FLEXIBLE FORAGING BY BUMBLEBEES ON FLOWERS OFFERING POLLEN AND NECTAR

Abstract

Pollen and nectar are the two most common floral rewards, and bees must collect both. Many plant species offer both rewards to bees; however, reward availability on such flowers varies. Pollen and nectar availability is constantly changing, and bees must be able to adapt to the various environments they encounter. Yet little is known about how bees partition the collection of resources on these flowers. Here I investigate how bees behave on flowers offering both nectar and pollen, and how this behavior shifts depending on reward presence. To do this I tested bumblebee workers, Bombus impatiens, on arrays of Orange Jubilee (Tecoma x alata) flowers. Bees were assigned to either a treatment with intact nectar and pollen rewards, or a treatment with depleted nectar and intact pollen rewards. I found that bees were reward generalists, collecting both pollen and nectar, often on the same flower visit. I also found that bees made fewer attempts to collect nectar and only collected pollen when nectar rewards were depleted. This strategy, which has not previously been described, likely promotes foraging efficiency by reducing time wasted searching and failing to find nectar. This work suggests that individual bees are able to adapt rapidly to changing reward environments in order to maximize collection of available rewards.