Eradication

In June/July 2002 the eradication of Pacific rats from Maninita Island in the Vava'u group of the Kingdom of Tonga was attempted using Brodifacoum pellets in bait stations. In December 2002, Maninita was revisited and rat trapping carried out to determine if rats were present. While no rats were caught and none were seen, further monitoring in June 2003 is recommended before the island is declared "rat free '.

The restoration of the small offshore islands of Nu’utele (108ha) and Nu’ulua (25ha) has long been identified as a priority for biodiversity conservation in Samoa. The first step towards restoration was the aerial spreading of brodifacoum to eradicate Pacific rats (Rattus exulans) in August 2009. Procedures for the eradication followed those used in New Zealand and involved technical experts from that country.

Introduced rats (Rattus spp.) can affect island vegetation structure and ecosystem functioning, both directly and indirectly (through the reduction of seabird populations). The extent to which structure and function of islands where rats have been eradicated will converge on uninvaded islands remains unclear. We compared three groups of islands in New Zealand: islands never invaded by rats, islands with rats, and islands on which rats have been controlled. Differences between island groups in soil and leaf chemistry and leaf production were largely explained by burrow densities.

Invasive species compete with endemic species and if successful can displace native species in the host region (Cororaton et al., 2009).

In 1989, the kakerori (Pomarea dimidiata) was one of the 10 rarest birds in the world with a declining population of just 29 individuals living in forested hill country in the Takitumu Conservation Area (TCA) of south-eastern Rarotonga, Cook Islands. Following 12 years of rat poisoning, the population had increased to 255 birds in August 2001. The programme then shifted from ‘species recovery’ to ‘sustainable management’ of the Rarotonga population at 250 to 300 birds. The rat poisoning effort was reduced, and an ‘insurance’ population was established on Atiu.

In 1989, the kakerori (Pomarea dimidiata) was one of the 10 rarest bird species in the world, with a declining population of just 29 birds. During each breeding season since then, rats have been poisoned within the 155 ha of forested hill country they occupy in the Takitumu Conservation Area in southeastern Rarotonga. As a result, the kakerori population has rebounded, with a minimum of 292 birds found on Rarotonga in August 2003. In 2001/02, the emphasis of management shifted from the .recovery. of kakerori to a programme aimed at .sustaining. the population at 250.300 individuals.

For one of the species potentially at some risk of poisoning under the proposed rat eradication regime, the Friendly Ground Dove, Nuutele and Nuulua hold populations that are nationally significant. The complete loss of these populations would threaten the survival of the taxon in Samoa. Some authors consider the Samoan doves to be a separate race (Gallicolumba s. stairi) from those in Fiji and Tonga (Watling, 2001). Outside Samoa, the race is only found on the small island of Ofu,

This is the final report describing the results from the second and third years of a three-year programme to determine the costs and benefits of aerial 1080 possum control operations to North Island robins (Petroica australis longipes) and moreporks (Ninox novaeseelandiae) in Pureora Forest Park, North Island, New Zealand. During this study robins were individually colour-banded, and moreporks radio-tagged in both treatment and non-treatment study areas. A poison operation using carrot baits in August 1997 covered 8577 ha and incorporated the 300 ha Waimanoa study area.

There are five toxicants (brodifacoum, bromadialone, coumatetralyl, diphacinone, and flocoumafen) registered for rodent control in New Zealand. They are all anticoagulants and are available in water-resistant bait formulations (i.e. wax coating, wax block, or egg). Several new rodenticide products, which are currently in the process of being developed or registered, including a new anticoagulant difethialone, have also been identified.

Although Talon® baits containing brodifacoum have been used successfully in eradicating rats from some of New Zealand’s offshore islands, little is known about any environmental effects of this toxin. We sampled invertebrates, blackbirds, soil, and water at intervals of 2 days to 9 months to determine whether brodifacoum residues were present after aerial distribution of Talon® 20P cereal pellets on Red Mercury Island and after bait-station use of Talon® 50WB wax-coated cereal blocks on Coppermine Island.