A turtle's gender is determined by temperature
Like crocodiles and alligators, a turtle's gender is determined after fertilization. If a turtle's eggs incubate below 27.7 degrees Celsius, the hatchlings will be male. But if the eggs incubate above 31 degrees, they will be female. If the temperature is somewhere in-between, or fluctuates, a mix of male and female babies will hatch. As oceans warm, turtles tend to give birth to more females.