Rodent removal on Aotea, Great Barrier’s Broken Islands on target

On some of the most remote islands off Aotearoa New Zealand - the team at Tū Mai Taonga have been removing rats. The methodology has been successful and the team is taking its learnings to mainland Aotea to tackle the next phase in the iwi-led predator free project. 

Rylie Arnell, Field Operations Manager, is building a predator-free workforce in some of the most challenging terrain in Aotearoa, New Zealand.

Success in eliminating rats from most of the outer islands of Aotea (Great Barrier Island), the Broken Islands, has been a major milestone for Tū Mai Taonga in 2024.

“We are on target for phase one and have gained valuable insights over the past year which will help determine the pathway for phase two of the project, when we progress to the Aotea mainland” says Rylie Arnell, who is leading this aspect of the initiative.

Rats pose a substantial threat to the local ecosystem, preying on birds eggs, insects, and impact the bush by consuming a large number of regenerating seeds.

After eradicating rats and following up with extensive monitoring, the project removed all toxic bait from Rangiahua Island in June 2024, after a successful trial using a first-generation rodenticide. Since then, the island has been operating under a robust biosecurity network.

Rangiahua Island Shaun Lee

The team has been successful in eliminating rats from Little Māhuki, and has managed to keep the rodent populations on Māhuki at an all time low.

“We have managed to isolate the remaining pockets of rats on Māhuki and know exactly where we need to target next.

“They are near zero, but the access is challenging, and we are monitoring them closely.”

This progress has been particularly rewarding for the one family living on Māhuki Island, who have observed trees and fruit flowering for the first time in years.

The initiative has also had a positive impact on the island’s lizard population.

The team has been trialing different lures, learning about habits and preferences of the rodents, which will help inform the approach to the next phase of the rodent removal, on mainland Aotea.

“Rats, like people, are looking for a balanced diet. Unfortunately, there is no ‘perfect lure’. It all depends on factors like time of year, weather, and food availability.

“If their diet consists of heavy protein foods, such as insects, sea food and eggs, — we have experimented with using a sweeter supplement like licorice or chocolate. If they are eating berries or seedlings they prefer a protein based food — like peanut butter.”

One of the success stories has been building a workforce — a role which is one of the most challenging field positions in Aotearoa New Zealand’s predator free movement.

“Many of them are now fully trained in the mechanisms of feral cat and rodent removal. We are extremely proud of them and their achievements.”

“Building a comprehensive grid system of traps has been incredibly challenging for our field crew,” Rylie says. “Carrying 8-10 wooden bait stations through thick gorse, up cliffs, while navigating wasp nests and constant bending, is no easy task. These conditions are extremely tough.”

“It’s all about scale now,” says Rylie. “We are pumped about our achievements and learnings so far and can’t wait to apply that knowledge to greater Aotea.”