Persistent leatherback turtle migrations present opportunities for conservation.

Effective transboundary conservation of highly migratory marine animals requires international management cooperation as well as clear scientific information about habitat use by these species. Populations of leatherback turtles (Dermochelys coriacea) in the eastern Pacific have declined by >90% during the past two decades, primarily due to unsustainable egg harvest and fisheries bycatch mortality. While research and conservation efforts on nesting beaches are ongoing, relatively little is known about this population of leatherbacks' oceanic habitat use and migration pathways. We present the largest multi-year (2004-2005, 2005-2006, and 2007) satellite tracking dataset (12,095 cumulative satellite tracking days) collected for leatherback turtles. Forty-six females were electronically tagged during three field seasons at Playa Grande, Costa Rica, the largest extant nesting colony in the eastern Pacific. After completing nesting, the turtles headed southward, traversing the dynamic equatorial currents with rapid, directed movements. In contrast to the highly varied dispersal patterns seen in many other sea turtle populations, leatherbacks from Playa Grande traveled within a persistent migration corridor from Costa Rica, past the equator, and into the South Pacific Gyre, a vast, low-energy, low-productivity region. We describe the predictable effects of ocean currents on a leatherback migration corridor and characterize long-distance movements by the turtles in the eastern South Pacific. These data from high seas habitats will also elucidate potential areas for mitigating fisheries bycatch interactions. These findings directly inform existing multinational conservation frameworks and provide immediate regions in the migration corridor where conservation can be implemented. We identify high seas locations for focusing future conservation efforts within the leatherback dispersal zone in the South Pacific Gyre.

Bioenergetics and diving activity of internesting leatherback turtles Dermochelys coriacea at Parque Nacional Marino Las Baulas, Costa Rica.

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) < or =24 degrees C (9.5+/-5.7%) increased with increasing mean maximum dive depths (22.6+/-7.1 m; all P< or =0.001). The FMRs increased with longer mean dive durations, bottom times and surface intervals and increased time spent in Tw< or =24 degrees C (all r2> or =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.

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 PO(2) and temperature during incubation to determine the extent to which they affected the developmental environment of leatherback embryos. Minimum PO(2) 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 PO(2) nor temperature was correlated with hatching success. Our measurements of relatively high nest PO(2) (lowest 17.1 kPa or 16.9% O(2)) 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.