Problem Definition-Research

Invasive rodents have significant negative impacts on island biodiversity. All but the smallest of rodent eradications currently rely on island-wide rodenticide applications. Although significant advances have been made in mitigating unintended impacts, rodent eradication on inhabited islands remains extremely challenging. Current tools restrict eradication efforts to fewer than 15% of islands with critically endangered or endangered species threatened by invasive rodents.

House mice are significant invasive pests, particularly on islands without native mammalian predators. As part of a multi-institutional project aimed at suppressing invasive mouse populations on islands, we aim to create heavily male-biased sex ratios with the goal of causing the populations to crash. Effective implementation of this approach will depend on engineered F1 wild-lab males being effective secondary invaders that can mate successfully.

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.