Spatial organisation of European badger (Meles meles) in northern Italy as assessed by camera-trapping

Italy is amongst the European countries for which data on badger Meles meles numbers and variation in population size are still too few to assess its conservation status. With the aim of estimating badger density in northern Italy, between February 2013 and March 2014, we extensively surveyed an isolated hilly area for badger setts and assessed group size by monitoring a sample of setts by two sessions of camera-trapping. The size and shape of each home range were assessed from main sett coordinates using the Dirichlet tessellation method. Then, assuming that badger home ranges tend to be delimited by hard boundaries or geographical features, the polygon shapes were successively modified by hand to draw more realistic home ranges. The overall trapping effort was 754 camera trap-days. The number of badger individuals sharing the same sett/entrances was recorded, distinguishing individuals based on the time and hole of emergence and, possibly, tail patterns. Groups consisted of two to four adult individuals, averaging 2.75 badgers/group. Camera-trapping proved to be a cost-effective and time-saving method. Depending on the method used to draw home ranges, in the study area, sett density was 0.34–0.51 sett/km2, whilst badger density was 0.93–1.4 adult individuals/km2. Both sett and badger densities were rather high with respect to most available data for continental Europe. As badger mean group size seems to be rather constant throughout both hilly and plain areas of the River Po basin, sett density may be used as an accurate estimator of badger density throughout this wide area.