Richard D. Reina

Nesting Ecology of the Leatherback Turtle, Dermochelys coriacea, at Parque Nacional Marino Las Baulas, Costa Rica: 1988–1989 to 1999–2000

Abstract We collected data on nesting ecology and identified individual turtles that nested at Parque Nacional Las Baulas, Costa Rica, one of the few remaining nesting sites for Pacific leatherbacks, from 1988–1989 to 1999–2000. We tagged individual female turtles with flipper tags and later with Passive Integrated Transponder (PIT) tags that permitted permanent identification. During the full calendars years of 1990 and 1995, over 93% of nests were laid between the beginning of October and the end of February. We found that 92.4 ± 1% of nesting attempts resulted in successful oviposition, with a mean clutch size of 64.7 ± 1.4 yolked and 38.5 ± 1.0 yolkless eggs (n = 1389). Mean standard curved carapace length and curved carapace width during the surveyed years ranged from 144.4 ± 0.6 cm to 147.6 ± 0.3 cm and from 103.9 ± 0.3 cm to 105.5 ± 0.6 cm, respectively. Reproductive output as determined by estimated clutch frequency (ECF) ranged from 4.3 ± 0.2 to 7.9 ± 0.3 clutches per female per nesting season. The mean period between nesting seasons for an individual turtle was 3.7 ± 0.2 years; only 15% of turtles tagged in 1993/1994 returned to nest again within six years. The nesting population declined from 1367 adult females in 1988/1989 to 231 in 1999/2000. The decline in the nesting population was apparently because of the low incidence of turtles returning to nest in more than one season.

Interpreting indices of physiological stress in free-living vertebrates

When vertebrate physiological ecologists use the terms ‘stress’ or ‘physiological stress’, they typically mean the level of hypothalamus–pituitary–adrenal (HPA-) axis activation. Measurements of stress hormone concentrations (e.g. glucocorticoids in blood, urine or faeces), leukocytes (e.g. the neutrophil–lymphocyte ratio or heterophil equivalent), immunofunction (e.g. innate, cell-mediated or humoral immunity measures) and regenerative anaemia (e.g. mean erythrocyte volume and red blood cell distribution width) have all been used to estimate HPA-axis activity in free-living vertebrates. Stress metrics have provided insights into aspects of autecology or population regulation that could not have been easily obtained using other indices of population wellbeing, such as body condition or relative abundance. However, short- and long-term stress (often problematically termed acute and chronic stress, respectively) can interact in unpredictable ways. When animals experience trapping and handling stress before blood, faeces and/or urine is sampled, the interaction of short- and long-term stress can confound interpretation of the data, a fact not always acknowledged in studies of stress in free-living vertebrates. This review examines how stress metrics can be confounded when estimates of HPA-axis activation are collected for free-living vertebrates and outlines some approaches that can be used to help circumvent the influence of potentially confounding factors.

Biotic and Abiotic Factors Affect the Nest Environment of Embryonic Leatherback Turtles, Dermochelys coriacea

Clutches of leatherback turtles, Dermochelys coriacea, have lower hatching success than those of other sea turtles, but causes of high embryonic mortality are unknown. We measured characteristics of clutches along with spatial and temporal changes in PO2 and temperature during incubation to determine the extent to which they affected the developmental environment of leatherback embryos. Minimum PO2 in nests decreased as both the total number and mass of metabolizing embryos increased. Increases in both the number and mass of metabolizing embryos caused an increase in maximum nest temperature. However, neither PO2 nor temperature was correlated with hatching success. Our measurements of relatively high nest PO2 (lowest 17.1 kPa or 16.9% O2) indicate that hypoxia apparently does not cause the low hatching success of leatherback clutches. Oxygen partial pressure increased and temperature decreased from the center toward the periphery of leatherback nests. We inferred from these measurements that positions of eggs within nests vary in quality and potentially affect overall developmental success of entire clutches. The large metabolic mass of leatherback clutches and limits to gas flux imposed by the sand create a situation in which leatherback embryos collectively affect their own environment.

Effects of salinity on the survival, growth and development of tadpoles of the brown tree frog, Litoria ewingii

We investigated the effects of 4% seawater (sw), 8% sw, 12% sw and 16% sw (1.4 g NaCl L–1, 2.8 g NaCl L–1, 4.2 g NaCl L–1 and 5.6 g NaCl L–1, respectively) on survival, mass and development of larvae of the brown tree frog, Litoria ewingii. Salinity of 16% sw significantly decreased survival of tadpoles such that 39% of tadpoles in 16% sw treatment survived to metamorphosis compared with 92% in the control group (freshwater). Growth (mass) of 16% sw tadpoles (0.048 g ± 0.005 g) slowed significantly during early development compared with control tadpoles (0.105 g ± 0.004 g); however, there was no significant difference in final metamorphosis mass between 16% sw (0.192 g ± 0.008 g) and control tadpoles (0.226 ± 0.006 g). Time taken to reach metamorphosis was greater for 16% sw tadpoles (84 ± 1.8 days) than for control tadpoles (55 ± 0.84 days). Tadpoles at salinity concentrations of 4% sw, 8% sw and 12% sw were significantly heavier than control tadpoles at metamorphosis. Our results show that moderate levels of salinity (16% sw) are sufficient to significantly reduce survival and retard development of tadpoles of L. ewingii.

Reassessment of the Leatherback Turtle (Dermochelys coriacea) Nesting Population at Parque Nacional Marino Las Baulas, Costa Rica: Effects of Conservation Efforts

ABSTRACT The number of leatherback turtles (Dermochelys coriacea) nesting at Parque Marino Las Baulas declined precipitously in the 15 years that we monitored the population (1988–1989 to 2003–2004). We estimate that the annual survival rate of adults was 0.78 (95% CI: 0.75–0.80) and that mortality rates for juveniles and subadults in the ocean appear to be double those of a stable population. The proportion of hatchlings produced from deposited eggs increased since the park was established as a result of conservation practices. Because the number of nesting females decreased, the overall production of hatchlings per season declined but was much greater than would be expected without protection efforts. There were similar numbers of hatchlings leaving the beaches of Las Baulas in 1998–2003, with 68 to 188 nesting females under the current conservation regime as there were in 1988–1989 with ca. 1500 nesting females and no park. Female leatherback turtles that nest at Las Baulas have a high level of exchange between nesting beaches; thus, protection of both Playa Grande and Playa Langosta is critical for the survival of the population. Despite current protection efforts, the population at Las Baulas is still threatened by mortality at sea and development on and behind the nesting beaches.

Nest site fidelity of leatherback turtles at Playa Grande, Costa Rica

Abstract The possibility of nest site fidelity of leatherback turtles, Dermochelys coriacea, raises concerns about the merit of translocating poorly located clutches to a safe hatchery. Specifically, if some females habitually nest in areas where the probability of egg survival is low because of tidal inundation, nest relocation may inadvertently select for turtles that make poor nest site selections. We investigate the nest site fidelity of leatherbacks by studying consecutive nest site selections by leatherbacks at Playa Grande, Costa Rica, from 1993 to 2001. Along the ocean-to-vegetation axis, consecutive nest placements were independent (G42=4.737, P=0.315). Regardless of previous zone choices, leatherbacks typically nested in the open beach above the high tide line and away from vegetation. Thus, concerns about translocation of poorly located nests are unfounded. Along the coastal axis, however, an independence model was rejected (G362=145.179, P 0.001 ). The log-linear model-based analysis we developed and applied indicated that the pattern of dependence in nest site locations is more consistent with a hypothesis of spatial proximity in which leatherbacks simply nest close to the site of the previous nest than it is with a hypothesis of intrinsic fidelity to a specific location on the beach. Our model-based approach is suitable for other settings where longitudinal nesting data are available.

The Physiological Response of Port Jackson Sharks and Australian Swellsharks to Sedation, Gill-Net Capture, and Repeated Sampling in Captivity

Abstract Studying postrelease effects of fisheries capture on chondrichthyans in the wild poses considerable logistical challenges. We report a laboratory-based technique to (1) simulate gill-net capture of sharks, which allows monitoring the condition of animals during recovery from a controlled capture event, and (2) assess effects of sedation, serial blood sampling, and repeated exposure to experimental treatment on stress-related blood variables. Exposing Port Jackson sharks Heterodontus portusjacksoni and Australian swellsharks Cephaloscyllium laticeps to 30 min of simulated gill-net capture elicited behavioral stress (struggling and elevated ventilation rate) and minor physiological stress (elevated plasma lactate) responses but did not cause any mortality. Sedation of Australian swellsharks affected some stress-related blood variables. Repeated handling of Port Jackson sharks and Australian swellsharks at short intervals may result in elevated stress levels, but repeated exposure to simulated captu...

Multiple distant origins for green sea turtles aggregating off Gorgona Island in the Colombian eastern Pacific.

Mitochondrial DNA analyses have been useful for resolving maternal lineages and migratory behavior to foraging grounds (FG) in sea turtles. However, little is known about source rookeries and haplotype composition of foraging green turtle aggregations in the southeastern Pacific. We used mitochondrial DNA control region sequences to identify the haplotype composition of 55 green turtles, Chelonia mydas, captured in foraging grounds of Gorgona National Park in the Colombian Pacific. Amplified fragments of the control region (457 bp) revealed the presence of seven haplotypes, with haplotype (h) and nucleotide (π) diversities of h = 0.300±0.080 and π = 0.009±0.005 respectively. The most common haplotype was CMP4 observed in 83% of individuals, followed by CMP22 (5%). The genetic composition of the Gorgona foraging population primarily comprised haplotypes that have been found at eastern Pacific rookeries including Mexico and the Galapagos, as well as haplotypes of unknown stock origin that likely originated from more distant western Pacific rookeries. Mixed stock analysis suggests that the Gorgona FG population is comprised mostly of animals from the Galapagos rookery (80%). Lagrangian drifter data showed that movement of turtles along the eastern Pacific coast and eastward from distant western and central Pacific sites was possible through passive drift. Our results highlight the importance of this protected area for conservation management of green turtles recruited from distant sites along the eastern Pacific Ocean.

Immediate and delayed effects of gill-net capture on acid-base balance and intramuscular lactate concentration of gummy sharks, Mustelus antarcticus☆

Many sharks are captured as untargeted by-catch during commercial fishing operations and are subsequently discarded. A reliable assessment of the proportion of discarded sharks that die post-release as a result of excessive physiological stress is important for fisheries management and conservation purposes, but a reliable physiological predictor of post-release mortality has not been identified. To investigate effects of gill-net capture on the acid-base balance of sharks, we exposed gummy sharks, Mustelus antarcticus, to 60 min of gill-net capture in a controlled setting, and obtained multiple blood and muscle tissue samples during a 72-h recovery period following the capture event. Overall mortality of gummy sharks was low (9%). Blood pH was significantly depressed immediately after the capture event due to a combination of respiratory and metabolic acidosis. Maximum concentrations of plasma lactate (9.9 ± 1.5 mmol L(-1)) were measured 3h after the capture event. Maximum intramuscular lactate concentrations (37.0 ± 4.6 μmol g(-1)) were measured immediately after the capture event, and intramuscular lactate concentrations were substantially higher than plasma lactate concentrations at all times. Sharks in poor condition had low blood pH and high intramuscular lactate concentration, but blood pH does not appear to be a reliable predictor of survival. Suitability of intramuscular lactate concentration as predictor of delayed mortality deserves further investigation.

Arrested embryonic development: a review of strategies to delay hatching in egg-laying reptiles.

Arrested embryonic development involves the downregulation or cessation of active cell division and metabolic activity, and the capability of an animal to arrest embryonic development results in temporal plasticity of the duration of embryonic period. Arrested embryonic development is an important reproductive strategy for egg-laying animals that provide no parental care after oviposition. In this review, we discuss each type of embryonic developmental arrest used by oviparous reptiles. Environmental pressures that might have directed the evolution of arrest are addressed and we present previously undiscussed environmentally dependent physiological processes that may occur in the egg to bring about arrest. Areas for future research are proposed to clarify how ecology affects the phenotype of developing embryos. We hypothesize that oviparous reptilian mothers are capable of providing their embryos with a level of phenotypic adaptation to local environmental conditions by incorporating maternal factors into the internal environment of the egg that result in different levels of developmental sensitivity to environmental conditions after they are laid.