Abstract
Aotearoa New Zealand (Aotearoa) has an incredibly high diversity of lizard fauna, many of which (83%) are classified as ‘Threatened’ or ‘At Risk’. The high number of lizards classified as ‘At Risk’ or higher is due to the introduction of invasive mammalian predators and habitat loss. Conservation management of lizard populations focuses on mitigating these pressures, including translocations, predator control and habitat protection/restoration. However, effective conservation management requires an understanding of the study species’ ecology and behaviour, how different pressures cause declines in the study species specifically and the best methods and tools for mitigating these declines. One such species needing urgent conservation action is the Kapitia skink (Oligosoma salmo).
Kapitia skinks are classified as ‘Nationally Critical’ and are only know from to Chesterfield (West Coast), Aotearoa. This small coastal population is at risk of predation and habitat loss due to climate change and coastal erosion. Individuals from a captive population of Kapitia skinks at Auckland Zoo were reintroduced into pens made from a new experimental, cost-effective ‘leaky’ fence design inside and outside a predator-proof fence in a newly established Kapitia Scientific Reserve. This translocation formed the focus of my study.
The first aim of my study was to evaluate the short-term success of the translocation and the effectiveness of the experimental leaky fence design. Using artificial retreats, I monitored the recapture rates, body condition and injury rates of skinks in leaky pens inside the predator-proof fence (no mammalian predators) and outside the predator-proof fence (mammalian predators present) for five months after the translocation. Additional monitoring was carried out a year after the translocation. The translocation of Kapitia skinks was a success in the short term, as a high percentage of skinks were recaptured (82.7%), the body condition of skinks increased, and a large number of skinks were born after the translocation occurred. Recapture rates, body condition and injury rates did not differ between the leaky pens inside compared to outside the predator-proof fence suggesting they were effective in protecting the Kapitia skinks in the short-term. Therefore, the leaky fence design could potentially be considered a cost-effective form of mammalian predator exclusion fencing for future translocations. I found that males and larger skinks use artificial retreats more often. I also found that weather conditions (daily minimum temperature, atmospheric pressure, sunshine and hourly radiation) affect the detectability of skinks when using artificial retreats as a monitoring method. Knowing how Kapitia skinks use artificial retreats and the capture biases associated with this monitoring method is important to optimising sampling. It is also important to be considered when interpreting the results gathered from artificial retreats in the translocated population, but especially in the wild population, where the number of skinks in each demographic is unknown.
The extent of the Kapitia skinks’ habitat use and preferences is largely unknown, but they possess a unique prehensile tail which could indicate they have arboreal tendencies. The second main aim of my study was to evaluate the habitat use and preferences of Kapitia skinks and whether they were found arboreally. I used artificial retreats, tracking tunnels, fluorescent powder tracking and camera trapping to determine what type of habitat (grass, shrubs or trees) Kapitia skinks used. Kapitia skinks were exclusively found in grass habitats and showed a strong preference for grass habitats in the open that lacked a canopy. I did not detect any arboreal behaviours. My results help inform how the Kapitia skink habitat is managed, what habitat types should be explored to look for more skinks, which habitat is most important to conserve, and potential areas for future translocations.
By determining that the translocation into the leaky fences was a short-term success, that skink demographics use artificial retreats differently, that weather affects the detectability of skinks when using artificial retreats and that Kapitia skinks prefer open grass habitats, some light is shed on the ecology and behaviour of the Kapitia skink that was previously unknown. By having a deeper understanding of the behaviour and ecology of Kapitia skinks, the future conservation management of both the translocated and wild Kapitia skinks can be more informed.