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Ecology and population structure of bottlenose dolphins and sperm whales in the Azores: assessing the relationship with habitat features

Referentie nr.: POCTI/BSE/38991/2001
Acroniem: CETAMARH
Periode: 2002 tot 2004
Status: Afgelopen

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Several ecological factors are known to strongly influence the ecology and social systems of cetaceans. The physical features of the habitat, system productivity, and distribution and abundance of predators, competitors and prey, are examples of ecological aspects acting on the distributional ecology, population biology and social structure of cetacean populations. As a result, cetaceans exhibit a wide range of ecological and social systems, which are found to be seasonally and geographically dependent. In spite of this observation, the precise nature and role of each ecological factor is still difficult to understand. Studies in distinct geographic areas, and most especially in different environments, would probably contribute to unravel this question. Taking the Azores Archipelago as a case study of a pelagic habitat, the present project intends to add to the diversity of ecological and social behaviours currently known, and provides an important opportunity for testing hypothesis about the ecological determinants of cetacean distributional ecology and social structure. It is a scientifically challenging objective as it may contribute to a better understanding of how social and ecological selective forces have influenced the evolution of complex societies in vertebrates - a central question to the theory of behavioural ecology. Scientific and conservationist reasons determined the choice of bottlenose dolphins (Tursiops truncatus) and sperm whales (Physeter macrocephalus) as target species of the project: as highly social species with a complex organization, they are ideal objects for a study on social structure; different groups have been identified in the area, rendering the question of population structure both pertinent and urgent; information on migration patterns of sperm whales is scarce but considered a priority for scientific and management reasons; the bottlenose dolphin is included in Appendix II of the Habitats Directive and is a priority species to the EU; sperm whales are the main focus of the whale-watching activity in the Azores, being subjected to unknown levels of disturbance. This project intends to use and further develop different research approaches, combining an already accredited method (photo-identification) with innovative techniques (population genetics, ecotoxicology and acoustics), which will complement each other. The identification of individual animals using photographs of natural markings (photo-id) is the key method and will provide information on population structure, ecology and social organization of both species. Photo-id databases will be used to study distribution, movements and habitat use of individual animals, obtain information on group and population unit sizes, measure associations between individuals or groups and assess degree of interaction between them. Acoustics will be used to record the location, number, behaviour and spatial arrangement of groups and to examine interactions underwater. Acoustic recordings will also be used to study population structure by investigating differences in dialects between population units from different areas. Genetic techniques will help solve the question of population structure and to understand social organization, by providing information on the genetic relationships among population units (degree of differentiation and amount of gene flow between them) and on the identity, sex and kinship of individuals. Ecotoxicology will be used as a means to distinguish between population units, comparing contaminant burdens from animals of different areas.

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