This muffled creak is what researchers heard repeatedly when they listened to giant South American river turtles swimming together. It could help explain how the animals coordinate their behaviour so well in the nesting season, when females gather in large groups at beaches before laying their eggs.
The researchers used microphones above and below the water to record the turtles at different stages in the season. And when the newly hatched turtles and adults were together in the river, scientists heard a different sound.
(Turtle sounds)
This, they think, is parents guiding newly hatched babies on their first migration. The researchers also say that their study shows how vulnerable turtles could be to man-made noise disturbing this quiet but seemingly vital chatter.