Reaching 35 in. in length, the Arrau turtle is one of the biggest of all the freshwater turtles. Like its large marine relatives, it travels huge distances to lay its eggs at traditional breeding grounds. Many hundreds of turtles congregate at these sandy sites every year, and the predictability of the event makes the animals vulnerable to local hunters who kill the adults and harvest their eggs. As a result, the Arrau turtle is now an endangered species.