Comparative success of two sampling techniques for high-altitude Alpine grassland reptiles under different temporal designs

Monitoring of wildlife populations is essential for their conservation and requires a carefully chosen methodology. We compared survey effectiveness of reptiles using coverboards and visual encounter surveys in two study sites in the Italian Alps with similar habitats and reptile communities. The two sites shared similar methodologies, cover boards and visual encounter surveys (VES), except for the temporal approach, with one employing a long-lasting monitoring scheme and the other operating on a much shorter time-frame. Coverboards were placed two years before the beginning of the monitoring in the first site, while they were installed only for ten days and then removed each year in the second site. Similarly, VES were spread across the whole reptile activity season (May-September) in the first site, while conducted over nine consecutive days in the second site. Although the observation rate of any species was mainly associated with its relative abundance, reptiles preferred long-established coverboards and all three species present (Zootoca vivipara, Anguis veronensis and Vipera berus) were found underneath them. Only Zootoca vivipara used recently installed ones. On the other hand, short-term daily visual encounter surveys led to a much higher observation rate of Z. vivipara than those spread over the entire season. Our results suggest that coverboards may provide a valuable monitoring tool for reptiles when projects are conducted over long periods. Conversely, when only short-term assessments are possible, no real difference exists between the two methods and observation rate is more influenced by the species abundance than by the chosen method.