Dolphins fishing alone in open waters may whistle without interrupting their sonar clicks as they find and eat or reject fish. Our study is the first to match sound and video from the dolphin with sound and video from near the fish. During search and capture of fish, free-swimming dolphins carried cameras to record video and sound. A hydrophone in the far field near the fish also recorded sound. From these two perspectives, we studied the time course of dolphin sound production during fish capture. Our observations identify the instant of fish capture. There are three consistent acoustic phases: sonar clicks locate the fish; about 0.4 s before capture, the dolphin clicks become more rapid to form a second phase, the terminal buzz; at or just before capture, the buzz turns to an emotional squeal (the victory squeal), which may last 0.2 to 20 s after capture. The squeals are pulse bursts that vary in duration, peak frequency and amplitude. The victory squeal may be a reflection of emotion triggered by brain dopamine release. It may also affect prey to ease capture and/or it may be a way to communicate the presence of food to other dolphins. Dolphins also use whistles as communication or social sounds. Whistling during sonar clicking suggests that dolphins may be adept at doing two things at once. We know that dolphin brain hemispheres may sleep independently. Our results suggest that the two dolphin brain hemispheres may also act independently in communication.

Large odontocetes are considered at risk of auditory and behavioral impacts from sonar, and it is necessary to predict the effects of tonal sonar signals that have widely varying durations. Here, the effect of sound duration on hearing threshold and reaction time was investigated in two killer whales (Orcinus orca) using behavioral methods. Hearing tests were conducted using sounds between 50 μs and 2 s in duration for frequencies across the hearing range. Hearing thresholds within each frequency were dependent on sound duration, with threshold increasing with duration out to a plateau, which was used to calculate auditory integration time. Vocal response reaction time data showed decreasing latency with increasing signal level and length. These data were consistent with other marine mammal species and demonstrate that signal detection and behavior are affected by the duration of tonal sounds in killer whales.