Interindividual variability in flower pickiness by foraging bumblebees

Overview & Synopsis

Pollinators navigate complex and heterogeneous “flower markets”, where floral resources vary in quality, availability, and distribution. Bumblebees, as generalist foragers, visit numerous flowers during their foraging bouts. Yet, the factors influencing their flower choices and the notable individual differences in foraging behaviour among bees are still not well understood. We hypothesised that early foraging experiences influence bees’ subsequent flower choices. To test this, we observed individual Bombus terrestris workers forage for three consecutive bouts in two artificial flower arrays. One array simulated a favourable environment with patches alternating high- and low-quality flowers (40% vs. 20% w/w sucrose solution), while the other array presented a more challenging environment with patches of high-quality flowers alongside unrewarded flowers (40% w/w sucrose solution vs. plain water). In both arrays, bees rapidly improved their foraging efficiency, increasing sucrose intake per unit time across bouts. In the favourable array, most bees became highly selective for high-quality flowers, while some continued visiting both flower types. Their degree of pickiness was influenced by early experiences: bees initially exposed to high-quality flowers became more selective, whereas those encountering low-quality flowers first were less selective in subsequent foraging. Despite differences in pickiness and array conditions, bees achieved comparable sucrose intake rates within three bouts. This study highlights the adaptability of bee foraging behaviour and emphasizes the role of early foraging experiences in driving individual differences. Significance statement To forage efficiently, pollinators must navigate complex “flower markets”, where floral resources vary in quality and availability. We observed Bombus terrestris workers forage across three bouts in two artificial flower arrays: a favourable array with flower patches alternating high- and low-quality flowers (40% vs. 20% w/w sucrose solution), and an extreme array with high-quality and non-rewarding flowers (40% w/w sucrose solution vs. plain water). We found that bees initially exposed to high-quality flowers became highly selective, whereas those encountering low-quality flowers first were less picky, collecting both flower types. Despite these differences, bees rapidly improved foraging efficiency over successive bouts, achieving similar sucrose intake rates within three bouts. This study highlights the foraging flexibility of bumblebees and suggests that early experiences can have lasting effects, influencing flower choices dozens of visits later.