A comparison of two techniques used to model sand temperatures and sex ratios at loggerhead turtle (Caretta caretta) rookeries in Western Australia

Lorian Woolgar

    Research output: ThesisMaster's Thesis

    295 Downloads (Pure)

    Abstract

    All marine turtles have temperature-dependent sex determination, and there is wide-spread concern that climate change could increase nest temperatures, leading to pronounced female biases at many of the current rookeries. This study contrasted the outcomes of correlative and mechanistic modelling approaches which predict sand temperatures and subsequent sex ratios of species with temperature-dependent sex determination. Of particular interest were the alignment of results and the ease of use of each modelling approach. Inputs for the models included nest temperature data from three key loggerhead (Caretta caretta) rookeries in Western Australia (WA) and data required to build the model, including; daily air temperatures, monthly sea surface temperatures, high resolution climate data, and information on the physical properties of beach sand. Monthly nest temperatures at each location were reconstructed over a 20 year period (Jan 1990 – Mar 2009), and also projected (2030, 2070) under 'conservative' and 'extreme' IPCC climate change emissions scenarios. Subsequent sex ratios were then estimated with reference to the temperature-dependent sex determination (TSD) parameters of C. caretta from WA. The correlative models estimated much warmer sand temperatures at 50 cm nest depth, and a greater feminisation at each rookery under IPCC projections. The mechanistic model required additional levels of complexity with respect to data input, but was capable of producing temporally explicit predictions across the range of nest depths that C. caretta embryos develop. Both models predicted that rookery temperatures were not correlated with latitude, with the coolest rookery at Gnaraloo Bay located at an intermediate latitude between the southernmost rookery on Dirk Hartog Island and a northern rookery in cape range national park.
    Original languageEnglish
    QualificationMasters
    Publication statusUnpublished - 2012

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