Case for aerial 1080 sound

A young Catlins mohua looks out at the world from the shelter of a punga on its first day out of the nest in January 2009. Its nest was successfully protected from a rat plague by a 1080 poison operation the previous winter. Photo by Tristan Rawlence.

• Still the most effective method of rabbit control

In Otago, the Department of Conservation's use of aerial 1080 is focused mainly on protection of endangered bird species in two beech forest systems - the Dart Valley and the Catlins Forest. 1080 is used in these areas during beech mast (seeding) years every two to four years, when rat and stoat numbers spike.

Normally not very productive, beech forests create a wave of exploding mouse, rat and stoat numbers when they mast.

This is a food-driven process, and as beech seed is eaten up or germinates, predators are forced to switch to hole-nesting birds.

Aerial 1080 provides a quick and effective knockdown of predators over several thousand hectares before that occurs, ensuring the survival of mohua, in particular.

It has produced better, faster results than bait stations or trapping in mast years, when rats appear to be more focused on natural food and bait than on foreign objects like bait stations and traps.

These areas have also been trapped and ground poisoned during non-mast years to control predators. As our learning evolves, however, we are finding that pest control in beech forest is dictated by interactions between beech seed, the nesting characteristics of the native species we are managing, predator species and their levels of abundance and the timing of the predator spikes in relation to nesting.

We are finding that ground control is largely unnecessary in mohua habitat in non-mast years.

The low food supply keeps rat and stoat numbers low enough to have no effect on mohua.

But continual ground control of stoats is required for blue duck, while kaka require stoat and possum control soon after they begin breeding, which is initiated by beech flowering.

Similar interactions between other endangered bird species, predators and habitats dictate the type and the timing of pest control.

The size and accessibility of the management area is also important.

So, too, is the need for buffer zones around it, and the level of available funding.

The choice of pest control is made by Doc staff.

They review all available options before seeking approval.

Thanks to Landcare Research, we are now looking at the possibility of using as little as a cupful of aerially applied 1080 bait per hectare (two rugby fields), which is less bait than is used in bait stations.

Thanks to good science, a leap in technology and good old Kiwi ingenuity, it looks possible.

It is a result of the same can-do attitude that makes New Zealand a world leader in conservation.

With regard to rabbit control, the department uses either 1080 carrot or pindone carrots for primary (knock-down) rabbit control, and fumigation, night shooting and some trapping for secondary control. Rabbit fencing is also used to avoid conflict with neighbours, as well as to provide better co-ordination of rabbit control with neighbours.

Most 1080 and pindone operations are ground-based, as the areas involved are relatively small.

The use of 1080 is not a money-go-round.

It simply works well in the hands of good operators, and it is cost-effective for large-scale pest control.

Research continues for new toxins and tools that may replace 1080.

The big question is whether aerial delivery of any toxin, irrespective of its makeup, its sowing rate or its benefits, will be acceptable to some people.

For more information about 1080, we recommend that readers visit the recently created website www.1080facts.co.nz

Bruce Kyle is technical support officer for Doc Otago.