1. Click interval of typical click trains emitted by Freja (A) and Freja blindfolded (B) during no fish trials and fish trials.
Click interval of typical click trains emitted by Freja (A) and Freja blindfolded (B) during no fish trials and fish trials. The click interval is plotted against time relative to the arrival of the porpoise in front of the hydrophone array in no fish trials (distance to reference, 5 m), and relative to the time of fish catch in fish trials (distance to fish, 0 m). As additional information, the corresponding distance is given (second y-axis in grey) to the reference (dark grey line) and to the fish (light grey line). The time of splash (S), the presumed time of prey detection (*), the time at the transition from far to near stage (T) and fish capture (C) are also shown. The black bars on the x-axes mark the time stretch DR=26–12 m, from which data were included in further analyses. Clicks with intervals >120 ms were not plotted (marked by X in B). The sudden increase in click interval shown by the arrow at about –6 s (19 m) for Freja (blindfolded) in the no fish trial (B left) indicates a shift to another landmark (see Results).
Ursula K. Verfuß et al. J Exp Biol 2009;212:
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