Bees: Caffeine Lovers, Just Like You And Me

Many people like a cup of coffee in the morning to help them get going, and apparently they're not alone. Human beings may not be the only species with a need for a bit of caffeine to get their day kicked off.

Researchers from the University of Sussex and the University of Bern have discovered that bees appear to be just as addicted to caffeine as the average college student - and the flowers they pollinate may be taking advantage of that addiction, by lacing their nectar with caffeine in order to be pollinated more frequently.

"We describe a novel way in which some plants, through the action of a secondary compound like caffeine that is present in nectar, may be tricking the honey bee by securing loyal and faithful foraging and recruitment behaviors, perhaps without providing the best quality forage," said Margaret Couvillon, of the University of Sussex.

Couvillon noted that many flowering plants naturally lace their nectar with caffeine in low concentrations.

Published in Current Biology, the study tested bees' responses to two types of sugary solutions (to act as forage), one with field-realistic doses of caffeine and one without, placed in feeders. The results showed that the bees with caffeine in their systems foraged more often and longer. The bees who had accessed the caffeine would then direct additional bees to the caffeinated forage more and more frequently.

The caffeine actually quadrupled the amount of recruitment dances to the feeders with caffeine, compared to the amount being recruited to the non-caffeinated feeders.

"The effect of caffeine is akin to drugging, where the honey bees are tricked into valuing the forage as a higher quality than it really is," Roger Schürch, of both universities, said. "The duped pollinators forage and recruit accordingly."

Earlier studies have shown that honey bees are better at remembering old scents and learning new ones when they are under the influence of caffeine, which suggested the role that reward pathways in bees' brains plays is quite significant in their production.

The bees were much more persistent about returning to sites with caffeine, even when those feeders' supply had run dry, according to a news release. The bees also showed that after ingesting the caffeine, they were less inclined to search for other resources of forage, which would be useful to the plants they pollinate.

"We were surprised at how, across the board, we saw an effect of caffeine just about everywhere we looked in foraging and recruitment, and all in the direction to make the colony more faithful to the caffeinated source compared to an equal-quality, uncaffeinated source," Schürch said.

The team concluded that access to caffeinated nectar may reduce the honey production in bee colonies if the sweetness of the nectar is reduced as a result of the introduction of that secondary compound, caffeine. The possibility that additional compounds make the nectar more bitter reminded the researchers that the goals of pollinator and plant don't always match up.

Couvillon noted that since plants can have more than one secondary compound in their nectar, it would be interesting to see the effects of other ones, explaining that "it may be that chemistry is a popular way in which plants can get the upper hand on their pollinators."

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