Do bumble bees save time when choosing novel flowers by following conspecifics?

1. Spatio-temporal variation in resource availability is often large and unpredictable. When animals need to find and sample novel foods, therefore they may prefer to choose food sources with feeding conspecifics or odour left by the conspecifics. This behaviour (local enhancement) would be favoured, especially if it decreases the time spent on food-finding and subsequent decision-making. In laboratory experiments we tested if naive bumble bees use local enhancement, and to what degree it could reduce the time spent on finding and sampling novel flowers. 2. When naive bees were presented with a pair of equally rewarded artificial or real flowers in a flight cage, they preferred to land and feed on the flower where a dead conspecific was attached. The presence of conspecifics reduced the time spent on detecting floral reward, which was significant only when bees chose between real flowers. In a similar pairwise choice, bees landed on artificial flowers with a dead conspecific wrapped in plastic more frequently than on flowers with the same-sized plastic wrap including no bees, which suggests that visual cues have important influences on the bees' flower choice. 3. Effects of conspecifics on flower choice and food detection time were most evident when they were attached to real flowers, and least evident when they were wrapped in plastic. These results suggest that the presence of conspecifics on flowers has stronger effects on bees' decision-making as the attractiveness of flowers increases, and that bees use both visual and non-visual cues to recognize conspecifics on flowers. 4. If the benefit of saving time were universal, the use of local enhancement would also be advantageous when bees switch between focal flower species or sites in response to temporal changes in resource availability.