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

Two species of turtles are contending for survival in a coastal Australian river – one belongs there, one does not. The Manning River helmeted turtle (Myuchelys purvisi) is a striking turtle, native only to the Manning River region in New South Wales, Australia. Yet, this ancient turtle, with a lineage dating back 55 million years, faces an urgent threat: the introduction of another native but locally-introduced turtle species.

The Macquarie River turtle (Emydura macquarii), also known as the Murray River turtle, is native to several river systems across Australia but is now expanding beyond its natural range. This turtle species was possibly introduced to the Manning River catchment in New South Wales in 2007 by people releasing their pet turtles into the river. Since then, Macquarie River turtles have been detected in nine different tributaries of the Manning River and continue to spread.

Both the Manning River turtle and the endangered Bellinger River turtle (Myuchelys georgesi), and the critically endangered Manning River turtle, face competition for resources and disease from the Macquarie River turtle. Furthermore, hybridisation, or the cross-breeding of different species, poses the most pressing threat. This hybridisation can lead to the loss of distinct species when hybrid animals rapidly reproduce and replace the endangered populations.

Currently, turtle ecologists can detect the presence of these turtles by snorkelling, trapping, or underwater video surveys. However, these methods are time-consuming and costly, and they often involve handling the turtles. To develop a more efficient monitoring method, researchers have created highly sensitive and species-specific environmental DNA tests.

By detecting the DNA traces left behind by turtles in river water, these tests can pinpoint the presence of Manning River turtles while ensuring the Macquarie River turtles do not infiltrate their habitat.