Caracterização dos sons explosivos de boto-cinza (Sotalia guianensis) (Van Bénéden, 1864) no norte do estado do Espírito Santo - Brasil

Abstract

Acoustic studies of the Guiana dolphin (Sotalia guianensis) have been focused on whistles, and little is known about pulsed signals in this species. Pulsed signals are broadband sounds and include echolocation clicks and bursts. Burst sounds are characterized by high frequencies, short inter-click interval and a high repetition rate and are commonly associated with an intraspecific communicative function, but their function has still been widely discussed. This study aimed to characterize spectral and temporal parameters of the burst sounds of the Guiana dolphin in the north of the state of Espírito Santo, Brazil. The analysis of the vocalizations involved two steps: signal detection and analysis of acoustic parameters. In all, 12 variables were analyzed for 21 explosive sounds: number of clicks, inter-click interval, duration, peak frequency, center frequency -3 dB and -10 dB, bandwidth -3 dB and -10 dB, minimum frequency -3 dB and -10 dB and maximum frequency -3 dB and -10 dB. It was observed that the duration of the Guiana dolphin's explosive sound ranged from 0.01 to 0.10s (0.05±0.03s). The interval between clicks ranged from 0.2 to 9.8 milliseconds (0.9±0.4ms). Peak frequency values ranged from 60 to 96.4 kHz (73.66±5.63 kHz). The central frequency values of -3 dB varied between 59.73 and 96.58 kHz (73.75±5.74 kHz) while the central frequency of -10 dB varied between 10.04 and 94.86 kHz (73.56±5.01 kHz). The frequency of the -3 dB bandwidth ranged from 3.48 to 70.14 kHz (6.74±1.57 kHz). Bandwidth values of -10 dB were between 5.62 to 49.34 kHz (20.40±6.95). The quantitative characterization of the explosive sounds of the Guiana dolphin is an important step in the description of the complete acoustic repertoire of this species.