Researchers use math to explain dolphins' dance

Findings show dolphins' "pirouette" is not made possible by helicopter-like movements of their tails.

dolphin 88 (photo credit: )
dolphin 88
(photo credit: )
Israeli and American researchers have succeeded in decoding the dolphin's technique of "dancing in the air." Writing in the Journal of Experimental Biology, Prof. Daniel Weiss of the Technion-Israel Institute of Technology's aeronautics and space engineering faculty and US colleagues explain that the dolphins' "pirouette" is not made possible by helicopter-like movements of their tails. Instead, Weiss - along with Prof. Frank Fisch and Prof. Anatoly Nicastro of the University of West Chester in Pennsylvania - found that dolphins are not flexible enough, so it is unreasonable that movement of their tails in the air allows them to perform a pirouette. Instead, based on biochemical and hydrodynamic principles collected from studies of dolphins and fish, the team formulated a mathematical model that explains how dolphins are able to dance like ballerinas. Dolphins start rotating while they are still under water, which makes the turn slow because of resistance. When the dolphin emerges from the water, the resistance around it suddenly is reduced, so the final twist of the tail in the water speeds up and makes possible the pirouette. Their model explains how the speed of the dolphin's turn when it leaves the water - six meters per second - allows it to make seven turns before it falls back into the sea. The swimming mammal's airborne dance "is not meant for playing and enjoyment," the researchers insist. The force of the dolphin's "slap" when it returns to the water is very painful - but dolphins continue to dance in the air because it serves a purpose: The force of the spin removes parasites called remora from dolphins' bodies. These parasites hold on to dolphins and sharks and feed on them, Weiss noted. The journal article, which was recently detailed in the prestigious journal Science, "presents the only basic research from the biomechanical and hydrodynamic point of view of the dolphin's pirouette," noted Prof. Malcolm Gordon, a marine biologist at the University of California at Los Angeles. "The article completely refutes the traditional theory on this matter." Three years ago, Weiss succeeded in explaining the amazing natural phenomenon of how baby dolphins keep up the pace next to their mothers for three years. The explanation was hydrodynamic effects from the mother's fast swimming that pushed the baby ahead without expending much effort.