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Publication
Association patterns of resident bottlenose dolphins in the region of the Sado estuary
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Authors
Abstract(s)
A vida social é uma caraterística importante dos mamíferos, onde é comum a formação
de grupos constituídos por associações dinâmicas e não aleatórias. A rutura destas relações é
causada por alterações no ambiente e afetará a sua conetividade, ecologia e estabilidade. Assim,
a estrutura social é uma caraterística importante para a conservação e gestão de uma população.
A população residente de golfinhos roazes no Estuário do Sado é atualmente constituída
por 28 indivíduos, 20 adultos, 5 juvenis e 3 crias. Trata-se de uma população pequena e
envelhecida que apresenta filopatria e reduzido contacto com indivíduos não residentes. A
dimensão média dos grupos foi de 5,7 indivíduos, sendo os grupos mais comuns constituídos
por adultos, ou adultos e crias. A dimensão média dos grupos foi também analisada de acordo
com a atividade dominante, revelando-se semelhante para todas as atividades.
O software SOCPROG V. 2.9 foi utilizado para analisar a estrutura social e identificar
padrões de associação. As "associações preferenciais de curto prazo" prevaleceram entre e
dentro das classes de idade e sexo, e o coeficiente médio de associação foi de 0,15. Estas
características são típicas de uma sociedade do tipo fissão-fusão, com baixo coeficiente de
associação e associações preferenciais de curto prazo, comuns para esta espécie.
Este estudo atualiza o estado desta população no que diz respeito à estrutura social. As
medidas de conservação aplicadas para esta população devem ser ajustadas para contemplar os
padrões de associação e a dinâmica populacional, especialmente associações importantes como
as díades mães-crias.
ABSTRACT: Social life is an important feature for mammals, where it is common to form groups that are made up of dynamic, non-random associations. The disruption of this relationships is caused by changes in the environment and will affect its connectivity, ecology and stability. Therefore, social structure is an important feature for the conservation and management of a population. The resident population of bottlenose dolphins in the Sado Estuary currently consists of 28 individuals, 20 adults, 5 juveniles and 3 calves. This is a small and aged population that show philopatry and reduced contact with non-resident individuals. The average group size was 5.7 individuals, with the most common groups consisting of adults, or adults and calves. Mean group size was also analysed according to the dominant activity and was similar for all activities. SOCPROG V. 2.9 software was used to analyse the social structure and identify patterns of association. "Short-term preferential associations" prevailed between and within age and sex classes, and the mean coefficient of association was 0.15. These characteristics are typical of a fission-fusion type society, with low coefficient of association and short-term preferential associations, common for this species. This study updates the state of this population regarding social structure. Conservation measures applied for this population should be adjusted to address the association patterns and the population dynamic, especially important associations such as mother-calves’ dyads.
ABSTRACT: Social life is an important feature for mammals, where it is common to form groups that are made up of dynamic, non-random associations. The disruption of this relationships is caused by changes in the environment and will affect its connectivity, ecology and stability. Therefore, social structure is an important feature for the conservation and management of a population. The resident population of bottlenose dolphins in the Sado Estuary currently consists of 28 individuals, 20 adults, 5 juveniles and 3 calves. This is a small and aged population that show philopatry and reduced contact with non-resident individuals. The average group size was 5.7 individuals, with the most common groups consisting of adults, or adults and calves. Mean group size was also analysed according to the dominant activity and was similar for all activities. SOCPROG V. 2.9 software was used to analyse the social structure and identify patterns of association. "Short-term preferential associations" prevailed between and within age and sex classes, and the mean coefficient of association was 0.15. These characteristics are typical of a fission-fusion type society, with low coefficient of association and short-term preferential associations, common for this species. This study updates the state of this population regarding social structure. Conservation measures applied for this population should be adjusted to address the association patterns and the population dynamic, especially important associations such as mother-calves’ dyads.
Description
Dissertação de Mestrado realizada sob a orientação de
Manuel Eduardo dos Santos, apresentada no Ispa –
Instituto Universitário para obtenção de grau de Mestre na
especialidade de Biologia Marinha e da Conservação.
Keywords
Tursiops truncatus Estrutura social Padrões de associação Díades Mães-crias Tursiops truncatus Social structure Association patterns Dyads Mother-calves