Two native turtles are vying to survive in a coastal Australian river. One doesn't belong there

The Manning River helmeted turtle, also known as the Guraa, is a unique freshwater turtle found only in the coastal rivers of New South Wales, Australia. This ancient species, dating back 55 million years, is classified as endangered due to threats such as habitat loss, illegal pet trade, and invasive predators. However, a new study reveals an unexpected threat to this species: the Macquarie River turtle, also known as the Murray River turtle.

Native to several river systems across Australia, this turtle is listed as critically endangered in Victoria and vulnerable in South Australia. Recent evidence suggests that the Macquarie River turtle has been spreading beyond its natural range and has been detected in nine tributaries of the Manning River. These turtles compete with the Manning River turtle and other endangered species for resources and can harbor diseases like the Bellinger River virus.

Furthermore, there is evidence that hybridization between the two species is already occurring in certain rivers. To monitor the presence of the Macquarie River turtle, researchers developed highly sensitive and species-specific environmental DNA tests. These tests can detect the DNA shed by turtles in river water, allowing for non-invasive monitoring.

The researchers tested water samples from five locations across the Manning River catchment and found that while they detected Manning River turtles at all locations, they did not find Macquarie River turtles. This method could prove valuable for tracking the spread of turtle species outside their natural ranges and contributing to local conservation efforts.