Eradicating rats on Palmerston Atoll in the Cook Islands

Department of Conservation —  05/04/2023

Thanks to a collaborative predator eradication project, introduced rats could be gone from Palmerston Atoll by the end of the year. 

Members of the aptly named ‘RAT’ team and some of the Palmerston community. 
📷: Finlay Cox

White sand beaches, crystal-clear turquoise water and gentle swaying palm trees… that’s the vibe in Palmerston Atoll.

But you know what ruins the vibe? Rats. Rats are most definitely not the vibe. But they’re there and they’ve been causing problems for the community’s wellbeing and biodiversity for ages. But hopefully not for much longer. 

We’ve been working with Cook Island agencies and the Palmerston community to eradicate introduced rats from Palmerston Atoll.  

In November last year, our National Eradication Team member’s Em Oyston and Finlay Cox travelled to Palmerston to assess whether removing rats is possible, and how it could be done.  

The trip was a chance to conduct research in preparation for an eradication, but it was also a special opportunity to share technical expertise with the local community, and for the team to learn about their islands and way of life.

Home Island, Palmerston Atoll 
📷: Finlay Cox 

Rats impact food security, health and biodiversity

Palmerston Atoll is a remote group of islets and sandbars about 400km from Rarotonga. Most of the islets are inhabited only by wildlife, and the only (human) populated island is home to a community of just 40 people. 

Rats have been unwelcome guests in Palmerston for a long time. Kiore (pacific rats) arrived on the motu from early Polynesian voyaging and ship rats likely turned up in the 20th century on copra trading vessels. 

Rats impact the livelihoods of the Palmerston community by eating local produce, fouling food stores and clothing, and being a potential vector for disease. Being such a remote community, these impacts are compounded as people rely on locally grown and stored foods. 

Rats also threaten the atoll’s native animals and plants. Surrounding Islands that rats never invaded have noticeably higher numbers of species like coconut crabs and green turtles, as well as nesting seabirds like brown booby, frigate birds, red-tailed tropic birds, and the Pacific pigeon. 

Rats prey on the young of these species, harming their overall population and survival.  

Getting rid of rats for good would make a massive difference to the Palmerston community’s food security, health and the ecosystem, thereby enhancing their resilience to climate change. 

A red tailed tropic bird and chick. These ground nesting birds nests and chicks are vulnerable to rat predation, and cannot be found nesting on the islets where rats are present on the atoll. Their healthy populations on the rat-free islets gives us an idea of the wins for nature that will be achieved when rats are successfully eradicated. 
📷: Em Oyston 

Preparing for rat eradication with the community

Em and Finlay spent three weeks on the atoll conducting research and field work with Cook Island agencies and the Palmerston administration team, known collectively as the (aptly named) ‘RAT’ team. 

The research included identifying the distribution of rats, determining the amount of bait needed to eradicate the rats, and identifying social issues such as the impact of the eradication work on people’s daily activities. 

Excitement over the first rodent caught and measured – what will it be?  
📷: Teariki Tearetoa 

Em and Finlay were stoked to see the progression and knowledge sharing between the RAT team and the Palmerston community. 

Community members jumped at the opportunity to get stuck in with the fieldwork. Thanks to sharing from the RAT team, many locals became confident installing and running devices for rodent detections, identifying different rat species, running bait measurement plots, and recording and collating data. 

Towards the end of the trip, the local community took a lead in aspects of the fieldwork, with school students measuring bait lines and members of the community establishing rodent detection lines. 

Finlay showing honorary members of the RAT team how to program trail cameras.  
📷: Em Oyston 

By the end of the study, the team had achieved their research objectives, bringing the community a big step closer to getting rid of rats on Palmerston.  

Using the information gathered during the study, we’ll be leading a full-scale eradication in mid-2023, with Palmerston’s community, the Cook Island’s National Environment Service, the Ministry of Agriculture, and the local NGO, Te Ipukarea Society. 

The project shows the power of collaboration in achieving predator free goals, both in the Pacific and in New Zealand. Not only is the project supporting Pacific communities by sharing technical knowledge and skills, but it’s also helping to grow our knowledge of island eradication.  

This research builds on over 70 years of research and worldwide expertise in invasive species eradication from precious islands.  

Read more about our island eradication work and how it brings us one step close to Predator Free 2050: Eradicating predators from islands: Predator Free 2050 

NGO Te Ipukarea Society made a video about the project and what rat eradication would mean for the Palmerston community. Check it out below:

This work is funded by the New Zealand Ministry of Foreign Affairs and Trade (MFAT), and is delivered through the Pacific Regional Invasive Species Management Support Service (PRISMSS).  

The New Zealand Department of Conservation, the Secretariat of the Pacific Regional Environment Programme (SPREP), and Manaaki Whenua have joined forces to support Pacific Island Countries and Territories to take stronger action against invasive species, and thereby build resilience to climate change.

One response to Eradicating rats on Palmerston Atoll in the Cook Islands

    Tom MacTavish 06/04/2023 at 9:20 am

    Great story thanks. Nice to read about collaboration with our pacific neighbours.