Habitat description and interannual variation in abundance and phenology of the endangered beetle Lucanus cervus L. (Coleoptera) using citizen science monitoring

Abstract

Conservation of threatened saproxylic beetles, which are often elusive, faces the problem of efficient monitoring. Lack of standard monitoring protocols has hindered the much needed assessment of temporal trends in phenology and abundance of the stag beetle, Lucanus cervus, and the development of landscape ecology studies. Our main objective was to illustrate how transects at dusk, implemented by means of citizen science projects, could provide reliable information on habitat characterization and population trends in the stag beetle. Abundance and phenology was studied in a longitudinal study during 7 years in E Spain. Habitat characterization was studied in a transversal study in N Spain. Our longitudinal study detected between-year variation in phenology (up to 4 weeks in peak activity) and abundance (twofold among maxima and minima recorded). In addition, both our longitudinal and transversal studies detected variation among sites in abundance, that was related to rainfall in the previous winter. In this sense, transects at dusk were a suitable monitoring method. Abundance variation could not be related to habitat variables. Nevertheless, we provide one of the few descriptions available of stag beetle habitat at scales of tens to hundreds of meters. Forest was the dominant vegetation in a 25 m buffer around the transects. However, open natural vegetation prevailed in a 1000 m buffer around the transects, indicating strong habitat fragmentation. We conclude that transects at dusk are easily implemented in citizen science projects and provide much needed information about temporal trends in abundance, phenology and habitat description of stag beetles.