The study of dispersal processes of small mammals, and especially of rodents, has a wide range of applications and until recent years there were few publications discussing the
colonisation of 'oceanic' islands by small mammals (cf. Crowell, 1986; Diamond, 1987; Hanski, 1986;Heany, 1986; Lomolino, 1986).
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
used in successful rat eradications in New Zealand, in that Pestoff 20R pellets and a network of bait stations were used.
Conditions on the island were not what was expected, the forest having been adversely affected by cyclone Waka and subsequent defoliation by caterpillars, resulting in an open forest canopy. Rats were found to be present on the island in high numbers and were breeding.
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
turtles. They also are the only offshore islands large enough and far enough offshore to be considered as refuges for several of the nation's species threatened on the larger islands by introduced mammalian pests. Such refuges have assumed greater
The impacts of house mice (Mus musculus), one of four invasive rodent species in New Zealand, are only clearly revealed on islands and fenced sanctuaries without rats and other invasive predators which suppress mouse populations, influence their behaviour, and confound their impacts. When the sole invasive mammal on islands, mice can reach high densities and influence ecosystems in similar ways to rats.
Following the incursion of rats (Rattus rattus) on Taukihepa (Big South Cape Island; 93.9 km²) off southern New Zealand in 1963, and the subsequent extirpation of several endemic species, the New Zealand Wildlife Service realised that, contrary to general belief at the time, introduced predators do not reach a natural balance with native species and that a safe breeding habitat for an increasing number of at risk species was urgently needed.
Rat eradication is a highly effective tool for conserving biodiversity, but one that requires considerable planning eff ort, a high level of precision during implementation and carries no guarantee of success. Overall, rates of success are generally high but lower for tropical islands where most biodiversity is at risk. We completed a qualitative comparative review on four successful and four unsuccessful tropical rat eradication projects to better understand the factors influencing the success of tropical rat eradications and shed light on how the risk of future failures can be minimised.