The Caffinated Lives of Bees
Caffeine improves learning and memory in bees, as it does in people. Scientists know that. But, one might wonder, what do these laboratory findings mean in terms of the actual lives of bees? It’s not as if a flower meadow is sprinkled with coffee shops.
Except that it is, in a way. Up to 55 percent of flowering plants are estimated to have caffeinated nectar. So any meadow or forest is going to have lots of places to stop by for a jolt.
Margaret J. Couvillon of the University of Sussex, who studies the behavior of honeybees, wanted to see how caffeine affected bees’ behavior.
What she found was that bees were drawn to caffeine like office workers to a coffee cart and that the favorite drug of so many human beings changed how bees evaluated nectar quality.
As they reported in the journal Current Biology Dr. Couvillon and her colleagues at the university, including Roger Schurch (her husband) and Francis L. W. Ratnieks, trained two groups of bees to go to two different feeders. They were filled with the same nectar, but one had caffeine in about the same concentrations common in flowers.
The caffeinated bees visited their feeder more often than the other bees. They were more loyal to their feeder. And they persisted in coming to the feeder for days after it was emptied, which the other bees did not.
And they danced up a storm. Honeybees communicate with the rest of the hive about the sources of nectar they’ve found by shaking their abdomens in what is called the waggle dance. They don’t always dance; it depends on how good the nectar source is.
The bees that sipped high-test nectar were more likely to dance than the ones who were drinking decaf. And they repeated their abdomen shaking routine more times — an indication of how much sugar — and therefore calories — the nectar contained.
But the caffeinated nectar was not nutritionally better than the plain nectar. In effect, Dr. Couvillon said, caffeine “causes the bee to overestimate the quality of the resource.”
It makes sense that plants would evolve to lace their nectar with caffeine. It seems that it would increase bee visits — the more bee visits, the more pollen carried around and the better the plants’ chances of reproduction.
But caffeine doesn’t seem to offer much to the bees other than a nice little buzz. In nature, that means they might stick to caffeine-laced nectar and miss out on other sources that are as good or better, Dr. Couvillon said.
Bees and flowers get something out of their ancient relationship. But, she said, “As with many partnerships, the interests don’t always align.” Some bees chew at the base of a flower to get nectar without having to load themselves up with pollen that they have to carry around as they fly.
“There’s always a little arms race going on,” she said.
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