Rangers are celebrating the "significant achievement" of eradicating mice from a Great Barrier Reef island off the central Queensland coast.
The common house mouse is no longer infesting North West Island thanks to a helicopter, ink pads in tunnels, a few tubs of peanut butter and a massive two-year team effort.
The pristine coral cay, 75 kilometres north-east of Gladstone, is the largest breeding island for wedge-tailed shearwaters and black noddies on Australia's east coast.
But Queensland Parks and Wildlife ranger Damon Shearer said introduced pests had turned the island into an all-you-can-eat seabird buffet.
"Mice impact the seabirds by direct predation on eggs and chicks and can cause a real reduction in the reproduction of the bird species at a population level," Mr Shearer said.
"During 2016 to 2019 we did surveys and noticed a 40 per cent drop in the shearwater population, which is quite significant."
Mr Shearer said the birds had been attacked by feral cats until they were eradicated from the island in the 1990s – leaving mice to flourish.
Beyond diminishing bird populations and destroying native vegetation, the invasive pest caused havoc for visitors.
"North West is our most popular island in the entire Barrier Reef for campers," Mr Shearer said.
"Mice were getting into peoples' camps, into peoples' tents and just being a real nuisance.
"They're a concern for health as well, they carry various diseases."
The eradication process
The traditional owners of the region are the Port Curtis and Coral Coast Trust, made up of the Bailai, Gooreng Gooreng, Gurang and Taribilang people.
Queensland Parks and Wildlife Service rangers and Gidarjil Land and Sea Country rangers began the eradication program in June 2020, when mice had reached plague levels.
"We did some tunnel tracking and at 119 of the 120 trap sites we detected mice, so it was fairly infested," Mr Shearer said.
The Black Trakka tunnels used in the program were not actually traps.
Peanut butter was placed in the centre of the tunnel and mice walked along an ink pad to reach it, leaving footprints and making it easy to see if mice were there.
The meticulous monitoring was repeated five times throughout the project after three rounds of aerial baiting.
"We used a helicopter to spread baits from a chopper across the entire island," Mr Shearer said.
There have been "zero detections of mice" since.
"An eradication program on an island isn't considered a success until two years of surveys find no signs of the target animal," Mr Shearer said.
The final survey was completed this month.
"It was quite exciting to get to the end and see the last ink pads free of mice," he said.
Early signs of improvement
Gooreng Gooreng man Jacob Bulow, who is also a senior Gidarjil ranger, said he was proud of his team's contribution.
"When they did the original chopper drops we had our boys doing all the groundwork, making sure the pellets didn't go in the wrong places," he said.
Mr Bulow said the wildlife had "really chirped up" since mice were removed.
"The birdlife will flourish a lot more and the campers will be happier — it's just going to be an overall healthier situation for the island," he said.
But he said other pests were causing harm on offshore islands.
"The seagulls, they're taking over," he said.
"They always attack the other birds and they form a little army.
"You look up the beach and there's a cloud of seagulls, waiting to attack whatever they can and they're getting more and more."
Hope in battle against pests
Griffith University ecologist Guy Castley said introduced pests on islands were "quite a big problem globally".
"When you compare an island to an equivalent area on the mainland, islands support way more biodiversity," Associate Professor Castley said.
He said reptiles, seabirds, shorebirds, terrestrial birds and native mammal fauna like wallabies were "more prone to extinction" from introduced pests on islands.
Associate Professor Castley said pests often hitched a ride onto islands with humans.
"Once those species are there, their biology makes them really successful in colonising those islands because they have a high reproductive rate, they're omnivores, they feed on just about anything," he said.
He said the achievement on North West Island was "immense" and provided hope.
"Every success that we can show where we've eradicated pests from islands is a win for conservation, because of the species that will benefit from the eradication," he said.
Queensland Parks and Wildlife Service is urging the public to check boats, clothing, footwear and camping gear are pest free before visiting islands.
