Fig. 4.

Nearby vocal animals and high-speed swimming at the surface by Sowerby's beaked whales. (A) Waveform and (B) spectra of high-intensity clicks recorded near the surface, produced by untagged conspecifics or by toothed whales of another species (blue dots in Fig. 1 show the occurrence of these clicks in the dive profiles of the tagged whales). (C,D) Tagged Sowerby's beaked whales produced occasional bursts of high speed near the surface, reaching estimated forward speeds of 8 m s⁻¹ with stroking rates of up to 2 Hz. (C) Dive profile during 90 s of surface swimming coloured by estimated forward speed. Intervals with absolute pitch angle <20 deg when the speed cannot be accurately estimated are uncoloured. (D) Pitching rotations due to swimming as measured at the tag position on the body over the same interval (black line), and inferred instantaneous stroking rate (red dots).