A trial wild-wild translocation of the critically endangered grand skink Oligosoma grande in Otago, New Zealand
The in situ management of the critically endangered grand skink Oligosoma grande currently hinges on the on-going health of a single large sub-population at Macraes Flat, Otago. Given its vulnerability, it was considered desirable to establish additional sub-populations to ensure the long-term survival of the species. A spatial meta-population simulation of grand skinks at Macraes Flat suggested that this could be facilitated by the translocation of grand skinks into areas of predator protected habitat. Areas identified by modelling as suitable translocation sites were ground-truthed by an experienced survey team in 2008. In October 2009 we began a translocation trial. We moved nineteen grand skinks from three locations to the translocation site. The founder population was made up of ten juveniles and nine sexually mature grand skinks. Seasonal estimation of persistence and abundance using a photographic re-sight methodology allowed the short- and medium-term performance of the translocation to be assessed. High initial persistence rates suggested immediate homing was not a factor of concern. After one year, all translocated juveniles had persisted, but only four of the original nine adults remained at the release site. While the loss of adults was to some extent offset by the birth of the young-of-the-year (total skinks start: n = 19, finish: n = 20) there was a moderate loss of ~ 10% in terms of the population’s expected reproductive value. Overall, we viewed the outcome as favourable and on that basis undertook a follow up translocation.