Variation in Guiana dolphin (Sotalia guianensis) whistles: using a broadband recording system to analyze acoustic parameters in three areas of southeastern Brazil

The Guiana dolphin produces a variable whistle repertoire related to different social contexts. The current study evaluates Guiana dolphin whistles at a microscale. Acoustic parameters of whistles were compared between three areas in southeastern Brazil using a recording system with sampling rate of 96 kHz. Previous studies that utilized a sampling rate of 48 kHz reported little variation between adjacent areas in Brazil. Nine acoustic parameters of the whistles (duration, start, end, minimum and maximum frequencies, delta frequency, frequency at 1/4, 1/2, and 3/4 of duration) were measured and whistles were classified into five contour forms. A total of 659 whistles were analyzed, of which 62.20 % showed an ascending contour form. The Guiana dolphin emitted whistles with a fundamental frequency reaching 44.9 kHz. Dolphin whistles from the three study areas varied significantly in nine acoustic parameters. The whistle duration was shorter (272.44 +/- 105.25 ms) in Guanabara Bay than those in Sepetiba (360.05 +/- 135.16 ms) and Paraty Bays (376.80 +/- 159.78ms). The start and minimum frequencies of the whistles in Guanabara Bay was significantly higher than those in Sepetiba and Paraty Bays. The results of discriminant function analysis indicated a significant difference between Guanabara Bay and the other two areas. Comparisons of the ascending, descending-ascending, and multi whistles between areas showed differences in some acoustic parameters. In this study, by doubling the sampling rate in our recording systems, we were able to more accurately sample the whistle repertoire of Guiana dolphins in southeastern Brazil, and thereby detect differences in whistles between neighboring populations.