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RESEARCH ARTICLE

Nesting ecology of hawksbill turtles at a rookery of international significance in Australia’s Northern Territory

Xavier Hoenner A B H , Scott D. Whiting C D , Gavin Enever E , Keith Lambert E , Mark A. Hindell F and Clive R. McMahon A F G
+ Author Affiliations
- Author Affiliations

A Research Institute for Environment and Livelihoods, Institute of Advanced Studies, Charles Darwin University, Darwin NT 0909, Australia.

B Integrated Marine Observing System (IMOS), University of Tasmania, Private Bag 110, Hobart, Tas. 7001, Australia.

C Marine Biodiversity Group, Department of Natural Resources, Environment, the Arts and Sport, Northern Territory, Darwin NT 0909, Australia.

D Marine Science Program, Department of Environment and Conservation, Kensington, WA, Australia.

E Anindilyakwa Land Council, 30 Bougainvillea Drive, Alyangula NT PO Box 172, Alyangula NT 0885, Australia.

F Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas. 7001, Australia.

G Sydney Institute of Marine Science, 19 Chowder Bay Road, Mosman NSW, 2088, Australia.

H Corresponding author. Email: xavier.hoenner@utas.edu.au

Wildlife Research 43(6) 461-473 https://doi.org/10.1071/WR16047
Submitted: 17 May 2016  Accepted: 10 August 2016   Published: 26 September 2016

Abstract

Context: Following centuries of intense human exploitation, the global stocks of hawksbill turtle have decreased precipitously and the species is currently considered Critically Endangered by the IUCN. Australia supports the largest breeding aggregations worldwide; however, there are no accurate estimates of population abundance and seasonality for hawksbill turtles at important nesting grounds in eastern Arnhem Land.

Aims: This study was designed to fill in this lack of ecological information and assist with the conservation and management of hawksbill turtles. More specifically, our overarching goals were to assess nesting seasonality, habitat preferences and provide the first estimate of annual nesting population size at a Northern Territory rookery.

Methods: In 2009 and 2010 we collected beach monitoring, satellite telemetry and sand temperature data over two nesting seasons at a group of three islands located 30 km off Groote Eylandt in the Gulf of Carpentaria, northern Australia. We subsequently analysed these data to unravel hawksbill nesting behaviour and reproductive outputs, and examined the vulnerability of this rookery to climate change.

Key results: Hawksbill turtle nesting seasonality consistently started in mid-May, peaked in mid-August and ended in late November. Annual nesting abundance showed a near 3-fold increase between 2009 and 2010, with an average of 220 and 580 hawksbill females nesting on this island group respectively. Sand temperature at 50 cm reached more than 30°C at all monitored sites during most of the peak of the incubation period.

Conclusions: This remote and untouched group of islands constitutes a major hawksbill turtle rookery both nationally and globally. While anthropogenic impacts and predation are low year round, climate change threatens to skew hatchling sex ratios, eventually leading to an increase in hatchling mortality.

Implications: Additional ground-based surveys are required to refine the accuracy of population estimates presented in this study. Given the paucity of data in the region, we recommend this island group off Groote Eylandt be used as a population-monitoring index site for the eastern Arnhem Land hawksbill turtle breeding aggregation.

Additional keywords: biologging, Eretmochelys imbricata, Groote Eylandt, nesting, Northern Territory, reproductive behaviour, seasonality.


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