August 17, 2014
Talking River Turtles Produce Vocalizations To Coordinate Activities, Care For Young
redOrbit Staff & Wire Reports - Your Universe Online
Giant South American River Turtles are capable of producing a variety of vocalizations in different behavioral situations, including while they are caring for their young, a team of US and Brazilian scientists report in a recent edition of the journal Herpetologica.The researchers have been studying the communication and social behavior of these creatures, which are known for their longevity and their protective shells, and have discovered that they stick around to help rear their offspring. Furthermore, they say the river turtles use multiple types of vocal communication to coordinate their social behaviors, and that female turtles possess a unique call that allows them to ‘talk’ to their offspring.
[ Listen: Vocalizations made between adults and hatchlings (individual sounds repeated for the listener's benefit). Credit: C. Ferrara/Wildlife Conservation Society ]
This observation marks the first recorded instance of parental care in turtles, and according to study author Dr. Camila Ferrara, an Aquatic Turtle Specialist for the Wildlife Conservation Society (WCS) Brazil Program, “These distinctive sounds made by turtles give us unique insights into their behavior, although we don't know what the sounds mean. The social behaviors of these reptiles are much more complex than previously thought.”
While some of the behaviors of the Giant South American River Turtle (Podocnemis expansa) have been known for some time, including their tendency to gather together in large numbers during the nesting season, the methods they use to coordinate their activities were not as well understood. Dr. Ferrara and her colleagues set out to determine how acoustic mechanisms could be used to facilitate social behavior and group aggregation during this period.
“From September 2009 to October 2011, the sound repertoire of P. expansa was identified during the nesting period, which begins with the migration of the turtles from the flooded forests to the nesting beaches and terminates when the hatchlings emerge and the females migrate with the hatchlings to the flooded forests,” the authors wrote.
They recorded sounds when the turtles were active in various behavioral patterns, including migrating, aggregating in front of nesting beaches, nesting during the nighttime, waiting in the water after having nested, and while waiting for their hatchlings to arrive. Their recordings revealed six different types of sound, leading the researchers to conclude the turtles are a social species and use sound to synchronize their activities during the nesting season.
Dr. Ferrara and her fellow investigators worked in the Rio Trombetas region of the Brazilian Amazon from 2009 through 2011, and captured a total of 270 individual sounds made during 220 hours of recording captured using both microphones and hydrophones. Those recordings were reviewed using spectrographic analyses, which allowed the research team to establish the six subdivisions of vocalizations and correlate them with specific behaviors.
While migrating through the river or basking, the turtles tended to make low frequency sounds, which the study authors believe might have been to facilitate contact between turtles over longer distances. During nesting, the sounds tended to be higher in frequency, possibly because they travel better in shallow water and in the air.
The most diverse sounds are those used by female turtles preparing to nest. The research team suspects that the animals use these noises to decide on a specific nesting location and to synchronize their movements, as the creatures tend to leave the water in a single-file procession. Hatchling turtles also make sounds before they hatch, and continue to do so as the leave the nest chamber, which could help stimulate group hatching.
“Groundbreaking studies such as this one can help us better understand the complex relationships between both individual animals and their environment,” explained Dr. Julie Kunen, Executive Director of WCS's Latin America and the Caribbean Program. “Protecting the still sizable populations of Giant South American river turtles will also enable us to conserve the behavioral richness of these reptiles for future study.”
In addition to Dr. Ferrara of the WCS, scientists participating in the study include Richard C. Vogt of the Instituto Nacional de Pesquisas de Amazônia, and the Associação de Ictiólogos e Herpetólogos da Amazônia (AIHA); Renata S Sousa-Lima of the Cornell Lab of Ornithology; Bruno M.R. Tardio of the Instituto Chico Mendez; and Virginia Campos Diniz Bernardes of the Instituto Nacional de Pesquisas de Amazônia and the AIHA.
Image 2 (below): A Giant South American river turtle hatchling emerges from its shell. Credit: C. Ferrara/Wildlife Conservation Society