"Long before it's in the papers"
January 27, 2015


Turtles found to communicate, care for young

Aug. 15, 2014
Courtesy of the Wildlife Conservation Society
and World Science staff

Some tur­tles use vo­cal calls to stick to­geth­er and to care for young, ac­cord­ing to a stu­dy.

Sci­en­tists are re­port­ing that Gi­ant South Amer­i­can riv­er tur­tles use sev­er­al kinds of calls to co­or­di­nate their acti­vities, in­clud­ing one call from fe­males to their hatch­lings in what is the first in­stance of recorded pa­ren­tal care in tur­tles.

An adult Giant South Amer­i­can ri­ver tur­tle. (Cre­dit: C. Fer­ra­ra/WCS)

The find­ings show these rep­tiles’ so­cial be­hav­iors “are much more com­plex than pre­vi­ously thought,” said Ca­mila Fer­ra­ra, aquat­ic tur­tle spe­cial­ist work­ing for the New York-based Wild­life Con­serva­t­ion So­ci­e­ty and a co-author of the stu­dy, pub­lished on­line in the jour­nal Her­peto­log­ica in June. 

Some be­hav­iors of the Gi­ant South Amer­i­can riv­er tur­tle have been well known, in­clud­ing a ten­den­cy to group in huge num­bers dur­ing their nest­ing sea­son. But just how they co­or­di­nate their ac­ti­vi­ties is un­ex­plained. Work­ing at the Trom­be­tas Riv­er in the Bra­zil­ian Am­a­zon be­tween 2009 and 2011, the re­search­ers cap­tured 270 in­di­vid­ual sounds made dur­ing 220 hours of re­cord­ing, both on the ground and un­der­wa­ter. 

They an­a­lyzed the sounds and di­vid­ed them in­to six dif­fer­ent types made dur­ing the nest­ing sea­son, which be­gins as the rep­tiles leave the sea­sonally flood­ed for­est for nest­ing beaches along riv­er banks. The sci­en­tists al­so sought to link sounds with spe­cif­ic be­hav­iors.

Sounds made while mi­grat­ing through the riv­er or bask­ing tended to be low, pos­sibly to fa­cil­i­tate con­tact over long­er dis­tances, the in­ves­ti­ga­tors said. Vo­cal­iz­a­tions made dur­ing nest­ing tended to be higher, pos­sibly be­cause these trav­el bet­ter in shal­low wa­ter and air.

A baby Giant South Amer­i­can ri­ver tur­tle emerges from its shell. (Cre­dit: C. Fer­ra­ra/WCS)

The great­est va­ri­e­ty of sounds came from fe­males about to nest, the study found. The re­search­ers the­o­rize that they use these sounds to choose a nest­ing site and syn­chro­nize their move­ments. They leave the wa­ter in a single-file pro­ces­sion.

The hatch­lings make sounds be­fore they hatch and con­tin­ue to do so as they clam­ber out of the nest cham­ber on the riv­er beach, the sci­en­tists said. The sounds, the au­thors spec­u­late, may stim­u­late group hatch­ing. The fe­males, in turn, call in re­sponse, per­haps guid­ing the nestlings in­to the wa­ter. These in­ter­ac­tion­ first recorded in­stance of pa­ren­tal care in tur­tles—were fea­tured in a 2012 study ap­pear­ing in the Jour­nal of Com­par­a­tive Psy­chol­o­gy.

Us­ing son­ic trans­mit­ters, the team al­so disco­vered that the hatch­lings stay to­geth­er and mi­grate with adult fe­males for more than two months.

The Gi­ant South Amer­i­can riv­er tur­tle is the larg­est of the side-necked tur­tle family and grows up to 80 cen­time­ters (nearly three feet) in length. The spe­cies is only found in the Am­a­zon Riv­er ba­sin and is now threat­ened by peo­ple eat­ing them and their eggs.

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Some turtles use vocal calls to stick together and to care for young, according to a study. Scientists are reporting that Giant South American river turtles use several kinds of calls to coordinate their social behaviors, including one call from females to their hatchlings in what is the first instance of recorded parental care in turtles. The findings show these reptiles’ social behaviors “are much more complex than previously thought,” said Camila Ferrara, aquatic turtle specialist working for the New York-based Wildlife Conservation Society and a co-author of the study, published in the journal Herpetologica in June. Some behaviors of the Giant South American river turtle have been well known, including a tendency to group in huge numbers during their nesting season. But just how they coordinate their activities is unexplained. Working at the Trombetas River in the Brazilian Amazon between 2009 and 2011, the researchers captured 270 individual sounds made during 220 hours of recording, both on the ground and underwater. They analyzed the sounds and divided them into six different types made during the nesting season, which begins as the reptiles leave the seasonally flooded forest for nesting beaches along river banks. The scientists also sought to link sounds with specific behaviors. Sounds made while migrating through the river or basking tended to be low, possibly to facilitate contact over longer distances, the investigators said. Vocalizations made during nesting tended to be higher, possibly because these travel better in shallow water and air. The greatest variety of sounds comes from females about to nest, the study found. The researchers theorize that they use these sounds to choose a nesting site and synchronize their movements. They leave the water in a single-file procession. The hatchlings make sounds before they hatch and continue to do so as they clamber out of the nest chamber on the river beach, the scientists said. The sounds, the authors speculate, may stimulate group hatching. The females, in turn, call in response, perhaps guiding the nestlings into the water. These interactions—the first recorded instance of parental care in turtles—were featured in a 2012 study appearing in the Journal of Comparative Psychology. Using sonic transmitters, the team also discovered that the hatchlings stay together and migrate with adult females for more than two months. The Giant South American river turtle is the largest of the side-necked turtle family and grows up to 80 centimeters (nearly three feet) in length. The species is only found in the Amazon River basin and is now threatened by people eating them and their eggs.