For marine turtles, the temperature at which eggs are incubated determines the sex of the offspring. Cooler incubation temperatures lead to male offspring, while warmer temperatures result in female turtles. This means that a planet warmed by climate change will lead to an imbalance among turtles—and researchers have already noticed that a disproportionate number of turtle offspring are female.
With fewer males in the population, birth rates among turtles could decline as rates of inbreeding increase.
Turtles in warmer climates, however, have managed to survive the surge in females. Researchers in Northern Cyprus observed that during one mating season a total of 28 males mated with 20 breeding females. Not only did every female mate with an average of 1.4 males, but genetic tests showed that no two clutches of eggs came from the same male.
Moreover, researchers noted that males travel across a great range during mating seasons, suggesting that they may be active in multiple breeding groups each year.
"There is great concern that a lack of males could lead to inbreeding in small populations of marine turtles, potentially causing a population crash," explained Lucy Wright, a PhD candidate at the University of Exeter who led the study, "however our research suggests that there are more males out there than expected considering the female-biased hatchling sex ratios and that their mating patterns will buffer the population against any potential feminising effects of climate change."