The first giant gecko found on the New Zealand mainland for almost 100 years has been killed in a mouse trap at Maungatautari.

The Duvaucel's gecko was found in the trap last month, and while dead, its discovery has led to hopes among Maungatautari staff and supporters that more of the rare species are living on the mountain.

Up until it was discovered at Maungatautari, the Duvaucel's gecko could only be found on predator-free offshore islands.

Maungatautari ecologist Chris Smuts-Kennedy said the dead gecko was "in the size range for an adult male".

The Duvaucel's can grow up to 30cm long, "weigh as much as a blackbird", and live for more than 50 years.

Mr Smuts-Kennedy said the trap had been laid as part of routine pest control, and while it was a cruel irony the gecko was dead, it indicated a strong possibility of a population of the species being on the inland island sanctuary.

"The most likely scenario is that it represents a surviving population, and this is a species which has been thought to be extinct on the mainland for probably close to a century.

"If he's a Maungatautari born-and-bred animal, it's very unlikely he's the last one.

"It's one of New Zealand's rare species. The last known mainland record (of the species) was about the 1920s in the Thames area."

Maungatautari staff and volunteers hoped to survey the mountain for more of the geckos, although increasingly cold weather could hamper that. A special nocturnal spotlighting technique would be used.

Mr Smuts-Kennedy said the Duvaucel's was prone to being hunted by ship rats, but was a feisty critter who would use its teeth and claws to defend itself.

They will feed on insects, "and even their own young, if they get the opportunity", he said.

- © Fairfax NZ News