The bottlenose dolphin uses vocal learning to develop its own unique acoustic signal. This signal encodes the identity of the signaller, and is known as the animal's signature whistle. The dolphin's ability for vocal learning means that the signature whistle of one animal may be found in the vocal repertoire of other animals. This copying of signature whistle types may allow conspecifics to label or address one another. This thesis investigated the use of signature whistle copying in both captive and wild animals. Dolphins have been known to rapidly imitate each other's signature whistle in vocal matching exchanges. This matching of sounds has an aggressive connotation in songbirds, yet the function in bottlenose dolphins remains unclear. I have shown, through playback experiments with captive animals, that signature whistle matching in dolphins is not aggressive but appears to be affiliative, and may be used as a tool to initiate contact with the signature whistle owner. In addition, the rapid matching of whistle types in wild dolphins appears to play a specific role in their foraging behaviour, indicating the function of vocal matching may indeed be multi-faceted. This thesis also uses a unique dataset to extensively describe the occurrence of signature whistle copying in wild animals. The imitation of individual signature whistles occurred almost exclusively between close associates during separations. All copies were accurate representations of the original signature whistle, but were clearly recognisable due to fine-scale differences in selected acoustic parameters, and are therefore unlikely to be used deceptively. Finally, I provide evidence that wild bottlenose dolphins respond to hearing a copy of their own signature whistle by calling back. This offers support to the notion that signature whistles function as distinctive labels that are used to address individuals, and perhaps even label them referentially.

The aim of this research was to apply genetic methods to a better understanding of the evolution of population genetic structure in two dolphin species inhabiting a shared geographic range in the Mediterranean Sea and eastern North Atlantic (ENA). In support of this I analysed the pattern of population subdivision, genetic variability and group kin structure of striped (Stenella coeruleoalba) and Risso's dolphins (Grampus griseus) in the Mediterranean Sea, and compare theassessed the level of genetic differentiation between Mediterranean and ENA populations. The specific objectives were to: 1- study their distribution in the core study area (the Ligurian Sea) and group size variation as a possible behavioural responses to environmental features; 2- assess patterns of kinship and association within and between social groups (based on estimates of R); and 3- investigate patterns of genetic subdivision among the putative striped and Risso's dolphin populations within the Mediterranean Sea, and in comparison with the ENA. Risso's dolphins showed a clear preference for the steeper continental slope, while striped dolphins did not show this distribution preference. Samples from 165 striped dolphins were collected from the Mediterranean Sea (Adriatic, Tyrrhenian, and Spam) and ENA, and were analysed at 8 microsatellite DNA loci. The comparison between the Mediterranean and the ENA populations showed a clear separation (Fst=0.055). All loci were polymorphic (4-22 alleles), and mean Ho ranged from 0.68 in the Tyrrhenian to 0.8 in the ENA. All comparisons between putative populations showed significant differentiation, including the populations of the eastern (Adriatic) and western (Tyrrhenian) seas of Italy. Analysis of the Risso's dolphin samples (n=50) collected in the Mediterranean and the ENA showed that the two populations were significantly differentiated (Fst=0.0296). All loci were polymorphic (up to 17 alleles), and mean Ho was 0.467 m the Mediterranean, 0.548 in the ENA. Analysis of 619 bp of sequence of the mtDNA control region revealed 28 variable sites defining 16 unique haplotypes among the two populations. The degree of differentiation was highly significant for both FST (0.260) and ɸST (0.542).Individual relatedness within and between social groups of striped dolphins was investigated m the Ligurian population. On average the values were higher for intra- than inter-group comparisons, and females showed significantly higher relatedness within than between groups. The kin structure of the Risso's dolphins in the Ligurian population showed that females had a considerably higher relatedness within groups than among groups. For both species, the data suggest a relatively fluid model of kin structure with a trend for female philopatry, and male dispersal. My results indicate fine-scale population structure in both species, and significant differentiation between the Mediterranean and North Atlantic populations. A hierarchical pattern of kin structure is clearly influenced by social group structure and the dispersal behaviour of males and females, though there are some differences between the species, probably related to differences in social structure and habitat use.

The primary function of this research project has been to investigate the physical properties of the lower jaw of the Atlantic Bottlenose Dolphin (Tursiops truneatus). This has been achieved through numerical modelling techniques, established physical measurements and modem Laser Doppler Velocity Measurements. During the course of this work some interesting characteristics of the dolphin jaw structure have been discovered. Sound speeds and attenuation levels of the jawbone have been determined and the implications assessed. The geometric array formed by the dolphin teeth of the lower jaw can be used to form an end-fire array which produces a beam pattern similar to those of the dolphin. The geometric array has also been analysed for its passive acoustical properties, in particular its ability to form acoustic stop bands within the audible range of the dolphin. The results of this research show that the directivity of the dolphin can be reproduced using the morphological features of the lower jaw.

The relationship between developmental stability, genomic diversity and environmental stress in three eastern North Atlantic populations of the harbour porpoise {Phocoena phocoena), and in two populations of the western North Atlantic and one from the Gulf of California of the bottlenose dolphin {Tursiops truncatus) was investigated. In addition, the population structure for the two species from the study areas mentioned was also assessed. Population structure was determined using discriminant function analysis for morphological characters and a Bayesian analysis for microsatellite loci. Consistency of the results was assessed with pairwise comparisons between populations using two indices of population differentiation (F(_st) and Rho(_st)). For the harbour porpoises classification was made into three putative populations: Norwegian, British and Danish. For the bottlenose dolphin significant differentiation was found for the three populations studied. Population differentiation between the two western North Atlantic parapatric populations was the highest among the pairwise comparisons. This result highlights the importance of resource specialisation of bottlenose dolphins in causing population structure for parapatric populations. Developmental stability was assessed by fluctuating asymmetry (FA) measured on morphological traits. Genomic diversity was determined by five indices (mean cf, scaled mean cF, multilocus individual heterozygosity, standardised heterozygosity and internal relatedness). Environmental stress was assessed by the concentration of chemical pollutants in tissues, and from the literature published for chemical pollutants, by-catch rate, parasite load and mean surface ocean temperature. Significant relationships between FA and the indices of genomic diversity were found. The Norwegian population of harbour porpoises and the coastal population of the western North Atlantic of bottlenose dolphin showed the highest level of FA. Both populations also showed the least genetically diverse animals. However, no clarity was obtained in respect of the relationship between FA and environmental stress. British and Norwegian harbour porpoises did not show significant correlations between the concentration of several chemical pollutants in tissues and FA. In addition, the Norwegian population of harbour porpoise inhabits the least impacted areas in respect to the concentration of chemical pollutants in tissues, parasite load and by-catch rates. Environmental stress was difficult to assess on the bottlenose dolphins populations due to the scarcity of data. These results show the influence of genetic diversity on the disruption of developmental stability and they also show the importance of conservation practices in maintaining genetic diversity as an important factor for the subsistence of natural populations.

Echolocation is the primary tool dolphins depend on for their survival underwater. Without this ability, the localization of food and navigation would be much harder for the animals. This active sonar is characterised by narrow transmission and reception directivity patterns, over a variety of ranges. In Cetaceans, only toothed whales and dolphins (odontocetes) are able to echolocate. The main concept for echolocation is to emit sound and listen to the returning echoes. Where sound enters the head first and how the signals are transmitted to the mandibular fats and inner ears is not fully understood. There are several theories on how sound reaches the fatty tissues in the lower jaw: through a thin region in the lower jaw called the pan bone, through the throat region and an opening in the rear mandibles and through the teeth, acting as an end-fire array and enhancing the directional hearing. The hypothesis on sound reception via the teeth was investigated further in this thesis. The sound pressure was modelled at the teeth of a bottlenose dolphin (Tursiops truncatus) using acoustic characteristics of different components of the entire jaw. The angle of the jaw was changed from 0° to ±10° in 1 degree steps and from ±10° to ±90° in 5 degree steps. The pressure was measured at 3 front and back teeth and the difference between pressure values compared. The pressure was also measured at each of the 22 teeth on both sides of the jaw for two different angles, 0° and +5°. Multiple scattering and the influence from the relative positions and sizes of teeth as well as the effect of missing teeth was investigated. Results show that the propagation of sound varies with size and position of the teeth. The simulations display the relation between neighbouring teeth and the attenuation or amplification of the signals at other teeth. Teeth cannot be considered as individual point-like receivers. A pressure tendency can be seen at the back teeth for the first ±15°, which indicates that directional hearing occurs for the first degrees the dolphin moves its head. It also shows that hearing takes place primarily at the back of the jaw.

The ecology of Pacific white-sided dolphins (Lagenorhynchus obliquidens) in the Broughton Archipelago, British Columbia (BC), Canada was explored through photo-identification, mark- recapture, acoustics, and sociality studies. New population parameters were estimated from photo-ID data for the first time in this species. Abundance was highly variable, ranging from 546 (95% CI: 293-1,018) to 2,889 (95% CI: 1,424-5,863), after accounting for the proportion (0.57; 95% CI: 0.55 - 0.60) of marked dolphins. A “match uncertainty” analysis showed that less strict matching criteria caused negative bias in abundance estimates and an apparent improvement in precision. Estimates of survival rate ranged from 0.907 (SE=0.03) to 0.989 (SE= 0.066). Robust design analyses revealed random temporary emigration movement at 0.14 (SE=0.318) annually and no movement seasonally. The study revealed new evidence for philopatry and sociality: some individuals were resighted over 19-year periods, and associated pairs more than a decade apart. Evidence was found for a high degree of sociality. The mean proportion of calves was estimated as 0.0597 (SE=0.0083, 95% CI: 0.045-0.079) per capita, translating to an average probability of pregnancy in adult females of 0.238 (95% CI: 0.180- 0.316) and an average interbirth interval of 4.2 years. Approximately 3.9% of dolphins bore injuries from killer whales, but only 0.5% showed evidence of interactions with fishing gear or propellers. Acoustic evidence for population structure was equivocal, but warrants additional, targeted research. Population viability analysis predicted an average rate of annual decline of - 0.122 (95% CI: -0.143 to -0.101), given a range of input values in a sensitivity test, over the next 50 years.

In the marine environment, where barriers to dispersal are limited, taxa normally exhibit genetic homogeneity across large spatial scales. Extraordinarily, marine mammals regularly exhibit genetic differentiation within their cruising range. Furthermore, recent radiation in Delphininae has resulted in several closely related species that remain taxonomically unresolved, particularly bottlenose dolphins (BND) Tursiops spp. and common dolphins (CD) Delphinus spp., making these taxa interesting for studying evolutionary processes. Using mitogenomes and a multi-locus dataset, BNDs from the northwest Indian Ocean (IO) were compared with other recognized species/ecotypes around the world. A new (third) lineage of Indo-Pacific BND, T. aduncus, was identified from the region. Reconstructions of ancestral biogeography and divergence date estimates, suggest a divergence mechanism within T. aduncus that coincides with climate change over the Pleistocene. Reconstructions of ancestral morphology suggest a coastal ancestry for BNDs. Significant population structure was exhibited between T. aduncus populations in the western IO based on mtDNA control region sequences and 14 microsatellite loci. Genetic subdivision appears to correlate with habitat heterogeneity across the study area, which may be driving differentiation through local adaption. Traditional and geometric morphometric techniques were used to investigate congruency between genetic and phenotypic differentiation of three BND lineages in the northwest IO. Strong differences were exhibited in morphology between common BNDs, T. truncatus, and T. aduncus. The T. aduncus lineages were similar, however significant differences in morphology were evident. Significant genetic structure was evident between CD populations off Portugal, South Africa and Oman, based on mtDNA sequences and 14 microsatellites. Further analyses support the taxonomic designation of D. capensis tropicalis in the northwest IO. Both genera exhibit significant population structure over spatial scales outdistanced by their dispersal abilities. Contemporary and historic environmental heterogeneity are suggested as drivers for this structure. Further evidence is provided for the northwest/northern IO as a region of evolutionary endemism, which will inform regional conservation initiatives.

The population of bottlenose dolphins off the east coast of Scotland has been studied since the late 1980s, initially focused on the inner Moray Firth, where a Special Area of Conservation (SAC) was designated under the EU Habitats Directive. The population has since expanded its distributional range and currently ranges from the Moray Firth to the Firth of Forth. The main aims of this thesis were: (1) to estimate population parameters for this population using a 25 year individual recognition dataset, and (2) to increase knowledge of the distribution and abundance of dolphins in areas outside the SAC, especially to investigate areas of high use in St Andrews Bay. Apparent survival rate for adults and sub–adult dolphins was estimated at 0.946 (SE=0.005) accounting for temporary emigration caused by the population's range expansion. Sex-specific survival was estimated for males (0.951, SE=0.013) and females (0.956, SE=0.011) using multistate models to minimize bias caused by individuals of unknown sex. Using a newly developed approach, fecundity rate was estimated at 0.222 (95% CI=0.218-0.253) from an expected mean inter-birth interval of 4.49 yrs (95% CI=3.94-4.93). Total population size was estimated as ~200 individuals, after accounting for temporary emigration and for heterogeneity in capture probabilities. In St Andrews Bay, an area used regularly in summer by approximately half the estimated population, habitat use modelling identified the entrance to the Firth of Tay and waters around Montrose as high use areas for dolphins, whose presence was influenced by tidal current speed and direction. The results suggest that the conservation and management plan for this small and isolated population of bottlenose dolphins should be reviewed to adapt it to current knowledge, especially regarding the uncertainty around the potential impacts of offshore renewable energy developments off the east coast of Scotland.

The coastal waters off western Scotland are inhabited by two small under-studied common bottlenose dolphin (Tursiops truncatus) communities: the Inner Hebrides and the Sound of Barra (SoB) community. The region is considered for future developments for the marine renewables industry, which have the potential to negatively impact these communities; however the assessment of impacts and the development of plans to minimise these are currently hampered by a lack of knowledge about the dolphin's distribution and residency patterns, and spatial and temporal mobility. Using a variety of research methods (dedicated cetacean surveys and targeted photo-ID trips, acoustic monitoring and the collection of opportunistic photo-ID and sightings data from the general public) the current study examined local dolphin spatial and temporal mobility patterns by investigation of their spatial distribution and temporal occurrence. Collectively, the results revealed the presence of two socially and geographically separated (at least 2006-2013) resident communities which both demonstrated year-round presence and long-term site-fidelity, but maintained different ranging patterns. Long-term presence of individuals from the Inner Hebrides community dated back to 2001 and dolphins from this community ranged widely in nearshore waters throughout the entire currently known communal range, and practically used the entire range throughout the year. The SoB community, on the other hand, appeared to have a more restricted distribution, and appeared female-dominated. Summer censuses of the SoB community revealed annual estimates of ≤15 dolphins, with four individuals first identified in 1995, and at least eight calves born since 2005. Acoustic presence of dolphins in the SoB varied through the year, and in relation to the tidal and diel cycles. This study demonstrated that the integration of complementary methodological approaches is useful in investigating mobility patterns of low-density populations, and given the indications for social and spatial isolation, these communities should be managed independently.

The main aim of this work was to determine the past, present and future conservation status of the bottlenose dolphin population inhabiting the Sado estuary region, Portugal, using a long term (photo ID) data set. Resident animals, identified from their strong resighting pattern, were confined to the estuary region. There is little evidence of social interchange with other coastal bottlenose dolphins and the role of emigration and immigration is unclear. This is a very small population. Numbers of animals have decreased in the past but now seem to be increasing. A mark-recapture analysis of individual capture histories showed that time changes in age-specific survival explained the observed changes in number of animals. Survival was lower, particularly in young animals, in earlier years which have resulted in a long period of lack of recruitment to adulthood. In the most recent years survival has increased, especially for calves in their second and third years. Fecundity has also been higher. Protected areas and proposed marine SACs reflect the importance of the Sado estuary region; this is also an area of intense anthropogenic activities that threaten the dolphin population. Population viability analysis was conducted using the software VORTEX incorporating estimates of past or current vital rates. The likely future of the resident population is for it to decline, especially during the next few decades. A viable population was only predicted if maximum values of vital rates were used or if regular immigration occurred. A number of proposals for management action are discussed. This work constitutes an example in conservation biology where life history parameters were estimated, and used to predict future viability and thus to indicate management actions that could increase the chance of saving a very small marine mammal population.