2 HONEYBEES Making Smart Decisions

      Appledore Island is a tough place for honeybees.

      Anchored in the Atlantic off the coast of southern Maine, the rocky, wind-blown island is barely a half-mile long, with hardly any trees, which the bees need for nest building. In fact, you might describe the island as a kind of bee Alcatraz, which makes it an ideal place to observe their behavior under controlled conditions.

      A few summers ago, biologists Thomas Seeley of Cornell University and Kirk Visscher of the University of California at Riverside ferried a half-dozen colonies of honeybees to Appledore, which is home to the Shoals Marine Laboratory run by Cornell. For nearly a decade, Seeley and Visscher have been studying a fascinating example of what they call “animal democracy.” How do several thousand honeybees, they want to know, put aside their differences to reach a decision as a group?

      The focus of their research has been honeybee “house hunting.” In late spring or early summer, as a large hive outgrows its nest, the group normally divides. The queen and roughly half of the bees fly off in a swarm to create a new colony, leaving behind a daughter queen in the old nest. There may be fifteen thousand bees in the swarm, which typically clusters on a tree branch, while several hundred scout bees search the neighborhood for new real estate. Although the queen’s presence is important to bees in the swarm, she plays no role in picking a new nest site. That task is delegated to the scouts, who do their jobs without direction from a leader.

      When a scout buzzes off into the countryside, she’s looking for just the right dwelling place (I say she, because worker honeybees are all females). It must be well off the ground, with a small entrance hole facing south and enough room inside to allow the colony to grow. If she finds such a spot—a hollow in a tree would be perfect—she returns to the swarm and reports her discovery by doing a waggle dance. This dance, which resembles the one forager bees do when they locate a new patch of flowers, contains a code telling others how to find the site. Some of the scouts that see her dance will then go examine the site for themselves, and, if they agree with her assessment, they’ll return to the swarm and dance in support of the site, too.

      This is no trivial question for the bees. As long as the swarm is clinging to the branch, it remains exposed to weather, predators, and other hazards. But once the swarm selects a new home, it won’t move again until next spring. So it has to get it right the first time. If the group selects poorly, the entire colony could perish.

      One by one, scouts that have been exploring the neighborhood return to the cluster with news about different locations. Soon there’s a steady stream of bees flying between the cluster and a dozen or more potential nest sites, as more and more scouts get involved in the selection process. Eventually, after enough scouts have inspected enough sites, it becomes clear that traffic at one site is much greater than that at any other, and a decision is reached. The bees in the main cluster warm up their wings and fly off together to the chosen site—which almost always turns out to be the best one.

      Facing a life-or-death situation, in other words, a honeybee swarm engages in a complex decision-making process involving multiple, simultaneous interactions between hundreds of individuals with no leadership at all—exactly the kind of chaotic, unpredictable enterprise that, if attempted by people under stress, would almost certainly lead to disaster. Yet the bees almost always make the right choice.

      How do they do it?

      The Five-Box Test

      One spring day in 1949, a young zoologist named Martin Lindauer was observing a swarm of bees near the Zoological Institute in Munich, Germany, when he noticed something odd. Some of the bees, he realized, were doing waggle dances. Ordinarily that meant they were foragers that had found a nice patch of flowers nearby, and they were telling other bees where to go find it. But these dancers weren’t carrying any pollen or nectar, so Lindauer didn’t think they were foragers. What were they up to?

      Lindauer’s mentor at the University of Munich, the renowned zoologist Karl von Frisch, had recently figured out that the waggle dance—or “tail-wagging dance” as he called it—was in fact a sophisticated form of communication (he won a Nobel Prize for this research in 1973). When a foraging bee danced, von Frisch had discovered, she wasn’t just advertising a source of food, she was also providing precise directions to locate it. To perform such a dance, a bee would run forward a short distance on the hive’s comb while vibrating her abdomen in a “waggle.” Then she’d return to her starting point in a figure-eight and repeat this over and over, as if reenacting her flight to the flower patch. The length of her dance indicated how far away the food was, and the angle of her dance (relative to vertical) corresponded with the direction of the food (relative to the sun). If a bee danced in a direction thirty degrees to the right of vertical, for example—picture the number 1 on a clock—the flower patch could be found by flying in a direction thirty degrees to the right of the sun. It was an ingenious system, but it had never been linked to house hunting before.

      By carefully studying several swarms—sometimes running beneath them as they flew across the Bavarian countryside—Lindauer determined that the bees dancing on the swarm cluster were scouts that had been out searching for a nest site. Some were still powdered with red-brick dust from having explored a hole in a building, or blackened with soot from having checked out a chimney. Just as foraging bees used the waggle dance to share news about food sources, so the scouts were using it to report on potential real estate. At first, many of the scouts danced in different directions, apparently announcing various options. But after some hours, fewer and fewer sites were mentioned until, finally, all the dancers were pointing in the same direction. Soon after that, the swarm lifted off from its bivouac and flew to its new home, which Lindauer was able to locate by reading the code of the dances.

      The bees had reached a consensus, he theorized, because the liveliest scouts had persuaded the rest to go along with their choice. They did this by getting rivals to visit their preferred site, where, confronted with the superior qualities of the site, the former competitors simply changed their minds. One by one they were won over, he speculated, and the disagreement went away.

      In this respect, at least, Lindauer got it wrong. It wasn’t quite that simple. Researchers have since established that only a small percentage of scouts ever visit more than one site. The group’s decision does not rely on individual scouts changing their minds, but rather on a process that combines the judgments of hundreds of scouts—one that would remain a mystery for fifty years.

      That’s where Tom Seeley and Kirk Visscher came in. Beginning in the late 1990s, they picked up where Lindauer left off, this time using video cameras to record every aspect of the swarm’s behavior. They also brought some new ideas about honeybee deliberation. Given the large number of individuals that take part in house hunting, they doubted that bees’ decision making was based on consensus. It just seemed too complicated, like trying to get a large group of friends to agree on which movie to watch. More likely, they figured, the process relied on some form of competition. Instead of trying to work through their differences with one another, scouts dancing on the swarm cluster appeared to be actively lobbying for different sites. It wasn’t a meeting of minds at all, but a race to build up supporters—with the winners taking all.

      In that sense, the bees’ system was more like a stock market, in which the value of a security rises or falls according to the collective judgment