Department of Conservation communications advisor Trish Grant said non-toxic baits had been distributed across 74,600 hectares of Kahurangi National Park in the Parapara and Gouland Downs operational blocks on Wednesday.
As non-toxic bait was being applied there was no requirement to close roads and tracks during the operation, Grant said.
Department of Conservation staff would be situated on the Heaphy Track to inform the public about the operation with signs at the track entrances and huts.
Grant said the pre-feed application of non-toxic baits would encourage rats to eat 1080 baits that would be applied at a later date when there was suitable weather.
It would usually be five days before it was followed up with a 1080 bait application but the timing was dependent on a sufficient period of suitable weather.
The operation is part of the department's Battle for our Birds national pest control programme.
The Kahurangi National Park was the largest site in the programme and it was planned to cover about 295,000 hectares of the park and other conservation land in different stages.
Grant said the predator control was being carried out to knock down rat numbers and it would also protect native species from a summer surge in stoat numbers.
The use of 1080 has been controversial in Golden Bay, with protests taking place in Takaka last year against the operation in the Kahurangi National Park.