Bumblebees Have Bad Memories, but They Still Use Them

Bumblebees have to make lots of decisions every day. They constantly must choose which flowers to visit in order to harvest the most nectar and pollen.

But they don’t have the best memories and can’t actually remember which blooms offered the best bounty. Their memories aren’t great, new research finds, but bumblebees still rely on them when foraging.

Researchers were intrigued by a study focused on the memories of European starlings. The findings showed that the birds are like people in that they use absolute and comparative information when making decisions. Absolute information is something like the size of a reward or how long it takes to get a reward. Comparative information is whether one option is better than another.

“That made us wonder whether that was the case for bees,” co-lead author Yonghe Zhou, a Ph.D. student at Queen Mary University of London, tells Treehugger.

“Bees have to make tons of decisions between lots of different flowers in their daily foraging trips. I thought it would be really interesting to see what kind of information bees store in their tiny brains during short visits to each flower to solve a type of problem that they and we are often confronted with.”

Studying How Choices Are Made

For their study, researchers designed a series of experiments to analyze how bees hold on to information. They presented bees with two artificial flowers of different colors, each with a different concentration of sucrose solution on the flowers. During training, the bees foraged on the flowers and learned that each color was associated with a particular concentration of the sweet solution.

“Usually, bees land more on the flowers that they prefer, so we tested which flowers they prefer by looking at which flower type they landed on the most,” Zhou says.

They found that bumblebees only had very basic memories for the flowers they visited. They could only remember that a flower had been better or worse than others. They only recalled for a few minutes how rewarding a flower was or how much sweeter it was compared to other flowers.

The results showed that bumblebee memories are quite different from those of birds and humans. 

“Our study shows that bumblebees can only make use of comparative information, and more specifically, ordinal ranking information, which means they can only remember that an option was better or worse, but not even how much better or worse,” Zhou says.

The results were published in the journal eLife.

Successful Strategies

Despite their poor ability to retain information, bumblebees still succeed in finding the best flowers.

“Our research sheds light on a fundamental difference in decision-making strategies between bumblebees and humans, illustrating that completely different strategies can be successful for survival in one’s own environmental niche,” Zhou says.

“Studying such differences between bees and other species can help us realise how cognition has evolved and how such limited neural architectures, i.e. the tiny brains of bumblebees, are able to successfully approach problems we all face.”