Monitoring presence, abundance and survival probability of the stag beetle, Lucanus cervus, using visual and odour-based capture methods: implications for conservation

A capture-mark-recapture study on the threatened saproxylic beetle Lucanus cervus was carried out in a chestnut (Castanea sativa) woodland located in northern Italy, using visual encounter surveys (VES) as well as aerial flight interception traps and pitfall traps (PT), both of which were baited with different odour lures. In total, 111 males and 25 females were captured, and VES was by far the most efficient method, accounting for 93 % of first captures, and 95 % of all captures. Stag beetles were not significantly attracted to any tested odour, and many PT were damaged by wild boars (Sus scrofa). Flying males were the most frequent adults observed during the season. The use of a net is necessary to capture the stag beetles, in order to evaluate the population parameters and to assess the local status of threat for the species. Capture data revealed that body size (i.e. body weight and elytron length) influences the survival probability of stag beetles, showing a lower survival probability for larger males. Felt-tip pen marking on the ventral sclerites of head and pronotum is a reliable and long lasting method for marking beetles, as proved by the use of an independent marking procedure with a small drill. Assessing the presence and threat status of L. cervus across Europe is urgently needed, and with no efficient odour-based strategy available, collection of adult beetles, dead or alive, by VES is the most reliable way to monitor this emblematic species.