Academic literature on the topic 'Toothed whales Toothed whales Cetacea'

Abstract Thin-layer isoelectric focusing was applied to the identification of whale (Cetacea) species by using water-soluble sarcoplasmic proteins of skeletal muscles. Twenty-eight samples consisting of 4 species (10 samples) of baleen whales (Mysticeti) and 8 species (18 samples) of toothed whales (Odontoceti) were analyzed. Each sample (approximately 1 g) was electrophoresed with Ampholine PAGplate, pH 3.5-9.5. The electrophoretic profiles were species-specific on the 4 toothed whale species that did not have a marked intra-species difference, and all 4 baleen whale species. However, the profiles were not specific on the 4 other dolphin species, even though they were discriminable from the other 4 toothed whale species. Numerical values of pls and relative peak heights were obtained by densitometric analysis of the isoelectro-focused protein bands. The bands were also species-specific for the 8 toothed whale species mentioned. The values may be applicable to species identification without the need for a standard sample, which may not be readily obtainable. Experiments on test samples of minke and sei whales showed that bloodletting with ice water made the densities of isoelectro-focused bands thinner, although species identification was still possible by using the Inside part of muscles. Heat treatment at below 60°C for 10 min caused little denaturation; at higher temperatures the protein bands were diminished in a temperature-dependent fashion. Therefore, the present isoelectric focusing analysis should be applicable to small samples of whale meat, excluding several species of dolphins.

Cetacean karyotypes possess exceptionally stable diploid numbers and highly conserved chromosomes. To date, only toothed whales (Odontoceti) have been analyzed by comparative chromosome painting. Here, we studied the karyotype of a representative of baleen whales, the gray whale (Eschrichtius robustus, Mysticeti), by Zoo-FISH with dromedary camel and human chromosome-specific probes. We confirmed a high degree of karyotype conservation and found an identical order of syntenic segments in both branches of cetaceans. Yet, whale chromosomes harbor variable heterochromatic regions constituting up to a third of the genome due to the presence of several types of repeats. To investigate the cause of this variability, several classes of repeated DNA sequences were mapped onto chromosomes of whale species from both Mysticeti and Odontoceti. We uncovered extensive intrapopulation variability in the size of heterochromatic blocks present in homologous chromosomes among 3 individuals of the gray whale by 2-step differential chromosome staining. We show that some of the heteromorphisms observed in the gray whale karyotype are due to distinct amplification of a complex of common cetacean repeat and heavy satellite repeat on homologous autosomes. Furthermore, we demonstrate localization of the telomeric repeat in the heterochromatin of both gray and pilot whale (Globicephala melas, Odontoceti). Heterochromatic blocks in the pilot whale represent a composite of telomeric and common repeats, while heavy satellite repeat is lacking in the toothed whale consistent with previous studies.

Abstract Kiszka, J., Macleod, K., Van Canneyt, O., Walker, D. and Ridoux, V. 2007. Distribution, encounter rates, and habitat characteristics of toothed cetaceans in the Bay of Biscay and adjacent waters from platform-of-opportunity data. – ICES Journal of Marine Science, 64: 1033–1043. Data on the distribution and habitat utilization of oceanic marine mammals are difficult to collect and yet such information is beneficial for many conservation and management purposes. Data collected during ferry-based cetacean surveys in the English Channel and Bay of Biscay between 1998 and 2002 were analysed to investigate the distribution, encounter rate, and habitat characteristics of toothed cetaceans there. In all, 17 873 nautical miles were surveyed, and 1008 encounters of 13 identified species, including delphinids, ziphiids, harbour porpoise, and sperm whale, were recorded. The common dolphin was the commonest species, followed in decreasing occurrence by striped and bottlenose dolphins, pilot whale, harbour porpoise, Cuvier's beaked whale, and sperm whales. The distribution of harbour porpoises was restricted to the shallow waters of the western English Channel. Common and bottlenose dolphins were distributed mainly over the continental shelf, although there were some encounters along the shelf edge and in the open ocean. Striped dolphins and pilot whales were sighted in oceanic waters in the central and southern Bay of Biscay. Cuvier's beaked whales and sperm whales were recorded in the deep oceanic waters of the southern Bay of Biscay. Bathymetry clearly plays a significant role in the distribution and habitat partitioning of toothed cetaceans in the region.

A series of visual–acoustic surveys were carried out in the Mediterranean Sea between 2003 and 2007 from RV ‘Song of the Whale’. Almost 21,000 km of trackline were surveyed between the longitudes of 14°W and 36°E with an emphasis on regions with low survey effort. Survey tracklines were designed to provide even coverage probability with random start points. Ten cetacean species were positively identified (sperm whale, fin whale, Cuvier's beaked whale, false killer whale, long-finned pilot whale, Risso's dolphin, common bottlenose dolphin, rough-toothed dolphin, striped dolphin and short-beaked common dolphin). Several of these species, plus sei whale and harbour porpoise, were also encountered in the Atlantic contiguous area (the entrance waters of the Mediterranean between the Iberian Peninsula and north-west Morocco). These surveys expand and clarify the known distributions of cetaceans within the Mediterranean basin. New species documented from Libyan waters include sperm whale, striped dolphin and rough-toothed dolphin. False killer whales and rough-toothed dolphins were documented for the first time off Cyprus. Live harbour porpoises were seen for the first time on Morocco's Atlantic seaboard. It is suggested that the status of rough-toothed dolphins in the Mediterranean be revised from visitor to regular species. Substantial new information on encounter rates is now available for the planning of a basin-wide systematic survey of cetaceans within the Mediterranean Sea and contiguous Atlantic waters.

The Polar branch of Russian Federal Research Institute of Fisheries and Oceanography (VNIRO) carries out annually comprehensive surveys in the Barents Sea. This allows obtaining relevant data on distribution and occurrence of marine mammals, in particular cetaceans – the key link in the World Ocean ecosystem. In recent years, marine mammals monitoring has become increasingly important due to climate change and temperature rise in seas and oceans, that can result in habitat displacement and even possible extinction of certain species. This article summarizes the results of the vessel surveys of cetaceans carried out by the Polar branch of VNIRO in the Barents Sea in 2010–2019, as well as provides retrospective data on baleen whales (Mysticeti) and toothed whales (Odontoceti). Based on vessel survey material and taking into account data from literature sources, the current composition of the Barents Sea cetacean fauna is presented; at the beginning of the XXI century, it may include up to 16 species of 7 families. The analysis of vessel survey data made it possible to determine the status of marine mammals of this water area and to identify the frequency of their occurrence. The article presents population abundance for most species of baleen and toothed whales and shows the most likely spots of cetacean occurrence. According to the data obtained, white-beaked dolphin Lagenorhynchus albirostris is the most abundant, frequently sighted, and a year-round species: it accounts for more than 80 % of the total number of surveyed animals and about 50 % of all sighted cetaceans. Beluga whale Delphinapterus leucas and harbor porpoise Phocoena phocoena are also classified as permanent residents of the water area, and their localization is mainly confined to the Kola Peninsula coastal zone. May to October, the Barents Sea is regularly visited by species arriving from other Atlantic Ocean areas for feeding: minke whale Balaenoptera acutorostrata, fin whale Balaenoptera physalus, and humpback whale Megaptera novaeangliae. Narwhal Monodon monoceros and northern bottlenose whale Hyperoodon ampullatus are rarely sighted in the Russian Arctic western area.

Several aspects of the fascinating evolutionary history of toothed and baleen whales (Cetacea) are still to be clarified due to the fragmentation and discontinuity (in space and time) of the fossil record. Here we open a window on the past, describing a part of the extraordinary cetacean fossil assemblage deposited in a restricted interval of time (19–18 Ma) in the Chilcatay Formation (Peru). All the fossils here examined belong to the Platanistoidea clade as here redefined, a toothed whale group nowadays represented only by the Asian river dolphin Platanista gangetica. Two new genera and species, the hyper-longirostrine Ensidelphis riveroi and the squalodelphinid Furcacetus flexirostrum, are described together with new material referred to the squalodelphinid Notocetus vanbenedeni and fragmentary remains showing affinities with the platanistid Araeodelphis. Our cladistic analysis defines the new clade Platanidelphidi, sister-group to Allodelphinidae and including E. riveroi and the clade Squalodelphinidae + Platanistidae. The fossils here examined further confirm the high diversity and disparity of platanistoids during the early Miocene. Finally, morphofunctional considerations on the entire platanistoid assemblage of the Chilcatay Formation suggest a high trophic partitioning of this peculiar cetacean paleocommunity.

Baleen whales (mysticetes) lack teeth as adults and instead filter feed using keratinous baleen plates. They do not echolocate with ultrasonic frequencies like toothed whales but are instead known for infrasonic acoustics. Both baleen and infrasonic hearing are separately considered key innovations linked to their gigantism, evolutionary success and ecological diversity. The earliest mysticetes had teeth, and the phylogenetic position of many so-called toothed mysticetes remains debated, including those belonging to the nominal taxonomic groups Llanocetidae, Mammalodontidae and Aetiocetidae. Here, we report a new stem mysticete, Borealodon osedax gen. et sp. nov., from the Oligocene of Washington State, USA. Borealodon preserves multi-cusped teeth with apical wear; microCT scans of the inner ear indicate that the minimum frequency hearing limit of Borealodon was similar to mammalodontids. Borealodon is not recovered within a monophyletic Mammalodontidae nor a monophyletic Aetiocetidae; instead, it represents an unnamed lineage of stem Mysticeti, adding to the diversity of stem mysticetes, especially across the Rupelian–Chattian boundary. Furthermore, the presence of a putative chemosynthetic bivalve along with Osedax , a bone-boring annelid, found in association with the type specimen of Borealodon , offer more insights into the evolution of deep-sea whale-fall communities.

Extant baleen whales (Cetacea, Mysticeti) are all large filter-feeding marine mammals that lack teeth as adults, instead possessing baleen, and feed on small marine animals in bulk. The early evolution of these superlative mammals, and their unique feeding method, has hitherto remained enigmatic. Here, I report a new toothed mysticete from the Late Oligocene of Australia that is more archaic than any previously described. Unlike all other mysticetes, this new whale was small, had enormous eyes and lacked derived adaptations for bulk filter-feeding. Several morphological features suggest that this mysticete was a macrophagous predator, being convergent on some Mesozoic marine reptiles and the extant leopard seal ( Hydrurga leptonyx ). It thus refutes the notions that all stem mysticetes were filter-feeders, and that the origins and initial radiation of mysticetes was linked to the evolution of filter-feeding. Mysticetes evidently radiated into a variety of disparate forms and feeding ecologies before the evolution of baleen or filter-feeding. The phylogenetic context of the new whale indicates that basal mysticetes were macrophagous predators that did not employ filter-feeding or echolocation, and that the evolution of characters associated with bulk filter-feeding was gradual.

AbstractMonitoring whale strandings are a key aspect of ecosystem management as stranded animals can provide indications on ecosystem health, pollution and adverse effects due to anthropogenic activities. Most mass mortality events are reported for toothed whales and rarely involve baleen whales. In the course of one month in spring 2020, 17 whales belonging to seven different species, stranded on the shores of Northern Norway, above the Arctic circle. This multi-species event included humpback (Megaptera novaeangliae), fin (Balaenoptera physalus) and sperm whales (Physeter macrocephalus), that were accompanied by northern bottlenose whales (Hyperoodon ampullatus), a white-beaked dolphin (Lagenorhynchus albirostris), a long-finned pilot whale (Globicephala melas) and a harbour porpoise (Phocoena phocoena). We discuss some potential causes of death based on the previous literature and available information for the area, highlighting the need for further investigation on cetacean strandings at high latitudes. Ultimately, the reasons for the stranding could only be identified by a thorough examination of all the animals, which was unfortunately not conducted. As the threats to polar ecosystems and access to local shores are likely to increase, reports of cetacean mortality are also expected to surge, particularly in high latitude regions where climate variations and anthropogenic activities are increasing. This study makes recommendations for future steps and considerations for monitoring networks and standardized sampling methods for future marine mammal stranding events. Finally, we suggest that national and international efforts based on the collaborative relationships are implemented, considering the multiple facets of animal ecology and health as an achievable step in the near future.

Observations of whales and dolphins in the Cape Verde Islands obtained in 1995 and 1996 are reported and data on the occurrence of 14 taxa are given, including four not previously reported from the region, viz. Bryde’s Whale Balaenoptera edeni, Killer Whale Orcinus orca,Rough-toothed Dolphin Steno bredanensis, and Striped Dolphin Stenella coeruleoalba. An earlier report of Fin Whale B. physalus is reviewed and re-identified as B. cf. borealis. Status and occurrence of the Humpback Whale Megaptera novaeangliae are discussed at some length. Unpublished observations from other observers are also included and a short account on the history of whaling in the islands is given. A list of all cetacean taxa reliably recorded in the Cape Verde region is presented and unsubstantiated reports are briefly discussed.

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 2004.<br>Thesis advisor(s): Ching-Sang Chiu, Curtis A. Collins. Includes bibliographical references (p. 43-44). Also available online.

In search of evidence for or against the endothermic dinosaur hypothesis, a recent study by Ruben et al. (1996) revealed that endotherms tend to have larger nasal cross-sectional areas than ectotherms of the same mass. The reason offered for this observation was that larger nasal passages are needed to house the complex respiratory turbinates possessed by endotherms. Whales were excluded from the study on the grounds that they have no nasal turbinates. In the present study, the cross-sectional area of the nasal passages of nine species of Odontoceti were measured by the use of latex casts. The regression of log cross-sectional area vs. log mass yielded the same line for the whales of the current study as for the endotherms of the previous study. Alternative explanations for the large nasal cross-sectional area of endotherms are sought.

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Biology; and the Woods Hole Oceanographic Institution), 2016.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>To maintain the benefits of group membership, social animals need mechanisms to stay together and reunite if separated. This thesis explores the acoustic signals that dolphins use to overcome this challenge and mediate their complex relationships in a dynamic 3D environment. Bottlenose dolphins are the most extensively studied toothed whale, but research on acoustic behavior has been limited by an inability to identify the vocalizing individual or measure inter-animal distances in the wild. This thesis resolves these problems by simultaneously deploying acoustic tags on closely-associated pairs of known animals. These first reported deployments of acoustic tags on dolphins allowed me to characterize temporal patterns of vocal behavior on an individual level, uncovering large variation in vocal rates and inter-call waiting time between animals. Looking more specifically at signature whistles, a type of call often linked to cohesion, I found that when one animal produced its own signature whistle, its partner was more likely to respond with its own whistle. To better evaluate potential cohesion functions for signature whistles, I then modeled the probability of an animal producing a signature whistle at different times during a temporary separation and reunion from its partner. These data suggest that dolphins use signature whistles to signal a motivation to reunite and to confirm identity prior to rejoining their partner. To examine how cohesion is maintained during separations that do not include whistles, I then investigated whether dolphins could keep track of their partners by passively listening to conspecific echolocation clicks. Using a multi-pronged approach, I demonstrated that the passive detection range of echolocation clicks overlaps with the typical separation ranges of Sarasota mother-calf pairs and that the amount of time since an animal was last able to detect a click from its partner helped explain its probability of producing a signature whistle. Finally, this thesis developed a portable stereo camera system to study cohesion in situations where tagging is not possible. Integrating a GPS receiver, an attitude sensor and 3D stereo photogrammetry, the system rapidly positions multiple animals, grounding behavioral observations in quantitative metrics and characterizing fine-scale changes that might otherwise be missed.<br>by Nicholas Blair Wootton Macfarlane.<br>Ph. D.

The first objective of this PhD was to determine the degree of ecological segregation between five sympatric species of toothed whales (i.e. common dolphin Delphinus delphis, harbour porpoise Phocoena phocoena, bottlenose dolphin Tursiops truncatus, striped dolphin Stenella coeruleoalba and long finned pilot whale Globicephala melas) inhabiting a restricted and highly productive area, the North West Iberian Peninsula (NWIP). To this end, chemical parameters analyses were used as an "alternative method" of assessing diet and habitat of these animals over different periods of integration, complementing the information given by traditional methods of investigation such as stomach contents, faeces analyses and field observations. The second objective was to evaluate the contamination status of these species in order to estimate the toxicological risk these populations face and to complete the existing database. In this context, trace elements, carbon and nitrogen stable isotopes, as well as persistent organic pollutants (POPs) were selected as chemical parameters for our investigations.Firstly, the chemical parameters were used as ecological tracers of populations (or parts of populations) by drawing an image of the diet and habitat of the species at different time scales. We estimated that the food web has five trophic levels, with toothed whales occupying the top positions, with no significant difference in trophic positions among them, ranging from 4.3 to 5.3. While the analysis of a single chemical parameter did not completely segregate between the five species, the information gained by combining the analyses of several long-term ecological tracers (i.e. nitrogen and carbon stable isotopes in teeth and renal cadmium concentrations) revealed ecological niche segregation in two dimensions of this niche (the trophic and the spatial dimensions). However, year-to-year or seasonal variations could not be investigated, except for in common dolphin, and thus temporary overlap cannot be excluded. Additionally, we showed that polychlorinated biphenyls (PCBs) profiles could be a relevant tracer of the foraging ecology of taxonomically close species, allowing a fine separation of the species as result of their different patterns. This was particularly clear for the harbour porpoise and striped dolphin.Secondly, the contamination status of the species in this area was evaluated, with concentrations interpreted in the light of biological and ecological factors. But the bioaccumulation of trace elements appeared to be less predictable than that of POPs. Bottlenose dolphins and harbour porpoises were found to have higher PCBs concentrations than the rest of the analysed NWIP toothed whales, as well as those of adjacent NE Atlantic waters.The main results of this PhD highlight the relevance of exploiting these chemical parameters as ecological tracers, as well as their usefulness in the comprehensive study of structure and function of ecosystems through the role of top predators. Combined with the information on anthropogenic activities, this work can also contribute to the development and implementation of management plans and mitigation measures for these five species of toothed whales in the NWIP.

This study successfully utilised the non-invasive neuroimaging techniques of Computerised Tomography (CT) and Magnetic Resonance Imaging (MRI) to establish that dolphins have high relative brain size values, transcending the primate range for neocortex volume and neocortex ratio. Bottlenose dolphins superseded human values of the neocortex ratio and common dolphins marked the upper limit of the range for the dolphin species under investigation. In addition this study was the first to find a correlation between sociality and neocortex ratio in dolphins (R.I.M. Dunbar, pers.comm), which supports the hypothesis of neocortical development in relation to sociality/group size (Sawaguchi & Kudo 1990; Dunbar 1992) and social/Machiavellian intelligence (Byrne & Whiten 1988; Byrne 1995). The study devised new measures of relative brain size, including the grey-white matter and higher cortical ratios and these require further research before verification of their efficacy. Equations were calculated to allow estimation of: (1) MRI values of total brain volumes from CT values, (2) total brain volume from cranial volume using CT, (3) cerebral cortex volume from cranial or total brain volume (CT) and (4) cerebral cortex and cerebellar cortex volume from total brain volume (MRI). The effects of freezing and defrosting on volume and density of CT and MRI values were investigated. Additionally, the relationship between relative brain size (EQ) and sociality was investigated for other dolphin research, using previously published figures, but no significant correlations were found. Finally, dolphin values were compared to primate values for neocortex volume and neocortex ratio with the finding that the only primate within the dolphin range of neocortex was the human, positioned higher than the solitary humpback dolphin, but below all of the other, more socially complex, dolphin species.<br>Thesis (M.A.)-University of Natal, Durban, 1996.

Tese de doutoramento em Ciências (ramo de conhecimento em Biologia)<br>The first objective of this PhD was to determine the degree of ecological segregation between five sympatric species of toothed whales (i.e. common dolphin Delphinus delphis, harbour porpoise Phocoena phocoena, bottlenose dolphin Tursiops truncatus, striped dolphin Stenella coeruleoalba and long finned pilot whale Globicephala melas) inhabiting a restricted and highly productive area, the North West Iberian Peninsula (NWIP). To this end, chemical parameters analyses were used as an “alternative method” of assessing diet and habitat of these animals over different periods of integration, complementing the information given by traditional methods of investigation such as stomach contents, faeces analyses and field observations. The second objective was to evaluate the contamination status of these species in order to estimate the toxicological risk these populations face and to complete the existing database. In this context, trace elements, carbon and nitrogen stable isotopes, as well as persistent organic pollutants (POPs) were selected as chemical parameters for our investigations. Firstly, the chemical parameters were used as ecological tracers of populations (or parts of populations) by drawing an image of the diet and habitat of the species at different time scales. We estimated that the food web has five trophic levels, with toothed whales occupying the top positions, with no significant difference in trophic positions among them, ranging from 4.3 to 5.3. While the analysis of a single chemical parameter did not completely segregate between the five species, the information gained by combining the analyses of several long-term ecological tracers (i.e. nitrogen and carbon stable isotopes in teeth and renal cadmium concentrations) revealed ecological niche segregation in two dimensions of this niche (the trophic and the spatial dimensions). However, year-to-year or seasonal variations could not be investigated, except for in common dolphin, and thus temporary overlap cannot be excluded. Additionally, we showed that polychlorinated biphenyls (PCBs) profiles could be a relevant tracer of the foraging ecology of taxonomically close species, allowing a fine separation of the species as result of their different patterns. This was particularly clear for the harbour porpoise and striped dolphin. Secondly, the contamination status of the species in this area was evaluated, with concentrations interpreted in the light of biological and ecological factors. But the bioaccumulation of trace elements appeared to be less predictable than that of POPs. Bottlenose dolphins and harbour porpoises were found to have higher PCBs concentrations than the rest of the analysed NWIP toothed whales, as well as those of adjacent NE Atlantic waters. The main results of this PhD highlight the relevance of exploiting these chemical parameters as ecological tracers, as well as their usefulness in the comprehensive study of structure and function of ecosystems through the role of top predators. Combined with the information on anthropogenic activities, this work can also contribute to the development and implementation of management plans and mitigation measures for these five species of toothed whales in the NWIP.<br>O primeiro objetivo desta tese foi determinar qual grau de segregação ecológica existente entre cinco espécies simpráticas de cetáceos odontocetes (i.e. golfinho-comum Delphinus delphis, bôto Phocoena phocoena, roaz-corvineiro Tursiops truncatus, golfinho-riscado Stenella coeruleoalba e baleia-piloto Globicephala melas) que habitam numa área restrita e altamente produtiva, o Noroeste da Península Ibérica (NOPI). Para este fim, foram analisados parâmetros químicos como um "método alternativo" que pode refletir a dieta e habitat em diferentes períodos de integração destes animais, complementando a informação obtida através de métodos tradicionais tais como as análises de conteúdos estomacais, as análises de fezes e a observação de campo levadas a cabo no NOPI. O segundo objetivo foi avaliar o estado de contaminação destas espécies, obtendo dados de base de contaminantes nestas populações e estimar o risco toxicológico. Os elementos traço, os isótopos estáveis de carbono e nitrogênio e os poluentes orgânicos persistentes (POPs) foram seleccionados como parâmetros químicos para responder aos nossos objectivos. Em primeiro lugar, os parâmetros químicos foram utilizados como traçadores ecológicos de populações (ou partes das populações) pondo em evidência a dieta e habitat das espécies em estudo ao longo de diferentes escalas temporais. Estimou-se que a cadeia trófica possui um total de cinco niveis tróficos onde os cetáceos odontocetes estudados ocupam as posições mais elevadas sem apresentar diferenças significativas entre elas, variando desde 4.3 para 5.3. Embora a análise de um único parâmetro químico não tenha permitido segregar completamente as cinco espécies, a informação obtida combinando as análises de vários traçadores ecológicos a longo prazo (i.e. isótopos estáveis de carbono e nitrogênio em dentes e concentrações de cádmio nos rins) revela uma segregação do nicho ecológico entre as cinco espécies em duas dimensões do nicho (a dimensão trófica e a dimensão espacial). Porém, não pode ser excluída uma sobreposição temporal, uma vez que não foi possível investigar variações sazonais ou interanuais, excepto no caso do golfinho-comum. Adicionalmente, mostramos que perfis de policloro bifenis (PCBs) podem ser un traçador pertinente da ecologia alimentar de espécies taxonomicamente próximas permitindo uma boa separação das espécies bôto e golfinho-riscado de acordo com os seus diferentes padrões. Em segundo lugar, foi avaliado o estado de contaminação das espécies nesta área. As concentrações foram interpretadas tendo em conta factores biológicos e ecológicos. No entanto, a bio-acumulação dos elementos traço mostrou-se menos previsível que a bio-acumulação dos POPs. O roaz-corvineiro e o bôto exibiram as concentrações mais elevadas de PCBs com respeito dos outros cetáceos odontocetes do NOPI e com respeito aos outros indivíduos de águas vizinhas do Oceano Atlântico Nordeste. Os principais resultados desta tese mostram a relevância destes parâmetros químicos como os traçadores ecológicos e a sua utilidade no estudo da estrutura e funcionamento dos ecossistemas através do papel dos predadores de topo. Combinando estes dados com a informação sobre as atividades antropogénicas, este trabalho pode contribuir ao desenvolvimento e implementação de planos de gestão e mitigação para estas cinco espécies de cetáceos odontocetes no NOPI.<br>Le premier objectif de ce travail de thèse était de déterminer quel est le degré de ségrégation écologique entre cinq espèces sympatriques de cétacés odontocètes (i.e. le dauphin commun Delphinus delphis, le marsouin commun Phocoena phocoena, le grand dauphin tursiops truncatus, le dauphin bleu et blanc Stenella coeruleoalba et le globicéphale noir Globicephala melas) fréquentant l’aire marine restreinte et très productive du Nord-Ouest de la Péninsule Ibérique (NOPI). Pour cela, des paramètres chimiques ont été analysés dans les tissus biologiques, en tant que “ méthode alternative ” pouvant refléter de façon précise le régime alimentaire et l’habitat de ces animaux à différents échelles de temps d’intégration, et ainsi compléter les informations apportées par des méthodes plus traditionnelles tels que l’analyse des contenus stomacaux ou des fèces, ou encore les données d’observations en mer. Le second objectif de ce travail était d’évaluer l’état de contamination de ces espèces, pour acquérir une base de données de référence complète les concernant et estimer le risque toxicologique auquel elles peuvent faire face. Dans ce contexte, les éléments traces, les isotopes stables du carbone et de l’azote, et les polluants organiques persistants (POPs) sont les paramètres chimiques qui ont été sélectionnés pour répondre aux objectifs fixés. Dans un premier temps, les paramètres chimiques ont été utilisés comme traceurs écologiques des populations (ou de segments de population), procurant une image du régime alimentaire et de l’habitat des espèces à différentes échelles de temps. Nous avons calculé que le réseau trophique du NOPI avait cinq niveaux trophiques, au sein duquel les espèces étudiées occupaient les plus hautes positions, comprises entre 4,3 à 5,3, et sans qu’il y ait de différence significative de position trophiques entre les espèces. Alors que l’analyse d’un seul paramètre chimique ne permettait pas ségréger les cinq espèces, les informations apportées par l’analyse de plusieurs traceurs de long terme (i.e. rapport des isotopes stables du carbone et de l’azote dans les dents et concentrations de cadmium dans les reins) ont révélé une ségrégation de leur niche écologique dans deux des dimensions possibles (les dimensions trophique et spatiale). Cependant, les variations pouvant survenir d’une année sur l’autre ou saisonnières n’ont pas pu être étudiées, excepté pour le dauphin commun, et un chevauchement temporaire des niches ne peut donc pas être totalement exclu. De plus, nous avons montré que les profils de polychlorobiphényles (PCBs) pouvaient être un traceur pertinent de l’écologie trophique d’espèces taxinomiquement proches, en permettant une séparation fine des espèces telles que le marsouin commun et le dauphin bleu et blanc, d’après les différents profiles d’accumulation de ces deux espèces. Dans un second temps, l’état de contamination des espèces dans la zone d’étude a été évalué. Les concentrations ont été interprétées à la lumière des facteurs biologiques et écologiques pouvant influencer ces concentrations, et la bioaccumulation des éléments traces s’est révélée moins prévisible que celle des POPs. Le grand dauphin et le marsouin commun présentaient les concentrations de PCBs les plus élevées par rapport aux autres cétacés odontocètes du NOPI et par rapport à d’autres individus des eaux adjacentes de l’Atlantique Nord-Est. Les résultats principaux de ce travail de thèse ont mis en évidence la pertinence d’utiliser ces paramètres chimiques comme traceurs écologiques, et leur utilité dans la compréhension de la structure et le fonctionnement des écosystèmes à travers le rôle des prédateurs supérieurs. En combinant ces résultats à des informations concernant les activités anthropiques, ce travail peut contribuer au développement et à l’implémentation de mesures de gestion pour ces cinq espèces de cétacés odontocètes du NOPI.<br>Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/36766/2007