Bumblebees Show Spontaneous Problem-Solving, Rolling Balls to Reach Reward
A study published in the journal Science reports that bumblebees (Bombus terrestris) were observed rolling a ball to a specific location and using it as a platform to access a sugar water reward in a controlled laboratory setting. The experiments were conducted by researchers at the University of Oulu and the University of Turku in Finland.
Experimental Design
Researchers constructed a circular arena (10 cm in diameter, 3.2 cm tall) where bees could walk but not fly. An artificial blue flower containing a sugar solution was placed on the ceiling of the chamber, at a height that was too high for the bees to reach while standing but too low for them to hover and fly to. A small polystyrene or plastic foam ball was placed in the arena.
The experiment consisted of three sequential scenarios:
- Scenario 1: Bees explored a blue flower with a sugar solution placed near a foam ball to reduce neophobia (fear of new objects).
- Scenario 2: The ball was placed covering the flower; bees learned to push it away to access the reward.
- Scenario 3: The flower was placed on the ceiling above a pit. The bees had to roll the ball into the correct pit and climb onto it to reach the flower.
Results
Seventy-five percent of bees that had experienced the first two scenarios successfully rolled the ball into the correct pit and climbed onto it to reach the flower in the third scenario. Bees that had not been exposed to both the ball and the flower reward association could not solve the task.
In a more complex version of the experiment, researchers allowed bees to explore two chambers, one containing the flower. The flower was then removed and a ball was introduced under red light, which obscured the visual cue of the flower's location. Twenty-three out of 30 bees successfully rolled the ball to the remembered location of the flower.
Control experiments demonstrated that bees could move the ball toward the flower's location even when the flower was not visible from the ball's starting position.
Interpretation and Significance
The researchers described the bees' behavior as "spontaneous problem-solving," a form of behavior that has previously been observed in great apes, elephants, and some birds. The study suggests that the insects were "truly naive" to the task—meaning they had no prior experience with similar problems—ruling out innate behavior or prior learning as explanations for their success.
"The bees must realise that an object can be repositioned and then used as a tool to reach an otherwise inaccessible goal."
— Senior author Dr. Olli Loukola
Dr. Loukola added that the high success rate indicates "very tiny brains can solve super complex problems."
The authors did not categorize the behavior as "tool use," as the term remains debated in animal behavior research. The findings challenge assumptions that insects operate solely on instinct and trial-and-error learning, suggesting that miniature brains can generate flexible solutions to novel problems.
External Commentary
James Nieh (University of California San Diego), who was not involved in the study, stated that while bees do not normally move objects to make platforms, the experiment shows they can "remember a hidden goal location and manipulate an object in relation to that goal."
Lars Chittka (Queen Mary University of London) noted that the bees' performance was impressive because in some tests they could not see the target when moving the ball, requiring "understanding of the task and memory of the goal."
Natalie Hempel de Ibarra (University of Exeter) commented that such flexibility could help bees cope with changing environments.
Primatologist Cat Hobaiter, also not involved in the study, stated that "intelligent brains come in really diverse shapes and sizes."
Background
The experiment is based on a classic 1917 study by Wolfgang Köhler, in which a chimpanzee stacked boxes to reach a banana. Similar tasks have since been performed by birds and elephants. The researchers had previously shown that bumblebees can learn tool use and cooperate.