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Flatback Turtles Facing the Heat of Projected Climate Change

Paper Reviewed
Howard, R., Bell, I. and Pike, D.A. 2015. Tropical flatback turtle (Natator depressus) embryos are resilient to the heat of climate change. Journal of Experimental Biology 218: 3330-3335.

Howard et al. (2015) introduce their recent study of tropical turtles by writing that "climate change is threatening reproduction of many ectotherms by increasing nest temperatures, potentially making it more difficult for females to locate nest sites that provide suitable incubation regimes during embryonic development," with the end result that "elevated nest temperatures could increase the incidence of embryonic mortality and/or maladaptive phenotypes."

In light of these negative possibilities, the three Australian researchers "investigated whether elevated nest temperatures reduce hatching success in tropical flatback turtles (Nator depressus) nesting in the Gulf of Carpentaria, Australia." This they did by recording onsite temperature measurements of turtle nests and conducting laboratory studies of the effects of egg incubation treatments that began at 29.5°C and progressively increased throughout incubation up to maxima of 31, 32, 33, 34 and 35°C. And what did they thereby learn?

Howard et al. determined that (1) flatback embryos "can survive mean temperatures almost 4°C above reported natural nest temperatures with little negative impact," that (2) "early in development, embryos can survive temperatures averaging more than 36° for 48 hours and ranging up to 39°C (briefly)," and that (3) "high-temperature incubation did not significantly influence hatchling body size." In addition, they note that in flatback turtles that nest in sites in close proximity to those of the turtles they studied, and which mainly produce male hatchlings, it can be anticipated that (4) "climate change may push the sex ratio towards parity," which they describe as an additional "encouraging finding."

Posted 29 February 2016