Fig. 2. The body movements from the digitized video clip of a two-year-old calf swimming independently at 3.84 m s^-1. Movements of the rostrum are in pink, cranial insertion of the dorsal fin is in yellow and the fluke tip is shown in blue. In this case, the dolphin swam from right to left, thus the orientation of the body parts was flipped in the y-plane during the coordinate transformation process (see Materials and methods). The magnitude of the distance between digitized points remains the same and is used in the calculations for swim effort. Peak-to-peak fluke stroke amplitude is the fluke displacement and is the difference in the y-coordinates of successive maximums and minimums (i.e. B-A and B-C) measured in m. Tailbeat frequency is the number of strokes s^-1, where one stroke is adjacent maximums or adjacent minimums (i.e. one stroke is from A to C).