Bumblebees’ food preferences are jointly shaped by rapid valuation of nectar sugar concentration and viscosity

Animals are often assumed to follow a strategy of energy maximisation, and therefore should evaluate feeding options based on energy intake rates. Contrastingly, rhesus macaque’s learned food preferences are based on sensory properties, e.g. sweetness and resistance, regardless of energy differences. Here, we show that nectar sugar concentration (sweetness) and nectar viscosity (resistance) drive preferences of bumblebees, classical models for economic and foraging decision-making. Using a tasteless/odourless biopolymer (tylose), we created feeding options that differed in sweetness and resistance, properties that affect energy intake rate and can be immediately sensed. When energy intake rates were similar, bumblebees developed preferences based on sweetness and resistance. When energy intake rates were different but sweetness and resistance were balanced against each other, bees developed no preferences. Decision dynamics during training indicated that bumblebees simultaneously evalua..., ,