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Temperature-dependent sex determination (TSD) is the predominant form of environmental sex determination (ESD) in reptiles, but the adaptive significance of TSD in this group remains unclear. Additionally, the viability of species with TSD may be compromised as climate gets warmer. We simulated population responses in a turtle with TSD to increasing nest temperatures and compared the results to those of a virtual population with genotypic sex determination (GSD) and fixed sex ratios. Then, we assessed the effectiveness of TSD as a mechanism to maintain populations under climate change scenarios. TSD populations were more resilient to increased nest temperatures and mitigated the negative effects of high temperatures by increasing production of female offspring and therefore, future fecundity. That buffered the negative effect of temperature on the population growth. TSD provides an evolutionary advantage to sea turtles. However, this mechanism was only effective over a range of temperatures and will become inefficient as temperatures rise to levels projected by current climate change models. Projected global warming threatens survival of sea turtles, and the IPCC high gas concentration scenario may result in extirpation of the studied population in 50 years. [ABSTRACT FROM AUTHOR]

The article offers information on possible causes of mortality for adult leatherback turtles (Dermochelys coriacea). It states that a switching state-space model was applied to distinguish migratory and area-restricted search behaviors. It indicated a high spatial segregation between East Pacific(EP) and West Pacific(WP) nesting populations.They have high risk of exposure to many different fisheries and more susceptible to any temperature or prey changes that occur in response to climate change.

The high probability of being depredated on the crawl to the water may have influenced the evolutionary processes of hatchling sea turtles on the beach. During this time hatchlings must locate water and move as quickly as possible in order to reduce the time spent on the beach. Hatchling leatherback turtles (Dermochelys coriacea) at Playa Grande, Parque Nacional Marino Las Baulas, Costa Rica, spent on average 34 minutes visible on the beach, covered a distance of 46.8 m, and moved at a rate of 3.11 m/min. During the time on the beach, 12% of hatchlings were eaten by predators, 83% reached the water, and 5% were determined as potential mortalities (hatchlings were stuck on debris, vegetation, or upside down). The main predators of hatchling leatherbacks at Playa Grande were ghost crabs (Ocypode occidentalis), great blue herons (Ardea herodias), and yellow-crowned night herons (Nycticorax violaceus) during the night, and crested caracaras (Caracara plancus) during the day. Tracks left by the hatchlings on the sand were straighter as they approached the water. Dispersion (distance between the 2 outermost tracks coming from a nest) was correlated with number of hatchlings crawling. Hatchling leatherback turtles at Playa Grande are threatened by predation by domestic animals. Hatchling mortality due to human-related activities is likely to increase in the future due to increasing pressure from tourism at Parque Nacional Marino Las Baulas. [ABSTRACT FROM AUTHOR]

1. Pacific leatherback turtle Dermochelys coriacea populations have been declining precipitously. It has been suggested that fishery-associated mortality is the leading factor causing the decline; however, the sensitivity of leatherbacks to climate variability relative to their population ecology is unknown. 2. We investigated the effects of interannual climate variability, as governed by the El Niño Southern Oscillation (ENSO), on leatherback nesting ecology. We used equatorial Pacific sea surface temperature (SST) anomaly data over various time scales derived from both moored buoys and remote satellites as signals of ENSO. We then incorporated these data into a remigration probability model for the largest nesting population of eastern Pacific leatherbacks at Parque Nacional Marino Las Baulas (PNMB), Costa Rica. 3. Our results showed that nesting females of PNMB exhibited a strong sensitivity to ENSO, as reflected in their nesting remigration probabilities. Cool La Niña events corresponded with a higher remigration probability and warm El Niño events corresponded with a lower remigration probability. 4. We suggest that productivity transitions at leatherback foraging areas in the eastern equatorial and south-eastern Pacific in response to El Niño/La Niña events result in variable remigration intervals and thus variable annual egg production. This phenomenon may render the eastern Pacific leatherback population more vulnerable to anthropogenic mortality than other populations. 5. Synthesis and applications. Physical indices of environmental variation can be used to estimate the probability of leatherbacks remigrating to nest at PNMB. This type of modelling approach can be extremely useful for understanding the effects of climatic variation on the population dynamics of sea turtles. Our remigration probability model can be applied to any monitored sea turtle nesting population where nesting site fidelity and beach monitoring coverage remains high. This modelling approach can help nesting beach monitoring programmes forecast remigrant numbers based on prior climate data, and can further quantify anthropogenic mortality by validating survival estimates. [ABSTRACT FROM AUTHOR]

Physiology, environment and life history demands interact to influence marine turtle bioenergetics and activity. However, metabolism and diving behavior of free-swimming marine turtles have not been measured simultaneously. Using doubly labeled water, we obtained the first field metabolic rates (FMRs; 0.20–0.74 W kg-1) and water fluxes (16–30% TBW day-1, where TBW=total body water) for free-ranging marine turtles and combined these data with dive information from electronic archival tags to investigate the bioenergetics and diving activity of reproductive adult female leatherback turtles Dermochelys coriacea. Mean dive durations (7.8±2.4 min (±1 S.D.), bottom times (2.7±0.8 min), and percentage of time spent in water temperatures (Tw) ≤24°C (9.5±5.7%) increased with increasing mean maximum dive depths (22.6±7.1 m; all P≤0.001). The FMRs increased with longer mean dive durations, bottom times and surface intervals and increased time spent in Tw≤24°C (all r²≥0.99). This suggests that low FMRs and activity levels, combined with shuttling between different water temperatures, could allow leatherbacks to avoid overheating while in warm tropical waters. Additionally, internesting leatherback dive durations were consistently shorter than aerobic dive limits calculated from our FMRs (11.7–44.3 min). Our results indicate that internesting female leatherbacks maintained low FMRs and activity levels, thereby spending relatively little energy while active at sea. Future studies should incorporate data on metabolic rate, dive patterns, water temperatures, and body temperatures to develop further the relationship between physiological and life history demands and marine turtle bioenergetics and activity. [ABSTRACT FROM AUTHOR]

Abstract: Limb preference is a behavioral indicator of lateralized brain function that was recently elucidated experimentally in lower vertebrates. We assessed natural spontaneous limb use of nesting eastern Pacific leatherback turtles by recording which hindlimb flipper was extended overtop the cloaca to cover the egg chamber during oviposition. We found a population level right bias in 1889 observations of 361 individuals. This is the first report of a limb preference in Testudinata. [Copyright &y& Elsevier]

Abstract: We analyzed some of the primary biological and physical dynamics within the eastern Pacific leatherback turtle (Dermochelys coriacea) migration area in relation to ENSO and leatherback nesting ecology at Parque Nacional Marino Las Baulas (PNMB), Costa Rica. We used data from remote sensing to calculate resource availability via a net primary production (NPP) model, and to analyze the physical dynamics of the migration area via sea surface temperature fronts. Within the migration area, NPP north of 15°S was highly governed by interannual variability as indicated by the Multivariate ENSO Index while south of 15°S, production had a more seasonal signal. Nesting peaks of leatherbacks at PNMB were associated with cool, highly productive La Niña events and with large-scale equatorial phytoplankton blooms encompassing 110°W that were induced by iron enrichment following the termination of El Niño events. Resource availability in the northern migration area (eastern equatorial Pacific) appeared to determine the nesting response for the population at PNMB, Costa Rica. We suggest that ENSO significantly influences the nesting ecology of leatherbacks at PNMB because the majority of the population consists of pelagic foragers that strictly rely on the eastern equatorial Pacific for prey consumption prior to the nesting season. Coastal foragers may be a minority in the population because of high mortality rates associated with coastal gillnet fisheries along Central and South America. [Copyright &y& Elsevier]

Abstract: Relationships between egg size, egg components, and neonate size have been investigated across a wide range of oviparous taxa. Differences in egg traits among taxa reflect not only phylogenetic differences, but also interactions between biotic (i.e., maternal resource allocation) and abiotic (i.e. nest environment conditions) factors. We examined relationships between egg mass, egg composition, and hatchling size in leatherback turtles (Dermochelys coriacea) because of the unique egg and reproductive characteristics of this species and of sea turtles in general. Albumen comprised 63.0%±2.8% (mean±S.D.) of egg mass and explained most of the variation in egg mass, whereas yolk comprised only 33.0%±2.7%. Additionally, leatherback albumen dry mass was ∼16% of albumen wet mass. Whereas hatchling mass increased significantly with egg mass (n =218 clutches), hatchling mass increased by only approximately 2 g for each 10 g increase in egg mass and was approximately 10–20 g greater than yolk mass. Taken together, our results indicate that albumen might play a particularly significant role in leatherback embryonic development, and that leatherback eggs are both capable of water uptake from the nest substrate and also possess a large reservoir of water in the albumen. Relationships between egg mass and egg components, such as variation in egg mass being largely explained by variation in albumen mass and egg mass containing a relatively high proportion of albumen solids, are more similar to bird eggs than to eggs of other non-avian reptiles. However, hatchling mass correlates more with yolk mass than with albumen mass, unlike patterns observed in bird eggs of similar composition. [Copyright &y& Elsevier]