Publications

Diet and foraging niche flexibility in green and hawksbill turtles

This study investigates the diet and foraging niche flexibility of green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles in a foraging habitat along the North Pacific coast of Costa Rica. Using stable isotope analysis of carbon (δ13C) and nitrogen (δ15N) in turtle blood and skin samples, we explored dietary patterns, trophic niche overlap, and potential ecological roles of these species.

Key Findings

1. Dietary Composition and Trophic Levels:

   • Black morphotype green turtles exhibited a mixed diet, including fish (34.8%) and macroalgae (51.8%), indicating foraging across multiple trophic levels.

   • Yellow morphotype green turtles and hawksbill turtles primarily consumed macroalgae (~85%), showing dietary specialization.

2. Niche Differentiation:

   • Significant overlap was observed between the isotopic niches of yellow morphotype green turtles and hawksbill turtles, while black morphotype green turtles had distinct niches.

   • Seasonal shifts were noted in the black morphotype’s diet, which varied between omnivory and herbivory depending on upwelling conditions.

3. Ecological Implications:

   • The study underscores the importance of niche partitioning in reducing competition and supporting biodiversity in these sympatric species.

   • Foraging activities of these turtles may contribute to ecosystem health, such as maintaining seagrass and reef resilience through grazing.

4. Management Recommendations:

   • Highlighted the need for habitat conservation efforts, as these bays serve as critical feeding grounds for endangered and critically endangered turtle populations.

Lipid profiling suggests species specificity and minimal seasonal variation in Pacific Green and Hawksbill Turtle plasma

This study investigated lipid profiles in green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles to understand how environmental factors influence their physiology. Using plasma samples collected from turtles in North Pacific Costa Rica, we identified 623 lipid molecules across 10 lipid classes and one metabolite group.

Key Findings

1. Species-Specific Lipid Profiles

   • Significant differences in lipid composition were found between green and hawksbill turtles, suggesting that species-specific physiological and dietary factors influence lipid profiles.

2. Minimal Seasonal Variation

   • Most lipids showed consistent levels across seasons, although a few structural lipids exhibited changes between upwelling (colder) and non-upwelling (warmer) periods, indicating potential adaptive mechanisms to environmental changes.

3. Environmental Adaptations

   • Differences in lipid saturation and chain length in some classes suggest that turtles may use homeoviscous adaptation to maintain cell membrane function in varying water temperatures.

4. Implications for Conservation

   • Lipid profiling can serve as a tool for monitoring health, diet, and stress in endangered sea turtles, contributing to more tailored conservation efforts.

Conclusion

The study provides a framework for using lipidomics to explore the physiological responses of sea turtles to dynamic ocean environments. It highlights the value of lipid profiling in assessing health and guiding conservation strategies​.

Pacific Sailfish (Istiophorus platypterus) in the Eastern Pacific Ocean

This study examines the movement ecology and habitat use of Pacific sailfish off the coast of Costa Rica, focusing on their association with ocean currents and seasonal upwelling. By deploying satellite transmitters on sailfish, we tracked their migration patterns and environmental interactions.

Key Findings

1. Movement and Habitat Use:

   • Sailfish traveled across six Exclusive Economic Zones (EEZs) and international waters.

   • Displacement distances ranged from 340 to 986 km, showing variable migration patterns.

2. Seasonal and Environmental Adaptations:

   • Sailfish maintained stable thermal environments despite upwelling-driven temperature changes (~2°C variability).

   • Behavioral shifts, such as varying dive depths (48m during upwelling vs. 37m in non-upwelling seasons), were observed but not fully explained by environmental data alone.

3. Ocean Currents and Energy Conservation:

   • Movements alternated between with-current and against-current directions, potentially optimizing energy expenditure.

4. Conservation Implications:

   • The findings highlight the need for multinational cooperation to protect sailfish habitats.

   • Costa Rica lags behind neighboring countries in implementing protections like banning commercial sailfish sales.

Conclusion

Sailfish exhibit resilience to environmental changes, but further research is necessary to understand fine-scale interactions between their behavior and oceanographic features. Strengthening conservation measures is critical to ensure the long-term viability of sailfish populations​.

VivLocal variation in the Internesting behavior of green turtles in the Gulf of Papagayo, Costa Rica

This study investigates the internesting behavior of East Pacific green turtles (Chelonia mydas) from two nesting beaches in the Gulf of Papagayo, Costa Rica: Nombre de Jesús and Playa Cabuyal. Using satellite telemetry, the researchers tracked 21 turtles to explore their movement, dive behavior, and habitat use during the internesting period.

Key Findings

1. Site-Specific Differences in Behavior:

   • Turtles from Cabuyal traveled greater distances and used larger areas (average 606.5 km²) compared to turtles from Nombre de Jesús (average 16 km²).

   • Cabuyal turtles also engaged in deeper dives (mean depth: 10 m) and longer dive durations (average: 18.75 minutes) than Nombre de Jesús turtles (mean depth: 6.5 m; average duration: 6.68 minutes).

2. Habitat Use and Energy Conservation:

   • Turtles from Nombre de Jesús remained closer to the nesting beach, possibly to conserve energy due to limited offshore resting habitats.

   • Cabuyal offered more varied and deeper habitats, allowing turtles to rest at different depths.

3. Influence of Environmental Factors:

   • Seasonal and oceanographic conditions, such as upwelling and El Niño events, may influence nesting behaviors and dive patterns.

   • Internesting periods were longer (up to 21 days) later in the nesting season when water temperatures were cooler.

4. Conservation Implications:

   • The study highlights the need for site-specific conservation strategies to account for differences in habitat use and behavior, even between nearby nesting beaches.

   • Protecting critical internesting habitats is essential to ensure the long-term survival of East Pacific green turtle populations.

Conclusion

Green turtles exhibit significant behavioral differences based on local environmental conditions, emphasizing the importance of tailored conservation efforts. These findings contribute to a better understanding of the ecological needs of green turtles during the reproductive season​.