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While most studies assessing the ecological impacts of climate change have examined impacts from warming temperatures, less attention has been given to other parameters such as increased rainfall events. At a nesting rookery in the northern Great Barrier Reef, Australia, we used data loggers to examine the impact of heavy rainfall and shade on the nest temperatures for green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles clutches, which have temperature-dependent sex determination. In the middle of the nesting season (December–March), on 21 January 2019, 125 mm of rain fell over two days, causing the temperature to initially decrease by an average of ~ 3.6 °C in hawksbill turtle nests (n = 18) and ~ 3.5 °C in green turtle nests (n = 9). For shaded clutches during the 20-day cooling period after the rainfall event, we report average nest temperatures of ~ 27.9 °C and ~ 28.2 °C for hawksbill and green turtle clutches respectively, falling well into the male-producing range for sex determination. This was profoundly cooler than the average nest temperatures of clutches without shade and prior to the heavy rainfall, which was ~ 31.3 °C for both species. Extreme rainfall events are predicted to increase around Australia due to climate change but may help counteract impacts of atmospheric warming on sea turtle offspring sex-ratios. Our results also show the potential for artificially cooling nests by applying a combination of shade and irrigation, to counter the expected increases in the feminisation of sea turtle hatchling production worldwide.

Satellite telemetry was used to track inter-nesting, post-nesting, and foraging movements of six green turtles that nested on Bioko Island, Equatorial Guinea at the end of the 2019 nesting season, as well as foraging movements of five green turtles after the 2018 nesting season (n = 11 across two seasons), from the same nesting population. These tracks were fit with a switching state-space model to characterize movements and then analyzed in relation to environmental and anthropogenic factors. Inter-nesting movements of two turtles included separate oceanic loops, in which turtles traveled > 40 km away from nesting beaches. Four complete migrations were observed to two distinct foraging grounds, with two turtles migrating west for an average of 1064 km to the coastal waters of Ghana, and two migrating south for an average of 1563 km to a newly discovered foraging ground in the coastal waters of Angola. All migrations included intermittent foraging at stopover sites, including one period of possible oceanic foraging. Turtles at both foraging grounds maintained distinct core use areas in shallow, near-shore (

Capture–mark–recapture studies that fail to account for the frequency and dynamics of marker loss risk generating biased demographic estimates. In this study, we used permanent multilocus genotypes (i.e., “genetic tags”) and a new enhanced tag loss model to quantify the tag loss dynamics for both passive integrated transponder (PIT) and Inconel metal tags applied to loggerhead turtles (Caretta caretta) nesting on Wassaw Island, GA USA. Our results indicate that tag loss is most likely to occur within the nesting season in which tags were applied and is maximal just after tagging (maximum likelihood estimates): 0.00098 PIT tags day−1 and 0.007 Inconel tags day−1. After that, PIT tag loss was negligible and Inconel tag loss remained low but constant at 0.00028 tags day−1, such that after 5 years, the probability of losing one PIT tag was 0.06 and losing at least one Inconel tag was 0.46. The use of genetic tags in this study makes these the first truly accurate estimates of PIT and Inconel tag loss for marine turtles, and the new model of tag loss described herein represents an important advancement in the analytical methods used to estimate and compare tag loss dynamics.

Sea turtles are migratory animals that travel from foraging grounds to specifc nesting beaches every few years and that, therefore, can be infuenced by oceanographic conditions in several diferent habitats. We assessed how sea surface temperature (SST) and chlorophyll-α (Chl-α) within both internesting and foraging areas infuence the nesting abundance, phenology and duration of internesting periods of the green turtles (Chelonia mydas) that nest at Cabuyal, Northwest Costa Rica. Specifcally, we compared (1) SST and Chl-α in foraging areas to the nesting abundance and median nesting date (MND) registered on the beach over seven nesting seasons and (2) SST in internesting habitats to the observed internesting period (OIP) (number of days between successful nesting events) and the MND. Nesting abundance was strongly correlated to Chl-α concentrations at the main foraging area during the February preceding the nesting season. However, we found no signifcant efect of SST or Chl-α in either foraging or internesting habitats on the MND. Mean SST values in the internesting habitats and OIP were negatively correlated and were highly variable both between and within years. Oceanographic conditions appear to strongly infuence OIP and nesting abundance, but not the nesting phenology of green turtles in this area. The complex nature of the efect of oceanographic conditions on reproduction of the East Pacifc green turtle suggests uncertainty in how this species will respond to climate change Las tortugas marinas son animales migratorios que viajan desde áreas de alimentación hasta playas de anidación específicas cada pocos años y que, por lo tanto, pueden verse influenciadas por las condiciones oceanográficas en varios hábitats diferentes. Evaluamos cómo la temperatura de la superficie del mar (TSM) y la clorofila-α (Chl-α) dentro de las áreas de anidación y forrajeo influyen en la abundancia de anidación, la fenología y la duración de los períodos de anidación de las tortugas verdes (Chelonia mydas) que anidan en Cabuyal, Costa Noroeste. Rica. Específicamente, comparamos (1) SST y Chl-α en áreas de forrajeo con la abundancia de anidación y la fecha mediana de anidación (MND) registrada en la playa durante siete temporadas de anidación y (2) SST en hábitats de internidación con el período de internidación observado (OIP) (número de días entre eventos de anidación exitosos) y el MND. La abundancia de anidación estuvo fuertemente correlacionada con las concentraciones de Chl-α en el área principal de alimentación durante el febrero anterior a la temporada de anidación. Sin embargo, no encontramos ningún efecto significativo de la SST o Chl-α en los hábitats de alimentación o de anidación en la MND. Los valores medios de SST en los hábitats inter-nidos y OIP se correlacionaron negativamente y fueron muy variables tanto entre como dentro de los años. Las condiciones oceanográficas parecen influir fuertemente en la OIP y la abundancia de anidación, pero no en la fenología de anidación de las tortugas verdes en esta área. La naturaleza compleja del efecto de las condiciones oceanográficas sobre la reproducción de la tortuga verde del Pacífico Oriental sugiere incertidumbre sobre cómo responderá esta especie al cambio climático. Universidad Nacional, Costa Rica Cape Eleuthera Island School, Eleuthera, Bahamas Goldring-Gund Marine Biology Station, Costa Rica Escuela de Ciencias Biológicas

Baseline hematologic and plasma biochemical analytes provide insight into wildlife health. In recent years, blood analytes have been used to infer foraging strategies and nutritional status of female sea turtles of different species during nesting season in an effort to determine if turtles at this life stage are capital breeders that forage little to none during nesting season. These changes in foraging during nesting have not been documented in loggerhead sea turtles (Caretta caretta). The objective of this study was to evaluate correlations between hematologic, plasma chemistry, immune function, and antioxidative analytes of female loggerhead turtles during nesting season to determine evidence of reduced foraging. We found that chloride tended to increase, while total protein, various plasma protein fractions (pre-albumin, alpha-1-globulins, beta-globulins, total globulins), total white blood cells, superoxide dismutase, reactive oxygen species, iron, and triglycerides decreased over the course of nesting season. These results suggest that loggerhead turtles rely on fat stores accumulated on foraging grounds to fuel their energetic costs during nesting. Our results also indicate alterations in hemodynamics, metabolism, and antioxidative capacity due to reduced foraging and high energy efforts of nesting, which lend further insight into the physiologic dynamics and catabolic state of sea turtles during nesting season.

Epibionts can serve as valuable ecological indicators, providing information about the behaviour or health of the host. The use of epibionts as indicators is, however, often limited by a lack of knowledge about the basic ecology of these ‘hitchhikers’. This study investigated the growth rates of a turtle barnacle, Chelonibia testudinaria, under natural conditions, and then used the resulting growth curve to estimate the barnacle’s age. Repeat morphometric measurements (length and basal area) on 78 barnacles were taken, as host loggerhead turtles (Caretta caretta) laid successive clutches at Mon Repos, Australia, during the 2015/16 nesting season. Barnacles when first encountered ranged in size from 3.7 to 62.9 mm, and were recaptured between 12 and 56 days later. Fitting the growth measurements of these barnacles to a von Bertalanffy growth curve, we estimated the age of these barnacles as a function of their size. Length growth rate decreased over time in a non-linear fashion, while basal area growth rate showed a linear relationship with age. The average estimated age of barnacles at first capture was approximately 6 months (barnacle length 30.3 ± 1.8 mm). The largest and oldest individual had a length of 62.9 mm when first measured, and was estimated to be 642 days old. The finding that C. testudinaria may live for up to 2 years, means that these barnacles may serve as interesting ecological indicators over this period. In turn, this information may be used to better understand the movement and habitat use of their sea turtle hosts, ultimately improving conservation and management of these threatened animals.

Nest counts are often used as indices for nesting female abundance in marine turtle monitoring, but accurately interpreting nest count trends requires context on the scale of demographic connectivity and estimates of reproductive parameters. Weak nest site fidelity (NSF) relative to the scale of tagging effort may bias parameter estimates. The reproductive ecology of Northern Recovery Unit (NRU) loggerhead turtles (Caretta caretta) was assessed through subpopulation-scale genetic capture-recapture via clutch sampling from approximately 1000 km of coastline from Georgia to Maryland, USA (30.75–38.06°N and 75.24–81.45°W). Of 20,682 clutches recorded from 2010 to 2012, 20,222 sampled clutches were assigned to 5684 unique females through microsatellite genotyping. Approximately 73% of females detected laying multiple clutches deposited them within a 20-km span, suggesting the possibility of demographic structuring across NRU rookeries that warrants further investigation. Estimated clutch frequencies (ECF) generated from open robust design modeling were 4.28 (4.02–4.54) in 2010, 4.63 (4.45–4.80) in 2011, and 4.57 (4.28–4.77) in 2012, and were significantly higher than observed clutch frequencies. ECF generated from single-island data were biased low by 23–50% relative to those from regional genetic tagging. Among females that nested at least once on a physical tagging beach, 54% also nested elsewhere, with 81% of these “permanently” emigrating during the nesting season. This pattern of relatively strong NSF, but distributed across multiple nearby islands, confounded modeling of detection in single-island datasets and highlights the need for regional coverage for generating robust estimates of demographic parameters for marine turtles.

The marine habitat use of olive ridley sea turtles (Lepidochelys olivacea) from northeastern Brazil was analyzed via stable isotope analysis (SIA). Blood (red blood cells and serum), epidermis and scute samples from 46 nesting females were collected for SIA of carbon (δ 13C) and nitrogen (δ 15N) to infer the habitats used at distinct time windows. Such approach is possible because each tissue reflects consumer’s diet at different time scales due to different tissue turnover time. Prey representative of both neritic and oceanic realms was used as endpoints. Differences in the residence time of δ 13C and δ 15N among samples indicated a shift from oceanic feeding grounds to neritic habitats before nesting or effects of prolonged fasting on stable isotope values. However, two individuals seemed to have used neritic feeding habitats for longer timespans before the nesting period. Stable isotope mixing models demonstrated high individual variability, suggesting the variable use of non-breeding grounds. Moreover, serum indicated that olive ridleys might feed during the nesting season, most likely opportunistically on discards from trawl fisheries. Finally, through correlations of stable isotope values among tissues, this study provides equations for the conversion and adequate comparison between values from different tissues. Therefore, the habitats used by olive ridley sea turtles from Brazil are vast, encompassing both oceanic and neritic habitats, where they encounter pelagic longline and trawl fisheries, respectively. The high individual variability in the population results in turtles experiencing distinct and variable threats during their annual cycle.

Understanding geospatial linkages is critical to the development of appropriate management and conservation strategies for migratory species. Stable isotope analysis is a powerful tool that is performed routinely across taxa to unravel migratory connectivity. Marine turtles are a highly migratory and widely distributed taxon, but are largely studied at breeding areas. Isotopic values of several slow turnover rate tissues have been used to identify often distant foraging areas. However, as more isotopic data from various tissues become available, the relationships between tissues need to be calculated to permit meta-analyses to elucidate isotopic patterns across broader spatiotemporal scales. We used several commonly collected tissues (blood, skin, fresh eggs and unhatched eggs) collected simultaneously from loggerhead turtles (Caretta caretta) to develop a common currency for stable isotope analysis studies conducted on the nesting beach. We found highly significant relationships between the tissue signatures (r 2 ranged from 0.83 to 0.96) and developed equations to convert isotopic values from one tissue to another. We examined inter- and intra-clutch isotopic variability and found that a single sampling event over the 4-month nesting season adequately defined the loggerhead female foraging area. Consequently, we propose using unhatched eggs as a common currency in stable isotope studies of nesting loggerheads. Unhatched eggs represent a noninvasive and nondestructive method that enables more extensive (both numerically and spatially) sampling. Given similar physiologies, analogous relationships might be derived in other sea turtle species.

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.

The hawksbill marine turtle (Eretmochelys imbricata) is listed on the IUCN Red List as critically endangered but little is known about its demography to support robust diagnosis of population trends. Moreover, adult female hawksbills do not nest each year due to environmentally mediated physiological constraints and this skipped breeding behaviour presents a major challenge in data collection and for estimating demographic parameters from such data sets. We estimated demographic parameters such as survival and breeding probabilities for a major Indo-Pacific nesting hawksbill population using a capture-mark-recapture (CMR) study and a multistate open robust design statistical modelling approach, which accounts for breeding omission and the staggered arrival and departure of nesters during each season. Our study used CMR histories for 413 nesting hawksbills tagged on Varanus Island (Western Australia) over a 4-month sampling period each year for 20 austral summer nesting seasons between 1987 and 2007. The estimated annual survival probability for these nesting hawksbills was constant over the 20 years at ca. 0.947 (95% CI: 0.91–0.97), which is encouragingly high for a population associated with industry. The estimated annual conditional nesting (breeding) probability for female hawksbills that had skipped the previous nesting season was time-specific ranging from 0.07 to 0.29 (mean = 0.18, CV = 41.3%), which presumably reflects the interaction between turtle physiology and in-water habitat quality. The mean conditional probability of breeding again having skipped 2 prior consecutive nesting seasons was ca. 0.83 (95% CI: 0.73–0.89), indicating a high frequency of breeding season omission. The annual nesting probability for females that had nested the previous season was 0, reflecting known obligate skipped breeding (reproductive omission) that is characteristic of hawksbill populations in response to high energy demands of vitellogenesis and breeding migration. These are the first estimates of annual survival and state-dependent breeding probabilities for any Indo-Pacific hawksbill stock that provide a basis for developing a better understanding of regional population dynamics for this critically endangered species.

Reproductive output of leatherback turtles (Dermochelys coriacea) is affected by the stochastic nature of emergence success. Average emergence success of nests at Playa Grande, Costa Rica was 0.38 ± 0.27. Incubation temperature affected development of leatherback turtle eggs and emergence of hatchlings from the nest. We found that high temperatures reduced hatching success and emergence rate and increased embryonic mortality both early and late during incubation at Playa Grande. There was a temporal effect on emergence success that resulted in more hatchlings being produced at the beginning of the season, because of higher emergence success, than toward the end. Likewise, production of hatchlings varied from year to year. The average annual reproductive output was 252 ± 141 hatchlings per female. The 2005–2006 nesting season had the highest emergence success and produced the greatest number of hatchlings per female compared to the 2004–2005 (+120%) and 2006–2007 (+41%) seasons. However, average clutch size (62 ± 10) and clutch frequency (9.45 ± 1.63), were not different among years. Turtles that had nested a high number of years exhibited greater clutch frequency and arrived earlier to nest than turtles that had nested in fewer numbers of years. Nesting when environmental conditions favor high developmental success and emergence rate may constitute an advantageous reproductive strategy.

Variation in environmental conditions at a foraging area or at a nesting rookery has the potential to impact reproductive output of green sea turtles (Chelonia mydas) by affecting food resources or the nesting substrate. In this paper we test whether turtles‘ physiological characteristics reflect variation in relevant environmental conditions. We did this by profiling metabolic and hormonal markers among (1) non-vitellogenic females from three different foraging areas and (2) nesting females from different rookeries and breeding seasons. Among the non-vitellogenic females, the highest plasma triglyceride concentrations (4.29 mmol/l) and the lowest plasma cholesterol concentrations (1.27 mmol/l) were found in non-vitellogenic females residing in Moreton Bay during the El Nino year of 1997. Furthermore, during 1997, these Moreton Bay females had higher plasma triglyceride and lower cholesterol concentrations than those recorded in non-vitellogenic females foraging at Heron Reef (triglyceride 1.22 mmol/l and cholesterol 4.53 mmol/l) and Shoalwater Bay (triglyceride 1.69 mmol/l and cholesterol 3.50 mmol/l) in the same year. Among nesting turtles, those nesting at Raine Island had low mean plasma triglyceride concentrations during the high density 1996 nesting season. For those nesting at Heron Island, the mean triglyceride concentrations were the lowest during the 1997 nesting season. This is the first time that hormone and metabolic markers have been used in concert to compare the physiological condition of nesting and foraging sea turtles and its relationship with the environment. Collectively, our data indicate that variation in the environmental conditions at both foraging and nesting areas are reflected at a physiological level. Moreover, our study indicates that turtles feeding during El Nino years are able to attain higher levels of body condition, and that physiological data combined with morphometric data is a useful proxy for assessing the condition of turtles in foraging areas.

The green turtle (Chelonia mydas) nesting population at Tortuguero, Costa Rica, is the largest nesting aggregation in the Atlantic, by at least an order of magnitude. Previous mitochondrial DNA (mtDNA) surveys based on limited sampling (n = 41) indicated low genetic diversity and low gene flow with other Caribbean nesting colonies. Furthermore, a survey of nuclear DNA diversity invoked the possibility of substructure within the Tortuguero rookery. To evaluate these characteristics, mtDNA control region sequences were determined for green turtles nesting at Tortuguero in 2001 (n = 157) and 2002 (n = 235). The increased sample revealed three additional haplotypes; five haplotypes are now known for Tortuguero female green turtles. Analyses of molecular variance indicated that there was no significant spatial population structure along the 30-km nesting beach. In addition, no temporal population structure was detected either between the two nesting seasons or within the nesting season. As a result of the larger sample size and additional haplotypes, estimates of genetic separation among Caribbean nesting colonies have changed and the concordance of phylogenetic and phylogeographic patterns reported in the past for green turtles in the Greater Caribbean has weakened. The five haplotypes from Tortuguero represent 36% of the haplotypes identified in green turtle nesting aggregations in the Greater Caribbean and 17% of the haplotypes known to occur in nesting or foraging aggregations in the Greater Caribbean. Haplotype diversity (0.16) and nucleotide diversity (0.0034) for the Tortuguero population are substantially lower than those for the combined rookeries in the Greater Caribbean (0.44 and 0.0078, respectively). Although comprehensive evaluation of regional genetic diversity requires nuclear DNA data, our study indicates that conserving genetic diversity in Caribbean green turtles will require careful management of the smaller rookeries in addition to the Tortuguero rookery.

We collected data on plasma levels of testosterone+5a-dihydrotestosterone (T+DHT) and corticosterone (CORT) from adult female green sea turtles (Chelonia mydas) from southern Queensland during distinct stages of their reproductive cycle. Those females capable of breeding in a given year had elevated plasma steroid levels (T+DHT 0.91 +/- 0.08; CORT 1.05 +/- 0.29 ng/ml), associated with follicular development, until courtship began in October. At the beginning of the nesting season in November plasma levels of 2 CORT were related to when the female first nested (r(2) = 0.06; F = 10.45; P = 0.01). However, they were not correlated with the number of clutches a female laid in that season (F = 3.65; P = 0.08). We repeatedly sampled 23 turtles over the nesting season and profiled changes in steroids immediately following oviposition of each clutch. Levels of T+DHT (range 0.41-0.58 ng/ml) and CORT (range 2.13-2.81 ng/ml) were similar through the early stages of the nesting season and inter-nesting period, and declined to near basal levels (T+DHT 0.37 +/- 0.03 and CORT 1.85 +/- ng/ml) following the last clutch for the season. Steroid hormone levels were also low (T+DHT 0.38 +/- 0.16; CORT 0.46 +/- 0.21 ng/ml) in four independent post-breeding (atretic) females; samples for these females were taken at a time when body condition was presumably at the lowest for the season. Subtle changes in the nesting environment, such as variation in nesting habitat or the time of night that nesting occurred, were associated with a small and slow CORT increase. We suggest CORT is increased in nesting females to assist in lipid transfer to prepare the ovarian follicles and/or the reproductive organs for ovulation.

The nesting season of the green turtle, Chelonia mydas on Wan-An Island, Peng-Hu Archipelago, Taiwan extended from early June to early October in both 1992 and 1993. Turtles nested on 9 of the 11 beaches on the island. The average inter-nesting interval was 14.9 d. A close relationship between the first reemergence time and the tidal cycle was found in the present study. The mean straight carapace length of the adult female was 96.6 cm. Female turtles produced from one to nine egg clutches; the average clutch size was 113 eggs. The mean egg size was 46.9 mm in diameter and 22.7 g in weight. The average incubation period was 49.3 d. The sediment characteristics of the beaches on the island are well within the incubation requirements for green turtle nesting. The average hatching success was 70%, but was lower in the artificial nest. The average size for hatchlings was 46.9 mm in straight carapace length and 22.7 g in body weight. The health of the hatchling is influenced by the adult female size, the nesting depth and the precipitation during incubation.