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Marine Turtle Newsletter 55:6, © 1991

Post-Hatchling Turtles Off Northern Australia

Terry A. Walker
Department of Environment and Heritage, P. O. Box 5391, Townsville 4810, Australia

Fifteen islands of the Wellesley Group (16.5°S, 139.5°E) in the Gulf of Carpentaria, northern Australia, were visited briefly in May 1991. Carapaces or skeletal remnants of six juvenile flatback sea turtles were found at white-bellied sea eagle (Haliaeetus leucogaster) feeding stations or nests on four islands as follows: Locust Rock (estimated curved carapace lengths [CCL] of 16.5, 18.5, 20.3 cm), Sweers Island (12.2 cm CCL), Douglas Island (17.4 cm CCL), and an unnamed vegetated sandbank north of Forsyth Island (16.2 cm CCL). These observations indicate that hatchlings and juveniles remain in coastal seas off northern Australia, as they appear to do in the Great Barrier Reef province (Walker 1991) where similar-sized juvenile flatbacks (14-24 cm straight carapace length) have also been found among prey remains at sea eagle island feeding stations (Walker and Parmenter 1990).

The carcass of an uneaten juvenile hawksbill (21 cm CCL) was also beached-washed at Douglas Island. Records of post-hatchling hawksbill turtles are rare, although a few have been caught in fishing nets off northern Australia (Limpus et al. 1991). Juvenile flatback turtles are often caught in these nets, but juvenile green turtles are almost never encountered despite the presence of large nesting colonies at Pisonia and Bountiful Islands in the Wellesley Group (Bustard 1972). The green turtle nesting population in northern Australia is much larger than that of the hawksbill, but there are only two records of post-hatchling green turtles compared with 10 such records for hawksbills (Limpus et al. 1991).

On the basis of these small samples, it is tempting to speculate that hawksbill juveniles are less pelagic than green juveniles and tend to remain in offshore areas (Arafura Sea, Timor Sea, Banda Sea, Gulf of Carpentaria, Gulf of Papua), while northern Australian green turtle juveniles tend to move to the open ocean (Indian Ocean and Coral Sea).

Bustard, H. R. 1972. Sea Turtles: Their Natural History and Conservation. Collins Publ., London. 220 p.

Limpus, C. J., T. A. Walker, and J. West. 1991. Post-hatchling sea turtle specimens and records from the Australian region. In: Proc. Workshop on Marine Turtle Conservation, September 1990. Aust. Natl. Parks Wildl. Serv. (in press).

Walker, T. A. 1991. Juvenile flatback turtles in proximity to coastal nesting islands in the Great Barrier Reef province. J. Herpetol. 25:246-248.

Walker, T. A. and C. J. Parmenter. 1990. Absence of a pelagic phase in the life cycle of the flatback turtle, Natator depressa (Garman). J. Biogeography 17:275-278.