An estimate of population density of the fat dormouse Glis glis, movement and nest cohabitation in two types of forests in the Transylvanian Plain (Romania)

Spatially explicit capture-mark-recapture data, obtained by regular nestbox checks during two summer seasons (2006, 2007) were used to estimate population density of the fat dormouse (Glis glis) in one oak (Quercus robur) and one hornbeam (Carpinus betulus) dominated forest in the Transylvanian Plain, Romania. The number of captured dormice was positively correlated with the number of occupied nestboxes, although between 10 % and 50 % of all nestboxes were shared by 2–6 individuals. The percentage of shared nestboxes and number of individuals found within them varied. Dormice tend to aggregate in nestboxes during the mating season, and almost all shared nestboxes containing more than two individuals (males and females) were encountered during that period. Dormice were more solitary in July and august, when females gave birth, but communal nesting was uncommon in our study sites. The fat dormouse had higher densities in the oak forest than in the hornbeam forest (11.32 ± 1.46 vs. 4.81 ± 0.70 ind./ha), and also the average distance moved was shorter in the oak forest. The maximum distance moved was 150 m in the oak forest and 250 m in the hornbeam forest, but here fewer than 5 % of the distances recorded were greater than 150 m, showing high nest site fidelity .