Studies were made of the shape, volume and depth below ground level of hibernation cavities used by free-living and captive edible dormice, Glis glis (Linnaeus, 1766). Most of the cavities (77 out of 83) were occupied by a single animal. Sixty of them had a characteristic oval shape and were analysed in detail. The volume of cavities in free-living dormice ranged from 429 cm3 to 1174 cm3 (median = 670 cm3, Q1 = 605.5 cm3, Q3 = 855 cm3, N = 17) and in captive animals from 293 cm3 to 2211 cm3 (median = 837 cm3, Q1 = 571 cm3, Q3 = 1055 cm3, N = 43). No correlation between body mass of hibernating dormice and volume of their cavities was found. A tendency for male cavities to be larger than female ones was evident, although the differences were not statistically significant. Comparison of volumes of cavities made by free-living versus captive dormice, as well as captive adults versus subadults also did not reveal significant differences. Cavities of free-living dormice were found between 18 and 70 cm underground (median = 30 cm, Q1 = 25 cm, Q3 = 40 cm).
In order to identify population trends in Barbastella barbastellus in Poland we summarised results of long-term winter bat counts conducted between 1985 and 2004 in seven of the most important hibernacula of the species. The results show an upward trend in four of the sites while in the remaining four no trend was found. The numbers of barbastelles in Poland seem stable or even increasing. In Central Europe the species is not threatened as seriously as it is in Western Europe.