The boys are back in town.

After more than a dozen years of nearly every sea turtle born on Florida beaches being female, a small but significant number of males were born last year, said Jeanette Wyneken, a biological sciences professor at Florida Atlantic University.

Wyneken hasn't finished her research on the 2018 hatchlings, but current data points to about 20 percent of them being male.

"It's not a lot, but it's better than nothing," she said.

And for the past couple of years, nothing has been the norm.

Wyneken studies mostly loggerhead sea turtles, by far the most prevalent species nesting on Florida beaches. In the past 13 years, there have been seven years with no male loggerhead hatchlings found at test beaches on the state's Atlantic and Gulf coasts, Wyneken said.

Since Wyneken started studying sea turtles in 2002, there hasn't been a year with a majority of males. The closest was 2013, when 32 percent of the hatchlings were males.

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The reason for the female predominance: Wyneken and other researchers suspect climate change.

The sex of sea turtle hatchlings is determined by the temperature of the sand around the eggs: the hotter the sand, the more likely the hatchlings will be female.

"If a nest is really hot, say 88 degrees, it's going to be all females," Wyneken said.

At the other end of the spectrum, a 77-degree nest would be all males. An 84-degree nest will produce some males. Rain also has an effect. A hot, damp nest is more likely to have a few males than a hot, dry nest.

"In Florida, there are very few years where it's cool enough to produce males," Wyneken said.

But cool, rainy weather last April and June resulted in all the hatchlings Wyneken tested from two nests to be males.

Nests laid a little after that period tended to have a mix of males and females, Wyneken said, and those laid in the heat of the summer went back to being all females.

Wyneken takes about 10 hatchlings from nests on beaches in Boca Raton and Juno Beach on the Atlantic Coast and Sanibel Island on the Gulf Coast; but she said the males' return probably happened on the Treasure Coast, as well.

"The Treasure Coast had the same late-spring, early summer weather that we had down here," the Boca Raton-based Wyneken said.

Turtle nesting season runs from early March through October. Leatherbacks are the first to lay nests, which could be why they have the highest percentage of males.

Loggerheads incubate during the hottest months of the year: June, July and August. Green sea turtles incubate a little later: in July, August and September.

A nest typically has about 110 eggs, and Wyneken usually takes about 10 percent of the hatchlings from a test nest to study.

They're raised in a lab until palm-sized, anywhere from 3 to 7 months old, and big enough to determine the gender, which is done by making a small incision and "looking under skirts" with a camera, Wyneken said.

The turtles aren't harmed in the process Wyneken said.

Are enough males being born to perpetuate the species?

"We don't know how many males is enough," Wyneken said.

Male sea turtles reach sexual maturity earlier than females; and while female sea turtles lays eggs only every two, three or four years, males are sexually active every year.

"What the males lack in numbers they make up for with frequency," Wyneken said.

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Shading or watering turtle nests to keep them cool would be a stop-gap way to produce more males, Wyneken said, but the ultimate answer is cutting down on greenhouse gases that cause climate change and "keep the world from getting hotter."