Vocalizações subaquáticas e fenômenos não lineares em focas antárticas

Abstract

Pinnipeds produce a variety of underwater sounds that are often related to reproductive activities and social interactions. In addition, several species of seals provide evidence of vocalizations with geographical and individual variations. Most of bioacoustics researches with seals studied the terrestrial environment repertoire using linear analysis. However, some characteristics of vocalizations can not be explained with linear analysis only or taking into account only one part of the animal's life. The nonlinear phenomena (NLP) present in vocalizations (sideband, harmonic, sub-harmonic, biphonation, jump of frequency and deterministic chaos) are still poorly studied. Given the importance of this phenomena in vocalizations to individual recognition, especially in social mammals, was studied the underwater vocalizations of Antarctic seals in order to know their vocal repertoire and their NLP as well as discuss their possible function. In 2013, Brazilian Navy conducted acoustic recordings on Half Moon Island. In this collection were recorded 128GB of sound files between 12th and 30th of November. A total of 18 days of uninterrupted collections, producing 7,448 files of 3 minutes each. These recordings were taken at the presence of seals to Lobodontini Tribe. A total of 15 types of vocalizations were found in the period between days 12-16/November. A pattern in the vocalizations types L, K and E, arranged in sequence K, L and E, respectively, was observed in all seal recordings. All files presented biphonations, jumps of frequency, harmonics, sidebands and chaos in nine types of vocalizations (A, C, E, F, K, L, M, N and O). The nonlinearities were abundant on all files, being present in 75.56% (N = 1829) of vocalizations. Deterministic chaos was most common, present in 53.86% of non-linear features and 43.08% of vocalizations in general. Taking into account only the tonal vocalizations, 88.85% of vocalizations were nonlinear. The repetition of the KLE pattern also displays a recognition function. The NLP, mainly deterministic chaos, had high incidence in the studied vocalizations indicating that this type has an important role in communication. Furthermore, it seems to belong to the acoustic pattern of Antarctic‟s Lobodontines.