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In their natural environments, most animals must learn about multiple kinds of rewards, both within and across contexts. Despite this, the majority of research on animal learning involves a single reward type. For example, bees are an important model system for the study of cognition and its ecological consequences, but nearly all research to date on their learning concerns a single reward, nectar (carbohydrates), even though foragers often simultaneously collect pollen (protein). Features of learning under more ecologically realistic conditions involving multiple reward types are thus largely unexplored. To address this gap, we compared performance on a colour-learning task when floral surrogates offered bumblebees, Bombus impatiens , a single type of floral reward versus multiple, nutritionally distinct rewards. In one experiment, bees learned a floral association with nectar either alone or while simultaneously collecting pollen. In a reciprocal experiment, bees learned a floral association with pollen either alone or while simultaneously collecting nectar. Bees that collected pollen while learning about nectar did not suffer any detriment to learning which flower colour offered nectar. However, this was not the case for the reciprocal task: collecting nectar impaired bees' ability to learn and remember associations between floral colour and pollen. Our findings offer new insight into how bees learn in relation to ecologically realistic rewards and how cognitive constraints may shape their behaviour under ecologically realistic foraging scenarios. [ABSTRACT FROM AUTHOR]

Ever since Karl von Frisch's Nobel Prize-winning work in the early 1900s, bees have served as an important model system for the study of learning, memory and foraging behaviour. Bees can learn about floral features including colour, scent, texture and electrostatic charge, and show surprisingly sophisticated forms of learning. However, nearly every study of bee cognition and foraging to date has used a sole reward: nectar, most often in the form of a simple sucrose solution. Plants also offer a number of other rewards to pollinators, the most prevalent being pollen that bees collect as their primary source of protein. Indeed, a significant proportion of angiosperm species are nectarless, rewarding bees with pollen alone. Surprisingly, whether free-flying bees can learn visual features based solely on floral pollen rewards is unknown. Here we show that bees can learn to associate multiple floral features with a pure pollen reward. Furthermore, these associations are remembered long term, comparable to bees' memory for nectar associations. These findings raise new questions about bee learning and the evolutionary history between plants and bee pollinators. [ABSTRACT FROM AUTHOR]