Returning tuatara (Sphenodon punctatus) to the New Zealand mainland

Abstract

Conservation on mainland New Zealand is defined by pest control programs and predator proof fencing, which have arisen to combat the suite of mammalian pest species now occurring there. Translocations are an integral part of species conservation and ecological restoration of mainland islands. Investigation into factors that influence translocation success, especially in the presence of managed levels of predators, is an emerging area of research. Tuatara (Sphendon punctatus), a ground dwelling reptile, were forced off the mainland of New Zealand and onto offshore islands with the introduction of mammalian predators. A translocation of 70 adult tuatara from Stephens Island, western Cook Strait to Karori Wildlife Sanctuary, Wellington, New Zealand, in December 2005 allowed investigation into whether tuatara can co-exist with controlled levels of mice by evaluating survival and condition of the founder population. Sixty tuatara were released in a mouse-proof exclosure within the sanctuary and ten outside this, in the main sanctuary, in the presence of mice. Survival was high with 80% of the tuatara released being sighted during the year post-release, and more are likely to have survived. Individuals of both sexes showed increases in mass. Adult tuatara are able to survive in the presence of controlled levels of mice, however the survival of juveniles and eggs requires further investigation. Translocation of individuals in groups with known neighbours did not reduce post-translocation dispersal compared to those in randomly assorted groups. Territory sizes were significantly larger than those on Stephens Island. Juveniles made use of the gaps created within the dense population on Stephens Island by removal of adults for translocation, and began establishing territories. Whether they are able to defend these territories long-term against larger males is uncertain. The threatened tuatara tick (Amblyomma sphenodonti) was also translocated with its host, the tuatara. Ticks are unlikely to have survived the translocation. By one year post release, few tuatara still had ticks, and numbers of ticks on tuatara were extremely low. Nymphs detached prior to the end of the study, but reattachment opportunities are reduced in the translocated population due to reduced density of tuatara and dispersal away from burrows. Success of translocations of tuatara to the mainland will be contingent on reproductive success in the presence of mice. Protocols for translocations that reduce subsequent dispersal are desirable for tuatara reproduction, and for the reproduction and conservation of tuatara ticks, however taking animals with known neighbours is not a time or cost effective way to achieve a reduction in dispersal.