Caretta Research Project

Box Elder, United States

Caretta Research Project

Box Elder, United States
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Shamblin B.M.,University of Georgia | Dodd M.G.,Conservation Way | Williams K.L.,Caretta Research Project | Frick M.G.,Caretta Research Project | And 2 more authors.
Molecular Ecology Resources | Year: 2011

Tagging studies on nesting beaches are commonly used to estimate nesting frequency, remigration interval and nesting population size for marine turtle rookeries. Estimates of these demographic parameters from tagging projects may be biased because of the small scale of tagging efforts relative to female nest site fidelity and the logistical difficulty of intercepting all nesting females. Therefore, alternative and supplemental means of individual identification of nesting females are required. We demonstrate that maternal nuclear microsatellite DNA can be isolated from unincubated eggshells of the loggerhead sea turtle (Caretta caretta) through comparison of DNA extracted from 59 eggs collected within 15 h of oviposition and DNA derived from skin samples from respective nesting females. Scorable microsatellite genotypes were produced in 897 of 994 (90.2%) single-locus egg amplifications attempted. Among eggs from known females, 730 of 748 (97.6%) single-locus, egg-derived genotypes matched the respective skin-derived genotypes. Allelic dropout was the most common type of error, followed by the presence of nonmaternal, presumably paternal, alleles. Genotypes derived from unincubated eggshells permit individual assignment of nests and therefore demographic parameter estimates for loggerhead turtle nesting populations, despite genotyping errors that require further optimization. Although sampling unincubated eggs is destructive, this technique is noninvasive to nesting females and is applicable in marine turtle population genetics studies when individual resolution is required but direct interception of nesting females is undesirable or logistically infeasible. © 2010 Blackwell Publishing Ltd.


Hawkes L.A.,University of Exeter | Hawkes L.A.,Bangor University | Witt M.J.,University of Exeter | Broderick A.C.,University of Exeter | And 10 more authors.
Diversity and Distributions | Year: 2011

Aim Although satellite tracking has yielded much information regarding the migrations and habitat use of threatened marine species, relatively little has been published about the environmental niche for loggerhead sea turtles Caretta caretta in north-west Atlantic waters. Location North Carolina, South Carolina and Georgia, USA. Methods We tracked 68 adult female turtles between 1998 and 2008, one of the largest sample sizes to date, for 372.2±210.4days (mean±SD). Results We identified two strategies: (1) 'seasonal' migrations between summer and winter coastal areas (n=47), although some turtles made oceanic excursions (n=4) and (2) occupation of more southerly 'year-round' ranges (n=18). Seasonal turtles occupied summer home ranges of 645.1km2 (median, n = 42; using α-hulls) predominantly north of 35° latitude and winter home ranges of 339.0km2 (n=24) in a relatively small area on the narrow shelf off North Carolina. We tracked some of these turtles through successive summer (n=8) and winter (n=3) seasons, showing inter-annual home range repeatability to within 14.5km of summer areas and 10.3km of winter areas. For year-round turtles, home ranges were 1889.9km2. Turtles should be tracked for at least 80days to reliably estimate the home range size in seasonal habitats. The equivalent minimum duration for 'year-round' turtles is more complex to derive. We define an environmental envelope of the distribution of North American loggerhead turtles: warm waters (between 18.2 and 29.2°C) on the coastal shelf (in depths of 3.0-89.0m). Main conclusions Our findings show that adult female loggerhead turtles show predictable, repeatable home range behaviour and do not generally leave waters of the USA, nor the continental shelf (<200m depth). These data offer insights for future marine management, particularly if they were combined with those from the other management units in the USA. © 2011 Blackwell Publishing Ltd.


Leblanc A.M.,Georgia Southern University | Drake K.K.,Georgia Southern University | Williams K.L.,Caretta Research Project | Frick M.G.,Caretta Research Project | And 2 more authors.
Chelonian Conservation and Biology | Year: 2012

We examined loggerhead nest temperatures and hatchling sex ratios in an effort to more accurately predict hatchling sex ratios produced from 2 barrier islands in the northern management unit (Blackbeard Island National Wildlife Refuge and Wassaw National Wildlife Refuge, Georgia, United States) from 2000 to 2004. Temperature data loggers were placed into 169 nests to monitor incubation temperatures. Average critical period temperatures ranged from 26.3°C to 33.2°C (mean ± SE, 29.2°±0.1°C) and indicated seasonal variation in sex ratios. The sex of 669 hatchlings found dead in nests was histologically evaluated (n212 nests; 1490 nests/yr). The sex ratios varied from 0 to 100 female per nest (n153 hatchlings/nest) and average sex ratio for all nests ranged from 55.5 female in 2003 to 85.4 female in 2002. In addition to monitoring nest temperature, 10 hatchlings per nest were euthanized to verify sex during 2003 on Blackbeard Island National Wildlife Refuge (n10 nests) and 2004 on Wassaw National Wildlife Refuge (n9 nests). Sex ratios were analyzed by using an advanced statistical program for evaluating temperature-dependent sex determination and indicated a 11 temperature (temperature that produces a 11 sex ratio) of 28.9°C. We offer an equation for predicting northern management unit hatchling loggerhead sex ratios by using critical period temperature and tested its validity. Sixteen of 18 nests (n = 10 hatchlings/nest) showed no significant difference between the predicted sex ratios based on the equation vs. sex ratios obtained through histology. Our data indicated that rookery beaches north of Florida are important areas for the production and recruitments of male loggerhead hatchlings into the overall western North Atlantic Ocean and nests deposited earliest within a nesting season are primary contributors of male turtles. We suggest that nest monitoring programs grant such nests particular protection to increase their survivability and the production of hatchlings. © 2012 Chelonian Research Foundation.


Vander Zanden H.B.,University of Florida | Vander Zanden H.B.,University of Utah | Pfaller J.B.,University of Florida | Pfaller J.B.,Caretta Research Project | And 9 more authors.
Marine Biology | Year: 2014

Diet items and habitat constitute some of the environmental resources that may be used differently by individuals within a population. Long-term fidelity by individuals to particular resources exemplifies individual specialization, a phenomenon that is becoming increasingly recognized across a wide range of species. Less is understood about the consequences of such specialization. Here, we investigate the effects of differential foraging ground use on reproductive output in 183 loggerhead sea turtles (Caretta caretta) nesting at Wassaw Island, Georgia (31.89°N, 80.97°W), between 2004 and 2011 with resulting possible fitness effects. Stable isotope analysis was used to assign the adult female loggerheads to one of three foraging areas in the Northwest Atlantic Ocean. Our data indicate that foraging area preference influences the size, fecundity, and breeding periodicity of adult female loggerhead turtles. We also found that the proportion of turtles originating from each foraging area varied significantly among the years examined. The change in the number of nesting females across the years of the study was not a result of uniform change from all foraging areas. We develop a novel approach to assess differential contributions of various foraging aggregations to changes in abundance of a sea turtle nesting aggregation using stable isotopes. Our approach can provide an improved understanding of the influences on the causes of increasing or decreasing population trends and allow more effective monitoring for these threatened species and other highly migratory species. © 2013 Springer-Verlag Berlin Heidelberg.


Pfaller J.B.,Caretta Research Project | Pfaller J.B.,University of Florida | Bjorndal K.A.,University of Florida | Chaloupka M.,University of Queensland | And 3 more authors.
PLoS ONE | Year: 2013

Assessments of population trends based on time-series counts of individuals are complicated by imperfect detection, which can lead to serious misinterpretations of data. Population trends of threatened marine turtles worldwide are usually based on counts of nests or nesting females. We analyze 39 years of nest-count, female-count, and capture-mark-recapture (CMR) data for nesting loggerhead turtles (Caretta caretta) on Wassaw Island, Georgia, USA. Annual counts of nests and females, not corrected for imperfect detection, yield significant, positive trends in abundance. However, multistate open robust design modeling of CMR data that accounts for changes in imperfect detection reveals that the annual abundance of nesting females has remained essentially constant over the 39-year period. The dichotomy could result from improvements in surveys or increased within-season nest-site fidelity in females, either of which would increase detection probability. For the first time in a marine turtle population, we compare results of population trend analyses that do and do not account for imperfect detection and demonstrate the potential for erroneous conclusions. Past assessments of marine turtle population trends based exclusively on count data should be interpreted with caution and re-evaluated when possible. These concerns apply equally to population assessments of all species with imperfect detection. © 2013 Pfaller et al.


Kaufman T.J.,University of Florida | Pajuelo M.,University of Florida | Bjorndal K.A.,University of Florida | Bolten A.B.,University of Florida | And 4 more authors.
Conservation Physiology | Year: 2014

Carbon and nitrogen stable isotope (δ13C and δ15N) analysis has been used to elucidate foraging and migration behaviours of endangered sea turtle populations. Isotopic analysis of tissue samples from nesting females can provide information about their foraging locations before reproduction. To determine whether loggerhead (Caretta caretta) eggs provide a good proxy for maternal isotope values, we addressed the following three objectives: (i) we evaluated isotopic effects of ethanol preservation and lipid extraction on yolk; (ii) we examined the isotopic offset between maternal epidermis and corresponding egg yolk and albumen tissue δ13C and δ15N values; and (iii) we assessed the accuracy of foraging ground assignment using egg yolk and albumen stable isotope values as a proxy for maternal epidermis. Epidermis (n = 61), albumen (n = 61) and yolk samples (n = 24) were collected in 2011 from nesting females at Wassaw Island, GA, USA. Subsamples from frozen and ethanol-preserved yolk samples were lipid extracted. Both lipid extraction and ethanol preservation significantly affected yolk δ13C, while δ15N values were not altered at a biologically relevant level. The mathematical corrections provided here allow for normalization of yolk δ13C values with these treatments. Significant tissue conversion equations were found between δ13C and δ15N values of maternal epidermis and corresponding yolk and albumen. Finally, the consistency in assignment to a foraging area was high (up to 84%), indicating that these conversion equations can be used in future studies where stable isotopes are measured to determine female foraging behaviour and trophic relationships by assessing egg components. Loggerhead eggs can thus provide reliable isotopic information when samples from nesting females cannot be obtained. © The Author 2014.


Pfaller J.B.,University of Florida | Pfaller J.B.,Caretta Research Project | Alfaro-Shigueto J.,ProDelphinus | Alfaro-Shigueto J.,University of Exeter | And 8 more authors.
Marine Biology | Year: 2014

Studies that incorporate information from habitat-specific ecological interactions (e.g., epibiotic associations) can reveal valuable insights into the cryptic habitat-use patterns and behavior of marine vertebrates. Sea turtles, like other large, highly mobile marine vertebrates, are inherently difficult to study, and such information can inform the implementation of conservation measures. The presence of epipelagic epibionts, such as the flotsam crab Planes major, on sea turtles strongly suggests that neritic turtles have recently occupied epipelagic habitats (upper 200 m in areas with >200 m depth) and that epipelagic turtles spend time at or near the surface. We quantified the effects of turtle species, turtle size, and habitat (neritic or epipelagic) on the frequency of epibiosis (F 0) by P. major on sea turtles in the Pacific Ocean. In neritic habitats, we found that loggerhead (F 0 = 27.6 %) and olive ridley turtles (F 0 = 26.2 %) host crabs frequently across a wide range of body sizes, and green turtles almost never host crabs (F 0 = 0.7 %). These results suggest that loggerheads and olive ridleys display variable/flexible epipelagic-neritic transitions, while green turtles tend to transition unidirectionally at small body sizes. In epipelagic habitats, we found that loggerheads host crabs (F 0 = 92.9 %) more frequently than olive ridleys (F 0 = 50 %) and green turtles (F 0 = 38.5 %). These results suggest that epipelagic loggerheads tend to spend more time at or near the surface than epipelagic olive ridleys and green turtles. Results of this study reveal new insights into habitat-use patterns and behavior of sea turtles and display how epibiont data can supplement data from more advanced technologies to gain a better understanding of the ecology of marine vertebrates during cryptic life stages. © 2014 Springer-Verlag Berlin Heidelberg.


PubMed | University of Florida and Caretta Research Project
Type: Journal Article | Journal: Conservation physiology | Year: 2016

Carbon and nitrogen stable isotope ((13)C and (15)N) analysis has been used to elucidate foraging and migration behaviours of endangered sea turtle populations. Isotopic analysis of tissue samples from nesting females can provide information about their foraging locations before reproduction. To determine whether loggerhead (Caretta caretta) eggs provide a good proxy for maternal isotope values, we addressed the following three objectives: (i)we evaluated isotopic effects of ethanol preservation and lipid extraction on yolk; (ii)we examined the isotopic offset between maternal epidermis and corresponding egg yolk and albumen tissue (13)C and (15)N values; and (iii)we assessed the accuracy of foraging ground assignment using egg yolk and albumen stable isotope values as a proxy for maternal epidermis. Epidermis (n=61), albumen (n=61) and yolk samples (n=24) were collected in 2011 from nesting females at Wassaw Island, GA, USA. Subsamples from frozen and ethanol-preserved yolk samples were lipid extracted. Both lipid extraction and ethanol preservation significantly affected yolk (13)C, while (15)N values were not altered at a biologically relevant level. The mathematical corrections provided here allow for normalization of yolk (13)C values with these treatments. Significant tissue conversion equations were found between (13)C and (15)N values of maternal epidermis and corresponding yolk and albumen. Finally, the consistency in assignment to a foraging area was high (up to 84%), indicating that these conversion equations can be used in future studies where stable isotopes are measured to determine female foraging behaviour and trophic relationships by assessing egg components. Loggerhead eggs can thus provide reliable isotopic information when samples from nesting females cannot be obtained.


Lasala J.A.,Georgia Southern University | Lasala J.A.,Florida Atlantic University | Harrison J.S.,Georgia Southern University | Williams K.L.,Caretta Research Project | Rostal D.C.,Georgia Southern University
Ecology and Evolution | Year: 2013

Characterization of a species mating systems is fundamental for understanding the natural history and evolution of that species. Polyandry can result in the multiple paternity of progeny arrays. The only previous study of the loggerhead turtle (Caretta caretta) in the USA showed that within the large peninsular Florida subpopulation, multiple paternity occurs in approximately 30% of clutches. Our study tested clutches from the smaller northern subpopulation for the presence of multiple paternal contributions. We examined mothers and up to 20 offspring from 19.5% of clutches laid across three nesting seasons (2008-2010) on the small nesting beach on Wassaw Island, Georgia, USA. We found that 75% of clutches sampled had multiple fathers with an average of 2.65 fathers per nest (1-7 fathers found). The average number of fathers per clutch varied among years and increased with female size. There was no relationship between number of fathers and hatching success. Finally, we found 195 individual paternal genotypes and determined that each male contributed to no more than a single clutch over the 3-year sampling period. Together these results suggest that the operational sex ratio is male-biased at this site. Our study uses microsatellites in conjunction with exclusion analysis of multiple paternity to establish the number of males contributing to a nesting population of loggerhead sea turtles. We suggest that the operational sex ratio is male biased at this site. © 2013 The Authors.


Frick M.G.,Caretta Research Project | Zardus J.D.,The Citadel
Journal of Crustacean Biology | Year: 2010

An analysis of museum specimens reveals that reports of the chelonophilic barnacle Cylindrolepas darwiniana are misidentifications of the similar turtle barnacle Platylepas decorata. As a result, contemporary collections from loggerhead and hawksbill sea turtles represent the first report of this turtle barnacle since its description nearly a century ago. Novel morphological characters that clearly distinguish C. darwiniana from other turtle barnacles have been ascertained from the recent specimens and are reported. © 2010 The Crustacean Society.

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