Elevated temperatures shape cognitive performance and foraging preferences in free-flying bumblebees

Abstract Despite concerns about global warming on pollination services, its impact on pollinator cognition and foraging remains underexplored. We investigated how short-term heat exposure influences learning and foraging preferences of free-flying bumblebees. Bees foraging at 32°C or 24°C were presented with yellow and blue artificial flowers associated with sugar solution (rewarding) and an alternative—water (neutral) or quinine (aversive). During the initial trials with an aversive alternative to the positively conditioned stimulus (CS+), bees at 24°C learnt at a faster rate than at 32°C, but the overall proportion of bees that learnt was higher at 32°C. This indicates that elevated temperature may impair the time required for bees to learn to associate a sugar reward with a coloured stimulus. However, by the end of the trials, temperature had no negative effect on the overall proportion of bees that learnt to associate flower colour with sugar solution. Moreover, we discovered that bumblebees foraging in warmer conditions exhibited a preference for water already in their initial floral visits. The findings of this study suggest that rising environmental temperatures may affect the foraging behaviour and floral preference of insect pollinators, but on-field studies are required to assess if it could impact the ecosystem services they provide.