Leatherback Research Articles

Impacts of nest temperatures on leatherback reproductive success, hatchling morphology, and performance in South Florida

Leatherback turtles Dermochelys coriacea are experiencing population declines due to various anthropogenic threats. Beaches play a crucial role in the survival of sea turtle species since reproductive success is affected by environmental conditions inside the nest. Climate change is predicted to increase sand temperatures and affect rainfall, which will change the nest microenvironment, and thus may alter not only hatch and emergence success but also hatchling morphology and performance. This study examined the relationship between nest incubation temperatures and leatherback hatchling terrestrial performance, as the crawl from the nest to the sea is a critical phase for hatchling survival. Temperature data loggers were placed in 12 leatherback turtle nests on the day they were laid across the early, middle, and late South Florida nesting season. Upon emergence, hatchlings were tested for righting ability and crawling speeds. Mean nest temperatures ranged from 29.0 to 32.5°C and were significantly higher in mid- and late-season nests compared to early-season nests. Hatching and emergence success correlated with temperature, where the mid-season nests were the most successful. Hatchling morphology also correlated with temperature; nests with lower temperatures produced larger hatchlings than nests with hotter temperatures. Righting response scores were significantly lower in hatchlings from late-season, hotter nests, while there was no correlation between crawling speeds and temperature. However, more studies are needed to investigate these relationships since the sample size of this study was relatively small. Our data provide insight into how rising nest temperatures may impact hatchling performance and, in turn, affect their survival.

A machine learning species distribution model for the critically endangered East Pacific leatherback turtle Dermochelys coriacea

The Eastern Pacific population of leatherback turtles Dermochelys coriacea is Critically Endangered, with incidental capture in coastal and pelagic fisheries as one of the major causes. Given the population’s broad geographic range, status, and extensive overlap with fisheries throughout the region, identifying areas of high importance is essential for effective conservation and management. In this study, we created a machine-learning species distribution model trained with remotely sensed environmental data and fishery-dependent leatherback presence (n = 1088) and absence data (>500000 fishing sets with no turtle observations) from industrial and small-scale fisheries that operated in the eastern Pacific Ocean between 1995 and 2020. The data were obtained through a participatory collaboration between the Inter-American Convention for the Protection and Conservation of Sea Turtles and the Inter-American Tropical Tuna Commission as well as non-governmental organizations to support the quantification of leatherback vulnerability to fisheries bycatch. A daily process was applied to predict the probability of leatherback occurrence as a function of dynamic and static environmental covariates. Coastal areas throughout the region were highlighted as important habitats, particularly highly productive feeding areas over the continental shelf of Ecuador, Peru, and offshore from Chile, and breeding areas off Mexico and Central America. Our model served as the basis to quantify leatherback vulnerability to fisheries bycatch and the potential efficacy of conservation and management measures (Griffiths & Wallace et al. 2024; Endang Species Res 53:295-326). In addition, this approach can provide a modeling framework for other data-limited vulnerable populations and species.

An ancestral hard-shelled sea turtle with a mosaic of soft skin and scutes

The transition from terrestrial to marine environments by secondarily aquatic tetrapods necessitates a suite of adaptive changes associated with life in the sea, e.g., the scaleless skin in adult individuals of the extant leatherback turtle. A partial, yet exceptionally preserved hard-shelled (Pan-Cheloniidae) sea turtle with extensive soft-tissue remains, including epidermal scutes and a virtually complete flipper outline, was recently recovered from the Eocene Fur Formation of Denmark. Examination of the fossilized limb tissue revealed an originally soft, wrinkly skin devoid of scales, together with organic residues that contain remnant eumelanin pigment and inferred epidermal transformation products. Notably, this stem cheloniid—unlike its scaly living descendants—combined scaleless limbs with a bony carapace covered in scutes. Our findings show that the adaptive transition to neritic waters by the ancestral pan-chelonioids was more complex than hitherto appreciated, and included at least one evolutionary lineage with a mosaic of integumental features not seen in any living turtle.

The authorship and date of the familial nomen Dermochelyidae (Chelonii)

The nomen of the family Dermochelyidae, with currently a single extant species, Dermochelys coriacea (Vandellius, 1761), has been attributed to different authors. This situation led us to research the sources and information about the various nomina (families, genera and species) concerned in order to review their status, in compliance of the Code, and to solve the problem. The logonymic lists concerning Dermochelyidae, Dermochelys and Dermochelys coriacea are reviewed, corrected and completed. The family nomen must be written as Dermochelyidae Baur, 1888.

Leatherback Sea Turtle (Dermochelys coriacea) Nesting and Health Parameters in St. Kitts, 2003–2016

The St. Kitts Sea Turtle Monitoring Network (SKSTMN) began implementation of a leatherback sea turtle (Dermochelys coriacea) monitoring program in 2003 on the main leatherback nesting beaches on St. Kitts, Keys Beach and North Friars Beach. From March 2003 to July 2016, a total of 2,419 adult female leatherback emergence events were recorded and evaluated. A notable decrease in adult leatherback emergence activity was observed over the course of the study period. The nesting season ranged from February to August. April and May were the months with the highest frequency of nesting. The number of females individually identified (flipper tagging and/or passive integrated transponder) from 2004-2016 was 259 with a mean curved carapace length (CCL) (n=720) of 153 cm and mean curved carapace width (CCW) (n=719) of 113 cm. Remigration intervals ranged from one to five years with a median of two years. Mean clutch frequency for nesting females in St. Kitts over the course of the study period was 3 (standard deviation (SD) 2.9) and during a reproductive season was 2.2 (SD 1.44). Mean total number of eggs laid per nest was 113 with mean number of yolked eggs being 83.5 and yolkless 29.3. The mean incubation period was 59.5 days overall (SD 3.5) with a hatch success overall of 16.75%. Relocated nests had significantly lower hatch success than in situ nests and poaching rates decreased over the course of this study. From 2006-2016 a total of 191 blood samples were collected from 118 individual animals.

The leatherback turtle (Dermochelys coriacea) and plastics in the Northwest Atlantic ocean: A hazard assessment

Atlantic leatherback turtles are faced with multiple threats, such as ship strikes, pollution and predation, throughout their annual migratory routes in the Northwest (NW) Atlantic. The risks associated with encounters with floating and submerged plastic debris are currently unknown. This study is a hazard assessment of plastics for this turtle's sub-population, using 2010–2019 data from the national Great Canadian Shoreline Cleanup (GSCS) program, therefore potential exposure, and published evidence on the interactions of plastics and leatherbacks, hence potential effects. The type of plastic items and their abundance along shorelines of three Atlantic Provinces – Nova Scotia (NS), Prince Edward Island (PEI), Newfoundland and Labrador (NL) – were evaluated and compared to plastic items known to interact with leatherbacks. During the 2010–2019 period, a total of 220,590 plastic items were collected from 578 sites, representing 1264 km of shoreline. Plastic bags and rope are in the top ten most common items found on shorelines of NS, PEI, and NL. Pot gear and trap nets are in the top ten for PEI and are the 14th most common plastic item found on all shorelines. Cigarette debris is also commonly found. From the literature, plastic bags, pot gear and trap nets, and rope are known to adversely affect leatherbacks. Assuming that a large proportion of the shoreline debris comes in from the sea, after being in coastal waters for unknown periods, the study shows that such items pose a hazard to leatherbacks through ingestion and entanglement, based on published studies. Evidence is now needed on actual exposure at sea to the most common items to establish the ecological risk of plastics to these turtles in NW Atlantic waters.

Penanaman Sikap Toleransi Anak Usia Dini dalam Buku Dongeng Binatang Penyelamat Penyu Belimbing

The attitude of tolerance is one of the character education that must be instilled and applied in children. The task of parents and educators in providing understanding and example by planting from an early age. This study examines the book The Tale of the Animal Save the Leatherback Turtle by Titi Anisatul Laely and Mokhamad Nur Zaman from the aspect of tolerance for early childhood. Fairy tale books are one of the interesting media in instilling tolerance in early childhood. The purpose of this study was to analyze the inculcation of tolerance in early childhood in the book Tale of Animals to Save Leatherback Turtles by Titi Anisatul Laely and Mokhamad Nur Zaman. This type of research is descriptive qualitative with a textual analysis approach or library research in the form of literature review. The data source is from the book Fairy Tale of Animals to Save Leatherback Turtles by Titi Anisatul Laely and Mokhamad Nur Zaman. Data collection using documentation. Data analysis was carried out in several ways, namely data reduction, data classification, and verification of data information. The results of the study determine and identify that attitudes or behaviors that reflect the cultivation of an attitude of tolerance are mutual respect, help and accept differences (humble). These three attitudes are attitudes of tolerance that must be instilled from an early age in children, so that children can be accepted in a wider environment and can socialize with others.

Experimental Analysis of Wavelength Preferences Shown by Hatchling Leatherback Sea Turtles (Dermochelys coriacea)

In marine turtles it is well established that the shorter light wavelengths in the visible and near-ultraviolet spectrum provide more potent, and preferred, cues for nocturnal seafinding orientation than the longer light wavelengths. In this study, we simultaneously presented leatherback hatchlings (Dermochelys coriacea) with a short near-ultraviolet (380 nm) and a longer visible (500 nm) light stimulus to determine whether that preference was based upon differences in light intensity, light wavelength, or a combination of both variables. We found that under light conditions mimicking those at the nesting beach on the darkest evenings, the behavioral preference for the shorter light wavelengths was based upon intensity cues, although we speculate that under brighter illumination, wavelength cues might also be utilized.

Dispersal of juvenile leatherback turtles from different Caribbean nesting beaches: A model study

The Northwest Atlantic (NWA) leatherback turtle (Dermochelys coriacea) subpopulation was recently classified as endangered. It nests in the Wider Caribbean Region and includes five genetic stocks, all declining, albeit at different rates. The causes of decline are multiple and difficult to identify based on annual nest counts which integrate the effects of multiple stressors over the entire life history. Demographic models, however, show that survival during the juvenile pelagic stage is the main factor modulating population trends, but this life stage remains largely unobserved. This paper presents a suite of numerical simulations where juveniles from the five NWA stocks disperse under the combined effects of ocean currents and habitat-driven swimming movements. Simulations reveal when and where NWA juveniles likely disperse and, thus, the environmental conditions and anthropogenic threats they may encounter. Simulated individuals initially disperse following either the “Caribbean route,” inside the Caribbean Sea and the Gulf of Mexico (GoM), or the “Atlantic route” east of the Antilles Islands Arc. The percentage of individuals following one or the other route varies markedly with the stock of origin. Late dispersal in the eastern Atlantic Ocean and the Mediterranean Sea is similar in all stocks. Juveniles following the Caribbean route are rapidly entrained northwards by the Gulf Stream and incur a high risk of cold-induced mortality. This mostly affects the Florida stock and the Western Caribbean (WCA) stock nesting in Costa Rica, Panama, and Colombia. The Atlantic route is less lethal as individuals progress more slowly toward higher latitudes. Simulations also show that the percentage of WCA juveniles visiting the GoM is larger than for any other stock. The learned migration goal (LMG) hypothesis, which posits that adult sea turtles tend to exploit foraging areas previously identified at the juvenile stage, may thus explain why WCA adults are overrepresented in the GoM. Finally, our results suggest that the recently observed increase in the percentage of WCA adults migrating into the GoM could be linked to bycatch reduction measures implemented in 2003–2004, combined with an increase in the frequency of Loop Current intrusion and eddy-shedding events that started around the year 2000.

Numerical Study on a Bio-Inspired Micropillar Array Electrode in a Microfluidic Device.

The micropillar array electrode (µAE) has been widely applied in microchip-based electrochemical detection systems due to a large current response. However, it was found that amplifying the current through further adjusting geometrical parameters is generally hindered by the shielding effect. To solve this problem, a bio-inspired micropillar array electrode (bµAE) based on the microfluidic device has been proposed in this study. The inspiration is drawn from the structure of leatherback sea turtles’ mouths. By deforming a μAE to rearrange the micropillars on bilateral sides of the microchannel, the contact area between micropillars and analytes increases, and thus the current is substantially improved. A numerical simulation was then used to characterize the electrochemical performance of bµAEs. The effects of geometrical and hydrodynamic parameters on the current of bµAEs were investigated. Moreover, a prototypical microchip integrated with bµAE was fabricated for detailed electrochemical measurement. The chronoamperometry measurements were conducted to verify the theoretical performance of bµAEs, and the results suggest that the experimental data are in good agreement with those of the simulation model. This work presents a novel bµAE with great potential for highly sensitive electrochemical detection and provides a new perspective on the efficient configuration of the µAE.

Preserving fragile ecosystems from oil spills – An environmental sensitivity assessment of the east coast of Trinidad

Ecosystems remain vulnerable, reducing their resilience without informed planning and management to update oil spill vulnerabilities. An oil spill from an offshore platform was simulated to predict probable oil landing zones off the east coast of Trinidad. Climate, land use, and sedimentation were used to classify the east coast of Trinidad and to identify the geomorphic features that are most susceptible to oil spills. In ArcGIS, physical and biological resources were used to modify NOAA's estuarine classification and build an environmental sensitivity index (ESI) map representing wet and dry seasonal changes. Leatherback sea turtle nesting sites are highly vulnerable; thus, the shoreline classification reflects this. This research identified six intertidal ecosystem indices along the east coast of Trinidad, namely ESI-1, ESI-3, ESI-4, ESI-6 and ESI-10. Mangroves were considered the most sensitive habitat, whereas high wave energy locations were ranked the lowest. This study provides first responders and environmental officials with a methodological approach to determine the locations and areas most vulnerable and develop appropriate response and cleanup strategies/plans before the oil reaches land.

HEMATOLOGICAL VALUES IN THE LEATHERBACK SEA TURTLE DERMOCHELYS CORIACEA FOUND AT BARRA DELA CRUZ BEACH, OAXACA, MÉXICO

In the months of December and January of the nesting 2013 season 2014 were copies of leatherback turtles (Dermochelys coriacea) on the beach bar de la Cruz, Oaxaca to determine the correlation between the biometric measures curved carapace length and values of hematological, between these and the curved carapace width and Hematological values and the State of deterioration of each female. Were punctures in breast cervical dorsal half of spawning, when females were completely immobile [1]; 8 females, four altered blood samples were obtained (presence of barnacles, fungi and barnacle) and four not altered. We found seven blood cells in all turtles, varying according to the alteration. In not altered turtles were 10 783 erythrocytes values; 2 043 heterophile; 6 576 monocytes; 5 802 basophils; 2 010 azurophilic; trombocito 9 090 and lymphocyte 1 148, while in the altered: 2 622 erythrocytes; 1 077 heterophile; 1 557 monocytes; basophil 3 080; 1 927 azurophilic; thrombocytes 309 5 and 1 773 lymphocyte. Through the analysis of linear correlation was determined that organisms which presented alterations had fewer blood cells, which had no physical changes were greater number of blood cells and there is no correlation between the curved carapace width and the number of blood cells.

EVOLUTIONARY HISTORY OF THE APEX1 GENE: FROM VERTEBRATES TO SICKLE CELL ANEMIA

In sickle cell anemia, it is known that the APEX1 gene, which encodes the APE1 protein, plays several roles, including DNA strand repair and redox functions, and it is highly expressed during the inflammatory process. The present study sought to investigate how conserved the APEX1 gene is in vertebrates. For this, the coding sequences of the APEX1 gene were obtained by searching genomic databases at the NCBI, with 14 sequences ( Pan troglodytes, Macaca mulatta, Homo sapiens, Bos taurus, Cervos elaphaus, Gallus gallus, Lagopus muta, Petromyson marinus, Felis catus, Rattus norvengicus, Alosa alosa, Dermochelys coriacea, Caretta caretta, Trachemys scriptaelegans) being chosen, using up to 300 amino acids as a selection criterion. After the sequences of the species were aligned using MAFFT v7.407 software, the quality of the sequences was verified and the aligned regions without divergence information were removed using Gblocks. Following this, phylogenetic trees were constructed using the MEGA-X software using the Maximum Likelihood method with 1,000 bootstraps. The generated phylogenies were edited using the FigTree version 1.44 program. A similarity in gene conservation has been observed in Primate species ( Pan troglodytes, Macaca mulatta , and Homo sapiens ). There was a grouping in the same clade of the species, Bos taurus and Cervus elaphus ; the same happened with the order Galliforme ( Gallus gallus and Lagopus muta ) and among the studied reptile species. The vertebrate that presented the least evolutionarily conserved gene was the marine lamprey ( Petromyson marinus) . According to the findings, APEX1 is linked to the oxidative stress pathway in diseases such as sickle cell anemia, preventing further oxidative damage and regulating transcription factors involved in the redox process. Interesting to note is the existence of sicklings of erythrocytes in deer; however, the genetic basis of the phenomenon is still unknown. It is, however, evident that sickling and the APEX1 gene may be related in an adaptive manner. There was a genetic distance of seventy for the APEX1 gene in Felis catus , which suggests that the presence of sickle erythrocytes is not related to the type of hemoglobin since feline hemoglobin contains six additional sulfhydryl groups compared to human hemoglobin. As for reptiles, grouped into a single clade, it is known that they may have sickled erythrocytes, however, unlike Primates, these are nucleated. Unlike the other groups, the capillary diameter in reptiles is greater, which in turn could favor a decrease in vaso-occlusive processes. The inflammatory process in vertebrates is accompanied by a series of cellular and molecular mechanisms that can trigger different costs, which are optimized by the forces of natural selection. The sickling of erythrocytes, which can culminate in inflammatory events, is common in some groups of the animal kingdom. It increases the expression of the APEX1 gene, which has been shown to be evolutionarily more conserved in animals with similar erythrocyte sickling mechanisms, suggesting that it has evolved convergently to protect against oxidative stress.

Historical Records of Loggerhead Sea Turtle (Caretta caretta) Nesting at Tortuguero, Costa Rica

Costa Rica is considered a hot spot for biodiversity and wildlife conservation in Central America, and sea turtles are a good example of this. Largely distributed along both the Caribbean and Pacific coast, adult females of five of the seven extant sea turtle species select beaches on both coasts as their breeding sites. Although Green Sea Turtles (Chelonia mydas), Leatherback Sea Turtles (Dermochelys coriacea), Hawksbill Sea Turtles (Eretmochelys imbricata), and Olive Ridley Sea Turtles (Lepidochelys olivacea) have been extensively studied in Costa Rica, little information regarding Loggerhead Sea Turtles (Caretta caretta) is available. Thus, we present an exhaustive data record of every Loggerhead encountered at Tortuguero beach (northeastern Caribbean coast of Costa Rica) over the past 60 yr. We collected Loggerhead nesting data between 1957 and 2021 through daytime and nocturnal monitoring activities. We documented 14 Loggerhead Sea Turtle nesting attempts between 1957 and 2021 at Tortuguero. Among them, seven nested successfully, four did not lay eggs, and one's fate is unknown. Additionally, two turtles were killed by jaguars. Mean minimum curve carapace length (CCLmin) measurements for Loggerheads was 98.2 ± 3.7 cm (range, 90.0–101.4 cm). Finally, we found that every encounter occurred between April and July, which coincides with the Loggerhead nesting season in the Northwest Atlantic. Our study is the first assessment of Loggerhead Sea Turtles nesting in Costa Rica, bringing to light new records for this species in the Caribbean Sea.

Effect of water temperature on the duration of the internesting interval across sea turtle species

Sea turtles generally lay several clutches of eggs in a single nesting season. While a negative correlation between water temperatures and the time required between constitutive nesting events (termed the internesting interval) has been previously reported in loggerhead Caretta caretta and green turtles Chelonia mydas, it is not understood whether this relationship remains constant across other sea turtle species. Here, we expanded upon these previous studies on loggerhead and green turtles by using larger sample sizes and including data from species with a wider range of body-sizes; specifically: hawksbill Eretmochelys imbricata, leatherback Dermochelys coriacea, and olive ridley turtles Lepidochelys olivacea. In total, we compiled temperature data from biologgers deployed over internesting intervals on 23 loggerhead, 22 green, 7 hawksbill, 26 leatherback and 11 olive ridley turtles from nesting sites in 8 different countries. The relationship between the duration of the internesting interval and water temperatures in green and loggerhead turtles were statistically similar yet it differed between all other turtle species. Specifically, hawksbill turtles had much longer internesting intervals than green or loggerhead turtles even after controlling for temperature. In addition, both olive ridley and leatherback turtles exhibited thermal independence of internesting intervals presumably due to the large body-size of leatherback turtles and the unique capacity of ridley turtles to delay oviposition. The observed interspecific differences in the relationship between the length of the internesting interval and water temperatures indicate the complex and variable responses that each sea turtle species may exhibit due to environmental fluctuations and climate change.

Responses of three nesting sea turtle species to hard-armoring structures

In the face of modern challenges, analyzing sea turtle nesting trends is critical to better understand impacts to these vulnerable species. The introduction of hard-armoring structures (e.g., seawalls, rock revetments) on sea turtle nesting beaches poses a threat to nesting leatherback (Dermochelys coriacea), loggerhead (Caretta caretta), and green (Chelonia mydas) sea turtles due to habitat loss and turtle interactions with the physical structure. Despite much of Florida’s coastline being protected by some form of hard-armoring technology, research on the impacts of these structures to sea turtles is limited to loggerheads. Our objectives were to (1) examine nest density, nesting success, washout rates, and hatching and emergence success at hard-armoring sites in comparison to a control area and (2) characterize impacts of obstructions encountered by sea turtles nesting in northern Palm Beach County, Florida. Our results indicate that the hard-armoring site showed significantly lower nest density for green turtles and nesting success for loggerheads and green turtles in comparison to a control area. Additionally, nesting success for loggerheads and green turtles that encountered hard-armoring structures was significantly lower in comparison to those that encountered no obstructions or other obstructions (e.g., beach furniture, walkovers, escarpments, etc.). These results suggest that hard-armoring structures negatively impact sea turtle nesting behavior, which could result in loss of energy or other physiological derangements. Green turtles showed the most significant differences between the two sites, likely a result of their typical nest site selection favoring the upper portions of the beach, crawling further distances from the high-water line than loggerheads or leatherbacks. Before additional hard-armoring structures are permitted and installed, governing agencies should first consider more natural methods of protecting shorelines (e.g., dune restoration).

Genetic Diversity in Leatherback Turtles (Dermochelys coriacea) along the Andaman Sea of Thailand

The leatherback sea turtle (Dermochelys coriacea) is the largest and one of the most migratory turtle species, inhabiting oceans throughout the world. There has been a steady decline in leatherback populations over the past several decades due to human activities. They are considered endangered in Thailand and global, so conservation strategies are needed to study and protect the species, including determining their genetic diversity. A total of 8 microsatellite loci and 658 bp amplicon of mitochondrial DNA (mtDNA) were used to assess genetic data from 149 dead leatherback turtle hatchlings among 14 nests in five locations along the Andaman Sea, Thailand, between 2018–2020. The microsatellite findings show that the observed heterozygosity (Ho) ranged from 0.44 ± 0.09 to 0.65 ± 0.10. Population structures were further divided into two genetically distinct groups by Bayesian inference. For the mtDNA control region, our samples consisted of three haplotypes. Globally, there are 27 haplotypes of leatherback turtles, with a relatively low genetic diversity (h = 0.43). These results reveal the genetic status of leatherback turtles in Thailand and globally, and raise concerns about their relative genetic health, which highlight the need for proactive, long-term management and conservation strategies for this endangered species.

Method Comparison of β-Hydroxybutyrate Using a Point-of-Care Device and Dry Chemistry Analyzer in Three Sea Turtle Species.

The ketone β-hydroxybutyrate (BHB) serves as an energy source when bodily energy stores are low. Concentrations of this blood analyte are often determined by spectrophotometric quantitative assays with a dry chemistry analyzer; however, rapid assessment with point-of-care devices have the potential to improve assessment of animals in the field or in clinical settings. We measured BHB concentrations in whole blood samples from 54 leatherback (Dermochelys coriacea), 27 loggerhead (Caretta caretta), and 14 green (Chelonia mydas) sea turtles in Florida, US with a point-of-care device and validated its use with corresponding plasma samples and dry chemistry analyzer as the gold standard. Concentrations of BHB highly correlated between the two methods for all three species, with loggerheads showing the best agreement and lowest bias. Therefore, the point-of-care device used for this study (Lucidplus β-ketone monitoring system) is probably appropriate for sea turtle BHB measurements.

Genetic monitoring of the critically endangered leatherback turtle (Dermochelys coriacea) in the South West Atlantic

Although leatherback turtles (Dermochelys coriacea) are highly migratory and have a wide oceanic distribution, the South West Atlantic (SWA) subpopulation comprises few reproductive females and is listed as Critically Endangered. Herein, we present temporal genetic assessment of the poorly known subpopulation of the D. coriacea from SWA subpopulation. A total of 39 leatherback adult individuals were sampled during seven reproduction seasons along 160 km in the main nesting area in Brazil and analysed using D-loop mtDNA sequences (N = 37) and 25 microsatellite loci (N = 29). We detected genetic differences in temporal mtDNA analysis, possible explained by genetic drift. We also found two different genetic clusters with admixture between them for SWA subpopulation, indicating possible gene flow between different nesting areas. The SWA subpopulation presented low mean number of different alleles, moderate levels of observed and expected heterozygosities and lack of inbreeding. This pattern is possibly the consequence of an important amount of breeding occurrence abroad SWA nesting beach adjacencies, mating behaviours (such as polyandry and/or polygyny), and also some degree of inbreeding avoidance among reproductive individuals. The low remigration rates estimated for SWA subpopulation is possibly related to the high mortality rates at seas. A more comprehensive analysis on the patterns of genetic diversity, operational sex ratios, and inbreeding avoidance could help to inform about population resiliency and better understand the reproductive behaviour to perform recovery strategies and efficiently act to prevent the extinction of this isolated and remarkably threatened leatherback subpopulation from the Atlantic Ocean.

Missing Data in Sea Turtle Population Monitoring: A Bayesian Statistical Framework Accounting for Incomplete Sampling

Monitoring how populations respond to sustained conservation measures is essential to detect changes in their population status and determine the effectiveness of any interventions. In the case of sea turtles, their populations are difficult to assess because of their complicated life histories. Ground-derived clutch counts are most often used as an index of population size for sea turtles; however, data are often incomplete with varying sampling intensity within and among sites and seasons. To address these issues, we: (1) develop a Bayesian statistical modelling framework that can be used to account for sampling uncertainties in a robust probabilistic manner within a given site and season; and (2) apply this to a previously unpublished long-term sea turtle dataset (n = 17 years) collated for the Republic of the Congo, which hosts two sympatrically nesting species of sea turtle (leatherback turtle [Dermochelys coriacea] and olive ridley turtle [Lepidochelys olivacea]). The results of this analysis suggest that leatherback turtle nesting levels dropped initially and then settled into quasi-cyclical levels of interannual variability, with an average of 573 (mean, 95% prediction interval: 554–626) clutches laid annually between 2012 and 2017. In contrast, nesting abundance for olive ridley turtles has increased more recently, with an average of 1,087 (mean, 95% prediction interval: 1,057–1,153) clutches laid annually between 2012 and 2017. These findings highlight the regional and global importance of this rookery with the Republic of the Congo, hosting the second largest documented populations of olive ridley and the third largest for leatherback turtles in Central Africa; and the fourth largest non-arribada olive ridley rookery globally. Furthermore, whilst the results show that Congo’s single marine and coastal national park provides protection for over half of sea turtle clutches laid in the country, there is scope for further protection along the coast. Although large parts of the African coastline remain to be adequately monitored, the modelling approach used here will be invaluable to inform future status assessments for sea turtles given that most datasets are temporally and spatially fragmented.