The Dance Language of the Honey Bee
There can be no argument that the most famous aspect of honey bee biology is their method of recruitment, commonly known as the honey bee dance language. It has served as a model example of animal communication in biology courses at all levels, and is one of the most fascinating behaviors that can be observed in nature.
The dance language is used by one individual to communicate two items of information to one ore more receivers: the distance and direction to a location (typically a food source, such as a patch of flowers). It is usually used when an experienced forager returns to her colony with a load of food, either nectar or pollen. If the quality of the food is sufficiently high, she will often perform a "dance" on the surface of the wax comb to recruit new foragers to the resource. The dance language is also used to recruit scout bees to a new nest site during the process of reproductive fission, or swarming. Recruits follow the dancing bee to obtain the information it contains, and then exit the hive to the location of interest. The distance and direction information contained in the dance are representations of the source's location (see Components of the Dance Language), and thus is the only known abstract "language" in nature other than human language.
The dance language is inextricably associated with Dr. Karl von Frisch, who is widely accredited with discovering its meaning. He and his students carefully described the different components of the language through decades of research. Their experiments typically used glass-walled observation hives, training marked foragers to artificial feeders placed at known distances from a colony, and carefully measuring the angle and duration of the dances when the foragers returned. His work eventually earned him the Nobel Prize (in Medicine) in 1973.
The concept of a honey bee language, however, has not been free of skepticism. Several scientists have argued that simply because the dance exists does necessarily mean that it communicates information about the location of a food source. Those critics have argued that floral odors on a forager's body are the major cues that recruits use to locate novel food sources. Many experiments have directly tested this alternative hypothesis and demonstrated the importance of floral odors in food location.
The biological reality, however, is somewhere in between these two extremes. The current conventional wisdom holds that recruits go to the area depicted in the dance, but then "home in" to the flower patch using odor cues. Indeed, researchers have built a robotic honey bee that is able to perform the dance language and recruit novice foragers to specific locations. The robot, however, is unable to properly recruit foragers to a food source unless there is some odor cue on its surface. Nevertheless, it is clear that honey bees use the distance and direction information communicated by the dance language, which represents one of the most intriguing examples of animal communication.
Components of the dance language
At its core, there are two things communicated in a dance: distance and direction. These two pieces of information are translated into separate components of the dance.
When a food source is very close to the hive (i.e., less than 50 meters away), a forager performs a round dance (see Figure). She does so by running around in narrow circles, suddenly reversing direction to her original course. She may repeat the dance several times at the same location or move to another location to repeat the dance. After the round dance has ended, she often distributes food to the bees following her. A round dance, therefore, communicates distance ("close to the hive"), but no direction.
Food sources that are at intermediate distances, between 50 and 150 meters away from the hive, are recruited to with the sickle dance. The form of this dance is crecent-shaped, a transitional dance between a round dance and a figure-eight waggle dance (see below).
A waggle dance, or wag-tail dance, is performed by bees foraging at food sources that are over 150 meters away from the hive. This dance, unlike the round and sickle dances, communicates both distance and direction² to potential recruits. A bee that performs a waggle dance runs straight ahead for a short distance, returns in a semicircle to the starting point, runs again through the straight course, then makes a semicircle in the opposite direction to complete a full, figure-eight circuit. While running the straight-line course of the dance, the bee's body, especially the abdomen, wags vigorously sideways. This vibration of the body gives a tail-wagging motion. At the same time, the bee emits a train of buzzing sound at a low frequency of 250-300 Hertz (cycles per second) with a pulse duration of about 20 milliseconds and a repetition of frequency of ca 30 seconds. The sound is produced by wingbeats.
While several variables of the waggle dance are correlated with distance information (e.g., dance "tempo", duration of buzzing sounds), the duration of the straight run portion of the dance, measured in seconds, is the simplest and most reliable indicator of distance. As the distance to the food source increases, the duration of the waggling portion of the dance (the "waggle run") also increases. The relationship is roughly linear, as shown in the figure. For example, a forager that performs a waggle run that lasts 2.5 seconds is recruiting for a food source located approximately 2625 meters away.
While the representation of distance in the waggle dance is relatively straight-forward, the method of communicating direction is more complicated and abstract. The orientation of the dancing bee during the straight portion of her waggle dance indicates the location of the food source relative to the sun. The angle that the bee adpots, relative to vertical, represents the angle to the flowers relative to the direction of the sun outside of the hive. In other words, the dancing bee transposes the solar angle into the gravitational angle. The figure below gives three examples. A forager recruiting to a food source in the same direction as the sun will perform a dance with the waggle run portion directly up on the comb. Conversely, if the food source were located directly away from the sun, the straight run would be directed vertically down. If the food source were 60 degrees to the left of the sun, the waggle run would be 60 degrees to the left of vertical.
Because the direction information is relative to the sun's position, not the compass direction, a forager's dance for a particular resource will change over time. This is because the sun's position moves over the course of a day. For example, a food source located due east will have foragers dance approximately straight up in the morning (because the sun rises in the east), but will have foragers dance approximately straight down in the late afternoon (because the sun sets in the west). Thus the time of day (or, more importantly, the location of the sun) is an important variable to interpret the direction information in the dance.
The sun's position is also a function of one's geographic location and the time of year. The sun will always move from from east to west over the course of the day. However, above the tropic of cancer, the sun will always be in the south, whereas below the tropic of capricorn, the sun will always be in the north. Within the tropics, the sun can pass to the south or to the north, depending on the time of year.
In summary, in order to translate the direction information contained in the honey bee dance language, one must know the angle of the waggle run (with respect to gravity) and the compass direction of the sun (which depends on location, date, and time of day).
The following tutorial enables you to vary the numerous parameters that are important to a foraging honey bee so that you may see how she would dance to recruit other foragers to the same resource.
Click HERE to start the tutorial, or use this address:
- Move the cursor over the image to start the movie.
- Change the various parameters to see how the dance changes. Move the locator on the map to change the position of the hive on the globe, or switch to a map of the continental US. In both cases, the default location is Raleigh, NC. Move the slide bars on the right to vary julian date, time of day, food source location, and food source direction.
- As you change each variable, the parameters that are affected will be highlighted and recalculated.
- The angle of the sun (azimuth) as a function of the time of day is plotted on the left, and the compass directions of the sun and food source is plotted on the right.
- The distance and direction information in the dance will be automatically recalculated, and the forager will change her dance accordingly.
- All calculations are performed as the mouse is moving, which may affect the real-time speed of the dance. After you change the variables, keep the cursor still to see the correct tempo of the dance.
- The latitude, longitude, and azimuth calculations are approximations, not exact values. Please, no angry emails from astronomers!
- The sun rise and sun set times do not include factors such as daylight savings time, change in horizon, and altitude, so the amount of daylight for a given date may vary from what is plotted in the graph.
- To get accurate data for the sun's position, go to the US Naval Observatory.
- Frisch, Karl von. 1967. The Dance Language and Orientation of Bees. The Belknap Press of Harvard University Press, Cambridge, Massachusetts, pp. 566.
- Frisch, Karl von. 1976. Bees: Their Vision, Chemical Senses, and Language. Cornell University Press, Revised Edition, Ithaca, N.Y., pp. 157.
- Seeley, Thomas D. 1995. The Wisdom of the Hive: The Social Physiology of Honey Bee Colonies. Harvard University Press, pp. 295.
- Wenner, Adrian M. and Patrick H. Wells. 1990. Anatomy of A Controversy: The Question of a "Language" Among Bees. Columbia University Press, New York, pp. 399.
- Dance diagrams: from von Frisch, 1976 p. 70.
- Direction figure: from Barth, F. G. 1982. Insects and Flowers: The Biology of a Partnership, p. 221, Princeton University Press