It’s hard to write a biology of the honey bee and not pause to linger over the waggle dance – one of the most celebrated examples of animal communication and a window into all sorts of questions about the honey bee’s evolution and modern functioning as a superorganism. Indeed, the waggle dance figures prominently in any discussion of group decision making, a topic I covered in my March installment. The waggle dance is a true symbolic language, by which we mean its users employ symbols – models or representations of real things. Communication can happen without symbols. If I were lecturing an audience and wanted to call their attention to a dog, I could bring my gregarious mutt Elijah on stage and he would wag his tail at them. Or, I could speak the combined Latin letters d-o-g and accomplish the same thing with much greater ease, those three letters of course symbolically representing the real animal. Honey bees do this same kind of cognitive leap – using models of reality to refer to the real things. For analyzing the honey bee dance and recognizing what it is, the Austrian scientist Karl von Frisch won the Nobel Prize in Physiology or Medicine in 19731, and since then scores of scientists have deepened our understanding of the intricacies and layers of this behavior.
To begin, let’s refresh with an overview of the waggle dance. It is essentially a means by which scout foragers communicate to potential recruits the distance, direction, and quality of a potential resource. The resource can be a nest site in the context of a swarm, or a foraging asset such as nectar, pollen, water, or propolis in the case of an established colony. A recruit may then use the information to fly out and inspect the resource herself, and if she agrees about its desirability she may return to the nest and reinforce the campaign with a dance of her own. In this manner the foraging force can rapidly mobilize around the most profitable sites and, by voting with their direct participation, steer the group toward a “decision.” Inversely, non-profitable sites receive fewer follow-up dances and thus interest in them fades rapidly.
Think for a moment how many moving parts there are in this machine. There are at least two levels of participant – the scout/dancer and the recruit/dance-follower; there are at least two levels of information – the information going “out,” that is, information about the resource being communicated by the scout, and the information coming “in,” that is, how that information is being received and processed by the recruits. And finally, there may be related signals that have nothing directly to do with communication at all but rather serve as announcements, “Hey everybody, come over here and watch my dance!” and for a human observer it can be difficult to know the difference between an announcement vs. real information. I’ll try to explain the waggle dance taking into consideration these moving parts. In what follows I draw heavily upon the excellent review by Fred Dyer and sources cited therein2.
The scout/dancer performs the waggle dance in a figure-8 pattern (Fig. 1), during the straight run of which she waggles her abdomen left and right. After completing a straight-run waggle she circles back and does it again, each return constituting one circuit. She alternates her return trips left and right, hence the figure-8 pattern. It’s the straight run that encodes for directional information, and it works like this: the angle of the straight run relative to gravity, in our case the top of the comb, is correlated to the angle of the resource to the sun relative to the nest (α° in Fig. 1). It’s as if the bees have agreed to pretend that the top of the comb corresponds to the direction of the sun when viewed from the nest. The degrees of the straight run to the left or right of true vertical correspond to the degrees left or right of the sun as viewed from the colony. True vertical has become a symbol for the direction of the sun, and the angle of the straight run relative to vertical has become a symbol for the resource’s direction relative to the sun.
The distance to the resource is symbolized by the tempo of the dance, the number of waggles performed in a straight run, and the duration of piping noise the dancer makes while she performs her straight run. As the distance to the resource increases, the tempo slows down, the number of waggles increases, and the duration of piping increases. Conversely, the nearer the resource the faster the dance and briefer the piping.
This is a good place to stop and mention another kind of …