral options available to them in order to respond effectively to shifts in resources. Historically these behavioral options have been studied in isolation despite the fact that, in nature, animals must coordinate these behaviors over time. Chapter 1 describes an integrated approach to examining these behaviors by looking simultaneously at the behavioral processes of extinction, negative contrast effects, and exploration as bees (both honeybees and bumblebees) respond to a dramatic downshift in available food resources. Additionally. Chapter 1 explores how the integration of these processes is influenced by such social factors as colony size and recruitment mechanisms as well as individual biological factors, particularly body size. The results from this assay suggest that extinction, contrast effects, and the decision to explore, occur in nature in a much more integrated fashion than has been previously acknowledged. Additionally, these results support the notion that while honeybees are much more dependent upon social information for foraging decisions, bumblebees are, in contrast, much more reliant upon gathering information on resources directly from the environment. Chapter 2 examines species differences in more detail, focusing on the question of how honeybees and bumblebees differ in terms of not only their sensitivity to shifts in reward magnitude, but also the decision processes subsequent to abandoning a past-profitable site. The results suggest that bumblebees are much more sensitive to shifts in reward, relative to honeybees, and that bumblebees are much more likely to explore the environment, and more likely to discover a novel food source subsequent to departing a past-profitable site. These results are very consistent with the findings from Chapter 1, and give strong support for notion that bumblebees are comparatively more reliant than honeybees upon the direct acquisition of information from the environment. Chapter 3 examines the longterm effects of honeybees' tendency to forgo feeding at a low quality food source when no other food is available, and looks at how this behavioral phenomenon might enhance fitness among honeybees. This was a follow-up on the finding from Chapter 1 that honeybees are generally very reluctant to resume feeding at a low quality feeder, following experience at a high quality food source. Chapter 3 tests the hypothesis that by not exploiting available but low quality food when there is an indication that better food will be available in the future, actually increases their lifetime contribution of food resources to the colony. The results show that honeybees that forgo exploiting available low quality food, having had previous experience with a high quality feeder, are more likely to live longer and ultimately contribute more food to the hive, than bees that forage continually at a low quality food source.