Dissertations / Theses on the topic 'Leatherback turtle'

I have quantified the energy requirements of leatherback turtles (Dermochelys coriacea) throughout development, and examined growth rates, resource requirement and availability, and anthropogenic threats from the commercial fishery. I demonstrated that the use of the doubly labeled water (DLW) method to determine field metabolic rate in marine turtles is constrained by low metabolic (MR) and high water turnover rates (Chapter 2). For fed and fasted turtles, water turnover rates were 9.57±1.33% and 6.14±0.65% TBW day−¹1 and MR (from respirometry) was 28.66±5.31 kJ kg−¹ day−¹ and 13.77±1.49 kJ kg−¹ day−¹, respectively. This led to isotope turnover (kd:ko) ratios of 0.91±0.02 for fed turtles and 1.08±0.16 for fasted turtles, producing negative MRs for fasted turtles. While I showed that for fed turtles the DLW method was consistent with respirometry the use of DLW in fasting turtles differed from respirometry by 440%. The fact that DLW does not work in certain situations is a rare finding that will be of broad interest in the field of energetics. Having determined that the DLW method is constrained in marine turtles I then turned to rearing leatherbacks in the laboratory to measure growth (Chapter 3) and determine energy intake (Chapter 4). For the first time I was able to rear several leatherbacks from hatching to juveniles. Leatherbacks maintained an average growth rate of 31.9 ± 2.8 cm year−¹ in straight carapace length (SCL) throughout the study period. The captive leatherbacks matched the length-mass relationship of wild juveniles and adults. A von Bertalanffy growth function (VBGF) predicted age-at-maturity for leatherbacks of 15.3 years. Bycatch data, supplemented with growth curve data, indicate that leatherbacks will reach the minimum length at which they are found interacting with fisheries (drift gill net and longline) in less than 3 years, suggesting they are exposed to threats from marine fisheries for > 80 % of their life before maturity is attained. I estimated that the majority of the Pacific Ocean population of leatherbacks is made up of 2-6 year old juveniles (137,368 turtles) consuming 1.6 x 10⁶ tonnes of jellyfish year−¹. These turtles are restricted to warmer equatorial waters where primary productivity and, possibly, jellyfish abundance are low.

Adult leatherback turtles (Dermochelys coriacea) exhibit thermal gradients between their bodies and the environment of ≥ 8 °C in sub-polar waters and ≤ 4 °C in the tropics. There has been no direct evidence for thermoregulation in leatherbacks although modelling and morphological studies have given an indication of how thermoregulation may be achieved. Using a cylindrical model of a leatherback I investigated the extent to which heat production by muscle activity during variation of swim speed could be used in a leatherback’s thermal strategy. Drag force of a full scale cast of a leatherback was measured in a low velocity wind tunnel to obtain an estimate of the metabolic cost needed to offset drag. It is apparent, from this modelling, that heat flux from the body and flippers, activity and body and water temperatures are important variables to measure in order to fully classify the thermoregulatory response of live leatherbacks. Using captive juvenile leatherbacks of 16 and 37 kg I show for the first time that leatherbacks are indeed capable of thermoregulation. In cold water (< 25 °C), flipper stroke frequency increased, heat loss through the plastron, carapace and flippers was minimized, and a positive thermal gradient of up to 2.3 °C was maintained between body and environment. In warm water (25 – 31 °C), turtles were inactive and heat loss through their plastron, carapace and flippers increased, minimizing the thermal gradient (0.5 °C). In juvenile leatherbacks, heat gain is controlled behaviourally through activity while heat flux is regulated physiologically, presumably by regulation of blood flow distribution. Using a scaling model, I show that a 300 kg adult leatherback is able to maintain a maximum thermal gradient of 18.2 °C in cold sub-polar waters. Thus, by employing both physiological and behavioural mechanisms, adult leatherbacks are able to keep warm while foraging in cold sub-polar waters and to prevent overheating in a tropical environment, greatly expanding their range relative to other marine turtles.

During spring and summer 2003 data were collected from the leatherback population nesting on a beach in Grenada, West Indies. By attaching data logging devices to leatherbacks I was able to record certain aspects of their behaviour whilst at sea between nesting events. Three different device types were used in these studies: Satellite Relayed Data Loggers (SRDLs), Time depth recorders (TDRs) and mouth opening sensors. The SRDLs as well as providing location fixes, transmit limited dive data to overpassing satellites. After introducing various aspects of leatherback biology and ecology (chapter 1) and describing the methodologies used to collect and process the data (chapter 2) I then go on to validate this data collected by the SRDLs (chapter 3). This was achieved by attaching, to the same animal, an SRDL and a TDR (which record depth and temperature at a predetermined sampling interval). The fourth chapter focuses specifically on the data acquired by the TDRs particularly in relation to diel periodicity and the function of deep dives. Chapter five pertains to the crepuscular diving behaviour of leatherbacks. In this chapter I predict how the turtles will behave according to optimal foraging theory and then investigate these predictions using the data collected by the TDRs. Chapters six and seven involves a thorough investigation into the mouth opening data collected. In chapter six I examine the breathing patterns and mouth opening behaviour of the turtle during dives whilst in chapter seven I focus on some unexpected oscillations being recorded by the mouth opening sensor.

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.

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.

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.

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.

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

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

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.

A beach conservation programme protecting nesting loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles in South Africa was started in 1963. As initial numbers of nesting females were low for both species (107 loggerheads and 24 leatherbacks) it was proposed that the protection of eggs, hatchlings and nesting females along the nesting beach would induce population growth and prohibit local extinction. Today, 50 years later, the loggerhead population exceeds 650 females per annum, whereas the leatherback population counts about 65 nesting females per year. The trend for leatherback turtles is that the population has been stable for about 30 years whereas loggerheads are increasing exponentially. Thus, this thesis investigated several life-history traits to explain the differing responses to the ongoing beach conservation programme. Reproductive output and success were assessed for both species; it was hypothesised that environmental conditions are sub-optimal for leatherback turtles to reproduce successfully. It was ascertained that nesting loggerhead females deposit larger clutches than leatherbacks (112 ± SD 20 eggs and 100 ± SD 23 eggs, respectively), but that annual reproductive output per individual leatherback female exceeds that of loggerhead turtles (±700 eggs and ±448 eggs, respectively) because they exhibit a higher intra-seasonal nesting frequency (leatherbacks n = 7 and loggerheads n = 4 from Nel et al. 2013). Emergence success (i.e. the percentage of hatchlings produced) per nest was similar for both species (loggerhead 73.6 ± SD 27.68 % and leatherback turtles 73.8 ± SD 22.70 %), but as loggerhead turtles nest in greater numbers, i.e. producing more hatchlings per year, the absolute population growth potential favours the loggerhead turtle. The second factor investigated was sex ratio because sea turtles display temperature-dependent sex determination (TSD) where extreme incubation temperatures can skew the sex ratio (i.e. feminising or masculinising a clutch). It was suspected that leatherback turtles are male-biased as this is the southern-most rookery (for both species). Further, leatherback nests are generally closer to the high tide mark, which might induce a cooling effect. Standard histological techniques were applied to sex hatchlings and a generalized linear model (GLM) was used to approximate annual sex ratio. Loggerhead sex ratio (2009 - 2011) was estimated at 86.9 ± SE 0.35 % female-biased; however, sufficient replication for the leatherback population was only obtained for season 2010, which indicated a 97.1 % (95 % CI 93.3 - 98.7) female bias. Both species are, thus, highly female-biased, and current sex ratio for leatherback turtles is not prohibiting population growth. Current sex ratios, however, are not necessarily indicative of sex ratios in the past which would have induced present population growth. Thus, to account for present population growth profiles, sex ratios from the past needed to be ascertained. Annual sex ratios (1997 - 2011) were modelled from historical air and sea surface temperatures (SSTs) but no significant change over time was obtained for either loggerhead or leatherback turtles (linear regression; p ≥ 0.45). The average sex ratio over this 15-year period for the South African loggerhead turtle was approximated at 77.1 ± SE 3.36 % female-biased, whereas leatherbacks exhibited a 99.5 ± SE 0.24 % female bias. Re-analysing data from the mid-80s by Maxwell et al. (1988) also indicated a 77.4 % female bias for the South African loggerhead population. It is, therefore, highly likely that sex ratios of the South African loggerhead and leatherback sea turtle populations have been stable for at least three decades and are not accountable for the differing population growth profiles as they are displayed today. Another possibility that could explain the opposed population growth profiles is the time taken for animals to replace themselves, i.e. age at maturity. It was suspected that age at maturity for the South African loggerhead turtle is comparable with that for leatherbacks. Using data from a 30-year mutilation tagging experiment (i.e. notching), age at first reproduction for South African loggerhead females was estimated. Results ranged broadly but a mean of 36.2 ± SD 7.71 years was obtained using a Gaussian distribution. Age at reproduction of the South African leatherback turtle was not determined but the literature suggests a much younger age of 13.3 - 26.8 years (Zug & Parham 1996, Dutton et al. 2005, Avens et al. 2009, Jones et al. 2011). Therefore, population growth would favour leatherback turtles as they exhibit a much shorter generation time. Finally, it was concluded that all life-history parameters investigated favour leatherback turtles, yet loggerheads are displaying population growth. However, as there were no obvious constraints to population growth on the nesting beach, it is suspected that population growth of the South African leatherback turtle is either unobserved (due to inadequate monitoring not capturing sufficient numbers of nesting events to establish a trend) or that population growth is prohibited by some offshore factor such as industrial fisheries (or some other driver not yet identified). Monitoring should, thus, be expanded and offshore mortality monitored as the leatherback population nesting in South Africa is still critically endangered with nesting numbers dangerously low.

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.

Diving bradycardia, or a decrease in heart rate while diving, has been observed in a wide variety of species, from frogs to seals. The degree to which an animal lowers its heart rate during a submergence may vary depending on the behaviour of the animal. The leatherback sea turtle (Dermochelys coriaced) is an active diver, and has a metabolic rate that is higher than expected for a reptile of its size. The purpose of this research was to gain an understanding of the cardiovascular response to diving made by the leatherback turtle and to integrate this information with what is known of the turtle's diving behaviour and metabolism. Instruments capable of recording heart rate, dive duration and dive depth were deployed on leatherback females as they lay eggs on a nesting beach. Heart rate and diving variables were recorded during the internesting interval when turtles were freely diving at sea. Instruments were recovered when the turtles returned to the nesting beach to lay more eggs. Relationships between the turtle's diving behaviour and heart rate were examined, and comparisons were made between diving heart rates, surface heart rates, and long-term heart rates. Dive records show that leatherback turtles dive continually throughout the internesting interval. The brief amount of time spent at the surface between dives suggests that these turtles rely mainly on aerobic metabolism for routine dives, and all observed dives fell within the calculated aerobic dive limit. No significant diel differences existed for leatherback turtles from the Playa Grande nesting population, but dives became shorter and shallower as the internesting interval drew to a close. Neither dive duration nor dive depth was strongly related to heart rate. Diving heart rates were significantly lower than surface heart rates for leatherback turtles. The most likely cause of the observed diving bradycardia is increased pulmonary resistance accompanied by variable degrees of systemic perfusion. The fact that decreases in heart rate during diving were not extreme suggests that turtles do not drastically lower their metabolic rate while diving during the internesting interval. Long-term heart rates were more similar to diving heart rates than to surface heart rates.

The global population of leatherback sea turtles is decreasing worldwide, with extinction predicted for some populations within 15 years. The population of leatherbacks nesting at Sandy Point National Wildlife Refuge (SPNWR), St. Croix, USVI, displayed a significant population increase from 1982 2001 but has experienced a slowed recovery since then. To better understand the causes of this decline, a historical database of SPNWR nesting female data was utilized to investigate trends in reproductive indices. Since 2001, average remigration interval (RI) has increased significantly, while average number of clutches laid, hatch success, hatchling production, and the percentage of neophytes recruited annually have decreased. Annual remigrant numbers have been stable to increasing, suggesting that adult survivorship remains high. To assess whether maternallyderived factors may be influencing clutch production and low hatch success, blood samples were collected by saturation sampling during nesting. Circulating estradiol, testosterone, and progesterone were evaluated in conjunction with reproductive data. All hormones were highest at deposition of the first clutch and declined progressively with each consecutive clutch, as previously observed in other sea turtle species. Increased clutch production in remigrants was associated with higher estradiol levels compared to neophytes, presumably due to ovarian size and maturity. Contrary to observations in Pacific leatherbacks, progesterone decreased significantly with successive nests and total levels of estrogen were significantly lower, suggesting Atlantic leatherbacks may undergo a longer migration or spend more time in the feeding grounds prior to migrating. Linear Mixed Effect (LME) modeling was employed to determine whether hormone levels at nesting might serve as indicators of reproductive variables. Because models for all hormones were individual specific, a population model could not be developed that effectively utilized hormone levels at nesting to predict clutch size, hatch success, age or RI. However, number of clutches laid may potentially be predicted based on individually tailored estrogen models. Decreased recruitment (due to increased mortality of early life stages, altered sex ratios, or delayed age to sexual maturity), decreased productivity, and increased RI (possibly due to diminished foraging ground productivity) appear primarily responsible for current population trends which threaten the population's future.

Despite facing threat of extirpation in the eastern Pacific, the critically endangered leatherback turtle (Dermochelys coriacea) appears to be thriving in the Atlantic. The purpose of my dissertation was to establish a baseline of biological data for the leatherback at the northern limit of its nesting range in the northwestern Atlantic (Florida) to inform management. From six years of empirical field data collected on nesting female leatherbacks, I addressed four major objectives of the Federal (US) Recovery Plan for the east coast of Florida. 1) I determined the rate of increase in observed nest numbers since standardized nest surveys began in 1979. From these data collected at 70 beaches and using a multilevel modeling approach, I found a dramatic increase of 11.3 ± 1.9% each year in the number of nests. 2) By tagging and recapturing individual females as well as marking nests for inventories at one high-density nesting beach, I determined several critical population parameters. The annual survival rate was 95.6% for nesting females and the yearly nesting population size was 71 ± 23 turtles at my Juno Beach study site (19.4 km); statewide the estimate will be higher. The average remigration interval was 2.2 +/- 0.5 years, clutch frequency was 4.1 +/- 0.9 nests/season, and the average clutch size was 69.0 +/- 18.2 eggs/female. 3) I used novel GPS tags and conventional tag returns to discover the full nesting range and true clutch frequency of individual turtles. Leatherbacks in Florida exhibit weak nest site fidelity by nesting at broad spatial scales, distributing at least five nests within a single season up to 139.8 km from first encounter. 4) Finally, I used microsatellites and mtDNA to determine the relatedness of leatherbacks in Florida and found few family groupings, indicating that this rookery has been established through immigration and not through a founding event, as there is no evidence of a genetic bottleneck. Although the Florida population is relatively small compared to other Caribbean mainland rookeries, it has the potential to contribute to further increases of leatherbacks in the Atlantic as well as contributing genetic variation, thereby achieving objectives of the US Recovery Plan.
Dissertation

Oxygen consumption (V02)a s monitored in six juvenile leatherback turtles (Dermochelys coriacea) imported from the Virgin Islands (UK) and kept in a covered outdoor facility at the University of British Columbia. Growth data suggest that leatherbacks can attain a mature size in as little as 5 1/2 to 6 years, much faster than other sea turtles, and reach 90 kg ( > 100 cm) in as little as 3 years when they may be thermally capable of venturing into temperature zones for greater resource availability. Animals were held at 24°C and their Routine Metabolic Rate (RoMR) was measured during the first year at 24°C as well as after acute exposure to 14, 19, 29 and 34°C at four different body masses (0.1, 0.5, 1 and 10 kg). Increasing temperature, as well as body mass, significantly increased V0 2 .Maximum flipper stroke rate occurred at the acclimation temperature (24°C), falling with exposure to lower and higher temperatures. In contrast, breathing frequency (fR) was unaffected by changes in temperature across all size classes. The intraspecific scaling exponent for VO2 over an order of magnitude change in body mass at 24°C was 0.88, very similar to allometric scaling exponents of other reptiles. The scaling exponent increased at 14°C and decreased at 34°C. lntraspecific scaling exponents are temperature dependent in leatherback turtles and this may also be the same in other reptiles.
Science, Faculty of
Zoology, Department of
Graduate

Illegal harvesting of sea turtle eggs is a reality worldwide. To ensure nest protection, conservation programs need to be implemented with specific measures for each nesting site location, taking in account poaching impact and climate impact. Nesting preferences of leatherback turtles in Playa Tres, Caribbean Costa Rica, were analysed, as well as nesting distribution among areas and sectors. The moon impact was also studied, since beach profile is directly related to it. Both factors analysed by beach profile (beach length and beach slope) appeared to have influence on the emergence and nesting decision. Distribution of nests accordingly to the beach profile was analysed showing some nests lost due to the rising water. The nesting distribution showed that leatherback turtles prefer the northern areas of the beach, and gentle slopes that prevent water rising. Leatherback nests suffered a severe decline. We estimate that 45% of nests laid during nesting season disappeared, due to poaching or due to the proximity to the water line. This study emphasizes the importance of Playa Tres protection, and may help in creating better protective measures taking in account the particularities of the beach.
A caça furtiva de ovos de tartarugas marinhas é uma realidade em todo o mundo. Para garantir a proteção dos ninhos, programas de conservação precisam ser implementados com medidas específicas para cada local de nidificação, levando em consideração o impacto da caça furtiva e o impacto das alterações climáticas. As preferências de nidificação da tartarugas-de-couro em Playa Tres, na Costa Rica Caribenha, foram analisadas, bem como a distribuição de nidificação entre áreas e setores. O impacto da lua também foi estudado, uma vez que o perfil da praia está diretamente relacionado a ele. Ambos os fatores analisados pelo perfil da praia (comprimento e declive da praia) parecem ter influência na emergência e decisão de nidificação. A distribuição dos ninhos de acordo com o perfil da praia foi analisada mostrando alguns ninhos perdidos devido à subida da água. A distribuição da nidificação mostrou que as tartarugas-de-couro preferem as áreas ao norte da praia e encostas suaves, que evitam à subida do nível da água. Os ninhos de tartarugas-de-couro sofreram um declínio severo. Estimamos que 45% dos ninhos postos durante a época de nidificação desapareceram, devido à caça furtiva ou à proximidade da linha de água. Este estudo enfatiza a importância da proteção de Playa Três, e pode ajudar na criação de melhores medidas de proteção levando em consideração as particularidades da praia.
Mestrado em Biologia Aplicada