abstract
Leatherback turtles (Dermochelys coriacea) are a federally listed endangered species with a global distribution, classified as critically endangered by the IUCN with the most severe declines observed in the Pacific population.1,2 Major threats to the Pacific leatherback populations are predominately anthropogenic including loss of nesting habitat due to coastal development, over-harvesting of eggs, and incidental bycatch in gill-net and longline fisheries, as well as nest predation and beach erosion.3 Genetic and satellite telemetry studies show that leatherbacks that forage off the coast of California are part of a genetically distinct Western Pacific breeding stock and migrate to nesting beaches on Papua, Indonesia.4-6 While it has been proposed that the rapid decline of the Pacific population is due to increased mortality, little is known about the health of this endangered population.2 To date, health assessment studies in leatherbacks have focused on sampling females on nesting beaches due to relative ease of capturing and sampling these large sea turtles on land.7,8 Such studies represent a sample biased by sex and physiologic state, with limited applicability to the population as a whole. This study represents the first known health assessment of foraging leatherback turtles. Foraging adult leatherbacks (n=18, 6 males, 12 females) were captured by boat along the coast of central California from 2005 to 2007. Blood was collected from the dorsal cervical sinus and/or the popliteal vein and external physical examinations were performed to assess the health of each individual. Physiologic parameters such as temperature, respiratory rate, and heart rate were measured to determine baseline ranges for leatherbacks during capture. Hematology and plasma chemistry panels were performed and levels of heavy metals (Pb, Hg, and Cd) and organochlorine contaminants were assessed. Although organochlorine contaminants are lipophilic and readily concentrate in fat, blood concentrations of organochlorines in two other species of sea turtles correlate well with levels in paired fat samples.9 Blood parameters from Pacific foraging leatherbacks were compared with two populations of Pacific nesting female leatherbacks from Papua New Guinea (n=9) and Costa Rica (n=8) and with nesting females from the Caribbean/ Atlantic population in St. Croix, US Virgin Islands (n=12). Results of this study will serve as baseline health information for foraging Pacific leatherback turtles and provide a foundation for expansion of such health assessments to address the conservation and recovery of this endangered species.
acknowledgements
The authors would like to thank the staff and volunteers involved in boat operations and aerial surveys for leatherback captures in California, especially John Douglas, Scott Hansen, Jim Harvey, Tomo Eguchi, and Erin LaCasella. We would also like to thank the West Indies Marine Animal Research and Conservation Service (WIMARCS), the Virgin Islands Department of Park and Natural Resources, and the US Fish and Wildlife Service for facilitating leatherback blood sampling in St. Croix, US Virgin Islands. This study could not have been completed without support from the Oiled Wildlife Care Network (http://www.owcn.org) and the National Marine Fisheries Service. Field work was carried out under NMFS Endangered Species Research Permit No. 1227.
References
1. US Fish and Wildlife Service. 2008. USFWS Threatened and Endangered Species System (TESS),
2. IUCN (World Conservation Union). 2007. IUCN Red List of Threatened Species 2007, http://www.iucnredlist.org/, downloaded on February 18, 2008.
3. Spotila JR, RD. Reina, AC Steyermark, PT Plotkin, PV Paladino. 2000. Pacific leatherbacks face extinction. Nature 405: 529-530.
4. Dutton PH, Benson SR, Eckert SA. 2006. Identifying origins of leatherback turtles from Pacific foraging grounds off central California, USA. In: Pilcher, N.J. (Comp.).