Tongan Island’s Seabird Population Rebounding Following Rat Eradication Initiative

A significant increase in seabird populations and other land wildlife was observed less than one year since the Kingdom of Tonga carried out a ground-breaking mission to restore and re-wild Late Island by eradicating invasive rats, potentially marking it as the largest rat-free island in the Pacific.

During a recent monitoring visit to Late Island in May 2024, conducted by members of the Vava’u Protection Association, Tonga Department of Environment, and Island Conservation as the technical lead for the PRISMSS Predator Free Pacific (PFP) Programme, promising signs emerged suggesting that this sanctuary of biodiversity for Tonga may be well on its way to achieving this monumental goal. 

“Upon approaching the island after a 35-mile boat ride, we immediately noticed a significant rise in seabird populations, with hundreds of boobies, noddies, frigatebirds, and terns circling the island – a stark contrast to the smaller numbers observed in 2023. We also witnessed and heard more land birds, crabs, and lizards than before,” said Helen Fairlamb, Island Conservation’s Conservation Impact Monitoring Specialist. 

To ensure accuracy, a bird point-count survey was conducted during the five-day monitoring visit, demonstrating that the number of birds on Late Island had doubled in just nine short months (compared to a survey carried out in 2023 before the operation) following the removal of invasive rats.

Over the course of a week, the team worked on re-deploying biodiversity monitors, including camera traps and acoustic recorders, programmed to continuously assess native species population dynamics. More promising news emerged after rat detection systems set up to gauge the operation’s success and eDNA results detected zero sign of rat presence, making it highly probable that the island will be declared free of invasive rats in 2025 as anticipated.

“Bird point counts are just one measure of success; however, out of caution, we will continue to monitor the island in a variety of ways in the coming years,” said Island Conservation Project Director Richard Griffiths.

“While we recognize the need for continued monitoring, these early signs of recovery highlight the resilience of nature and the potential for effective conservation actions to drive positive change. The rebounding native species populations on Late Island serve as yet another beacon of hope, demonstrating that our collaborative conservation efforts indeed result in tangible impacts, safeguarding our planet’s biodiversity for future generations.”

Once the island is declared rat-free, the partnership will implement another conservation intervention with the re-introduction of threatened endemic species such as the Malau (Tongan Megapode). This unique land bird roosts atop Tonga’s volcanic islands, warming its eggs not via body heat but rather by the heat of these islands’ steam vents.

“There are currently only two populations of this species in the world, so establishing a third population on Late Island would be yet another incredible win for conservation – and more evidence that conservation works,” said Fairlamb.

SPREP’s Invasive Species Adviser David Moverley has been working with Tonga to progress this work on Late for over 10 years and commends the team at the Environment Department and VEPA for their relentless efforts to reach this milestone.

“The successful removal of rats from Late Island is a significant milestone for Kingdom of Tonga. Late Island was identified for the removal of rats in the first National Invasive Species Strategy and Action Plan 2013-2020,” said Moverley. “Following the development of a Feasibility Assessment and Operational Plan in 2014, it has been a long journey to secure the funding required to complete the job. It really is a credit to the Tongan team from the Environment Department for their ongoing commitment and I look forward to seeing the people of Tonga enjoy the incredible opportunities that this now provides in the form of tourism and sustainable development.”

This project was made possible with support from the Secretariat of the Pacific Regional Environment Programme (SPREP)-led Pacific Regional Invasive Species Management Support Service (PRISMSS) through its Predator Free Pacific (PFP) Programme. Funding was initiated through the GEF 6 Regional Invasive Species Project and co-financed in partnership through the Island Ocean Connection Challenge.

Bell Laboratories, a longtime supporter of rodent eradication initiatives in sensitive environments, as well as a supplier of rodenticide for Island Conservation projects, was involved in this project.