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Scott A Eckert - One of the best experts on this subject based on the ideXlab platform.
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satellite tracked movements of female Dermochelys coriacea from southeastern brazil
Endangered Species Research, 2011Co-Authors: Antonio De Padua Almeida, Scott A Eckert, Milagros Lopezmendilaharsu, Soraya Christina Bruno, Juarez T Scalfoni, Bruno Giffoni, Joao C A ThomeAbstract:Four female leatherback sea turtles Dermochelys coriacea were satellite tracked from the southeastern coast of Brazil (3 from nesting beaches in the state of Espirito Santo, and 1 recovered from a driftnet off the coast of the state of Sao Paulo), representing the first study of movements of leatherbacks nesting on Brazilian grounds. The results suggest that during the internesting period, leatherbacks may disperse up to 160 km from the nesting beach using an area of 4400 km 2 . Tracking also revealed shared feeding areas in southern South America, comprising Brazilian, Uruguayan, and Argentinean waters, and highlighted important interactions with fish- eries along nesting, migratory, and feeding habitats. The presence in migratory/foraging areas of turtles from at least 2 different nesting populations from both sides of the South Atlantic Ocean supports the concept that management efforts for this species must incorporate a broad regional perspective.
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high use oceanic areas for atlantic leatherback sea turtles Dermochelys coriacea as identified using satellite telemetered location and dive information
Marine Biology, 2006Co-Authors: Scott A EckertAbstract:The movements and behavior of nine female leatherback sea turtles, Dermochelys coriacea (L.) were monitored for up to 370 days from their nesting beaches on the Caribbean island of Trinidad between 1995 and 2004 using satellite-linked time and depth recorders. During the inter-nesting period (typically March–July) turtles ranged widely, but frequented the area around Galera Point on the NE corner of Trinidad. Diving depths were typically 26 min) as the turtles left the Caribbean, but became very shallow (>50 m) and short at high latitudes. Between mid-October and mid-November, the turtles left high latitudes for a presumed foraging area in the Mauritania upwelling where they resided until their tracking records ended. Diving remained relatively shallow. It is proposed that movements of these turtles from one foraging area to another are driven by the opportunity to forage in areas of distinct oceanic structure which serve to concentrate their gelatinous prey (e.g., salps, Scyphomedusae, Siphonophora) either at or below the surface.
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Migratory and reproductive movements of male leatherback turtles (Dermochelys coriacea)
Marine Biology, 2005Co-Authors: Michael C. James, Scott A Eckert, Ransom A. MyersAbstract:The biology of the endangered leatherback turtle ( Dermochelys coriacea ) at sea is poorly understood. As research has been almost exclusively limited to studies of nesting females, the movements of male turtles and the timing and location of mating activity have remained unknown. We report on the first deployments of satellite tags on male leatherbacks. Male migration to and residency in waters adjacent low-latitude nesting beaches in the western Atlantic suggest that this is where mating occurs, and return migration to these areas reveals male fidelity for breeding sites. Rate of travel decreased markedly after arriving in coastal breeding areas, where males remained for up to 96 days before assuming northward migrations. The initiation of these northward migrations coincided with peak nesting activity in adjacent nesting colonies. Data from satellite-linked time-depth recorders attached to two males revealed diel dive patterns in breeding areas and marked differences in diving behaviour between migratory and breeding periods in one turtle. When male turtles were in waters adjacent nesting colonies, their movements differed from those reported for nesting females, with females ranging farther from shore. Our results suggest that male leatherbacks may be vulnerable to entanglement in coastal fishing gear in waters adjacent nesting beaches.
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swim speed and movement patterns of gravid leatherback sea turtles Dermochelys coriacea at st croix us virgin islands
The Journal of Experimental Biology, 2002Co-Authors: Scott A EckertAbstract:Swim speed, dive behavior and movements were recorded for seven female leatherback sea turtles ( Dermochelys coriacea Vandelli 1761) during a single internesting interval near St Croix in the US Virgin Islands. Modal speeds ranged from 0.56 to 0.84 m s-1, maximum speed range 1.9-2.8 m s-1. Turtles swam continuously throughout the day and night. There were two swim-speed patterns; the most common was slightly U-shaped, with high speeds at the initiation and conclusion of the dive, and the less common was continuous high-speed swimming. The U-shaped speed patterns were coincident with vertical diving by the turtles, while the second pattern occurred most frequently during the daytime, with the turtle swimming within 2 m of the surface. This latter swim behavior appeared to be designed to maximize efficiency for long-distance travel. The hypothesis that leatherbacks rest or bask at midday during their internesting interval is refuted by this study.
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distribution of juvenile leatherback sea turtle Dermochelys coriacea sightings
Marine Ecology Progress Series, 2002Co-Authors: Scott A EckertAbstract:Data on the location, date, sea temperature, and turtle size for 98 small (<145 cm) leatherback sea turtles Dermochelys coriacea demonstrate that leatherbacks less than 100 cm in carapace length occur only in waters warmer than 26°C.
Michael C. James - One of the best experts on this subject based on the ideXlab platform.
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At-sea biology and movements of leatherback turtles, Dermochelys coriacea, in the northwest Atlantic.
2020Co-Authors: Michael C. JamesAbstract:The endangered leatherback turtle, Dermochelys coriacea , has the broadest distribution of any sea turtle; however, research on this species has principally been limited to studies of the biology of nesting females, their internesting behaviour, and more recently, their post-nesting movements. To hasten this species' recovery, research on the biology of leatherbacks and the threats they face in other areas of their range is needed. In collaboration with the fishing industry, I developed a field research program to study leatherbacks in waters off eastern Canada, where turtles aggregate seasonally to forage on gelatinous plankton.
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VALIDATION OF ULTRASOUND AS A NONINVASIVE TOOL TO MEASURE SUBCUTANEOUS FAT DEPTH IN LEATHERBACK SEA TURTLES (Dermochelys coriacea)
Journal of Zoo and Wildlife Medicine, 2016Co-Authors: Heather S Harris, Scott R. Benson, Michael C. James, Brian A Stacy, Thierry M Work, Kelly J. Martin, Pierre-yves Daoust, Paul M. Rist, George H. Balazs, Jeffrey A. SeminoffAbstract:Abstract Leatherback turtles (Dermochelys coriacea) undergo substantial cyclical changes in body condition between foraging and nesting. Ultrasonography has been used to measure subcutaneous fat as an indicator of body condition in many species but has not been applied in sea turtles. To validate this technique in leatherback turtles, ultrasound images were obtained from 36 live-captured and dead-stranded immature and adult turtles from foraging and nesting areas in the Pacific and Atlantic oceans. Ultrasound measurements were compared with direct measurements from surgical biopsy or necropsy. Tissue architecture was confirmed histologically in a subset of turtles. The dorsal shoulder region provided the best site for differentiation of tissues. Maximum fat depth values with the front flipper in a neutral (45–90°) position demonstrated good correlation with direct measurements. Ultrasound-derived fat measurements may be used in the future for quantitative assessment of body condition as an index of health...
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pleated turtle escapes the box shape changes in Dermochelys coriacea
The Journal of Experimental Biology, 2011Co-Authors: John Davenport, Thomas K. Doyle, Jeanyves Georges, Virginie Plot, Michael C. JamesAbstract:SUMMARY Typical chelonians have a rigid carapace and plastron that form a box-like structure that constrains several aspects of their physiology and ecology. The leatherback sea turtle, Dermochelys coriacea, has a flexible bony carapace strengthened by seven longitudinal ridges, whereas the plastron is reduced to an elliptical outer bony structure, so that the ventrum has no bony support. Measurements of the shell were made on adult female leatherbacks studied on the feeding grounds of waters off Nova Scotia (NS) and on breeding beaches of French Guiana (FG) to examine whether foraging and/or breeding turtles alter carapace size and/or shape. NS turtles exhibited greater mass and girth for a given curved carapace length (CCL) than FG turtles. Girth:CCL ratios rose during the feeding season, indicating increased girth. Measurements were made of the direct (straight) and surface (curved) distances between the medial longitudinal ridge and first right-hand longitudinal ridge (at 50% CCL). In NS turtles, the ratio of straight to curved inter-ridge distances was significantly higher than in FG turtles, indicating distension of the upper surfaces of the NS turtles between the ridges. FG females laid 11 clutches in the breeding season; although CCL and curved carapace width remained stable, girth declined between each nesting episode, indicating loss of mass. Straight to curved inter-ridge distance ratios did not change significantly during the breeding season, indicating loss of dorsal blubber before the onset of breeding. The results demonstrate substantial alterations in size and shape of female D. coriacea over periods of weeks to months in response to alterations in nutritional and reproductive status.
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Pleated turtle escapes the box – shape changes in Dermochelys coriacea
The Journal of Experimental Biology, 2011Co-Authors: John Davenport, Thomas K. Doyle, Jeanyves Georges, Virginie Plot, Michael C. JamesAbstract:SUMMARY Typical chelonians have a rigid carapace and plastron that form a box-like structure that constrains several aspects of their physiology and ecology. The leatherback sea turtle, Dermochelys coriacea, has a flexible bony carapace strengthened by seven longitudinal ridges, whereas the plastron is reduced to an elliptical outer bony structure, so that the ventrum has no bony support. Measurements of the shell were made on adult female leatherbacks studied on the feeding grounds of waters off Nova Scotia (NS) and on breeding beaches of French Guiana (FG) to examine whether foraging and/or breeding turtles alter carapace size and/or shape. NS turtles exhibited greater mass and girth for a given curved carapace length (CCL) than FG turtles. Girth:CCL ratios rose during the feeding season, indicating increased girth. Measurements were made of the direct (straight) and surface (curved) distances between the medial longitudinal ridge and first right-hand longitudinal ridge (at 50% CCL). In NS turtles, the ratio of straight to curved inter-ridge distances was significantly higher than in FG turtles, indicating distension of the upper surfaces of the NS turtles between the ridges. FG females laid 11 clutches in the breeding season; although CCL and curved carapace width remained stable, girth declined between each nesting episode, indicating loss of mass. Straight to curved inter-ridge distance ratios did not change significantly during the breeding season, indicating loss of dorsal blubber before the onset of breeding. The results demonstrate substantial alterations in size and shape of female D. coriacea over periods of weeks to months in response to alterations in nutritional and reproductive status.
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behaviour of leatherback sea turtles Dermochelys coriacea during the migratory cycle
Proceedings of The Royal Society B: Biological Sciences, 2005Co-Authors: Michael C. James, Ransom A. Myers, Andrea C OttensmeyerAbstract:Leatherback sea turtles, Dermochelys coriacea, undertake broad oceanic movements. While satellite telemetry has been used to investigate the post-nesting behaviour of female turtles tagged on tropical nesting beaches, long-term behavioural patterns of turtles of different sexes and sizes have not been described. Here we investigate behaviour for 25 subadult and adult male and female turtles satellite-tagged in temperate waters off Nova Scotia, Canada. Although sex and reproductive condition contributed to variation in migratory patterns, the migratory cycle of all turtles included movement between temperate and tropical waters. Marked changes in rates of travel, and diving and surfacing behaviour, accompanied southward movement away from northern foraging areas. As turtles approached higher latitudes the following spring and summer, they assumed behaviours consistent with regular foraging activity and eventually settled in coastal areas off Canada and the northeastern USA. Behavioural patterns corresponding to various phases of the migratory cycle were consistent across multiple animals and were repeated within individuals that completed return movements to northern waters. We consider the potential biological significance of these patterns, including how turtle behaviour relates to predator avoidance, thermoregulation and prey distribution.
Justin R Perrault - One of the best experts on this subject based on the ideXlab platform.
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nesting leatherback sea turtle Dermochelys coriacea packed cell volumes indicate decreased foraging during reproduction
Marine Biology, 2016Co-Authors: Debra L Miller, Justin R Perrault, Annie PagekarjianAbstract:Leatherback sea turtles (Dermochelys coriacea) are hypothesized to be capital breeders, whereby they forage little to none during the nesting season. The capital breeding hypothesis can be tested in marine turtles using physiological measures of health, which are much less expensive than studies that use satellite tags or other physiological monitoring equipment to make inferences about behavior and foraging status during the nesting season. In this study, we analyzed packed cell volumes (PCVs), a simple and inexpensive, hematologic health parameter, in nesting leatherback turtles from St. Croix, U.S. Virgin Islands (17°40′40″N, 64°54′0″W) across the nesting season (April–July 2009) in an effort to determine foraging status. We found that PCV in nesting females significantly declined using two longitudinal measures: nest number and level of reproductive effort. We also found that PCVs of remigrants were significantly higher in comparison with neophytes, suggesting that experience in reproductive activities (e.g., migration, breeding, nesting) might increase foraging success on feeding grounds. Lastly, we found that leatherbacks with a greater reproductive output had significantly higher PCVs. While the northwest Atlantic leatherback population is evaluated as least concern by the IUCN, Pacific leatherbacks are critically endangered. The assumed behaviors of turtles from this study provide insight into reproductive strategies and energy reserves in all marine turtle populations. Thus, the results presented here are applicable to (1) veterinarians, rehabilitation facilities, and conservationists and (2) other more vulnerable marine turtle populations.
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mercury and selenium ingestion rates of atlantic leatherback sea turtles Dermochelys coriacea a cause for concern in this species
Marine Environmental Research, 2014Co-Authors: Justin R PerraultAbstract:Abstract Bodily accumulation of certain toxic elements can cause physiologic harm to marine organisms and be detrimental to their health and survival. The leatherback sea turtle (Dermochelys coriacea) is a broadly distributed marine reptile capable of consuming hundreds of kilograms of gelatinous zooplankton each day. Little is known about toxicants present in these prey items. Specifically, mercury is a known neurotoxin with no known essential function, while selenium detoxifies bodily mercury, but can be toxic at elevated concentrations. I collected 121 leatherback prey items (i.e., gelatinous zooplankton) from known leatherback foraging grounds and sampled the esophagus and stomach contents of stranded turtles. All samples were analyzed for total mercury and selenium. Additionally, two prey items and three liver samples were analyzed for methylmercury, the most toxic form of the element. Total mercury concentrations in prey items ranged from 0.2 to 17 ppb, while selenium concentrations ranged from
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assessment of mercury and selenium concentrations in tissues of stranded leatherback sea turtles Dermochelys coriacea
Journal of herpetological medicine and surgery, 2012Co-Authors: Justin R PerraultAbstract:Abstract The impact of mercury (Hg) and selenium (Se) compounds on wildlife health is an issue of concern, especially because anthropogenic practices (e.g., fossil fuel combustion, metal processing) release these trace elements and their compounds into the environment where they become incorporated into food chains. Little is known about the concentrations of these elements in tissues (other than in blood) of most wild reptiles, especially for pelagic species. The purpose of this study was to document Hg and Se concentrations in leatherback sea turtles, Dermochelys coriacea. To assess Hg and Se concentrations in leatherbacks, multiple tissue samples (whole blood, enteric contents from the small intestine, feces, yolked follicles, liver, and salt gland) were collected from dead, stranded male and female leatherbacks that were assigned to three life stage classes (juvenile, subadult, adult) identified at gross necropsy. The tissues were tested for Hg and Se concentrations. The liver exhibited the highest co...
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pathologic findings in hatchling and posthatchling leatherback sea turtles Dermochelys coriacea from florida
Journal of Wildlife Diseases, 2009Co-Authors: Debra L Miller, Sreekumari Rajeev, Jeanette Wyneken, Justin R Perrault, Douglas R Mader, James Weege, Charles A BaldwinAbstract:In an attempt to identify critical health issues affecting the survival of endangered leatherback sea turtles (Dermochelys coriacea), a prospective study was conducted in several dead-in-nest hatchlings and captive posthatchlings to examine pathologic changes and presence of pathogenic microorganisms. Numerous histopathologic changes were identified. Although bacterial etiologies were suspected in deaths of captive individuals, a single causative organism was not identified but rather, a mixed population of bacterial flora was cultured. Muscle degeneration observed in most samples implicates a potential environmental factor in species survival and needs future investigation.
James R Spotila - One of the best experts on this subject based on the ideXlab platform.
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reassessment of the leatherback turtle Dermochelys coriacea nesting population at parque nacional marino las baulas costa rica effects of conservation efforts
Chelonian Conservation and Biology, 2007Co-Authors: Pilar Santidrian Tomillo, Frank V Paladino, Richard D Reina, Rotney Piedra, Elizabeth Velez, James R SpotilaAbstract:ABSTRACT The number of leatherback turtles (Dermochelys coriacea) nesting at Parque Marino Las Baulas declined precipitously in the 15 years that we monitored the population (1988–1989 to 2003–2004). We estimate that the annual survival rate of adults was 0.78 (95% CI: 0.75–0.80) and that mortality rates for juveniles and subadults in the ocean appear to be double those of a stable population. The proportion of hatchlings produced from deposited eggs increased since the park was established as a result of conservation practices. Because the number of nesting females decreased, the overall production of hatchlings per season declined but was much greater than would be expected without protection efforts. There were similar numbers of hatchlings leaving the beaches of Las Baulas in 1998–2003, with 68 to 188 nesting females under the current conservation regime as there were in 1988–1989 with ca. 1500 nesting females and no park. Female leatherback turtles that nest at Las Baulas have a high level of exchang...
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size growth and reproductive output of adult female leatherback turtles Dermochelys coriacea
Endangered Species Research, 2004Co-Authors: Edwin R Price, Bryan P Wallace, James R Spotila, Frank V Paladino, Richard D Reina, Rotney Piedra, Elizabeth VelezAbstract:Leatherback turtles Dermochelys coriacea exhibit superlative measures of size, growth, and fecundity among reptiles, yet factors affecting these variables remain poorly studied. We inves- tigated the relationships between the leatherback's variable remigration interval and measures of growth and fecundity by analyzing 8 years of data from a population of females nesting at Parque Nacional Marino Las Baulas, Costa Rica. We hypothesized that variation in the remigration interval was due to tradeoffs with seasonal fecundity (clutch size and estimated clutch frequency) or growth rate over the interval. Nesting females grew an average of 0.2 cm yr -1 (range: -1.5 to 2 cm yr -1 ) in standard curved carapace length and 0.2 cm yr -1 (range: -1.6 to 1.7 cm yr -1 ) in curved carapace width, with smaller turtles growing significantly faster than larger ones. The small adult growth rates observed indicate that size differences within and between populations are not good indicators of age. Major differences in body size among turtles within a population appear to be set during the juvenile and subadult portions of female leatherbacks' lives. Remigration interval did not correlate with either growth or measured indices of seasonal fecundity. Because delayed remigration did not result in enhanced growth or measured indices of reproduction, variability of environmental condi- tions might instead determine the length of the remigration interval and thus the overall reproduc- tive output during a female's lifetime.
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biotic and abiotic factors affect the nest environment of embryonic leatherback turtles Dermochelys coriacea
Physiological and Biochemical Zoology, 2004Co-Authors: Bryan P Wallace, James R Spotila, Paul R Sotherland, Richard D Reina, Bryan F Franks, Frank V PaladinoAbstract:Abstract Clutches of leatherback turtles, Dermochelys coriacea, have lower hatching success than those of other sea turtles, but causes of high embryonic mortality are unknown. We measured characteristics of clutches along with spatial and temporal changes in PO2 and temperature during incubation to determine the extent to which they affected the developmental environment of leatherback embryos. Minimum PO2 in nests decreased as both the total number and mass of metabolizing embryos increased. Increases in both the number and mass of metabolizing embryos caused an increase in maximum nest temperature. However, neither PO2 nor temperature was correlated with hatching success. Our measurements of relatively high nest PO2 (lowest 17.1 kPa or 16.9% O2) indicate that hypoxia apparently does not cause the low hatching success of leatherback clutches. Oxygen partial pressure increased and temperature decreased from the center toward the periphery of leatherback nests. We inferred from these measurements that pos...
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low reproductive success of leatherback turtles Dermochelys coriacea is due to high embryonic mortality
Biological Conservation, 2004Co-Authors: Barbara Bell, James R Spotila, Frank V Paladino, Richard D ReinaAbstract:We examined the mechanism responsible for low reproductive success in leatherback turtles (Dermochelys coriacea) at Playa Grande, Costa Rica: low egg fertilization versus high rates of embryonic death. Leatherbacks at this beach had a high rate of fertility (X=93.3%� 2.5%, n=819). We incubated 10 eggs from every clutch encountered of 19 females during 3 months of the 1998– 1999 nesting season. Fertility rate of some females decreased during the nesting season, but overall was high. Detection of fertility was difficult using standard methods because fertility rates cannot be determined accurately from nests excavated after hatching because of egg decomposition. Removal and incubation of eggs from nests provided a better estimate. Embryonic death, particularly in the beginning of incubation before embryos are visible to the unaided eye, was the cause of low hatching success in this population. Hatching success increased with increasing fertility and differed between females, with some mothers having 71–81% success and others 23–32%. Embryonic death and not low egg fertility drives poor recruitment at Playa Grande. Improved conservation of this species at Playa Grande will require a better understanding of the mechanism behind embryonic death. # 2003 Elsevier Ltd. All rights reserved.
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the leatherback turtle Dermochelys coriacea exhibits both polyandry and polygyny
Molecular Ecology, 2002Co-Authors: J L Crim, James R Spotila, Michael P Oconnor, Richard D Reina, Loretta D Spotila, Charlene J Williams, Frank V PaladinoAbstract:: The leatherback turtle (Dermochelys coriacea) is an endangered species, and world-wide populations are declining. To understand better the mating structure of this pelagic and fragile species, we investigated paternity in nearly 1000 hatchlings from Playa Grande in Parque Marino Nacional Las Baulas, Costa Rica. We collected DNA samples from 36 adult female leatherbacks and assessed allele frequency distributions for three microsatellite loci. For 20 of these 36 females, we examined DNA from hatchlings representing multiple clutches, and in some cases assessed up to four successive clutches from the same female. We inferred paternal alleles by comparing maternal and hatchling genotypes. We could not reject the null hypothesis of single paternity in 12 of 20 families (31 of 50 clutches), but we did reject the null hypothesis in two families (eight of 50 clutches). In the remaining six families, the null hypothesis could not be accepted or rejected with certainty because the number of hatchlings exhibiting extra nonmaternal alleles was small, and could thus be a result of mutation or sample error. Successive clutches laid by the same female had the same paternal allelic contribution, indicating sperm storage or possibly monogamy. None of 20 females shared the same three-locus genotype whereas there were two instances of shared genotypes among 17 inferred paternal three-locus genotypes. We conclude that both polyandry and polygyny are part of the mating structure of this leatherback sea turtle population.
Marc Girondot - One of the best experts on this subject based on the ideXlab platform.
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On the occurrence of Leatherback Turtles Dermochelys coriacea (VANDELLI, 1761), in Tunisian waters (Central Mediterranean Sea) (Testudines: Dermochelydae) Zum Vorkommen der Lederschildkröte, Dermochelys coriacea (VANDELLI, 1761) in den Gewässern vor
2020Co-Authors: Sami Karaa, Marc Girondot, Imed Jribi, Abderrahmen Bouain, Mohamed Nejmeddine BradaAbstract:A total of 51 records of the Leatherback Turtle, Dermochelys coriacea (VANDELLI, 1761) from Tunisian waters during 1907-2011, are reviewed based upon published literature and present records. Most measured females and males were adult (curve carapace length, CL > 145 cm). Findings occurred throughout the year, mostly in the central and southern study zones. However, more turtles were observed in the south during the warm period of the year possibly related to the abundance of jellyfishes during that season. Thirty-six out of 51 records (70.58 %) derived from fishery bycatch; gillnets are the dominant threat to leatherbacks in the region. The relatively high frequency of the Leatherback coincides with an increased presence of other jellyfish consumers, such as the sunfish Mola mola. Systematic monitoring and Leatherback data collection is necessary to increase the knowledge on this species’ distribution, behavior and feeding in Tunisian waters.
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nesting estimation and analysis of threats for critically endangered leatherback Dermochelys coriacea and endangered olive ridley lepidochelys olivacea marine turtles nesting in congo
Oryx, 2009Co-Authors: Marieclelia Godgenger, Nathalie Breheret, Karine Ndamite, Alexandre Girard, Marc GirondotAbstract:Six marine turtle species are reported from the coastal waters of the Republic of the Congo. Among them, nesting by the Critically Endangered leatherback Dermochelys coriacea and Endangered olive ridley Lepidochelys olivacea marine turtles occurs annually from September to April on Congolese beaches. We developed a methodology to model the nesting season of marine turtles and apply it to the time series of nest counts for six nesting beaches monitored over 2–4 years. There is a peak of nesting activity in early January for leatherback turtles and early December for olive ridley turtles. We show a decline of olive ridley nests during this period whereas leatherback nesting increased, and propose that differential threats for these two species explain such a contrasted pattern.
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estimating clutch frequency in the sea turtle Dermochelys coriacea using stopover duration
Marine Ecology Progress Series, 2006Co-Authors: Philippe Rivalan, Marc Girondot, Roger Pradel, Remi Choquet, Annecaroline PrevotjulliardAbstract:When direct counts are not possible, relative population size indices, based on animal activity (e.g. number of tracks, burrows, feces, calls per unit area), are sometimes the only tools avail- able to investigate population size variations over time. In sea turtles, the number of clutches laid on a nesting beach in a particular season is commonly used as a relative index of population density. The factor of proportionality that links the relative index and population density is the number of clutches annually laid per female per season or clutch frequency. At Awa:la-Ya:lima:po Beach, French Guiana (South America), we estimated clutch frequency in the sea turtle Dermochelys coriacea using cap- ture-recapture monitoring over an 8 yr period (1995 to 2003, 1997 excluded). We compared 2 meth- ods: (1) Estimated Clutch Frequency (ECF), where Observed Clutch Frequency (OCF) was corrected by taking account for intermediate missed nests, and (2) Total Clutch Frequency (TCF) derived from recent advances in capture-recapture methodologies that were initially developed to estimate stopover duration in migratory animals. Compared to the first method, the latter enabled estimation of the time spent before first capture and after the last capture, as well as the capture probability. Mean annual clutch frequency derived from stopover duration was considerably higher than ECF (respectively 2.38 and 7.01 clutches female -1 yr -1 ). In nesting sites where survey effort is low and vari- able over years, using capture-recapture data analysis might enhance the reliability of conclusions about population size in marine turtles.
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impact of density dependent nest destruction on emergence success of guianan leatherback turtles Dermochelys coriacea
Animal Conservation, 2006Co-Authors: Stephane Caut, Vincent Hulin, Marc GirondotAbstract:To assess the impact of nest covering on a leatherback turtle Dermochelys coriacea nesting beach in French Guiana, we used field study data and a modelling approach. Field results showed that the covering of a pre-existing nest by a new one causes the destruction of the older nest under some conditions of time and covering area, and almost always causes the destruction of the new nest. We then used field results to parameterize a theoretical model of the nesting beach. This allowed us to obtain a ‘critical carrying capacity for the beach’: the number of nests deposited for which the number of successful nests is maximum; when this number increases, the number of successful nests decreases. With these results, we then concluded that density-dependent nest destruction plays a role in the functioning of the nesting beach. These results are essential for our understanding of nest-site selection at the scale of the beach and its consequences.
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Impact of density‐dependent nest destruction on emergence success of Guianan leatherback turtles (Dermochelys coriacea)
Animal Conservation, 2006Co-Authors: Stephane Caut, Vincent Hulin, Marc GirondotAbstract:To assess the impact of nest covering on a leatherback turtle Dermochelys coriacea nesting beach in French Guiana, we used field study data and a modelling approach. Field results showed that the covering of a pre-existing nest by a new one causes the destruction of the older nest under some conditions of time and covering area, and almost always causes the destruction of the new nest. We then used field results to parameterize a theoretical model of the nesting beach. This allowed us to obtain a ‘critical carrying capacity for the beach’: the number of nests deposited for which the number of successful nests is maximum; when this number increases, the number of successful nests decreases. With these results, we then concluded that density-dependent nest destruction plays a role in the functioning of the nesting beach. These results are essential for our understanding of nest-site selection at the scale of the beach and its consequences.