Estrutura e contexto eto-ecologico do canto da população de Baleia-jubarte Megaptera novaeangliae, no ano 2000

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

To our knowledge, this is the first study of the song of the Brazilian population of Humpback Whale Megaptera novaeangliae in its breeding and calving ground. Digital recordings (DAT) were made at the Abrolhos Bank, Bahia, from July to November 2000. Aural and spectral analyses were carried out for approximately 20 song cycles, in a total of 5 hours of songs from 10 different recording events. The end of a song session was recorded once. Note types were classified using acoustical parameters, namely: duration, length of the intervals between them, minimum and maximum frequencies. The rhythm of note utterance was also measured. We identified twenty-four note types, organized in 5 themes (each theme has one or more types of phrases). All themes are shared by all singers. In contrast to all other studies that we are aware of, in no occasion the singers in our sample omitted a particular theme or reversed the order in which they were sung. In one of the themes we found different types of phrases that contain the same kind of ending. Previous studies have suggested that this is a mnemonic device, analogous to the rhymes we use in our language, being its main purpose to facilitate the learning of the song alteration through time. Sometimes the passage from one theme to another occurs gradually. This is due to the occurrence of transitional phrases, in which notes of the two adjacent themes are emitted in the same phrases prior to the change of theme. These transitional phrases occur in the passage between two themes. One of the well established characteristics of the song is its irregular alteration through time, which seems always to occur during the breeding season. In the songs we have analyzed, we observed the appearance of a particular note type and the dissapearance of a particular phrase ending, and both seem to be related to the progression of the breeding season. Another characteristic is the fact that all individuals in a population tend to sing the same current version of the song. In contrast, we observed an individual variation in the performance of certain note types, which are all concentrated in the same theme. We believe that this variation is related to each singer s ability to compose and/or to learn the song alterations through time. From the observation that an individual variation in the song of the species exists, something to our knowledge not reported in any other study so far, we present the idea that a singer s ability to compose and/ or learn the song alterations through time influences his fitness

ASSUNTO(S)

baleia-jubarte - abrolhos canto arquipelagos dos bioacustica

ACESSO AO ARTIGO

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