Cetaceans are aquatic mammals that rely primarily on sound for most daily tasks. A compendium of sounds is emitted for orientation, prey detection, and predator avoidance, and to communicate. Communicative sounds are among the most studied Cetacean signals, particularly those referred to as tonal sounds. Because tonal sounds have been studied especially well in social dolphins, it has been assumed these sounds evolved as a social adaptation. However, whistles have been reported in ‘solitary’ species and have been secondarily lost three times in social lineages. Clearly, therefore, it is necessary to examine closely the association, if any, between whistles and sociality instead of merely assuming it. Several hypotheses have been proposed to explain the evolutionary history of Cetacean tonal sounds. The main goal of this dissertation is to cast light on the evolutionary history of tonal sounds by testing these hypotheses by combining comparative phylogenetic and field methods. This dissertation provides the first species-level phylogeny of Cetacea and phylogenetic tests of evolutionary hypotheses of cetacean communicative signals. Tonal sounds evolution is complex in that has likely been shaped by a combination of factors that may influence different aspects of their acoustical structure. At the inter-specific level, these results suggest that only tonal sound minimum frequency is constrained by body size. Group size also influences tonal sound minimum frequency. Species that live in large groups tend to produce higher frequency tonal sounds. The evolutionary history of tonal sounds and sociality may be intertwined, but in a complex manner rejecting simplistic views such as the hypothesis that tonal sounds evolved ‘for’ social communication in dolphins. Levels of social and tonal sound complexity nevertheless correlate indicating the importance of tonal sounds in social communication. At the intraspecific level, tonal sound variation in frequency and temporal parameters may be product of genetic isolation and local levels of underwater noise. This dissertation provides one of the first insights into the evolution of Cetacean tonal sounds in a phylogenetic context, and points out key species where future studies would be valuable to enrich our understanding of other factors also playing a role in tonal sound evolution.

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No. of bitstreams: 1 brunaribeiroduque.pdf: 1742764 bytes, checksum: f627a5ce49adc9ffbc23310a410912ca (MD5) Previous issue date: 2017-03-24 / Assobios são emitidos por golfinhos para a comunicação entre indivíduos da mesma espécie, transmitindo informações que possibilitam a identificação individual e a coordenação do grupo. Devido a este fato, os assobios apresentam características que os diferenciam de maneira espécie-específica. Um crescente número de estudos têm utilizado este tipo de vocalização para a identificação de espécies, mas poucos no contexto de associações interespecíficas. Portanto, informações acerca da relação entre estas associações e as propriedades dos assobios representam um importante aspecto a ser compreendido. Nestas circunstâncias, o objetivo deste trabalho foi classificar e caracterizar os assobios emitidos pelas espécies Globicephala melas (baleia-piloto-de-peitoral-longa) e Tursiops truncatus (golfinho-nariz-de-garrafa) registradas durante uma interação na região da plataforma continental e talude sul brasileiro, Oceano Atlântico Sul. Os dados acústicos foram coletados oportunisticamente em maio de 2014 por dois hidrofones de uma matriz de arrasto Auset® (resposta de frequência: 1,592 a 48 kHz) rebocada pela popa do navio R/V Atlântico Sul e acoplada a um gravador digital Fostex FR-2 LE (amostragem de 48 kHz/24 bits). Um total de 418 assobios foram analisados, dos quais 117 foram classificados visualmente como G. melas e 301 como T. truncatus. A análise discriminante multivariada mostrou uma taxa de classificação correta de 97,99%. Os assobios de contorno constante foram comumente mais produzidos pela espécie G. melas (N = 50; 46,73%), enquanto para T. truncatus a categoria múltiplo ocorreu em maior frequência (N = 131; 46,13%). O golfinho-nariz-de-garrafa produziu sinais com médias de frequência maiores do que a baleia-piloto-de-peitoral-longa, em contrapartida esta espécie apresentou coeficiente de variação com valores mais altos para a maioria das variáveis. Os assobios de G. melas variaram de 1,64 a 13,93 kHz, enquanto os assobios de T. truncatus alcançaram frequências entre 5,03 e 23,91 kHz. As duas espécies emitiram assobios com média de duração próxima e com número de pontos de inflexão acima de um. Foram encontradas diferenças nos parâmetros acústicos dos assobios em relação a estudos com outras populações das duas espécies. As diferenças interespecíficas podem estar relacionadas à sobreposição de habitat e às características corporais de G. melas e T. truncatus, ao passo que as variações intraespecíficas podem ser ocasionadas devido à gama de contextos populacionais e ecológicos aos quais as populações estão submetidas. / Dolphins emit whistles for communication among individuals of the same species, transmitting information that enables individual identification and group cohesion. Due to this fact, whistles show characteristics that differentiate them in a species-specific way. An increasing number of studies have used this type of vocalization to identify species, but few of them were carried out in interspecific association contexts. Thus, information about the relationship between these associations and whistles properties represent an important aspect to be understood. In these circumstances, the aim of this work was to classify and characterize the whistles emitted by Globicephala melas (long-finned pilot whale) and Tursiops truncatus (bottlenose dolphin) recorded during an interaction in the Brazilian south continental shelf and slope, South Atlantic Ocean. The acoustic data were opportunistically collected in May 2014 using two hydrophones of an Auset® array (response frequency: 1,592 to 48 kHz) towed through the stern of the R/V Atlântico Sul and coupled to a Fostex FR-2 LE digital recorder (sampling of 48 kHz/24 bits). A total of 418 whistles were analyzed, 117 of which were visually classified as emitted by G. melas and 301 by T. truncatus. The multivariate discriminant analysis showed a correct classification rate of 97.99%. Constant whistles were more commonly produced by G. melas (N = 50, 46.73%), while for T. truncatus the multiple category occurred more frequently (N = 131, 46.13%). The bottlenose dolphin produced whistles with higher mean frequencies than the long-finned pilot whale, in contrast, this species showed a coefficient of variation with higher values for most variables. G. melas whistles varied from 1.64 to 13.93 kHz, while T. truncatus whistles ranged between 5.03 and 23.91 kHz. Both species emitted whistles with near mean duration and number of inflection points above one. Differences were found in whistles acoustic parameters in relation to studies with other populations. We hypothesize that interspecific differences may be related to habitat overlapping and body characteristics of G. melas and T. truncatus, whereas intraspecific variations can be caused due to the range of population and ecological contexts to which the populations are submitted.