Cli­mate change is turn­ing Florida’s sea tur­tles fe­male

The Bradenton Herald - - Front Page - BY ADRI­ANA BRASILEIRO abrasileir­[email protected]­ami­her­

Two dozen tiny leatherbac­k tur­tles swam around in small tanks, at­tached by fish­ing lines to a sys­tem that kept them from hit­ting walls and hurt­ing them­selves. As an open-wa­ter species, leatherbac­ks don’t rec­og­nize bar­ri­ers, so they are kept on leashes at Florida At­lantic Uni­ver­sity’s lab at Gumbo Limbo Na­ture Cen­ter in Boca Ra­ton.

It was lunchtime and pro­fes­sor Jeanette Wyneken was feed­ing them a con­coc­tion she per­fected over the years: or­ganic gelatin, fish oil, pro­tein and vi­ta­mins, shaped into lit­tle squares. Leatherbac­ks are picky

eaters, feed­ing mostly on jel­ly­fish.

Wyneken planned to fat­ten the baby tur­tles for a few weeks, un­til they are about the size of her palm and can un­dergo a la­paroscopy to check their other­wise im­per­cep­ti­ble gen­der — a process that re­quires in­sert­ing a tiny cam­era to view in­ter­nal or­gans. Dozens of hatch­lings will go through Wyneken’s lab this nest­ing sea­son as part of her lon­grun­ning tur­tle sex-ra­tio re­search in South Florida.

Yet even be­fore any test­ing is done and the hatch­lings are re­leased back into the ocean, the sci­en­tist al­ready knows there is a strong chance most of the tur­tles will be one gen­der: fe­male.

As is the case with some rep­tiles, the sex of sea tur­tles is de­ter­mined by the tem­per­a­ture of the sand where the eggs in­cu­bate. With cli­mate change turn­ing up the heat in South Florida, pro­duc­ing longer and hot­ter sum­mers, sea tur­tle gen­der bal­ance is be­ing thrown way out of whack.

“It’s scary,’’ said Wyneken. “I’m see­ing more and more all-fe­male nests, and even when we have males, it’s a very small per­cent­age.’’

Wyneken’s re­search over the past 20 years shows that the num­ber of males is de­creas­ing across the three species she mon­i­tors, even as they lay eggs at dif­fer­ent times dur­ing the March-Oc­to­ber nest­ing sea­son. Us­ing the past decade as a ref­er­ence, she said that seven out of the 10 years pro­duced 100 per­cent fe­male hatch­lings. The three years in which nests pro­duced males, their num­bers ranged from just 10 to 20 per­cent.

In ad­di­tion to the leatherbac­ks, the world’s largest sea tur­tle species, Wyneken tests the gen­ders of log­ger­heads and green tur­tles in Boca Ra­ton, Juno Beach and Sani­bel Is­land, where nest­ing ac­tiv­ity is closely mon­i­tored and tem­per­a­tures in nests are tracked year­round.

What hap­pens on beaches in Florida is im­por­tant for sea tur­tle pop­u­la­tions: It’s the only state in the con­ti­nen­tal U.S. where leatherbac­k tur­tles reg­u­larly nest; it hosts some of the world’s largest nest­ing ag­gre­ga­tions of log­ger­heads; and it’s home to the sec­ond-largest num­ber of green tur­tle nests in the West­ern At­lantic, ac­cord­ing to the Florida Fish and Wildlife Con­ser­va­tion Com­mis­sion.

In the­ory, sex ra­tios among leatherbac­k tur­tles, which lay eggs early in the sea­son be­fore the height of the sum­mer in South Florida, should be more bal­anced than that of log­ger­heads, which usu­ally start nest­ing in June and whose eggs in­cu­bate in the hottest months of the year. And green tur­tles tend to lay eggs later, when beaches are be­gin­ning to cool in late Au­gust and Septem­ber, so more males should hatch from their nests com­pared with the other two species.

But Wyneken said that for the past few years, es­pe­cially since scorch­ing sum­mers of 2015 and 2016, she hasn’t seen a sig­nif­i­cant dif­fer­ence in the sex ra­tios of the species in South Florida: It’s girls, girls and more girls, in ev­ery nest.

And things are get­ting worse. July was the hottest month ever recorded in the world, com­ing in slightly higher than the pre­vi­ous record, which was July 2016, ac­cord­ing to data from the World Me­te­o­ro­log­i­cal Or­ga­ni­za­tion and the Coper­ni­cus Cli­mate Change Ser­vice. There were wild­fires in the Arc­tic, a huge ice melt event in Green­land and 90-de­gree weather in Alaska. Euro­pean cities baked, with the tem­per­a­ture in Paris reach­ing 108.7 de­grees. And this year’s record tem­per­a­tures did not get a boost from a strong “El Niño,” which heats up sur­face sea wa­ter and con­trib­utes to warmer tem­per­a­tures, as hap­pened in 2016.

“I never thought that what started as re­search on sea tur­tle gen­der ra­tios on a cou­ple of Florida beaches would be­come a mea­sur­ing stick for cli­mate change, but that’s what I’m see­ing,’’ Wyneken said. Be­fore warm­ing tem­per­a­tures be­gan to dra­mat­i­cally skew the sex of sea tur­tles to­ward fe­male, the same nest would pro­duce girls and boys, with eggs buried deeper in the sand lead­ing to males and eggs on the warmer sur­face gen­er­at­ing fe­males.

What sci­en­tists have ob­served in South Florida is hap­pen­ing in other sea tur­tle nest­ing ar­eas around the world.

On Aus­tralia’s Raine Is­land, the big­gest green tur­tle nest­ing ground in the Pa­cific, the ra­tio was 116 fe­males to one male in a 2018 study led by Michael Jensen and Cam­ryn Allen, sci­en­tists with the Na­tional Oceanic and At­mo­spheric Ad­min­is­tra­tion. The study found that older tur­tles that had hatched 30 or 40 years ear­lier were mostly fe­male, but only by a 6 to 1 ra­tio. Younger tur­tles, how­ever, born dur­ing the last 20 years, were more than 99 per­cent fe­male.

Jensen and Allen “com­bined ge­netic and en­docrine tech­niques to show that an im­por­tant green tur­tle pop­u­la­tion has pro­duced pri­mar­ily fe­males for two decades, sug­gest­ing that com­plete fem­i­niza­tion is pos­si­ble in the near future,” said the re­search.

An­other study done re­cently with green tur­tles in Guinea-Bis­sau, West Africa, by the Uni­ver­sity of Ex­eter and Por­tu­gal’s Ma­rine and Environmen­tal Sciences Cen­ter showed sim­i­lar re­sults.

But how soon could tur­tle pop­u­la­tions run out of males?

Sea tur­tles have been around in some form for more than 200 mil­lion years, weath­er­ing all kinds of ex­treme weather events and even sur­vived the ex­tinc­tion of the di­nosaurs 66 mil­lion years ago.

“These sex ra­tio find­ings are very con­cern­ing and we want to raise aware­ness about the is­sue, but there is also some hope,’’ said David God­frey, ex­ec­u­tive di­rec­tor of the Sea Tur­tle Con­ser­vancy, a Florida re­search and con­ser­va­tion non­profit. “Sea tur­tles are amaz­ing at adapt­ing to changes in their habi­tat and in the en­vi­ron­ment.’’

There have been plenty of suc­cess sto­ries of re­cov­ery of sea tur­tle pop­u­la­tions. The Con­ser­vancy’s green tur­tle con­ser­va­tion pro­gram at Tor­tuguero, a ma­jor nest­ing spot in Costa Rica, started in 1959 and since then the pop­u­la­tion has in­creased six­fold, mak­ing the colony the largest in the West­ern Hemi­sphere.

Also, one male tur­tle goes a long way. Sea tur­tles are polyg­a­mous an­i­mals and one male will mate with many fe­males. They have a long life­span of around 50 years, but some species can live longer. Most sea tur­tles take decades to ma­ture — be­tween 20 and 30 years — and fe­males are ac­tively re­pro­duc­tive for about 10 years. De­pend­ing on the species, fe­males will nest be­tween two and eight times each sea­son, lay­ing about 100 eggs in each nest.

In Florida, sea tur­tle nest­ing ac­tiv­ity has seen some ups and downs over the past few years, with a slightly neg­a­tive trend since 2014. Over­all, nest counts re­cov­ered sig­nif­i­cantly from the lows of the ‘80s and ‘90s, a re­sult of con­ser­va­tion ef­forts in more densely pop­u­lated ar­eas. Nest­ing varies widely de­pend­ing on the species and lo­ca­tion. This year, researcher­s on the Gulf Coast and in Palm Beach County also are bet­ting on record nest counts con­sid­er­ing the num­bers recorded so far.

The Fish and Wildlife Con­ser­va­tion Com­mis­sion counted 91,451 log­ger­head nests in the state in 2018, com­pared with 86,870 in 2014. But leatherbac­k nests were down at 949 last year, com­pared with 1,604 in 2014. Green tur­tle nests reached 4,545 last year, down from 5,895 four years ear­lier.

Sea tur­tle hatch­lings have never had it easy. Not all eggs in a nest are vi­able, and only a small share of hatch­lings will sur­vive and grow to be­come adults. The eggs may be dug up by rac­coons, foxes or other preda­tors. Those same preda­tors can gob­ble up the ba­bies as they race to the surf af­ter emerg­ing from their nests. Once in the ocean, they aren’t safe: Crabs and other ma­rine an­i­mals feed on baby sea tur­tles.

Ma­ture tur­tles have few nat­u­ral preda­tors, but hu­mans have done a great job in cut­ting their sur­vival odds sig­nif­i­cantly. Poach­ing of the eggs and the killing of nest­ing tur­tles for their meat or to make frames for eye glasses or jew­elry have de­pleted pop­u­la­tions all over the world. But the great­est threat to sea tur­tles is fish­ing gear, as hun­dreds of thou­sands of tur­tles are ac­ci­den­tally caught by trawl nets and on long­line hooks.

And now there is cli­mate change. Can they adapt by nest­ing in cooler beaches? Will fe­males start look­ing for shadier lo­ca­tions to lay their eggs?

“All or­gan­isms tend to adapt to their chang­ing en­vi­ron­ment by evolv­ing through nat­u­ral se­lec­tion, but the ques­tion is, will tur­tles adapt as fast as the cli­mate is chang­ing around them?’’ said Fredric Janzen, an evo­lu­tion­ary bi­ol­o­gist at Iowa State Uni­ver­sity who was one of the first sci­en­tists to con­nect cli­mate change to tem­per­a­ture­de­pen­dent sex de­ter­mi­na­tion in tur­tles. In a 1994 study ti­tled “Cli­mate Change and Tem­per­a­ture­De­pen­dent Sex De­ter­mi­na­tion in Rep­tiles,” Janzen found that even a small in­crease of 1.5 de­grees Cel­sius (2.7 de­grees Fahren­heit) was enough to dras­ti­cally skew the sex ra­tio of the painted tur­tles in his re­search.

In his opin­ion, changes are oc­cur­ring faster than they did prior to hu­man in­flu­ence, and this can po­ten­tially — and fa­tally — out­pace the abil­ity of some species to adapt.



JENNIFER KING jk­[email protected]­ami­her­

Sawyer Wiles, 21, a bi­o­log­i­cal tech­ni­cian at the FAU Ma­rine Lab­o­ra­tory, feeds the baby leatherbac­k tur­tles. They feed mostly on jel­ly­fish. With cli­mate change turn­ing up the heat in South Florida, pro­duc­ing hot­ter sum­mers, sea tur­tle gen­der bal­ance is be­ing thrown way out of whack.

JENNIFER KING jk­[email protected]­ami­her­

Ali Courte­manche, 27, takes notes on a new tur­tle nest as her col­league, Tay­lor Roe, 30, mea­sures the dis­tance from the nest to the dune on the beach at the Gumbo Limbo Na­ture Cen­ter in Boca Ra­ton.

JENNIFER KING jk­[email protected]­ami­her­

Dr. Jeanette Wyneken, a pro­fes­sor of bi­o­log­i­cal sciences at FAU and the di­rec­tor of the FAU Ma­rine Lab­o­ra­tory, checks on baby leatherbac­k tur­tles, like the one at top, at the facility in June.

JENNIFER KING jk­[email protected]­ami­her­

Sawyer Wiles, 21, a bi­o­log­i­cal tech­ni­cian at FAU’s Ma­rine Lab­o­ra­tory, feeds a baby leatherbac­k tur­tle a mix­ture of gelatin and pro­tein.

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