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opencc-zeroNov 2020View details →

Changes in dive patterns of leatherback turtles with sea surface temperature and potential foraging habitats

Marine mesotherms are able to occupy broader thermal niches than ectotherms; however, this means they must exhibit greater tolerance to diverse environmental conditions across the ocean. Knowledge remains limited about how differences in environmental conditions within occupied habitats affect the bioenergetics of mesotherms and associated ecological traits. Here, we report that leatherback turtles (Dermochelys coriacea) migrating across the North Pacific changed their dive behavior regionally, possibly in response to changes in sea surface temperature and prey abundance. Our results demonstrate that dives became deeper when the surface water was warmer, presumably because leatherbacks dive to deep cold waters to avoid overheating. Moreover, the patterns of presumed foraging dives indicate that leatherbacks engage in behavioral thermoregulation in warmer foraging regions, which perhaps limit the time available for foraging activity. In contrast, mesothermy allows leatherbacks to spend more time foraging in cool-temperate regions. However, it might not produce greater reproductive output due to additional migration cost to these areas, which are more distant from their nesting beaches. Our results highlight that mesothermy might not provide a direct fitness advantage to all individual leatherback turtles; rather, it affords a species-level fitness advantage by allowing a greater diversity of habitats to be utilized.

opencc-zeroJul 2021View details →

Data from: Large-scale connectivity, cryptic population structure, and relatedness in Eastern Pacific olive ridley sea turtles (Lepidochelys olivacea)

Endangered species are grouped into genetically discrete populations to direct conservation efforts. Mitochondrial Control Region (mtCR) haplotypes are used to elucidate deep divergences between populations, as compared to nuclear microsatellites that can detect recent structuring. When prior populations are unknown, it is useful to subject microsatellite data to clustering and/or ordination population inference. Olive ridley sea turtles (Lepidochelys olivacea) are the most abundant sea turtle, yet few studies have characterized olive ridley population structure. Recently, clustering results of olive ridleys in the Eastern Tropical Pacific Ocean suggested weak structuring (FST=0.02) between Mexico and Central America. We analyzed mtCR haplotypes, new microsatellite genotypes from Costa Rica, and pre-existing microsatellite genotypes from olive ridleys across the Eastern Tropical Pacific, to further explore population structuring in this region. We subjected inferred populations to multiple analyses to explore the mechanisms behind their structuring. We found 10 mtCR haplotypes from 60 turtles nesting at three sites in Costa Rica, but did not detect divergence between Costa Rican sites, or between Central America and Mexico. In Costa Rica, clustering suggested one population with no structuring, but ordination suggested four cryptic clusters with moderate structuring (FST=0.08, p<0.001). Across the Eastern Tropical Pacific, ordination suggested nine cryptic clusters with moderate structuring (FST=0.103, p<0.001) that largely corresponded to Mexican and Central American populations. All ordination clusters displayed significant internal relatedness relative to global relatedness (p<0.001) and contained numerous sibling pairs. This suggests that broadly dispersed family lineages have proliferated in Eastern Tropical Pacific olive ridleys and corroborates previous work showing basin-wide connectivity and shallow population structure in this region. The existence of broadly dispersed kin in Eastern Tropical Pacific olive ridleys has implications for management of olive ridleys in this region, and adds to our understanding of sea turtle ecology and life-history, particularly in light of the natal-homing paradigm.

opencc-zeroJan 2021View details →

First Atlantic satellite tracks of lost years green turtles support the importance of the Sargasso Sea as a sea turtle nursery

In-water behaviour and long-term movements of oceanic-stage juvenile sea turtles are not well described or quantified. This is due to technological or logistical limitations of tracking small, fast-growing animals across long distances and time-periods within marine habitats. Here we present the first long-term offshore tracks of oceanic green turtles (Chelonia mydas) in western North Atlantic waters. Using a tag attachment technique developed specifically for young (<1 year old) green turtles, we satellite tracked 21 oceanic-stage green turtles (<19 cm straight carapace length) up to 152 days using small, solar-powered transmitters. We verify that oceanic-stage green turtles: (i) travel to and remain within oceanic waters; (ii) often depart the Gulf Stream and North Atlantic Subtropical Gyre currents, orienting toward waters associated with the Sargasso Sea; (iii) remain at the sea surface, using thermally-beneficial habitats that promote growth and survival of young turtles; and (iv) green turtles orient differently compared to same stage loggerhead turtles (Caretta caretta). Combined with satellite tracks of oceanic-stage loggerhead turtles, our work identifies the Sargasso Sea as an important nursery habitat for North Atlantic sea turtles, supporting a growing body of research that suggests oceanic-stage sea turtles are behaviourally more complex than previously assumed.

opencc-zeroDec 2016View details →

Data from: Loggerhead sea turtle embryos (Caretta caretta) regulate expression of stress-response and developmental genes when exposed to a biologically realistic heat stress

Oviparous reptile embryos are expected to breach their critical thermal maxima if temperatures reach those predicted under current climate change models due to the lack the maternal buffering processes and parental care. Heat shock proteins (HSPs) are integral in the molecular response to thermal stress, and their expression is heritable, but the roles of other candidate families such as the heat shock factors (HSFs) have not been determined in reptiles. Here we subject embryonic sea turtles (Caretta caretta) to a biologically realistic thermal stress and employ de novo transcriptomic profiling of brain tissue to investigate the underlying molecular response. From a reference transcriptome of 302,293 transcripts, 179 were identified as differentially expressed between treatments. As anticipated, genes enriched in the heat shock treatment were primarily associated with the Hsp families, or were genes whose products play similar protein editing and chaperone functions (e.g. bag3, MYOC and serpinh1). Unexpectedly, genes encoding the HSFs were not significantly upregulated under thermal stress, indicating their presence in unstressed cells in an inactive state. Genes that were downregulated under thermal stress were less well functionally defined but were associated with stress response, development, and cellular organization, suggesting that developmental processes may be compromised at realistically high temperatures. These results confirm that genes from the Hsp families play vital roles in the thermal tolerance of developing reptile embryos, and in addition with a number of other genes, should be targets for evaluating the capacity of oviparous reptiles to respond adaptively to the effects of climate change.

opencc-zeroDec 2015View details →

Data from: The anti-predator role of within-nest emergence synchrony in sea turtle hatchlings

Group formation is a common behaviour among prey species. In egg-laying animals, despite the various factors that promote intra-clutch variation leading to asynchronous hatching and emergence from nests, synchronous hatching and emergence occurs in many taxa. This synchrony may be adaptive by reducing predation risk, but few data are available in any natural system, even for iconic examples of the anti-predator function of group formation. Here, we show for the first time that increased group size (number of hatchlings emerging together from a nest) reduces green turtle (Chelonia mydas) hatchling predation. This effect was only observed earlier in the night when predation pressure was greatest, indicated by the greatest predator abundance and a small proportion of predators preoccupied with consuming captured prey. Further analysis revealed that the effect of time of day was due to the number of hatchlings already killed in an evening; this, along with the apparent lack of other anti-predatory mechanisms for grouping, suggests that synchronous emergence from a nest appears to swamp predators, resulting in an attack abatement effect. Using a system with relatively pristine conditions for turtle hatchlings and their predators provides a more realistic environmental context within which intra-nest synchronous emergence has evolved.

opencc-zeroDec 2014View details →

Data from: Deepwater Horizon oil spill impacts on sea turtles could span the Atlantic

We investigated the extent that the 2010 Deepwater Horizon oil spill potentially affected oceanic-stage sea turtles from populations across the Atlantic. Within an ocean-circulation model, particles were backtracked from the Gulf of Mexico spill site to determine the probability of young turtles arriving in this area from major nesting beaches. The abundance of turtles in the vicinity of the oil spill was derived by forward-tracking particles from focal beaches and integrating population size, oceanic-stage duration and stage-specific survival rates. Simulations indicated that 321 401 (66 199–397 864) green (Chelonia mydas), loggerhead (Caretta caretta) and Kemp's ridley (Lepidochelys kempii) turtles were likely within the spill site. These predictions compared favourably with estimates from in-water observations recently made available to the public (though our initial predictions for Kemp's ridley were substantially lower than in-water estimates, better agreement was obtained with modifications to mimic behaviour of young Kemp's ridley turtles in the northern Gulf). Simulations predicted 75.2% (71.9–76.3%) of turtles came from Mexico, 14.8% (11–18%) from Costa Rica, 5.9% (4.8–7.9%) from countries in northern South America, 3.4% (2.4–3.5%) from the United States and 1.6% (0.6–2.0%) from West African countries. Thus, the spill's impacts may extend far beyond the current focus on the northern Gulf of Mexico.

opencc-zeroDec 2013View details →

Data from: High rates of growth recorded for hawksbill sea turtles in Anegada, British Virgin Islands

Management of species of conservation concern requires knowledge of demographic parameters, such as rates of recruitment, survival, and growth. In the Caribbean, hawksbill turtles (Eretmochelys imbricata) have been historically exploited in huge numbers to satisfy trade in their shells and meat. In the present study, we estimated growth rate of juvenile hawksbill turtles around Anegada, British Virgin Islands, using capture–mark–recapture of 59 turtles over periods of up to 649 days. Turtles were recaptured up to six times, having moved up to 5.9 km from the release location. Across all sizes, turtles grew at an average rate of 9.3 cm year−1 (range 2.3–20.3 cm year−1), and gained mass at an average of 3.9 kg year−1 (range 850 g–16.1 kg year−1). Carapace length was a significant predictor of growth rate and mass gain, but there was no relationship between either variable and sea surface temperature. These are among the fastest rates of growth reported for this species, with seven turtles growing at a rate that would increase their body size by more than half per year (51–69% increase in body length). This study also demonstrates the importance of shallow water reef systems for the developmental habitat for juvenile hawksbill turtles. Although growth rates for posthatching turtles in the pelagic, and turtles larger than 61 cm, are not known for this population, the implications of this study are that Caribbean hawksbill turtles in some areas may reach body sizes suggesting sexual maturity in less time than previously considered.

opencc-zeroDec 2016View details →

Data from: Detecting elusive aspects of wildlife ecology using drones: new insights on the mating dynamics and operational sex ratios of sea turtles

Offspring and breeding (operational) sex ratios (OSR) are a key component of demographic studies. While offspring sex ratios are often relatively easy to measure, measuring OSRs is often far more problematic. Yet highly skewed OSRs, and a lack of male-female encounters, may be an important extinction driver. Using loggerhead sea turtles (Caretta caretta) as a case study, we showed the utility of drones, i.e. unmanned aerial vehicles (UAVs) to distinguish adult males and females in a marine breeding area, using a combination of morphological characteristics (tail length) and behavioural differences (active mating, courting and searching by males versus resting by females). Through repeated surveys, we documented seasonal changes in the OSR. While the number, and ratio, of males and females on the breeding grounds changed massively, the ratio of receptive females (derived from the rate of influx of new individuals to the area) to breeding males remained close to 1:1 for much of the period before nesting commenced. Hence, we show how large imbalances in the number of adult males and females may translate into relatively balanced OSRs. Our results suggest that the departure of males from the breeding grounds is linked to a decline in female receptivity, with female sea turtles being known to store sperm to ensure high clutch fertility throughout the nesting season. In conclusion, while we detected up to three times more females than males at the breeding ground, at present, OSRs appear stable. However, because most males breed annually (versus biannually by females), there might only be ˜100 males in the adult population (i.e. adult sex ratio of 1:7.5), which might become further skewed under expected climate change scenarios; thus, we need to identify the minimum number of males required to prevent extinction. Finally, we highlight the use of UAVs for assessing the mating dynamics of other marine, terrestrial or avian species, in which adults might exhibit visually detectable differences, such as sexual dimorphism, external body characteristics or grouping tendencies.

opencc-zeroDec 2014View details →

Data from: Heritable variation in heat shock gene expression: a potential mechanism for adaptation to thermal stress in embryos of sea turtles

The capacity of species to respond adaptively to warming temperatures will be key to their survival in the Anthropocene. The embryos of egg-laying species such as sea turtles have limited behavioural means for avoiding high nest temperatures, and responses at the physiological level may be critical to coping with predicted global temperature increases. Using the loggerhead sea turtle (Caretta caretta) as a model, we used quantitative PCR to characterise variation in the expression response of heat shock genes (hsp60, hsp70, and hsp90; molecular chaperones involved in cellular stress response) to an acute non-lethal heat shock. We show significant variation in gene expression at the clutch and population levels for some, but not all hsp genes. Using pedigree information, we estimated heritabilities of the expression response of hsp genes to heat shock and demonstrated both maternal and additive genetic effects. This is the first evidence that the heat shock response is heritable in sea turtles and operates at the embryonic stage in any reptile. The presence of heritable variation in the expression of key thermotolerance genes is necessary for sea turtles to adapt at a molecular level to warming incubation environments.

opencc-zeroDec 2021View details →

Sick of attention: The effect of a stress-related disease on juvenile green sea turtle behaviour in the face of intense and prolonged tourism

Anthropogenic activities are increasingly linked to emerging diseases that cause mortality across many taxa. Human interference through ecotourism, in particular, can increase the stress levels of wild populations and promote the spread of disease. In Akumal Bay, Mexico, green sea turtles (Chelonia mydas) are increasingly infected with fibropapillomatosis (FP), an infectious disease associated with stress-induced immunosuppression linked to high human density, which is particularly high in this area because of intense and prolonged ecotourism. To examine if FP might be associated with behavioural indicators of stress and varying levels of tourist pressure, we observed the behaviour of turtles and the number of tourists through 20-minute focal sampling periods from May to August 2017. We related disease presence and tourist pressure to several aspects of turtle behaviour, specifically feeding, resting, vertical movements (i.e., surfacing and diving), and evasive responses. Turtles that had FP engaged in fewer feeding periods, vertical movements, and evasive responses. Additionally, with increasing tourist pressure, all turtles spent less time engaging in vertical movements and had more evasive responses. Our results suggest that the presence of FP affects green sea turtle behavior, potentially increasing their exposure to tourists. Sick and healthy turtles appear to react differently to tourists, suggesting that FP weakens behavioural responses to tourist pressure. Future management strategies should consider regulating tourist pressure on turtles to reduce the incidence and progression of FP.

opencc-zeroFeb 2022View details →

Data from: Sea turtle epibiosis: Global patterns and knowledge gaps

This database serves to summarize over 100 years of sea turtle epibiont research. We conducted a two-tiered literature search to compile all records of sea turtle-epibiont interactions along with their associated metadata. A structured search was conducted in Web of Science, Google Scholar, and Sea Turtle Online Bibliography (Archie Carr Center for Sea Turtle Research, University of Florida), then an unstructured literature search was conducted by reviewing the reference lists of all relevant publications and reports from the structured search. We included any peer-reviewed scientific article, thesis/dissertation, conference presentation, and official report that contained information on sea turtle epibiosis. From each applicable reference, we extracted data on all reported sea turtle-epibiont interactions according to the data categories and descriptions listed below (Table 1 in Robinson and Pfaller 2022; doi link when available). We constrained our database to only include records of sea turtle-epibiont interactions from (1) turtles surveyed in the wild, (2) animal epibionts (i.e., Kingdom Animalia), and (3) macro-epibionts (>1 mm). For the seven global sea turtle species, we identified 304 studies conducted between 1886 and 2020 that included a combined total of 1717 sea turtle-epibiont interactions involving 374 unique epibiont taxa from 11 Phyla.

opencc-zeroMay 2022View details →

Validating the use of stereo-video cameras to conduct remote measurements of sea turtles

Stereo-Video Camera Systems (SVCSs) are a promising tool to remotely measure body size of wild animals without the need for animal handling. Here, we assessed the accuracy of SVCSs for measuring straight carapace length (SCL) of sea turtles. To achieve this, we hand captured and measured 63 juvenile, sub-adult, and adult sea turtles across three species, greens, Chelonia mydas (n = 52), loggerheads, Caretta caretta (n = 8), and Kemp's ridley, Lepidochelys kempii (n = 3) in the waters off Eleuthera, The Bahamas and Crystal River, Florida, U.S.A. between May - November 2019. Upon release, we filmed these individuals with the SVCS. We performed photogrammetric analysis to extract stereo SCL measurements (eSCL), which were then compared to the (manual) capture measurements (mSCL). mSCL ranged from 25.9 – 89.2 cm, while eSCL ranged from 24.7 – 91.4 cm. Mean percent bias of eSCL ranged from -0.61% (± 0.11 SE) to -4.46% (± 0.31 SE) across all species and locations. We statistically analyzed potential drivers of measurement error, including distance of the turtle to the SVCS, turtle angle, image quality, turtle size, capture location, and species.Using a linear mixed effects model, we found that the distance between the turtle and the SVCS was the primary factor influencing measurement error. Our research suggests that stereo-video technology enables high-quality measurements of sea turtle body size collected in situ without the need for hand-capturing individuals. This study contributes to the growing knowledge base that SVCS are accurate for body size measurements independent of taxonomic clade.

opencc-zeroJun 2022View details →

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.

opencc-zeroDec 2021View details →

Data for: Representation in sea turtle science: slow progress towards gender equity and globalization revealed from thirty years of symposium abstracts

Sea turtles are a circumglobal taxon that receive considerable research attention, yet there is little information about the demographics of sea turtle researchers. To assess long-term trends in demographic, geographic, and institutional representation within the sea turtle community, we quantified information from 7041 abstracts presented at the International Sea Turtle Symposium (ISTS) between 1988–2018. The dataset from this study is presented here.

opencc-by-4.0Jun 2015View details →

Supplementary material 1 from: Ullmann J, Stachowitsch M (2015) A critical review of the Mediterranean sea turtle rescue network: a web looking for a weaver. Nature Conservation 10: 45-69. https://doi.org/10.3897/natureconservation.10.4890

Stepping stones toward a Mediterranean sea turtle rescue network: Explanation note: Historical outline of sea turtle protection in the Mediterranean.

opennotspecifiedNov 2017View details →

FIGURE 2 in Hexapleomera urashima sp. nov. (Crustacea: Tanaidacea), a tanaidid epibiotic on loggerhead sea turtles at Yakushima Island, Japan

FIGURE 2. Hexapleomera urashima sp. nov. A, two living animals (arrowheads) on the carapace of Caretta caretta individual Y7115 (left tag number), photographed by Daisuke Uyeno; B, C, female holotype and male paratype (ICHUM-5381 and 5396), respectively, dorsal views, fixed specimens. Scale bars: 1 mm.

FIGURE 10 in Chelonocytherois omutai gen. et sp. nov. (Crustacea: Ostracoda) from the back of loggerhead sea turtles

FIGURE 10. Chelonocytherois omutai gen. et sp. nov. A and B, male, holotype (UMUT RA 33122); C, female, paratype (UMUT RA 33129). A, Right hemipenis; B, Left hemipenis; C, Female copulatory organ and posterior body. Abbreviations: bc, basal capsule; cd, copulatory duct; ddl, dorso-distal lobe; ddp, dorso-distal prehensile process; fgo, female genital opening; rs, receptaculum seminis; sd, spermathecal duct; vdl, ventro-distal lobe. Scale: 50 μm.

FIGURE 9 in Chelonocytherois omutai gen. et sp. nov. (Crustacea: Ostracoda) from the back of loggerhead sea turtles

FIGURE 9. Chelonocytherois omutai gen. et sp. nov., male, holotype (UMUT RA 33122). A, Fifth limb; B, Sixth limb; C, Seventh limb. Scale: 50 μm.

FIGURE 8 in Chelonocytherois omutai gen. et sp. nov. (Crustacea: Ostracoda) from the back of loggerhead sea turtles

FIGURE 8. Chelonocytherois omutai gen. et sp. nov. A and B, male, holotype (UMUT RA 33122); C, male, paratype (UMUT RA 33125). A, Mandibula; A′, Distal area of mandibular palp; B, Maxillula; B′, Distal area of palp and endites of maxillula; C, Oral cone. Scale: 50 μm.

FIGURE 7 in Chelonocytherois omutai gen. et sp. nov. (Crustacea: Ostracoda) from the back of loggerhead sea turtles

FIGURE 7. Chelonocytherois omutai gen. et sp. nov. A and B, male, holotype (UMUT RA 33122); C, female, paratype (UMUT RA 33129). A, Antennula; B, Antenna; B′, Comb-like seta on sixth podomere of antenna; C, Distal area of antenna; C′, Comb-like seta on sixth podomere of antenna. Scale: 50 μm.