Use of the single rope access technique reveals habitat use patterns for the elusive Erebia christi (Lepidoptera: Nymphalidae)

In this study we apply a new monitoring technique for butterflies in order to get more insights into the habitat use patterns of Erebia christi Rätzer 1890 (Nymphalidae: Satyrinae). This European endemic is a rare and very localized butterfly species, found alongside steep slopes in a restricted area in the Alps, at the border between Italy and Switzerland. Even though it was discovered almost 140 years ago, captivating the interest of many lepidopterists, there are still several aspects about the biology of E. christi that are not fully known. We selected two monitoring sites in Veglia–Devero Natural Park, Italy and tested whether E. christi was more likely to use rocky, almost vertical slopes than other types of habitat. Since this habitat was almost inaccessible to humans, we used the single rope access technique, in which field operators rappelled down the slopes to explore the rock faces. We demonstrate that the main characteristics of the typical habitat of E. christi are indeed very steep rock faces with grassy ledges where Festuca sp. plants are present. We also show that, E. christi is more abundant than it was previously thought, with populations that could probably be structured in a metapopulation system. Long-term monitoring with the rope access technique could represent an optimal method to provide key insights into the biology and ecology not only of E. christi but of other butterflies that use similar habitats. Finally, we propose the upgrading of its IUCN category from Vulnerable to Endangered at European level. Implications for insect conservation Our findings demonstrate how appropriate, long-term monitoring can contribute to improve the scarce knowledge of the ecology of an elusive species, and to devise informed proposals regarding the management and protection of populations, especially for species of conservation concern.