Choice in a floral marketplace: the role of complexity in bumble bee decision-making

Animals have evolved in complex, heterogeneous environments. Thus, decision-making behavior is likely affected by a diversity of co-occurring community-level traits. Here, we investigate how 3 co-occurring traits of floral communities—the number of flower types, reliability that flowers are associated with a reward, and signal complexity of flowers—affect bumble bee (Bombus impatiens) decision-making. We used arrays of artificial flowers in a full factorial experimental design to assess floral selectivity (preference and constancy), foraging efficiency, and decision latency in foraging bumble bees. We find that our environmental traits uniquely affect each of these behavioral variables, revealing the intricate, yet biologically significant ways that co-occurring environmental traits can affect behavior. Floral selectivity, but not foraging efficiency, is increased by a greater number of choices. Decision latency is greatest when bees are inexperienced foraging in environments with high choice number. Collectively taken, we argue that these results suggest a cost to deciding among many choices, which promotes choice fidelity when many options are present. We suggest that these results have implications for theory on decision-making and selection in biological markets, while demonstrating the importance of studying interactions between naturally co-occurring traits. Nature is comprised of complex, co-occurring traits. We show that floral traits affect bumble bee decision-making based on how they co-occur. Specifically, we examined how flower number, signal complexity, and nectar reliability affect which flowers bumble bees choose to feed from. Our results show that all of these traits significantly affect bumble bee decision-making. Notably, our results suggest that bumble bees experience a cost to decision-making when many flowers are present.