DNA detection to alert public to crocodiles lurking in the vicinity

Scientists can detect whether a crocodile is present in a waterway through DNA particles. They hope it can help prevent attacks.

Daniel Guymer and Peta Hill analyse a water sample taken from a saltwater crocodile enclosure. Picture: Brendan Radke

Scientists are developing a method to detect the DNA of saltwater crocodiles within a waterway in the hope it will help authorities to reveal whether the stealthy reptiles are lurking nearby.

The breakthrough could be used to enhance public safety and alert water users of dangers present in popular swimming holes in northern Australia, where there is ongoing debate about managing resurgent crocodile populations and human interactions.

It comes after the recent death of a 12-year-old Northern Territory girl, who was killed by a crocodile while swimming in a creek with her family, and the recent discovery of a large crocodile at a popular swimming spot near Townsville.

Researchers Peta Hill and Elise Furlan from the University of Canberra have come up with a technique to detect mitochon­drial DNA from shed skin cells, faeces or urine.

“We conducted trials to detect DNA in water samples collected from crocodile holding ponds at the DESI facility in Cairns, and compared them with control samples of water,” Dr Hill said.

Wildlife officers remove a 4m saltwater crocodile at Port Hinchinbrook in Cardwell. Picture: Cameron Bates

“We will use these trials to confirm estuarine crocodiles having been present in those ponds.”

Similar research has been undertaken by scientists at Charles Darwin University in the Northern Territory who were able to detect DNA from the crocodiles in an aquarium within an hour of its entry and for 72 hours after it had been removed.

They were also able to differentiate between the DNA of saltwater and freshwater crocodiles.

Queensland’s Department of Environment, Science and Innovation has supported the University of Canberra project and hope it will give them another tool to manage crocodile populations and prevent future tragedies.

“Occasionally, wildlife officers respond to a crocodile sighting report and our conventional methods such as land or vessel-based surveys don’t confirm the presence of a crocodile,” DESI program co-ordinator Simon Booth said.

“This program is in the preliminary phase but if t (it) is successful, wildlife officers could take water samples to detect crocodiles in waterways that are hard to access, or areas the public use regularly such as swimming holes. We’re hoping the research project will allow us to reliably test water samples to detect the presence of crocodiles.”

Crocodiles at the department’s facility in Cairns are being used in ongoing studies to determine how long a crocodile needs to be present in a body of water before it can be detected and how long its DNA is able to be detected for once it has moved on.

“Once we understand the captive dynamic, we will undertake sampling in rivers and water bodies around north Queensland, known to hold estuarine crocodiles,” Mr Booth said.