This bee seems to having a grand old time rolling this colored wooden ball.
Enlarge / This bee seems to having a grand old time rolling this colored wooden ball.
There's rarely time to write about every cool science-y story that comes our way. So this year, we're once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2020, each day from December 25 through January 5. Today: Scientists captured bees rolling wooden balls, solely for fun, on video, providing additional evidence that bees might experience positive "feelings."

Large-brained mammals and birds are known for engaging in play. According to an October paper published in the journal animal behavior, scientists think they have observed genuine play behavior in bees, which were filmed rolling small colored wooden balls.

The co-author of The Mind of a Bee said that the research provided a strong indication that insect minds are more sophisticated than we think. Young mammals and birds are the most common examples of animals who play just for the sake of fun.

There are three broad categories for play behavior. Social play involves animals playing with one another. There is anecdotal evidence that shows social play among ants and young wasp. Running, jumping, or similar intense and sustained movements are not associated with a specific purpose. An object can be manipulated as a toy.

Chittka's group conducted a previous study in which they showed that bees can be trained to roll wooden balls in order to get a reward. The bees rolled the balls even when there wasn't an obvious benefit. The hive had a tunnel that connected it to the experimental arena. The bees were rolling the balls back and forth from the food. Chittka and his team wondered if this was real play behavior.

It's difficult to design an experiment to show that bees are playing in a specific way. You can't just ask the bees if they're happy. There are five basic criteria.

Bees at play. Credit: Samadi Galpayage

In order to get food, attract a mate, or find shelter, the behavior should not be done. The play behavior should be voluntary and rewarding in and of itself, rather than being associated with a reward. When searching for food or trying to mate, the motor actions should be different. The play behavior is repeated but not stereotyped in order to distinguish between a one-off occurrence and an ongoing habit. When the subject is relaxed, the play should be initiated to distinguish it from stress-related behaviors like pacing or walking.


Chittka and his team followed a similar setup. 45 bees were placed in the arena and given the choice to walk along a straight line or wander off into the woods. Most bees rolled balls for at least one extra day after feeding, with 29 rolling balls for two extra days. The bees rolled balls between 1 and 117 times, with the latter number suggesting at least some of the bees found the activity enjoyable.

42 bees were given access to two chambers, one of which was empty and the other always had wooden balls, in order to determine if this was play. After the balls were removed, the bees were given a choice of which chamber to stay in. They preferred the chamber with a color that was associated with wooden balls. Younger bees roll balls more frequently than older bees, and male bees roll balls longer than females.

The five basic criteria for play were met by the bees in the experiment. Samadi Galpayage is a graduate student in Chittka's lab. They approach and manipulate the toys again and again. It shows once more that they are more than small robotic beings. Even if rudimentary, they may experience some kind of positive emotional states.

There is an animal behavior in the book. About DOIs can be found in the 10.1016/j.anbehav.2022.08.014.