Increased cave use by butterflies and moths: a response to climate warming?

Abstract

Between 2015 and 2019, the list of Lepidoptera from “cave” habitats (i.e., proper caves, rock shelters and artificial subterranean structures) in Austria grew from 17 to 62 species, although the effort of data collection remained nearly constant from the late 1970s onwards. The newly recorded moths and butterflies were resting in caves during daytime in the the warm season, three species were also overwintering there. We observed Catocala elocata at 28 cave inspections, followed by Mormo maura (18), Catocala nupta (7), Peribatodes rhomboidaria, and Euplagia quadripunctaria (6). More than half of the species have been repeatedly observed in caves in Austria or abroad, so their relationship with such sites is apparently not completely random. Since the increase of records in Austria coincided with a considerable rise in the annual number of hot days (maximum temperatures ≥30°C) from 2015 onwards, we interpret the growing inclination of certain Lepidoptera towards daytime sheltering in caves as a behavioral reaction to climate warming.