Technical Report #178. Seitz, W.A., K.M. Kagimoto, B. Luehrs and L. Katahira. 2012. Twenty years of conservation and research findings of the Hawai‘i Island Hawksbill Turtle Recovery Project, 1989 - 2009

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ABSTRACT:
Prior to 1989, available information on nesting hawksbill turtles (Eretmochelys imbricata) in the Hawaiian Islands was minimal. From 1987 to 1990, personnel from Hawai‘i Volcanoes National Park conducted reconnaissance along the southern coastline of Hawai‘i Island to confirm evidence of nesting activity, identify hawksbill nesting beaches, and evaluate threats. Thereafter, the Hawai‘i Island Hawksbill Turtle Recovery Project (HIHTRP) was established to monitor and manage nesting sites, document nesting events, collect baseline data, ensure hatchlings safely reach the ocean, and mitigate threats. Between 1993 and 2009, the number of beaches monitored for nesting activity expanded from eight to 17, with variable coverage at each site. Flipper tagging of nesting adult females has occurred since 1991. Primary findings from twenty years of data collection include: 1) The southern coast of Hawai‘i Island has the highest documented hawksbill nesting activity in the Main Hawaiian Islands; 2) Nesting season (egg laying to hatchling emergence) begins in April and extends to February with a peak egg laying period from late-July to mid-September; 3) The mean seasonal cohort observed was 11.6 ± 1.2 (n= 18) with a range of 3 to 18 turtles; 4) The mean number of nests per turtle was 3.3 ± 0.2 per season (n= 20) with a range of 1 to 6 nests; 5) The mean remigration interval was 3.5 ± 0.1 years (n= 106) with a range of 2 to 10 years; 6) Nesting turtles demonstrated a high degree of nesting site fidelity, with 87% of individuals documented using only one nesting site. Forty-eight of these individuals were documented at the same beach in multiple years. Thirteen percent of nesting females were documented at multiple sites; 7) The mean nest to next crawl inter-nesting interval was 18.6 ± 0.1 days (n= 276) (range 13 to 24 days), while the mean nest to nest inter-nesting
interval was 20 ± 0.2 days (n= 277) (range 13 to 30 days); 8) The mean incubation period was 62.5 ± 0.4 days (n= 446) with a range of 50 to 101 days; 9) The mean clutch size was 175.2 ± 1.5 eggs (n= 631) with a range of 78 to 274 eggs; 10) The mean nest hatch success of eggs was 71.9 ± 1.0% (n= 640) with a range of 0 to 100%; 11) Between 1991 and 2009, 100 adult females were tagged, with a mean of 5.3 ± 0.7 (n=19) and range of 1 to 11 per season; 12) Between 1988 and 2009 a total of 742 nests (most occurring at Kamehame, ‘Āpua Point, and Pōhue Bay) were documented with a mean of 35 ± 4.0 (n= 21) and range of 8 to 69 per season; 13) Between 1989 and 2009, over 80,775 hatchlings are estimated to have entered the Pacific Ocean from Hawai‘i Island; 14) Primary threats to nest and hatchling success all of which have been significantly addressed were non-native mammalian predators, alien plants, artificial lights, hatchling stranding, vehicular traffic, and incompatible recreational use of nesting beaches; 15) Volcanism including land subsidence remains as an uncontrollable factor.

Title pages, table of contents

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Abstract and introduction

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Methods

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Results

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Discussion

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Acknowledgements and literature cited

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Appendix A. Site Descriptions and Results Summaries for Individual Nesting Beaches

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Appendix B. Detailed Data Summaries for Tagged Adult Females and Nesting Activity

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Appendix C. Satellite Tracking Maps of Hawaiian Hawksbills from Nesting Beach to Foraging Grounds

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