A University of Melbourne researcher has spent nearly a year scouring Litchfield National Park in the Northern Territory for northern quolls without a single sighting, and now believes the endangered marsupial may be locally extinct in the region.
PhD student Ryan Sauermann said the project began with hopes of establishing a captive breeding and rewilding colony, but had shifted into a detection exercise.
"We started out hoping to set up a captive breeding and rewilding colony, given how quickly their populations have declined," he said. "Now the PhD project has turned more into [looking at] where are they, are they even still around, and if not, why?"
NT Parks and Wildlife senior ranger Darius Nasir, who has been assisting with the research, said the nocturnal quolls were once abundant in the area.
"Around 2009, 2010, I used to see them all the time around my house ... my dogs would be going off and it'd be quolls, quite abundant quolls back then," he said. He estimated it had been four or five years since he last saw one.
Mr Sauermann said the spread of cane toads was largely to blame.
"As the cane toad front moves through, we're losing 85 to 95 per cent [of the northern quoll population]," he said.
Changes to fire management and feral predators, particularly cats, were also major threats. Northern quolls are listed as endangered nationally and critically endangered in the Northern Territory.
The decline is not confined to the Top End. Earlier this year, research in Queensland confirmed spotted-tail and northern quolls were functionally extinct across large parts of the state.
Mr Sauermann has set up more than 30 wildlife-tracking cameras throughout the national park in hopes of capturing footage of the species.