Bumblebees occupy: when foragers do and do not use the presence of others to first find food

The aim of this study was to determine whether an unlearned preference by bumblebees for flowers that are occupied by other bees is frequency dependent and whether it depends on the size of the flower. In three experiments, bees leaving their colony for the first time were given 20 unrewarded choices of occupied versus unoccupied floral patterns in a radial arm maze. In Experiment 1, the relative frequency of occupiers was manipulated. In Experiment 2, a variety of large (≥6 cm diameter) artificial flowers was used. In Experiment 3, floral patterns were eliminated in an effort to reduce the similarity between “occupied” and “unoccupied”. A significant unlearned preference was found only under the combination of conditions in which occupied flowers were comparatively rare and the occupier to flower size ratio was relatively high. Otherwise, the preferences were non-significant, though the stimuli were discriminable because control groups given prior discrimination training acquired a preference. Our results narrow down the conditions under which foragers respond to the presence of others when making their first floral choices.