Social Foraging by Honeybees: How a Colony Tracks Rich Sources of Nectar

Abstract

This paper examines how the behavioral acts of the thousands of foragers in a honeybee colony are combined to produce the coordinated foraging behavior of a whole colony. We focus on a colony’s ability to quickly adjust the distribution of its foraging efforts following changes in the spatial distribution of rich nectar sources. The analysis begins by examining the factors that influence an individual nectar forager’s response to a patch of flowers (Fig. 1). These include variables, such as distance from the nest, nectar sweetness, and nectar abundance (Fig. 4), that are associated with the patch itself, as well as variables, such as weather conditions and the colony’s rate of nectar intake (Fig. 2), that are not associated with a particular patch of flowers. These non-patch variables affect a forager’s response to her patch of flowers by changing her thresholds in patch quality for abandoning or recruiting nestmates to a patch (Fig. 3). Foragers evidently assess their colony’s rate of nectar intake while unloading nectar to receiver bees. The ease of unloading varies inversely with the rate of nectar flow into the colony. The responsiveness of nectar foragers to this indicator of their colony’s foraging status enables a colony to swiftly redirect its nectar collection efforts following changes in the spatial distribution of rich nectar sources. Whenever the quality of a major nectar source declines, its foragers reduce their rate of visits to the patch, which depresses the colony’s total rate of nectar intake, which in turn stimulates recruitment to whichever patches remain high in quality (Figs. 6 and 7). The paper concludes by presenting some generalizations about colony integration in social insects that emerge from this research.