Ontogenia do Padrão Vocal Individual do Peixe-Boi da Amazônia Trichechus inunguis (Sirenia, Trichechidae)




There are evidences that Amazonian manatee convey identity information, to its conspecifics, using sounds. Evidences about the presence of vocal signature and individual recognition have been documented in the specie. However, there is little information about the vocal behavior and the development of the individual vocal pattern for this species. The vocalizations of thirty eight individuals living in captivity at INPA had their vocalizations recorded throughout eleven years. The calling rates from these animals were compared across age classes and sexes. Three females that reproduced in captivity also had their calling rates compared in two different stages: lactating and non-lactating. Lactating females and calves presented higher calling rates than the others, emphasizing that the main role of manatees acoustic communication is the mainentance of proximity between mother and calf. Aiming to verify if the variability within individual vocal pattern would tend to decrease with age, we analyzed vocalizations of twenty three individuals. We performed spectrographic cross-correlation of vocalizations emitted by each animal, within each recording day. The resulting similarity indexes were plotted across time for each individual. The similarity indexes did not show any clear tendency of increase or decrease across time. We also investigated intra-individual variations in some acoustic parameters. Among them, only the maximum fundamental frequency showed significant increase in five individuals that were analyzed during the change of age class from calf to juvenile. When we compared the acoustic parameters within age classes and sexes, we did not find any significant differences in the fundamental range or in the maximum fundamental frequency. Only signal duration showed a significant difference among age classes, more specifically, between calves and adults, with longer signal durations in adults. There wasnt a significant difference in signal duration between calves and juveniles, or between juveniles and adults. A calf born in captivity was recorded since birth. In this case study, we observed that the similarity between the calfs vocalizations and those from his mother increased through time, suggesting the existence of vocal learning in this species.


sirenia zoologia peixe-boi vocalização ontogenia. bioacústica trichechus inunguis peixe-boi comportamento

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