Sotalia fluviatilis (Gervais, 1853) sound emissions characterization e during feeding behaviour in two beaches in Cananéia estuary, São Paulo. / Caracterização das emissões sonoras de Sotalia fluviatilis (Gervais, 1853) (Cetacea, Delphinidae) durante o comportamento alimentar em duas praias do estuário de Cananéia, São Paulo.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

This study had two objectives: to describe the sound emissions of Sotalia fluviatilis and to classify the analyzed whistles. During August and December, 2002, whistle emissions were recorded from solitary individuals and groups of 2 to 10 individuals that, in order to capture preys, approached Pereirinha (Ilha do Cardoso) and Ponta da Trincheira (Ilha Comprida) beaches in Cananéia estuarine complex, São Paulo. A hydrophone (HTI SSQ 94), connected to a professional analog audio tape recorder (SONY TCM 5000ev) was used to capture the emissions. In 22 hours of acoustic data, 3.188 whistles (74,5%), 689 echolocation click sequences (16%) and 406 burst pulses (9,5%) were reported; totalling 4.283 sound emissions. This represents 0,93 emissions/minute/individual. Only the emissions with clear visualization and up to 20kHz were analyzed (61%). The whistles were classified in two ways: by human observation technique and through the multivariate analysis. Using human observation, 1.592 whistles were quantitatively classified in 5 categories, according to the physical shape of the contour resulting from the number of inflection points presented in the whistle. Whistles with up to 4 inflection points were found. Most of the whistles (89%) did not show inflection points; moreover, there were considerably more whistles with rising frequency. (87%). Only 213 (13,3%) whistles had harmonics. The average duration of the 1.592 whistles was 0,23s (but varied between 0,04 and 0,64s). The frequency modulation of the whistles varied between 1,01 and 19,98 (mean = 7,22kHz). Variations were found when compared to other studies carried out on S. fluviatilis; nevertheless, this occurred due to differences in methodology, recorder equipment and data analysis. Furthermore, varieties of habitats and the ecological and behavioral context between freshwater and marine ecotypes of S. fluviatilis must be considered. The results of the multivariate analysis, applied to the 1.592 whistles, were very different to the results of the human observation technique (univariate method). The multivariate analysis links all measured acoustics; forming whistle groups. Four groups were formed by this method; they showed whistles with varying numbers of inflection points. There are few studies that classify whistles of odontocetes according to multivariate analysis. This kind of study is important to comparisons between different populations. The qualitative and quantitative descriptions of the whistles are necessary for future comparisons among populations from different geographic regions along the species distribuition. This study reported important ecological relationships and can contribute to the efforts of preservation.

ASSUNTO(S)

tucuxi sound emissions clicks tucuxi sotalia fluviatilis clicks emissões sonoras sotalia fluviatilis whistles assobios

ACESSO AO ARTIGO

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