Is culture only reserved for creatures with big brains? One study suggests that bumblebees are also able to learn from each other and culturally transmit learned behaviors within a colony. In the experiment, bumblebees learned to open a puzzle box by observing experienced individuals. Although there was an alternative, equivalent solution, the animals preferred the copied one. This suggests that it was indeed a culturally acquired behavior.
Different social animal species are able to transmit knowledge and behaviors within a community: chimpanzees from different populations each exhibit their own tool-using tactics, songbirds have different dialects, and whales hunt their prey in different ways depending on the population. All these behaviors, which are not innate but socially acquired, are considered signs of culture.
Puzzling bumblebees
“So far, however, research on culture in animals has mainly focused on vertebrates with relatively large brains,” writes a team led by Alice Bridges from Queen Mary University in London. It was previously unclear whether similar phenomena also exist in insects. “Social insects have some of the most fascinating and complex behavioral repertoires that exist, such as the dance language of honey bees and the mushroom cultivation of leafcutter ants,” says Bridges. “However, their brains are only about the size of a pinhead, and many of their behaviors are probably innate. I was curious if some of these behaviors might have evolved through culture-like processes, at least initially.”
To find out whether insects are at least fundamentally capable of culturally transmitting behaviors, Bridges and her team conducted behavioral experiments with ground bumblebees (Bombus terrestris). To do this, they built puzzle boxes that contained a sugar solution on a large yellow dot as a reward. To reach the treat, the bumblebees had to turn the lid of the box either clockwise or counter-clockwise by crawling against one of two tabs on the lid, thereby sliding one of the two openings in the lid over the yellow dot.
Social learning shapes preferences
In a first step, the researchers trained a single bumblebee from a colony to turn the lid counterclockwise. Once this demonstrator bumblebee learned to open the box, Bridges and her team placed this individual with untrained animals in a flight arena with free access to several puzzle boxes. Over a period of six to 12 days, they filmed the bumblebees and observed how they handled the boxes. Two colonies served as controls, which were given access to the puzzle boxes without a trained role model.
The result: If there was a demonstrator bumblebee, the other bumblebees copied the solution to the puzzle from it within a few days and also began to open the box by turning the lid counterclockwise. “Even when some of the animals tried the alternative behavior and realized that the lid could also be opened clockwise, the colony developed a strong preference for the demonstrator bumblebee’s version,” reports Bridges. The same result was seen in experiments where the demonstrator bumblebee learned to turn the lid clockwise. Here, too, the colony followed its path to a solution.
“In control experiments in which no demonstrator was present, some bumblebees opened the puzzle boxes spontaneously, but were significantly less skilled than those that had learned in the presence of a demonstrator,” reports the team. “This indicates that social learning is crucial for the correct opening of the boxes.” If the researchers placed several demonstrator bumblebees, which were trained to rotate in different directions, in a colony, their conspecifics learned to open the box in both ways. In these colonies, too, however, a preference for one of the two solutions developed within a few days.
Culture in the wild?
The results show that ground bumblebees are indeed able to pass on skills through social learning – a prerequisite for culture. However, it is still unclear whether they actually cultivate some kind of culture in the wild. “The life span of the bumble bee worker bees is short and, unlike honey bees, the colonies do not survive the winter,” explains the research team. “Since no workers survive the winter, possible traditions die with them. Therefore, it seems unlikely that ground bumblebees would establish cultures in the wild that outlive biological generations.”
However, given the basic biological ability for cultural transmission, it may be that other bumblebee species that survive the winter may well have traditions that are maintained over several generations. Bridges and her team believe that further studies of cultural behavior in insects could help provide insight into the evolutionary origins of culture.
Source: Alice Bridges (Queen Mary University of London, UK) et al., PLOS Biology, doi: 10.1371/journal.pbio.3002019