Possum control operation to target southern Rimutaka

Date 31 March 2016

An aerial possum control operation is planned for the southern Rimutaka Ranges this spring as part of the drive towards eventual eradication of bovine tuberculosis from New Zealand.

The TBfree operation proposed for September is supported by the Department of Conservation, and community consultation and public meetings have been scheduled to determine the exact size of the control area, water supplies and exclusion zones.

The proposed area includes the East Harbour Regional Park where the Eastbourne Forest Rangers have been performing effective possum control since 1933, and the Orongorongo Valley, where community groups such as the Moa Conservation Trust have contributed hugely to supporting biodiversity with voluntary possum control. The wider southern Rimutaka area has not been treated with an aerial operation before.

The farming region of South Wairarapa on the eastern fringe of the southern Rimutaka has a documented history of TB in cattle herds going back more than 30 years, and the link with tuberculous wildlife is well established. Possums are the main ‘vector’ or transmitter of TB among cattle. Possum surveys in 2008 by the Animal Health Board (now OSPRI) and more recently by Landcare Research found TB-infected possums in the forest park.

Primary sector service organisation OSPRI, which manages the TBfree programme, aims to eradicate bovine tuberculosis from New Zealand by 2055, with freedom from TB in livestock by 2026 and in wildlife by 2040. To eradicate bovine TB, possum numbers need to be kept extremely low – one to two possums in every 10 hectares.

While the control of TB is the focus of OSPRI, DOC says the conservation values of the area, including lowland forest and threatened bird species make the southern Rimutaka an important target area for possum control. The unique and popular recreational area is used extensively by walkers, runners, trampers and hunters and the many owners of the park’s network of historic huts.

DOC Kapiti-Wellington Operations Manager Rob Stone says the operation will not only knock down the possum population but also significantly reduce rat and stoat numbers and this is good news for our native plants and animals. Among the species to benefit are rata, kiwi, kakariki and NZ falcon.

Possums, along with other introduced mammals such as stoats, ferrets and rats, impact dramatically on the habitat that supports these native birds.

Large rata trees with their distinctive show of crimson flowers dominate the forest canopy in the Orongorongo Valley. “These ancient trees are seriously threatened by possums which show strong preferences for browsing this species,” says Rob Stone.

Likewise, the birdlife needs all the help it can get. Kiwi have been re-introduced to Rimutaka Forest Park, but protecting them against mustelids requires constant control work local community conservation groups. The operation will add value to this important work.
Kakariki, the native yellow-crowned parakeet are hole nesters which are hanging on in the forest canopy, in Rimutaka Forest Park but they are very vulnerable to predation by stoats, rats and possums.

The North Island robin was extinct in the area until the Greater Wellington Regional Council re-introduced them to East Harbour Regional Park. Their ground feeding habits make them popular with trampers but because of that, they are also very vulnerable to rats and stoats.
The region has large tracts of native and pine forest with some scrub and native bush in gullies – habitat for native wildlife that will benefit from pest control.

The rugged terrain is notoriously difficult country in which to trap possums. Advanced GPS navigational equipment will be used to ensure the pellets of the toxin sodium fluoroacetate (1080) are accurately placed and identified exclusion zones are avoided.

OSPRI’s chief operating officer, Matthew Hall, says aerial control is the best method to achieve fast and accurate knockdown of pest populations – particularly when trying to suppress bovine TB – while on-going ground-based control has benefits for protecting kiwi and other native species.

The effectiveness of the operation will be monitored with a survey of wild pigs in the area. The absence of bovine tuberculosis in captured pigs will guide the next steps in the programme towards the eventual eradication of bovine TB.

You can find further details about the planned operation in the TBfree factsheet.



Oliver Bates
Corporate Communications Manager
(04) 474 7105

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