Stick insects found on an outcrop off Lord Howe Island have been confirmed to be the same species as those once thought to have been driven to extinction by the black ship rat.
The findings, published today in Current Biology, come just weeks after the Lord Howe Island (LHI) board voted in favour of a controversial plan to helicopter-drop poison-laced baits across the island in an attempt to wipe out introduced rodents.
The plan, passed by a six-to-one margin, will involve dropping tonnes of bait across the World Heritage island in the winter of 2018 to eradicate the black ship rat Rattus rattus and the house mouse.
The rat has driven five endemic birds and 13 invertebrates to extinction since it invaded from a beached supply ship in 1918.
Stick insects were thought to have been wiped out by 1920, until rock climber and scientist Dr David Roots photographed a recently-dead individual in 1964 while trying to scale Ball's Pyramid — a 561-metre-tall sea stack 20 kilometres offshore.
Conservationists and scientists hope to reintroduce the Lord Howe Island stick insect — Dryococelus australis — also known as the "tree lobster", to the main island.
'Unique second chance' for island ecosystem
In 2003, a captive breeding program was established, but the insects found on Ball's Pyramid looked different to the museum specimens preserved from the original Lord Howe Island population.
To confirm the insects' identity, Alexander Mikheyev and colleagues compared DNA from the Ball's Pyramid and museum specimens.
The study's results meant an introduction of the species would be more likely to succeed, said Professor Mikheyev, who is based at Okinawa Institute of Science and Technology.
"The Lord Howe Island stick insect has become emblematic of the fragility of island ecosystems," he said.
"We thought we'd lost it, but really miraculously we have a chance to bring it back to life again."
But, he said getting rid of the rats was a crucial next step.
"The rats are what drove the extinction in the first place, and as long as the rats are there, really the introduction of the Lord Howe Island stick insect...is not going to work," he said.
Poison plan a 'tried and tested method'
For the poison program to fail, only a single pregnant female rat or breeding pair need to escape the net.
Despite fierce opposition from some locals, CEO of the Lord Howe Island board Penny Holloway said she was confident the program, which was first conceived of in 2001, could work.
"The methodology has been worked out based on eradications that have taken place on other islands around the world," she said
The Lord Howe Island model is based in part on the successful eradication of rabbits and rats from Macquarie Island, located about halfway between New Zealand and Antarctica.
Forty-two tonnes of pellets laced with the anticoagulant poison brodifacoum, commonly found in over-the-counter rat baits, will be dropped by helicopter over the uninhabited regions of Lord Howe Island, and dispersed by hand around the community of roughly 300 permanent residents.
Although some locals opposed to the plan have vowed to block access to their properties, Ms Holloway said power to enter against the will of owners could be used as a last resort.
"We do have powers to enter properties, not buildings, but properties, which we can use," she said.
"At the end of the day, we do want to do it with everyone's consent and support."
The poison will be dropped in two instalments about two weeks apart, to make sure any newborn rats have time to leave the nest. Afterward, dogs will be deployed in residential areas to help catch rodents that might have been missed.
Only one chance to 'counteract damage' we've done
Endangered Lord Howe Island woodhens will be rounded up ahead of the poison drop and held in captivity by a Taronga Zoo program.
Although organisers concede that some non-target animals may eat the poison, they hope that the overall benefit will be a healthier ecosystem.
"We want to ensure that the rodents, which are very destructive and have made extinct some plants and animals and continue to threaten others, aren't able to do that anymore," said Ms Holloway.
Professor Mikheyev said bringing one species back from the brink of extinction was a sorely needed symbol of encouragement.
It's important to show that we can do something actively to counteract the damage that we have done. The Lord Howe Island stick insect is a really good emblem of that."