The Why Files The Why Files --

Eat, drink and bee merry
7 JUL 2005

Eat, drink and bee merry
You walk into a restaurant and belly up to the buffet, but nothing looks familiar. Then you spot your dear Aunt Anne shoveling an indecent mound of strawberry pudding into her bowl. Without a word, you follow her lead. It's a pretty safe strategy if you know that Aunt Anne likes the same kind of food as you.

2 bees drink liquid from tiny cup, in the middle of a blue discBumblebees forage on an artificial flower. Among unfamiliar flowers, bees tend to copy other bees that have already chosen a flower. The phony flowers eliminated the effect of scent in the experiment. Courtesy Nicole Milligan

But you wouldn't bother following her lead if the buffet had familiar food. In that case, you could make an informed choice based on experience.

It turns out that bumblebees use the same strategy when choosing flowers to gather nectar. And just like you, they only use this strategy when confronted with unfamiliar food.

That's the word from Ellouise Leadbeater, a biology Ph.D. student at Queen Mary College, University of London, who published a study in the current Current Biology. Leadbeater had heard that bees, when confronting a gastronomical dilemma over unfamiliar flowers, prefer flowers already occupied by other bees. Nobody had studied the phenomenon, she told us, "But there was a lot of anecdotal evidence. People noticed that bees land on the same flower."

Bumblebees are a widespread group of bees that establish colonies with about 80 to 100 workers -- far smaller than honeybee colonies. Queens hatch all the other bees, which become workers, which gather nectar and pollen, or male drones, which live to fertilize queens.

diagram of enclosed box with flowers. Tube coming out, leads to nestboxLeadbeater, working with Lars Chittka, a behavioral ecologist at Queen Mary College, populated a box with phony flowers in two colors. The plastic flowers had no scent, which helps determine bee behavior, and each one carried the same amount of nectar.

This experimental setup allowed scientists to see how bees choose flowers for collecting nectar. Courtesy Current Biology

Then Leadbeater released two bees, first the "demonstrator," then the "observer." If the observer bee had already taken nectar from the color of flower in the enclosure, it usually visited the familiar flower. But if both types of flower were new to it, the observer bee usually visited the flower where the demonstrator was collecting nectar.

chart shows when bees have a demonstrator, they follow them to unfamiliar flowersData from "A New Mode of Information..."

Follow the leader
Remember our encounter with Aunt Anne at the buffet? An observer who was familiar with the food usually chose that food. If the food was unfamiliar, but a member of the same species (a conspecific) was present, the observer followed the conspecific's lead.

And like a ravenous runner suddenly loosed on a bounteous buffet, the bees dug right in, Leadbeater said. "Most bees came out of the nest and flew straight to the flower that the conspecific was on." If neither a familiar flower nor another bee was present, she said, "They fly around, then tend to go for the one they are known to prefer, based on color." (Bees in the tested species generally prefer blue flowers.)

Since both the observer and demonstrator bees are from the same species ( Bombus terrestris), at this point Leadbeater has only proven that one species of bumblebee takes "advice" from its own species. In a new experiment, however, she's starting to see signs that the phenomenon is more widespread. Early observations of the Japanese bee suggest that observers also tend to follow the lead of the demonstrator.

It may be too fancy to call this arthropod emulation, but it's intriguing. Leadbeater says the experiment could be expanded in several other directions:

Do bees follow conspecifics in the wild, as they do in the lab?

Are bees born with this trait, or must they learn it?

Does this type of intelligent foraging help bumblebees gather nectar more efficiently?

What signal does the observer bee receive?

The nature of the signal is critical, Leadbeater says. "We don't know if it's visual or chemical communication. Obviously, bees are very scent-oriented animals." For example, she says, bumblebees often avoid flowers carrying a scent from a previous forager, so they don't waste energy visiting empty flowers. It's possible that the demonstrator bee is releasing a foraging pheromone. This chemical is released by successful foragers after they return to the hive, to encourage worker bees to starting flapping their wings and find some food.

closeup of 3 bees on bright orange and yellow painting
Flowers didn't evolve their stunning colors to please people -- but they probably did to attract bees and other pollinators. Here, bees investigate a reproduction of Sunflowers, a painting by Vincent Van Gogh. Courtesy Lars Chittka and Julian Walker

As she plans experiments to settle the sight or scent question, Leadbeater says," We suspect it could be a combination of vision and scent."

While this is the first study showing that bees emulate other bees while among unfamiliar flowers, it's common for animals to inform conspecifics about food. Norway rats, for example, copy the food choices of other rats by "smelling what food the rat has been eating on its breath," says Leadbeater.

Aunt Anne wouldn't approve. She flossed her teeth every night. Plus, she loathed rats!

-- David Tenenbaumtiny bee looks at writer's name

- A New Mode of Information Transfer in Foraging Bumblebees? Leadbeater E., and Chittka, L. Current Biology, Vol. 15, R447-R448, June 21, 2005.
- Bees relate to the flowers of Van Gogh!
- Animal Communication Project

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