Burst pulses of Guiana dolphin (Sotalia guianensis) in southeastern Brazil.

Acoustic studies of Guiana dolphin have been focused on whistles, with little known about pulse signals in this species. This study characterized the temporal and spectral properties of Guiana dolphin burst pulses. Groups of 2 to 23 Guiana dolphins were recorded while feeding and socializing in shallow waters in Guanabara Bay, southeastern Brazil, in 2013 and 2014. Burst pulse analysis involved two steps: signal detection and acoustic parameter analysis. Eight variables were analyzed for 197 total burst pulses: number of clicks, burst pulse duration, interclick interval, click duration, peak frequency, center frequency, -3 dB bandwidth, and -10 dB bandwidth. Mean burst pulse duration was 108.6 ms [standard deviation (SD) = 91.3] with a mean of 168 clicks (SD = 137.3). Burst pulses had short interclick interval (0.7 ms, SD = 0.3) and mean click duration of 300 µs (SD = 100). Mean peak frequency and center frequency were 28 kHz (SD = 11.6) and 29 kHz (SD = 11.0), respectively. Mean -3 dB bandwidth was 15 kHz (SD = 7.5) and mean -10 dB bandwidth was 40.5 kHz (SD = 14.3). The quantitative characterization of Guiana dolphin burst pulses is an important step in describing the full acoustic repertoire of this species.

High-frequency whistles of Guiana dolphins (Sotalia guianensis) in Guanabara Bay, southeastern Brazil.

Guiana dolphins produce whistles with a higher frequency and less complexity than most other delphinid species. The present study used a recording system with sampling rate of 192 kHz to describe the high-frequency whistles of Sotalia guianensis in Guanabara Bay, Rio de Janeiro. Eleven acoustic parameters (start, end, minimum, maximum, delta, center and peak frequency, duration, and frequency at 14, 12, and 34 of duration) were measured for all whistles. Whistles with a fundamental frequency up to 66.7 kHz were reported, thereby expanding the known frequency range of this species.