Fig. 5. Kinematic variables plotted against fork length. (A) Turn angle; (B) angular velocity; (C) duration; (D) curvature. Turn angle (A) and angular velocity (B) show a biphasic pattern of change. The transition points as identified by piecewise linear regression occur at FL=1.18±0.28 cm for turn angle and FL=1.16±0.23 cm for angular velocity. The piecewise regression for turn duration (C) against FL, although significant overall, did not have a significant transition point. Body curvature (D) did not have a significant piecewise regression and so we interpret the rate of change as constant across ontogeny with a slope of –16±6; a quadratic model did not fit the data significantly better than a single linear regression model. For further explanation of the regressions, see Statistics in Materials and methods. In all graphs each point represents the mean value per individual, from 2 or 3 turning sequences.