Wellington's Miramar Peninsula was meant to be the first predator free-urban area 18 months ago, but trappers are struggling to eliminate the final rats.
So far, $2.5 million dollars has been spent and 60 people employed on the operation.
Stoats and weasels are gone but ship rats - the most common type of rat – remain.
"They can live in tiny, tiny areas, far smaller than we originally thought, so we're having to turn the screws tighter and tighter and find where these things are," James Willcocks of Predator Free Wellington told 1 NEWS.
Recently, just six rats were found across 1000 traps.
The pests like to live in trees, making them difficult to eradicate.
“This work is really, really, hard and it's been called our moon shot, we can tell you having been out here the work is a lot harder than we would have anticipated,” Willcocks said.
So if it's tough in Mirama, what hope is there for the rest of the country?
“Predator free 2050 is an achievable goal. We know that the current tools and technologies available right now may not be adequate to accomplish the goal, but we've prepared for that inevitability,” Auckland University ecologist Zachary Carter said.
Thanks to the efforts on Miramar, Peninsula birdlife is up by a third and the number of weta has tripled.