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Bees Found to Swarm to Same Plants

Bumblebees, believed to be loners in foraging for food, are shown to rely on one another's leads in choosing nectar.

June 25, 2005|Brad Wible | Times Staff Writer

Bumblebees act like copycats, following another bee's lead when foraging for food in unfamiliar flowers, according to a study in this week's issue of the journal Current Biology. This research on the "bumblebee mind" may offer insight into the survival and growth of plant species that depend on bees for pollination.

The insects' social interactions, such as "bee dances," are among the most complex systems of communication in the animal kingdom. Though social creatures at times, bumblebees had been considered loners when it came to finding nectar.

"People had thought of them as individual foragers," said the study's lead author, biologist Ellouise Leadbeater of the University of London. "No one had thought they'd attract one another to the food source."

Leadbeater and her colleagues studied 17 pairs of bees. For each pair, they released one bee into a clear box containing a group of three identical artificial flowers. Once this "demonstrator" bee had settled upon the blossoms, which offered a dose of sugar water, seven other groups of such flowers were placed in the box. Faced now with eight groups of flowers from which to choose -- four groups yellow and four blue -- an "observer" bee was released into the chamber.

The observers initially preferred the same group of flowers on which the demonstrator had begun feasting. But this mimicking occurred only when the bees explored unfamiliar flowers. After experiencing the taste of a flower during their first flight, about two-thirds of the observers returned to the same color flower when the test was repeated. Observers who tried a different color landed on the new color only if the demonstrator was already on a flower of that color, with the majority landing on the exact same group that was occupied by the demonstrator.

Bumblebees mark flowers they visit with scented secretions to repel other bees, allowing them to focus their efforts on untouched flowers likely to offer greater reward. The finding that bees sometimes seek, rather than avoid, such deflowered flowers invites speculation as to the advantage of such behavior. Given limited resources with which to forage among unknown flowers, bees may be driven to invest in a type of flower that already has been shown to reward another bee.

"Bees are making these decisions millions of times each day," Leadbeater said. "How they make these decisions affects which plants get visited and which don't," and thus which get pollinated.

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