Reconsiderando a dança das abelhas melíferas

When Karl von Frisch decoded the secret language of bees in 1946, even he couldn't quite believe what he had found. Was it really possible for a creature with a brain smaller than a pinhead to do something so clever? "It is conceivable that some people will not believe such a thing. Personally, I also harboured doubts in the beginning," he said in his Nobel lecture in 1973.

Countless experiments later, the bee's waggle dance has become an established scientific fact. Even schoolchildren are taught that honeybees dance to tell hive-mates about good food sources. Most researchers have long since stopped asking whether bees communicate in this way and concentrated on working out how the dance - among the most sophisticated forms of animal communication outside of primates - evolved.

In the waggle dance as described by von Frisch, a bee returning from a plentiful food source heads for one of the hive's vertical honeycombs, where it runs in a figure of eight. On the straight part of the run, the bee buzzes its wings and vibrates its abdomen - the "waggle" (see diagram). Von Frisch's insight was that this middle portion of the dance contains two crucial pieces of information about the location of food.

First of all, direction is given in relation to the sun's position. If the food source can be found by flying directly towards the sun, the middle of the dance is perfectly vertical. Any angle to the right or left of the sun is communicated by running at the same angle to the vertical. Distance, meanwhile, is communicated by the duration of the waggle. The longer the bee waggles, the further away the food is: about 75 milliseconds is added to the waggle for every 100 metres. These two pieces of information are what von Frisch dubbed "the dance language".

The dance, which can go on for several minutes, attracts other bees, which become increasingly excited as they watch the dancer. Once a follower has observed five or six runs, it leaves the hive and flies directly to the food, as if by satnav. This behaviour is seen as crucial to a hive's success.

Or that's how the story goes. In recent years, some researchers have begun to suggest that the waggle dance is too good to be true. While they accept that the dance contains information about the location of food, they argue that its importance has been massively overstated. A litany of recent evidence suggests that while bees can follow the dance, they often fail to decode it properly, or ignore it completely (Trends in Ecology and Evolution, vol 24, p 242).

"I think the atmosphere is changing," says Christoph Grüter at the University of Sussex in Brighton, UK. "People are much more open to the idea that the dance language is not that important."

In one study, Grüter and his colleague Walter Farina of the University of Buenos Aires in Argentina found that among bees that attend to a dance, 93 per cent ignore the instructions and head to a food source they already know about (Proceedings of the Royal Society B, vol 275, p 1321). Similarly, bees often seem unable to follow the instructions. Some watch more than 50 runs and make several sorties out of the hive but never find the food.

The waggle dance also turns out to be much less important to foraging success than has been suggested. Hives in which the honeycombs are laid horizontally, preventing the bees from indicating direction properly, don't fare any worse than others, except when natural food sources are severely depleted.

So why hasn't this been noticed before? Grüter points out that most waggle dance experiments are carried out in highly unnatural conditions, using artificial feeders filled with sucrose solution in areas where there are few natural food sources. While this eliminates the confusion of having lots of bees dancing about lots of different food sources, it gives an overly simplistic picture.

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PDF gratuito do artigo Informational conflicts created by the waggle dance de Christoph Grüter1,2, M. Sol Balbuena1 and Walter M Farina1* aqui.

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