A planned 1080 drop in South Westland has been called off as there are not enough rats.
The Battle for our Birds -- to combat a pest plague triggered by a beech forest fruiting -- involves the largest ever pest control programme over a million hectares of conservation estate, including swathes of the West Coast.
In South Westland, the Abbey Rocks and Landsborough drops are still proceeding. But DOC has postponed the Haast drop this year.
Science advisor Josh Kemp said the Haast Range was further west than the Landsborough site and the climate triggers for a mast to occur did not happen. "This operation has been postponed to another year because of the absence of rodents at higher altitudes.
"Although possum numbers are high we would prefer to control them in a mast year so that rat and stoat eruptions can be simultaneously controlled."
At the Abbey Rocks site, rat numbers were higher in the higher altitude parts of the block.
DOC scientist Graeme Elliot, said that was not surprising as it was "in the higher altitude forest with the most beech trees that we expect to see the most rats during a beech mast".
If uncontrolled, the rats, and the mice would enable a stoat plague to develop over summer. They in turn threatened hole nesting birds such as kaka and kea.
Rats in the higher altitude parts of the block were tracking at 35 per cent, rats in the lower parts 27 per cent.
That means footprints were found in 35 out of 100 tunnels set out for one night, with ink.
Mr Kemp said the Landsborough site contained a range of vulnerable plants and animals.
Rats there were currently tracking at 5 per cent, and it expected this number to grow to 17 per cent by November. Mice numbers were tracking at 26 per cent.
"This level of mice is expected to trigger a stoat plague. Stoats will also be killed after feeding on poisoned rats and mice and possums."
Anti-1080 activist Danny Lane said the Battle for our Birds was cementing opposition to poison, pointing to the more than 2000 votes anti-1080 candidate Peter Salter got in the election.
Mr Lane said he was not surprised to hear Haast had been called off this year.
He said 1080 drops interfered with the natural rodent cycle.
"Trees have been masting for years. Then they target those rodents, they die, but they never get everything. They will be doing it [pest control] for the rest of our lives."
Fellow activist Mary Molloy, welcomed DOC's decision to postpone the Haast drop. She predicted some months ago the mast would be patchy, especially after Cylone Ita.
"I'm very pleased they're recognising there hasn't been a masting. It's been very patchy."
Prefeeding is likely to start in the next month for the Abbey Rocks operation.
- Greymouth Star