Problem Definition-Research

The Cook Islands Ministry of Agriculture seeks approval for the release of the plan pathogen Puccinia xanthii Schw. (Pucciniales: Pucciniaceae) into Rarotonga for biological control (biocontrol) of the introduced plant cockleburr Xanthium pungens Wallr. (syn. Xanthium strumarium; Xanthium occidentale Bertol.) (Asterales: Asteraceae).

The Cook Islands Ministry of Agriculture seeks approval for the release of a gall-forming wasp Tetramesa romana and an armoured scale insect Rhizaspidiotus donacis into Rarotonga for biological control (biocontrol) of the introduced plant giant reed Arundo donax (Poales: Poaceae).

Invasive plants seriously threaten native habitats throughout the Pacific region, including the Cook Islands, where numerous invasive weed species of agricultural concern are also present.

This study describes the biodiversity values of Malden Island, Kiribati, and assesses the potential benefits, feasibility and costs of removing key invasive species. Malden is relatively pest-free, but two significant invasive species are present - feral house cats and house mice. We believe that the most cost-effective and beneficial conservation action in the short term for Kiribati is to undertake a cat eradication programme.

Rat eradications on tropical islands have been less successful than operations in temperate climates. This is likely due to poor understanding of the factors unique to tropical regions that rat populations respond to, such as high numbers of land crabs, aseasonal climates and habitats not found at higher latitudes. On Aldabra Atoll, southern Seychelles, black rats were monitored for one year in three habitats over three climatic seasons to investigate changes in density and breeding to inform planning for a possible rat eradication.

Invasive rats are found on most island groups of the world, and usually more than one species has invaded. On tropical islands populations of different invasive rat species can co-exist on very small islands, but the population dynamics of such co-existing rat species, their impact on each other, and the mechanisms of coexistence are not well known. This lack of knowledge is a barrier to improving the success rate of tropical island rat eradications.

Rodents remain one of the most widespread and damaging invasive alien species on islands globally. The current toolbox for insular rodent eradications is reliant on the application of sufficient anticoagulant toxicant into every potential rodent territory across an island. Despite significant advances in the use of these toxicants over recent decades, numerous situations remain where eradication is challenging or not yet feasible.

Rodent eradications undertaken on tropical islands are more likely to fail than eradications undertaken at higher latitudes. We report on 12 independent rodent eradication projects undertaken on tropical islands that utilized the results of an in situ bait availability study prior to eradication to inform, a priori, the bait application rate selected for the eradication. These projects also monitored bait availability during the eradication.

Invasive mammal eradications are a proven, effective method of restoring damaged ecosystems and preserving biodiversity. On most tropical oceanic islands indigenous land crabs compete with targeted alien species for bait and interfere with traps and detection devices. Current eradication practices are inherited from successful termperate or subantarctic campaigns, yet we do not possess trued and tried methods for managing land crab interference.