Figure 4
From: Wild harbour porpoises startle and flee at low received levels from acoustic harassment device
Behaviour around AHD exposure of HP3. See legend in Fig. 3 for general figure explanations. (a) The porpoise had surfacing periods right after the AHD exposure, where it seemed to lay at the surface several times. (b) The SELcum exceeded the TTS-threshold, indicating a risk of hearing impairment. Received level (rms fast) of the pings decreased as the porpoise swam away from the sound source. (c) Shortly after exposure start, the echolocation ceased (clicks per minute, cpm) and was not resumed until 10 min after the exposure had stopped. (d) Swimming effort increased, especially during the initial part of the exposure. During and after the exposure, the porpoise increased breath-hold intervals, but also increased number of breaths per surfacing, compared to before the exposure.
