To compare the energy costs of different techniques animal swims, American engineers have developed a robot swimmer style turtle Wednesday. This robot swimmer was named Madeleine by its designers of Vassar College in New York. Its shape and its measurements are comparable to those of a sea turtle It measures 80 cm long and 30 cm wide and weighs 24 kg. Thanks to him, U.S. scientists have studied the energy cost of different techniques of swimming. Madeleine is equipped with four fins, which can be activated independently. The researchers were able to compare the modes of propulsion involving two or four fins. Conclusion: with four fins active, acceleration and braking are better. However, two fins enough the robot to reach its maximum cruising speed, while spending twice less energy than when its four fins are moving.This study could explain why animals using only their two upper limbs to propel itself into the water, such as penguins, seals or sea turtles have emerged during evolution. Indeed, their technique swimming would, under natural selection, the advantage of being less costly energy. The robot turtle-American engineers could also help develop means of propulsion for more efficient vehicles autonomous submarine tomorrow.