Evaluating log piles as stag beetle conservation measure

Like many other anthropogenic habitats, log piles are mainly built in urban areas as a species-specific conservation measure for the European stag beetle (Lucanus cervus). As little is known about the success of this measure, we aim to study their success and longevity based on 100 small log piles that were followed up with emergence traps. Log piles were colonised the first year of building and beetles emerged up to 13 years later, with most beetles emerging after eight years. Overall, 67% of the log piles had emerging beetles: Quercus robur log piles (80%) were more successful than Fagus sylvatica (58%) and Populus x canadensis (50%). Overall, 177 ± 5, 131 ± 5 and 89 ± 5 beetles emerged per 1 m³ wood used in the log pile for oak, beech, and poplar respectively, but tree species had no effect on the size of the beetles. The emergence phenology was explained by a degree-day model with 6.6 °C as baseline temperature, predicting start and end of the emergence around 620 and 810 accumulated degree-days.