Bumblebees’ flexibility is in focus

The research used a series of specially designed tasks to test how the insects explore unfamiliar environments, recognise colours and learn to earn rewards.

The study, which was supported by Chester and Newcastle universities and Toyota UK, examined how the different roles of female workers and male drones influence their behaviour.

While previous research has established bees as a highly intelligent species capable of complex learning, most studies have largely focused on female bees. The researchers compared male and female bumblebees’ active time in a novel environment, using an ‘activity’ task as well as their ability to learn to associate a colour with a reward of sucrose, in a colour learning task.

Researchers also examined the bees’ behavioural flexibility with a final task by reversing the colour that led to a reward.

To do this, the team developed a series of experiments using large, rectangular-shaped boxes with 10 equally divided compartments.

Each compartment had a hole in the middle of the wall separating it from the next meaning the bees were free to visit any compartment, with the time from entry to exit recorded.

Next, shutters between compartments were added, and bees were presented with pairs of artificial flowers — one blue and one yellow.

Bees learned which colour was linked to a sucrose reward, with shutters opening only after a correct choice was made. In the final stage, the rewarded flower colour was reversed to test how quickly bees could adapt to the change.

The tests revealed males spent more time actively exploring unfamiliar environments than females. While both sexes performed similarly when learning the initial colour-reward association, males demonstrated enhanced behavioural flexibility when the colour changed.

Dr Théo Robert, co-author of the study, said: “The difference in learning flexibility between males and females is especially interesting, as it likely reflects differences in their foraging strategies. Because female workers have the support of their colony in the form of food stores, they can probably afford to undertake foraging trips and regularly revisit the highest-quality flowers in their environment, even when those flowers are temporarily depleted or heavily used by other pollinators.

"Their reluctance to switch to new flowers immediately may actually be profitable for the colony in the long term.

“On the other hand, as males’ main role is reproduction, they do not need to compete for the best flowers but simply to sustain themselves long enough to mate with virgin queens.

"Therefore, it may be more profitable for them to switch to different flowers when those on which they have previously learned to feed become depleted.”

Psychologist Dr Pizza Ka Yee Chow said sex role differences can influence ecological and evolutionarily important traits like activity level and behavioural flexibility.

She said in bumblebees, female workers are the main foragers for the colony, whereas drones have minimal responsibility. However, males become solitary foragers once they leave the colony.

Dr Chow added: “Males’ active time may reflect their exploratory behaviour such as pre-mating patrolling, and their enhanced flexibility suggests their readiness to find new profitable flowers when exploited flowers decrease in quality.

"These results highlight the importance of these behavioural and cognitive traits for males, which may increase their chance of finding mates and improve their foraging efficiency.

“They indicate that increased activity level and behavioural flexibility are, therefore, crucial for their survival.”

Dr Chow added the findings highlight the need for broader assessments of additional ecologically and evolutionarily important traits that may vary between sexes with different roles, particularly given that males’ cognition has often been overlooked.

The research paper has recently been published in Animal Cognition.