Climate change is threatening the future of sea turtles. Whereas the gender of most animals is determined at fertilization, the sex of most turtles, as well as alligators, and crocodiles is determined by the temperature of the developing eggs. The hotter the sand where the eggs are buried, the more female turtles are hatched. Recent heat waves have caused the sand on some beaches in Florida to get so hot that nearly every turtle born was female.

Reuters quotes Bette Zirkelbach, manager of the Turtle Hospital in Marathon in the Florida Keys, saying, “The frightening thing is the last four summers in Florida have been the hottest summers on record.”

“Scientists that are studying sea turtle hatchlings and eggs have found no boy sea turtles, so only female sea turtles for the past four years,” Zirkelbach said, whose turtle center has operated since 1986.

When a female turtle digs a nest on a beach, the temperature of the sand determines the gender of the hatchlings. Zirkelbach said an Australian study showed similar statistics – “99% of new sea turtle babies are female.”

Research shows that if a turtle’s eggs incubate below 27.7° Celsius (81.86° Fahrenheit), the turtle hatchlings will be male. If the eggs incubate above 31° Celsius (88.8° Fahrenheit), however, the hatchlings will be female. Temperatures that fluctuate between the two extremes will produce a mix of male and female baby turtles according to NOAA’s National Ocean Service.

“Over the years, you’re going to see a sharp decline in their population because we just don’t have the genetic diversity,” said Melissa Rosales Rodriguez, a sea turtle keeper at the recently opened a turtle hospital at the Miami Zoo. “We don’t have the male-to-female ratio needed in order to be able to have successful breeding sessions.”

The two turtle hospitals are also battling tumors in turtles known as fibropapillomatosis, also known as FP. These tumors are contagious to other turtles and can cause death if not treated.

With climate affecting the future of turtles and the disease being so widespread, Zirkelbach sees the need to save every turtle she can and open more rehab centers.

Thanks to Alaric Bond for contributing to this post.

Rising heat tips sea turtle gender balance as hatchlings emerge nearly all female