Weta species hits critical

A LOCAL weta species is one step away from extinction, making the work of an Ōtorohanga breeding programme more important than ever.

Recently, the Department of Conservation released a report detailing several insects that had their level of endangerment reassessed, with the Mahoenui giant weta being one of three species determined to be nationally critical.

Previously, the Mahoenui species had been classified as at risk: recovering, but threats to its four populations led researchers to increase the risk level.

The report authors said the natural population at Mahoenui Giant Weta Scientific Reserve, though stable in the first seven years of monitoring from 2004, had declined significantly in the past decade.

One of the reasons given by the authors for the weta’s declining population was reducing protection from the lifting gorse canopy.

Native vegetation growing in its place did not provide as much protection for the weta against mammalian predators.

DOC’s Maniapoto district manager Graham Kimber said the aging gorse was not being purposely removed, but it was gradually reducing as the native vegetation regenerated.

In an unusual twist, DOC was attempting to sustain the presence of the gorse, he said.

“For more than 20 years, we have been maintaining a reserve of gorse because it protects a threatened species.

“However, with the gorse slowly decreasing we have new measures in place to protect the weta.”

Those included regular predator and pest control with trapping and bait stations inside the reserve.

Building a predator-proof fence or creating new populations at different locations are possibilities being considered.

“Our long-term goal for Mahoenui is for a reserve that is predator-free and as much as possible replicates the original habitat for the species,” Graham said.

The report found three other populations created through translocation were either not fully established or considered to be at risk from predators.

Graham said the reclassification was not a death sentence for the weta species.
“But it does identify Mahoenui giant weta as in trouble and needing more dedicated support and protection than in the past to survive.

“We are determined to ensure we do not lose this taonga species.”

A few shreds of hope remain for the Mahoenui giant weta – one which lies inside the boundaries of Ōtorohanga Kiwi House and Native Bird Park.

Almost two years ago, the kiwi house, in combination with DOC and contracted ecologists, rehomed 12 weta from Mahoenui Giant Weta Scenic Reserve to form the basis of a breed-for-release programme.

Graham described the kiwi house’s investment in supporting the Mahoenui giant weta through the development of captive husbandry and breeding techniques as a vital tool in protecting the weta.

“We are impressed by the kiwi house’s contribution and continue to work closely with them.

“They’re learning as they go with the Mahoenui giant weta, and sharing what they discover and develop.

“The long-term plan is for the kiwi house to perfect captive breeding for this species.”

The programme aimed to breed 3000 of the weta species to be released to Maungatautari Sanctuary Mountain in efforts to aid the then-at risk but recovering population.

Kiwi house general manager Jo Russell said she didn’t know anymore how significant that figure would be in improving the weta’s endangerment status, but the reclassification had lit a spark under the breeding programme.

“For us it has always been high stakes. Every weta counts from our point of view.

“But I guess now what we’re seeing is an even greater need to move this programme swiftly through the stages.”

Only one female was left at the kiwi house this month with all others reaching the end of their natural lifespan, Jo said.

In May last year, King Country News reported one female was entertaining four males.

Being down to one surviving weta did not signal the end of efforts to save the species, Jo said, and the fact there was one left was actually a good sign.

By this date everyone involved expected all weta to have exceeded their lifespan.

Jo said the team in charge of the weta programme was monitoring 19 egg fields, each containing an unknown number of eggs laid by the females captured in 2021.
But there was no way of knowing if the eggs were fertilised until they hatched.

The breeding programme was being developed based on the knowledge and experience of Auckland Zoo, Butterfly Creek and field researchers, Jo said.

“This sort of conservation work doesn’t happen in isolation.

“It takes that that incredible level of collaboration and passion to ensure our taonga species are here for our grandchildren and great grandchildren.”

Because of that knowledgebase, Jo said the team was reasonably confident that they had good parameters on how to raise the weta from nymphs.

“The last piece of the puzzle really is how we hatch the eggs. From there, there’s fairly good husbandry already developed around how we support them through the stages of their development, and until they’re adults.

“We look to release them when they’re about seven months old, roughly, and so we’ve just got to crack that last piece of the puzzle and then hopefully we can see some positive returns for this species.”

Jo said it was with the support of the community and some specific organisations that the kiwi house could aid the survival of the Mahoenui giant weta.

Ōtorohanga District Council as stakeholders allowed the kiwi house to build the weta breeding facility earlier than planned in the redevelopment project, she said.

“We’re incredibly grateful not just to the district council alone; the whole community.”

Several conservation stakeholders were involved in supporting the long-term survival of the Mahoenui giant weta, including Mōkau ki Runga as kaitiaki for the weta, Maungatautari as a translocation site and Manaaki Whenua Landcare Research.

More weta are expected to be translocated to the kiwi house in the future, but rigorous discussions will be held with stakeholders first.