MTN 114:14-15 Hawksbill Turtle Tracking as Part of Initial Sea Turtle Research and Conservation at Groote Eylandt, Northern Australia

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Hawksbill Turtle Tracking as Part of Initial Sea Turtle Research and Conservation at Groote Eylandt, Northern Australia

Scott D. Whiting¹, Simon Hartley², Simeon Lalara², Damian White¹, Tony Bara², Christopher Maminyamunja² & Laban Wurramarrba²
¹ WWF-Australia PO Box 1268, Darwin, NT, 0801 (E-mail: s_whiting@biomarine.com)
² Sea Ranger Unit, Anindilyakwa Land Council PO Box 172 Alyangula NT 0885

Limited sea turtle research has been conducted in the Gulf of Carpentaria in northern Australia because of its remoteness and inaccessibility. Groote Eylandt lies in the north east of the Gulf of Carpentaria and is a large continental island (area of over 2260 km²) with many smaller associated islands, all of which are Aboriginal owned. The population of 2500 resides in two main Aboriginal communities and in one urban centre associated with mining operations. Green, hawksbill, flatback and olive ridley turtles nest on the main and associated islands (Chatto 1998) and green and hawksbill turtles are resident in the local waters. In 2001 the Anindilyakwa Land Council established an Aboriginal Sea Ranger Unit to manage marine species and their habitats. Sea turtle management was a priority and as part of initial sea turtle research, satellite transmitters were attached to two post-nesting hawksbill turtles. The objectives of the tracking study were to; 1) identify migration paths of two turtles; 2) increase awareness of sea turtle biology and conservation among all residents on Groote Eylandt and 3) increase enthusiasm for management.

Satellite transmitters (PTTs) (KiwiSat 101 – Sirtrack Pty Ltd) were attached using epoxy (Mitchell 1998) to the carapace of two hawksbill turtles immediately after oviposition on North East Island, 12 km NE of Groote Eylandt on 2 August 2005. The turtles were named Numarngainyamba (meaning Cheeky) and Numinuwurrariyaamakilya (meaning Bad Skin) in the local Anindilyakwa language by the Traditional Owners and Sea Rangers. The Argos data were analysed using STAT (Coyne & Godley 2005).

Numinuwurrariyaamakilya remained in the vicinity of the nesting beach for 43 weeks. Her transmitter produced poor results; transmitting for 5 weeks, remaining dormant for 26 weeks and transmitting intermittently for a further 12 weeks. However, the results were sufficient to indicate no long distance migration.

Numarngainyamba made a straight-line post-nesting migration of 600 km (Fig. 1). She remained in the vicinity of the nesting beach for 89 days and laid a further five clutches of eggs (based on renesting intervals of 14.2 days, Dobbs et al. 1999). Numarngainyamba then moved directly to the mainland of Australia and followed the coastline northward until she reached a rocky reef area near Maningrida 21 days later. She remained at this location for seven weeks before transmissions ceased. Although this transmitter produced only a small percentage (8%) of good quality (Class 3, 2, 1 – Argos 1996) results, her migration path was easily identified.

Figure 1. Post-nesting migration route of Numarngainyamba from North East Island, northern Australia in 2005. Map created using Maptool (SEATURTLE.ORG Maptool 2002).

This study was the first to track post-nesting hawksbill turtles in Australia and identified the first migration route for an Australian nesting hawksbill outside the rookeries on the east coast of Queensland. This tracking project proved very successful in raising awareness of sea turtle biology and management in the Aboriginal communities on Groote Eylandt through the public interface of STAT (Coyne & Godley 2005). By mapping movements which intersected the hunting grounds of many Traditional Owners, Numarngainyamba’s migration clearly demonstrated in a non-technical fashion why sea turtle conservation needs the cooperation of many communities and stakeholders. The rangers have included this message in numerous community talks, presentations to government and local schools, and informally throughout their own communities.

Further, the degree of interest in this project has provided the impetus for the establishment of track, nest and harvest surveys at key rookeries within the Groote archipelago. If maintained, the value of this long-term data, in one of Australia remotest areas, will be a significant, desirable and an unexpected outcome of this tracking study.

Acknowledgements: Funding was provided for this project by the Lisette Lewis Foundation. Satellite transmitters were provided by WWF-Australia. Boats and equipment were provided by the Anindilyakwa Land Council. Fieldwork assistance was provided by Alec Wurramara and Phillip Mamarika.

ARGOS. 1996. Location and data collection satellite system user’s guide. Service Argos, Toulouse, France.

CHATTO, R. 1998. A preliminary overview of the locations of marine turtle nesting in the Northern Territory. In: R. Kennett, A. Webb, M. Guinea & G. Hill (Eds). Marine Turtle Conservation and Management in Northern Australia, Northern Territory Univ., Darwin. pp. 33-40.

COYNE M.S. & B.J. GODLEY. 2005. Satellite Tracking and Analysis Tool (STAT): An integrated system for archiving, analyzing and mapping animal tracking data. Marine Ecology Progress Series 301: 1-7.

DOBBS, K.A., J.D. MILLER, C.J. LIMPUS & A.M. LANDRY, Jr. 1999. Hawksbill turtle, Eretmochelys imbricata, nesting at Milman Island, northern Great Barrier Reef, Australia. Chelonian Conservation & Biology 3: 344-362.

MITCHELL, S.V. 1998. Use of epoxy in telemeter attachment. In: F.A. Abreu-Grobois, R. Briseno-Duenas, R. Marquez & L. Sarti (Compilers). Proceedings of the Eighteenth International Sea Turtle Symposium. U.S. Dept. of Commerce. NOAA Technical Memorandum NMFS-SEFSC-436. pp 254-255.

SEATURTLE.ORG Maptool. 2002. SEATURTLE.ORG, Inc. <https://seaturtle.org/maptool/> (downloaded 20 May 2006).