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Detecting Wetas

Teetering on the side of a steep rock face high above a South Island stream brought rewards for Victoria University weta hunters, with the rediscovery of a giant weta previously thought to be extinct. It was an outcome that delighted Victoria biologist Dr George Gibbs, leader of the small party who had been searching for the Mt Somers giant weta.

"It was a bit like the rediscovery of the takahe," he says. "It was particularly pleasing because we hadn't been very optimistic about finding them, and because our scientific detective work turned up trumps."

Discovering new giant weta populations has become a regular occurrence for Gibbs -- he found two others in his South Island searches this summer. But the Mt Somers weta, at an inland Canterbury location near the Mt Hutt skifield, was something special.

The hunt for this beast began when Gibbs examined the sole known example of the insect, a faded brown individual in the Mt Albert Research Centre collection in Auckland. The note with the specimen said it had been discovered by V. Hunt in 1957. Inquiries led Gibbs to telephone Britain to speak to Val Hunt, who recalled finding the specimen in a beech forest on the southern side of Mt Somers, about 600 metres above sea level.

The initial four-hour night search made by Gibbs and his team did not go well.

"It was cold and wet -- there was fresh snow on the tops -- and it was a pretty miserable experience. And we didn't see any sign of a weta."

Fortunately Gibbs had another lead to follow. He had studied the Kaikoura giant weta, discovered in 1988, and suspected it was the same as the Mt Somers specimen although the colours were different and the two habitats were far apart. The Kaikoura weta lives on high rocky faces, not in forest, so next day the team moved around to the bluffs above the river on the western side of Mt Somers, covering some precarious ground without ropes.

"About 4.30pm Tom Davies [keen rock climber and former Victoria technician] let out a yell. He'd seen the back of the insect deep in a crevice. We tapped it on its nose with slivers of manuka and winkled it out."

Another half-dozen red and black wetas were found nearby. Gibbs assumes their colours are different from the Auckland specimen because it had faded, and indeed Val Hunt remembers his discovery as being red and black.

How did that weta come to be found in a forest? It could have fallen into the river and been swept down into that area, Gibbs says, which means that Val Hunt's discovery was a remarkable chance.

The weta has huge claws compared to other species, which may help it cling to vertical rock faces. It lives in crevices during the day, coming out at night to forage for leaves and small insects. Those found are sub-adults, but if they grow to the size of the Kaikoura wetas they will weigh about 16 grams when fully grown.

In a later search, Gibbs followed up a lead on the West Coast, where a tourism operator had reported seeing an unusual weta on Mt Faraday in the Paparoa Range behind Punakaiki. A helicopter ride up the mountain resulted in the discovery of some wetas living in burrows in the earth, which makes them unique among giant wetas.

"It's mainly grey, with heavily spined back legs," Gibbs says. "It lives in burrows a foot or more deep; it's more different from other wetas than we'd expected and it may be a new species. We're carrying out tests at the university to investigate."

"By and large it was an amazingly successful trip," Gibbs says. "There has already been a lot of interest from other biologists about our discoveries."