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Female Turtles “Talk” to Their Hatchlings, Scientists Discover

A photo of a giant South American river turtle.
A giant South American river turtle. Photograph by Joel Sartore, National Geographic Creative

The first time Richard Vogt tried to catch a giant South American river turtle (Podocnemis expansa), the hundred-pound (45-kilogram) reptile dragged him 30 feet (9.1 meters) down to the bottom of a river. It would have kept going, too, if he hadn’t decided to give up and let go of the shell.

Vogt is a herpetologist with Brazil’s National Institute for Amazonian Research who recently received the ninth annual Behler Turtle Conservation Award for lifetime achievement. Twenty-five years after that giant first pulled him under, he’s still studying these fascinating creatures. In fact, in the most recent issue of Herpetologica, the first known evidence that turtles provide parental care for their hatchlings was reported by Vogt and Camila Ferrara of the Wildlife Conservation Society. 

“The giant South American river turtle is one of the most social species of turtle in the world,” Vogt said. “They migrate together, they nest communally, and they hatch out in huge numbers together.”

And now, thanks to 220 hours’ worth of underwater recordings, Vogt and his team have shown that female giant South American river turtles in Brazil call to their hatchlings once they reach the water for the first time.

Pillow Talk

The very idea that turtles can communicate with each other using sound is rather new. Turtles lack vocal cords and their ears are internal, so for many years scientists simply assumed turtles were, as Vogt called it, “deaf as a post.”

Over the past 50 years of working with these animals, it always seemed strange to him that some species could seem so downright organized without some form of communication.

For instance, when giant South American river turtles (also known as Arrau river turtles) leave the water to dig a nest and lay eggs, they do so in single file. Vogt has witnessed a queue of females stretching 16 turtles long—though regrettably, that tally was reduced to 15 after a black caiman picked off the last in line.

In recent years, however, herpetologists have started to detect a whole host of sounds made by the reptiles, both in and out of the water.

“Not only are the turtles talking,” said Vogt, “they’re talking before they hatch.”

Vogt suspects that sounds made while the hatchlings are still in the shell may stimulate the group to emerge all at once. They may also account for the many premature hatchlings commonly found at the bottom of a nest. Presumably, the turtles hear their siblings’ calls and pop out before they’re physically ready.

Come to Mama!

Unlike other species that hatch en masse, such as sea turtles, giant South American river turtles don’t have to start their lives as orphans.

In fact, as soon as the tiny turtles hit the water for the first time, females that have been waiting in the area since they laid eggs two months ago start calling out to the babies. Once the two generations meet up, they migrate together from the beach back to the river’s flooded forests.

A photo of a Giant South American river turtle hatchling emerging from its shell.
A giant South American river turtle hatchling emerges from its shell. Photograph by C. Ferrara, Wildlife Conservation Society

The scientists aren’t sure yet if the females in the water are actually related to the hatchlings, but they plan to do blood tests later this year to determine whether an individual mother might somehow recognize and join up with her own offspring. A hatching event can mean thousands and thousands of babies hitting the water at the same time, so this kind of recognition would be all the more impressive.

Not Exactly Chatterboxes

One of the reasons it’s taken us so long to learn about these sounds is that turtles communicate at frequencies in the lower range of the human audible spectrum. Like whales, turtles probably use these frequencies because the sounds can travel long distances underwater.

It helps to have a young set of ears, because humans over the age of 50 have a difficult time detecting low-frequency sounds. Oh, and you’ll also need some patience. Vogt said you can place a hydrophone in the water next to a turtle and expect to hear only 15 to 20 sounds over the course of eight hours.

And it only works in the wild. “Take a turtle out of the wild and it’ll talk for a few days and then just shut up,” Vogt said.

So, what do turtles sound like? Vogt compares the sounds to clicks, clucks, and hoots.

Note that the individual sounds on these recordings have been amplified and repeated to enable the listener to better hear the differences in vocalizations. In the wild, the turtles make these individual sounds with long periods of silence in between. All recordings are by C. Ferrara of the Wildlife Conservation Society.

Cry for Help?

Now that we know giant South American river turtles rely on communication to enable hatching and migration, Vogt said it’s time to determine what effect shipping noise might have on the animals. There’s already plenty of evidence that the noise created by oil and gas exploration is detrimental to a wide variety of marine mammals, so perhaps turtles are also at risk. (See “Will Atlantic Ocean Oil Prospecting Silence Endangered Right Whales?”)

Unfortunately, this species is also under threat from the illegal wildlife trade and local appetites. Brazilians prize turtle eggs as a delicacy, and the turtles themselves are often slaughtered for meat. A recent trend toward dam building in the country rounds out the list of potential threats. (See also “Costa Rican Murder Shines Light on Poaching, Drug Nexus.”)

While the International Union for Conservation of Nature currently lists the giants as being of “Least Concern,” the Tortoise and Freshwater Specialist Group (of which Vogt is part) has strongly recommended a change in status to “Endangered.”

A Whole New Line of Inquiry

This sort of research is interesting not only for the effects it might have on our understanding of a particular species, but also for turtles in general.

“This research is exciting because it basically opens up a whole new line of inquiry related to turtle behavior,” said David Steen, a conservation biologist specializing in turtles and snakes at the Alabama Natural Heritage Program at Auburn University.

“That we know so little about the wildlife around us is exciting because it reinforces that one should never just accept conventional wisdom when conducting research,” Steen said. “We still have a lot to learn.”

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Comments

  1. Star Thrower
    A southern planet where I'm an alien
    August 25, 1:55 pm

    The more I read about animals, the more I begin to believe that all are sentient, at least with the planet, and to some level. Seems like every time I read about a species I once thought “safe” to eat, scientists have found out otherwise, and I have to cross it off my list. I’m starting to believe that going vegetarian would just be simpler, and healthier too.

  2. Scott
    Zurich, ch
    August 22, 10:35 pm

    Dear Kimberly ,
    There is enough ‘oil’ and natural gas to last way beyond your great, great, great great grandchild’s birth. With the new technologies in deep water exploration, the new finds in North America, Mexico, Russia, and elsewhere have enough oil for centuries. ( especially since we are beginning to use alternative fuel sources) . I would love to have a clean alternative, however please get your facts straight. One of the big reason there has not been a serious rush for cleaner, safer energy is because we are still awash in fossil fuels. It is NOT big Oil. It is big supply and demand. It would be the best for the slternative energy movement to discontinue its demonization of oil and begin to understand economics. It is big Money. The average Joe/Jane will not be ok with the drastic change in their collective lives if the use of oil was prohibited. Do you have any value how forcefully linked we are to fossil fuel use. It isn’t because this illusion of big fat cat oil executive sitting in a room to conspire the dependency of their product . You should research , actually how secretive each oil company is to the oil. There is no big collaboration – that us a myth.

  3. Kimberly Williams
    United States
    August 22, 6:45 am

    We are long over due with implementing Green energy! Why on earth with all our technology should we still be fighting over oil, damaging the environment, and wondering how many people should we alllow to die because there is not enough oil to sustain our population but for a few more yeas! The oil Baron’s are planning our deaths when we should be spending our time, energy and money on trading reliance on oil for utilizing new technologies, as well as, our other more abundent natural resources. I am talkling about the sun, wind, earth and water! I am sick of the oil baron’s dictating which way the wind blows! We need to switch over and today is not a day to soon. Also, we do not need to utilize something so dangerous as nuclear energy! All that dangerous stuff needs to be shut down!

  4. Carmel Keely
    United States
    August 21, 5:14 pm

    Interesting article but I take issue with the statement that domesticated turtles don’t communicate vocally. I’ve known a Red Earred Slider turtle that frequently made vocalizations. If the room was quiet and he was familiar and comfortable with the people in it he’d make all sorts of clicks and whistling noises. It took a while for us to be convinced it was coming from him. With the arrival of a puppy in the house he even started to imitate some of it’s quieter whines. You’d start looking for the puppy to see what was wrong, realize that the puppy was out of the house, and see the turtle staring at you trying to get your attention to feed him. Reptiles can certainly surprise you.

  5. Miriam Delgado
    Venezuela
    August 21, 1:59 pm

    I always say that everything in nature is astonishing. This article is too interesting.

  6. Dr. Davare V.R.
    AHMEDNAGAR(MS) INDIA
    August 20, 10:13 pm

    Thanks to NASA ‘s research team which provide so much interesting information of this planet which we have been given a chance to live in.I become fully emotional when I get new information of nature from NASA as well as NATIONAL GEOGRAPHIC.

  7. Hayward Wang
    China
    August 20, 10:18 am

    Sure we should pay more attention on environmental protection and this is related to the destiny of the Earth.

  8. Barbara Galbreth
    Washington State
    August 19, 2:39 pm

    Researchers ,should stay focused and push they’re peers into healthy environmental changes for all ocean and aquatic dependent creatures,(that includes us). Nothings going to get better, if we don’t rid the world’s oceans of human garbage dumps. I hope some of this research closes and cleans up many toxic ocean dumping sites. I’m aware dumping starts from debris off waste trucks also littering that ends up blown into rivers and water ways. This is where we use your brains with our dollars to fix these problems,for the benefit of all living creatures. Thank you.