Comparing the behavior of three bee species foraging on alfalfa flowers

An understanding of the foraging behavior of pollinators is necessary before we can link pollinator behavior to gene flow. We examined the behavior of two social bees, honey bee, Apis mellifera, and bumble bee, Bombus impatiens, and a solitary bee, the alfalfa leafcutting bee, Megachile rotundata, foraging on alfalfa flowers. Observers followed a bee as she moved between consecutive racemes during a foraging bout, marked each raceme visited in succession, counted the number of flowers visited per raceme and recorded the distance and direction traveled between successive racemes. Mixed and generalized linear models helped compare the distance and direction traveled between consecutive racemes and the number of flowers visited per raceme among the pollinators. We also examined whether each bee species exhibited directionality of movement within foraging bouts and had an overall preferred direction. Honey bees visited more flowers per raceme and traveled shorter distances to the next raceme relative to the other bee species. Honey bees and bumble bees, but not leaf cutting bees, showed directionality of movement within foraging bouts. Bees foraged differently on alfalfa flowers and such differences must be considered when developing models of pollinator movement and gene flow.