Eradication

While eradication projects on large islands require substantial funding and a high level of technical and logistical support, projects on small islands are much simpler and can achieve success with much less funding and outside assistance. The Pacific has thousands of such islands that can contribute to significant biodiversity outcomes. The purpose of this guide is to assist the practitioner in removing invasive rodents from small islands (less than 20 hectares) where access to all parts of the island is possible.

To enhance their conservation value, several hundred islands worldwide have been cleared of invasive alien rats, Rattus spp. One of the largest projects yet undertaken was on 43 km2 Henderson Island in the Pitcairn group, South Pacific, in August 2011. Following massive immediate mortality, a single R. exulans was observed in March 2012 and, subsequently, rat numbers have recovered. The survivors show no sign of resistance to the toxicant used, brodifacoum.

The Island of Suwarrow and its surrounding waters was declared a National Park in 1978 under the Conservation Act 1975. The legal opinion sought in 2001 clarifies that Suwarrow is Crown Land. Today, Suwarrow is under the jurisdiction of the National Environment Service (NES) since 2003, for the primary purpose of conserving, preserving, protecting and managing the natural resources of Suwarrow.

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.

The Ministry of Environment, Lands and Agricultural Development (MELAD) has received funds through

A programme to eradicate two species of myna from Kiribati was carried out between November 2014 and November 2015 by staff of the Environment & Conservation Division, Ministry of Environment, Lands and Agricultural Development with funds through the regional GEF-PAS Invasives project coordinated by UNEP and SPREP, assisted by international consultant Dave Butler.

Invasive rodents are successful colonists of many ecosystems around the world, and can have very flexible foraging behaviours that lead to differences in spatial ranges and seasonal demography among individuals and islands. Understanding such spatial and temporal information is critical to plan rodent eradication operations, and a detailed examination of an island’s rat population can expand our knowledge about possible variation in behaviour and demography of invasive rats in general.

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.

As part of the Isles of Scilly Seabird Recovery Project, and directed by Wildlife Management International Ltd, the eradication of brown rats (Rattus norvegicus) from the inhabited islands of St Agnes & Gugh, Isles of Scilly was completed between October 2013 and April 2014 with the assistance of volunteers, and staff from the Royal Society for the Protection of Birds, Isles of Scilly Wildlife Trust and Natural England. Bait stations with cereal-based wax blocks containing bromadiolone at 0.005% w/w were established on a 40–50 metre grid over the island.

This essay offers a 25-year overview of eff orts to remove Pacific rats (Rattus exulans) from the four islands of the Pitcairn group. Following the 1991–1992 discovery that rats were severely reducing breeding success of gadfly petrels (Pterodroma spp.), Wildlife Management International proposed eradication. Eradication success was achieved using ground-based baiting on the small atolls of Ducie and Oeno in 1997, and there is now evidence of petrel recovery on Oeno, but two eradication attempts on inhabited Pitcairn (1997 and 1998) failed.