It’s temperature that determines the sex of a baby sea turtle. For mammals like us, sex is determined during fertilization, by the sex chromosomes inside cells. But for sea turtles it’s the temperature at which the egg develops on beaches that determines the sex: this is called temperature dependent sex determination or TSD.
“Research shows that if a turtle's eggs incubate in sand below 27.7° Celsius (81.86° Fahrenheit), the turtle hatchlings will be male. If the eggs incubate above 31° C (88.8° F), however, the hatchlings will be female.”
With climate change the temperature on beaches in many places is warmer. What does this mean for the sex ratio of turtles in a population? Researchers have found that the warmer the sand, the higher the ratio of female turtles, reaching nearly 99% female in some places, including the Great Barrier Reef and Florida’s east coast. Not having enough males means fewer mating opportunities, threatening the population’s ability to survive.
Preventing an “All Girl” Generation
Some Sea turtles seem to be adapting to the rising temperatures. Since the 1990s green sea turtles have been laying their first nests at a beach in Cyprus almost one day earlier each year.
Nest monitoring for temperature can help local scientists understand what’s happening to sea turtle nests. Shading of nests that are too warm can make a difference in the sex ratio of hatchlings without disturbing nests. Conservationists have tried more extreme measures like nest relocation and artificial hatcheries in some places. Preventing further warming by fighting climate change at all levels is the ultimate solution for sea turtles.
