Mote Marine Laboratory

Hot Mamas, Cool Daddies

By: Susannah Costello

Researchers have found that the sex of turtle hatchings depends on nest temperatures

Mote’s Sea Turtle Program recently contributed to a hatchling sex determination study conducted by Dr. Jeanette Wyneken of Florida Atlantic University, an adjunct scientist at Mote, and Dr. Larry Crowder of Duke University. The goal of the EPA-funded study was to determine sex ratios of hatchlings produced on geographically different beaches of various sand types and with different temperatures.

Researchers examined hatchlings from 10 nesting beaches along four southeastern states in what was the first large-scale study of sex ratios. They documented that the sex of the hatchling is determined by the nest environment. Sea turtles do not have chromosomes like human Xs and Ys that determine sex.

Cooler temperatures tend to produce males while warmer temperatures produce females.

In an initial breakthrough finding, the study determined that there were far more male hatchlings being produced on all Florida beaches than what had been determined previously. There were also far fewer males coming from the northern beaches than expected.

Very few males are being produced north of Jacksonville, says Crowder. In fact, a large and recovering adult loggerhead population in South Florida is roughly stable but it’s producing almost 80 percent females.

With a northern population still in decline and not producing nearly the percentage of males researchers initially believed, the preliminary results are surprising and even alarming, he says.

As both Crowder and Wyneken note, if researchers continue to see such highly skewed sex ratios, it will be alarming. The public will have to start thinking about the implications of global warming and climate change.

Learn more about: Sea turtles