While exploring the jungles of New Guinea in 1959, agricultural researcher John H. Barrett often heard strange, intermittent buzzing sounds. The buzzes came from bees, which was to be expected, but they were significantly louder and higher in frequency than the usual flight sounds. With further study, Barrett realized he was witnessing a novel way of gathering pollen.The method, which was later termed buzz pollination or floral sonication, is comparable to gathering fruit by shaking a fruitbearing tree. After a plant is buzzed in this fashion, pollen may fall directly on the flower's stigma or be carried to another flower by the offending bee.
To release the pollen, the animal uses its mouth appendages called "mandibles" to grasp the anthers, the flower's pollen-producing organs, and shake them by contracting its flight muscles 200 to 500 times per second, without moving its wings. During this intense shivering motion, a bee's body may experience accelerations approaching 30 g's— roughly four times the level test pilots can endure. Buzz pollination is practiced by a large number of bee species, including bumblebees and carpenter bees, but not by honeybees, for reasons that continue to puzzle entomologists.
In most flowers, pollen in the anther is readily accessible. When the anther of a mature flower splits open, its pollen either spills out or is easily extracted by insects. In about eight percent of the world's flowering plants, roughly 20,000 species in all, the anthers consist of narrow tubes with tiny pores at one end, requiring a good shake to dislodge the pollen. Buzzing is by far the most efficient way to do this. A bumblebee, for example, can collect pollen from deadly nightshade flowers hundreds of times faster than a non-buzzing honeybee.
Plants that yield important crops such as tomatoes, potatoes, blueberries, cranberries, eggplant, chili peppers, and kiwi fruits rely on buzz pollination. For years, tomatoes grown in greenhouses were hand-pollinated by people equipped with electric vibrators—a slow, expensive process. Bumblebees, of course, have an evolutionary advantage over humans and today this job is mainly left in their capable hands—or mandibles, to be precise.
More than 80 percent of the world's 250,000 flowering plants depend on animal pollinators, and roughly 15 to 30 percent of the food eaten throughout the world comes from plants pollinated by these creatures.