Fig. 6. Perception of ocean wave direction by hatchling sea turtles. (A) The motion of a hatching turtle swimming with and against the direction of wave propagation. For a hatchling oriented into waves (left), the sequence of accelerations during each wave cycle is upwards, backwards, downwards and forwards. A turtle swimming with the waves (right) is accelerated upwards, forwards, downwards and backwards. Modified from Lohmann and Lohmann (Lohmann and Lohmann, 1992). (B) A machine designed to simulate wave motion by reproducing the sequence of accelerations that occur beneath a propagating wave. The responses of hatchling turtles to these simulated waves have been studied by placing turtles into cloth harnesses (see C) and subjecting them to orbital movements while they are suspended in air. Modified from Lohmann et al. (Lohmann et al., 1995b). (C) A hatchling turtle suspended in air on the wave simulator. Hatchlings suspended in this way act out their normal swimming behavior and will attempt to turn until facing into simulated waves.