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Fijian seabird isles to be ‘de-ratted’

…safe haven planned

Invasive predators such as cats and rats are to be eradicated from some of Fiji’s most important seabird islands, as part of a project undertaken by BirdLife International’s Fiji programme, with the support of landowners, and funding from the David & Lucile Packard Foundation. The Ringgold Isles, a remote archipelago forming an outlier group to Vanua Levu (the northernmost of Fiji’s two main islands), are mostly uninhabited, and their relative isolation should make them a safe haven for seabirds like the Black Noddy Anous minutes and Red-footed Booby Sula sula. However, Pacific Rat Rattus exculans, which has successfully naturalised on many islands, is contributing to a progressive decline in seabird breeding populations through the predation of eggs and chicks. Rats also hinder regeneration of coastal forest –essential to tree-nesting species like Red-footed Booby- by eating the seeds of native trees.

The first phase of the project, a survey to establish seabird numbers and the presence of invasive predators, was completed by BirdLife staff in August 2007, with local community assistance. The survey provides baseline data which will enable pre- and post-eradication monitoring to be carried out. “The Survey has confirmed that these islands are among Fiji’s most important for seabirds, and once the data has been analysed some islands will also meet criteria for internationally important bird areas (IBAs),” said Vilikesa Masibalavu manager for BirdLife’s Fiji programme. “The large seabird populations include many thousand Gogo (Black and Brown Noddy Anous stolidus), and hundreds of Toro (Brown Sula leucogaster and Red-footed Booby) and Manumanu ni cagi (Lesser Frigatebird Fregata ariel).” Also present were Masked Booby Sula dactylatra, Black-naped Tern Sterna sumatrana and White-tern Gygis alba.

The islands were found to support good populations of invertebrates such as coconut crabs Birgus latro, which have been extirpated from most of the islands in Fiji. They are also foraging and nesting sites for endangered sea turtles and native lizards. The cryptic and elusive Fiji Banded Iguana, an Endangered species, may also occur on some of the Ringgold Isles. Many of these species are believed to be affected by rat predation and are also expected to benefit when the rats are removed (as has been demonstrated elsewhere).Rats were found on seven of the eight islands surveyed. On six islands the rat population was found to be ‘medium to high’. Steve Cranwell, who took part in the survey, explained: “Where numbers were deemed to be high, rats were seen frequently during the day and at night the forest floor was crawling with them. Having set a trap you would walk ten metres only to hear it snap shut on the next victim. Medium densities weren’t visibly that dissimilar, other than rats being less visible during the day and not quite the seething mass at night. The forest would still chorus to the snap of traps.”

The lower rat numbers on the seventh were attributed to the presence of a feral domestic cat. As for the eighth island, Steve Cranwell says it is likely that they are still present in lower numbers.

“Rats eat eggs and chicks, whereas cats can quickly decimate an entire seabird colony, particularly those that nest on the ground,” said Vilikesa Masibalavu. “The information collected from the survey will be used to determine if these introduced predators can be eradicated, which in addition to technical considerations requires the full support of the islands’ owners and communities, and the ability to prevent future reinvasion.”Local communities and landowners have already pledged their support for rat eradication, planning and discussions are now going on to establish how the eradication is to be carried out, and what restrictions on access, crab harvesting and other activities may need to be imposed until it is complete. The ‘operational plan’ is expected to be finalised in early 2008. “This is not restricted to laying the rat bait, but includes bio-security for the island (ie how rats and other invasive species will be prevented from returning in the future),” explained Steve Cranwell. “Eradication will occur sometime between May and August; the exact timing is dependent on many things, and ultimately comes down to the weather.”

He added that the involvement of the local communities and landowners was vital throughout the eradication process and beyond. “Without their support, bio-security will fail.”

The Tui Laucala (chief or king of Laucula), whose jurisdiction includes the Ringgold Isles, said that the isles are the ancestral lands of his people, and home to ancient villages and burial grounds of great importance. “As guardians of the land, it is our responsibility to protect these islands. With the support of BirdLife this is an opportunity for us to ensure the islands’ birds and other natural resources will be there for our ‘ira na gone’ (our children and their children).”

4th July 2014