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Dancing in the Hive
4 June 2008 (All day)
When a honey bee finds a nectar-laden patch of flowers, she flies back to the hive and does a dance that tells her fellow workers how to get there. A new study shows that two species of honey bee have different dance styles but can understand each other even after evolving separately for 6 million to 8 million years. Further experiments might reveal whether bees are smart enough to learn new dance moves, a knack that could help explain how this method of communication evolved.
Honey bees perform three types of instructive dances. The most complicated steps belong to the waggle dance, which traces out a figure eight on the vertical surface of the honeycomb and provides directions to the most distant flowers. During one part of the figure, the bee walks in a straight line waggling her abdomen. The duration of this waggling reveals the distance to the flowers, while the angle of the path tells the direction.
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Earlier experiments suggested that honey bee species had different "dialects" in their waggle dances. But not everyone was convinced because of potentially confounding factors; perhaps the dances differed because the bees flew through different environments, for example.
To make sure foragers experienced the same conditions, a team of researchers from Germany, China, and Australia created a single hive in which both species would live and work. That was a challenge, because usually two species under one roof will kill each other. The team was able to raise workers of the European honey bee, Apis mellifera, in a hive of the Asian honey bee, Apis cerana. The secret was keeping the hive well-stocked with sugar syrup, calming disturbances by spraying the bees with diluted honey, and removing troublemakers.
After setting up two such hives at the Agricultural School of Zhangzhou in China, the researchers trained the European and Asian bees to fly to a feeder placed various distances from the hive. In general, the dances were similar. But there was a key difference: Asian foragers waggled longer than European ones did to signal the same distance, the team reports online in the June issue of PLoS ONE. "This paper provides the best evidence yet there are these dialects," says entomologist and neuroscientist Gene Robinson of the University of Illinois, Urbana-Champaign.
The next step was to see if the bees could understand each other. The team painted identification marks on Asian bees that were watching dances (see video) of European bees trained to fly to a feeder 500 meters away. Many more of these Asian bees found the 500-meter feeder than other feeders placed 400 or 600 meters away. This shows that Asian bees can understand the European dances, says author Shaowu Zhang, a biophysicist and animal behaviorist at the Australian National University in Canberra.
Behavioral ecologist Lars Chittka of Queen Mary, University of London, calls that a "provocative conclusion." He's not convinced that the Asian bees were getting their information only from the European dancers. But he and Robinson say that the findings raise the intriguing possibility that honey bees can learn to interpret unfamiliar waggle dance moves. If so, that ability might explain how two traits--an instinctive dance and the ability to understand it--both evolved when neither one alone provides an advantage. Perhaps, Chittka speculates, ancient bees were able to learn what a mutant dancer was trying to say.