Lepidochelys Olivacea Research Articles

Feeding ecology of the olive ridley turtle (Lepidochelys olivacea) in southern Brazil

Feeding ecology of the olive ridley turtle (Lepidochelys olivacea) in southern Brazil

First report of Rhytidodes gelatinosus (Rudolphi, 1819) Looss, 1901 (Digenea: Rhytidodidae) in an olive-ridley Turtle Lepidochelys olivacea (Eschscholtz, 1829) from Brazil.

This article reports the first occurrence of Rhytidodes gelatinosus (Rudolphi, 1819) Looss, 1901 (Digenea: Rhytidodidae) in the olive-ridley turtle Lepidochelys olivacea (Testudines: Chelonidae), in an individual found in the State of Sergipe, Brazil. Although R. gelatinosus has already been described in other species of sea turtles in the world, this is the first report of this parasite in L. olivacea. We also present a list of hosts and locations where this helminth has already been identified.

FIRST OSTEOMYELITIS RECORDS IN NESTING FEMALE TURTLES OF Lepidochelys olivacea (ESCHOLTZ 1829) AT LA ESCOBILLA SANCTUARY, OAXACA, MEXICO

We provide the first records of osteomyelitis in shell of nesting female turtles of Lepidochelys olivacea at La Escobilla Sanctuary, Mexico. Osteomyelitis is an infectious and inflammatory disease of the bone, characterized by necrosis and destruction of bone tissue. Until now, there no exist records of this infectious disease of bone in olive ridley turtle (Lepidochelys olivacea) in tropical waters.

Conservation‐relevant reproductive parameters from long‐term tagging of two globally important sea turtle nesting aggregations in Central Africa

Abstract Assessing abundance and monitoring ecology and population trends are of critical importance for animal species of conservation concern. For sea turtles, annual nest counts represent the most common method of estimating population size. However, to develop a better understanding of population trends, these data need to be complemented by other reproductive parameters, which are lacking for many nesting populations across central Africa. To this end, an intensive capture–mark–recapture programme was conducted spanning 21 years (1997–2018) in the most important nesting sites on the Atlantic coast of central Africa (Gabon and Congo) for leatherback (Dermochelys coriacea) and olive ridley (Lepidochelys olivacea) sea turtles. A total of 18,105 encounters of 14,109 D. coriacea individuals and 2678 encounters of 2427 L. olivacea individuals were recorded. Biological and technical parameters such as clutch frequency, inter‐nesting interval, remigration interval, annual survival rate, somatic growth, size trends, tag loss and number of annual nesting females were estimated through a variety of methods and models. The study detected a decline in body size and low survival probability (not due to tag loss) in both species but no clear decline in estimated annual number of nesting females. High fidelity to nesting sites (<30 km for both species) implies that the current conservation strategy, protecting the main nesting areas, could be effective. We recommend that local conservation managers promote: (i) continued monitoring of the nesting activity of the two species through capture–mark–recapture programmes; (ii) continued nest counts at long‐term monitoring sites, which may also detect possible spatial shifts; and (iii) strengthening of cross‐border cooperation between Gabon and Republic of the Congo given the observed connectivity between nesting sites of the two countries.

THE EFFECT OF TEMPERATURE DIFFERENCES ON HATCHING RATES OF LEKANG TURTLE (Lepidochelys olivacea) EGGS IN SEMI-NATURAL NESTS

This research was conducted on August 31, 2021 – December 7, 2021, at the UPTD KPSDKP, West Sumatra Province. The purpose of this study was to determine the effect of temperature differences on incubation time, hatching rate, and survival rate of turtle hatchlings (Lepidochelys olivacea). The method used in this study is an experiment that uses 3 trials plus 1 control, with 3 repetitions. Turtle eggs were incubated with the same depth and number of eggs with the addition of different temperatures from incandescent lamps with different powers. Then proceed with the calculation of incubation time, percentage of hatching, and survival of hatchling. Based on the results of the research, for the calculation of incubation time, the experimental unit with the shortest incubation period was produced by experimental unit B, with a temperature range of 27.5–29.5⁰C, which was 58 days. The incubation period that took the longest was the control experimental unit with an average temperature of 25⁰C, which was 65 days. For the results, the most optimal hatching rate was produced by experimental unit B, with an average hatching rate of 86%. Meanwhile, the lowest hatching rate was obtained from experimental unit C with an average hatching rate of only 53.3%. Then for the survival of the hatchlings after being quarantined for one week, all of them show the number 100%, which means that no hatchlings died during the quarantine

Evaluation of sea turtle morbidity and mortality within the Indian Ocean from 12 years of data shows high prevalence of ghost net entanglement.

Anthropogenic activities can negatively affect sea turtle populations. Quantifying the effect of human actions on these threatened species can help guide management strategies to reduce adverse impacts. However, such assessments require extensive effort and resources and as such have not been carried out in many areas of important sea turtle habitat, including the Republic of the Maldives (Maldives). Here, we utilise 12 years of data (2010-2022) collected from marine turtle stranding and rehabilitation cases from across the Maldives to identify the key threats in this region. Olive ridley turtles were found stranded or injured most frequently (74.7% of total cases), along with hawksbill (15.2%), and green (10.1%) turtles. Anthropogenic factors were the primary cause of injury or stranding in 75.2% of cases with entanglement in ghost fishing gear being the most common (66.2% of all cases). Other causes of morbidity, such as from turtles being kept as pets (5.6%), boat strikes (<1%), bycatch (<1%), and poaching (<1%) were recorded less frequently. Olive ridley turtles were more likely to have injuries associated with entanglement than other species and showed a peak in admissions during the northeast monsoon, in the period following the known arribada nesting season in nearby India. Turtles admitted to rehabilitation following entanglement were released a mean of 70 days sooner and had 27.5% lower mortality rates than for other causes of admission. This study highlights the high prevalence of ghost net entanglement of sea turtles within the Maldives. The topic of ghost fishing is of global importance and international cooperation is critical in tackling this growing issue.

Suitable habitat of Lepidochelys olivacea and the changes under climate change.

As a vulnerable species identified by the International Union for Conservation of Nature (IUCN), Lepidochelys olivacea has attracted extensive attention in recent years. To examine its current distribution and that under future climate change scenarios, we compiled the occurrence data of L. olivacea. With eight predictor variables, including depth, offshore distance, mean primary productivity, minimum primary productivity, mean sea surface temperature, minimum sea surface temperature, mean sea surface salinity, and minimum sea surface salinity, we predicted its distribution in an ensemble species distribution model. The accuracy of the model was evaluated with the parameters of areas under curves (AUC) and true skill statistics (TSS). The results showed that the AUC and TSS values were 0.96 and 0.81, respectively, indicating a good predictive performance of the ensemble model. Sea surface temperature and salinity were the two most important variables determining the distribution of L. olivacea, with the suitable temperature ranging from 23 to 29 ℃ and salinity below 34. The current distribution range of L. olivacea was between 30° N-25° S. Under future climate scenarios, its distribution range would decrease, especially under the RCP85 scenario in the 2100s (with a 28% reduction in the suitable survival range). The results of model validation showed that it had high accuracy and could make accurate predictions of the distribution. This study would provide references for the development of more rational conservation measures and management strategies.

Empowering the Rural Community as Turtle Breeder: Case Studi of Dunu Village, Gorontalo Utara Regency

Turtles are marine reptiles that have existed on Earth for millions of years and have managed to survive until today. Turtles play a crucial role in the marine ecosystem, maintaining the balance of nature and contributing to marine biodiversity. The method used in this research is a qualitative approach, which includes conducting in-depth interviews, participatory observations, and analyzing relevant documents. The data obtained will be analyzed using descriptive and interpretative approaches to illustrate the process of empowering the rural community in Dunu Village. This research aims to understand how the empowerment of the Dunu village community as turtle breeders takes place. The study was conducted for a duration of two weeks, starting from June 27, 2023, to July 11, 2023. The research findings indicate that in Dunu village, Gorontalo Utara Regency, three types of turtles are being conserved. The turtle species involved are the green turtle (Chelonia mydas), hawksbill turtle (Eretmochelys imbricata), and olive ridley turtle (Lepidochelys olivacea). There are two individuals from Dunu village who are recognized as professional turtle breeders and actively participate in the protection of turtle eggs, caring for hatchlings, and conducting patrols along the beach where the turtles nest. These two breeders received training from the Balai Konservasi Sumber Daya Alam (BKSDA) Sulawesi Utara through the Seksi Konservasi Wilayah II Gorontalo.

Herpetofauna of Piuaí state, northeastern Brazil

Piauí State houses a relevant biological diversity, but, simultaneously, its growing economy has sped up the use of natural resources in the region, oftentimes in an unorganized way, a fact that affects amphibians and reptiles’ diversity. Knowledge on local fauna provides subsidies to elaborate strategies aimed at implementing conservation practices. Accordingly, the aim of the present study is to screen the herpetofauna of Piauí State to help better understanding the composition and richness of species registered in previously developed scientific studies. In order to do so, a systematic review was carried out; it included the largest number possible of publications about the distribution of amphibian and reptile species in the state. In total, 181 species (60 amphibian and 121 reptile species) were recorded in 73 scientific studies developed in 38 of the 224 municipalities of Piauí State - Parnaíba, Ilha Grande and Piracuruca were the municipalities recording the largest number of publications. Most herpetofauna known in Piauí State is distributed in conservation units (CU). Seven species in these units are endangered, namely: Amphisbaena frontalis, Caretta caretta, Chelonia mydas, Eretmochelys imbricate, Lepidochelys olivacea, Dermochelys coriácea and Trachemys adiutrix. This finding reinforces the need of actions to conserve and preserve the state’s herpetofauna.

Artisanal fishery with surface gillnets and megafauna strandings

Bycatch is an issue of worldwide relevance involving conflicts between conservation and fishery interests. In Brazil, this conflict has been highlighted in relation to the regulation of small-scale fishery with surface gillnets. To promote management and transformation of this conflict, we analyzed the relationship between catch unloadings from small-scale fishing with surface gillnets and strandings of marine megafauna. We used fishery monitoring data and beach monitoring data in São Paulo between 2015 and 2021, relating to Chelonia mydas, Caretta caretta, Lepidochelys olivacea, Pontoporia blainvillei and Sotalia guianensis. The analyses included (i) overview of catches unloadings from small-scale fishing with surface gillnets and strandings that resulted in the death of each of these species over the course of the year; (ii) correlation tests between those variables for the northern, central, and southern regions; and (iii) performing regression analyses for municipalities within these regions, exhibiting statistically significant positive correlations. The fisheries harvest period was found not to overlap with the stranding distribution. In correlation tests, only strandings of C. mydas in the northern and southern regions, S. guianensis in the southern region and P. blainvillei in the central region showed relationships with fishing landings. The regression analysis was significant for C. mydas and S. guianensis. At the municipal level, the results were statistically significant for C. mydas in São Sebastião, Ubatuba, Ilha Comprida and Cananéia and for S. guianensis in Cananéia. However, the regression explained a small part of the mortality and other impact factors were pointed out. Non-prohibitive management measures, participatory studies, and direct methods for evaluating the interaction between fisheries and megafauna associated with environmental factors should be implemented, along with analyses on other impacts on megafauna.

Nowhere to hide: Sea turtle bycatch in Northwest Africa

Abstract Fisheries bycatch is considered the largest threat to sea turtle populations globally. However, it has been challenging to assess the impact of bycatch on sea turtles in some regions such as Northwest Africa (i.e. Cabo Verde, Guinea, Guinea–Bissau, Mauritania, Senegal, Sierra Leone and The Gambia) owing to large data gaps. This hampers effective management actions and interferes with conservation efforts in the region. Five sea turtle species occur in Northwest Africa (i.e. green turtle Chelonia mydas, hawksbill Eretmochelys imbricata, leatherback Dermochelys coriacea, loggerhead Caretta caretta and olive ridley Lepidochelys olivacea). The region has regionally and globally important sea turtle nesting and foraging habitats and is a global fishing hotspot, with high and increasing fishing pressure. Available information on sea turtle bycatch in Northwest Africa was compiled from peer‐reviewed and grey literature from 2010 onwards to determine the impact of artisanal and industrial fisheries (by gear type) on regional sea turtle populations and assess the level of threat to individual species. All sea turtle species occurring in the region are impacted by bycatch. Reports suggest that green turtles and loggerheads have the highest bycatch rates, probably owing to their regional abundance and widespread distribution. Some of the potentially highest reported global bycatch rates (14,000–90,000 turtles/year/country) are noted, particularly in gillnets, longlines and handlines. However, further research is needed to understand mortality levels from artisanal fisheries and assess the impact of trawl fisheries operating in the region. Additional sources of mortality include deliberate capture for consumption or trade. To strengthen regional sea turtle conservation and reduce sea turtle bycatch and mortality, urgent action is needed to implement and enforce national protection, establish a bycatch reduction framework (including gear modifications and spatio‐temporal closures), improve fisheries data collection and build capacity.

Marine pollution between gyres: plastic debris in marine turtles and dolphins in French Guiana, Equatorial Atlantic

Plastic pollution has not raised much attention until the 2000s, despite being manufactured for about a century. It is now considered one of the most substantial environmental issues. Here we investigate the presence of plastic contamination in 34 stranded animals on the coast of French Guiana, South America. Here we present information highlighting the magnitude of plastic contamination in marine coastal and pelagic tropical marine vertebrates on the Equatorial Atlantic coast of South America. All four species studied here are protected and emblematic vertebrates of the region, with a fragile conservation status, including the olive ridley turtle Lepidochelys olivacea, the green turtle Chelonia mydas and the leatherback turtle Dermochelys coriacea, and a small cetacean, the Guiana dolphin Sotalia guianensis. Macroplastics (polypropylene, polyethylene, terephthalate, and polystyrene) were detected in four juvenile green turtles. Microplastics (polypropylene, polyethylene, terephthalate, polystyrene, nylon, acrylates, polycarbonates) were found in 13 individuals (two dolphins, six olive ridleys, four green turtles, and the leatherback turtle). The sampled species have different diets, distribution patterns, and ages, suggesting widespread plastic pollution. The study area is located far from the oceanic gyres. However, they are influenced by the North Brazilian Current, the Amazon River, and other rivers of the Guianas.

The use of the territorial sea by Lepidochelys olivacea (Eschscholtz, 1829) in front of nesting beaches in Oaxaca, Mexico

Scientific research focused on sea turtle monitoring and management has relied on nesting beaches, but little attention has been paid to surveying turtles in the territorial sea off nesting beaches. This study aimed to evaluate how the Olive Ridley turtle, Lepidochelys olivacea, uses the territorial sea off the nesting beaches in Puerto Escondido, Puerto Ángel, Santa María Huatulco, and Morro Ayuta, in Oaxaca, Mexico. Between December 2017 and August 2018, 2394 individuals were sighted in the territorial sea engaged in the following activities: feeding (6 individuals), mating (164 individuals), swimming (2172 individuals), and resting (49 individuals). We analyzed the diet and body condition of L. olivacea and identified which biophysical factors affect the distribution of these sea turtles in the region. We also recorded direct interactions with fishers and tourism service providers. We captured 40 individuals, collected morphometric data, and analyzed esophageal content to characterize feeding habits, which were correlated with a body condition index. Diet items included crustaceans, tunicates, four commercially important fish species, jellyfish, mollusks, and algae. Approximately 95% of turtles exhibited very good body condition. The largest turtle aggregations were recorded in Morro Ayuta (898 individuals) and Puerto Ángel (808 individuals). In situ sea surface temperature and chlorophyll-a concentrations from satellite images were used to characterize the territorial sea. Sea surface temperature was negatively correlated with turtle abundance. Management and conservation actions are needed for sea turtles that address the negative interactions with fishers (e.g., competition for commercially important fish species) and tourism service providers that occur in the territorial sea off nesting beaches to protect these crucial reproductive habitats in the long term.

New Delhi metallo-β-lactamase-1-producing Citrobacter portucalensis belonging to the novel ST264 causing fatal sepsis in a vulnerable migratory sea turtle

Olive ridley (Lepidochelys olivacea) turtles migrate across tropical regions of the Atlantic, Pacific, and Indian Oceans. Worryingly, olive ridley populations have been declining substantially and is now considered a threatened species. In this regard, habitat degradation, anthropogenic pollution, and infectious diseases have been the most notorious threats for this species. We isolated a metallo-β-lactamase (NDM-1)-producing Citrobacter portucalensis from the blood sample of an infected migratory olive ridley turtle found stranded sick in the coast of Brazil. Genomic analysis of C. portucalensis confirmed a novel sequence type (ST), named ST264, and a wide resistome to broad-spectrum antibiotics. The production of NDM-1 by the strain contributed to treatment failure and death of the animal. Phylogenomic relationship with environmental and human strains from African, European and Asian countries confirmed that critical priority clones of C. portucalensis are spreading beyond hospital settings, representing an emerging ecological threat to marine ecosystems.

Reassessment of the olive ridley sea turtle Lepidochelys olivacea nesting population at Nancite Beach, Costa Rica

AbstractNancite is a fully protected beach within the Guanacaste Conservation Area, Costa Rica where olive ridley (Lepidochelys olivacea) sea turtles nest in synchronous mass‐nesting events known as arribadas. Arribadas decreased in magnitude at this beach by approximately 90% during the period 1971–2007 due to unknown causes. The total count estimate of females nesting in a year also decreased over these decades. In the present study, from August 2009 to February 2021, the trend of arribada nesting female abundance and estimated annual production of hatchlings were assessed and compared with previous trend analyses. A total of 62 mass‐nesting events were quantified in the period 2009–2021, with an estimated annual average of 64,694 nesting females. Trend analysis indicated that during our recent study period, the number of females per arribada event increased by an estimated 14% (8%, 20% CI95%). During this period, a mean hatching rate of 33.4% was estimated, corresponding to an overall estimated production average of 2,165,597 per season, which represented an increase of 82.7% compared with a previous estimate for the period 1980–1984, when the arribadas were larger. We suggest that the growth in hatchling production over the past four decades is at least in part responsible for the slight increase in the estimated size of arribadas since 2009/2010. However, because maximal hatching success did not increase above 60%, the beach may be close to reaching carrying capacity, and it seems that high hatchling production may soon level off or begin to decrease. Thus, it is not clear whether current hatchling production will lead to the recovery of the Nancite population to the historical levels documented in the 1970s and early 1980s.

Mitochondrial DNA and local ecological knowledge reveal two lineages of leatherback turtle on the beaches of Oaxaca, Mexico

Despite multiple conservation efforts of the Mexican government, the leatherback turtle is at serious risk of extinction. In this study, we investigated the possible presence of a genetic bottleneck that could prevent the recovery of this species and compared these findings with those of the olive ridley turtle, which is in true recovery. Our results confirmed that a demographic change occurred in the past and the presence of two different leatherback turtle lineages that diverged approximately 13.5 million years ago. Local ecological knowledge (LEK) also described the presence of these two lineages and warned that one is at higher risk of extinction than the other. Genetic analysis confirmed 124 mutations between the two lineages, and much lower genetic diversity in one lineage than the other. Our study highlights and substantiates the power of mixing LEK, environmental history, and genetics to better understand conservation challenges of highly threatened species such as the leatherback turtle. Moreover, we report a new lineage of the leatherback turtle which may represent a distinct species. Future studies should focus on morphological, ecological, biogeographical, evolutionary and conservation perspectives for the analysis of the new lineage.

Anthropogenic threats associated with mortality and biomass of stranded sea turtles on the northern coast of São Paulo State, Brazil

ABSTRACT Beach monitoring programmes along the Brazilian coast in recent years have provided stranding data which can be analysed to show the effects of human impacts on sea turtle populations. In Brazil, the five species recorded are threatened with extinction. In this study, data from strandings of sea turtles on the northern coast of the State of São Paulo, Brazil, over six years (2015–2021), were used to evaluate whether human activities are associated with impacts on the populations and to analyse the effects of seasonality on abundance. There were 6411 strandings of sea turtles, the majority being Chelonia mydas, followed by Caretta caretta, Lepidochelys olivacea, Eretmochelys imbricata and Dermochelys coriacea. Strandings occurred mainly during winter and spring. Where it was possible to determine the cause of death of an individual, there were several associations with anthropogenic factors, mainly solid waste, fishing gear, collisions with vessels, injuries and dredging. The high incidence of strandings of sea turtles on the Brazilian coast, mostly juveniles, and the great impact of anthropogenic factors in the causa mortis indicate the need to adopt ocean education strategies and public policies that can establish effective management and conservation plans of marine ecosystems.

A Pilot Study of Mercury Distribution in the Carapace of Four Species of Sea Turtles from Northeastern Brazil.

Scutes present very complex morphologies with different growth rates at different areas of the carapace that can change the accumulation process of essential and non-essential metals. To infer the effects of morphology and growth on Hg concentrations in scutes, we mapped them in the carapace of one individual of four species of sea turtles sampled along the Brazilian coast. The results showed that Hg concentrations were higher in the vertebral scutes of Chelonia mydas and Eretmochelys imbricata suggesting variation in growth rates of different carapace areas since the vertebral area is the first to develop prior to costal areas. Caretta caretta and Lepidochelys olivacea did not show differences between carapace areas. The preliminary data from this pilot study indicate that vertebral scutes may be suitable for monitoring Hg in C. mydas and E. imbricata, since they reflect longer exposure period. A species-to-species comparison of Hg concentrations is not possible due to the small number of sampled individuals, nevertheless, E. imbricata showed remarkably lower Hg concentrations compared to the other three species. Further studies are required for all four species, with a larger number of individuals, preferentially of varying life stages, due to the unknown effects of different diets, Hg exposure, and migration histories.

Developed black beaches - too hot to emerge? Factors affecting sand temperatures at nesting grounds of olive ridley sea turtles (Lepidochelys olivacea)

Climate change research on sea turtles has focused on the impact of rising temperatures on sex ratios, while the thermal ecology of natural nesting grounds has received less attention. Many nesting beaches are highly affected by vegetation loss and urbanization which in turn may affect their thermal profile, particularly at beaches with dark volcanic sand. We studied the sand temperatures on two urban-developed volcanic sea turtle nesting beaches in Guatemala for two years, and their potential effect on the thermal ecology of sea turtle nests by using the olive ridley as model species. We hypothesized that local weather, type of cover at surface, and season (dry vs rainy) will have a pronounced effect on sand temperatures, potentially affecting the hatching success of sea turtles. Average sand temperatures at nesting beaches were almost always above the pivotal temperature (87% of days), and either close to or above the thermal maximum tolerance of sea turtle embryos over longer periods (78% of days). We found that higher air temperatures led to higher sand temperatures, and high relative humidity and precipitation led to lower sand temperatures. As expected, sand temperatures in plots covered by vegetation were lower (32.5 ± 2.8°C) than those without vegetation cover (33.1 ± 2.6°C). Plots close to concrete structures showed the highest sand temperatures (34.0 ± 3.2°C). Our results highlight the relevance of vegetation in buffering the effects of high sand temperatures, which will have profound implications for the resilience of olive ridleys to global warming.

Evaluation of Reproductive Success of the Olive Ridley Turtle Lepidochelys olivacea (Testudinata: Cheloniidae) Using Different Incubation Treatments

In nesting areas with extreme climatic conditions, such as high temperatures, it is advisable to use mitigation strategies that counteract these negative effects on the hatching success of sea turtle nests. We evaluated the effect of incubation treatment on hatching success and incubation period for olive ridley turtles Lepidochelys olivacea during the 2019 nesting season in Guerrero, Mexico. Three incubation treatments (T1 = shade & freshwater irrigation; T2 = shade, seawater pre-irrigation, sand covered & freshwater irrigated; T3 = shade, seawater pre-irrigation, covered with a plastic lid & freshwater irrigated) were trialed at two different times during the nesting season. One of our goals was to compare the reproductive success of hatchery nests versus in situ nests, however, in situ nests hatching success was zero. We found that treatments had no effect on hatching success or incubation period, but there were differences in proportions of dead and crushed hatchlings. Clutches incubated in the second relocation period had longer incubation times. However, nest relocation periods had no effect on hatching success, dead hatchlings, or the proportion of crushed hatchlings. Our results also showed that the amount of seawater applied to the holes and the rate of irrigation were not lethal for the incubating eggs, but prolonged the incubation period. These results could help to increase our understanding of sea turtle reproductive success and may serve as a baseline to adapt the spatio-temporal conditions of the hatcheries in other areas with similar environmental conditions.