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There is considerable debate still regarding the rate of growth of leatherback turtles in the wild, but juvenile leatherback turtles do appear to grow much faster than Chelonid sea turtles (Zug & Parham 1996). The two smallest specimens studied by Zug and Parham (see appendix in Zug & Parnham 1996) closely overlap the size of the two small turtles recovered in Western Australia. The estimated ages of the animals described therein were ca. 0+ to 1 year old.

I noted some voided material adhering to the cloacal area of the turtle when received post-mortem. This material, plus the product of 3x hind-gut flushing using a 50ml syringe via the cloaca was collected and preserved in 70% Ethanol. The material recovered appeared to be remains of pelagic tunicates (Class Thaliacea). Pyrosoma sp. remains have previously been identified among gut contents of a larger sub-adult Western Australian Leatherback turtle specimen (Prince, unpublished data).

The combination of southward flowing warm Leeuwin Current waters and the common intense midwinter westerly storm systems is regularly associated with southward translocation and stranding around southwestern and southern Western Australia of posthatchling sea turtles. Most of these are small loggerheads, but occasionally, other species are also recovered. These strandings are generally sourced from the coastal and offshore island sea turtle nesting beaches of Western Australian (Walker 1994; Prince & Crane unpublished data).

Leatherback turtle specimen WAM R112624 certainly stranded in association with a westerly storm system, and is perhaps a product of an undetected recent leatherback turtle nesting event within the Western Australian region. However, it is more likely that this turtle came from a nesting beach in either the South East Asian region to the north, quite possibly from eastern Indonesia (Spotila et al. 1996), or perhaps Malaysia (Chan & Liew 1996). A South African origin (Hughes 1996) is considered least likely, given that surface drift time across the southern Indian Ocean is typically 18 months, and usual sea surface temperatures found along that route are in the range 10° to 15°C Marine Turtle Newsletter No. 104, 2004 - Page 3 SANCHES, T.M. 1999. Projeto de Conservação Utilização Sustentável da Diversidade Biológica Brasileira. PROBIO – Sub-projeto Biodiversidade da Zona Costeira e Marinha. Área temática: Tartarugas Marinhas. Termo de referência No. 155/98. IBAMA. Programa Nacional de Biodiversidade-Pronábio. WITHERINGTON, B.E. & R.E. MARTIN. 1996. Understanding, assessing, and resolving light-pollution problems on sea turtle nesting beaches. Florida Marine Research Institute Technical Report TR-2. 73 pp. (Alan Pearce, pers. comm.). Genetic sample material to help address this question has been retained. Whatever the origin, R112624 can be expected to have been chilled on entering a neighbouring cooler water mass somewhere off the southwestern Western Australian coast, which thus rendered it more vulnerable to passive displacement by surface drift. The Leeuwin Current flow state ca. 1 week before the stranding is indicated by the processed satellite image N16/9363 of 17 July 2002 (Figure 1). The main current warm water mass (ca. 22oC, in lightest shade) straddling Marine Turtle Newsletter No. 104, 2004 - Page 4 the 200m isobath is shown extending outhward of Perth, with numerous tongues of relatively warm water pushing shoreward across the shelf from the eastern current edge. A current eddy of > 21oC located northwestward of the Shoalwater Bay beach stranding site is also shown with ‘fingers’ of cooler water closer inshore. The regional sea state and water temperatures indicated by the Figure 1 imagery is consistent with observations of marine science colleagues engaged in simultaneous independent field-work. There can be little doubt that our specimen was entrained for some extended time in a water mass cooler than the 26oC suggested by Eckert (2002) as typical of locations for much larger juvenile leatherback turtles as it travelled down the Western Australian coast towards the Perth region. From that point on, it was apparently swept along in the storm driven surface drift into even cooler coastal waters until it stranded near death along with a wrack of dislodged macroalgae and seagrass at the point of discovery.

Acknowledgments: Rebecca Carter, who received the moribund turtle from unnamed beachcombers early AM, and correctly identified it as a leatherback, advised Deanne Pember (CALM Fremantle) of the stranding. Marine Ranger Chris Mather organised retrieval of the turtle from Shoalwater Bay, and delivery to the AQWA, Hillarys Harbour facility, as arranged by John Edwards. Gloria Jackson (AQWA) arranged veterinary consultation. Documentation detail for the find was provided by Chris Mather and Deanne Pember. I thank Mick Byrne, Rob McCauley, Micheline-Nicole Jenner, and Chris Mather for sharing their independent observations on regional sea temperatures and currents. I thank Alan Pearce for his comments on the sea currents and water temperatures relevant to this case, and for use of his Leeuwin Current imagery.