Crocodile 'fingerprints' may reveal Australia's deadly, hidden predators

Australia has a crocodile problem. In the last two decades, attacks have risen sharply after the population exploded. Along with safety messaging, government officials are increasing the number of permitted crocodile kills, but experts say the move isn't likely to work given how mobile crocodiles are — kill one, and another will immediately move into its territory.

But a new, stealthy way of preventing attacks may be on the horizon. The tool involves using the genetic fingerprints of crocodiles to identify areas where these predators are present. By harnessing environmental DNA (eDNA), wildlife officials could test waterways and warn swimmers, boaters and campers to avoid areas where crocodiles are, or have recently been.

The croc problem is partly the result of one of conservation's greatest success stories. In the early 20th century, thanks to overhunting, the Australian crocodile population plummeted to around 3,000. After protections were introduced in the 1970s, the population surged, and now an estimated 100,000 live in waterways across the country.

Because of this rise, both crocodile attacks and retaliatory attacks by humans are increasing. In the latest incident, on Aug. 3, 40-year-old David Hogbin fell into the Annan River in Queensland and was killed by a 16-foot-long (5 meters) saltwater crocodile (Crocodylus porosus), which was later killed by wildlife officials. And in 2023, a 13-foot (4 m) crocodile was found beheaded on a beach. A few months later, a 40-year-old female croc was also found dead, having been butchered with just her head and spine remaining.

Related: 'Eyes coming straight for me': Huge crocodile launches itself into boat with jaws wide open in strange attack

One reason it's hard for people to avoid croc attacks is that they are some of the world's ultimate ambush predators. They can sit completely still underwater for up to eight hours, waiting for unsuspecting prey to pass by before they strike. From the surface, the water may seem croc-free, but people should "assume crocodiles are present in all waterways," according to advice from the Northern Territory Government.

So researchers are developing tests that will show where crocodiles are — without ever needing to see them.