As cane toads continue their march across Western Australia's Kimberley region, authorities hope environmental DNA testing will be the latest tool to stop the invasive species from gaining a foothold on coastal islands.
Cane toads crossed the border from the Northern Territory into the Kimberley in 2009 with the front line moving another 50 kilometres during the past wet season, putting the pests halfway between Fitzroy Crossing and Broome.
Despite their aggressive mainland expansion, the toads have only been detected on one island off the Kimberley, which has enough fresh water to support a population.
But authorities fear that number could grow, putting at risk vital sanctuaries for animals such as northern quolls, goannas and snakes, which have traditionally been decimated by the poisonous creatures.
DNA testing hoped to detect toads before it's too late
Parks and Wildlife Service cane toad strategy program leader Clare Forward said Augustus Island and Koolan Island were among many islands off the Kimberley coast at risk of a toad invasion.
"Got quite a few people coming and going from Koolan Island and there's a good population of quolls," Ms Forward said.
"There's that nice little saltwater barrier between the coast and islands … so doesn't mean the cane toads can't get there, they just can't get there as easily.
But detecting the toads early can be tricky, so Parks is looking to environmental DNA sampling as a new weapon to be used against the pest.
The technology can detect a toad's DNA from fresh water if they have come into contact within the previous four days.
"So this is a pretty exciting development to find toads early enough to have our best chance of trying to get rid of them before they establish breeding populations," Ms Forward said.
The technology has not yet been used on islands off the Kimberley but Parks hoped to soon set up a DNA testing lab in the region.
"It's a technology that's been used across the world and we're trying to tailor it to cane toads in Western Australia," Ms Forward said.
"Unfortunately on mainland Kimberley, or on mainland Australia, we don't have the techniques to slow down or stop cane toads from spreading out.
Fears tourists could introduce toads to remote islands
As the Kimberley coast's reputation grows among tourists, Parks was now focusing on educating boaties, yachties and cruise ship passengers to identify cane toads.
"So the main way cane toads can get to islands is they can stow away on boats and in people's things if they're visiting islands," Ms Forward said.
While the pandemic has dramatically reduced the number of international cruise ships from visiting the coast there was concern once the trade started back up, it would provide more opportunities for toads to reach popular islands.
"We're trying to work with island managers on the Kimberley coast to find ways of better informing visitors," Ms Forward said.
Cane toads on one Kimberley island appear less deadly
The cane toads' devastating impact on mainland Australian species has been well documented, but the pests do not appear as lethal to native species on Adolphus Island, 35km north of Wyndham, in the Cambridge Gulf.
It remains the only island off the Kimberley where cane toads have been detected, and Ms Forward said the pest seemed to be co-existing with native fauna.
"Interestingly on Adolphus Island they haven't wiped out the animals. There's still a healthy population of quolls out there and four different species of goanna," she said.
She said data was being collected to find out why native animals managed to survive.
"Possibly to do with the fact that it's a dry island for most of the year, which would force the cane toads to hide underground where they're not going to dry out," Ms Forward said.
"And because it is an island, there are no toads that can just keep arriving."
