Climate change is exerting significant impacts on ecosystems worldwide, with alpine regions being particularly vulnerable. Increased global temperatures have reduced available habitat for alpine species, whilst enabling generalist species to encroach higher into alpine ecosystems. Alpine fauna are relatively poorly understood, particularly in terrain that is difficult for humans to survey. This is especially true for New Zealand’s alpine lizard species. Knowledge of alpine species is further limited by a paucity of survey techniques that are widely applicable in this environment. Current techniques can be disruptive to the composition of alpine habitats and are limited to places that can be safely accessed on foot. Novel survey techniques are needed to enhance our understanding of alpine ecology in remote and inaccessible terrain.

Drones have emerged as a non-invasive tool for surveying fauna in remote or inaccessible terrain, but there has been limited research to date on their applicability to surveying small animals. Alpine lizards of New Zealand provide an ideal system for exploring novel survey techniques because there is a wide range of species that occur in both accessible and inaccessible locations and many of these species are threatened and of conservation interest. I build on research demonstrating the potential of drones for surveying alpine lizards by evaluating: (1) how closely a drone can approach five alpine lizard species in three habitat types (scree-rockfield, talus-rockfields and tussock grassland); and (2) the effectiveness of drone surveys compared to traditional systematic visual searches for several alpine lizard species across three habitat types.

The drone (model: DJI Mavic Air 2) was able to approach within 0.1-2.5 m of all lizards (mean = 0.77 m) before triggering a flight response. Each species showed differing tolerances to the presence of a drone. Nevis skinks (Oligosoma toka) were the most tolerant to the drone, whereas scree skinks (Oligosoma waimatense) were the least tolerant (i.e., fled earlier than other lizard species when approached by a drone). The high tolerance of tussock-dwelling Nevis skinks to the presence of a drone is likely due to reduced predator wariness caused by higher vegetation cover in tussock-grassland, making them less conspicuous to potential predators. The opposite is true for individuals in open, non-vegetated terrain such as scree skinks inhabiting rockfields. This was supported by the finding that drones were best able to approach skinks within tussock-grassland (mean = 0.5 m) and were able to approach less closely to individuals within scree and talus-rockfield (mean = 0.9 m for both). Systematic visual searches outperformed drone surveys in all habitats accessible to human observers. However, drones were relatively effective in talus habitats, demonstrating their potential utility in inaccessible rocky alpine habitats.  Additionally, lower average wind speed and higher temperatures allowed the drone to approach skinks more closely.

Improvements to drone technology (e.g., zoom function and higher camera quality) are likely to enhance drone survey performance in ecological research. Future studies should investigate drone use for surveying arboreal lizards, allowing researchers better access to areas of high canopy where current survey methods are ineffective.