Factors affecting hatch success of hawksbill sea turtles on long island, Antigua, West Indies

Mark Allan Ditmer, Seth Patrick Stapleton

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

Current understanding of the factors influencing hawksbill sea turtle (Eretmochelys imbricata) hatch success is disparate and based on relatively short-term studies or limited sample sizes. Because global populations of hawksbills are heavily depleted, evaluating the parameters that impact hatch success is important to their conservation and recovery. Here, we use data collected by the Jumby Bay Hawksbill Project (JBHP) to investigate hatch success. The JBHP implements saturation tagging protocols to study a hawksbill rookery in Antigua, West Indies. Habitat data, which reflect the varied nesting beaches, are collected at egg deposition, and nest contents are exhumed and categorized post-emergence. We analyzed hatch success using mixed-model analyses with explanatory and predictive datasets. We incorporated a random effect for turtle identity and evaluated environmental, temporal and individual-based reproductive variables. Hatch success averaged 78.6% (SD: 21.2%) during the study period. Highly supported models included multiple covariates, including distance to vegetation, deposition date, individual intra-seasonal nest number, clutch size, organic content, and sand grain size. Nests located in open sand were predicted to produce 10.4 more viable hatchlings per clutch than nests located >1.5 m into vegetation. For an individual first nesting in early July, the fourth nest of the season yielded 13.2 more viable hatchlings than the initial clutch. Generalized beach section and inter-annual variation were also supported in our explanatory dataset, suggesting that gaps remain in our understanding of hatch success. Our findings illustrate that evaluating hatch success is a complex process, involving multiple environmental and individual variables. Although distance to vegetation and hatch success were inversely related, vegetation is an important component of hawksbill nesting habitat, and a more complete assessment of the impacts of specific vegetation types on hatch success and hatchling sex ratios is needed. Future research should explore the roles of sand structure, nest moisture, and local weather conditions.

Original languageEnglish (US)
Article numbere38472
JournalPloS one
Volume7
Issue number7
DOIs
StatePublished - Jul 3 2012
Externally publishedYes

Bibliographical note

Funding Information:
The Jumby Bay Hawksbill Project is generously supported by the Jumby Bay Island Company. We are indebted to the tireless efforts of JBHP field teams, who have spent countless hours patrolling Jumby Bay’s beaches over the past few decades. We are grateful for the enduring support of the island’s residents, the Jumby Bay Resort, its staff and guests, and the Fuller family and other individuals on Antigua who have made the field teams feel at home. C. Guy, J. Jungers, J. Richardson and S. Thompson provided helpful comments on earlier drafts that greatly improved the manuscript. We would also like to thank faculty and peers at the University of Minnesota’s Conservation Biology Graduate Program. The JBHP is a member of the Wider Caribbean Sea Turtle Conservation Network.

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