Waves
Research 2
that white-beaked dolphin clicks were short (about 15-22 ms long) and broad band (90% energy bandwidth between 59-75 kHz) and similar to what has been reported from other dolphin species when
recording dolphin sound using broadband equipment (e.g. Au, 1993). However, the main difference of white-beaked dolphin clicks compared to other dolphin clicks, were a secondary frequency peak between 200 - 250 kHz, which can be about 6-10 dB below the main spectral peak. The high frequency component about 200 kHz has not been reported for other species until recently. It has now been reported from recordings of free-ranging Indo-Pacific Humpback dolphins, Sousa chinenses (Goold and Jefferson, 2004).  The whistles of white-beaked dolphins also consisted of a fundamental including higher frequencies that reported before at the time (up to 35 kHz). Though recently using broadband equipment has demonstrated a fundamental with higher frequencies for instance in whistles of the Hawaiian spinner dolphin, Stenella frontalis (Lammers et al., 2003). Whistles are thought to be used as signature whistles (Caldwell and Caldwell, 1990). This hypothesis was based on recordings of isolated bottlenose dolphins in captivity.Mostly likely the dolphin communication system under natural circumstances are more complicated than that. Using signature whistles for maintaining contact
Paper I between a mother and a calf seems reasonably, but in other situations the dolphins do not need to whistle a signature whistle. White-beaked dolphin whistles can be described by using frequency contours in spectrograms, 21 different whistles contours could be classified based on visual inspection of spectrograms as seen in papers I (whistles and clicks) and II (echolocation and social signals). 
Paper I published in Aquatic Mammals (2002) 28:78-89.


 



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