Ridley Sea Turtle Lepidochelys Olivacea Research Articles

Validating trends in olive ridley sea turtle nesting track counts in Guatemala in light of a national hatchery protection strategy

AbstractThe 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 turtle nests on the condition they donate 20% of each nest to a hatchery, where the eggs are incubated and hatchlings later released. This system was initiated in the 1970s and, until recently, no effort has been made to determine its sustainability. In a 2020 publication based on tracks on a single beach in Guatemala and 15 years of egg incubation data from Guatemalan hatcheries, it was concluded that the population had increased. Several weaknesses were detected in this research. To verify the validity of the conclusion, we analysed data from 22 years (2 years are missing) and 11 beaches using several statistical models. We used an intraseasonal model of nesting phenology to fill in missing data for monitored periods during a nesting season, and a new method of spatial and temporal aggregation of nesting seasons. Based on our findings, we reject the hypothesis that olive ridley sea turtle nesting activity is increasing. The total nesting activity for these 12 beaches was stable over the 22-year period. Because of inconsistent hatchery management and the financial dependency of local communities on the sale of turtle eggs, the number of incubated eggs cannot be used as an indicator of the population trend of olive ridley sea turtles in Guatemala.

Surveys of the Angolan coast uncover the largest olive ridley sea turtle nesting population in the Atlantic and the largest non-arribada population globally

AbstractKnowledge of the abundance and distribution of species is important for designing and prioritizing conservation and management activities. Despite numerous existing studies on the distribution and status of sea turtles, we still lack knowledge about certain populations, especially in Angola, which is considered to be the southernmost range of nesting sea turtles in the eastern Atlantic. This study provides an overview of the status, size and distribution of the olive ridley sea turtle Lepidochelys olivacea population nesting along the coast of Angola, and its relevance in the context of other olive ridley turtle nesting populations in the Atlantic. Aerial and ground surveys were conducted along 1,410 km of Angolan coastline and daily beach monitoring over 53.9 km of seven permanent study sites at a range of latitudes during 2011–2020. Angola hosts the largest olive ridley turtle nesting population in the Atlantic, and the largest non-arribada population globally. Although the population appeared relatively stable, the pressures from various threats on land (e.g. consumption of turtles and eggs) and at sea (captures in fishing gear) necessitate the development of a comprehensive management plan, improved and strengthened legislation and law enforcement, and a cohesive approach to conserving all sea turtle species in Angola.

Plesiochorus Cymbiformis (Rudolphi, 1819) Looss, 1901 (Digenea: Gorgoderidae) in Olive Ridley Sea Turtles Lepidochelys Olivacea (Eschscholtz, 1829) (Testudines: Chelonidae) from The Brazilian Coast: New Geographic Occurrence and Associated Injuries.

SummaryThe present study reports the first occurrence of Plesiochorus cymbiformis (Digenea: Gorgoderidae), in two Olive Ridley Sea turtles Lepidochelys olivacea (Testudines: Chelonidae), from the states of São Paulo and Sergipe in Brazilian coast. Concerning the Neotropical region, P. cymbiformis has been previously reported in green sea turtles (Chelonia mydas) from Panama and Brazil, in loggerhead sea turtles (Caretta caretta) from Brazil, in hawksbill sea turtles (Eretmochelys imbricata) from Puerto Rico, and in Olive Ridley Sea turtles only in Costa Rica. Lesions resulting from the presence of parasites in the hosts’ urinary bladders are also presented. This is the second report on endoparasites in Olive Ridley sea turtles from Brazil.

Are the uplifted reef beds in North Andaman letting nesting Olive Ridley Sea Turtle Lepidochelys olivacea stranded?

During our survey to understand vegetation colonization, focused on mangroves, in the uplifted reef beds near the Radhanagar creek in North Andaman on 10 February 2021 (Lat: 13°24'40.70"N; Lon: 92°50'57.73"E), we came across four carcasses of Olive Ridley turtles within a 500 m transect. The carcasses were probably a week old and are characterized by the presence of degenerating flesh, and foul smell. The article describes the potential reasons behind turtle mortality and future research needs for the holistic understanding of such incidences.

Relationship between sea surface temperature and the nesting of the Olive Ridley sea turtle Lepidochelys olivacea (Testudines: Cheloniidae) in Gorgona Island, Colombian Pacific

Introduction: Lepidochelys olivacea is the most abundant sea turtle in the Colombian Pacific and oceanographic conditions at the Eastern Tropical Pacific may have an effect on its reproductive behavior Objective: To assess the relationship between reproductive aspects of L. olivacea nesting at Gorgona island and sea surface temperature at local and regional scales. Methods: Monthly mean data of reproductive attributes associated with nesting females, nests, eggs and hatchlings were established using records from Gorgona’s National Natural Park nesting monitoring and were correlated (cross-correlations) with SST of Gorgona island and Panama Bight, and with the temperature variability of the El Niño 1+2, El Niño 3, El Niño 3.4 and El Niño 4 regions, their thermal anomalies, and the ONI and SOI indexes. Significant correlations were included in a Generalized Additive Model. Results: Highest inverse correlation since maximum correlation is 1 was established between visits to the beach, number of nesting females, number of nests, clutch size, incubation days and hatching success and Niño 1+2 region with a lag of 12 months, whereas egg diameter, egg weight, straight carapace length and width and weight of hatchlings were correlated with Niño 4 anomaly, SOI and ONI indexes. It was also found that there is a non-linear tendency to decrease number of nesting females, number of nests, clutch size, egg diameter and egg weight with regional positive anomalies. Conclusions: Nesting attributes of L. olivacea in Gorgona correlate mainly with variations in regional SST, being low at high sea surface temperatures the year prior to nesting (12-month lag).

New records of Planes crabs associated with sea turtles in Africa and adjacent waters

Crabs of the genus Planes (family Grapsidae) live on floating debris and pelagic animals and spend their lives rafting at the surface of the open ocean. Among living substrata, Planes minutus is frequently found associated with sea turtles. However, prior to this study, crabs had never been documented on sea turtles in continental Africa or in the western Indian Ocean. We found P. minutus associated with olive ridley sea turtle Lepidochelys olivacea nesting and foraging/pre-nesting in Gabon, and with loggerhead Caretta caretta and green sea turtle Chelonia mydas foraging off the east coast of South Africa, as well as loggerheads nesting in Cape Verde and loggerheads foraging off Réunion. No crabs were found on nesting loggerheads surveyed in Oman. We integrate these new findings with a review of all known records of Planes–sea turtle interactions in the Atlantic and Indian oceans and the Mediterranean Sea, to better understand the geographic distribution and ecological characteristics of such associations.

Sea turtles support sustainable livelihoods at Ostional, Costa Rica

AbstractOstional in Costa Rica is the second largest nesting site of the olive ridley sea turtle Lepidochelys olivacea, which is categorized as Vulnerable on the IUCN Red List. In Ostional the local community helps maintain the nesting site and collects olive ridley eggs for consumption and trade within Costa Rica. Since its inception in 1987 the egg harvesting project has integrated sea turtle conservation with community development. We assessed the current status of this project in terms of community awareness, dependency, involvement and perceptions, using a household survey and semi-structured interviews with key informants. We also compared some of our findings with those of previous studies at the site, finding that the project has fewer dependents, primary livelihood activities have shifted towards tourism and hospitality, and respondents are more aware about environmental conservation and stewardship. We map outcomes of the project with the Sustainable Livelihoods Framework, and suggest that further capacity building for research and tourism could contribute towards sustaining the turtle population, local livelihoods, and the community-based conservation institution.

<b>The persistence of the Striped Hyena <I>Hyaena hyaena</I> Linnaeus, 1758 (Mammalia: Carnivora: Hyaenidae) as a predator of Olive Ridley Sea Turtle Lepidochelys olivacea Eschscholtz, 1829 (Reptilia: Testudines: Cheloniidae) eggs</b>

A few records of the Striped Hyena Hyaena hyaena, a Near Threatened species, suggest that it can survive along coasts, preying on intertidal fauna. This record updates earlier information about the presence of the Striped Hyena preying on the Rushikulya Olive Ridley Sea Turtle Lepidochelys olivacea mass-nesting beach to show that the hyena persists in this human-dominated landscape. In addition, it provides details of the first direct sighting of the Striped Hyena feeding on sea turtle eggs. The implications of the presence of this predator for conservation and coastal development are discussed.

The influence of oceanographic features on the foraging behavior of the olive ridley sea turtle Lepidochelys olivacea along the Guiana coast

The circulation in the Western Equatorial Atlantic is characterized by a highly dynamic mesoscale activity that shapes the Guiana continental shelf. Olive ridley sea turtles (Lepidochelys olivacea) nesting in French Guiana cross this turbulent environment during their post-nesting migration. We studied how oceanographic and biological conditions drove the foraging behavior of 18 adult females, using satellite telemetry, remote sensing data (sea surface temperature, sea surface height, current velocity and euphotic depth), simulations of micronekton biomass (pelagic organisms) and in situ records (water temperature and salinity). The occurrence of foraging events throughout migration was located using Residence Time analysis, while an innovative proxy of the hunting time within a dive was used to identify and quantify foraging events during dives. Olive ridleys migrated northwestwards using the Guiana current and remained on the continental shelf at the edge of eddies formed by the North Brazil retroflection, an area characterized by low turbulence and high micronekton biomass. They performed mainly pelagic dives, hunting for an average 77% of their time. Hunting time within a dive increased with shallower euphotic depth and with lower water temperatures, and mean hunting depth increased with deeper thermocline. This is the first study to quantify foraging activity within dives in olive ridleys, and reveals the crucial role played by the thermocline on the foraging behavior of this carnivorous species. This study also provides novel and detailed data describing how turtles actively use oceanographic structures during post-nesting migration.

Age and growth of olive ridley sea turtles Lepidochelys olivacea in the main Brazilian nesting ground

Age and growth of olive ridley sea turtles Lepidochelys olivacea in the main Brazilian nesting ground

Olive Ridley Sea TurtleLepidochelys olivacea(Eschscholtz, 1829) from Brazil as a New Host ofPyelosomum cochlearLooss 1899 (Digenea: Pronocephalidae)

Here we present the occurrence of Pyelosomum cochlear Looss 1899 in the urinary bladder of an olive ridley sea turtle Lepidochelys olivacea (Eschscholtz, 1829) from Brazil. This parasite species has previously been reported only from Chelonia mydas from Egypt, the United States (including Puerto Rico), Panama, and Costa Rica. This paper reports the first occurrence of P. cochlear parasitizing L. olivacea and the first occurrence of this parasite in the western South Atlantic.

Defining olive ridley turtle Lepidochelys olivacea management units in Australia and assessing the potential impact of mortality in ghost nets

In Australia, the olive ridley sea turtle Lepidochelys olivacea has received little re - search attention and monitoring. The Australian populations are relatively small and their distri- bution is limited to remote areas in the northern part of the country. Previous global genetic stud- ies of olive ridley populations showed that the Australian breeding population at the McCluer Group of islands, Northern Territory, is genetically distinct from other olive ridley populations breeding in the Indo-Pacific. However, nothing is known about the genetic stock structure among Australian olive ridley rookeries found across northern Australia. High predation of eggs by feral pigs, dogs and monitor lizards Varanus spp. is believed to have severely impacted the number of nesting females at some rookeries. Of particular concern is the small nesting population on the western Cape York Peninsula, and without immediate conservation action this population could face extinction. The results presented here establish that there are at least 2 independent manage- ment units (stocks) of olive ridley turtles nesting in Australia and emphasise the importance of conserving the genetically distinct small breeding population nesting along the western Cape York Peninsula. In addition, results from 44 turtles caught in ghost nets across the Gulf of Carpen- taria revealed that 45% of the haplotypes (32% of all ghost net samples) had not been observed at any rookery in Australia or SE Asia. This research highlights the need for better information on olive ridley population structure in the region and for urgent conservation action for the western Cape York population.

Conservation related insights into the behaviour of the olive ridley sea turtle Lepidochelys olivacea nesting in Oman

We followed the movements of 9 adult female olive ridley turtles Lepidochelys oli- vacea after nesting on Masirah Island, Oman, using satellite tracking. Their post-breeding migra- tions ranged from 85 to 796 km. Three individuals travelled north to foraging grounds in Pakistan, Iran and the United Arab Emirates. The other 6 turtles remained in Omani seas for extended peri- ods (mean ± SD = 171.3 ± 109.4 d; range = 40 to 310 d). These locally resident turtles experienced biannual cooling of sea temperatures due to the effect of the west Arabian Sea upwelling which was not experienced by those that migrated to the north. Indications of disparity in turtle size between foraging locations are identified for the first time in this species. The majority of turtles (8) settled in coastal areas of water depth 100 min) in water warmer than 21°C, which is a feature unique to olive ridleys amongst sea turtles. They dis- played a shift to shorter diving after breeding, indicating increased activity levels. The entire spa- tial footprint of olive ridley dispersal remained within a putative regional management unit (RMU) for this species in the western Indian Ocean, supporting its delineation. We reveal Oman's key role in conserving this demographic unit, with 6 turtles remaining within its national boundary. Our data add to the growing body of evidence that marine turtles show varied migration behav- iours within populations, thus complicating their management.

Mass nesting of olive ridley sea turtles Lepidochelys olivacea at La Escobilla, Mexico: linking nest density and rates of destruction

Olive ridley sea turtles Lepidochelys olivacea exhibit synchronized nesting behavior that affects egg survival through a variety of mechanisms, including intra-specific nest destruc- tion. This activity is difficult to quantify due to the frequency of arribadas (mass nesting events that occur over several days) and temporal overlap of incubation periods. We hypothesized that nest destruction is positively related to cumulative nest density. We quantified these variables through direct observation of nesting by 1293 turtles in 26 plots (each 9 m 2 ) during 2 arribadas at La Escobilla, Mexico, in 2009. Cumulative nest densities ranged from 1 to 8 nests m �2 . The propor- tion of turtles observed destroying eggs was used as a proxy for nest destruction. A total of 5.12 and 23.10% of turtles destroyed eggs in the first and second arribadas, respectively. We used a mixed model logistic regression to determine that the odds of destruction (or the probability that a turtle destroys eggs divided by the probability that she does not) increased 21% for every addi- tional nest per square meter. We could not measure total egg survival as a function of nest density likely due to extreme weather conditions and beetle predation that resulted in 0% hatchling pro- duction over most of the study area in August to October 2009. However, understanding the rela- tionship between nest density and the probability of nest destruction is an important first step toward quantifying density dependence in olive ridleys. We recommend that monitoring plans include standardized measurements of density (nests per square meter) and destruction levels to improve estimates of annual hatchling production.

Reproductive synchrony in a recovering bottlenecked sea turtle population

1. The assessment of species extinction risk has been well established for some time now. Assessing the potential for recovery in endangered species is however much more challenging, because complementary approaches are required to detect reliable signals of positive trends. 2. This study combines genetics, demography and behavioural data at three different time-scales to assess historical and recent population changes and evidence of reproductive synchrony in a small population of olive ridley sea turtle Lepidochelys olivacea. Lepidochelys is considered as the most extraordinary example of reproductive synchrony in reptiles, yet to date, it has only been reported in large populations. 3. Using Bayesian coalescent-based models on microsatellite nuclear DNA variability, we demonstrate that effective population size in olive ridleys nesting in French Guiana has dramatically declined by 99% over the last 20 centuries. This low current population size is further illustrated by the absence of genetic mitochondrial DNA diversity in the present nesting population. Yet, monitoring of nesting sites in French Guiana suggests a possible recovery of the population over the last decade. 4. Satellite telemetry shows that over the first 14 days of their 28-days inter-nesting interval, i.e. when eggs maturation is likely to occur, gravid females disperse over the continental shelf. They then gather together with a striking spatiotemporal consistency close to the nesting site, where they later emerge for their second nesting event. 5. Our results therefore suggest that reproductive synchrony also occurs in small populations. Olive ridleys may ensure this synchrony by adjusting the duration of the second half of their inter-nesting interval prior to landing, possibly through social mediation. 6. Such reproductive synchrony may be related to the maintenance of some species-specific strategy despite former collapse and may contribute to the present population recovery. The gregarious behaviour of reproductive individuals close to shore where human-induced perturbations occur is however a cause for conservation concern for this still poorly known species.

Nomadic behaviour of the highly migratory olive ridley sea turtle Lepidochelys olivacea in the eastern tropical Pacific Ocean

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 13:33-40 (2010) - DOI: https://doi.org/10.3354/esr00314 Nomadic behaviour of the highly migratory olive ridley sea turtle Lepidochelys olivacea in the eastern tropical Pacific Ocean Pamela T. Plotkin* Cornell University, Office of Sponsored Programs, 373 Pine Tree Road, Ithaca, New York 14850, USA *Email: ptp8@cornell.edu ABSTRACT: I studied the post-reproductive migrations of 30 male and female olive ridley sea turtles Lepidochelys olivacea in the eastern tropical Pacific Ocean (ETP) using satellite telemetry. Long-term data revealed that turtles were widely distributed in the pelagic zone from Mexico to Peru and lacked migratory corridors. Turtles migrated long distances, swam continuously, displayed no fidelity to specific feeding habitats, and were nomadic. An El Niño occurred in the middle of the study, and turtle migration patterns changed in response. ETP olive ridleys likely evolved migratory flexibility to adapt to the frequent and unpredictable environmental change characteristic of their large dynamic marine ecosystem. This suggests that ETP olive ridleys may be less vulnerable to the impacts of climate change than other sea turtle species. KEY WORDS: Lepidochelys olivacea · Eastern tropical Pacific · Satellite telemetry · Nomadic · Highly migratory · El Niño Full text in pdf format Supplementary material PreviousNextCite this article as: Plotkin PT (2010) Nomadic behaviour of the highly migratory olive ridley sea turtle Lepidochelys olivacea in the eastern tropical Pacific Ocean. Endang Species Res 13:33-40. https://doi.org/10.3354/esr00314Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 13, No. 1. Online publication date: December 03, 2010 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2010 Inter-Research.

Movements of olive ridley sea turtles Lepidochelys olivacea and associated oceanographic features as determined by improved light-based geolocation

We demonstrate the use of pop-off satellite archival tags (PSAT)-derived geolocations to determine the most probable tracks (MPTs) of olive ridley sea turtles Lepidochelys olivacea off Costa Rica. We use a Kalman filter state-space model (KFSST) that uses light-based longitude and latitude and sea surface temperatures (SST). PSATs placed on 14 turtles remained fixed for an average 53 d (range: 29 to 111 d). The average reduction in longitude and latitude standard deviations was ϕlon = 0.62 and ϕlat = 0.28 between the raw and KFSST-derived MPTs, respectively. Geolocations were linked in time to oceanographic features such as SST and chlorophyll a, as reported by satellite-based sensors. Turtles went in all directions from their respective release points, independent of year and capture type (longline-caught vs. hand-caught). Turtles remained within a SST range between 23.3 and 30.5°C (mean = 27.1°C), with over 75% of all recorded temperatures between 25.0 and 28.0°C. Turtle locations were associated with mean chlorophyll a = 0.37 mg m -3 . MPT data suggest that tur- tles spent a disproportionate amount of time in the general region of the Costa Rica Dome, a nutrient- rich quasi-permanent cyclonic eddy. Taken together, these findings support the increased utility of filtered light-based geolocation data in identifying environmental features characteristic of sea tur- tles' preferred habitat, information which can be useful in managing regional fisheries.

Mortality of olive ridley turtles Lepidochelys olivacea due to incidental capture in fishing nets along the Orissa coast, India

The coastal state of Orissa, India, harbours three important mass-nesting beaches of the olive ridley sea turtle Lepidochelys olivacea. During a survey of sea turtle nesting beaches from December 1993 to May 1994, 5282 dead olive ridleys were counted along the 480 km coastline of Orissa. Almost all the deaths were due to incidental capture in offshore fishing nets. Increased fishing activities in the coastal waters near important sea-turtle nesting beaches pose a serious threat to the survival of this endangered sea turtle. It is therefore suggested that coastal waters adjacent to major sea-turtle nesting beaches be declared as closed areas for commercial fishing activities in order to ensure the sea turtle's long-term survival.

Mortality of olive ridley turtles Lepidochelys olivacea due to incidental capture in fishing nets along the Orissa coast, India

The coastal state of Orissa, India, harbours three important mass-nesting beaches of the olive ridley sea turtle Lepidochelys olivacea. During a survey of sea turtle nesting beaches from December 1993 to May 1994, 5282 dead olive ridleys were counted along the 480 km coastline of Orissa. Almost all the deaths were due to incidental capture in offshore fishing nets. Increased fishing activities in the coastal waters near important sea-turtle nesting beaches pose a serious threat to the survival of this endangered sea turtle. It is therefore suggested that coastal waters adjacent to major sea-turtle nesting beaches be declared as closed areas for commercial fishing activities in order to ensure the sea turtle's long-term survival.