京都大学 / 新制・課程博士 / 博士(農学) / 甲第24298号 / 農博第2527号 / 新制||農||1095(附属図書館) / 学位論文||R4||N5421(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 三田村 啓理, 教授 益田 玲爾, 准教授 市川 光太郎 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Two sympatric dolphin species, Stenella frontalis and Tursiops truncatus, resident to Little Bahama Bank, Bahamas were found to mostly forage independent of one another, but occasionally foraged in mixed groups. Analysis of over 20 years of data revealed the degree of overlap to be minimal with spatially distinct regions identified for both species, environmental segregation based on depth, bottom type, temperature, and time of day. Results based on observational data indicated significant differences in group size and selected prey. For S. frontalis, lactating females had the most distinct diet, which differed from that of non-reproductively active (NRA) females. Pregnant females had ambiguous prey use results, but diet differences were revealed through nutritional analysis. Lactating females had a higher intake of all nutrients (% moisture, % lipid, % protein, and calories) than pregnant females but lower than NRA females. Mother and calf pairs selected prey for caloric and moisture values. The influence of calves on foraging groups was reflected through discrete differences in all nutrients. Males and females appeared to select the same major prey, but female prey use was much more diverse. / by Christopher R. Malinowski. / Thesis (M.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

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 Bottlenose dolphins superseded human values of the neocortex ratio and common dolphins marked the upper limit of the range for the dolphin species under investigation.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. / Thesis (M.A.)-University of Natal, Durban, 1996.

Populations of the humpback dolphin in Natal, South Africa, are subject to increasing pressures including capture in the shark nets and habitat degradation, and concern has been raised about the status of the population. A minimum of 95 humpback dolphins were caught in the shark nets during the period from 1980 to 1992. Capture and sighting records of the Natal Sharks Board revealed a relatively high occurrence of humpback dolphins at Richards Bay. Elsewhere, in southern Natal, the infrequent sightings and captures were attributed to a seasonal occurrence of dolphins, possibly due to temporary movements away from resident areas. Sighting rates reported by the Natal Sharks Board has decreased by 55%from 1984-86 to 1990-92 and may reflect a decrease in the population. In a photo-identification study, searches took place in ten search areas in Natal. The sighting rates in the different areas revealed a relatively high density of humpback dolphins occurring in north central Natal, from the Tugela River to the St. Lucia estuary (including Richards Bay). This distribution correlated significantly with the turbidity of the water and the width of the inshore continental shelf, and was inversely related to the density of bottlenose dolphins. Within the northern Tugela Bank region, higher densities of dolphins were found surrounding the five river mouths and estuaries. The Natal population was estimated to be between 161 to 166 animals (95% confidence limits 134 to 229). The annual mortality due to shark net captures approximates 4,5%of the population. Various evidence, including a high mortality rate and a decrease in the annual sighting per unit effort reported by the Natal Sharks Board suggest that the humpback dolphin population in Natal is vulnerable and may be decreasing in size. A proposal is made to reduce the capture rate by relocating shark nets away from the Richards Bay harbour. / Thesis (M.Sc.)-University of Natal, 1994.

Knowledge about cetaceans in the Red Sea is limited with only a handful of sporadic or spatially-limited studies carried out to date. Funded by the Italian Cooperation through a Debt-for-Nature Swap programme and carried out in collaboration with the Egyptian NGO HEPCA, this thesis presents the results from the first ever systematic vessel-based surveys conducted in the southern Egyptian Red Sea from 2010 to 2013 using linetransect methodology. The main aims of the thesis were (a) to estimate cetacean abundance, (b) to determine distribution patterns and habitat use of the cetacean species, (c) to investigate movement patterns for species for which individual recognition techniques were suitable and (d) to identify areas of conservation concern for cetaceans with a particular focus on existing protected areas. Eight species were identified, of which five were commonly encountered (Stenella longirostris, S. attenuata, Tursiops truncatus, T. aduncus, and Grampus griseus) and three were rare (Pseudorca crassidens, Sousa plumbea, Balaenoptera edeni). Estimates of abundance using design-based line transect sampling techniques were obtained for five species: S. attenuata 10,268 (CV=0.26); S. longirostris 6,961 (CV=0.26); T. aduncus 659 (CV=0.69); T. truncatus 509 (CV=0.33), and G. griseus 367 (CV=0.37). Habitat modelling revealed that the two Stenella species were widely distributed across the study area. In contrast, T. truncatus was concentrated in waters around Ras Banas peninsula (in particular Satayah offshore reef), and T. aduncus was mainly found along the coast with possibly separate sub-populations in the northern and southern study area. G. griseus was only encountered in the southern part. The information provided in this study will allow the development of a conservation strategy for the protected areas and will serve as baseline information to carry out future survey work in the Red Sea.

Demographic changes, through immigration/emigration (or death) can affect the social and community structure of a population. This study reports on the effects of demographic changes following 2 intense hurricanes on two sympatric delphinid species: Atlantic bottlenose dolphins, Tursiops truncatus, and Atlantic spotted dolphins Stenella frontalis. Thirty percent of the bottlenose population was lost after the hurricanes, with an influx of roughly the same number of immigrants. The stable community split into two cohesive units. Preferences in association in relation to reproductive status and sex remained. Immigrants assimilated well into the population, especially males. There is a conflict of interest between resident males and females in accepting immigrants and often females find more resistance than males. Long-term analysis of spotted dolphins revealed a community structure defined by long-term site fidelity, natal philopatry of both sexes and three social clusters. / Female associations were influenced by reproductive status and social familiarity within clusters. Males formed long-term alliances and shorter-term coalitions. Some movement between clusters occurred. Alliance formation crystallized in adulthood. Mating strategies and sex were the primary factors shaping social structure. Thirty-six percent of the spotted dolphin population was lost after the hurricanes with no influx of immigrants. The spotted dolphin community differed little from long-term analysis, including definitive social clusters and sex preferences. Social cohesion increased within units and across age classes. Some juveniles had associations of alliance level. Loss of individuals resulted in subtle changes in social structure. Interspecies associations reveal striking differences in association patterns between species. Group sizes and re-sightings of spotted dolphins were larger than for bottlenose dolphins, particularly for aggressive encounters. / Male alliances and coalitions were prevalent for spotted dolphins, but not for bottlenose dolphins. After the hurricanes lower re-sighting and group sizes for spotted dolphin males and less aggressive behavior documented, indicates a re-structuring period of relationships between the species. This study shows that environmental variations may alter the structure of mammal societies through demographic upheaval and survival of populations may depend on their social structure and the social adaptability of the species. / by Cindy Rogers Elliser. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

The Major Histocompatibility Complex (MHC) encodes proteins critical to the vertebrate immune response; therefore MHC diversity is an indicator of population health. I have (1) Isolated exon 2 of the class II gene DQA in Tursiops truncatus in the North Indian River Lagoon (IRL) (n=17), South IRL (n=29) and adjacent Atlantic waters (n=20), (2) assessed genetic variability between groups, (3) developed a method to genotype individuals, (4) typed 11 unique alleles in 66 individuals, (5) detected geographic patterns of diversity between estuarine and coastal individuals (FST=0.1255, p<0.05), (6) found evidence of positive selection centered in the binding pockets P1, P6 and P9 of the peptide binding region (w=2.08), (7) found that patterns of polymorphism did not closely match patterns of diversity in neutral markers, (8) performed a pilot study with Orcinus orca. The initial findings highlight the need for further comparative work and suggest that silent mutations are not neutral. / by Tatiana Ferrer. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Wavelets have been used in numerous geophysical studies but few have examined their applicability to underwater acoustic signals. Wavelet transforms can remove noise from a given time series and allow data analysis at multiple levels of resolution. This unique ability is exercised as a feasible application to the signals in this thesis: a reflected scattered signal from a swimbladder-bearing fish, alewife (Alosa pseudoharengus), and several Odontocetes vocalizations. Both studies reveal that wavelet-based techniques show potential in providing viable information for these acoustic signals despite the lack of statistical analysis. The alewife portion shows a reasonable first order approximation to the absolute target strength and to the time delay correlation caused by the spatial separation of scattering features in the fish. The marine mammal application shows a possible real time method to estimate the mammal's range using the root mean square (RMS) energy of the decomposed signal. Because of wavelet function mismatch, both studies conclude that more extensive research is necessary to develop these techniques into systematic processes.

Duas espécies de cetáceos apresentam padrões de distribuição peculiares ao longo da costa brasileira, muito provavelmente em resposta às condições hidrográficas e topográficas que ocorrem entre 20 e 33°S. A primeira espécie, a franciscana ou toninha (Pontoporia blainvillei), é um golfinho de distribuição restrita do Brasil até a Argentina, que ocorre primariamente na plataforma continental interna, raramente ultrapassando os 50 m de profundidade. Já a segunda espécie, o golfinho-pintado-do-Atlântico (Stenella frontalis), é um golfinho de distribuição restrita ao Oceano Atlântico, que ocupa principalmente a plataforma continental. Estas duas espécies apresentam hiatos ao longo da sua distribuição no Brasil que tem consequências na morfologia e estrutura genética das espécies. Através da aplicação de diferentes métodos, o principal objetivo deste estudo foi investigar a influência do ambiente marinho no padrão de distribuição e na estrutura genética destas duas espécies com ênfase na costa brasileira. No primeiro capítulo, investigou-se a relação do ambiente marinho com o padrão de distribuição da franciscana. Para tanto, uma revisão e atualização da distribuição das áreas de manejo da franciscana (FMA), e dos limites dos hiatos, ao longo do Brasil foram realizadas. Análises de nicho ecológico sugerem que os hiatos fazem parte do nicho fundamental da franciscana que seriam, portanto, relativamente adequados para a espécie.No entanto, o estreitamento da plataforma continental parece ser o principal fator que explica a ausência da espécie nos hiatos e, inclusive poderia explicar a diferenciação genética entre algumas FMAs No segundo e terceiro capítulos, a relação entre similaridade genética e distâncias geográficas e ambientais foram investigadas para o golfinho-pintado-do- Atlântico em duas escalas: ao longo de praticamente toda distribuição e em uma escala mais restrita com ênfase no Brasil. Populações geneticamente distintas ao longo de toda distribuição da espécie foram identificadas com base em um marcador mitocondrial, que podem ser resultado Isolamento por Distância e Isolamento por Resistência, relacionados tanto com condições ambientais contemporâneas quanto do passado (Último Glacial Máximo). As análises de estrutura populacional do golfinho-pintado-do-Atlântico no Brasil, investigada mais profundamente com marcadores genômicos, indicam ao menos a existência de três populações (Brasil, Colômbia e Oceânica) suportanto, portanto, a hipótese de uma população isolada no sudeste do Brasil. De forma geral, conclui-se que o ambiente marinho e, principalmente, fatores como extensão da plataforma continental, batimetria e temperatura tem um papel fundamental para explicar o padrão de distribuição destas espécies no Brasil. Além disso, outros processos podem estar envolvidos na estruturação genética do golfinho-pintado-do-Atlântico e também da franciscana como, por exemplo, estrutura social, filopatria e a história evolutiva destas espécies. O maior desafio para conservação da franciscana é seu status de Criticamente Ameaçada no Brasil e, em relação ao golfinho-pintado-do-Atlântico é a deficiência de dados. Uma vez que ambas espécies ocorrem na porção mais desenvolvida do país, os resultados aqui obtidos têm impacto direto na conservação destas espécies, porque trazem informações que podem ser utilizadas em planos futuros de conservação e manejo. / Along Brazilian coastal waters, either franciscana and Atlantic spotted dolphins exhibited distributional gaps, which is most likely resulting from changes in the environmental features between 20 and 33°S. The former species, franciscana (Pontoporia blainvillei), is a river dolphin with restricted distribution from Brazil to Argentina, recorded mainly up to 50 m deep over the inner shelf. The second species, Atlantic spotted dolphin (Stenella frontalis), is a delphinine dolphin distributed across the Atlantic Ocean, being mainly recorded over the continental shelf. The distribution patterns that these species showed in Brazil have a direct influence on the morphology/ecology and genetic struture of both species. Different approaches were applied to address the main goal of this study, which was investigating the influence of marine environment in shaping the distribution pattern, as well as genetic strcuture of franciscana and Atlantic spotted dolphin with emphasis in the Brazilian coastal waters. In the first chapter, I investigated the franciscana distribution in Brazil using an ecological niche modeling approach. In order to do that, I performed a review of records of the species along Brazial and, updated the limits of franciscana management areas (FMAs) and distributional gaps. The results suggested that gaps are within franciscana fundamental niche and, therefore, both gaps would be suitable for franciscana. However, the narrow of continental shelf seems to be the main factor inhibiting the presence of franciscana in these areas. Furthermore, the narrowing of continental shelf play a role to explain the genetic differentiation among FMAs. In the second and third chapters, the relationship between genetic distances and geographic and environmental distances were investigated both in a restrict and a broad scale. I found genetically distinct populations 12 across Atlantic spotted dolphin distribution based on mtDNA, that are probably resulting of Isolation-by-Distance and Isolation-by-Resistance related both with contemporary and past conditions (e.g. Last Glacial Maximum). Furthermore, I investigated population struture using genomic markers (Single Nucleotide Polymorphisms, SNPs) across Western South Atlantic, Caribbean and Eastern Atlantic. The results suggested at least three different populations, and therefore, confirmed previous hypothesis of an isolated population in the southeastern Brazil. Overall, I concluded that marine envinronment, especially the extension of continental shelf, bathymetry and sea surface temperature, are the main factors that explaning the distribution pattern of franciscana and Atlantic spotted dolphin in Brazil. Besides that, other process such as, social structure and phylopatry, as well as biogeographical process might be investigated in further studies. Franciscana is considered “Critically endangered” in Brazil, and Atlantic spotted dolphin has not enough data to determine its conservation status. Since both species are recorded in the most developed region of the country with high anthropic pressure, my results could help in future management and conservation plans for both species in a regional scale.

Hector�s dolphin (Cephalorhynchus hectori) is an endangered coastal species endemic to New Zealand. Their distribution, like other marine organisms, is intertwined with the dynamics of their local habitats, and at a larger scale, the coastal waters around New Zealand. The main purpose of this thesis was to identify specific habitat requirements of this rare dolphin. Hector�s dolphin distribution around the South Island was quantified along several temporal and spatial scales. Large-scale density analyses of abundance surveys found over half of the South Island�s current population occurred within only three main regions. Two of these strongholds are along the west coast and the third is located around Banks Peninsula on the east coast. Smaller-scale analyses at Banks Peninsula found the majority of the dolphin community was preferentially using core regions within the marine mammal sanctuary. Monthly surveys showed that in summer and autumn statistically more dolphins occurred within inshore regions ([less than or equal to]one kilometre), spread throughout the surveyed coastline. From May through winter, dolphin densities rapidly declined. Remaining dolphins were significantly clumped in more offshore waters of eastern regions. The lowest encounter rates occurred between August and September. Certain 'hotspots' consistently had higher dolphin densities throughout the study period while others were preferred seasonally. To address habitat preferences, surveys simultaneously collected oceanographic samples using a CTD profiler. In general, physical variables of the Peninsula�s eastern and southeastern waters varied less, despite being regularly exposed to upwellings and the varied presence of sub-tropical waters. Semi-sheltered bays and shallow inshore waters were highly variable and more susceptible to spatially discrete influences, such as localised river outflows and exchange events. Several hydrographic features were seasonally predictable due to their dependence on climate. The stratification and location of the two dominant water masses (neritic and sub-tropical) accounted for over half of the temporal and spatial variability observed in oceanographic data. Possible relationships between oceanographic features and aggregations of dolphins within Banks Peninsula were examined using global regression and a spatial technique known as geographical weighted regression (GWR). GWR models out-performed corresponding global models, despite differences in degrees of freedom and increased model complexity. GWR results found relationships varied over localised scales that were concealed by global methods. Monthly GWR models suggested the seasonal presence and strength of local oceanographic fronts influenced dolphin distribution. Dolphin aggregations coincided with the steepest gradients between water masses along eastern regions of the Peninsula, and strong exchange events along the edges of the study area. The continued survival of this endangered species is contingent on its protection. Long-term monitoring programmes are needed for the three main strongholds identified in this study. The occurrence of Hector�s dolphin 'hotspots' along frontal zones within Banks Peninsula also suggests alternative and increased protection strategies are needed for this sanctuary to be effective. In light of this thesis� findings and based on marine protection research, future sanctuaries need to consider why Hector�s dolphins are preferentially using particular regions and how their association with certain oceanographic features can help make informed decisions on more appropriate protected areas.