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Turtle Eggs Respond to Heatwaves

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    A loggerhead sea turtle hatchling makes its way to the ocean along Haulover Beach in Miami, Florida. (AP/Lynne Sladky)
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    A loggerhead sea turtle egg (AP/Lynne Sladky)
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    A marked sea turtle nest in Surfside, Florida (AP/Wilfredo Lee)
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    Workers at Zoo Miami’s Sea Turtle Hospital feed a loggerhead sea turtle named Baymax. He was brought to the hospital after being bitten by a shark. (AP/Wilfredo Lee)
  • 5 tsp
    In 1966, a scientist named Madeleine Charnier first recorded the observation that temperature determined the sex of reptiles during her studies of red-headed agama lizards. (AP/Sayyid Azim)
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  • 5 tsp


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This summer saw record-breaking global heatwaves. The United Kingdom, Australia, and France experienced all-time high temperatures in 2022. Heatwaves can affect human health, decrease agricultural yield, and fuel wildfires and droughts. And on the U.S. southeastern coast, they can even affect sea turtle births.

God created many reptiles and some fish to experience a thermo- (or temperature-) sensitive period known as TSP. According to biologist Valentine Lance, TSP is the window of time—usually mid-incubation—when a developing turtle becomes either a male or female. So when a momma turtle digs a nest on a beach, the sand temperature determines the gender of her hatchlings. Warm temperatures produce female turtles; cool temperatures produce males.

Florida’s sea turtles are struggling with their gender ratio. Intense heat in recent years has caused the sand on some beaches to get so toasty that nearly every turtle born is female.

Scientists have known about TSP since the late 1960s. But they still don’t understand exactly how or why temperature affects reptile gender. Yet multiple studies confirm the phenomenon.

Today, many people worry about rising temperatures on Earth—especially those who don’t acknowledge the sovereign reign of an all-wise Creator. (Matthew 6:34)

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

“Over the years, you’re going to see a sharp decline in their population because we just don’t have the genetic diversity,” says Melissa Rosales Rodriguez, a sea turtle keeper at the recently opened turtle hospital at the Miami Zoo.

Studies from Australia echo the findings in Florida.

Concern for the turtle population has biologists studying ways to save every turtle.

At Zirkelbach’s Florida Keys Turtle Hospital, workers “rescue, rehabilitate, and return threatened and endangered sea turtles to the wild.” The hospital has been working with sick and injured sea turtles for over 36 years. Staff members there have already helped more than 2,000 turtles along over 200 miles of Florida coastline.

But Zirkelbach says biologists and hospital workers couldn’t do it alone. “We actually depend on visitors to the Keys,” she says, referring to those who spot and make rescue calls about struggling turtles. They are, she says, the hospital’s “eyes on the water.”

Why? God rules the winds and waves, the Sun and Moon, and all things. He wants humans to care for His creation, but we need not worry that His sovereignty will ever fail.