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.
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.
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.