Meaner than myxomatosis, more calculating that calicivirus, the latest weapon against Australia's exploding rabbit numbers has scored an 80 per cent strike rate near Canberra.
They're a tough bunch of people from Sydney and Melbourne and the local region who sleep in a freezing cold shearing shed and work for nothing.
An aerial picture of Scottsdale between the Monaro Highway and Murrumbidgee River looked like a bad case of chicken pox when volunteers mapped it three years ago, placing red dots on 320 warrens which harboured an estimated 2000 to 3000 rabbits.
With rugged vistas and wind-swept slopes rising 700 and 900 metres above sea level, Scottsdale has become a beacon for hardy volunteers.
Senior ecologist Sandy Gilmore, who helped acquire the 1320-hectare property six years ago under Senator Bob Brown's Bush Heritage scheme, has measured a dramatic change in local wildlife since then.
More resistant to traditional biological controls of myxomatosis and calicivirus, rabbits still infest 70 per cent of Australia, threatening native grasses, shrubs and trees.
Valleys on Scottsdale cleared of habitat for grazing and overrun by rabbits are recovering with the help of these determined and methodical volunteers who seal, gas and monitor burrows.
Groups of ground-feeding birds, including brown tree creepers, speckled warblers, diamond firetail finches and hooded robins, are thriving as native ground cover spreads.
Regional reserve manager Peter Saunders of Gundaroo said the Murrumbidgee River and steep terrain restricted some re-infestation from neighbours. The focus now was on active warrens.
''One of the most active is near the [Monaro] Highway. We counted 35 open burrows.''
Scottsdale is part of the Kosciuszko-to-Coast project, a community partnership to help landowners create connections between remnant woodlands and grasslands between Kosciuszko and Namadgi national parks and the forests of the far south coast.
Corridors enable birds and mammals to move about and breed.
''They can share their genes with animals as far away as Canberra,'' Mr Gilmore said.
Grazing has been reduced to a few cattle on the fringes to maintain firebreaks, while the shearing shed has been upgraded with a wood heater and kitchen for volunteers who come from Melbourne, Sydney and the region to spray weeds, gather and propagate seeds and enjoy the bush without the expense of buying a hobby farm.
Mr Saunders said volunteer days had been the equivalent of three full-time staff. They had built shade houses on to the shearing shed, a propagating shed and gardens.
''It is an amazing place to work. At the end of a day I like to think a tiny piece of the world is a better place. It's an amazingly positive environment to work in, it's the best job I've ever had, I don't know why they picked me.'' Camping with volunteers one winter he's seen the temperature drop to minus 10 degrees and water in his tin mug freeze.