Impact of rat species in Ouvea and Lifou (Loyalty Islands) and their consequences for conserving the endangered Ouvea Parakeet

This study assesses the impact of Pacific Rat Rattus exulans predation on the endangered Ouvea Parakeet Eunymphicus cornutus uvaeensis and investigates the feasibility of translocating this bird to the island of Lifou (despite the presence of Ship Rat R. rattus). A rat trapping campaign, conducted from July 1995 to October 1996 in the forest of Ouvea and Lifou (Loyalty Islands, New Caledonia, South-west Pacific), confirmed the presence of Pacific Rats in Ouvea and both Pacific and Ship Rats in Lifou. Population dynamics, sex ratio, age structure and diet of both rats were investigated. An experiment, using quail eggs in natural tree holes during the main bird breeding season, in Ouvea in 1994 and in Ouvea and Lifou in 1996, compares the nest predation rate between these islands. Mayfield's estimator for a 21 day theoretical incubation period gives a survival rate of 0.80 and 0.99 in the two experiments in Ouvea but only 0.22 in Lifou. Most of the difference in egg survival observed between the islands appears to be related to the presence of Ship Rat in Lifou, while the difference in the two experiments in Ouvea may estimate the effects of trapping. The study shows that Lifou is not a suitable place for translocating Ouvea Parakeets, unless active habitat management is carried out to protect this bird against Ship Rats. The value of low intensity rat control in Ouvea immediately prior to the parakeet breeding period is also suggested.