Immediate and long-term effects of translocations on breeding success in Takahe Porphyrio hochstetteri

Abstract

Translocations of threatened species play an increasingly important role in conservation management. However, few studies have examined what effects, if any, the translocation process itself (i.e. catching, handling, confining, transferring and releasing an animal into an unfamiliar environment) has on subsequent breeding success. Takahe Porphyrio hochstetteri living on offshore “predator-free” islands in New Zealand are a model system for examining such effects because pre-breeding birds have been frequently translocated between established island populations before they pair up and breed at 2-3 years of age. We postulated that “translocated” breeders (i.e. breeders that had been raised on another island) would delay first breeding attempts and/or have lower reproductive success compared with “resident” birds (i.e. bred on the same island that they were raised). The results indicated that translocated birds did not delay breeding and had similar mean hatching and fledging success as resident pairs in their first breeding season and subsequent seasons combined. The results suggest that at least for large or long-lived birds such as Takahe, the effects of any stress from the translocation itself, or the release into an unfamiliar environment, might be either short-lived or not significant enough to hinder subsequent breeding success. We recommend that further research be carried out on other species to determine the baseline effects, if any, of translocations, so that they can be taken into account when considering other determinants of translocation success such as habitat suitability, number of individuals and timing of releases.