Recent studies have proposed latitudinal variations for the whistles of Sotalia guianensis, since parameters of frequency increase from the southernmost distribution of the species (State of Santa Catarina, Brazil) toward the North. The last study on the whistles of S. guianensis, conducted in Costa Rica, confirmed the geographical variation of whistles, regardless of frequency responses used in the samples. Initial and minimum frequencies of whistles of the Costa Rican populations were higher than were the frequencies of Brazilian populations. In this current study, the whistles of S. guianensis were recorded with a sampling frequency of 48 kHz, the highest frequency band used in Brazilian studies. The initial and minimum frequency of whistles recorded and analyzed were similar to parameters of Costa Rican populations and show little or no difference when compared to the average of each study. Therefore, whistle frequency variables do not increase with latitude. It is likely that variations in acoustic parameters S. guianensis are mainly linked to environmental characteristics of the habitats in which the populations occur. Thus, the repertoire sound S. guianensis appears linked to similar environments with similar physical characteristics and not linked to population characteristics (dialects).

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