In the last two decades a series of chance discoveries and dedicated research programmes have produced a wealth of data on the post-mortem fate of whale carcasses. Biological taphonomic processes at whale skeletons on the seafloor are driven by chemical energy in the form of abundant lipid reserves in whale skeletons. Previously unrecognised variations in the lipid content of bones from different parts of whale skeletons explained patterns of faunal colonisation and bone degradation. Experimental work to elucidate the mechanisms responsible for these relationships demonstrated that the breakdown of bone lipids retards. microbial digestion of the bones, leading to differential degradation of the skeleton. Furthermore, analysis of total skeletal lipid content shows that when this value is high «1000 kg) skeletons may last for decades on the seabed until degradation or burial leading to a taphonomic bias towards large mature individuals. Another key factor in determining the longevity of whale skeletons on the seafloor is the activity of Osedax tubeworms, which bore into the bones, using them as a source of nutrition. Micro computed-tomography was used to investigate multiple aspects of bone destruction by Osedax. Rates of bone erosion by Osedax mucofloris in experimentally deployed bones varied between 1-6% per year, depending on the density of colonisation. The boring morphology of thirteen Osedax species were quantitatively described and analysed. Most species preferentially utilise the collagen matrix of the bone through the erosion of individual bone trabeculae, indicating that bone structure is largely responsible for the boring morphology. Using this information Osedax borings were described in a fossil whale bone from shelf-depth sediments from the Pliocene of Italy, indicating that by this time Osedax was widespread throughout the world's oceans. Further evidence of Osedax bioerosion in samples from the abyssal Pacific suggests that these worms probably have a worldwide distribution today.

This thesis examines one of the most controversial issues in the modern governance of marine living resources, namely the regulation of cetaceans (whales, dolphins and porpoises). Cetaceans face a wide range of conservation pressures, from targeted catches to incidental mortality in fisheries and the pernicious effects of habitat destruction and disturbance. The voluminous literature on cetacean issues to date has focussed predominantly on the complicated regulatory position of the International Whaling Commission, created under the International Convention for the Regulation of Whaling 1946, although supervisory institutions pertinent to cetaceans have steadily proliferated since the mid-1970s. This thesis reviews the leading regulatory actors and institutions, with particular reference to the cohesion of the overall framework and its ability to develop effective synergies and to advance meaningful conservation measures for cetaceans. In so doing, the role of the IWC is analysed to provide a basis to identify the degree of regulatory supplementation required by alternative fora. To this end, this thesis further analyses the role of the Convention on International Trade in Endangered Species of Wild Flora and Fauna 1973, the Convention on Biological Diversity 1992 and the UN Convention on the Law of the Sea 1982, before conducting a sustained appraisal of obligations under the Convention on the Conservation of Migratory Species of Wild Animals 1979 in respect of small cetaceans. This thesis also advances a first substantive examination of pertinent policies of the European Union, and evaluates the role of EU law in the conservation of cetaceans on the international, regional and national levels.

Tooth microwear occurs when an animal processes food, producing microscopic pits and scratches on tooth surfaces, providing evidence of tooth movements and food properties. 3D microwear analysis is a growing field of study, where sub-micron scale tooth surface textures are used to compare populations with dietary differences. It has been primarily employed to study terrestrial vertebrates, however, the technique has rarely been applied to aquatic vertebrates, and never to aquatic mammals. Furthermore, the technique suffers from methodological variability. To address these points this thesis presents the results of five studies using 3D microwear analysis, three of which investigate different aspects of methodological variability, and two investigate the utility of 3D microwear analysis to differentiate diet in marine mammals, both across multiple species, and within a single species. An investigation of seven commonly used moulding compounds of varying viscosity demonstrated that mid-viscosity President Jet Regular Body produced the most accurate and precise moulds of tooth surface texture. An investigation was also carried out to test the effect of scale limiting 3D surfaces using 40 different combinations of operator (Nth order of polynomial) and filter to produce roughness surfaces. It was shown that high variability exists between resulting surfaces depending on the operator and the filter used. A combination of 6th order of polynomial, robust Gaussian filter and 0.025mm nesting index produced the greatest separation of known dietary groups while also being comparable to surfaces generated using many other combinations. An investigation into the effect of using four different microscopes to collect 3D tooth surface texture data showed high variability between resulting roughness parameter values and sensitivity to dietary differences depending on the microscope used. When testing the ability of 3D microwear analysis to separate ten marine mammal species into four known dietary groups, it was shown that this technique is highly sensitive to dietary differences, and provides information about the dietary evolution of extinct cetaceans. Finally, when using dentin tooth surfaces to test the ability of 3D microwear to detect differences between Orcinus orca dietary populations, it was found that their surface texture appears highly variable, and that little separation was possible between dietary groups.

Freshwater cetaceans are one of the most threatened groups of mammals on earth. Limited resources for monitoring and low power to detect trends hinder the development of effective conservation. Using the southern Bangladesh subpopulation of Ganges River dolphins (Platanista gangetica gangetica), previously thought to be a closed population, I investigate cost-effective boat-based methods for monitoring and estimating population size, and the value of local informant data for contributing to knowledge on the status of this poorly-known subpopulation. Detectability must be accounted for during surveys to make inferences on species’ trends. However, many surveys use methods that do not account for detectability, assuming such approaches to be cheaper. I demonstrate that a combined visual-acoustic survey is a robust and cost-effective approach for monitoring. Using data from multiple seasons and marine surveys, I show the population may not be closed. I develop correction factors to account for imperfect detectability during past visual-only surveys and use these to show there is no detectable long-term (1999-2012) change in the abundance of this subpopulation. Local informant data are sometimes considered to have the potential to provide information of value to monitoring population trends. A comparison of the long-term and seasonal trends from boat-based surveys and those reported by fishers showed poor agreement. Memory-related biases are likely to have impacted informant recall. However, local informant data proved useful in identifying causal mechanisms underlying dolphin susceptibility to bycatch in gillnets, in particular river depth and net mesh size. Furthermore, local informant data provided a minimum estimate of annual mortality that is deemed unsustainable, but is based on a number of assumptions and potential biases that are discussed. Combined visual-acoustic surveys and local informant data represent cost-effective tools for addressing some of the significant knowledge gaps on freshwater cetacean status, aiding the development of evidence-based conservation strategies.

No description available.

Cetaceans are highly mobile mammals, but many species still exhibit degrees of population structure while inhabiting seemingly boundary-free open waters. Resource specialisation is hypothesized as one of the main drivers of population structure. Using multiple diploid and haploid genetic markers, this study reveals, for the first time, the population genetic structure of Risso’s dolphins, Fraser’s dolphins and common bottlenose dolphins in the tropical-temperate regions of the western North Pacific Ocean. For the Risso’s dolphins, the results showed that there are at least three populations in the North Pacific Ocean, by-and-large parallel to the existing biogeographic provinces; and the direction of gene flow corresponds with the direction of the mainstream currents. Mitochondrial DNA (mtDNA) data showed that the Pacific populations are genetically different from the three populations in the eastern North Atlantic Ocean and the Mediterranean Sea. For the Fraser’s dolphins, the genetic differentiation between Japanese and Philippine waters is consistent with the differentiation suggested in an earlier skull morphometric study. For the common bottlenose dolphins, the results suggested that there are at least four populations in the western and central North Pacific Ocean, and the differentiation appears to correspond to habitat types, resembling the scenario of inshore-offshore differentiation seen in other populations of the same species in other regions. The analysis also confirmed that there is no evident gene flow between the two “sister species”, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin (T. aduncus), occurring sympatrically in the region. The mtDNA data suggested that the Risso’s and Fraser’s dolphin populations in the western North Pacific experienced an episode of expansion in the last 10,000 years. Genetic diversity is high in most of the population examined in this study; however, a relatively low effective population size is found in some populations and that may require further conservation attention.

No description available.

Lack of knowledge regarding beaked whale biology restricts our ability to evaluate their vulnerability to anthropogenic threats. This work addresses critical data gaps in Blainville's beaked whale social structure and communication systems. Social analysis shows that Blainville's beaked whales in the Bahamas exhibit group living through a harem structure characterised by a single male accompanying a group of females for up to a year. This study also reveals that females preferentially associate with conspecifics in the same reproductive state, remaining together for up to three years. I show what may be the first example of social philopatry in beaked whales, with adult males possibly providing protection for kin. Analysis of data from acoustic tags reveals previously undescribed sexually distinctive vocalisations. These sounds might serve a communicative function helping to form and maintain groups. Acoustic data also reveals a distinctive double click pattern in Blainville's beaked whales that is likely physiological in nature. The same pattern is also shown in two other deep diving species, Cuvier's beaked whales and sperm whales. Species differences in the frequency of production of these double clicks may be providing a window into the evolution of odontocete echolocation. Data from a bottom-mounted hydrophone array reveals a lack of sex and / or age specific information in this species' echolocation clicks. Analysis of mother-calf pairs indicate calves from at least three months of age echolocate using clicks similar to those of adults. This work provides the first comprehensive study of possible communicative sounds in an elusive deep-diving cetacean species exhibiting a complex social structure that lies somewhere between stable groups and fission-fusion societies. Understanding the interaction between communication and social organisation enhances our ability to predict the effects of anthropogenic disturbance on this species.

Since 2000, there has been a marked decline in the number of harbour seals in some regions around Britain; one possible contributing cause is competition for prey with sympatric grey seals. To explore one important aspect of this interaction, in this thesis the diet of harbour seals is estimated using analysis of hard prey remains recovered from faeces and compared with equivalent results for grey seals. To estimate coefficients to account for partial and complete digestion of hard prey remains, 100 whole prey feeding trials were conducted with six harbour seals and 18 prey species. Differences were found among prey species and between harbour and grey seals highlighting the importance of applying predator- and prey-specific digestion correction factors when reconstructing diet. In a comprehensive exploration of the diet of harbour seals around Britain, sandeel and flatfish dominated in the North Sea and large gadoids dominated on the Scottish west coast with seasonal pulses of pelagic prey. Variation in diet was linked to regional and seasonal differences in prey distribution and abundance. Sex-specific variation in harbour seal diet was examined in four regions. The main difference detected was in The Wash, where female diet quality was significantly higher than males in winter, which appeared to be driven by greater consumption of pelagic prey by female seals associated with seasonal energetic requirements of their annual life cycle. Comparison of the diet of harbour and grey seals revealed regional differences in diet composition, diversity and quality between the two species. However, there was no consistent pattern in this variation in relation to regional variation in harbour and grey seals population trajectories and no clear evidence for interspecific competition for prey. Future work should focus on an integrated investigation of prey abundance and distribution, and seal diet and foraging behaviour/distribution.

Mid-latitude shelf-seas are highly productive regions that host a rich diversity of animals including large numbers of marine mammals and seabirds. These large vertebrate predators play a crucial role in the functioning of shelf-sea ecosystems. However, the combined effects of multiple anthropogenic stressors are driving unprecedented declines in many of their populations. Mitigating this depends upon effective conservation and integrated ecosystem based approaches to management, which require a comprehensive understanding of the habitat needs of marine predators. The foraging efficiencies of marine predators are closely tied to the availability of a number of oceanographic features. As such, these physical habitats represent critical locations within a species’ range whose preservation and protection should be of high priority. The collection of studies presented in this thesis aims to improve our understanding of the physical oceanographic processes that underlie the at-sea behaviours and distributions of marine mammals and seabirds in coastal and shelf-sea environments. A combination of at-sea boat surveying, animal-borne biologging, satellite remote-sensing, passive acoustics and numerical modelling was used to collect information on the distributions and foraging behaviours of a range of marine predators alongside the bio-physical characteristics of the oceanographic habitats they occupied. These data were then used to (1) examine the use of oceanographic habitats generated around tidal-mixing fronts and coastal topographic structures by a range of piscivorous species including bottlenose dolphins Tursiops truncatus, common dolphins Delphinus delphis, harbour porpoises Phocoena phocoena and northern gannets Morus bassanus, and (2) identify the physical processes underlying their creation. Original aspects of this work include the examination of the fine-scale bio-physical mechanisms that link marine predators to tidal-mixing fronts and coastal tidal-topographic structures. Main findings indicate that offshore habitats around tidal-mixing fronts are used by both common dolphins and northern gannets for foraging. Individuals associated with patches of increased sub-surface primary productivity, which were generated via a bi-weekly cycle of episodic turbulent mixing and stratification following an adjustment in the spatial position of a front with the spring-neap cycle. Moreover, around fronts, the dives of gannets were likely to be short and of a V-shaped strategy (with little active swim phase), which likely reflects an increase in the accessibility and catchability of their prey. In a coastal estuarine system, bottlenose dolphins were shown to associate with predictable downwelling features generated during flood tidal flows that were thought to act as a foraging aid. Together, these findings highlight the fundamental role physical oceanographic processes play in the structuring of marine ecosystems by providing vulnerable marine predators with prosperous and reliable foraging resources that they can exploit. This work has implications for both future studies of marine predator foraging ecology and the management of anthropogenic activities in coastal and shelf-seas.