Turns out bees like a jolt of caffeine as much as humans do, and some flowers have souped up their nectar with the stimulant to keep bees coming back for more.
While the caffeine in flowers is intended primarily as a bitter-tasting defense against marauding plant-eating insects like caterpillars, researchers have found bees are capable of developing a taste — maybe even an addiction — for it.
Bees might even go for an inferior quality of nectar if it contains caffeine, they suggest, letting some flowers get away with attracting bees even if their nectar is of lesser quality.
That's because it is likely easier for the plant and its flowers to produce a small amount of caffeine than a large amount of sugar.
"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," says Margaret Couvillon of the University of Sussex in Britain.
Previous studies found that caffeine improved bees' ability to learn and remember certain scents put out by flowers, many of which offer nectar containing low concentrations of caffeine.
In experiments, bees were offered sucrose solutions, some with caffeine and some without.
More bees chose the caffeinated solutions and were more likely to use their waggle dances to direct other foraging bees to the same nectar, the researchers found.
Researchers said they were surprised how long the effect lasted, finding that the bees would continue returning to a feeder that had contained caffeinated sucrose after it was empty.
"We saw that if they just had one, three-hour exposure to the caffeinated nectar on the first day, they would come back [to the empty feeder] for many more days, and more often within each day," Couvillon says.
While the caffeine is particularly harmful to the bees directly, it can make the colony's foraging less efficient, the researchers explain, since, by ignoring identical flowers that lack caffeine, bees are not taking full advantage of all potential food sources.
"If they've had caffeine, they're less likely to check the surrounding area," Couvillon says. "They're really hooked on that location."
