A detection dog has caught a rat on the usually predator-free Motuihe Island in the Hauraki Gulf.
A Department of Conservation ranger discovered rat prints in a tracking station on the northern end of the island on Monday.
DoC later discovered evidence of rats in five more trackingstations spread across the 179ha island.
But Jack, a trained terrier brought up from the Coromandel Peninsula yesterday, sniffed his way to a female Norway rat soon after his arrival on the island.
DoC biodiversity manager Phil Brown said it was great to catch the rat so quickly.
"Everyone has a responsibility to check their boats and gear before leaving the mainland, so we don't end up with this type of situation."
DoC plans to release the native parrot kakariki on Motuihe, which had been free of rats and mice since1996.
It became pest free in 2004 when 20,000 rabbits were eradicated.
The island is being ecologically restored with the establishment of other native bird species, such as saddlebacks which Mr Brown said had doubled in numbers since theywere introduced a couple of yearsago.
Rats on the island could eat eggs and attack shore nesting birds, including the protected variable oyster catcher and the critically endangered New Zealand dotterel.
DoC will continue checking the island for more rats and use another dog on Sunday.
About 250 rat traps baited with peanut butter have been laid out.
DoC will also be checking neighbouring pest-free islands such as Motuora, Rakino, Browns Island and Hauturu/Little Barrier.
They eventually plan to eradicate all pests from neighbouring Rangitoto and Motutapu, creating the largest pest-free habitat (over 3800ha) in the Hauraki Gulf Marine Park.
