Assobios do boto-cinza, Sotalia guianensis, (Cetacea, Delphinidae) em três áreas de concentração na costa do Rio de Janeiro

Abstract

The species Sotalia guianensis presents a varied repertoire of whistles that are linked to social interaction and different contexts of behavior. The intraspecific variations in thestructures of whistles may indicate differences between populations of this species. This study characterized and compared the repertoire of Sotalia guianensis whistles in three bays of Rio de Janeiro: Guanabara Bay (BG), Sepetiba Bay (SB) and Ilha Grande Bay (BI), using a system recording upper limit frequency of 48 kHz and by applying the quantitative and qualitative analysis of acoustic parameters. The recordings of whistles were performed by vessels of 5.5 and 7m and recording system consists of a hydrophone High Tech, model HTI-96-MIN, and a digital recorder Marantz Model PMD 671, with upper limit frequency of 48 kHz. The analysis of the spectrograms were made with Adobe Audition 1.5 and Raven 1.3. The whistles were classified into six categories of shape and contour of 11 acoustic parameters were measured for each whistle. To compare the acoustic parameters of the same form of boundary among the three bays, were applied to descriptive analysis and statistical tests of comparison of average. A total of 1800 whistles was selected and 61.38% (N = 1105) showed whistles outline form up. Whistles with zero or one point of inflection were more common (N = 1476), corresponding to 82%. The frequency range found was between 1.03 to 46.87 kHz, the greater range record for this species in Brazil. The average duration of whistles from BG was lower than the averages found in the BS and BI. The results of all comparisons showed that the parameters of frequency (FI, FF, FMAX and F3/4) were the most significant differences among the three areas. The variation found in the whistles of S. guianensis between the three study areas may also be linked to the types of whistles most common in each area, represented by the ascending whistles, that even using the same contour form, have differences in their acoustic parameters, possibly linked to individual information. The use of a recording system with the upper limit of 48 kHz allowed the analysis of many assobios.Com it was possible to verify the importance of the frequency limit used to characterize the acoustic repertoire of this species, together with qualitative analysis of the forms of contour and quantitative analysis of the acoustic parameters of whistles. The application of this methodology was effective in intraspecific comparison of whistles, and in the future, more detailed studies of the classification of whistles, you can add relevant information about the variation of this type of noise in the acoustic repertoire S. guianensis