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Let’s get into the cockpit of a honey bee worker (to borrow an evocative metaphor used by Jochen Zeil) and try to figure out how she is going to solve a problem in navigating and communicating: finding a food source, getting back home, and informing her nest mates how to find the same food. This is a problem that thousands of bees solve every day in every honey bee colony. Their ability to solve it explains a lot about their ecological success and their importance to our agricultural systems.
As we shall see, the bee does the navigation part by using visual features of the environment: the sun and earth-bound landmarks. She does the communication part by encoding navigational information into body movements that have been called a “dance language.”
To appreciate the difficulty of the problem, consider that it is common for bees to fly to food sources a mile or more from the nest. Let’s use two kilometers to keep things in round numbers, and because the metric system really does make it easier to do calculations in your head. Given that a bee is about a centimeter long, food that far in the distance is two hundred thousand body lengths away. Or you can think about it in travel time. Bees fly about eight meters per second, so it takes two hundred fifty seconds to fly two kilometers. That’s a little more than four minutes.
Why does it matter how far the bee has to travel? The key issue is that for a typical flight distance of two kilometers, neither the food source nor any landmarks around it are visible, smellable, or detectable by the bee in any other way. You of course face the same problem that the bee does if you want to set a course for a grocery store two kilometers or more from your home. Unless you live in a flat treeless plain where the IGA sign is visible down the road, all you can see at the beginning of your journey are features of the environment in the immediate vicinity of your starting point, but most of those—at least the ones fixed to the ground and not up in the sky—will soon disappear from view as soon as you are underway.
The solution to this problem, for both bees and people, is to rely upon either the sequence of landmarks (trees, bushes, hills) visible along the way, or on a directional reference, such as the sun, that can be continuously checked during the trip. Neither of these sources of navigational information is inherently easy to use. Landmarks corresponding to particular routes have to be learned, and for a long route it would be necessary to learn a long sequence of landmarks. Not only that, but the landmarks will look different on the way out to the goal than on the way back, and so the bee (and you) will need to learn how to recognize and use them going both ways. As for the sun, its position relative to the route is not constant thanks to the rotation of the earth, so you need to know how to compensate for this rotation.
Once the bee is back home with her load of food, the plot thickens. The next part of her challenge is something that she can do but that no other organism other than human beings can do—she has to tell her nest mates which way to go to get to the same food source. She does so with a series of body movements—a “dance” it has been called—while a small group of her nest mates pay close attention. This happens in total darkness, but it can easily be seen by us if the colony is in a glass-walled observation hive. The dance takes place on the vertical sheets of comb. The overall structure of the dance varies in specific ways according to the direction and the distance the bee has flown to reach the food. Many have noticed that the dance looks like a repeated reenactment, on foot and at a miniature scale, of the flight the dancer has just taken.
The bees following the dance, after attending it for a few cycles of repetition, will peel away, leave the nest, and search for the same flower patch that the dancer had come from. Many will get there, and may come home and do dances of their own, leading to a rapid buildup of foragers in the patch. The resemblance of this communication system to the way humans communicate—encoding information about experience in behavioral actions (vocalizations or gestures in our case)—led the discoverer of this system, Karl von Frisch, to call it a “dance language”.
For further explanation of how bees solve these problems, and how we know how they do it, stay tuned….