Fig. 2. The predictive start of archer fish. (A) After the shot of a group member has just dislodged an aerial insect, a responding fish (lower right) turns from its initial orientation (dotted line) and takes off directly towards the later point of impact, with a speed matched to distance. Because the initial values of prey motion (initial height, speed and take-off angle) vary independently over broad ranges, predicted points P of impact can be anywhere within a large area. They must be inferred from a quick judgement of the prey's initial motion, based on which the fish must rapidly select an appropriate turn (angle ) and take-off (speed v). The match that the responding fish must make is illustrated by showing three ways (in different colors) in which a given shot might dislodge the target insect. The correspondingly different impact points P₁-P₃ (shown in the respective colors) would require speed levels v₁-v₃ and turning angles ₁-₃. Responses aimed at P₁ and P₂ would require different turns but the same take-off speed, whereas responses to P₂ and P₃ would require the same turn, but different take-off speed. (B) The actual turning range and accuracy in the set of predictive starts (N=76) whose kinematics are analyzed in this study using digital high-speed video. Turns were accurately set to the later point of impact and accuracy did not decrease when larger turns were required. The regression line (r²=0.9016, P<0.0001) is not significantly different from that expected if actual turn size equalled the expected turn size.