After a $25 million operation, Macquarie Island in the subantarctic is now free of environmentally damaging pests like rabbits, rats and mice. Finn is one of the dogs that helped confirm the pest-free status, as Keiren McLeonard writes.

It's a dogs life.

Finn has spent two years with the run of Macquarie Island, 1500 kilometres south-east of Tasmania in the subantarctic. But while he has enjoyed hundreds of days on the hunt, his super-sensitive nose and inquisitive nature have failed to detect any rabbits lurking in the environment.

There's an enormous amount of training that goes into the dogs. So if he didn't find any, there were none to be found. Karen Andrew, dog handler on Macquarie Island

That might be frustrating for Finn, but for his handler, Karen Andrew, and the pest eradication teams that have been stationed in this rugged and beautiful patch of earth, it is good news.

There's almost no part of Australia's territory that has escaped the destruction of invasive species, but on Macquarie Island the curse of invasive pests appears to have been vanquished.

Keith Springer is the Macquarie Island pest eradication project manager for the Tasmania Parks and Wildlife Service. He has been overseeing a $25 million pest eradication effort that's been running for several years on the island.

Can he finally claim 'mission accomplished'?

'We believe so, yes,' he says.

'We've had teams on the island for the last three years, searching intensively for any sign of remaining rabbits, rats or mice and for more than two years we've not found any sign of them.'

'Given the coverage we've been able to get on the island we're pretty confident that means they are gone.'

There were believed to be around 150,000 rabbits on Macquarie Island—which is listed as a 13,000-hectare World Heritage site—and the nearest estimate of ship rats and mice was 'lots', according to Mr Springer.

He says the mice came first with ship stores taken in by sealers in the early 1800s. Rats came either with ship stores or from one of the shipwrecks near the island.

Rabbits arrived with island workers in 1879, when the crews wanted a new food source. The rabbits soon found their own food supply and the environmental damage started.

'Rodents were chomping on eggs and chicks of burrow nesting seabirds. Rabbits devegetated the island ... that was resulting in landslides,' says Mr Springer.

The eradication program involved three years of planning and then, in 2011, four helicopters spreading rodent bait across the island, which rabbits also consumed.

Then hunting teams of 12 were brought in to put pressure on rabbit survivors over the last two years.

Karen Andrew, one of the dog handlers, has this week arrived back in Tasmania after two years on Macquarie Island, in time to hear the declaration that the island is free of the target pests.

She's confident they are gone, having spent six days a week for two years with her dogs, including Finn, searching for any remaining pests.

'I didn't see any the entire time I was there,' she says.

'There's an enormous amount of training that goes into the dogs. They are really enthusiastic and switched on by hunting rabbits. So if he didn't find any, there were none to be found.'

It's a job, she says, where it was important to be able to enjoy your own company, along with the dogs.

'I spent a lot of time with Finn. I saw more of the dogs than anyone else,' she says.

'I stayed in field huts ... some put in especially for the project. They are small, compact but with heaters, food, cooking equipment. Every block had a couple to choose from. You could share or be by yourself with your dog.'

The eradication efforts have already seen environmental and wildlife changes on Macquarie Island, with some of the bird species, like Blue Petrels that were eaten off the island by rats, back and breeding.

New tussock cover for the seabird chicks that are fledging is returning, protecting them from predator birds.

While full environmental recovery will take many decades, there have been three seasons of regrowth.

Now Mr Springer says attention is turning to other islands with similar pest problems which might benefit from the lessons learned from Macquarie Island's eradication program.

'Lord Howe has been following what we are doing ... in South Africa they are taking notice because there are islands with mice. And South Georgia, in the south Atlantic Ocean, has their program under way now.'