Hatchling Production Research Articles

Using systems thinking to inform management of imperiled species: A case study with sea turtles

Management of imperiled species facing spatiotemporally dynamic threats is difficult. Systems thinking can inform their management by quantifying the impacts that they face. We apply systems thinking to the Northern Gulf of Mexico (NGM) loggerhead (Caretta caretta) Recovery Unit (RU), one of the smallest subpopulations of loggerheads nesting in the USA. We characterized disturbances to nests, management actions, and hatchling production across 12 nesting beaches used by this RU to explore how hatchling production would increase if disturbances were mitigated. Annual hatchling production at sites ranged from 470 to 18,191 hatchlings/year. Washovers (19.3% nests/year), washouts (17.9% nests/year), and predation (13% nests/year) were the most common annual disturbances across sites. Focusing on the most impactful disturbances at just five sites could increase annual NGM RU hatchling production by 2.2–6.7%. Efforts to mitigate washovers and washouts are ongoing in Alabama, but these may be futile against tropical cyclones, which accounted for >80% of washouts in the present study, and further require careful examination of associated adverse side-effects. Efforts to mitigate predation are common throughout this RU, but require improved knowledge of predator ecology to reach full potential. Systems thinking allowed us to create a simple model for assessing disturbances and management strategies in terms of hatchling sea turtles. This model can be augmented to run dynamic simulations of how disturbances and management actions impact hatchling production, and can be applied to other species with similar reproductive strategies.

Low‐cost tools mitigate climate change during reproduction in an endangered marine ectotherm

Abstract The impacts of anthropogenic climate change will be most dramatic for species that live in narrow thermal niches, such as reptiles. Given the imminent threat to biodiversity, and that actions to reduce carbon emissions are not yet sufficient, it is important that a sound evidence base of potential mitigation options is available for conservation managers. Successful incubation and production of male sea turtle hatchlings is threatened by increased global temperatures (sex is determined by the temperature at which eggs incubate). Here we test two conservation tools to reduce incubation temperatures: clutch splitting and clutch shading, on a nesting loggerhead turtle Caretta caretta population in the Eastern Atlantic Ocean. During the thermosensitive period of incubation, split and shaded clutches were both 1.00°C cooler than control nests. Clutch splitting (mean: 45 eggs) reduced nest temperatures by reducing metabolic heating during incubation compared to controls (mean: 92 eggs). Modelled primary sex ratios differed between nest treatments, with 1.50% (±6% SE) females produced in shaded nests, 45.00% (±7% SE) females in split nests and 69.00% (±6% SE) females in controls. Neither treatment affected hatchling size, success, mass or vigour. When clutch splitting was repeated 2 years later, hatch success was higher in split clutches compared to controls. Synthesis and applications. Clutch splitting and clutch shading successfully altered the thermal profile of incubating turtle nests. When there is sufficient knowledge to better understand the effects of intervention on fundamental population demographics, they will be useful for reducing incubation temperatures in sea turtle nests, potentially increasing nest survival and male hatchling production. The effect of clutch splitting in reducing nest temperature was lower relative to clutch shading, but requires significantly less funding, materials and specialist skill, key factors for management of turtle rookeries that are often in remote, resource‐limited areas.

Bias in sea turtle productivity estimates: error and factors involved

The conservation and management of endangered species, including sea turtles, require consistent long-term monitoring of productivity (e.g., number of hatchlings emerged per nest, per female, per nesting site, per population). In sea turtle species, some of the relevant data are obtained by estimating the number of hatched eggs from fragments found in the nest after hatching. Yet, no formal assessment of the associated error has been published. Here we provide an estimation of the error associated with the most widespread method used to determine sea turtle productivity (count of shell fragments > 50% of the egg size) using a large dataset (n = 8539) of actual and estimated clutch sizes of four sea turtle species (Caretta caretta, Chelonia mydas, Dermochelys coriacea, Eretmochelys imbricata). The data are analyzed through linear mixed models with several explanatory variables. Results show that the error can be large in certain cases and, when the associated error rate is not adequately considered, may represent a serious problem in studies on reproductive parameters such as clutch size. Some significant explanatory variables suggest that some sources of error are linked to species-specific biological traits (e.g., clutch size, egg size, nest depth), and others imply human error. Other biotic and abiotic factors may also be involved. We recommend that—whenever possible—errors be assessed and adequately reported by studies that estimate clutch size, hatching and emergence success, or hatchling production.

Artificial and natural shade: Implications for green turtle (Chelonia mydas) rookery management

Global sea turtle populations are threatened by rising atmospheric temperatures which result in higher incubation temperatures. Increased incubation temperatures affect embryo survival, hatchling sex ratio and hatchling locomotor performance. This study aimed to determine the effectiveness of natural and artificial shade on reducing green turtle (Chelonia mydas) incubation temperature at Chagar Hutang beach, Redang Island, Malaysia. To achieve this objective, clutches were incubated using three treatments: unshaded control, artificial shade, and natural tree shade. Estimated hatchling sex ratios, hatching success and locomotor performance were compared across the shade treatments. Clutches incubated in the shaded hatchery were on average 1.3 °C cooler than the unshaded control group, but remained above 30.5 °C and were predicted to produce 100% female hatchlings. In contrast, natural shade from the fringing forest reduced incubation temperatures by 2.7 °C relative to the unshaded clutches, and were predicted to produce up to 85% male hatchlings. Hatching success was similar across treatments and little effect of treatment was observed on hatchling locomotor performance. We recommend relocating nests at high risk of inundation or predation to natural tree shade as a viable solution for ensuring at least some male hatchling production at Chagar Hutang beach.

Feminization of hawksbill turtle hatchlings in the twenty-first century at an important regional nesting aggregation

Projected climate change is forecasted to have significant effects on biological systems worldwide. Marine turtles in particular may be vulnerable, as the sex of their offspring is determined by their incubating temperature, termed temperature-dependent sex determination. This study aimed to estimate historical, and forecast future, primary sex ratios of hawksbill turtleEretmochelys imbricatahatchlings at an important nesting ground in northeastern Qatar. Incubation temperatures from the Arabian/Persian Gulf were measured over 2 nesting seasons. Climate data from same period were regressed with nest temperatures to estimate incubation temperatures and hatchling sex ratios for the site from 1993 to 2100. Future hatchling sex ratios were estimated for 2 climate forecasts, one mid-range (SSP245) and one extreme (SSP585). Historical climate data showed female-biased sex ratios of 73.2 ± 12.1% from 1993 to 2017. Female biases from 2018 to 2100 averaged 85.7% ± 6.7% under the mid-range scenario and 87.9% ± 5.4% under the high-range scenario. In addition, predicted female hatchling production was >90% from 2054 and 2052 for SSP245 and SSP585, respectively. These results show that hawksbill primary sex ratios in Qatar are at risk of significant feminization by the year 2100 and that hawksbill turtle incubation temperatures in an extreme, understudied environment are already comparable to those predicted in tropical rookeries during the latter half of the 21stcentury. These results can help conservationists predict primary sex ratios for hawksbill turtles in the region in the face of 21st-century climate change.

Insights into the Nesting Ecology and Annual Hatchling Production of the Komodo Dragon

We studied annual trends and characteristics of nesting activities and hatchling production by female Komodo Dragons (Varanus komodoensis) in Komodo National Park, Indonesia between 2002 and 2006. During this period, we recorded 12, 16, 15, 13, and 6 females nesting annually at 42 potential nesting sites. An average female nesting periodicity was estimated at 1.2±0.4 years. This result arose because most females bred annually and some biennially. Some females reused nest sites in successive years while others did not. Nesting females had significantly lower body mass compared to when they were recaptured again in a non-nesting state. All-female nesting activities were conducted within their resident valleys and suggested a strong tendency for spatial fidelity. Komodo Dragons were generally considered solitary nesters as only on one occasion were two nesting females observed to use the same nesting site. On average, 21.0±3.6 Komodo Dragon hatchlings emerged from each nest. We estimated that within the study area, nesting female Komodo Dragons produced between 129.0±21.8 and 344.0±58.16 hatchlings per annum. We discuss the ecological and evolutionary significance of these attributes. However, the main conservation management implications drawn from this study are that there are a low annual number of nesting females and associated hatchling production in Komodo National Park. Hence, a continuation of more extensive nesting surveys could provide a cost-effective and accurate way to gather important long-term demographic information for this species.

Impact of heavy rainfall events and shading on the temperature of sea turtle nests

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.

Body size constrains maternal investment in a small sea turtle species

To maximise reproductive fitness, species make trade-offs among reproductive traits, e.g., offspring quantity vs. offspring size, within energetic, anatomical, and physiological constraints. Sea turtles are a model taxon to study reproductive trade-offs, because they lack parental care and because there are strong selective pressures on hatchlings due to high predation rates. Natural selection therefore typically favours optimising offspring size over offspring quantity. Nevertheless, the balance between these traits varies between both sea turtle populations and species. Here, we quantified individual variation in reproductive traits of olive ridley turtles (Lepidochelys olivacea) in northwest Costa Rica. Olive ridley females displayed considerable inter-female variation in reproductive traits with larger females producing larger clutches. These larger females also produced longer and heavier hatchlings than smaller females despite producing similar sized eggs. Females did not exhibit a trade-off between clutch size and egg mass, although variation in clutch size (coefficient of variation = 16.8%) was greater than that of egg mass (10.1%). Producing more eggs per clutch had 1.8 times the effect of producing heavier eggs at increasing clutch mass. The effect of clutch frequency was 2.5 times that of clutch size on seasonal egg production and 2.4 times that of clutch size on seasonal hatchling production. In conclusion, olive ridley turtles exhibit considerable variation in reproductive traits, but their small body size constrains clutch size and has implications for their overall reproductive output.

Effects of temperature on life histories of three endangered Japanese diving beetle species

AbstractTo elucidate population‐increasing factors in the diving beetle Cybister tripunctatus lateralis (Fabricius) (Coleoptera: Dytiscidae) in Japan in recent years, life histories and oviposition patterns were compared among three endangered diving beetle species, Cybister brevis Aubé (qualified by the Japanese Red Data List as ‘near threatened’), Cybister chinensis Motschulsky (vulnerable), and C. tripunctatus lateralis (vulnerable). Oviposition in C. brevis, C. chinensis, and C. tripunctatus lateralis was observed from late April to mid‐June, from late April to early July, and from late May to mid‐August, respectively, under semi‐outdoor conditions. There were no interspecies differences in total hatchling production during the reproductive season. In rearing experiments at various temperatures (20, 23, 25, 28, and 30 °C), the mortality of C. tripunctatus lateralis larvae was higher at 20 °C, and gradually lower with increasing temperature up to 30 °C. Adult body size of females in C. tripunctatus lateralis is larger than that of males but there were no significant differences among temperatures (25–30 °C). Cybister brevis had a higher emergence rate at 23–28 °C than at 20 and 30 °C. In C. brevis, the body size of adults reared at 25 or 28 °C was significantly larger than at other temperatures. Cybister chinensis did not differ in emergence rate and adult body size among the five temperature conditions. The developmental zero (i.e., the lower developmental threshold) from the first instar to adult emergence was 11.1 °C for C. brevis, 8.7 °C for C. chinensis, and 16.8 °C for C. tripunctatus lateralis. We speculate how the influence of global warming may have a positive impact on the growth and survival of C. tripunctatus lateralis.

Sex ratio of the green sea turtle Chelonia mydas (Testudines: Cheloniidae) hatchlings in the Guanahacabibes Peninsula, Cuba

Introduction: Sea turtles have temperature dependent sex determination. The increase in global temperature leads to higher nest temperatures that can cause a prevalence of females, threatening the future of these species. Objective: The present work aims to evaluate the trend of incubation temperatures and the incubation period, as well as to estimate the sex ratio in nests of Chelonia mydas at Antonio and La Barca beaches, Southwestern Cuba, during the seasons from 2012 to 2018. Methods: Temperature data loggers were placed in green turtle nests with a representativeness that varied between the years analyzed. To assess the temporal variation of temperatures and incubation periods, a Kruskal-Wallis test was performed in each case. Sex ratio was estimated from its relation with temperature and incubation duration. Results: At La Barca beach, there was a 1.5 °C increase in the mean nest temperature from 2012 to 2018, although no differences were found in the period from 2015 to 2018. At Antonio beach, there is no trend since no differences were found in the mean nest temperature except for the years 2013 and 2017, which had lower temperatures than the other seasons. In both beaches mean nest temperature exceeded 30 °C in most of the years. As a result, there was a predominance of nests with incubation periods shorter than 55 days. With these values, a female hatchling production over 90 % is expected in both study sites. Conclusions: In correspondence with the registered temperature and incubation period values, most of the years reflect a hatchling production biased towards females in both beaches.

Predicted distributions and abundances of the sea turtle ‘lost years’ in the western North Atlantic Ocean

Oceanic dispersal characterizes the early juvenile life‐stages of numerous marine species of conservation concern. This early stage may be a ‘critical period’ for many species, playing an overriding role in population dynamics. Often, relatively little information is available on their distribution during this period, limiting the effectiveness of efforts to understand environmental and anthropogenic impacts on these species. Here we present a simple model to predict annual variation in the distribution and abundance of oceanic‐stage juvenile sea turtles based on species’ reproductive output, movement and mortality. We simulated dispersal of 25 cohorts (1993–2017) of oceanic‐stage juveniles by tracking the movements of virtual hatchling sea turtles released in a hindcast ocean circulation model. We then used estimates of annual hatchling production from Kemp's ridley Lepidochelys kempii (n = 3), green Chelonia mydas (n = 8) and loggerhead Caretta caretta (n = 5) nesting areas in the northwestern Atlantic (inclusive of the Gulf of Mexico, Caribbean Sea and eastern seaboard of the U.S.) and their stage‐specific mortality rates to weight dispersal predictions. The model's predictions indicate spatial heterogeneity in turtle distribution across their marine range, identify locations of increasing turtle abundance (notably along the U.S. coast), and provide valuable context for temporal variation in the stranding of young sea turtles across the Gulf of Mexico. Further effort to collect demographic, distribution and behavioral data that refine, complement and extend the utility of this modeling approach for sea turtles and other dispersive marine taxa is warranted. Finally, generating these spatially‐explicit predictions of turtle abundance required extensive international collaboration among scientists; our findings indicate that continued conservation of these sea turtle populations and the management of the numerous anthropogenic activities that operate in the northwestern Atlantic Ocean will require similar international coordination.

Effects of local climate on loggerhead hatchling production in Brazil: Implications from climate change

Sea turtle eggs are heavily influenced by the environment in which they incubate, including effects on hatching success and hatchling viability (hatchling production). It is crucial to understand how the hatchling production of sea turtles is influenced by local climate and how potential changes in climate may impact future hatchling production. Generalized Additive Models were used to determine the relationship of six climatic variables at different temporal scales on loggerhead turtle (Caretta caretta) hatchling production at seventeen nesting beaches in Bahia, Espirito Santo, and Rio de Janeiro, Brazil. Using extreme and conservative climate change scenarios throughout the 21st century, potential impacts on future hatching success (the number of hatched eggs in a nest) were predicted using the climatic variable(s) that best described hatchling production at each nesting beach. Air temperature and precipitation were found to be the main drivers of hatchling production throughout Brazil. CMIP5 climate projections are for a warming of air temperature at all sites throughout the 21st century, while projections for precipitation vary regionally. The more tropical nesting beaches in Brazil, such as those in Bahia, are projected to experience declines in hatchling production, while the more temperate nesting beaches, such as those in Rio de Janeiro, are projected to experience increases in hatchling production by the end of the 21st century.

PATHOLOGY OF LEATHERBACK SEA TURTLE (DERMOCHELYS CORIACEA) EMBRYOS AND HATCHLINGS FROM NESTS IN ST. KITTS, WEST INDIES (2015–16)

Sustained hatchling production is a priority for leatherback sea turtle (Dermochelys coriacea) conservation. Yet the species is challenged by notoriously low hatch success, much lower than other species of sea turtles, and the result of a high rate of embryo mortality for which the causes are not understood. The aim of our study was to describe the pathology of embryos and dead-in-nest hatchlings, to help understand the basis for low hatch success in St. Kitts, West Indies. We surveyed two leatherback nesting beaches, Keys and North Friars, in 2015-16. Pathology was present in 38% (32 of 84) of individuals, including renal mineralization (24%, 20 of 83), bacterial pneumonia (12%, 10 of 82), and skeletal muscle necrosis (7%, 6 of 84). Renal mineralization was seen in all stages of development that we examined and was associated with cardiac mineralization in two cases. Bacterial pneumonia affected dead-in-nest hatchlings and late-stage embryos and involved 40% (6 of 15) of nests evaluated, all laid by different mothers. Hematopoiesis was consistently observed in the liver, lung, kidneys, and heart. Gonad was histologically classified as female in 100% (68 of 68) of individuals examined. Rathke's gland was identified in the axillary musculature of 51 individuals, which has not previously been described in leatherbacks. Bacterial pneumonia and renal mineralization were presumed to be significant causes of death in leatherback embryos and hatchlings in St. Kitts. Overrepresentation of females in our study suggested high incubation temperatures in the nests.

Nest-to-Surf Mortality of Loggerhead Sea Turtle (Caretta caretta) Hatchlings on Florida’s East Coast

Sea turtles are vulnerable immediately after emerging from nests and before they reach the surf. Mortality rates during this brief period are largely unknown. Many sea turtle monitoring programs measure hatchling production from nest inventories. These inventories rarely account for post-emergence mortality, leaving an unknown bias in hatchling production estimates. This study addresses the nest-to-surf data gap for Florida’s east coast nesting assemblages of loggerhead sea turtles (Caretta caretta). Five locations were surveyed during the 2016-nesting season. Across all beaches, 7.6% of the observed hatchlings did not survive to reach the water. Mortality sources varied by location. Observed predators include: mammals, birds, and crabs. Hatchling disorientation and misorientation due to photopollution occurred more frequently in urban areas than natural areas. Factors identified as important in hatchling mortality included numbers of hatchlings emerging, nest-to-surf distance, and level of urbanization. The results of this study may help sea turtle nesting managers address nest-to-surf mortality and improve hatchling production estimates.

Microclimatic effects on the incubation success, hatchling morphology and locomotor performance of marine turtles

Global atmospheric temperatures are predicted to rapidly increase within the next hundred years, consequently altering the microclimates of the sand dune environment where marine turtles lay their eggs. High nest temperatures can increase embryonic mortality, decrease hatchling vigour and size (i.e. quality), and also feminises the sex-ratio of clutches. Sand composition, vegetation cover, rainfall and sun exposure affect the temperature of sand surrounding a nest, however the effect of this variability in the beach environment on the incubation success of a sea turtle clutch is still relatively unknown. We conducted a manipulative study on loggerhead turtle nests at Mon Repos, Queensland, Australia, to investigate the effect of ground-cover vegetation vs bare sand and tree-shade vs no shade on incubation success, hatchling morphology and hatchling locomotor performance. Twenty-four nests were used in a two-factor experimental design, with tree-shade/sun and, ground-cover vegetated/cleared as fixed factors. Sun-exposed nests experienced higher nest temperatures (∼2 °C warmer), shorter incubation periods and poorer incubation success than those in tree-shade. Ground-cover-vegetated nests in tree-shade had lower hatching and emergence success (73%, 66% respectively) than sun-exposed nests placed in sites cleared of ground-cover vegetation (79%, 83% respectively). Hatchlings that emerged from cooler, tree-shaded nests were also larger and crawled faster than hatchlings from sun-exposed nests. We suggest for conservation projects on naturally ‘hot’ beaches, active management strategies such as selective groundcover vegetation removal and increased shading could be implemented to increase high quality hatchling production.

Climate change resilience of a globally important sea turtle nesting population.

Few studies have looked into climate change resilience of populations of wild animals. We use a model higher vertebrate, the green sea turtle, as its life history is fundamentally affected by climatic conditions, including temperature-dependent sex determination and obligate use of beaches subject to sea level rise (SLR). We use empirical data from a globally important population in West Africa to assess resistance to climate change within a quantitative framework. We project 200years of primary sex ratios (1900-2100) and create a digital elevation model of the nesting beach to estimate impacts of projected SLR. Primary sex ratio is currently almost balanced, with 52% of hatchlings produced being female. Under IPCC models, we predict: (a) an increase in the proportion of females by 2100 to 76%-93%, but cooler temperatures, both at the end of the nesting season and in shaded areas, will guarantee male hatchling production; (b) IPCC SLR scenarios will lead to 33.4%-43.0% loss of the current nesting area; (c) climate change will contribute to population growth through population feminization, with 32%-64% more nesting females expected by 2120; (d) as incubation temperatures approach lethal levels, however, the population will cease growing and start to decline. Taken together with other factors (degree of foraging plasticity, rookery size and trajectory, and prevailing threats), this nesting population should resist climate change until 2100, and the availability of spatial and temporal microrefugia indicates potential for resilience to predicted impacts, through the evolution of nest site selection or changes in nesting phenology. This represents the most comprehensive assessment to date of climate change resilience of a marine reptile using the most up-to-date IPCC models, appraising the impacts of temperature and SLR, integrated with additional ecological and demographic parameters. We suggest this as a framework for other populations, species and taxa.

Optimism for mitigation of climate warming impacts for sea turtles through nest shading and relocation

Increasing incubation temperatures may threaten the viability of sea turtle populations. We explored opportunities for decreasing incubation temperatures at a Caribbean rookery with extreme female-biased hatchling production. To investigate the effect of artificial shading, temperatures were measured under simple materials (white sheet, white sand, palm leaves). To test natural drivers of incubation temperature, temperatures were measured at average nest depths with shading on two beaches. Results from a pilot experiment suggest the most effective material was palm leaves. Shading decreased temperatures by a mean of 0.60 °C (SE = 0.10 °C, N = 20). Variation between beaches averaged 1.88 °C (SE = 0.13 °C, N = 20). We used long-term rookery data combined with experimental data to estimate the effect on sex ratio: relocation and shading could shift ratios from current ranges (97–100% female) to 60–90% female. A conservation mitigation matrix summarises our evidence that artificial shading and nest relocation are effective, low-cost, low-technology conservation strategies to mitigate impacts of climate warming for sea turtles.

Reproductive parameters as assessment tools for arsenic and chromium induced toxicity in Eudrilus eugeniae

The present study of 28 days was carried out to assess the effect of arsenic and chromium on biomass gain and reproduction parameters (cocoon and hatchling production) of E. eugeniae. The worms were cultured in substrate having different concentrations of arsenic and chromium alongwith control in triplicates. Dose and time dependent decreased in number of adults, cocoon production and hatchling emergence and reduction in growth was observed. In worms exposed to Cr (0.1 ppm), reduction in population (24.66%), body weight (2.44%), cocoon production (47.14%) and hatchling emergence (39.99%) was observed. While As (0.1 ppm) exposure resulted in reduction of adult population (10.66%), body weight (0.24%), cocoon production (37.05%) and hatchling emergence (28.53%) was observed. Cocoon production was observed to be the most sensitive parameter for heavy metal exposure in all treatments. Chromium was observed to be more detrimental to earthworms when compared with arsenic.

Warmer and wetter conditions will reduce offspring production of hawksbill turtles in Brazil under climate change.

Climate change is expected to impact animals that are heavily reliant on environmental factors, such as sea turtles, since the incubation of their eggs, hatching success and sex ratio are influenced by the environment in which eggs incubate. As climate change progresses it is therefore important to understand how climatic conditions influence their reproductive output and the ramifications to population stability. Here, we examined the influences of five climatic variables (air temperature, accumulated and average precipitation, humidity, solar radiation, and wind speed) at different temporal scales on hawksbill sea turtle (Eretmochelys imbricata) hatchling production at ten nesting beaches within two regions of Brazil (five nesting beaches in Rio Grande do Norte and five in Bahia). Air temperature and accumulated precipitation were the main climatic drivers of hawksbill hatching success (number of eggs hatched within a nest) across Brazil and in Rio Grande do Norte, while air temperature and average precipitation were the main climatic drivers of hatching success at Bahia. Solar radiation was the main climatic driver of emergence success (number of hatchlings that emerged from total hatched eggs within a nest) at both regions. Warmer temperatures and higher solar radiation had negative effects on hatchling production, while wetter conditions had a positive effect. Conservative and extreme climate scenarios show air temperatures are projected to increase at this site, while precipitation projections vary between scenarios and regions throughout the 21st century. We predicted hatching success of undisturbed nests (no recorded depredation or storm-related impacts) will decrease in Brazil by 2100 as a result of how this population is influenced by local climate. This study shows the determining effects of different climate variables and their combinations on an important and critically endangered marine species.

Influences of the Local Climate on Loggerhead Hatchling Production in North Florida: Implications From Climate Change

The environment and climate in which sea turtle eggs incubate affects how successful and viable hatchlings are. Therefore, it is crucial to understand how local climate impacts sea turtle hatchling production as well as how potential changes in climate may impact future hatchling production. In this study, we investigated the effects of five different climate variables at different temporal scales on loggerhead sea turtle (Caretta caretta) hatchling production from North Florida, USA. Humidity, air temperature, and accumulated precipitation were the main climatic drivers of hatchling production, while sea surface temperature and wind speed did not demonstrate to have strong effects. Climate projections show air temperatures increasing at the nesting beaches throughout the 21st century, while precipitation and humidity projections vary between sites and projection scenarios. Due to the temperate nature of these nesting beaches, increases in hatching success for nests that incubate undisturbed (not affected by depredation and storm-related impacts) are projected for this region by 2100. This study demonstrates how different climate variables and their interactions can have a determining effect on an important marine species.