Environmental DNA (eDNA) has helped rediscover the Irwin’s tortoise in the lower Burdekin River for the first time in more than 25 years. PHOTO: Lorelle McShane
Photo: Lorelle McShane/James Cook University
A team of researchers from Australia’s James Cook University confirmed the presence of Irwin’s tortoise in rivers in that country, an animal that had not been formally recorded in the area for more than 25 years. The research has just been published in the journal BMC Ecology and Evolution. How they did it?
The scientists used environmental DNA, a technique that uses the genetic material that organisms release and that remains floating in the water of oceans, rivers or lakes. They collected five replicate water samples at 37 sites along the catchments and tributaries of Australia’s Burdekin, Bowen and Broken rivers.
“Until this rediscovery we had no formal records to prove that Irwin’s tortoise still lived in the lower Burdekin River,” said Professor Damien Burrows, director of the Center for Tropical Waters and Aquatic Ecosystems Research. The information collected will assist the state government in evaluating a proposal to build a dam on the upper reaches of the Broken River.
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Irwin’s tortoise, Elseya irwini, belongs to a unique group of freshwater turtles endemic to Australia capable of breathing through the cloaca (their bottom). The development of water resources, the increased presence of saltwater crocodiles, and their cryptic behavior have made sampling for Irwin’s tortoise in parts of its range problematic.
“Previously, it has been very difficult to sample Irwin’s tortoise because they only live in places where there are crocodiles or in upland tributaries that are very difficult to access,” Professor Burrows explains in a statement. “They also don’t fall easily into traps and the water they live in at Burdekin is not clear so you can’t set up underwater cameras to see them.”
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Although the samples do not allow scientists to know about the demographics of this population, the finding could indicate that adult Irwin’s tortoises can survive in more turbid water conditions. “This rediscovery has now challenged the previous hypothesis that the species could not survive in these conditions,” the scientists said. Approximately 50% of freshwater turtles worldwide are threatened by habitat loss, rural development, and altered water flows.