Super-Hero Experiment #2: The Waggle Dance

In 1923, Karl von Frisch sat down in a meadow to observe the behaviors of a transparent-windowed colony of honeybees. His original experimental goal, as he remarked in his Nobel lecture in December of 1973, was to prove his faith in the color sense of the bee. After all, what was the point of flowers evolving such bright and brilliant color schemes, if the honeybees that pollinated and fed from them were colorblind? But with his days out in the meadow, Karl von Frisch uncovered much more than how the world of yellow sunflowers and purple cupheas appears in the eyes of the honeybee: indeed, he unveiled the very language of this incredible and hard-working social insect. Karl von Frisch, with his pioneering experiments in Germany, decoded the language of the bee. For his work, von Frisch earned the 1973 Nobel Prize in Physiology/Medicine, and has earned a spot here in Super-Hero Experiments! Tweet

“Karl von Frisch described as a simple language the round and waggle dances of honeybees. He found the real ‘Rosetta Stone’ to decipher the language of bees: Round dances mean a food source nearby, waggle dances one at some distance.” (Science 1973)

Karl von Frisch, a scientist of ethology studying out of the University of Munich, was the first and major proponent of the honeybee dance-language hypothesis. This hypothesis, by now viewed as an almost irrefutable fact of biology, holds that scout honeybees notify other hive-dwelling bees of pollen and food locations through the waggle dance, in an example of ‘the most sophisticated non-primate communication that we know of’ (Riley, Nature 2005). The waggle dance is a special mode of communication between bees that have returned to their hive after collecting sugary stores from a tasty flower, for example, and ‘recruit’ bees still in the hive and on the lookout for a meal. During the dance, the bee that has returned from successful foraging makes a series of figure-8 movements, shaking or ‘wagging’ its tail during the central or straight portion of its ‘dance’ (Panel A in figure to the right). The dance itself is fascinating to see, but the fact that honeybees act in such a way upon returning from a food source was not by itself so novel to the keen ethologist von Frisch. What WAS intriguing to the pioneering researcher of honeybees was the surprisingly rich and socially shared information encoded in the waggle dance!

It was during von Frisch’s first field experiments in 1923 that he observed that bees resting in the hive were taking some kind of cue from returning foragers to themselves venture out and find an artificially placed feeding source. The clever ethologist set up a small colony of honeybees with a glass observation window, and marked individual foragers with distinctly colored dots. He then placed two different feeding sources, either artificial sugar syrup bowls or real flowers, at different locations in a meadow, and observed bees coming and going between food sources and the colony. By his observations he concluded the following: foraging bees in the colony “let themselves be guided by the scent of the dancers.” In other words, he found that the fragrance of a specific sugar syrup or blossom attached to the body of a returning ‘dancing’ honeybee determined which food source a responding bee flew too. He also noted that the sweeter the food source, the more ‘lively and lengthier’ the dance of a returning bee. The honeybee was obviously doing a wonderful job of alerting her colony-mates of good quality nearby food sources, and for that, she earns a hardworking and unselfish namesake.

But these observations were only the tip of the iceberg for the honeybee dance-language hypothesis. Twenty years after his initial field experiments, in 1943, Karl von Frisch went out into the meadow again, this time revealing the most beautiful aspect of the honeybee waggle dance. Having installed one feeding place close to the hive (within 12 meters), and another 300 meters away, the ethologist noticed this time around very different dancing patterns from foragers returning from the nearby feeding source as opposed to those returning from the distant meadow. All foragers from nearby performed short and round dances, whereas all foragers from the long-distance food source performed longer figure-8 tail-wagging dances. He noted that the tail wagging dance sent responders, or ‘recruits’, to greater distances in the search of a food source. Longer distances, requiring longer flight times for recruited bees, were seemingly communicated by longer tail-wagging times, or longer periods spent in the straight portion of the figure-8 waggle dance.

Believe it or not, the beauty of the waggle dance doesn’t stop here. Karl von Frisch also noted the fact that the honeybee tail-wagging dance encoded the direction to the targeted food source. He observed that the dancer always showed the other bees the direction to the food source in relation to the position of the sun. She did this by performing the tail-wagging portion of her dance on the honeycomb at an angle (α) away from vertical (the honeycomb typically hangs vertically) representing the angle away from the sun at which the recruit bee would need to fly to find the food source. For example, if the target food source or flower resided in the direction of the sun, the dancer’s tail-wagging would point straight upward on the vertical honeycomb surface. If the flower resided an angle of 40° to the left of the sun’s position, the dancer would shift the straight ‘waggle’ of the dance 40° to the left of the vertical (Karl von Frisch Nobel Lecture). By always choosing to represent the angle away from the sun as an angle away from the vertical, the dancing bee could direct other bees to the scrumptious goal that she had just returned from even in the darkness of the hive. She could even account for the continuous daily motion of the sun across the sky with her precisely timed ‘inner clock’, adjusting the direction of her waggle dance accordingly.

In his Nobel Prize lecture, von Frisch fondly remembers: “Those hours at the observation hive when the bees revealed this secret to me, that the recruiting dancers show the other bees the direction to the goal in relation to the position of the sun, remain unforgettable.” While fellow scientists in von Frisch’s day had their doubts, many further experiments proved that he was right: responding honeybees determined the location and distance to a food source based on the dance of a returning forager, and not simply from the scent of the pollen on the body of the dancer. Bees responding to a waggle dance would fly with amazing accuracy in the direction of the intended target, and avoid other nearby ‘fake’ targets labeled with similar scents but no food. Indeed, experiments intended to ‘confuse’ the honeybees, in which their hives were placed horizontally instead of vertically, and in which the sky was screened so that the bees were not aware of their position in relation to the sun, resulted in very confused bees regardless of scent stimuli. However, a honeycomb can be turned continuously like a playing record, and the honeybees, as long as they have access to some portion of sunlight or blue sky, will “adjust themselves to their new direction, like the needle of a compass.” This amazing ability to adjust their dances based on the orientation of their comb to the sun, or to gravity in the case of vertical combs, is quite an accomplishment! It is a testament to the ingenuity with which Mother Nature guides the intelligent movements of swarms and other social animal collectives.

Karl von Frisch won a Nobel Prize for opening the eyes of researchers to the ‘complex and versatile communication behavior’ of social insects such as the honeybee (Science, 1973). His original experiments back in 1923 and circa 1943 have been confirmed by complex modern experiments, such as in work published in Nature in 2005 by J.R. Riley and colleagues. The fact that modern experiments have only strengthened and added to von Frisch’s original hypothesis is a testament to his scientific acumen and superb skills of experimental observation. For his contributions to the field of ethology and biology at large, we dub Karl von Frisch a Super-Hero of science experiments extraordinaire!

Summary:
• Honeybees communicate the location of food sources or new hive locations to other bees via the waggle dance.
• The direction of the straight portion of the waggle dance points directly towards a food source (if the bee dances on a horizontal surface) or points a certain angle away from vertical representing the angle away from the sun where the food source can be located. The direction of the sun is symbolized by straight up on a vertical hive surface.

References:
1) Karl von Frisch, Decoding the Language of the Bee, Nobel Lecture, December 12, 1973
2) “Karl von Frisch – Nobel Lecture”. Nobelprize.org. 28 Jul 2011 http://nobelprize.org/nobel_prizes/medicine/laureates/1973/frisch-lecture.html
3) Riley et al. The flight paths of honeybees recruited by the waggle dance. Nature 435, 205-207 (2005)
4) P. Marler, D.R. Griffin. The 1973 Nobel Prize for Physiology or Medicine. Science 182, 464-466 (1973)
5) Images and Video from Wiki Commons unless otherwise noted

Glossary:
• Ethology = the scientific study of animal behavior, and a sub-topic of zoology.

Riley, J., Greggers, U., Smith, A., Reynolds, D., & Menzel, R. (2005). The flight paths of honeybees recruited by the waggle dance Nature, 435 (7039), 205-207 DOI: 10.1038/nature03526