Rat tracks on one of Auckland's island sanctuaries have sparked a major hunt.
Tiritiri Matangi has been predator free since 1993, but the alarm was raised when footprints were spotted last week.
You'd usually go there to escape the rat race, but on Tiritiri Matangi on Friday, the race is on to find a rat.
Footprints were found in a detection tunnel last week and that's a major problem.
"We've got a network of these tracking cards out to detect rodents and we bait them with peanut butter," said DoC supervisor David Wilson. "There's sticky ink in the middle.
"So the animals, like the rat's done, leave footprints on the way out and we can identify what's been on the card."
The Department of Conservation has scrambled a team to the island to set traps and monitor tunnels, and there's a real urgency about finding the rat.
"It's important we get in top of it straight away, before it escalates into something more difficult to manage," said DoC operations manager Keith Gell.
There's a team of 16 DoC workers and specialists are on the hunt. They've set 55 traps and more than 300 tracking tunnels.
The island sanctuary is home to endangered birds like takahē and other defenceless species.
"The worst-case scenario, if the rat was a female, if the rat was pregnant, all of a sudden, we're dealing with 'rats' as oppose to a singular," said Mr Gell.
It's a reminder for boaties and visitors to be extra vigilant about stowaways.
"We do those checks on the wharf here," said James Bailey from 360 Discovery Cruises. "Most people are aware of the status of the island - the pest-free status - so they're pretty well prepared."
DoC workers are confident they're closing in and hope to catch the unwelcome intruder within the month.