Global analysis of the effect of local climate on the hatchling output of leatherback turtles

Santidrián Tomillo, Pilar et al.The most recent climate change projections show a global increase in temperatures along with precipitation changes throughout the 21 century. However, regional projections do not always match global projections and species with global distributions may exhibit varying regional susceptibility to climate change. Here we show the effect of local climatic conditions on the hatchling output of leatherback turtles (Dermochelys coriacea) at four nesting sites encompassing the Pacific, Atlantic and Indian Oceans. We found a heterogeneous effect of climate. Hatchling output increased with long-term precipitation in areas with dry climatic conditions (Playa Grande, Pacific Ocean and Sandy Point, Caribbean Sea), but the effect varied in areas where precipitation was high (Pacuare, Caribbean Sea) and was not detected at the temperate site (Maputaland, Indian Ocean). High air temperature reduced hatchling output only at the area experiencing seasonal droughts (Playa Grande). Climatic projections showed a drastic increase in air temperature and a mild decrease in precipitation at all sites by 2100. The most unfavorable conditions were projected for Sandy Point where hatching success has already declined over time along with precipitation levels. The heterogeneous effect of climate may lead to local extinctions of leatherback turtles in some areas but survival in others by 2100.Funding for the study was provided by a Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme. Specific funding for each site was provided by the Earthwatch Institute, the Betz Chair of Environmental Science at Drexel University, the Schrey Chair of Biology at IPFW and The Leatherback Trust (Playa Grande), the US Fish and Wildlife Service (USFWS) (Sandy Point), the Endangered Wildlife Trust (Pacuare) and NRF/Thuthuka and NMMU Postgraduate Research Scholarship (Maputaland)Peer Reviewe

Factors affecting population dynamics of eastern pacific leatherback turtles (Dermochelys coriacea)

The leatherback turtle (Dermochelys coriacea) is critically endangered. The population of leatherbacks that nest at Parque Nacional Marino Las Baulas, in Costa Rica declined by 95% in less than 20 years. Annual mortality rate of adults was higher than expected in a natural population and mortality rates of juveniles could double those of a stable population. Conservation efforts since the Park was established in 1991 resulted in higher production of hatchlings per egg laid. However, the overall hatchling output decreased because of the decreasing number of nesting turtles. Simulations on the effect of egg poaching showed that poaching was the most important cause of population decline at Las Baulas. Heavy poaching resulted in a stepwise decline in number of nesting turtles due to consecutive reductions in each nesting stage. The nesting population declined faster and was extirpated sooner with 90% egg poaching than with 20% adult mortality. However, both protection in the ocean from fishing and on the beach are critical to the survival of the population. Behavior of hatchling leatherback turtles on the walk to the water was driven by predation risk. Hatchling leatherback turtles decreased predation risk emerging in groups and dispersing. Straightness of tracks increased during the process of departure and was lower in areas of higher exposure to light pollution. Nest success of leatherback turtles was driven by environmental variability. High temperatures in the nest reduced its success, and high rainfall and low ambient temperatures resulted in higher production of hatchlings. Predicted emergence success was related to El Niño Southern Oscillation (ENSO). Leatherback female turtles increased reproductive success over time by increasing number of eggs, number of clutches and arriving earlier in the season, when hatchling production was greater.In conclusion, the population decline at Las Baulas was mainly caused by egg poaching but is still threatened by high mortality in the ocean. Conservation efforts have been efficient at increasing hatchling production. However, the stochastic nature of nest success and consequently, recruitment rate, may increase the risk of extinction of a population already reduced from past poaching and fisheries.Ph.D., Biological Sciences -- Drexel University, 200

Colapsos depredador-presa en el límite de la distribución del depredador: el caso de los clupeidos y el arao común (Uria aalge) en Iberia

The spatial structuring of seabird populations makes individual colonies very dependent on regional factors. That is especially the case in small edge populations located far from large colonies. We analysed retrospectively the poorly known collapse, some 50 years ago (around 1962-1973), of a relatively small population of breeding common guillemots (Uria aalge) located at their southernmost limit of distribution in Europe (NW Iberia). We assumed that guillemots behaved locally as facultative specialists in small pelagic fish due to the occurrence of a strong clupeid fishery, and we studied the association between the guillemot collapse and annual regional landings of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus), used as a proxy of total stock size. The overall relationship between ln-transformed guillemot counts (May-June) and ln-transformed sardine landings (May-October) was stronger than the fit on untransformed variables (r2 =0.52 vs. 0.27), indicating an exponential relationship between the non-transformed variables. This relationship was somewhat stronger and linear after the collapse, when only a few tens of guillemots remaining (r2 =0.60). A strong regime shift in sardine landings was detected in 1968 and also in anchovy landings in 1969. The overall relationship between guillemot numbers and anchovy landings was linear and strong (r2 =0.72) but completely dependent on the large 1960s estimate of guillemots. However, no relationship was found between guillemot numbers and anchovy landings (April-June) after the guillemot collapse. The most likely period for the guillemot collapse was therefore 1968-1970, as seabird colonies are known to collapse immediately after their staple prey crashes. Local guillemot colonies were not subsequently rescued by immigration and have remained empty or almost empty until present, showing the high sensitivity of edge populations to environmental variability at the regional scale.Las poblaciones de aves marinas están espacialmente estructuradas y eso hace que las colonias individuales dependan mucho de factores regionales. Ese es especialmente el caso en pequeñas poblaciones ubicadas lejos de grandes colonias. Aquí analizamos retrospectivamente el colapso de una población relativamente pequeña de araos comunes (Uria aalge) reproductores, ubicada en su límite de distribución sur en Europa (NO de Iberia), sucedido hace unos 50 años (alrededor de 1962-1973). Asumimos que los araos reproductores se comportaron localmente como especialistas facultativos en el consumo de peces pelágicos pequeños debido a la existencia de una potente pesquería de clupeidos y estudiamos la asociación entre el colapso del arao y los desembarcos regionales anuales de sardina (Sardina pilchardus) y boquerón (Engraulis encrasicolus), utilizados como un proxy del tamaño total del stock. La relación general entre los conteos de araos (mayo-junio), transformados mediante el logaritmo neperiano, y los desembarcos de sardina (mayo-octubre) transformados, fue más fuerte que el ajuste de las variables no transformadas (r2 =0.52 frente a 0.27), lo que indica una relación exponencial entre las variables no transformadas. Esta relación fue algo más fuerte y lineal después del colapso, cuando solo quedaron unas pocas decenas de araos (r2 =0,60). Se detectó un fuerte cambio de régimen en los desembarcos de sardina en 1968 y también en los de boquerón en 1969. La relación entre el número de araos y los desembarcos de boquerón fue lineal y fuerte (r2 =0.72). Sin embargo, no se encontró relación entre el número de araos y los desembarcos de boquerón (abril-junio) después del colapso del arao. La fecha más probable para el colapso del arao, por lo tanto, fue el período 1968-1970, ya que las colonias de aves marinas colapsan inmediatamente después de que sus presas principales hayan colapsado. Las colonias locales de araos no fueron rescatadas posteriormente por inmigración y han permanecido vacías o casi vacías hasta el presente, lo que demuestra la alta sensibilidad a la variabilidad ambiental a escala regional de las poblaciones ubicadas en el límite de la distribución de la especie

Open Access perpetuates differences between higher- and lower-income countries

We dedicate this letter to the memory of Sue Kilham, an outstanding mentor and ecologist.Peer reviewe

Climate Driven Egg and Hatchling Mortality Threatens Survival of Eastern Pacific Leatherback Turtles

Egg-burying reptiles need relatively stable temperature and humidity in the substrate surrounding their eggs for successful development and hatchling emergence. Here we show that egg and hatchling mortality of leatherback turtles (Dermochelys coriacea) in northwest Costa Rica were affected by climatic variability (precipitation and air temperature) driven by the El Niño Southern Oscillation (ENSO). Drier and warmer conditions associated with El Niño increased egg and hatchling mortality. The fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC) projects a warming and drying in Central America and other regions of the World, under the SRES A2 development scenario. Using projections from an ensemble of global climate models contributed to the IPCC report, we project that egg and hatchling survival will rapidly decline in the region over the next 100 years by ∼50–60%, due to warming and drying in northwestern Costa Rica, threatening the survival of leatherback turtles. Warming and drying trends may also threaten the survival of sea turtles in other areas affected by similar climate changes

Embryonic Death Is Linked to Maternal Identity in the Leatherback Turtle (Dermochelys coriacea)

Leatherback turtles have an average global hatching success rate of ∼50%, lower than other marine turtle species. Embryonic death has been linked to environmental factors such as precipitation and temperature, although, there is still a lot of variability that remains to be explained. We examined how nesting season, the time of nesting each season, the relative position of each clutch laid by each female each season, maternal identity and associated factors such as reproductive experience of the female (new nester versus remigrant) and period of egg retention between clutches (interclutch interval) affected hatching success and stage of embryonic death in failed eggs of leatherback turtles nesting at Playa Grande, Costa Rica. Data were collected during five nesting seasons from 2004/05 to 2008/09. Mean hatching success was 50.4%. Nesting season significantly influenced hatching success in addition to early and late stage embryonic death. Neither clutch position nor nesting time during the season had a significant affect on hatching success or the stage of embryonic death. Some leatherback females consistently produced nests with higher hatching success rates than others. Remigrant females arrived earlier to nest, produced more clutches and had higher rates of hatching success than new nesters. Reproductive experience did not affect stage of death or the duration of the interclutch interval. The length of interclutch interval had a significant affect on the proportion of eggs that failed in each clutch and the developmental stage they died at. Intrinsic factors such as maternal identity are playing a role in affecting embryonic death in the leatherback turtle

When population-advantageous primary sex ratios are female-biased: changing concepts to facilitate climate change management in sea turtles

Sea turtles have temperature-dependent sex determination. Because females are produced at high temperatures, increasing global temperature may lead to population feminization. Primary sex ratios (PSR) of sea turtle hatchlings are naturally female-biased, but this translates into a more balanced operational sex ratio because male turtles reproduce more often than females. As a consequence, a balanced PSR and the temperature that produces it (pivotal temperature) are of limited use to guide climate mitigation management because an equal PSR may be demographically suboptimal. Here, I define population-advantageous primary sex ratios (PA-PSR) as the PSR that will tend to be in equilibrium in a population and that will result in balanced operational sex ratios; I then estimate PA-PSR for different reproductive frequencies (years elapsed between reproductive seasons) of adult female and male turtles. I also define population equilibrium temperature (PET) as the temperature that would result in the equilibrium PSR of hatchlings (i.e., PA-PSR). These concepts may help assess the influence of rising temperatures on populations, as they can better indicate if PSRs depart from those at equilibrium. I compared PA-PSR and beach PSR for two populations of sea turtles for which male and female remigration intervals were known and found that a mild or no feminization over the PA-PSR may be occurring. Because PSR varies inter-annually, and hatchlings coming from beaches of different thermal conditions could recruit to the same population, it is critical to estimate beach PSR at the right temporal and spatial scales. Climate mitigation strategies based on these concepts could provide better management guidance for conservation practitioners. Similar approaches could be considered for other female-biased species with temperature-dependent sex determination.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

La pesca amenaza a la tortuga laúd en el Pacífico Oriental

Peer reviewe

El Niño events and chlorophyll levels affect the reproductive frequency but not the seasonal reproductive output of East Pacific green turtles

The El Niño-Southern Oscillation (ENSO), which includes El Niño and La Niña phases, affects oceanographic conditions and primary productivity of marine ecosystems at a global scale. During El Niño events, warm temperatures in the central and eastern tropical Pacific de crease primary productivity, affecting the biology of many species including sea turtles. We aimed to determine the effect of ENSO (as a global index) and primary productivity in the foraging areas (as a local index) on remigration intervals (number of years between nesting seasons) and seasonal reproductive output (clutch size and number of clutches in a season) of green turtles Chelonia mydas in the North Pacific off Costa Rica, an area highly influenced by ENSO. We used the Multivariate ENSO Index (MEI) and mean values of chlorophyll a from previously identified feeding areas for this population over different time periods (up to 3 yr before the nesting season). Chlorophyll a levels in foraging areas and MEI strongly influenced the reproductive frequency of green turtles. Variability in the remigration intervals was better explained by models that in - cluded chlorophyll levels 2 and 3 yr before the onset of the nesting season and MEI conditions in the previous 3 yr. Models using global and local indexes were equally good at predicting changes in the remigration intervals. Positive values of MEI (El Niño phase) and lower levels of chlorophyll a corresponded to longer remigration intervals. No statistically significant relationships were found between seasonal reproductive output and MEI or chlorophyll a levels. As El Niño events may become more frequent and last longer due to climate change, the lifetime reproductive output of green turtles in this area may be compromised in the future