Heredia, Costa Rica
Heredia, Costa Rica

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Bailey H.,University of Maryland Center for Environmental Science | Bailey H.,National Oceanic and Atmospheric Administration | Benson S.R.,National Oceanic and Atmospheric Administration | Shillinger G.L.,Stanford University | And 14 more authors.
Ecological Applications | Year: 2012

Interactions with fisheries are believed to be a major cause of mortality for adult leatherback turtles (Dermochelys coriacea), which is of particular concern in the Pacific Ocean, where they have been rapidly declining. In order to identify where these interactions are occurring and how they may be reduced, it is essential first to understand the movements and behavior of leatherback turtles. There are two regional nesting populations in the East Pacific (EP) and West Pacific (WP), comprising multiple nesting sites. We synthesized tracking data from the two populations and compared their movement patterns. A switching state-space model was applied to 135 Argos satellite tracks to account for observation error, and to distinguish between migratory and area-restricted search behaviors. The tracking data, from the largest leatherback data set ever assembled, indicated that there was a high degree of spatial segregation between EP and WP leatherbacks. Area-restricted search behavior mainly occurred in the southeast Pacific for the EP leatherbacks, whereas the WP leatherbacks had several different search areas in the California Current, central North Pacific, South China Sea, off eastern Indonesia, and off southeastern Australia. We also extracted remotely sensed oceanographic data and applied a generalized linear mixed model to determine if leatherbacks exhibited different behavior in relation to environmental variables. For the WP population, the probability of area-restricted search behavior was positively correlated with chlorophyll-a concentration. This response was less strong in the EP population, but these turtles had a higher probability of search behavior where there was greater Ekman upwelling, which may increase the transport of nutrients and consequently prey availability. These divergent responses to oceanographic conditions have implications for leatherback vulnerability to fisheries interactions and to the effects of climate change. The occurrence of leatherback turtles within both coastal and pelagic areas means they have a high risk of exposure to many different fisheries, which may be very distant from their nesting sites. The EP leatherbacks have more limited foraging grounds than the WP leatherbacks, which could make them more susceptible to any temperature or prey changes that occur in response to climate change. © 2012 by the Ecological Society of America.


Shillinger G.L.,Stanford University | Swithenbank A.M.,Stanford University | Bograd S.J.,National Oceanic and Atmospheric Administration | Bailey H.,National Oceanic and Atmospheric Administration | And 6 more authors.
Endangered Species Research | Year: 2010

The numbers of leatherback turtles Dermochelys coriacea in the eastern Pacific Ocean have declined by up to 90% in the past 2 decades. Initially, egg harvesting was determined to be the largest causative factor, but now that this has been eliminated, high estimated adult mortality from fisheries bycatch poses the single greatest threat to this population. During the nesting season, adult female leatherback turtles nest multiple times and occupy coastal marine habitats near their nesting beaches. In this study, we characterize the interannual variability of high-use internesting habitats used by 44 (out of 46 total) female leatherback turtles that were satellite-tagged at Playa Grande, Costa Rica, from 2004 to 2007. A total of 1135 d of internesting movements were recorded across 3 tracking years. The core 25% utilization distribution (UD) remained predominantly centered within the marine protected area, Parque Nacional Marino Las Baulas (PNMB). The turtles generally dispersed in a northward or southward direction over the shallow continental shelf framing Costa Rica's Nicoya Peninsula. However, there was considerable interannual variation in the shape and area of the larger UD polygons, which was driven by variability in the thermal environment. The maximum swimming speeds and distance traveled from the nesting beach occurred during 2007. Significantly deeper and longer dive durations to cooler temperatures also occurred in this year, which may have been in response to the warming trend from the south driven by the strong Costa Rica Coastal Current. Our findings, therefore, validate the importance of PNMB as a critical habitat for internesting leatherback turtles, but also suggest that a latitudinal expansion of the park is warranted. © Inter-Research 2010.


Santidrian Tomillo P.,CSIC - Mediterranean Institute for Advanced Studies | Oro D.,CSIC - Mediterranean Institute for Advanced Studies | Paladino F.V.,The Leatherback Trust | Paladino F.V.,Indiana University | And 4 more authors.
Biological Conservation | Year: 2014

Sex of offspring in most turtles is determined by temperature-dependent sex determination (TSD). In sea turtles, higher incubation temperatures produce female hatchlings and primary sex ratios are often highly female-biased. Because of the current rate of climate warming, highly female-biased sex ratios have raised concern among scientists and managers because populations might become too female biased for genetic viability.We tested the effects of higher incubation temperatures on embryo and hatchling mortality and on sex ratios in a population of leatherback turtles (Dermochelys coriacea) in the eastern Pacific. The long-term study provided a large sample size in a location influenced by El Niño Southern Oscillation that resulted in highly variable climatic conditions between seasons. High temperatures reduced emergence success. Output of female hatchlings increased with incubation temperature as it reached the upper end of the transitional range (range of temperatures that produce both sexes) (30. °C) and decreased afterwards because high temperatures increased mortality of 'female clutches'. Effect of temperature on female hatchling output lessened female-biased sex ratios from 85% female primary sex ratios to 79% secondary sex ratios (sex ratios of total number of hatchlings emerged). If male turtles reproduce more often than females, operational sex ratios will be closer to 1:1. Female-biased primary sex ratios should not raise concerns by default, but climate change may still threaten populations by reducing hatchling output and increasing frequency of seasons with 100% female production. Clutch relocation to cooler conditions may alter sex ratios and should be used cautiously unless temperatures are so high that no hatchlings survive. In addition, it is unknown what differential survival of male versus female hatchlings may have on the eventual adult sex ratio after they enter the ocean and disperse. © 2014 Elsevier Ltd.


Shillinger G.L.,Stanford University | Shillinger G.L.,Center for Ocean Solutions | Swithenbank A.M.,Stanford University | Bailey H.,National Oceanic and Atmospheric Administration | And 9 more authors.
Marine Ecology Progress Series | Year: 2011

Leatherback turtles are the largest and widest ranging turtle species, and spend much of their time in the offshore pelagic environment. However, the high seas have thus far received little management attention to protect their ecosystems and biodiversity. We tagged 46 female leatherback turtles with satellite transmitters at Playa Grande, Costa Rica from 2004 to 2007. In the present study, we analyzed the vertical and horizontal habitat preferences of these leatherback turtles in the South Pacific Ocean. The turtles exhibited short, shallow dives during their migration southward (mean depth: 45 m; mean duration: 23.6 min), followed by deeper, longer dives (mean depth: 56.7 m; mean duration: 26.4 min) in the South Pacific Gyre that probably indicated searching for prey. We integrated the horizontal movements with remotely sensed oceanographic data to determine the turtles' response to the environment, and applied this information to recommendations for conservation in the pelagic environment. A generalized additive mixed model applied to the daily turtle travel rates confirmed that slower travel rates occurred at cooler sea surface temperatures, higher chlorophyll a concentration and stronger vertical Ekman upwelling, all of which are considered favorable foraging conditions. The southern terminus (35 to 37° S) of the leatherback tracks was also in an area of increased mesoscale activity that might act as a physical mechanism to aggregate their prey, gelatinous zooplankton. However, this could also act as a thermal limit to their distribution. This characterization of leatherback habitat use could aid the development of management efforts within the South Pacific Ocean to reduce mortality of leatherback turtles from fisheries interactions. © Inter-Research 2011.


Blanco G.S.,Drexel University | Morreale S.J.,Cornell University | Velez E.,Kelonian Conservation Society | Piedra R.,Parque Nacional Marino Las Baulas | And 3 more authors.
Journal of Wildlife Management | Year: 2012

Reproductive output is one of the most relevant aspects of life history. We analyzed the reproductive output of the endangered East Pacific green turtle (Chelonia mydas) nesting in Nombre de Jesús, Costa Rica. We supplemented beach patrols with ultrasonography to estimate clutch frequency. With ultrasound scans, we classified the stage of turtle ovaries as: early stage (2 or more clutches), late stage (1 clutch), and depleted ovaries (no clutches). We calculated mean (±SD) estimated clutch frequency (ECF) to be 3.7 ± 1.8 (n = 24) and an adjusted frequency considering individual stage (ECF U; ECF + number of clutches remaining as observed in the last ultrasound) as 5.1 ± 1.3. This is greater than previously described for East Pacific green turtles. Greater individual output could be representative of a healthier population; but could also indicate a decrease in the estimate population numbers previously reported. © 2011 The Wildlife Society.

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