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article imageScientists study Amazon turtles that ‘talk,’ take care of young

By Martin Laine     Aug 19, 2014 in Science
A team of scientists studying the Giant River Turtles of the Amazon River have found the species uses various sounds to communicate with each other, even one for newly-hatched nestlings, a previously unknown parenting behavior.
“These distinctive sounds made by turtles give us unique insights into their behavior, although we don’t know what the sounds mean,” said Dr. Camila Ferrara, Aquatic Turtle Specialist, for the Wildlife Conservation Brazil program, according to an article on the Wildlife Conservation Society website. “The social behaviors of these reptiles are much more complex than previously thought.”
Ferrara is one of the authors of a study published recently in the journal Hepetologica.
According to the National Aquarium website, the Giant Amazon River Turtle (Podocnemis expansa) is native to the Amazon and Orinoco River Basin. One of the largest freshwater turtles, the female can grow to be nearly three feet long and weigh 200 pounds. The males grow to slightly more than half that size.
They spend most of their time in the water, with only the females emerging out onto sandbanks to lay their eggs in communal nesting sites, where thousands will congregate. Each female will lay anywhere between 50-150 eggs.
While many of these behaviors have been well-known for years, the research team wanted to find out what, if any, role the sounds these turtles make have in coordinating these behaviors.
Working in an area called Rio Trombetos between 2009 and 2011, the research team recorded 220 hours of sounds using both microphones and hydrophones.
Spectographic analyses revealed a number of interesting features.
Sounds made during migration tended to be at a lower frequency, possibly to make them travel over longer distances. Sounds during nesting were generally at a higher frequency, possibly because higher frequencies travel better through air.
The greatest mix of sounds came from females congregating just before they begin nesting. When they reach a particular nesting site, the females emerge from the water one-by-one in single file, even though there may be hundreds or even thousands of individuals. The scientists theorize the sound may somehow help in choosing the site and organizing themselves.
Hatchlings themselves emit sounds, even before they hatch, possibly as a way of stimulating the group hatching. Adult females will emit a particular sound after hatching, possibly as a way of guiding the nestlings to the water. In addition, sonic transmitters show the young turtles will stay with an adult for female for about two months after hatching.
At one time, these river turtles were abundant, but they have been reduced to the point where they are now considered an endangered species. Humans are their primary predator, both for their meat and eggs. Before protections were put into place, some 48 million eggs were taken per year. Poaching continues to be a threat.
More about river turtles, Wildlife conservation society, Endangered species
 
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