The Cook Islands’ Palmerston Atoll has been declared rat-free following a mammoth eradication effort by the local community, with support from agencies in Rarotonga and New Zealand.
A rat eradication operation took place on the atoll’s Home and Cooks islets over August and September 2023. Monitoring to confirm the atoll’s rat-free status was recently completed, with trail cameras and traps showing no evidence whatsoever of rats.
The atoll’s Executive Officer, Arthur Neale, says Palmerston’s rat-free status means the world to everyone who lives on the atoll.
“Rats infested the atoll for over a century. They ate our crops, invaded our homes and harmed local wildlife. We saw the rat problem becoming worse, with the potential to seriously undermine our resilience in the face of climate change impacts,” he said.
“Benefits from the rat eradication are already evident. Our food security has improved massively. Fruits like guava, mango and star fruit are now abundant and free from rat damage. Our nu mangaro (a coconut tree variety) are thriving. Vegetables, especially cucumbers, have seen an astonishing increase in yield.
“We’re very excited to see more native species now rats are no longer eating them. Seedlings of tamanu and puka are increasing and we’re seeing and hearing more birds. Wood pigeons and red-tailed tropic birds have returned to Home Islet. Crabs and lizards appear to be more abundant.”
The work that led to a rat-free Palmerston Atoll began several years ago when local NGO Te Ipukarea Society prepared the Palmerston Island Natural Resource Management Plan 2020, which highlighted the potential benefits of eradicating rats.
From there, a partnership to eradicate rats from Palmerston Atoll was set up between New Zealand’s Department of Conservation (DOC), the Palmerston Atoll community, Cook Island’s National Environment Service and Ministry of Agriculture, and Te Ipukarea Society.
Mr Neale says the community’s preparations for the eradication operation were “immense”.
“We had to ensure there wasn’t any food for rats – bait had to be the only option. Everything was sealed up, from food to kitchen wastewater systems. We removed sugar cane from our gardens and fruit from trees. We couldn’t risk having livestock feed and faeces available to rats, so we had to carefully manage our chickens and pigs,” he said.
The six-week operation covered Palmerston Atoll’s Home Islet, which has around 30 inhabitants, and the uninhabited Cooks Islet. Bait was hand laid across the two islets and 116 buildings on Home Islet were baited.
Em Oyston from DOC was the project team leader and one of three DOC National Eradication Team members on the ground for the operation. The DOC team has international expertise in island eradications.
“Working on this project with the community and Cook Island agencies was a privilege. The operation’s logistics were challenging, so Palmerston Atoll’s official rat-free status is very satisfying and a huge credit to everyone who played a role in this project,” said Ms Oyston.
To help the atoll to remain rat-free, biosecurity measures are in place. Detection devices and traps are installed and visiting vessels will be checked offshore for rats or any other pests.
Biodiversity Coordinator at the Cook Islands National Environment Service, Jessie Nicholson says the rat eradication is a national milestone.
“Palmerston is the first inhabited island in the Cook Islands to be deemed rat-free. This is an incredible achievement that should be celebrated by all people of the Cook Islands.”
“Some of our outer island communities have heard about the eradication in Pamati (Palmerston) and expressed interest to conduct rat eradications on their islands also. Palmerston is truly leading the way.
“The National Environment Service is extremely pleased with the successful outcome of the eradication and wishes to acknowledge all those who helped along the way to make this a reality for Palmerston,” she said.
The work was made possible by funding from the New Zealand Ministry of Foreign Affairs and Trade, a major supporter of the Pacific Regional Invasive Species Management Support Service, a collaborative Pacific-led partnership to restore island resilience.
