Operation Ark in Canterbury

What is Operation Ark?
Operation Ark is an initiative to respond to predator plagues in South Island beech forests, to prevent the extinction of orange-fronted parakeet/kakariki karaka, mohua/yellowhead and whio/blue duck. Plagues occur in years when beech trees produce vast quantities of seed. The abundant supply of high energy food that the seeds provide means rat and stoat numbers can increase rapidly with dire consequences for our native birds. Eleven sites have been selected where rats, stoats and possums will be intensively controlled with traps, toxins in bait stations and bait bags, and, possibly, aerial 1080.

Which areas have been selected in Canterbury and why?
Canterbury has two Operation Ark sites: the Hawdon Valley (Arthur’s Pass National Park) and the South Branch of the Hurunui (Lake Sumner Forest Park) (shaded areas on map). Orange-fronted parakeets and mohua are found at both sites. Orange-fronted parakeets are New Zealand’s most threatened forest bird with a total population of 100-200. They are found only in Canterbury, and only in one other valley, the Poulter (see map). Mohua are ‘nationally endangered’ and declining fast. There are 5,000 left at isolated beech forest sites on the mainland. A larger management area has been identified (see map) where orange-fronted parakeet and mohua in the Poulter Valley will be managed in the future if further resources become available.

Why is predator control necessary?
Rats, stoats and possums have a devastating impact on orange-fronted parakeet and mohua. They are particularly vulnerable because they nest in holes in trees. In 2000/01 rat and stoat plagues resulting from two consecutive beech seeding years in Canterbury caused catastrophic declines in parakeet and mohua populations. Orange-fronted parakeets may become extinct and mohua may become locally extinct if they are subjected to another predator plague.

When will predator control happen?
The timing of control will be dependent on when predator numbers increase. This happens infrequently and irregularly, and usually only when beech trees seed prolifically.

How will predators be controlled?
Ideally rats would be controlled early, before population explosions occur. The Department is proposing to control rats using the following approach:
1) If rats are caught in traps used for monitoring, trapping effort would be stepped up in rat ‘hotspots’.
2) If this fails, the trapping effort would be increased throughout both valleys.
3) If traps fail to control rats, poison baits containing anticoagulant rodenticides will be used on an alternating basis in secure bait stations or bait bags, in conjunction with trapping.
4) If trapping and using pesticides in bait stations or bait bags fails, aerial 1080 may be used.
Stoats will be trapped at both sites.
Possums will be controlled using poison baits laid in secure bait stations. If aerial 1080 is used to control rats, possums may need to be controlled with aerial 1080, or they will eat the baits sown for rats.

Will there be any adverse effects on the environment from using pesticides?
A range of measures will be taken to minimise the risk of any adverse effects on the environment and non-target species.
Using bait bags and bait stations means that:
- No poison bait will get into waterways.
- No poison bait will be in contact with the ground.
- The risk to birds and other non-target species will be very low.
The effects on the environment of sowing 1080 by helicopter are minor:
- Using green dyed cereal baits with a cinnamon lure and following strict bait quality control procedures means the risk to birds is low. Although a small number of birds may be poisoned, no adverse effects on their populations are expected. The net benefits of predator control for birds far outweigh the loss of a few individual birds.
- No baits would be dropped within 50 m of lakes, rivers or streams larger than 5m. 1080 is highly soluble and is rapidly diluted and broken down into non-toxic by-products.
- 1080 is rapidly broken down by soil micro-organisms and does not accumulate in the soil.

Why are pesticides being considered?
Trapping may not control rat numbers as rats can breed rapidly when beech seed is available on the forest floor. Pesticide operations are an effective, efficient and environmentally sound form of predator control.
When bait is regularly spaced in secure pest bait stations or bait bags, most rats and possums eat the bait. Pest specific bait stations mean the baits are secure and only the target species can access them.
1080 is relatively safe, cheap and effective. The size of the area, and the steep, rugged terrain rule out hand laying of baits. Helicopter sowing of baits using satellite navigation technology means an even coverage of bait can be achieved. It also allows the pilot to be sure of the boundaries and to exclude important areas from being sown with baits, such as hut sites, lakes and rivers. Overall, this results in higher rat kills and less risk to visitors to the parks.

How thoroughly will this operation be planned?
Before pesticides can be used a detailed assessment and consultation process is undertaken. This involves:
- Considering people’s needs and concerns.
- Consultation with the rünanga.
- Preparing an Assessment of Environmental Effects (AEE).
- Obtaining resource consent from Environment Canterbury to sow 1080 from the air.
- Seeking approval from the Medical Officer of Health (MOH consent).
- Complying with DOC’s quality management standards to obtain DOC consent.

How can I get further information?
For further information, contact the Canterbury Conservancy Office at 133 Victoria Street, P.O. Box 4715 Christchurch, ph (03) 379 9758 or fax (03) 365 1388.

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