Marc Girondot

University of Paris-Saclay · Life Sciences

Accurate scientific information is critical for undertaking appropriate conservation and management practices for imperiled species. One source of concern is that research findings might vary for non-biological reasons, including experimental design and analytical methods. To illustrate, we provide detailed modern analysis of reproductive data for...

Marine turtles are iconic, globally distributed large reptiles with a largely oceanic life history that makes it difficult to characterize population demography and dynamics. This is significant because all marine turtle species are currently considered vulnerable or endangered. Knowledge of the age of individuals is central to our understanding of...

Incidental capture of non-target species poses a pervasive threat to many marine species, with sometimes devastating consequences for both fisheries and conservation efforts. Because of the well-known importance of vocalizations in cetaceans, acoustic deterrents have been extensively used for these species. In contrast, acoustic communication for s...

Ever since the discovery of temperature-sensitive sex determination (TSD), research has been hindered by scientists' inability to estimate hatchling sex ratios using nonlethal methods, because the sacrifice of embryos is inconceivable in species that we wish to protect. But numerous methods have been attempted. Typically, average incubation tempera...

The loggerhead turtle Caretta caretta is a large marine turtle with a cosmopolitan repartition in warm and temperate waters of the planet. The South Pacific subpopulation is classified as ’Critically Endangered’ on the IUCN Red List, based on the estimated demographic decline. This precarious situation engages an urgent need to monitor nesting popu...

The seasonality of egg-laying in marine turtles is a well-known phenomenon that has been used to determine population trends based on an integration of the number of female emergences or nests during a season. However, in some cases, several peaks in female emergences are detected during single year. In this paper, we explore three such situations,...

Incidental capture of non-target species poses a pervasive threat to many marine species, with sometimes devastating consequences for both fisheries and conservation efforts. Because of the well-known importance of vocalizations in cetaceans, acoustic deterrents have been extensively used for these species. In contrast, acoustic communication for s...

Estimating demographic parameters is key for unraveling the mechanisms governing the population dynamics of species of conservation concern. Endangered green sea turtles navigate vast geographical ranges during their life cycle and face various pressures in coastal areas, especially during their juvenile life-stage. Here, we investigated survival,...

An adult female Lepidochelys kempii was found trapped in drifting sargassum south of Martinique; this is the southernmost report of this taxon in the Lesser Antilles arc. Determining the limits of distribution and the existence of possible sympatry between L. kempii and L. olivacea in certain subregions of the Caribbean has been hindered by numerou...

Sea turtles are vulnerable to climate change since their reproductive output is influenced by incubating temperatures, with warmer temperatures causing lower hatching success and increased feminization of embryos. Their ability to cope with projected increases in ambient temperatures will depend on their capacity to adapt to shifts in climatic regi...

The Guatemalan strategy for sea turtle conservation was defined by the National Council of Protected Areas (CONAP) in 1989. Hatcheries lie at the core of this strategy: egg collectors are allowed to deliver 20% of a nest to a hatchery in exchange for selling or eating the remaining eggs. Consequently, nearly 100% of nests are collected, with no nes...

Reptiles represent one of the most diverse groups of tetrapod vertebrates. Extant representatives of reptiles include lepidosaurs (lizards), testudines (turtles) and archosaurs (crocodiles and birds). In particular, they show an important locomotor diversity with bipedal, quadrupedal and facultatively bipedal taxa. This diversity is accompanied by...

Yalimapo beach, near the Maroni River estuary in French Guiana, is an important turtle nesting site. The interaction of massive mud banks migrating alongshore from the distant Amazon River with discharge from the Maroni River generates strong beach morpho-sedimentary changes. The eventual degradation of the marine turtle nesting habitats resulting...

The green turtle Chelonia mydas is a large marine turtle present in tropical and subtropical seas of the Atlantic, Pacific and Indian Oceans. It is categorized as Endangered on the IUCN Red List based on the trend of nesting populations at 32 sites, of which only three are in the Pacific Ocean. New Caledonia is a sui generis overseas territory of F...

Reptiles represent one of the most diverse groups of tetrapod vertebrates. Extant representatives of reptiles include lepidosaurs (lizards), testudines (turtles) and archosaurs (crocodiles and birds). In particular, they show an important locomotor diversity with bipedal, quadrupedal and facultatively bipedal taxa. This diversity is accompanied by...

The distribution of the sum of negative binomial random variables has a special role in insurance mathematics, actuarial sciences, and ecology. Two methods to estimate this distribution have been published: a finite-sum exact expression and a series expression by convolution. We compare both methods, as well as a new normalized saddlepoint approxim...

Mammals have an evolutionary history spanning hundreds of millions of years. Today, mammals represent one of the most diverse groups of tetrapod vertebrates. In particular, they present a great postural diversity. The humerus adopts different positions: small mammals have a “crouched” posture with a quasi-horizontal humerus, while in the largest sp...

The water‐to‐land transition by the first tetrapod vertebrates represents a key stage in their evolution. Selection pressures exerted by this new environment on animals led to the emergence of new locomotor and postural strategies that favoured access to different ecological niches and contributed to their evolutionary success. Today, amniotes show...

Reproductive seasonality is present across species and phyla. Many species retain seasonal patterns even in tropical regions where climatic variations may be less apparent. Environmental features and large-scale environmental cues play a role in species seasonality and can have major effects on reproductive success. In organisms that present enviro...

The olive ridley sea turtle Lepidochelys olivacea is the most abundant marine turtle species in Guatemala, representing > 99% of all nests. Along with other marine turtles, they are important both culturally and ecologically. Conservation efforts rely almost exclusively on an informal system whereby local residents can harvest olive ridley sea turt...

One recurring difficulty in ecotoxicological studies is that a substantial portion of concentrations are below the limits of detection established by analytical laboratories. This results in censored distributions in which concentrations of some samples are only known to be below a threshold. The currently available methods have several limitations...

Environmental policies, including the European Marine Strategy Framework Directive (MSFD), generally rely on the measurement of indicators to assess the good environmental status (GES) and ensure the protection of marine ecosystems. However, depending on available scientific knowledge and monitoring programs in place, quantitative GES assessments a...

Species with temperature-dependent sex determination (TSD) can experience biased sex ratios in natural conditions , which raises questions the vulnerability of populations in the face of climate change. Studies addressing the adaptive significance TSD have been hampered by the difficulty of accurately estimating sex ratios under natural incubation...

We are pleased to have contributed to the newly released State of the World’s Sea Turtles (SWOT) Report, vol. XVII

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 a...

Fibropapillomatosis (FP) threatens the survival of green turtle (Chelonia mydas) populations at a global scale, and human activities are regularly pointed as causes of high FP prevalence. However, the association of ecological factors with the disease's severity in complex coastal systems has not been well established and requires further studies....

The genome size of five Rhodnius species ( R. milesi, R. nasutus, R. neivai, R. prolixus, and R. robustus ) and two Psammolestes species ( P. coroedes and P. tertius ) were estimated using flow cytometry and/or k-mer distributions in genome sequences. Phylogenetic generalized linear mixed models highlighted significant genome size variations among...

Marine herbivores face rapid changes in the coastal ecosystems where they forage. In the Caribbean, the recent and fast expansion of the invasive phanerogam species Halophila stipulacea is threatening native seagrass ecosystems. So far, H. stipulacea is escaping most Caribbean herbivores, certainly because of its recent introduction or lower nutrit...

Bone sections have been widely used for over a century to assess life history traits of extant and extinct vertebrates, and they remain extremely useful. The charac- terization of their geometric and microanatomical properties forms the core of many descriptive and inferential studies. Bone compactness in particular has been associated with various...

In marine turtles, sex is determined during a precise period during incubation: males are produced at lower temperatures and females at higher temperatures, a phenomenon called temperature-dependent sex determination. Nest temperature depends on many factors, including solar radiation. Albedo is the measure of the proportion of reflected solar radi...

Sea turtles are marine species that are generally in danger of extinction. The conservation strategies in the different countries are attempting to preserve these species and should be constantly updating their policies according to research results taking place on site. The most abundant and frequent species of sea turtle that nest in the Pacific...

Leatherback marine turtles are the largest extant turtles with some individuals meas- uring up to 2 m in carapace length. In addition, this species remains in oceanic habi- tat during much its life, making it difficult to investigate its ontogeny from hatchling to adult stage. Furthermore, distinct chondro-osseous (cartilage and bone) tissue morpho...

Determination of sexual size dimorphism (SSD) in marine turtles is challenging because females are observed on nesting beaches, while males remain at sea and are rarely encountered. Data obtained from a sea turtle bycatch survey and a nesting monitoring program conducted in the same area in the Republic of the Congo give access to the body size of...

This study reports the largest inorganic elements database in the blood of live marine turtles (Lepidochelys olivacea), with 241 live as well as 38 dead nesting turtles sampled and analyzed for 26 inorganic elements, including essential (Al, As, B, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Se, S, V, and Zn) and non-essential elements (Cd, Li, P...

Movement ecology studies are essential to protect highly mobile threatened species such as the green turtle (Chelonia mydas), classified as an endangered species by the IUCN. In 2019, the South Atlantic subpopulation has been downlisted to ‘Least Concern’, but the maintenance of this status strongly relies on the pursuit of research and conservatio...

Beach protection and monitoring has been used for about half a century to multiple rookeries globally as an effective sea turtle conservation strategy with successful population recovery at some. Loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) turtles nesting in South Africa have been continuously protected and monitored since 1...

Sea turtles have temperature-dependent sex determination, with males being produced at low incubation temperatures and females at high temperatures within the thermal range for embryonic development. In the context of climate change, there are concerns that warming temperatures will lead to an increase in female production. If primary sex ratios ar...

Supplemental Information for "Production of male hatchlings at a remote South Pacific green sea turtle rookery: conservation implications in a female-dominated world'.

Leatherback turtles (Dermochelys coriacea) are the largest extant marine turtle, with some individuals measuring more than 1.80 m carapace length. Given the exceptional size of this species and that females only return to land every few years to nest, it is difficult to investigate its ontogeny from hatchling to adulthood. Distinct chondroosseous (...

Temperature-dependent sex determination, or TSD, is a widespread phenomenon in reptiles. The shape of the relationship between constant incubation temperature and sex ratio defines the TSD pattern. The TSD pattern is considered a life-history parameter important for conservation because the wider the range of temperatures producing both sexes, the...

In marine turtles, incubation begins when females lay eggs on sandy beaches. Emergence of newborns from the sand marks the conclusion of a much longer process. At the end of incubation, the amnion ruptures inside the egg, and the chorioallantois moves posterior to the embryo to reveal the head and forelimbs, thus freeing the embryo to pip the shell...

In the context of global change, endangered species such as sea turtles undergo strong population dynamics changes. Understanding demographic processes inducing such changes is critical for developing appropriate measures for conservation and management. Nesting females of the French Guiana population of leatherback sea turtles Dermochelys coriacea...

The change of animal biometrics (body mass and body size) can reveal important information about their living environment as well as determine the survival potential and reproductive success of individuals and thus the persistence of populations. However, weighing individuals like marine turtles in the field presents important logistical difficulti...

In the eastern Pacific, peak olive ridley sea turtle (Lepidochelys olivacea) nesting occurs during the warmest months which coincide with the rainy season, yet as nesting takes place year-round, the small proportion of the nests laid during dry-low season are exposed to contrasting environmental conditions. Most of the studies on Pacific coast sea...

Phenological shifts, by initiating reproductive events earlier, in response to advanced seasonal warming is one of the most striking effects currently observed in wild populations. For sea turtles, phenological adjustment to warming conditions could be the most effective short-term adaptation option against climate change. We calculated future phen...

Climate change affects the spatial distribution and timing of seasonal events (i.e. phenology) of species. The phenology of ectotherms, such as sea turtles, is strongly influenced by rising temperatures associated with climate change, since most of their life history traits are dependent on temperature. Most studies on the phenology of sea turtles...

Capture–mark–recapture studies that fail to account for the frequency and dynamics of marker loss risk generating biased demographic estimates. In this study, we used permanent multilocus genotypes (i.e., “genetic tags”) and a new enhanced tag loss model to quantify the tag loss dynamics for both passive integrated transponder (PIT) and Inconel met...

Afin de mieux comprendre les interactions existantes entre les espèces marines et leurs habitats, nous étudions depuis quelques années l’écologie trophique et fonctionnelle de la tortue verte Chelonia mydas. L’objectif de cette étude est de définir le rôle de cette espèce menacée dans la dynamique des écosystèmes marins et sa capacité à s’adapter a...

Tagging and counting are central activities for many marine turtle organizations, even if sometimes the exact goal is not well defined. Even when it is clearly defined, the methodology to analyze data is not straightforward and requires good statistical capacities. In the view to help organizations facing such a problem, I have developed a R packag...

A hundred nesting olive ridley turtles were sampled to determine biochemical parameters (ALP, AST, ALT, creatinine, albumin, cholesterol, glucose, proteins, triglycerides, urea, and P-nitrophenyl acetate esterase activity). Esterase activity (EA) is a new biomarker very sensitive to metals. Most of the samples showed detectable levels. We also anal...

During the 5 th Workshop about Temperature-Dependent Sex Determination held in the 38 th International Sea Turtles Symposium (16-22 February 2018) in Kobe, Japan, we discussed the uncertainty of temperatures recorded by data logger and their calibration. We report here an extension of this discussion. First, we propose a way to estimate the uncerta...

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The intrinsic variability associated with virtually all measurements in biology or ecotoxicology leads researchers to perform statistical tests to assess the robustness of their results. It will be published all the more easily and in a better journal that the statistical tests will give a significant result. If not, there is of course the possibil...

The Olive Ridley marine turtle (Lepidochelys olivacea) is characterized by individual morphological variability in the number and shape of scutes. The influence of pollutants on developmental instability and one of its consequences, the asymmetry of individuals, has been demonstrated in several species, especially invertebrates and some birds. Howe...

Reproducibility is central in science and statistics are one of the tool used to ensure that conclusions are supported by data. However, high false positive rate is a common problem denounced regularly when hypotheses testing using null and alternative hypotheses are used. The origin of this high false positive rate is deeply anchored in the method...

France’s 12 overseas regions and territories range across all of the Earth’s temperate, tropical, and polar seas, with a combined marine territory of nearly 10.2 million square kilometers (nearly 4 million square miles), an area larger than the mainland United States. Marine turtles are found throughout most French waters; indeed, it is easier to l...

Due to their longevity and extensive migration areas, marine turtles are able to accumulate diverse contaminants over many years and as a consequence they represent an interesting bioindicator species for marine ecosystem pollution. Metals provoke toxicological effects in many aquatic animal species, but marine turtles have been under-investigated...

The sexual phenotype of the gonad is dependent on incubation temperature in many turtles, all crocodilians, and some lepidosaurians. At hatching, identification of sexual phenotype is impossible without sacrificing the neonates. For this reason, a general method to infer sexual phenotype from incubation temperatures is needed. Temperature influence...

Olive ridleys (Lepidochelys olivacea) and loggerheads (Caretta caretta) are two closely phylogenetically related sea turtles that nest in very different thermal habitat. Olive ridleys nest in pan-tropical beaches whereas loggerheads nest in more temperate beaches. In the context of climate change, the temperature in temperate beaches will increase...

Ectothermic species are strongly affected by thermal changes. To assess the viability of these species under climate change constraints, we need to quantify the sensitivity of their life history traits to temperature. The loggerhead marine turtle (Caretta caretta) nests regularly in the Oriental Basin of the Mediterranean Sea. The different populat...

Temperature-dependent sex determination (TSD) is a kind of sex determination in which gonadal sex is dependent on the incubation temperature of the eggs. Within reptiles, TSD occurs in many turtles, all crocodilians, the tuataras and some lizards. The European Pond Turtle, Emys orbicularis, has been the most studied species for TSD, and the biochem...

Due to their bioaccumulation and biomagnification pathways, inorganic elements can accumulate in high-level aquatic organisms in the food web. Then, this species can be used to monitor the quality of the environment. Blood concentration of nine inorganic elements, including possible toxic metals (An, Cu, Mn, Se, As, Ni, Cd, Pb, and Hg), in 20 males...

Knowledge of the sex ratio of a population is crucial to understand their structure and dynamics. For species, such as marine turtles, with temperature-dependent sex determination, this knowledge provides a baseline in advance of climate change. Determining the primary sex ratio for marine turtle populations is challenging since offspring lack sexu...

Inorganic elements (Pb, Cd, Hg, Al, As, Cr, Cu, Fe, Mn, Ni, Se and Zn) are present globally in aquatic systems and their potential transfer to marine turtles can be a serious threat to their health status. The environmental fate of these contaminants may be traced by the analysis of turtle tissues. Loggerhead turtles (Caretta caretta) are the most...