Loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles as well as their eggs and hatchlings have been protected on their nesting beach in South Africa (SA) since 1963. Both nesting populations were expected to show similar trends in recovery following the application of identical protection and conservation measures. The loggerhead nesting population has responded favourably to these protection efforts. In contrast, the leatherback nesting population showed an initial increase but is currently stable. The reason for this difference in response is thought to be due to differential offshore mortality of these two species. This prompted an investigation into the different sources of sea turtle mortality in the South Western Indian Ocean (SWIO). Specific aims were to identify and quantify sources of loggerhead and leatherback mortality on nesting beaches as well as in the oceans. Reasonable survivorship at all age classes is important to ensure recruitment of new nesting individuals into sea turtle populations. Mortality of nests, eggs per nest and hatchlings were quantified over two seasons for the loggerheads and leatherbacks nesting in SA. The beach was patrolled on foot to encounter and record females emerging from the ocean and later, hatchlings from their nests. The nests were then monitored during the incubation period and excavated once hatched. The fates of 925 nests were determined during these two nesting seasons (2009/2010 and 2010/2011). The main source of loggerhead and leatherback nest destruction was predation (8.6 percent and 15.7 percent respectively) followed by nest erosion (2.2 percent and 6.3 percent respectively). Overall nest success was high but higher for loggerheads (89 percent) than for leatherbacks (78 percent). The main cause of egg mortality for both species was early developmental arrest, followed by predation by ants and ghost crabs. Hatchlings en route to the sea were almost exclusively predated by ghost crabs (4.2 percent of emerged loggerhead hatchlings and 3.2 percent of emerged leatherback hatchlings). It appears that both species benefit from the coastal conservation efforts. When sea turtles leave the nesting beach, either as hatchlings or adults, conservation and monitoring becomes more difficult and sea turtles are exposed to a multitude of threats, including anthropogenic threats. Age classes tend to be spatially separated due to different habitat and dietary requirements. The type of threat sea turtles are exposed to thus depends on the current age class. Offshore sources of mortality in the SWIO were identified and where possible loggerhead and leatherback mortality was quantified and mapped spatially. Loggerheads were mostly exposed to and had the highest mortality in the artisanal fisheries in the SWIO (> 1000 per annum), inshore trawling (ca. 41 per annum), shark nets (protective gill nets) (21.6 ± 6.7 per annum) and the pelagic longline fishery (5.0 ± 4.4 per annum). In contrast, leatherbacks with a pelagic lifestyle, were mostly exposed to pelagic longline fisheries (7.8 ± 7.8 per annum). A spatial analysis of fishing activities indicated that leatherback home ranges overlapped 41percent with pelagic longline fishing activity in the SA EEZ, whereas the overlap between pelagic longliners and loggerhead home ranges was 29 percent. The quantified sources of mortality provide some explanation for the trend in the loggerhead nesting population but not the trend in the leatherback nesting population. Hatchling survivorship to adulthood was estimated to determine the viability of the two nesting populations as well as to determine whether offshore mortality was responsible for the difference in recovery of the two populations. Loggerhead hatchling survivorship to adulthood was estimated at between 2 and 10 per 1000 hatchlings, the minimum requirement for an increasing population. The adopted sophisticated model shows that leatherbacks have a survival rate of 5 to 10 per 1 000 hatchlings. However, this suggests that the population is increasing, but the leatherback population is stable. Perhaps the age to maturity of SA leatherbacks is greater than 12 years, or fisheries-related mortality affects younger age classes than initially thought. It is therefore recommended that the turtle monitoring area is extended to include other potential nesting grounds. In addition, observer or monitoring programs for commercial as well as artisanal fisheries needs to be extended throughout the SWIO to quantify sea turtle mortality. Ultimately a comprehensive multi-regional approach is required for the conservation of these highly migratory species.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As tartarugas marinhas são espécies ameaçadas, altamente migratórias que apresentam um ciclo de vida longo e uma ampla distribuição geográfica. Assim, melhorar a nossa compreensão sobre a ecologia espacial das tartarugas marinhas é essencial para a elucidação de aspectos da sua história de vida e para o desenvolvimento de medidas eficazes de conservação. Esta tese compreende um conjunto de artigos ou capítulos que visam contribuir ao conhecimento da ecologia espacial da tartaruga-de-couro, Dermochelys coriacea. Este estudo utilizou novas tecnologias como à telemetria por satélite (que proporciona um método útil para monitorar os movimentos de espécies migratórias) e um conjunto de ferramentas de geoprocessamento como abordagem metodológica que visou: examinar os movimentos e migrações da tartaruga-de-couro, identificar áreas de uso intenso e padrões espaço-temporais no uso do habitat, e integrar dados biológicos e oceanográficos para descrever as estratégias comportamentais desta espécie. Cinco tartarugas-de-couro (um subaduto, dois machos adultos e duas fêmeas adultas) foram equipadas com transmissores por satélite no Atlântico Sul Ocidental entre 2005 e 2008. Além de fornecer dados de localização geográfica os tansmissores permitiram registrar informações de mergulho tais como profundidade e duração máxima e media dos mergulhos, perfis completos de mergulhos individuais e dados de temperatura do mar. Movimentos e migrações de tartarugas-de-couro marcadas no Atlântico Sul foram documentados pela primeira vez. Alem disso, foi posível identificar áreas de uso intenso (ou alimentação) previamente desconhecidas para a espécie, assim como uma residência sazonal nestas áreas localizadas em águas tropicais e temperadas fora da costa sul-americana (19-45S). A sazonalidade dos movimentos esteve intimamente associada a processos físicos sazonais de pequena e mesoescala. Dependendo do ambiente marinho explorado, durante os períodos de residência, as tartarugas apresentaram diferentes estratégias alimentares identificadas através da análise dos padrões de mergulho. / Sea turtles are long-lived, highly migratory endangered species with a wide distribution. Thus improving our knowledge of the spatial ecology of sea turtles is essential for elucidating aspects of their life history and for the development of effective conservation measures. This thesis comprises a collection of articles or chapters that aim to contribute to the knowledge of the spatial ecology of the leatherback turtle, Dermochelys coriacea. This study used new technologies such as satellite telemetry (which provides a useful approach for tracking the movements of migratory species) and a set of geoprocessing tools as a methodological approach that aimed to: examine the movements and migrations of leatherback turtles, identify high use areas and spatio-temporal patterns of habitat use, and integrate biological and environmental data to describe foraging strategies of this species. Five leatherback turtles (a subadut, two adult males and two adult females) were fitted with satellite transmitters in the Southwest Atlantic between 2005 and 2008. Besides providing geographical location data the transmitters also recorded dive information such as mean and maximum dive depth and duration, individual dive profiles and water temperature data. For the first time the movements and migrations of leatherback turtles tagged in the South Atlantic were documented. Previously unidentified high use areas (or foraging areas) were recognized for this species, also a seasonal residence along those areas located in tropical and temperate areas off the coast of South America (19-45 S). The seasonal movements were closely associated with small and mesoscale physical seasonal processes. Depending on the marine environment exploited during periods of residence, the turtles showed different foraging strategies identified through the analysis of the diving patterns.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As tartarugas marinhas são espécies ameaçadas, altamente migratórias que apresentam um ciclo de vida longo e uma ampla distribuição geográfica. Assim, melhorar a nossa compreensão sobre a ecologia espacial das tartarugas marinhas é essencial para a elucidação de aspectos da sua história de vida e para o desenvolvimento de medidas eficazes de conservação. Esta tese compreende um conjunto de artigos ou capítulos que visam contribuir ao conhecimento da ecologia espacial da tartaruga-de-couro, Dermochelys coriacea. Este estudo utilizou novas tecnologias como à telemetria por satélite (que proporciona um método útil para monitorar os movimentos de espécies migratórias) e um conjunto de ferramentas de geoprocessamento como abordagem metodológica que visou: examinar os movimentos e migrações da tartaruga-de-couro, identificar áreas de uso intenso e padrões espaço-temporais no uso do habitat, e integrar dados biológicos e oceanográficos para descrever as estratégias comportamentais desta espécie. Cinco tartarugas-de-couro (um subaduto, dois machos adultos e duas fêmeas adultas) foram equipadas com transmissores por satélite no Atlântico Sul Ocidental entre 2005 e 2008. Além de fornecer dados de localização geográfica os tansmissores permitiram registrar informações de mergulho tais como profundidade e duração máxima e media dos mergulhos, perfis completos de mergulhos individuais e dados de temperatura do mar. Movimentos e migrações de tartarugas-de-couro marcadas no Atlântico Sul foram documentados pela primeira vez. Alem disso, foi posível identificar áreas de uso intenso (ou alimentação) previamente desconhecidas para a espécie, assim como uma residência sazonal nestas áreas localizadas em águas tropicais e temperadas fora da costa sul-americana (19-45S). A sazonalidade dos movimentos esteve intimamente associada a processos físicos sazonais de pequena e mesoescala. Dependendo do ambiente marinho explorado, durante os períodos de residência, as tartarugas apresentaram diferentes estratégias alimentares identificadas através da análise dos padrões de mergulho. / Sea turtles are long-lived, highly migratory endangered species with a wide distribution. Thus improving our knowledge of the spatial ecology of sea turtles is essential for elucidating aspects of their life history and for the development of effective conservation measures. This thesis comprises a collection of articles or chapters that aim to contribute to the knowledge of the spatial ecology of the leatherback turtle, Dermochelys coriacea. This study used new technologies such as satellite telemetry (which provides a useful approach for tracking the movements of migratory species) and a set of geoprocessing tools as a methodological approach that aimed to: examine the movements and migrations of leatherback turtles, identify high use areas and spatio-temporal patterns of habitat use, and integrate biological and environmental data to describe foraging strategies of this species. Five leatherback turtles (a subadut, two adult males and two adult females) were fitted with satellite transmitters in the Southwest Atlantic between 2005 and 2008. Besides providing geographical location data the transmitters also recorded dive information such as mean and maximum dive depth and duration, individual dive profiles and water temperature data. For the first time the movements and migrations of leatherback turtles tagged in the South Atlantic were documented. Previously unidentified high use areas (or foraging areas) were recognized for this species, also a seasonal residence along those areas located in tropical and temperate areas off the coast of South America (19-45 S). The seasonal movements were closely associated with small and mesoscale physical seasonal processes. Depending on the marine environment exploited during periods of residence, the turtles showed different foraging strategies identified through the analysis of the diving patterns.

La forte hétérogénéité de l'écosystème marin se traduit par une production inégale des ressources sur un large éventail d'échelles spatio-temporelles, qui conditionne par conséquent les déplacements des tortues marines. Considéré comme l’un des plus dynamiques au monde, le plateau des Guyanes est une région très complexe d'un point de vue océanographique et qui héberge trois des sept espèces de tortues marines présentes dans le monde (la tortue olivâtre, la tortue verte et la tortue luth). L'objectif de cette thèse était de comprendre comment les contraintes océanographiques peuvent-elles influencer les déplacements en mer de ces trois espèces. Le déploiement de 55 balises satellites sur des femelles reproductrices en Guyane française a permis de fournir des informations sur leurs trajectoires, sur leur comportement de plongée et sur les caractéristiques de leur environnement. Notre étude a mis en évidence une forte plasticité comportementale interspécifique qui semble être principalement dictée par les traits reproducteurs, les stratégies de reproduction, les conditions locales de l'habitat ou encore les adaptations physiologiques. / The strong heterogeneity of the marine ecosystem leads to a patchy distribution of the resources in time and space, shaping therefore the movements of sea turtles. Considered as the most dynamic ecosystem in the world, the Guiana shield is a highly dynamic system which hosts three of the seven sea turtle species in the world (the olive ridley, the green turtle and the leatherback turtle). The aim of this thesis was to understand how the oceanographic constraints can influence the at-sea movements of these three species during the reproduction and the migration phases. The deployment of 55 satellite tags on adult females in French Guiana provided information on their trajectories, their diving behavior and on the environment encountered. Our study shows a strong behavioral plasticity between species, which seems to be mainly dictated by the reproductive traits and strategies, the local conditions of the habitat and the physiological adaptations.

Broward County, Florida is a popular tourism destination. Due to its popularity, much of the shoreline has been modified and natural habitats were replaced with infrastructure such as houses, condominiums, resorts, and restaurants. The same Broward County beaches utilized by tourists and residents are important for three species of nesting sea turtles, including the Leatherback, Dermochelys coriacea, Loggerhead, Caretta caretta, and Green, Chelonia mydas, Turtles. The Broward County Sea Turtle Conservation Program (BCSTCP) collects yearly data in order to study these endangered reptiles. Increased anthropogenic effects including further coastal development (public & private), public beach events, public beach access, as well as natural events, have caused these important nesting beaches to erode and narrow. In an effort to control this erosion damage, Broward County has performed a number of beach nourishment projects. This study found yearly fluctuations in sea turtle hatching and emergence success rates, and years of beach nourishment projects significantly decreased these rates. Yearly hatching data available from Broward County concludes that beach nourishment, as well as hurricanes and tropical storms cause decreases in sea turtle hatching and emergence success rates in Broward County. Additionally, nest depth and sea turtle size increases the hatching and emergence success rates from females that are not too large or too small that nest in Broward County.

Loggerhead and leatherback sea turtles nest on the beaches of the north-eastern portion of Kwazulu-Natal within the iSimangaliso Wetland Park. Loggerheads place ~60 percent of all nests within an 8 km stretch of beach, whereas leatherbacks tend to space their nests more evenly along the entire length of the monitoring area. The study aimed to determine nest site fidelity of loggerheads and leatherbacks (using four decades of nesting data housed by Ezemvelo KZN Wildlife) and the factors that influence nest site selection of both species within the 56 km of turtle monitoring area (32N to 100S) and the 5 km area of high-density loggerhead nesting (0N to 12N). The effectiveness of nest site selection was then determined through the hatching success of loggerheads over the 5km area (0N to 12N). Results showed that loggerheads show a high degree of nest site fidelity (~3 km) with nest site fidelity of individuals increasing over subsequent seasons of nesting, as well as these individuals using the same stretches of beach for nesting (the most popular area being 1N to 4N for repeat nesters). Leatherbacks displayed nest site fidelity of ~9 km and this did not increase over successive seasons of nesting. In terms of nest site selection, loggerheads and leatherbacks both avoided areas where low shore rock was present, whereas both species preferred nesting on beaches of intermediate morphodynamic state. Leatherback nesting was significantly higher in areas with wider surf zones. Both species were able to surpass the high water mark when nesting as nests below this point would be almost certainly doomed. Hatching success of loggerheads was comparative to high (83 %) relative to other studies, however, nest success varied across the beach from beacon 1N to 12N. Areas where highest nest success was observed were not areas of highest nest density presumably due to artificial lighting. Results from this study increase our understanding of the evolutionary biology of loggerhead and leatherback turtles in South Africa and the effectiveness of loggerhead nest site selection through hatching success.

<p dir="ltr">The Leatherback Sea Turtle (<i>Dermochelys coriacea</i>) is a globally vulnerable species suffering from declining populations due to anthropogenic pressures. There are seven recognized Leatherback Sea Turtle regional management units; however, the Southeast Atlantic unit is considered data deficient. Bioko Island, Equatorial Guinea, is a primary nesting rookery for the Southeast Atlantic regional management unit and has some of the world’s highest numbers of nesting Leatherback Sea Turtles. Despite Bioko Island’s importance to the species, little is known about the nesting ecology or post-nesting migratory movement and behaviors of its nesting Leatherback Sea Turtles. Here, I present the findings of two individual research projects on the nesting ecology of Leatherback Sea Turtles on Bioko Island. First, I explored the long-term clutch success rates (i.e., hatching success and emergence success) of <i>in situ</i> Leatherback Sea Turtle nests on Bioko and searched for associated variables. I found significant spatiotemporal variation over nine nesting seasons, likely driven by individual beach characteristics rather than regional climate patterns. Secondly, I described a novel effort to use solar-reliant towable transmitters to track the post-nesting migratory movements and behaviors of Leatherback Sea Turtles nesting on Bioko Island. With the results from each project, I make recommendations to further the current conservation and research initiatives of Leatherback Sea Turtles.</p>

Les tortues marines, espèces emblématiques des écosystèmes marins, sont de plus en plus menacées par les effets directs et indirects des activités humaines. Leur cycle de vie est complexe, partagé entre divers habitats, souvent très éloignés les uns des autres. Leur conservation nécessite donc d'identifier les habitats occupés à chaque stade de vie et les routes migratoires empruntées entre ces différents habitats. Si l'écologie spatiale des tortues adultes est relativement bien connue, notamment grâce au suivi par satellite, il n'en va pas de même pour les juvéniles qui se développent plusieurs années en milieu pélagique sans pouvoir être suivis. Dans ce contexte, les simulations numériques constituent un outil adapté pour explorer la dispersion des tortues juvéniles à partir de leurs plages de naissance. Jusqu'à présent il a le plus souvent été supposé dans ces simulations que les juvéniles dérivaient passivement avec les courants marins. Dans ce travail de thèse nous présentons STAMM (Sea Turtle Active Movement Model), un nouveau modèle de dispersion active des tortues juvéniles qui s'attache à dépasser l'hypothèse initiale d'une dérive purement passive. Dans STAMM, les juvéniles simulés se déplacent sous l'influence de la circulation océanique et d'une nage motivée par la recherche d'habitats favorables. Ce modèle est appliqué ici à l'étude de la dispersion des juvéniles de trois populations de tortues marines : les tortues luths (Dermochelys coriacea) du Pacifique Ouest et de l'Atlantique Nord-Ouest puis les tortues caouannes (Caretta caretta) de l'ouest de l'océan Indien. Nos résultats montrent que, même si la circulation océanique détermine, à grande échelle, les zones de dispersion, la prise en compte des mouvements motivés par l'habitat augmente considérablement le réalisme des simulations et impacte profondément la distribution spatiale et temporelle des individus simulés à l'intérieur de leur zone de dispersion. Les mouvements motivés par l'habitat induisent notamment des migrations saisonnières en latitude qui réduisent la mortalité par hypothermie. Ces mouvements induisent également une concentration des individus simulés dans des zones productives (comme les upwellings de bord Est) inaccessibles en dérive passive. Ces résultats questionnent la vision classique des juvéniles circulant passivement autour des gyres océaniques et devraient rapidement être pris en compte pour la mise en place de mesures de conservation ciblées visant les tortues marines juvéniles. / Sea turtles are increasingly threatened by the direct and indirect effects of human activities. Their life cycle is complex, shared between various, and often very distant, habitats. Their conservation therefore requires identifying the habitats occupied at each stage of life and the migration routes between these different habitats. While the spatial ecology of adult turtles is relatively well known, particularly through satellite monitoring, the situation is not the same for juveniles which pelagic development phase remains largely unobserved. In that context, numerical simulation constitutes an appropriate tool to explore the dispersal of juvenile sea turtles from their natal beaches. Until now, simulations were mostly performed under the assumption that juveniles disperse passively with oceanic currents. In this PhD thesis we present STAMM (Sea Turtle Active Movement Model), a new model of active dispersal that aims to go beyond the initial hypothesis of passive drift. In STAMM, juvenile sea turtles move under the influence of ocean currents and swimming movements motivated by the search for favorable habitats. This model is applied here to the study of the dispersal of juveniles from three sea turtle populations: leatherback turtles (Dermochelys coriacea) of the Western Pacific and the Northwest Atlantic Oceans, and loggerhead turtles (Caretta caretta) of the Western Indian Ocean. Our results show that, although ocean currents broadly shape juvenile dispersal areas, simulations including habitat-driven movements provide more realistic results than passive drift simulations. Habitat-driven movements prove to deeply structure the spatial and temporal distribution of juveniles. In particular, they induce seasonal latitudinal migrations that reduce cold induce mortality. They also push simulated individuals to concentrate in productive areas that cannot be accessed through pure passive drift. These results challenge the classical view of juveniles circulating passively around oceanic gyres. They should rapidly be taken into account for the implementation of targeted conservation measures concerning juvenile sea turtles.

Sex determination in leatherback sea turtles is directed primarily by the temperatures a clutch experiences during the middle third of development. Warmer temperatures tend to produce females will cooler temperatures yield males. Nest temperatures can vary spatially and temporally. During the 2010 and 2011 nesting seasons, this study estimated the hatchling sex ratio of leatherback sea turtles on Sandy Point National Wildlife Refuge (SPNWR), St. Croix, U.S. Virgin Islands. I measured sand temperatures from May- August and across the spatial range of leatherback nesting habitat. I spatially interpolated those temperatures to create maps that predicted temperatures for all nests incubating on SPWNR. Nest temperatures were also directly measured and compared with predicted nest temperatures to validate the prediction model. Sexes of dead-in-nest hatchlings and full term embryos were used to confirm the sex-temperature response. The model showed that microclimatic variation likely impacts the production of both sexes on SPNWR. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2013.

Les organismes font face à des compromis entre leur reproduction, leur maintenance et leur survie, dont découlent des stratégies adaptatives énergétiques, comportementales et écologiques.Ce travail de thèse propose de préciser les stratégies de reproduction chez la tortue luth Dermochelys coriacea nidifiant en Guyane. Nous avons étudié les caractéristiques maternelles, les performances de reproduction et les potentiels liens existants entre la migration et la reproduction chez une population d’individus d’identité connue, suivis grâce à un suivi longitudinal original combinant biométrie, physiologie et biologie moléculaire.Premièrement nous montrons que les tortues luth opèrent comme des reproducteurs sur capital, i.e., leur reproduction repose sur les ressources stockées sous forme de réserves corporelles pendant la migration précédant la saison de ponte. D’autre part, nous suggérons que les femelles ajustent la durée de leur migration en fonction des conditions océanographiques rencontrées pendant la migration. Ceci leur permettrait, à l’échelle de la vie, de répondre au compromis entre la reproduction en cours et les reproductions futures. Enfin, notre démarche souligne l’importance de prendre en compte les caractéristiques individuelles dans la compréhension des stratégies de reproduction, et de manière ultime pour l’établissement de modèles réalistes de la dynamique des populations, notamment dans le cas d’espèces emblématiques telles que les tortues marines. / Organisms face trade-offs between their reproduction, maintenance and survival, from which result adaptative strategies at the energetics, behavioural and ecological levels.This PhD work investigates the reproductive strategies used by leatherback turtles, Dermochelys coriacea, nesting in French Guiana. We investigated maternal characteristics, reproductive output, and the possible links between migration and reproduction in a population of known identity, studied through a unique longitudinal monitoring, based on complementary approaches combining biometry, physiology and molecular biology.First, we found that leatherback turtles are capital breeders, i.e. females’ reproductive output displayed during their nesting season relies on body reserves previously stored during their migration. Second, we suggested that leatherback females adjust the duration of the migration according to the oceanographic conditions they experienced during migration. At a lifetime scale, this may allow females to face the trade-off between current and future reproductions. Finally, our approach highlights the importance to take into account individual characteristics in order to better understand reproductive strategies, and further assess realistic models of population dynamics, particularly when considering emblematic species such as sea turtles.