Honeybees learn the sign and magnitude of reward variations

In this study, we asked whether honeybees learn the sign and magnitude of variations in the level of reward. We designed an experiment in which bees first had to forage on a three-flower patch offering variable reward levels, and then search for food at the site in the absence of reward and after a long foraging pause. At the time of training, we presented the bees with a decrease in reward level or, instead, with either a small or a large increase in reward level. Testing took place as soon as they visited the patch on the day following training, when we measured the bees' food-searching behaviours. We found that the bees that had experienced increasing reward levels searched for food more persistently than the bees that had experienced decreasing reward levels, and that the bees that had experienced a large increase in reward level searched for food more persistently than the bees that had experienced a small increase in reward level. Because these differences at the time of testing cannot be accounted for by the bees' previous crop loads and food-intake rates, our results unambiguously demonstrate that honeybees adjust their investment of time/energy during foraging in relation to both the sign and the magnitude of past variations in the level of reward. It is likely that such variations lead to the formation of reward expectations enhancing a forager's reliance on a feeding site. Ultimately, this would make it more likely for honeybees to find food when forage is scarce.