Rattus exulans

The islands of Nu'utele and Nu'ulua have been identified as highly significant sites for conservation in Samoa. They hold large populations of species currently found nowhere else in the country' including threatened land-birds, seabirds and nesting

Invasive vertebrates are a leading cause of the extinction on islands and rats (Rattus spp.) are one of the most damaging to island ecosystems. Methods to eradicate rates from islands are well established and there have been over 580 successful eradications to date. Increasingly, rat eradications are being implemented on tropical islands, a reflection of the need to protect the threatened biodiversity in the tropics. Yet rat eradications on tropical islands fail more frequently than those in temperate climates.

Late is an isolated and uninhabited island located about 55 km WSW of the island of Vava'u, in the Kingdom of Tonga. Late supports a tropical broad-leaf forest ecosystem, one of the most threatened ecosystem types in the world and one of the best remaining tracts of diverse native forest in Tonga. Owing to its relatively unmodified forest communities, Late is also a global stronghold for two IUCN listed species of bird, one native mammal, and six species of reptile.

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.

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.

Invasive rodents have an overwhelmingly detrimental impact to native flora and fauna on islands. Rodent eradications from islands have led to valuable biodiversity conservation outcomes. Tropical islands present an additional suite of challenges for rat eradications due to unique characteristics associated with these environments. To date tropical island rat eradications have failed at a higher rate than those undertaken outside the tropics. Critical knowledge gaps exist in our understanding of what drives this outcome.

In June/July 2002 an eradication programme to remove Pacific rats from Maninita Island in the Vava'u group of the Kingdom of Tonga was initiated. The techniques used were similar to those