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[photo: Biotechnology and Biological Sciences Research Council/Rothamsted Research]

Decoding Bees' Wild Waggle Dances
By Wendy M. Grossman, Wired News
Story location: http://www.wired.com/news/technology/0,1282,67494,00.html
02:00 AM May. 13, 2005 PT

A team of British scientists tracked honeybees by radar to solve an enduring controversy in zoology: whether bees communicate the source of food to each other by performing a waggle dance.

In the 1960s, Nobel Prize-winning Austrian zoologist Karl von Frisch proposed that bees use a coded dance to indicate the direction, distance and type of food to hive mates.

But although indirect evidence has supported von Frisch's theory, it has never been tested directly.

Bees certainly dance, but there is typically a time lag between performance of the dance and other bees' arrival at the food source. The time lag led scientists to suggest that the bees were actually finding the food on their own, possibly by following a scent or the original bee when it returned to the food source.

But now a team at Rothamsted Research, an agricultural research center, has tracked bees by radar as they flew to a food source.

"We've solved it for once and for all," said professor Joe Riley, the team leader.

After finding food, scout bees returning to the hive dance on the vertical walls of the honeycomb. A round dance indicates the food is very close, within 35 yards or less. A figure-eight pattern indicates that the food is farther away. The bee indicates the distance to the food by how long it dances; it indicates the food's richness by how vigorously it dances; and it indicates the food's direction by the angle the dance deviates from an imaginary line drawn from the current position of the sun to the dance floor. The code is complex and detailed.

The controversy, said Riley, was created by von Frisch himself when he said that recruits read the dance and flew directly to the food source.

But "they take five to 10 minutes, not one minute," said Riley.

Because of this discrepancy, opponents like Adrian Wenner have suggested that while the bees dance, it's not to convey information. Instead, he said bees are guided to the food source by odor conveyed by the scout bee.

Riley's team members have worked with radar tracking since 1996, when they were trying to help a British aid program in Zimbabwe control tsetse flies.

The team's results show that bees do read the dance and fly off immediately in the direction indicated. In addition, the bees correct for wind drift by looking at the ground and the angle of the sun and correcting any lateral shift.

But "they very rarely get it absolutely right," said Riley. "The mean error is about 5 to 6 meters."

Once the bees get to the end of the flight, they change their flight pattern and start circling, looking for the food they've been instructed to find. That takes time, Riley said, and bees can loop back and forth for up to 20 minutes.

"This is where the missing time went," said Riley.

When they near their destination, bees use odor to help find the food source. To make sure bees weren't following a scent, a control group of bees was transported 250 meters after seeing a waggle dance. When released, the bees flew off in the direction indicated by the dance, the team found.

To track bees by radar, the researchers first had to create a transponder small and light enough that a bee could carry it. It took approximately two years, Riley said, to come up with a system that worked efficiently and was small enough for the insect to carry. It had to be omnidirectional, and robust enough to survive being attached to the insect and to stay on during grooming. The final version weighs approximately 10 to 12 milligrams, a fraction of the pollen load bees are accustomed to carrying.

The final product, he said, "looks like a whisker with a lump in the middle" and is essentially a nonlinear antenna made of steel wire with a small chip in the middle. To attach the transponders to the bees, handlers stick them to the insects' backs as they leave the hive.

Once the bees are airborne, they are tracked by radar just the way you see in old movies: dots on a screen that are recorded and later converted to graphs. Because there are no batteries small enough to power them, the transponders derive power from the 20-kilowatt signal the radar sends out, replying with a new signal that identifies each transponder uniquely.

The work was published May 12 in Nature.

"It's a wonderful paper because the results are so clear and they did some very nifty controls," said Thomas Seeley, a biology professor at Cornell who peer-reviewed the paper for Nature.

But questions remain, said Seeley. "We don't know yet how a bee standing next to a dancer in the darkness of a beehive is able to get all this information from the dancer," he said. "And we also don't know how it evolved."