Spatial organization of the fat dormouse (Glis glis) in an oak-hornbeam forest during the mating and post-mating season

Home range (HR) size and overlap, movements, and nest site use of fat dormice Glis glis (Linnaeus, 1766) were studied by live-trapping and radiotracking in the Bialowieza Forest in north-eastern Poland. The study was conducted during a mast year of oak Quercus robur (2001) and hornbeam Carpinus betulus (2002). Average HR size measured by 100% minimum convex polygons varied from 3.6 to 7.0 ha in males and from 0.55 to 0.76 ha in females. HR size in males was significantly larger in the hornbeam mast year than in the oak mast year, which was probably due to the lower energy value of hornbeam mast. Males had significantly larger HRs and used more nest sites than females. In contrast to females, HRs of males overlapped extensively. In the mating season, core areas of males overlapped significantly more and they shared their core areas with more males than in the post-mating season. During the mating season, males were found to share nest sites with other males or with a single female. Additionally, groups of 2–3 males were observed aggregating around a female during the mating season. Our data suggest that fat dormice have a promiscuous mating system where the females are territorial, and the non-territorial males directly compete for access to receptive females during the mating season.