Caffeine is a widely occurring plant defense chemical that occurs in the nectar of some plants, e.g., coffee and citrus, where it may influence pollinator behavior to enhance pollination. New laboratory tests show that buff-tailed bumblebees (Bombus terrestris) locate new food sources emitting a learned floral odor more consistently if they have been fed caffeine.
Feeding bumblebees caffeine helps them better remember the smell of a specific flower with nectar inside. Image credit: Arnold et al., doi: 10.1016/j.cub.2021.06.068.
“When you give bees caffeine, they don’t do anything like fly in loops, but do seem to be more motivated and more efficient,” said Dr. Sarah Arnold, a researcher at the Natural Resources Institute at the University of Greenwich.
“We wanted to see if providing caffeine would help their brains create a positive association between a certain flower odor and a sugar reward.”
Scientists already know that caffeine plays a role in converting bees into faithful customers of caffeinated flowers.
But previous experiments where bees showed a preference for the smell of flowers with caffeinated nectar have mostly been designed to give bees caffeine at the flower itself.
With that setup, it’s difficult to pinpoint the role caffeine plays: do caffeinated bees actually have better memories, or do they just crave the caffeine?
In laboratory arena tests, Dr. Arnold and colleagues fed 86 previously untrained bumblebees a caffeinated food alongside a strawberry odor blend (priming).
They then used robotic experimental flowers to disentangle the effects of caffeine improving memory for learned food-associated cues versus caffeine as a reward.
Inexperienced bumblebees primed with caffeine made more initial visits to target robotic flowers emitting the target odor compared to control insects or those primed with odor alone.
Caffeine-primed bumblebees tended to improve their floral handling time faster.
“These findings have big implications for agriculture,” Dr. Arnold said.
“Strawberry farmers are buying several dozen, or perhaps hundreds, of boxes of commercial bumblebees every year — many of which may stray toward neighboring wildflowers instead of the intended strawberries.”
“But by teaching the bumblebees to prefer the crop with caffeine, we leave wildflower resources for the wild bumblebees, and the growers are getting more value for their money spent on the nests. It’s a win-win solution for everybody.”
The team’s results were published in the journal Current Biology.
Sarah E.J. Arnold et al. Bumble bees show an induced preference for flowers when primed with caffeinated nectar and a target floral odor. Current Biology, published online July 28, 2021; doi: 10.1016/j.cub.2021.06.068