Social insects like bees demonstrate a remarkable range of behaviors, from working together to build structurally complex nests (complete with built-in climate control) to the pragmatic division of labor within their communities. Biologists have traditionally viewed these behaviors as pre-programmed responses that evolved over generations in response to external factors. But two papers last week reported results indicating that social learning might also play a role.

The first, published in the journal PLoS Biology, demonstrated that bumblebees could learn to solve simple puzzles by watching more experienced peers. The second, published in the journal Science, reported evidence for similar social learning in how honeybees learn to perform their trademark "waggle dance" to tell other bees in their colony where to find food or other resources. Taken together, both studies add to a growing body of evidence of a kind of "culture" among social insects like bees.

"Culture can be broadly defined as behaviors that are acquired through social learning and are maintained in a population over time, and essentially serves as a 'second form of inheritance,' but most studies have been conducted on species with relatively large brains: primates, cetaceans, and passerine birds," said co-author Alice Bridges, a graduate student at Queen Mary University of London who works in the lab of co-author Lars Chittka. "I wanted to study bumblebees in particular because they are perfect models for social learning experiments. They have previously been shown to be able to learn really complex, novel, non-natural behaviors such as string-pulling both individually and socially."

Ever since Charles Darwin observed bumblebees in 1884 engaged in "nectar robbing"—in which a forager bites into the base of a flower to collect the nectar but doesn't pollinate the plant—scientists have recognized a surprising capacity for social learning in creatures of all kinds. An evolutionary theory called the Baldwin effect says that certain beneficial behavioral traits learned in the lifetime of one creature are passed on to its offspring via natural selection. So Bridges et al. decided to explore the possibility that social learning might have contributed to unique behavioral innovations in bumblebees (Bombus terrestris), rather than being purely instinctive.

As we reported previously, Chittka's group conducted a 2017 study in which it showed that bees could be trained to roll little wooden balls in order to receive a reward. But the group also noticed instances where the bees opted to roll the balls even when there wasn't an obvious reward or benefit. The balls had been placed in a tunnel that connected the hive to the experimental arena where the food was. Several bees walked over the balls or stopped to roll them on their way back and forth from the food. The group wondered if this might be genuine play behavior.

Chittka's lab published a follow-up study last year reporting its observations of genuine play behavior in bees, which were filmed rolling small colored wooden balls. (While many animals are known to engage in play, they are usually large-brained mammals and birds.) For Chittka, this was “a strong indication that insect minds are far more sophisticated than we might imagine."

The idea to use two-option puzzle box experiments to explore social learning came from prior research on chimpanzees (2005) and great tits (2015). For the bees, the Chittka lab designed puzzle boxes that could be opened by rotating a clear lid, either by pushing clockwise on a red tab or counter-clockwise on a blue tab. This would let the bees collect a tasty reward of 50 percent sucrose solution.