Understanding contaminant exposure risks in nesting Loggerhead sea turtle populations

Queensland loggerhead turtle nest numbers at Mon Repos (MR) indicate population recovery that doesn't occur at Wreck Island (WI). Previous research illustrated that MR and WI turtles forage in different locations, potentially indicating risks differences. Blood, scute, and egg were collected from turtles nesting at MR and WI, with known foraging sites (from concurrent studies). Trace element and organic contaminants were assessed via acid digestion and in vitro cytotoxicity bioassays, respectively. WI turtles had significantly higher scute uranium and blood molybdenum compared to MR turtles, and arsenic was higher in WI turtles foraging north and MR turtles foraging south. Egg and blood titanium, manganese, cadmium, barium, lead, and molybdenum, and scute and egg selenium and mercury significantly correlated. Blood (75 %) extracts produced significant toxicity in vitro in turtle fibroblast cells. In conclusion, reducing chemical exposure at higher risk foraging sites would likely benefit sea turtles and their offspring.

Non-targeted proteomics reveals altered immune response in geographically distinct populations of green sea turtles (Chelonia mydas)

All seven species of sea turtle are facing increasing pressures from human activities that are impacting their health. Changes in circulating blood proteins of an individual, or all members of a population, can provide an early indicator of adverse health outcomes. Non-targeted measurement of all detectable proteins in a blood sample can indicate physiological changes. In the context of wildlife toxicology, this technique can provide a powerful tool for discovering biomarkers of chemical exposure and effect. This study presents a non-targeted examination of the protein abundance in sea turtle plasma obtained from three geographically distinct foraging populations of green turtles (Chelonia mydas) on the Queensland coast. Relative changes in protein expression between sites were compared, and potential markers of contaminant exposure were investigated. Blood plasma protein profiles were distinct between populations, with 85 out of the 116 identified proteins differentially expressed (p < 0.001). The most strongly dysregulated proteins were predominantly acute phase proteins, suggestive of differing immune status between the populations. The highest upregulation of known markers of immunotoxicity, such as pentraxin fusion and complement factor h, was observed in the Moreton Bay turtles. Forty-five different organohalogens were also measured in green turtle plasma samples as exposure to some organohalogens (e.g., polychlorinated biphenyls) has previously been identified as a cause for immune dysregulation in marine animals. The few detected organohalogens were at very low (pg/mL) concentrations in turtles from all sites, and are unlikely to be the cause of the proteome differences observed. However, the changes in protein expression may be indicative of exposure to other chemicals or environmental stressors. The results of this study provide important information about differences in protein expression between different populations of turtles, and guide future toxicological and health studies on east-Australian green sea turtles.

Age-specific growth and maturity estimates for the flatback sea turtle (Natator depressus) by skeletochronology

To address a major knowledge gap for flatback sea turtles (Natator depressus), a species endemic to Australia and considered ‘Data Deficient’ for IUCN Red List assessment, we present the first-ever skeletochronology-derived age and growth rate estimates for this species. Using a rare collection of bone samples gathered from across northern Australia, we applied skeletochronology and characterized the length-at-age relationship, established baseline growth rates from the hatchling to adult life stages, and produced empirical estimates of age-at- and size-at-sexual-maturation (ASM, SSM). We analyzed humeri from 74 flatback sea turtles ranging in body size from 6.0–96.0 cm curved carapace length (CCL), and recovered from Western Australia (n = 48), Eastern Australia (n = 13), central Australia (n = 8; Northern Territory n = 3, the Gulf of Carpentaria n = 5), and unknown locations (n = 5). We identified the onset of sexual maturity for 29 turtles, based on rapprochement growth patterns in the bones. Estimates for ASM ranged from 12.0 to 23.0 years (mean: 16.3 ± 0.53 SE), SSM ranged from 76.1 to 94.0 cm CCL (mean: 84.9 ± 0.90 SE), and maximum observed reproductive longevity was 31 years for a 45-year old male flatback. Growth was modeled as a smoothing spline fit to the size-at-age relationship and at the mean SSM (84.9 cm CCL) corresponded with a spline-predicted maturity age of 18 years (95% CI: 16 to 24), while mean nesting sizes reported in the literature (86.4 to 94 cm CCL) corresponded to estimated ages of 24+ years. A bootstrapped von Bertalanffy growth model was also applied and showed consistencies with the spline curve, yielding an estimated upper size limit, L_inf, at 89.2 ± 0.04 cm (95% CI: 85.5 to 95.9 cm) with the intrinsic growth rate parameter, k, at 0.185 ± 0.0004 (0.16 to 0.22); at the same mean SSM (84.9 cm CCL) the estimated ASM was 16.3 ± 0.05 years (95% CI: 12.8 to 27.7 years). Lastly, four of the samples analyzed were collected from deceased adult females that had previous sizes known from on-going mark/recapture studies at nesting sites in Western Australia. The paired CCL data (measured at nesting and back-calculated) did not significantly differ (p = 0.875). This first skeletochronology study for flatback sea turtles generates valuable empirical estimates for ongoing conservation and management efforts.

How well do embryo development rate models derived from laboratory data predict embryo development in sea turtle nests?

Development rate of ectothermic animals varies with temperature. Here we use data derived from laboratory constant temperature incubation experiments to formulate development rate models that can be used to model embryonic development rate in sea turtle nests. We then use a novel method for detecting the time of hatching to measure the in situ incubation period of sea turtle clutches to test the accuracy of our models in predicting the incubation period from nest temperature traces. We found that all our models overestimated the incubation period. We hypothesize three possible explanations which are not mutually exclusive for the mismatch between our modeling and empirically measured in situ incubation period: (1) a difference in the way the incubation period is calculated in laboratory data and in our field nests, (2) inaccuracies in the assumptions made by our models at high incubation temperatures where there is no empirical laboratory data, and (3) a tendency for development rate in laboratory experiments to be progressively slower as temperature decreases compared with in situ incubation.

We determined the hatching time in sea turtle nests and compared those with hatching times predicted from nest temperature traces. We found that nest temperature traces overestimated hatching time.

Temporal changes in chemical contamination of green turtles (Chelonia mydas) foraging in a heavily industrialised seaport

Port Curtis, a major shipping port, has undergone significant expansion in the last decade, with plans for further development into the future. These activities may result in an increase of contaminant concentrations, threatening local wildlife including sea turtles. This study used a species-specific in vitro bioassay to examine spatial and temporal differences in exposure to, and effects of, organic contaminants in green sea turtles foraging in Port Curtis. Blood was collected from 134 green sea turtles (Chelonia mydas) from five locations in the port over four years. Organic contaminants were extracted from blood, and the cytotoxicity of the extracts to primary green sea turtle cells was assessed. Results indicated spatially similar chemical contamination throughout Port Curtis, at levels significant to sea turtle health, and with signs that chemical contamination may be increasing over time. These results can provide valuable information on the health of green turtles as further development occurs.

Influence of short-term temperature drops on sex-determination in sea turtles

All sea turtles exhibit temperature-dependent sex-determination, where warmer temperatures produce mostly females and cooler temperatures produce mostly males. As global temperatures continue to rise, sea turtle sex-ratios are expected to become increasingly female-biased, threatening the long-term viability of many populations. Nest temperatures are dependent on sand temperature, and heavy rainfall events reduce sand temperatures for a brief period. However, it is unknown whether these short-term temperature drops are large and long enough to produce male hatchlings. To discover if short-term temperature drops within the sex-determining period can lead to male hatchling production, we exposed green and loggerhead turtle eggs to short-term temperature drops conducted in constant temperature rooms. We dropped incubation temperature at four different times during the sex-determining period for a duration of either 3 or 7 days to mimic short-term drops in temperature caused by heavy rainfall in nature. Some male hatchlings were produced when exposed to temperature drops for as little as 3 days, but the majority of male production occurred when eggs were exposed to 7 days of lowered temperature. More male hatchlings were produced when the temperature drop occurred during the middle of the sex-determining period in green turtles, and the beginning and end of the sex-determining period in loggerhead turtles. Inter-clutch variation was evident in the proportion of male hatchlings produced, indicating that maternal and or genetic factors influence male hatchling production. Our findings have management implications for the long-term preservation of sea turtles on beaches that exhibit strongly female-biased hatchling sex-ratios.

Combining analytical and in vitro techniques for comprehensive assessments of chemical exposure and effect in green sea turtles (Chelonia mydas)

Sea turtle populations foraging in coastal areas adjacent to human activity can be exposed to numerous chemical contaminants for long periods of time. For trace elements, well-developed, sensitive and inexpensive analytical techniques remain the most effective method for assessing exposure in sea turtles. However, there are many thousands more organic contaminants present in sea turtles, often at low levels as complex mixtures. Recently developed species-specific in vitro bioassays provide an effective means to identify the presence, and effect of, organic chemicals in sea turtles. This study used a combination of chemical analysis and effects-based bioassays to provide complementary information on chemical exposure and effects for three green turtle foraging populations (Chelonia mydas) in southern Queensland, Australia. Blood was collected from foraging sub-adult green turtles captured in Moreton Bay, Hervey Bay, and Port Curtis. Twenty-six trace elements were measured in whole blood using ICP-MS. Organic contaminants in turtle blood were extracted via QuEChERS and applied to primary green turtle skin fibroblast cell in vitro assays for two toxicity endpoints; cytotoxicity and oxidative stress. The trace element analysis and bioassay results indicated site-specific differences between foraging populations. In particular, turtles from Moreton Bay, a heavily populated coastal embayment, had pronounced cytotoxicity and oxidative stress from organic blood extracts, and elevated concentrations of Cs, Ag, and Zn relative to the other sites. Incorporating traditional chemical analysis with novel effects-based methods can provide a comprehensive assessment of chemical risk in sea turtle populations, contributing to the conservation and management of these threatened species.

Post-nesting movements and feeding ground distribution by the hawksbill turtle (Eretmochelys imbricata) from rookeries in the Torres Strait

ContextHawksbill sea turtles (Eretmochelys imbricata) are conservation-dependent species in many areas of the world. A key component to ensuring successful conservation initiatives for the species is understanding their distribution and habitat use, in particular, knowing the nesting sites, migration routes and foraging areas for each genetic stock, and how these might overlap with threats. AimsInvestigate the post-nesting movements of hawksbill sea turtles nesting in the Torres Strait, including migration movements and foraging ground size and distribution. MethodsNine nesting hawksbill turtles of the north-eastern Australian genetic stock were satellite-tagged between the 2010 and 2019 nesting seasons for 182 ± 143 days (mean ± s.d.). Key resultsThree turtles continued to nest on adjacent islands before commencing their post-nesting migrations. From the nine tracked turtles, the following three migration movement strategies were identified: (1) direct migration between the nesting beach and foraging ground, (2) non-direct movements with a period of meandering, and (3) establishment of two foraging areas separated by direct movement pathways. Foraging grounds were distributed across the Torres Strait and north-eastern Australia and varied in size between 0.54 km2 and 3.31 km2 (95% UD). None of the turtles migrated outside of Australian waters. ConclusionsThe localisation of these movements and habitats within Australian waters provides a unique conservation opportunity, whereby protection efforts involve multiple life stages and potentially preserve turtles from multiple genetic stocks. The variety of inter-nesting, migration and home range strategies used by the tracked turtles in the present study highlight the broad scope of hawksbill movements. ImplicationsOur findings are useful for the implementation of future marine conservation areas and shed light into the nesting, migratory and foraging behaviours of hawkbills from this genetic stock. An understanding of the movement tracks and habitats used by a genetic pool is essential for well grounded implementation of conservation areas and management regulations.

Flooding-induced mortality of loggerhead sea turtle eggs

Abstract ContextMarine turtle eggs incubate in dynamic beaches, where they are vulnerable to both saltwater and freshwater flooding. Understanding the capacity for marine turtle eggs to tolerate flooding will aid management efforts to predict and mitigate the impacts of climate change, including sea-level rise and increases in coastal flooding. AimsEvaluate the interactive effects of flooding duration and incubation stage on the hatching success of loggerhead turtle (Caretta caretta) eggs. MethodsGroups of 20 eggs from multiple clutches were incubated in plastic containers in a beach hatchery. Eggs at six stages of incubation (0, 1, 2, 4, 6 and 7 weeks post-oviposition) were excavated from the hatchery and exposed to saltwater or freshwater flooding for seven durations of time (0, 1, 2, 3, 6, 24 or 48h). Containers of eggs were either submerged in a bucket of water or left outside of the bucket (control; no flooding) for their designated duration, allowed to drain, then reburied in the hatchery. Following hatchling emergence, the hatching success of each group of eggs was evaluated. Key resultsFreshly laid eggs and eggs on the verge of hatching exposed to any flooding and all eggs exposed to extended periods of flooding (24 and 48h) suffered complete mortality. Eggs at 20–80% development exposed to short periods of flooding (1–6h) maintained high hatching success that was statistically equivalent to control eggs, while eggs at &lt;20% and &gt;80% development exhibited significant decreases in hatching success. ConclusionsMarine turtle eggs in the middle of incubation can tolerate saltwater and freshwater flooding for up to 6h. Outside of this period or when flooding is longer, disruption of gas concentrations and osmotic gradients in the egg chamber can lead to embryonic mortality. These findings have reinforced concerns regarding the capacity for marine turtle populations to continue to function as rising sea levels and increases in coastal flooding alter the hydrology of nesting beaches. ImplicationsAs current and predicted climate change threatens the suitability of the incubation environment used by marine turtles, corrective actions to maximise hatching success need to be taken before the eggs are flooded.

Fidelity to foraging sites after long migrations

Patterns of animal movement associated with foraging lie at the heart of many ecological studies and often animals face decisions of staying in an environment they know versus relocating to new sites. The lack of knowledge of new foraging sites means there is risk associated with a decision to relocate (e.g. poor foraging) as well as a potential benefit (e.g. improved foraging). Using a unique long-term satellite tracking dataset for several sea turtle species, combined with capture-mark-recapture data extending over 50 years, we show how, across species, individuals generally maintain tight fidelity to specific foraging sites after extended (up to almost 10,000 km) migration to and from distant breeding sites as well as across many decades. Migrating individuals often travelled through suitable foraging areas en route to their 'home' site and so extended their journeys to maintain foraging site fidelity. We explore the likely mechanistic underpinnings of this trait, which is also seen in some migrating birds, and suggest that individuals will forgo areas of suitable forage encountered en route during migration when they have poor knowledge of the long-term suitability of those sites, making relocation to those sites risky.

Towards the development of standardised sea turtle primary cell cultures for toxicity testing

Chemical contaminants are known to accumulate in marine megafauna globally, but little is known about how this impacts animal health. In vitro assays offer an ethical, reproducible and cost-effective alternative to live animal toxicity testing on large, long-lived or threatened species, such as sea turtles. However, using a cell culture from a single animal raise the question of whether the toxicity observed adequately represents the toxicity in that species. This study examined variation in the cytotoxic response of primary skin fibroblasts established from seven green (Chelonia mydas) and five loggerhead (Caretta caretta) sea turtles. Cell viability using resazurin dye was examined in response to exposure to five contaminants. The variation in cytotoxicity was generally low (within a factor of five) for both independent analyses of the same cell culture, and cell cultures from different individuals. This low within and between cell culture variation indicates that primary sea turtle cell cultures can provide a suitable approach to understanding toxicity in sea turtles. In addition, green and loggerhead turtle cells showed similar toxicity to the compounds tested, indicating that only subtle differences in chemical sensitivity may exist between sea turtle species. This study provides a framework for using species-specific cell cultures in future toxicological studies on sea turtles. Although in vivo studies are the gold standard for toxicological studies and species-specific risk assessments, the development of in vitro tools can provide important information when in vivo studies are not possible or practical. For large, endangered species such as sea turtles that are exposed to, and accumulate, a large number of contaminants, using validated cell cultures may facilitate the rapid assessment of chemical risk to these animals.

Distinguishing between sea turtle foraging areas using stable isotopes from commensal barnacle shells

Understanding the movement behaviour of marine megafauna within and between habitats is valuable for informing conservation management, particularly for threatened species. Stable isotope analyses of soft-tissues have been used to understand these parameters in sea turtles, usually relying on concurrent satellite telemetry at high cost. Barnacles that grow on sea turtles have been shown to offer a source of isotopic history that reflects the temperature and salinity of the water in which the host animal has been. We used a novel method that combines barnacle growth rates and stable isotope analysis of barnacle shells (δ¹⁸O and δ¹³C) as predictors of home area for foraging sea turtles. We showed high success rates in assigning turtles to foraging areas in Queensland, Australia, based on isotope ratios from the shells of the barnacles that were attached to them (86–94% when areas were separated by >400 km). This method could be used to understand foraging distribution, migration distances and the habitat use of nesting turtles throughout the world, benefiting conservation and management of these threatened species and may be applied to other taxa that carry hitchhiking barnacles through oceans or estuaries.

Elucidating temporal trends in trace element exposure of green turtles (Chelonia mydas) using the toxicokinetic differences of blood and scute samples

Blood is considered a suitable biomonitoring matrix for evaluating relatively recent exposure to environmental contaminants since abrupt changes in exposure regimes are rapidly reflected in blood. On the other hand, keratinized tissues, such as turtle scutes, are known to integrate trace element exposure over relatively long time periods. This study aimed to test the use of the differences in blood and scute to inform on the historical trace element exposure of green turtles. We propose a blood-scute kinetic model to predict how an increase in exposure would affect the concentrations in these two matrices over time. We then tested the relationship between blood and scute concentrations for 19 trace elements in two green turtle populations presumed to experience relatively constant exposure conditions. Significant log-log and linear correlations were observed between blood and scute concentrations for Co, As, Mo, Sb, and Cd. We then analysed blood-scute ratios in turtles from two coastal sites with known elevated exposure to various trace elements from previous studies. Deviations from the steady-state were clearly evident in these coastal turtles (for Co and Cd) and were consistent with the model prediction of changes in exposure. These field data provide evidence that blood-scute ratios can provide a valuable tool for examining the historical trace element exposure of turtles. We further present a method by which the general model may be refined and validated, by using data from individual turtles that had been recaptured across multiple years. Although the timeframe and number of recaptured samples available for this study were limited, the temporal changes in blood-scute ratios in these animals were generally consistent with those suggested by the model. Thus, the ratio between paired blood and scute trace element concentrations could be used to establish a temporal exposure index in turtles.

Microplastic ingestion ubiquitous in marine turtles

Despite concerns regarding the environmental impacts of microplastics, knowledge of the incidence and levels of synthetic particles in large marine vertebrates is lacking. Here, we utilize an optimized enzymatic digestion methodology, previously developed for zooplankton, to explore whether synthetic particles could be isolated from marine turtle ingesta. We report the presence of synthetic particles in every turtle subjected to investigation (n = 102) which included individuals from all seven species of marine turtle, sampled from three ocean basins (Atlantic [ATL]: n = 30, four species; Mediterranean (MED): n = 56, two species; Pacific (PAC): n = 16, five species). Most particles (n = 811) were fibres (ATL: 77.1% MED: 85.3% PAC: 64.8%) with blue and black being the dominant colours. In lesser quantities were fragments (ATL: 22.9%: MED: 14.7% PAC: 20.2%) and microbeads (4.8%; PAC only; to our knowledge the first isolation of microbeads from marine megavertebrates). Fourier transform infrared spectroscopy (FT-IR) of a subsample of particles (n = 169) showed a range of synthetic materials such as elastomers (MED: 61.2%; PAC: 3.4%), thermoplastics (ATL: 36.8%: MED: 20.7% PAC: 27.7%) and synthetic regenerated cellulosic fibres (SRCF; ATL: 63.2%: MED: 5.8% PAC: 68.9%). Synthetic particles being isolated from species occupying different trophic levels suggest the possibility of multiple ingestion pathways. These include exposure from polluted seawater and sediments and/or additional trophic transfer from contaminated prey/forage items. We assess the likelihood that microplastic ingestion presents a significant conservation problem at current levels compared to other anthropogenic threats.

The impact of environmental factors on marine turtle stranding rates

Globally, tropical and subtropical regions have experienced an increased frequency and intensity in extreme weather events, ranging from severe drought to protracted rain depressions and cyclones, these coincided with an increased number of marine turtles subsequently reported stranded. This study investigated the relationship between environmental variables and marine turtle stranding. The environmental variables examined in this study, in descending order of importance, were freshwater discharge, monthly mean maximum and minimum air temperatures, monthly average daily diurnal air temperature difference and rainfall for the latitudinal hotspots (-27°, -25°, -23°, -19°) along the Queensland coast as well as for major embayments within these blocks. This study found that marine turtle strandings can be linked to these environmental variables at different lag times (3-12 months), and that cumulative (months added together for maximum lag) and non-cumulative (single month only) effects cause different responses. Different latitudes also showed different responses of marine turtle strandings, both in response direction and timing.Cumulative effects of freshwater discharge in all latitudes resulted in increased strandings 10-12 months later. For latitudes -27°, -25° and -23° non-cumulative effects for discharge resulted in increased strandings 7-12 months later. Latitude -19° had different results for the non-cumulative bay with strandings reported earlier (3-6 months). Monthly mean maximum and minimum air temperatures, monthly average daily diurnal air temperature difference and rainfall had varying results for each examined latitude. This study will allow first responders and resource managers to be better equipped to deal with increased marine turtle stranding rates following extreme weather events.

Does behaviour affect the dispersal of flatback post-hatchlings in the Great Barrier Reef?

The ability of individuals to actively control their movements, especially during the early life stages, can significantly influence the distribution of their population. Most marine turtle species develop oceanic foraging habitats during different life stages. However, flatback turtles (Natator depressus) are endemic to Australia and are the only marine turtle species with an exclusive neritic development. To explain the lack of oceanic dispersal of this species, we predicted the dispersal of post-hatchlings in the Great Barrier Reef (GBR), Australia, using oceanographic advection-dispersal models. We included directional swimming in our models and calibrated them against the observed distribution of post-hatchling and adult turtles. We simulated the dispersal of green and loggerhead turtles since they also breed in the same region. Our study suggests that the neritic distribution of flatback post-hatchlings is favoured by the inshore distribution of nesting beaches, the local water circulation and directional swimming during their early dispersal. This combination of factors is important because, under the conditions tested, if flatback post-hatchlings were entirely passively transported, they would be advected into oceanic habitats after 40 days. Our results reinforce the importance of oceanography and directional swimming in the early life stages and their influence on the distribution of a marine turtle species.

Anti-predator meshing may provide greater protection for sea turtle nests than predator removal

The problem of how to protect sea turtle nests from terrestrial predators is of worldwide concern. On Queensland's southern Sunshine Coast, depredation of turtle nests by the introduced European red fox (Vulpes vulpes) has been recorded as the primary terrestrial cause of egg and hatchling mortality. We investigated the impact of foxes on the nests of the loggerhead turtle (Caretta caretta) and occasional green turtle (Chelonia mydas) over ten nesting seasons. Meshing of nests with fox exclusion devices (FEDs) was undertaken in all years accompanied by lethal fox control in the first five-year period, but not in the second five-year period. Lethal fox control was undertaken in the study area from 2005 to February 2010, but foxes still breached 27% (range19-52%) of turtle nests. In the second five-year period, despite the absence of lethal fox control, the average percentage of nests breached was less than 3% (range 0-4%). Comparison of clutch depredation rates in the two five-year periods demonstrated that continuous nest meshing may be more effective than lethal fox control in mitigating the impact of foxes on turtle nests. In the absence of unlimited resources available for the eradication of exotic predators, the use of FEDs and the support and resourcing of a dedicated volunteer base can be considered an effective turtle conservation tool on some beaches.

The effect of on-shore light pollution on sea-turtle hatchlings commencing their off-shore swim

Context Off-shore recruitment impairment of sea-turtle hatchlings because of light pollution is a growing concern to conservation of sea-turtle population throughout the world. Studies have focussed on sea-turtle hatchling sea-finding behaviour, and ignored the possible effect that on-shore lighting might have on hatchlings after they have entered the sea. Aims We experimentally evaluated the effect that on-shore light pollution has on the swimming behaviour of green turtle hatchlings once they have entered the sea and begun swimming off-shore. We also estimated the decrease in off-shore recruitment of hatchlings as a result of light pollution disruption of the off-shore swim. Methods Hatchling misorientation rates were quantified by releasing marked hatchlings to the sea from different land-based locations adjacent to light-polluted beach areas under a variety of environmental conditions. The beach in light-polluted regions was then searched for marked hatchlings returning to shore from the sea. Key results Misorientation rates were highest in trials conducted during moonless nights (66.7% of trials had some hatchlings return to shore) and lowest during trials conducted during moonlit nights (no trials had hatchlings return to shore). Green turtle hatchling off-shore recruitment for the entire 2014–15 nesting season at Heron Island was estimated to decrease 1.0 –2.4% as a result of on-shore lights disrupting hatchling off-shore swimming behaviour. Conclusions On moonless nights, sea-turtle hatchlings after having successfully completed their journey from nest to sea and entered the sea can be lured back to shore again by shore-based light pollution and, this will decrease their off-shore recruitment success. Implications To ensure maximum off-shore recruitment of sea-turtle hatchlings, on-shore light pollution adjacent to nesting beaches needs to be minimised so as to minimise misorientation and disorientation of hatchlings while on the beach and in near-shore waters.

Trace element reference intervals in the blood of healthy green sea turtles to evaluate exposure of coastal populations

Exposure to essential and non-essential elements may be elevated for green sea turtles (Chelonia mydas) that forage close to shore. Biomonitoring of trace elements in turtle blood can identify temporal trends over repeated sampling events, but any interpretation of potential health risks due to an elevated exposure first requires a comparison against a baseline. This study aims to use clinical reference interval (RI) methods to produce exposure baseline limits for essential and non-essential elements (Na, Mg, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba, and Pb) using blood from healthy subadult turtles foraging in a remote and offshore part of the Great Barrier Reef. Subsequent blood biomonitoring of three additional coastal populations, which forage in areas dominated by agricultural, urban and military activities, showed clear habitat-specific differences in blood metal profiles relative to the those observed in the offshore population. Coastal turtles were most often found to have elevated concentrations of Co, Mo, Mn, Mg, Na, As, Sb, and Pb relative to the corresponding RIs. In particular, blood from turtles from the agricultural site had Co concentrations ranging from 160 to 840 μg/L (4-25 times above RI), which are within the order expected to elicit acute effects in many vertebrates. Additional clinical blood biochemistry and haematology results indicate signs of a systemic disease and the prevalence of an active inflammatory response in a high proportion (44%) of turtles from the agricultural site. Elevated Co, Sb, and Mn in the blood of these turtles significantly correlated with elevated markers of acute inflammation (total white cell counts) and liver dysfunction (alkaline phosphatase and total bilirubin). The results of this study support the notion that elevated trace element exposures may be adversely affecting the health of nearshore green sea turtles.

An assessment of ‘turtle-friendly' lights on the sea-finding behaviour of loggerhead turtle hatchlings (Caretta caretta)

Context It is well established that artificial light can disrupt the sea-finding ability of sea turtle hatchlings, and some manufactures are now marketing ‘turtle-friendly’ lights that are supposed to be minimally disruptive to this sea-finding behaviour. However, there have been no studies that have tested whether ‘turtle-friendly’ lights are benign to hatchling sea turtle sea-finding ability. Aims We tested two different types of ‘turtle-friendly’ lights (LED amber-light peak intensity 620 nm and LED red-light peak intensity 640 nm) to see whether they are disruptive to the sea-finding ability of eastern-coast Australian loggerhead turtle hatchlings. Methods Using standard circular-arena experiments, we assessed the directional preference of newly emerged loggerhead turtle hatchlings from the Woongarra Coast of Queensland, Australia, during different moon phases without artificial lighting and in the presence of ‘turtle-friendly’ lights. Key results Contrary to expectations, sea-finding ability of hatchlings was disrupted by the amber lights, particularly in the absence of a moon. The less intense red lights were less disruptive to hatchlings; however, misorientation and disorientation events still occurred when lights were within 4 m of hatchlings. The disruptive impact on sea-finding ability increased with the cumulative impact of multiple lights increasing light intensity. Conclusions The ‘turtle-friendly’ lights we used disrupted the sea-finding ability of eastern-coast Australian loggerhead turtle hatchlings, with the most pronounced disruption occurring under moonless conditions. Implications The use of amber and red LED lights adjacent to the nesting beaches of loggerhead sea turtles should be managed because this lighting has the potential to disrupt the sea-finding ability of sea turtle hatchlings.

Phylogeography, Genetic Diversity, and Management Units of Hawksbill Turtles in the Indo-Pacific

Hawksbill turtle (Eretmochelys imbricata) populations have experienced global decline because of a history of intense commercial exploitation for shell and stuffed taxidermied whole animals, and harvest for eggs and meat. Improved understanding of genetic diversity and phylogeography is needed to aid conservation. In this study, we analyzed the most geographically comprehensive sample of hawksbill turtles from the Indo-Pacific Ocean, sequencing 766 bp of the mitochondrial control region from 13 locations (plus Aldabra, n = 4) spanning over 13500 km. Our analysis of 492 samples revealed 52 haplotypes distributed in 5 divergent clades. Diversification times differed between the Indo-Pacific and Atlantic lineages and appear to be related to the sea-level changes that occurred during the Last Glacial Maximum. We found signals of demographic expansion only for turtles from the Persian Gulf region, which can be tied to a more recent colonization event. Our analyses revealed evidence of transoceanic migration, including connections between feeding grounds from the Atlantic Ocean and Indo-Pacific rookeries. Hawksbill turtles appear to have a complex pattern of phylogeography, showing a weak isolation by distance and evidence of multiple colonization events. Our novel dataset will allow mixed-stock analyses of hawksbill turtle feeding grounds in the Indo-Pacific by providing baseline data needed for conservation efforts in the region. Eight management units are proposed in our study for the Indo-Pacific region that can be incorporated in conservation plans of this critically endangered species.

Coupling passive sampling with in vitro bioassays and chemical analysis to understand combined effects of bioaccumulative chemicals in blood of marine turtles

Conventional target analysis of biological samples such as blood limits our ability to understand mixture effects of chemicals. This study aimed to establish a rapid passive sampling technique using the polymer polydimethylsiloxane (PDMS) for exhaustive extraction of mixtures of neutral organic chemicals accumulated in blood of green turtles, in preparation for screening in in vitro bioassays. We designed a PDMS-blood partitioning system based on the partition coefficients of chemicals between PDMS and major blood components. The sampling kinetics of hydrophobic test chemicals (polychlorinated dibenzo-p-dioxins; PCDDs) from blood into PDMS were reasonably fast reaching steady state in <96 h. The geometric mean of the measured PDMS-blood partition coefficients for PCDDs, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) was 14 L blood kg PDMS(-1) and showed little variability (95% confidence interval from 8.4 to 29) across a wide range of hydrophobicity (logKow 5.7-8.3). The mass transfer of these chemicals from 5 mL blood into 0.94 g PDMS was 62-84%, which is similar to analytical recoveries in conventional solvent extraction methods. The validated method was applied to 15 blood samples from green turtles with known concentrations of PCDD/Fs, dioxin-like PCBs, PBDEs and organochlorine pesticides. The quantified chemicals explained most of the dioxin-like activity (69-98%), but less than 0.4% of the oxidative stress response. The results demonstrate the applicability of PDMS-based passive sampling to extract bioaccumulative chemicals from blood as well as the value of in vitro bioassays for capturing the combined effects of unknown and known chemicals.

Clinical and Pathological Findings in Green Turtles (Chelonia mydas) from Gladstone, Queensland: Investigations of a Stranding Epidemic

An investigation into the health of green turtles was undertaken near Gladstone, Queensland, in response to a dramatic increase in stranding numbers in the first half of 2011. A total of 56 live turtles were subject to clinical examination and blood sampling for routine blood profiles, and 12 deceased turtles underwent a thorough necropsy examination. This population of green turtles was found to be in poor body condition and a range of infectious and non-infectious conditions were identified in the unhealthy turtles, including hepato-renal insufficiency (up to 81%, 27/33 based on clinical pathology), cachexia (92%, 11/12), parasitism (75%, 9/12), cardiopulmonary anomalies (42%, 5/12), gastroenteritis (25%, 3/12), masses (25%, 3/12) and mechanical impediments (17%, 2/12 based on necropsy). Overall, there was no evidence to indicate a unifying disease as a primary cause of the mass mortality. Recent adverse weather events, historic regional contamination and nearby industrial activities are discussed as potential causative factors.

Incubation temperature, morphology and performance in loggerhead (Caretta caretta) turtle hatchlings from Mon Repos, Queensland, Australia

Marine turtles are vulnerable to climate change because their life history and reproduction are tied to environmental temperatures. The egg incubation stage is arguably the most vulnerable stage, because marine turtle eggs require a narrow range of temperatures for successful incubation. Additionally, incubation temperature affects sex, emergence success, morphology and locomotor performance of hatchlings. Hatchlings often experience high rates of predation in the first few hours of their life, and increased size or locomotor ability may improve their chances of survival. Between 2010 and 2013 we monitored the temperature of loggerhead (Caretta caretta; Linnaeus 1758) turtle nests at Mon Repos Rookery, and used these data to calculate a mean three day maximum temperature (T3dm) for each nest. We calculated the hatching and emergence success for each nest, then measured the mass, size and locomotor performance of hatchlings that emerged from those nests. Nests with a T3dm greater than 34°C experienced a lower emergence success and produced smaller hatchlings than nests with a T3dm lower than 34°C. Hatchlings from nests with a T3dm below 34°C performed better in crawling and swimming trials than hatchlings from nests with a T3dm above 34°C. Thus even non-lethal increases in global temperatures have the potential to detrimentally affect fitness and survival of marine turtle hatchlings.

A risk assessment approach to manage inundation of Elseya albagula nests in impounded waters: a win-win situation?

A risk assessment process was used to trial the impact of potential new operating rules on the frequency of nest inundation for the White-throated snapping turtle, Elseya albagula, in the impounded waters of the Burnett River, Queensland, Australia. The proposed operating rules would increase the barrage storage level during the turtle nesting season (May-July) and then would be allowed to reduce to a lower level for incubation for the rest of the year. These proposed operating rules reduce rates of nest inundation by altering water levels in the Ben Anderson Barrage impoundment of the Burnett River. The rules operate throughout the turtle reproductive period and concomitantly improve stability of littoral habitat and fishway operation. Additionally, the proposed rules are expected to have positive socio-economic benefits within the region. While regulated water resources will inherently have a number of negative environmental implications, these potential new operating rules have the capacity to benefit the environment while managing resources in a more sustainable manner. The operating rules have now been enacted in subordinate legislation and require the operator to maintain water levels to minimize turtle nest inundation.

Mixed stock analysis of a resident green turtle, Chelonia mydas, population in New Caledonia links rookeries in the South Pacific

Context Migratory species are known to pose a challenge for conservation because it is essential to understand their complex life history in order to implement efficient conservation actions. Aims In New Caledonia, large seagrass habitats in the Grand Lagon Sud (GLS) are home to resident green turtles (Chelonia mydas) of unknown origins. To assess the stock composition in the GLS, 164 foraging turtles were sampled for genetic analysis of ~770 base pairs of the mitochondrial DNA (mtDNA) control region. Methods Foraging turtles ranging in size from 48.0 to 108.4 cm curved carapace length were captured at five different sites within the GLS between September 2012 and December 2013. To provide baseline data for mixed stock analysis, published data from rookeries were used in addition to 105 samples collected at rookeries in the d’Entrecasteaux Islands and Chesterfield Islands in New Caledonia and at Malekula Island in Vanuatu. Exact tests of population differentiation and pairwise FST estimates were used to test for differences in mtDNA haplotype frequencies. Key results These analyses indicated that rookeries in the d’Entrecasteaux Islands and Vanuatu form unique management units and that the Chesterfield Islands rookeries are linked to the Coral Sea management unit. Mixed stock analysis indicated the highest proportion (mean = 0.63) of foraging turtles originate from the d’Entrecasteaux stock. Conclusions The larger contribution is estimated to be from a large rookery from New Caledonia, but smaller contributions are suggested from other rookeries in the South Pacific. Implications Marine conservation policies in New Caledonia need to consider the links between the foraging and nesting populations of C. mydas in New Caledonia and other rookeries and foraging grounds in the Coral Sea.

A decision framework for prioritizing multiple management actions for threatened marine megafauna

Resources for conserving biodiversity are invariably insufficient. This situation creates the need for transparent, systematic frameworks to help stakeholders prioritize the allocation of resources across multiple management actions. We developed a novel framework that explicitly prioritizes actions to minimize the impacts of several threats across a species' range. The framework uses a budget constraint and maximizes conservation outcomes from a set of management actions, accounting for the likelihood of the action being successfully applied and accepted by local and Indigenous communities. This approach is novel in that it integrates local knowledge and expert opinion with optimization software, thereby minimizing assumptions about likelihood of success of actions and their effectiveness. To test the framework, we used the eastern Gulf of Carpentaria and Torres Strait population of the flatback turtle, Natator depressus, as a case study. This approach allowed the framework to be applied in a data-poor context, a situation common in conservation planning. The framework identified the best set of actions to maximize the conservation of flatback eggs for scenarios with different budgets and management parameters and allowed comparisons between optimized and preselected scenarios. Optimized scenarios considered all implementable actions to explore how to best allocate resources with a specified budget and focus. Preselected scenarios were used to evaluate current allocations of funds and/or potential budget allocations suggested by different stakeholders. Scenarios that used a combination of aerial and ground strategies to reduce predation of eggs performed better than scenarios that focused only on reducing harvest of eggs. The performances of optimized and preselected scenarios were generally similar among scenarios that targeted similar threats. However, the cost-effectiveness of optimized scenarios was usually higher than that of preselected scenarios, demonstrating the value of conducting a systematic optimization approach. Our method provides a foundation for more effective conservation investments and guidance to prioritize actions within recovery plans while considering the sociopolitical and cultural context of decisions. The framework can be adapted easily to a wide range of species, geographical scales, and life stages.

Investigating diet and diet switching in green turtles (Chelonia mydas)

Understanding the dietary ecology of animals provides information about their habitat requirements, facilitating informed conservation. We used last-bite diet and stable isotope analysis to assess the diet of juvenile and adult green turtles (Chelonia mydas) at two different habitats located 10 km apart within Port Curtis, Queensland, Australia. Last-bite diet analysis indicated that turtles had distinctly different diets in these two habitats: in one the diet was dominated by red macroalgae and in the other the diet was dominated by seagrass. Only juveniles (n = 12) were caught in the habitat where red macroalgae dominated the diet, while both juveniles (n = 9) and adults (n = 38) were captured in the habitat where seagrass dominated the diet. In the seagrass habitat there was no difference in diet between juveniles and adults, and no difference in diet between adult males (n = 17) and females (n = 21). Because the red macroalgae and seagrass had distinctly different carbon stable isotope ratios, it was possible to detect a change in diet by comparing the carbon stable isotope ratio between serum and epidermal tissue sampled from the same turtle. In this region, a switch in diet would reflect a shift in foraging habitat. Such comparisons indicate that ~50% of turtles switched diet, and therefore changed foraging habitat between the time when blood serum and epidermis were formed. This implies that switching foraging habitat by green turtles within this region is a common occurrence, which is somewhat surprising because previously it was thought that foraging green turtles had high site fidelity with relatively small home ranges.

Establishment of reference intervals for plasma protein electrophoresis in Indo-Pacific green sea turtles, Chelonia mydas

Biochemical and haematological parameters are increasingly used to diagnose disease in green sea turtles. Specific clinical pathology tools, such as plasma protein electrophoresis analysis, are now being used more frequently to improve our ability to diagnose disease in the live animal. Plasma protein reference intervals were calculated from 55 clinically healthy green sea turtles using pulsed field electrophoresis to determine pre-albumin, albumin, α-, β- and γ-globulin concentrations. The estimated reference intervals were then compared with data profiles from clinically unhealthy turtles admitted to a local wildlife hospital to assess the validity of the derived intervals and identify the clinically useful plasma protein fractions. Eighty-six per cent {19 of 22 [95% confidence interval (CI) 65-97]} of clinically unhealthy turtles had values outside the derived reference intervals, including the following: total protein [six of 22 turtles or 27% (95% CI 11-50%)], pre-albumin [two of five, 40% (95% CI 5-85%)], albumin [13 of 22, 59% (95% CI 36-79%)], total albumin [13 of 22, 59% (95% CI 36-79%)], α- [10 of 22, 45% (95% CI 24-68%)], β- [two of 10, 20% (95% CI 3-56%)], γ- [one of 10, 10% (95% CI 0.3-45%)] and β-γ-globulin [one of 12, 8% (95% CI 0.2-38%)] and total globulin [five of 22, 23% (8-45%)]. Plasma protein electrophoresis shows promise as an accurate adjunct tool to identify a disease state in marine turtles. This study presents the first reference interval for plasma protein electrophoresis in the Indo-Pacific green sea turtle.

Migrations of green turtles (Chelonia mydas) between nesting and foraging grounds across the Coral Sea

Marine megafauna tend to migrate vast distances, often crossing national borders and pose a significant challenge to managers. This challenge is particularly acute in the Pacific, which contains numerous small island nations and thousands of kilometers of continental margins. The green sea turtle, Chelonia mydas, is one such megafauna that is endangered in Pacific waters due to the overexploitation of eggs and adults for human consumption. Data from long-term tagging programs in Queensland (Australia) and New Caledonia were analysed to investigate the migrations by C. mydas across the Coral Sea between their nesting site and their feeding grounds. A review of data collected over the last 50 years by different projects identified multiple migrations of C. mydas to and from New Caledonia (n = 97) and indicate that turtles foraging in New Caledonia nest in the Great Barrier Reef (Australia) and vice versa. Several explanations exist for turtles exhibiting this energetically costly movement pattern from breeding to distant foraging grounds (1200–2680 km away) despite viable foraging habitat being available in the local vicinity. These include hatchling drift, oceanic movements and food abundance predictability. Most of the tag recoveries in New Caledonia belonged to females from the south Great Barrier Reef genetic stock. Some females (n = 2) even showed fidelity to foraging sites located 1200 km away from the nesting site located in New Caledonia. This study also reveals previously unknown migrations pathways of turtles within the Coral Sea.

Plasma biochemical and PCV ranges for healthy, wild, immature hawksbill (Eretmochelys imbricata) sea turtles

In recent years, the use of blood chemistry as a diagnostic tool for sea turtles has been demonstrated, but much of its effectiveness relies on reference intervals. The first comprehensive blood chemistry values for healthy wild hawksbill (Eretmochelys imbricata) sea turtles are presented. Nineteen blood chemistry analytes and packed cell volume were analysed for 40 clinically healthy juvenile hawksbill sea turtles captured from a rocky reef habitat in northern Australia. We used four statistical approaches to calculate reference intervals and to investigate their use with non-normal distributions and small sample sizes, and to compare upper and lower limits between methods. Eleven analytes were correlated with curved carapace length indicating that body size should be considered when designing future studies and interpreting analyte values.

Reproduction and population ecology of the vulnerable western sawshelled turtle, Myuchelys bellii, in the Murray–Darling Basin, Australia

Effective management decisions about the conservation of threatened species often rely on good information about their biology and life-history traits. Nearly half of all turtle species face extinction in the wild through worldwide rapid declines in species abundance and habitat loss. The vulnerable western sawshelled turtle, Myuchelys bellii, from eastern Australia is one such species under threat and for which fundamental information is lacking. The three known populations of M. bellii in the Murray–Darling Basin from the Namoi, Gwydir and Border Rivers catchments were studied over a period of nearly eight years. From capture–mark–recapture data, we studied M. bellii’s sexual maturity and reproduction, compared age of individuals using growth rates derived from annuli and growth increment data and calculated a population estimate for the Queensland population. For the first time this study has quantified the life-history traits of M. bellii including having delayed age at first breeding, with males taking nearly 10 years to mature and females approaching 20 years (from growth increment data), low reproductive effort (14.3 eggs per adult female; 78% of females breeding in any one year) and high survivorship with a predicted lifespan of over 40 years. Of particular management concern for M. bellii is the long-term conservation of the small isolated Queensland population (<400 individuals). The extensive dataset provides a baseline for future investigations and management actions required to improve the conservation outcomes for this threatened turtle.

Evidence of sirenian cold stress syndrome in dugongs Dugong dugon from southeast Queensland, Australia

Cold stress syndrome (CSS) is the term used to describe the range of clinical signs and chronic disease processes that can occur in Florida, USA, manatees Trichechus manatus latirostris exposed to water temperatures below 20°C for extended periods. Although no cold-related adverse events have been described in the closely related dugong Dugong dugon thus far, it has been established that they make movements in response to water temperatures lower than about 17 to 18°C. In this study, archive reports for dugong carcasses submitted to The University of Queensland School of Veterinary Science for post mortem examination during 2010 to 2012 were examined. These animals had been recovered from Moreton Bay, southeast Queensland, Australia, and 10 out of 14 fulfilled the criteria for 'potential cold stress cases.' Epidermal hyperplasia and secondary bacterial infection, serous atrophy of pericardial adipose tissue, and multisystem abscessation were features commonly noted in these cases. Water temperature data were correlated with the time of year that carcasses were submitted for examination. Higher numbers of carcasses diagnosed with potential CSS were noted during sustained periods in which water temperature was below 20°C. Given the pattern of increased submission of non-specifically, chronically unwell animals in the colder months and evidence that environmental conditions known to precipitate CSS occur in southeast Queensland, it is probable that, like manatees, dugongs in this area are affected by CSS. Further investigation to confirm and to better characterize the syndrome is recommended to refine management practices and improve treatment of affected animals.

Artificial lighting and disrupted sea-finding behaviour in hatchling loggerhead turtles (Caretta caretta) on the Woongarra coast, south-east Queensland, Australia

Coastal development adjacent to sea turtle nesting beaches can result in an increase in exposure to artificial lighting at night. That lighting can repel nesting females and interfere with the orientation of hatchlings from the nest to the sea. Disrupted hatchling orientation is a serious source of turtle mortality, sufficient to reduce recruitment and contribute to a long-term marine turtle population decline. The purpose of this study was to assess whether artificial lighting disrupts hatchling sea-finding behaviour at the largest loggerhead rookery in the South Pacific, the Woongarra coast, south-east Queensland. The crawling tracks of hatchlings that emerged from nests, as well as staged emergences, were used to assess the effect of lighting conditions at several local beaches on hatchling sea-finding behaviour. Disrupted orientation was observed at only a few locations, excluding the majority of the main nesting beach at Mon Repos Conservation Park. At the sites where orientation was disrupted, normal orientation was restored when a full moon was visible, presumably because lunar illumination reduced the perceived brightness of the artificial lights. The controlled use of lights used for guided turtle-viewing tour groups within Mon Repos conservation Park did not interfere with the sea-finding behaviour of hatchling turtles. Further coastal development, especially at the nearby town of Bargara, requires that a light management plan be formulated to ensure that development does not adversely affect the marine turtles that utilise the local nesting beaches.

Blood concentrations of lactate, glucose and corticosterone in dispersing hatchling sea turtles

Natal dispersal of sea turtles is an energetically demanding activity that is fuelled primarily by aerobic metabolism. However, during intense exercise reptiles can use anaerobic metabolism to supplement their energy requirements. We assessed anaerobic metabolism in dispersing hatchling loggerhead and flatback turtles by measuring the concentrations of blood lactate during crawling and at different times during the first four hours of their frenzy swim. We also measured concentrations of blood glucose and corticosterone. Blood lactate (12.13 to 2.03 mmol/L), glucose (6.25 to 3.8 mmol/L) and corticosterone (8.13 to 2.01 ng/mL) concentrations decreased significantly over time in both loggerhead and flatback hatchlings and no significant differences were found between the species. These results indicate that anaerobic metabolism makes a significant contribution to the dispersal phase of hatchling sea turtles during the beach crawl and the first few hours of the frenzy swim.

High incidence of multiple paternity in an Australian snapping turtle (Elseya albagula)

Genetic parentage studies can provide detailed insights into the mating system dynamics of wild populations, including the prevalence and patterns of multiple paternity. Multiple paternity is assumed to be common among turtles, though its prevalence varies widely between species and populations. Several important groups remain to be investigated, including the family Chelidae, which dominate the freshwater turtle fauna of the Southern Hemisphere. We used seven polymorphic microsatellite markers to investigate the presence of multiple fathers within clutches from the white-throated snapping turtle (Elseya albagula), an Australian species of conservation concern. We uncovered a high incidence of multiple paternity, with 83% of clutches showing evidence of multiple fathers and up to three males contributing to single clutches. We confirm a largely promiscuous mating system for this species in the Burnett River, Queensland, although a lone incidence of single paternity indicates it is not the only strategy employed. These data provide the first example of multiple paternity in the Chelidae and extend our knowledge of the taxonomic breadth of multiple paternity in turtles of the Southern Hemisphere.

Effect of nest temperature on hatchling phenotype of loggerhead turtles (Caretta caretta) from two South Pacific rookeries, Mon Repos and La Roche Percée

La Roche Percée, in New Caledonia, is the most important loggerhead turtle rookery outside of Australia for the eastern Pacific genetic stock. The females nesting on this beach are genetically similar to the females found at the Mon Repos rookery in Queensland, Australia. This study shows how nest temperature affects the phenotype of genetically similar populations. During the 2010–11 breeding season, mean nest temperatures were significantly higher at La Roche Percée (31.8°C) than at Mon Repos (29.5°C) and the mean for the three-days-in-a-row maximum nest temperatures was also significantly higher at La Roche Percée (34.6°C), than at Mon Repos (31.7°C). Differences were found in mean hatching success (La Roche Percée 83 ± 3%, Mon Repos 96 ± 2%) and emergence success (La Roche Percée 76 ± 3%, Mon Repos 93 ± 3%). Hatchlings from La Roche Percée also had significantly lower fitness characteristics, having smaller carapace size (La Roche Percée 1565 ± 7 mm2, Mon Repos 1634 ± 5 mm2), slower self-righting times (La Roche Percée 4.7 ± 0.1 s, Mon Repos 2.7 ± 0.1 s) and slower crawling speed in terms of both absolute speed and body lengths per second (La Roche Percée 2.5 ± 0.2 cm s–1 or 0.57 ± 0.05 body lengths s–1, Mon Repos 4.6 ± 0.1 cm s–1 or 1.04 ± 0.02 body lengths s–1). Nest temperatures at La Roche Percée approached the upper limit of embryo thermal tolerance towards the end of incubation (34°C) and this condition may contribute to the lower hatching and emergence success and lower fitness characteristics of hatchlings at the La Roche Percée rookery.

Locomotor activity during the frenzy swim: analysing early swimming behaviour in hatchling sea turtles

Swimming effort of hatchling sea turtles varies across species. In this study we analysed how swim thrust is produced in terms of power stroke rate, mean maximum thrust per power stroke and percentage of time spent power stroking throughout the first 18 h of swimming after entering the water, in both loggerhead and flatback turtle hatchlings and compared this with previous data from green turtle hatchlings. Loggerhead and green turtle hatchlings had similar power stroke rates and percentage of time spent power stroking throughout the trial, although mean maximum thrust was always significantly higher in green hatchlings, making them the most vigorous swimmers in our three-species comparison. Flatback hatchlings, however, were different from the other two species, with overall lower values in all three swimming variables. Their swimming effort dropped significantly during the first 2 h and kept decreasing significantly until the end of the trial at 18 h. These results support the hypothesis that ecological factors mould the swimming behaviour of hatchling sea turtles, with predator pressure being important in determining the strategy used to swim offshore. Loggerhead and green turtle hatchlings seem to adopt an intensely vigorous and energetically costly frenzy swim that would quickly take them offshore into the open ocean in order to reduce their exposure to near-shore aquatic predators. Flatback hatchlings, however, are restricted in geographic distribution and remain within the continental shelf region where predator pressure is probably relatively constant. For this reason, flatback hatchlings might use only part of their energy reserves during a less vigorous frenzy phase, with lower overall energy expenditure during the first day compared with loggerhead and green turtle hatchlings.