Rat Eradication a Success in Tonga

Recent monitoring has resulted in the confirmation that rats have been eradicated from the islands of Malinoa and Motu Tapu in Tonga following a successful eradication operation in 2015..

"We are very pleased with the result and it's great to see the motivation to do more. Invasive vertebrates are a major threat to munch of the Pacific's biodiversity, but with community buy-in combined with increased skills and experience we can turn the tide," said Mr. Richard Griffiths, Project Director, Island Conservation.

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Saia from Tonga and Sosefo from Wallis et Futuna set a rat trap to determine whether the eradication on Motutapu Island was successful. Monitoring consists of setting rat traps and looking for rat signs all over the island, It takes about 8 months for the rat population to build up to a detectable level on small islands following the eradication operation. | Photo: Robert Griffiths 


The islands of Malinoa and Motutapu were assessed by completing day and night surveys for rats and rat sign, and setting rat traps that were checked the following day.

Observations were also made of the noticeable increases in the different species of birds such as the wattled honeyeater also known as the fulaehehu (Foulehaio carunuculata) and Polynesian starlings also known as Misi or (Aplonis tabuensis). It was also noted that Black-naped terns (Sterna sumatrana) were nesting and had eggs on the beaches of both islands.

IMGP0078One of the many elements of biodiversity that benefits from removing rats is the birds and their ability to nest and raise their young chicks. Both islands had nesting Black-naped terns (Sterna sumatrana) with intact eggs. | Photo: Robert Griffiths


Other observations made include the uncommonly seen Ghost crabs (Ocypode ceratophthalmus) and (Ocypode pallidula) during the beach surveys, these usually remain hidden in their burrows during the day. Also noted were the increase in numbers of fruit and flowers that would have previously been eaten by rats.

This activity began in August last year with a special training to help countries with many small islands to be able to complete small and simple eradications themselves with limited resources and very little assistance from outside organisations.

Participants from Kiribati, Republic of the Marshall Islands, Tonga and Wallis and Futuna took part in the capacity development workshop that included a practical activity of removing rats from the islands of Malinoa and Motutapu in the Tongatapu island group of Tonga.

"It is important that Pacific countries have the capacity to manage invasive species. This project is aimed at facilitating countries to succeed in meeting meaningful conservation goals, eventually on their own accord, in bite size chunks," said Mr. David Moverley, the Invasive Species Adviser of the Secretariat of the Pacific Regional Environment Programme (SPREP).

"This will compliment more complex projects and conservation goals which require more extensive resources, technical assistance and finance."

"Tonga can do this. With what we have learned and the skills we now have we can protect our smaller but important islands and their biodiversity from the many impacts of rats," said Mr. Viliami Hakaumotu, Invasive Species Coordinator of Tonga.

With the positive outcomes of the rat eradication in Malinoa and Motutapu, the program was replicated last month on two further islands – Fangasito and Luahaipo in the Vava'u island group.

These islands were determined as priorities for protection during the Vava'u BIORAP, or Biodiversity Rapid Assessment, completed by SPREP and the Tongan Government under the Global Environment Facility – Pacific Alliance for Sustainability (GEFPAS) Integrated Island Biodiversity Project.

It is anticipated that this work will be similarly successful and provide protection to the biodiversity of these important islands which are also important nesting sites for the critically endangered hawksbill and green turtles.

The rodent eradication from small islands initiative was a partnership between SPREP, Island Conservation and the Government of Tonga. It is supported by the "Global Environment Facility Eradication, Management and Control of Invasive Alien Species in the Pacific Islands Project", United Nations Environment Program, Vava'u Environmental Protection Agency and Fonds Pacifique.

For further information please contact David Moverly, SPREP's Invasive Species Adviser (davidm@sprep.org)
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