The Department of Conservation now believes Kapiti Island is free of stoats.
A trapping and monitoring campaign costing more than $600,000 was launched after a stoat was spotted on the island in 2010.
The latest results from the monitoring programme, which used stoat-detection dogs and tracking tunnels, suggest the campaign successfully eradicated the family of stoats on Kapiti Island, DOC Kapiti area manager Rob Stone said.
''All of the results from our monitoring to date have not found no stoats - that doesn't mean there isn't any.
''But we're feeling hopeful it is [stoat free].''
Mr Stone said in two years, three stoats were caught in the roughly 260 traps across Kapiti Island, and lab testing showed they were a family - a mother, son and daughter.
''It would suggest a pregnant female got there and had a litter.
''Litters are normally a lot bigger than two so we wondered what happened to the others.''
Stoats were dangerous predators of native birds, especially for those species that lived or nested on or near the ground, he said.
''They're quite voracious killers, and they also reproduce quickly, so they can respond to an abundance food source quite quickly as well.''
While optimistic about Kapiti once again being stoat free, DoC would maintain a vigilant watch for the pest species.
Mr Stone said the extensive monitoring programmes would continue, and traps for stoats would be permanently used on the island.
''Kapiti is such a precious nature reserve.
''We now know stoats can get there, and keeping it pest free is a top priority for us.''
Kapiti Island was eradicated of introduced mammals in 1996, and was a wildlife sanctuary for some of the country's rarest native birds including the little spotted kiwi, stitchbird and takahe.
- © Fairfax NZ News
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