Alpine skinks persist 12 months post-translocation with no initial evidence of weka predation

Many of Aotearoa | New Zealand’s lizards are threatened, and translocation to offshore islands where introduced mammalian pests are absent is one option to increase species’ security. However, the high densities of native avian predators of lizards that occur on some offshore islands are a potential barrier to translocation success. This threat is amplified for obligate alpine lizards, as few offshore islands have an alpine zone. Off the coast of Fiordland, Secretary Island has alpine habitat and is largely mammal free, with only a suppressed population of stoats (Mustela erminea) present. It has been identified as a potential translocation site for the critically endangered Sinbad skink (Oligosoma pikitanga), but the resident weka (Gallirallus australis) population poses a potential threat. Mahogany skinks (Oligosoma aff. pluvialis “mahogany”) co-occur with Sinbad skinks, but are less endangered (classified as At Risk – Declining), and were identified as a surrogate species to first attempt to translocate to Secretary Island as a proof-of-concept. In January 2023 and February 2024, a total of 40 mahogany skinks were translocated from Sinbad Gully to Secretary Island. We used trail cameras, visual observations, and tracking tunnels to monitor the mahogany skink population at their release site for a total of 177 days. We investigated whether the resident weka preyed on the translocated skinks, measured skink dispersal from the release site, and compared temporal activity of weka and skinks. Weka were not witnessed preying upon skinks. Skinks persisted at the release site for at least one year, and some dispersed at least 25 metres away. Skink detections significantly increased with temperature. In relation to time of day, daylight type, or temperature, peak activity levels of skink and weka did not overlap. These results imply that we can be cautiously optimistic about habitat viability and any future translocation of Sinbad skinks to Secretary Island.