How foraging preference and activity level of bumble bees contribute to colony flexibility under resource demand

Abstract

Groups of cooperative organisms, including humans, benefit from the contributions of both specialist and generalist individuals. Group responses to resource or task demand emerge from the specific actions of individuals within the group. Bumble bee colonies need to respond to resource demands for both pollen and nectar for colony growth and reproduction. Bumble bee workers have been shown to display differences in foraging preferences for these essential resources and in activity level. This study investigated the responses of Bombus terrestris individuals to resource demand by subjecting colonies to different pollen and sucrose storage scenarios, considering their individual foraging preferences and activity levels. The sucrose sensitivity and olfactory learning ability of individuals were then compared along a spectrum of foraging preference (between pollen and sucrose foraging) using the proboscis extension reflex paradigm. When sucrose was in demand, individuals with a preference for sucrose showed the largest upregulation in foraging bouts. Individual preference for pollen and activity level correlated with the upregulation of foraging bouts when pollen was in demand. This study detected no relationship between body size, sucrose preference and worker sucrose sensitivity or olfactory learning ability, tested with proboscis extension reflex conditioning. This study highlights the potential value of foraging preferences in bumble bee colonies but also the flexibility these colonies have with a small foraging workforce. • Bumble bees with high sucrose preference upregulate to fill sucrose demands. • Pollen preference and individual activity level predict upregulation in pollen demand. • Body size and sucrose preference do not predict worker sucrose sensitivity. • Body size and sucrose preference do not predict odour learning performance. • Workload is not evenly split between individuals.