Thursday, January 11, 2018

Climate change turning green sea turtles all female

What a strange evolutionary development! It seems that the sex of baby green sea turtles is dependent on the temperature of the sand in which eggs incubate.
For some evolutionary reason that remains unclear (to me at least), the sex of baby turtles - as well as alligators and crocodiles - is not yet determined when an egg is laid. Within a very narrow and specific temperature range, the eggs will produce a clutch of roughly 50% male and 50% female baby turtles. However, if the temperature of the sand is just a few degrees cooler, the clutch will turn out 100% male; a few degrees warmer, and the eggs turn out 100% female.
So, you can imagine that the hotter temperatures created by climate change could wreak havoc with the gender profile of baby turtles. And that is exactly what is being found among the green sea turtles of Australia: 99.8% of green sea turtles born recently along the northern part of the Great Barrier Reef are female. Along the cooler southern part of the Reef, the population is also skewed female, although not in such an extreme manner, around 65%-69%. There has also been a much higher incidence of mortality in the developing eggs, a phenomenon also found in other sea turtle populations, such as those in Florida, where the heat is effectively cooking the eggs and killing the babies.
Between them, these two effects of climate change puts the viability of the whole population of sea turtles, which is already seriously impacted by habitat loss and the effects of unbridled tourism, in jeopardy.

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