Department of Conservation national predator control programme operations lead Colin Bishop said the bait drop was necessary because native species were fighting for survival due to predation.
The aim was to protect vulnerable native species such as kaka, the South Island robin, native mistletoe and New Zealand falcon/karearea.
The aerial toxic bait drop was in response to a large beech mast (forest seeding) event in summer 2022-23 that triggered a rise in pest numbers.
"These mast events lead to increased numbers of stoats, possums and rodents, which have a devastating impact on vulnerable native species," Mr Bishop said.
Previous operations had taken place in the area in 2010, 2014, 2016 and 2020 and had resulted in increased numbers of birds and other native species.
The programme was a critical part of Predator Free 2050.
Alongside the 1080 bait drop, large-scale stoat-trapping operation had been operating to protect native fauna.
Bait was the most effective tool to control introduced predators over large areas and rough terrain.
Signs would be in place to warn people bait may be present.
The green cylindrical bait pellets were about 16mm in diameter, and poisonous to humans, domestic and game animals. Dogs were particularly susceptible until poison carcasses had disintegrated.
Dogs should not be taken into the treated area until the caution period was over and signs removed which could take four to eight months after a drop.
Neighbouring landowners and other stakeholders had been notified.
The drop area extended from the south coast from the Wairaurahiri River, west to Big River up to the east shore of Lake Poteriteri and across to the west shore of Lake Hauroko.
Mr Bishop said a full list of alerts and areas could be checked on the Doc website or people could contact their local visitor centre.
- By Toni McDonald
