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Health and hatching success of Western Australian loggerhead turtle (Caretta caretta) nesting populations

Trocini, S., Warren, K., O'Hara, M., Bradley, S. and Robertson, I. (2008) Health and hatching success of Western Australian loggerhead turtle (Caretta caretta) nesting populations. Ningaloo Research Progress Report: Discovering Ningaloo – latest findings and their implications for management. Ningaloo Research Coordinating Committee. Department of Environment and Conservation, W.A..

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    Abstract

    Most of the existing sea turtle populations worldwide are in decline. In particular, loggerhead turtles (Caretta caretta) are listed as endangered and loggerhead nesting populations in Eastern Australia declined by 86% since the 1970s.

    This study aims to collect critical baseline data regarding health and hatching success of the loggerhead turtle nesting population in Cape Range National Park. Adult nesting turtles were examined and a blood sample taken to establish reference ranges of several blood health parameters and screen for toxin levels. The marked nests were excavated after observed hatchling emergence to establish hatching and emergence success, and collect samples of dead hatchlings and embryos for further histological examination, as well as unhatched eggs for toxin screening. Additionally, all nests were monitored for signs of predation.

    The research was conducted for two nesting seasons (2006/07 and 2007/08) and initial results show that in Cape Range National Park nest predation is a crucial limiting factor affecting hatching success. Predation by ghost crabs (Ocypode spp), monitor lizards (Varanus giganteus) and feral European red foxes (Vulpes vulpes), considerably reduce survivorship from egg to hatchling. In fact, in the first and second years of this study 78.2% and 83.3% of the monitored nests respectively, showed signs of partial or complete nest predation. It is unlikely that this mainland nesting population can sustain such severe level of predation pressure, especially in conjunction with other anthropogenic causes of decline at foraging sites and during migration to the nesting site (i.e. poaching, fisheries by-catch and pollution), and more studies are recommended to identify successful management strategies to reduce nest predation on this beach.

    This study takes an important first step towards obtaining crucial information on loggerhead turtle nest ecology and nesting turtle health in this region.

    Publication Type: Report
    Murdoch Affiliation: School of Veterinary and Biomedical Sciences
    Series Name: Ningaloo Research Program Progress Report
    Publisher: Ningaloo Research Progress Report: Discovering Ningaloo – latest findings and their implications for management. Ningaloo Research Coordinating Committee. Department of Environment and Conservation
    URI: http://researchrepository.murdoch.edu.au/id/eprint/3758
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