Rat prints have been found on a predator-free island sanctuary for endangered birds off Stewart Island.
The Department of Conservation confirmed staff found signs of a rat in two areas on Ulva Island, located in Paterson Inlet.
The eco-tourism destination is home to the South Island saddleback, rifleman, yellowhead, Steward Island robin and the Stewart Island brown kiwi.
Rat prints were first detected during a routine trap check, near the Post Office Bay houses.
"On average, one rat per year manages to reach Ulva. It's not surprising, considering it's very close to Stewart Island," DOC Ranger Jennifer Ross said.
DOC have now activated all traps on the island and have increased checks from once to twice weekly.
Rats were removed from the island in 1995.