C02-powered pest trap impresses officials

Declaring the "battle for our birds" this year, the Government announced it would increase pest control in 35 forests to protect 12 native species, mainly by using 1080 poison. Photo / Thinkstock

Officials have been impressed at new results of a C02-powered pest trap, which has matched 1080 poison in wiping out entire rat populations.

The Department of Conservation has described the Kiwi-built A24 trap as a "significant step" toward better trapping solutions, as the so-called battle for our birds ramps up in forests this year.

The self-resetting traps, already used by DOC in sites around the country, were recently trialled Onepu in Te Urewera and Boundary Stream northwest of Napier, completely annihilating surrounding rat populations.

The unprecedented results contrasted with results at nearby comparison sites, where rat populations continued to thrive.

"The ultimate goal was to get to zero, so now we are achieving what 1080 achieves, but with a trap," said Stu Barr of Goodnature, the Wellington-based company that developed the traps.

Powered by compressed C02 canisters, the traps reset themselves after striking and can kill up to 24 rats before the canisters need replacing.

Kevin O'Connor, deputy director general of DOC's Conservation Services Group, described the trials as "very promising".

"It is a significant step towards having a better and more effective trapping option for predator control in New Zealand."

Mr Barr said while 1080 was an effective knock-down measure over large areas, the traps could be used more intensively in areas to protect critically endangered habitats, preventing rat populations from regrouping.

"1080 costs about $40 per ha to deploy, while these traps cost about three times that. But the difference is you're getting sustained control over time."

This autumn, a one in 10 to 15 year large beech mast was expected to drop around a million tonnes of seed, fuelling a plague of an additional 30 million rats and tens of thousands of stoats.

Declaring the "battle for our birds" this year - a $21 million project aiming to protect 25 million native birds each year over the next five years - the Government announced it would increase pest control in 35 forests to protect 12 native species, mainly by using 1080 poison.

How it works:

1. The rat is attracted into the A24 trap by the potent long-life rodent lure.

2. As the rat brushes past the very sensitive leaf-trigger the trap is set into action.

3. A piston strikes the rats head - killing it instantly - then retracts on a light spring.

4. The dead rat falls to the ground and the trap automatically resets itself ready for the next pest to arrive.