Vocalizations of a Wild Finless Porpoise (Neophocaena asiaeorientalis sunmeri) in the Western Coast of the Taiwan Strait, China

Abstract

Vocalizations of a wild finless porpoise (Neophocaena asiaeorientalis sunmeri) were recorded within the dolphin natural reserve, in the western coast of the Taiwan Strait, China. The subsequent acoustical analyses suggested that the porpoise (N. p. sunameri) produced typical phocoenid clicks, with the peak frequency ranging from 123.4 to 141.4 kHz, averaging at 132.8±4.02 kHz (n = 193). The durations of these typical signals ranged from 97 to 130 microseconds, averaging at 111.6±8.49 (n = 193) microseconds. The 3 dB bandwidth had a scope from 5.8 to 15.6 kHz, averaging at 10.49±1.84 kHz (n = 193). For typical clicks, the energy converged on a narrowband frequency range with peak frequency over 120 kHz. The acoustic parameters of the signals were compared with those of signals emitted by finless porpoises from other living regions. Besides, the broadband clicks were also recorded and reported here. The sound energy was more diffuse in frequency domain for the broadband clicks than typical narrowband ones, extending to below 50 kHz and above 180 kHz. During the recordings, the reverberations influenced the signals, shown in both time and frequency domains. The reverberations could disperse the energy of the original narrowband and broadband clicks into several peak frequency ranges. For the signals used by porpoise for echolocation, the noise caused by man-made activities could influence the marine mammal negatively. The researches into porpoise's signals could provide references to protect the animal.