Burst-pulsed sounds of rough-toothed dolphins (Steno bredanensis) in Southeastern Brazil

Abstract

Recordings of Steno bredanensis were done in Southeastern Brazilian coast during eleven days between 2013 and 2017. The system consisted of a C54-XRS hydrophone (−165 dB re: 1 V/μPa, 0.009 to 100 kHz) and a Fostex FR-2 digital recorder with a 192 kHz sample rate. Recordings were inspected for burst-pulsed sounds in Adobe audition 1.5 software in a 512 Hann window, 50% overlap. When they were found, the sound was cut to a new file of 2-s window, and a butterworth high-pass filter was used when necessary. A burst-pulse sound was considered for analysis when its pulses were correctly and clearly identified in the Sound Ruler software, which was used to obtain the acoustic parameters (512 Hann window, 50% overlap). Thirty-one burst pulsed sounds were analyzed. The mean number of pulses per burst-pulse was 52 ± 44 (varying between 6 and 224), mean inter-pulse interval was 5.1 ± 1.9 ms (varying between 2.4 and 8.4 ms), mean burst-pulse duration was 0.27 ± 0.23 s (varying between 0.04 and 1.1s), and mean peak frequency was 26.1 ± 11.3 kHz (varying between 7.0 and 64.7 kHz). Although preliminary, these results show a first characterization of the burst-pulsed sounds of this species.