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Mating loggerhead turtles at the Gnaraloo Bay Rookery in Western Australia

Sand temperature data logger deployment

After completing our daily track survey and unexpectedly coming across two mating loggerhead sea turtles (Caretta caretta) near the water’s edge, the Turtle Team undertook the task of burying temperature data loggers in the sand throughout the Gnaraloo Bay Rookery (GBR) – a new project led by GTCP1516 Program Assistant, Dr. Jordy Thomson.

Sand temperature has a large effect on sea turtle development and hatching success, with cooler average nest temperatures producing more males, warmer temperatures producing more females, and mortality potentially occurring within the nest if temperatures exceed 33°C for extended periods. The temperature data we collect this season will be used to assess the vulnerability of the GBR to future climate change in addition to giving us more information on factors influencing hatching success within the southeast Indian Ocean loggerhead turtle population in the shorter term.

We determined areas of peak turtle nesting density based on data from previous seasons and, after selecting our sample locations, we were ready for deployment. The locations were based on typical nesting sites between the high tide mark and the dunes and at range of average loggerhead sea turtle nest depths. Once we dug out the top layer of soft sand, we used a PVC pipe to take a sediment core at depth, allowing us to maintain the natural layering of the sand with minimal disturbance. The data logger was then lowered into the hole created by the core and buried with the sand still in the core.

These data loggers are already recording. By the end of nesting season, we will have temperature profiles that are representative of the highest-density nesting areas throughout the GBR!

Kimberly Nielsen (Data QA/QC Intern)

Sand temperature data logger
Jordy and Alistair removing the core and readying a sand temperature data logger
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