Short-finned pilot whale clicks
Among short-finned pilot whales click vocalizations occur during near all periods of vocal activity. It is generally believed for toothed whale species that clicks functionally serve for echolocation. Though clicks can also have a communicative function, researchers rather argue that communication between conspecifics is assured by tonal sounds such as calls and whistles (...here...).
Click ...here... to hear regular clicks
(.mp3 file with 1.2 MB)
Own research (...here...) showed that short-finned pilot whale clicks are short pulses mostly having a broadband frequency composition. Many sequences during which the whales emitted regular clicks ranged 5 - 60 s or even longer in duration. The inter-click interval (ICI) is about 0.5 seconds between clicks. The sound example was recorded during apparant foraging behavior at night. Though own observations showed that short-finned pilot whales also feed during daylight hours, they are generally believed to be night-time feeders. During the night their main prey -cephalopod species- ascend from deeper waters to the water surface (...here...).
Click ...here... to hear click trains (.mp3 file with 1.3 MB)
Own research further showed that pilot whales increase the pulse repetition rate ranging 20 - 80 pulses per second. These sequences were termed click trains. During this sound example, several pilot whales simultaneously emitted clicks trains and directed them towards the recording hydrophone. The animals sometimes increased and decreased their ICI. Such click train sequences were also observed during human-pilot whales in-water encounters where certain or several individuals direct their vocalizations to the snorkelers (...here...).
Click ...here... to hear buzzes
(.mp3 file with 2.2 MB)
During apparant foraging sequences pilot whales can increase their pulse repetition rates up to 90-280 pulses per second. These sequences were termed fast click trains or buzzes. Whereas regular clicks generally have a continous energy distribution from 0.1 to more than 24 kHz, during buzzes the energy distribution for frequencies becomes less broadband. The spectrogram shows a buzz lasting several seconds with concentrated frequency compositions from about 5 to 14 kHz. Buzzes supposingly represent pre-catch indicators. During the last stage of the prey catch, pilot whales (as several other clicking cetacean species) may use buzzes to focus on individual prey items.