Life in the slow and high lane: ecology of an alpine gecko (Mokopirirakau “Cascades”) in the Southern Alps | Kā Tiritiri o te Moana, Aotearoa New Zealand

Alpine regions worldwide support diverse, endemic, and specialised fauna, yet knowledge of the basic ecology of many species is lacking and urgently required for management. Aotearoa New Zealand’s lizards (geckos and skinks) are no exception: of at least 33 species that occur in the alpine zone, ≥ 90% are currently Threatened or At Risk of extinction. Here, we focus on the Cascade gecko: a cryptic and viviparous species found in the Southern Alps | Kā Tiritiri o te Moana in the South Island. To improve understanding of its ecology (distribution, habitat use, emergence behaviour, demography, life history, and female reproduction), we collated varied records spanning 50 years and sampled geckos at two alpine sites in South Westland over 46 days, January 2019–March 2023. Of 470 individual geckos reported from 16 sites since 1974, the vast majority (92%, including 334 from our study area) were from the alpine zone. Surveys for lizards (geckos, skinks, or both) in South Westland revealed more geckos with significantly greater catch-per-unit-effort than in Fiordland, possibly due to differences in gecko densities, lithology, terrain, and/or focal taxon surveyed. Consistent with other nocturnally-foraging gecko species that live in cool-climates in southern New Zealand, we found evidence for cryptic basking, female-larger sexual-size dimorphism, adult- and female-biased captures, and extended pregnancies. Females in our study area appeared to have summer-to-early-autumn births, pregnancies of ≥ 2 years and triennial reproduction, yielding one of the lowest reproductive outputs reported for female reptiles worldwide. Climate change and predation by introduced mammals are inferred as the main threats to the species. Due to their extremely slow life histories, alpine geckos will require prolonged time-frames for population monitoring and management.