Pēhea ai mātou e tiaki i te pae maunga o Hūnua i ngā kīrearea How we protect the Hūnua Ranges from pests

Possums and rats threaten native animal and plant species in the Hūnua Ranges.

Hūnua Ranges 2025 pest control complete

In late October 2025 we completed an aerial 1080 pest control operation in the Hūnua Ranges. 1080 is a poison containing sodium fluoroacetate used to control pest species.

The area included:

• Hūnua Ranges Regional Park
• Waharau Regional Park
• Whakatīwai Regional Park
• neighbouring Department of Conservation (DoC) land.

Visit Our Auckland to read more about the pest control operation.

Results of the 2025 operation 

Monitoring after the operation shows possum numbers dropped dramatically, from 2.2 per cent of traps catching a possum before the operation to just 0.16 per cent afterward.

Rat numbers dropped even more dramatically. Before monitoring began, rat activity was extremely high, with 90 to 100 per cent of tracking devices detecting rats. After the control work, only about 1.3 per cent detected rats.

These results exceeded the targets set in the 2025 operational plan. We aimed to reduce possum numbers to two possums caught per 100 trap checks and three rats detected out of 100 tracking tunnels. Both targets were comfortably met.

At these levels, the forest can recover and native species can thrive. 

These targets follow national biodiversity protection and recovery guidelines.

Caution period lifted 

Dogs can return to the on-leash areas of the park from Monday 9 March 2026.

During pest control operations and for four to six months afterwards, dog owners should not bring pets into the parkland. 1080 pellets are highly toxic to animals, particularly dogs.

Monitoring of bait and carcass breakdown is now complete. Results show complete breakdown has occurred so the caution period can be lifted.

Safety tips 

For more information on keeping your dog safe, check our dog protection fact sheet.

Pest control method

We follow strict guidelines set out by the Environmental Protection Agency (EPA) and the Ministry of Health (MoH).

We used a two-step process to make sure the operation is as successful as possible.

• Step one: Put non-toxic cereal bait (prefeed) in targeted areas to encourage pest animals to feed in that area.
• Step two: Drop toxic bait containing 1080 on targeted areas using a helicopter guided by a global positioning system (GPS).

We used two kilograms of cereal pellets per hectare. To manage the large area and protect water-supply reservoirs, we divided the operational area into two blocks:

• Cossey and Mangatangi
• Wairoa and Upper Mangatāwhiri.

During the operation, we:

• worked on one block at a time
• turned off the reservoir for that block.

Before we returned the reservoirs to service we tested the water until sampling showed no traces of 1080.

Park access

During the operation, we:

• closed access roads and tracks within the parks and reserves
• put warning signs outside affected areas.

We reopened the parks after we carried out a full track clearance programme.

This operation was in water catchment areas, which required careful planning and working closely with Watercare.

We put measures in place to ensure the ongoing safety of Auckland's water supply, including:

• no flying over water supply reservoirs
• exclusion zones around reservoirs where bait was not applied
• using accurate (GPS) technology to apply bait
• closing reservoirs before the operation and only reopening them after water testing confirms there was no 1080 in the water
• worked with landowners to understand which streams in the operational area are used for drinking water.

Observe all information and warning signs. It is a criminal offence to remove signs or bait without permission.

Ground-based pest control will be in place on areas of parkland and some surrounding private land that was not treated during the aerial operation.

Always keep your dogs on a leash. This is a requirement within the park at all times.

A Controlled Area Notice is in place across the native forest area of the Hūnua Ranges Regional Park and adjoining DoC-administered lands. This is to protect against kauri dieback disease.

Use hygiene stations to clean and disinfect all footwear and equipment to ensure you do not carry any visible soil into the controlled area.

We have done three aerial control operations in Hūnua, in 2015, 2018 and 2022.

Post-operational monitoring shows our previous operations were very successful.

The number of pest species reduced dramatically, with possum numbers at an all-time low in Hūnua since 2015.

Hūnua's kōkako population has also reacted well to pest control operations.

Population records show an increased number of kōkako:

• In 2015, there were 50 pairs of kōkako.
• In 2022, the kōkako population reached 259 pairs, the second-largest mainland population of kōkako in New Zealand.

In 2011 the Parliamentary Commissioner for the Environment released an independent report endorsing the use of 1080. Download the report from the Parliamentary Commissioner for the Environment website.

DoC also looks after large areas of parkland and uses 1080 to manage animal pests.

For more information on the use of 1080, visit the DoC website.