The hunt is on after a potential sighting of a stoat on Great Barrier Island, previously considered free of New Zealand's number one predator.
Auckland Council and the Department of Conservation have rallied their teams to hunt down what could be a devastating invader.
Great Barrier Island had been considered free of stoats, and its significant populations of endangered birds could be easy prey for them.
A predator detection dog from the Conservation Dogs programme was called in as soon as the potential sighting was notified.
DoC operations manager George Taylor said as stoats could move quickly it was vital to get on its trail as early as possible.
"Getting a positive indication of stoat presence from the dog is the fastest way for us to know we have a problem and to start planning how to deal with it," Taylor said.
The team had established a network of trail cameras, tracking tunnels and traps which, along with the dogs, would try to confirm and hopefully eradicate any stoats that had made their way onto Great Barrier Island.
Auckland Council incident controller Jonathan Miles said the scale of the operation was a reminder of why it was so important for visitors to the Hauraki Gulf and other offshore islands to undertake effective biosecurity inspections.
"Stoats, ferrets, weasels, plague skinks and even Argentine ants rely on people to transport them to our islands, so it's up to people to make sure they are not unwittingly introducing these devastating pests by thoroughly checking their gear and vessels before they leave the mainland," Miles said.