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This report assesses the feasibility of eradicating rats from Palmerston Atoll – a small inhabited Atoll located in the Southern Cook Island group. The project was originally requested by the community so has social acceptance and political support. The project is being funded by the New Zealand Ministry of Foreign Affairs and Trade through the Managing Invasive Species for Climate Change Adaptation in the Pacific project. The Department of Conservation are leading the operational planning and delivery of the project, in collaboration with multiple Cook Island partner agencies and the Palmerston Island community. The feasibility study reviews why the eradication is being done; whether it is achievable; sustainable and acceptable; and identifies what the key issues and dependencies are; and proposes the next steps if the project is to proceed.

This document covers the operational planning for the eradication of ship rats and kiore from Palmerston Atoll. Kiore are present on two motu (islands) on Palmerston Atoll – Home Island, and Cooks motu; while ship rats are present on Home Island only; thus, the scope of the eradication includes only these two islands for the hand broadcast application of toxic baits. Ensuring rats do not establish on other motus in the Atoll is also critical to the project’s success.

This document reports on the operational activities carried out over the field work delivery period of the Palmerston Atoll rat eradication. The purpose of doing this is to retain and build institutional knowledge and learnings for future operations; as well as report on the operational proceedings in the event they need to be referred to in the future.

Coral atolls are natural laboratories within which to examine ecological processes (Sachet, 1967; Lee, 1984). They are often isolated, in some cases little disturbed, and have a geologically recent history of terrestrial plant colonisation. Reef islands around the rim of most atolls are Holocene in age. They are composed of biogenic skeletal sediments and have developed since reef growth caught up with sea level which stabilized after post-glacial sea-level rise. Plant colonisation of most of these islands must have occurred over a period of no more than 6000 years.

Rarotonga and Aitutaki form the summits of separate volcanic masses rising from depths of 4000 m, at which depth the cones are 45-55 km in diameter (Summerhayes and Kibblewh 1966, 1967).The lower slopes of the cones average 15-25 increasing to 30 in the upper 750 m and becoming very steep the surface reef is approached. The Mauke-Aitutaki line of islands is thought to be of early Tertiary age: the surface volcanics are much eroded, with a subdued topography, or are capped with limestones (Wood, 1967; Wood and Hay, 1970). On Rarotonga, where the relief is much stronger (maximum altitude 640 m), radiometric ages of 2.3-2.8 million years date the 1 as Pliocene (Tarling, 1967). Mangaia, with a cap of Oligoce Miocene limestones, must be much older (Marshall, 1927). Evi dence from the deep-sea drilling programme indicates that th ocean floor in the area of the southern Cooks is Paleogene (22.5-65 million years) in age (Winterer, 1973), thus provid a maximum age for the islands. It is probable that the gross history of the Cooks resembles that of other, better-known reef-capped Pacific volcanic cones known to have been initia in the early Tertiary.