Influence of natural and anthropogenic sound sources on the soundscape of the Cananéia estuary, southeastern Brazil.

The aim of this study is to characterize the background noise and abiotic and anthropogenic sound sources in the sector with greater anthropogenic use of the Cananéia estuary. The results show that the relative amplitude of background noise decreased with the increase of frequency range, and was higher with greater number of vessels, wind speed and during flood tide. Weekends and vacation periods were shown to be important dates during which background noise increased in the region. The influence of the tide and the wind speed on the relative amplitude was dependent on the frequency range analyzed. Therefore, both abiotic and anthropogenic sound sources were observed to be important factors regarding an increase in background noise in Cananéia. The importance of the continuity of vessel regulation in the region and of future studies that identify whether such noises alter parameters from the sound repertoire of the cetacean species in the region.

High initial and minimum frequencies of Sotalia guianensis whistles in the southeast and south of Brazil.

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).