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By Rodrigo Santos Andrade
Two native turtles are vying to survive in a coastal Australian river. One doesn’t belong there
visibility comment0 event September 21, 2026 timer 23:32
Not all conservation threats come from overseas. Some are our own native animals.
Alex PikeThe Manning River Helmeted turtle (Myuchelys purvisi) might just be Australia’s most beautiful freshwater turtle.
With a bright yellow stripe stretching from their nose to the tip of their tail, these striking turtles are hard to miss.
The Manning River turtle is found nowhere else on earth except for the few coastal rivers in New South Wales’ Manning River region. Known as Guraa in the Gathang language of the Traditional Custodians of Birpai-Barray, this ancient turtle has a lineage dating back 55 million years.
However, this ancient species faces a very modern crisis. The Manning River turtle is listed as endangered and is being pushed towards extinction by the pressures of habitat clearing, the illegal pet trade and invasive predators that prey on adult female turtles and their eggs.
But as our new study reveals, this species faces an even more urgent, and perhaps unexpected, threat: another native but locally-introduced turtle.
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An unexpected threat
The Macquarie River turtle (Emydura macquarii), also known as the Murray River turtle, is native to several river systems snaking across Australia. It is also listed as critically endangered in Victoria and vulnerable in South Australia.
However, this species is spreading beyond its natural range. Macquarie River turtles were first found in NSW’s Manning River catchment in 2007, and were possibly introduced by people releasing their pet turtles into the river. These turtles have now been detected across nine different tributaries in the Manning River and are continuing to spread.
Macquarie River turtles are a threat to populations of the critically endangered Bellinger River turtle (Myuchelys georgesi) and the endangered Manning River turtle. These two species are only found in two coastal river systems in eastern Australia. Macquarie River turtles compete with these native species for resources such as food. They can also harbour disease such as the Bellinger River virus.
Hybridisation is perhaps the most pressing threat. Hybridisation occurs when different species breed and produce hybrid offspring. Research suggests it is not a new phenomenon among Australia’s freshwater turtles. However, hybridisation can lead to the loss of distinct species, when hybrid animals rapidly reproduce and eventually replace the endangered population.
Current evidence suggests hybridisation is already occurring in the Bellinger and Kalang Rivers, where the Macquarie River turtle was introduced in the 1990s.
The native Macquarie River turtle (Emydura macquarii) is now found in the Manning, Bellinger and Kalang Rivers.
Ricky Spencer/1 Million Turtles
All in a drop of water
Thankfully, Macquarie River turtles have not yet expanded across the entire Manning River. So tracking their spread is vital to protecting other native turtles.
Currently, turtle ecologists can detect turtles by snorkelling or trapping. They can also observe their behaviour through underwater video surveys. However, these methods can be time consuming and costly, and in some cases mean turtles are handled by humans.
Our new study investigated how else we could monitor the presence of Macquarie River turtles, particularly as they encroach on the Manning River turtle’s habitat.
Specifically, we developed highly sensitive and species-specific environmental DNA tests. When turtles swim through rivers they leave behind traces of their DNA – known as eDNA – that scientists can detect using eDNA tests.
We designed these turtle tests in the lab. We then compared the DNA sequences of our target turtle species with other turtle species that are closely related or live in the same habitat. This ensured our tests were specific to the Manning River and Macquarie River turtles. This matters because river water can contain the DNA of hundreds or even thousands of different species.
We then took water samples from five locations across the Manning River catchment over a period of three days. We did this to see if the eDNA tests could detect the DNA turtles shed into river water. Using a portable eDNA backpack – which filters water from the river to capture DNA – we were able to sample litres of water in minutes while preserving the DNA we collected.
Meanwhile, turtle ecologists from the Redleaf Group, an Australian environmental company, took to the river with mask and snorkel. They physically captured turtles present in the river and recorded important population data.
Results from the snorkelling surveys and our eDNA tests were consistent. Both methods detected Manning River turtles at all five locations but no introduced Macquarie River turtles. However, more research is needed before we can conclusively say Macquarie River turtles were not present at these sites.
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How this research could help
We hope these eDNA tests will help researchers accurately track the spread of turtle species outside their natural ranges.
eDNA tests are valuable because of their versatility. They can be used to pinpoint areas where a target species is present, allowing ecologists to then gather population data using traditional survey methods like trapping and snorkeling. They can also be used to identify broader trends about the distribution of a target species.
Dr Jessica Tout-Lyon with an eDNA backpack, sampling river water in the Manning River catchment.
Aunty Yvonne Harvey
eDNA surveys can act as a powerful citizen science tool. Their straightforward application allows members of the community to collect water samples and contribute to local conservation efforts. These surveys can complement other citizen science projects such as 1 Million Turtles and TurtleSAT, which allow the public to record turtle sightings.
Australians are accustomed to the threats of introduced species from overseas. But as the Macquarie River turtle shows, native species in the wrong locations can also put additional pressure on our already endangered species.
Jessica Tout-Lyon receives funding from the MidCoast Council and the New South Wales Department of Climate Change, Energy, the Environment and Water. She is affiliated with the Manning River Helmeted Turtle Steering Committee.Elise Furlan is Director of Science and Research at NatureDNA. She receives funding from the MidCoast Council and New South Wales Department of Climate Change, Energy, the Environment and Water.Louise Streeting is affiliated with the University of New England and is involved in the Turtles Forever conservation program funded by Local Land Services.Mathew Bell is employed by MidCoast Council, which receives grant funding from external sources including from the New South Wales and Commonwealth governments. He is affiliated with the Manning River Helmeted Turtle Steering Committee.
Tags: Academic Journalism, The Conversation, The Conversation Academic News
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