Bumblebees surprise scientists by showing a sense of rhythm

Bumblebees have demonstrated the ability to identify Morse code-like sequences of flashing lights and vibrations, revealing a rhythmic understanding previously unseen in animals with small brains.

Recognizing flexible, abstract rhythms—such as when the same pattern or melody is played at various tempos—has only been observed in certain birds and mammals, including parrots, songbirds, and primates like chimpanzees.

Andrew Barron at Macquarie University in Sydney, Australia, and his team conducted a series of experiments to investigate whether buff-tailed bumblebees (Bombus terrestris), with their less complex brains, could also discern a variety of rhythms.

In their initial experiment, bumblebees were trained to choose between two artificial flowers with flashing LED lights. One flower emitted long flashes, while the other produced short pulses, resembling Morse code dashes and dots. One flower contained sucrose as a reward, while the other held unpalatable quinine.

After learning to differentiate between the rewarding and punishing flashing flowers, the bees were presented with flowers containing only water. Almost all the bees still opted for the flower with the flash pattern that previously contained sucrose.

Subsequently, the researchers increased the complexity of the light patterns, with each flower displaying a different flash sequence—either dash dash dot dot or dot dash dot dash. The bees successfully distinguished between these patterns.

The most remarkable result, according to Barron, occurred when the artificial flowers were replaced with a maze. At a junction between two paths, a vibrating floor was introduced.

“If it was vibrating dot dash dot dash, it meant turn right to get sugar,” Barron explains. “One rhythm indicated to turn left, the other to turn right, and we trained them accordingly. We demonstrated that they could learn this.”

Finally, without additional training, the vibrating floor was swapped out for LED lights flashing in the same pattern. “Not all bees understood, but overall, the population showed the ability to transfer the task from vibration to light pulses,” Barron says.

This means the bees could recognize a pattern regardless of its presentation form—whether through light or vibration, they identified the rhythms.

Until now, it was believed that abstract rhythm recognition required larger brains, Barron notes. Understanding how bees achieve this with their small brains could transform how miniature drones and other compact autonomous devices perceive the world.

“I think what this research indicates is that there must be a simpler method,” Barron concludes. “The fact that a bee, with a bee-sized brain, is capable of abstracting a rhythm is extraordinary.”