A contribution to the population ecology of Nyctalus noctula (Mammalia: Chiroptera)

From March to October colonies of Nyctalus noctula were found in hollow trees where also the reproduction takes place; winter colonies in trees are evidenced by oldish material. In buildings these bats were found throughout the year with the exception of June and July, and they do not reproduce there. One winter colony was found in a crack in a rock. According to the authors' material and according to data in literature the relation of different components of populations to different types of shelters is evaluated as well as the behaviour of N. n. in their hunting grounds. In Central Europe all females and most of the males mature at the age of about 3 months, i. e., immediately after finishing their growth. Most females older than 1 year have 2 young and the average number of young per one grown-up female is 1.8. The sex ratio at birth is 1:1 and is probably also maintained later on. The young are born from mid-June till early July and nursery colonies disintegrate in August. Old females as well as those born in that year move to mating quarters to territorial old males. The males of that year do not mate and in juvenile colonies they gradually exceed the females in number. In October at the latest the summer shelters are left till March or April. Males prevail in all winter samples from Western and Central Europe; the possible causes of this phenomenon are being discussed. The average population density in the summer season, found in two areas of the optimum habitat, is 0.32 individuals per ha. Although originally a forest species, N. noctula has managed to adapt to the civilization pressure and in places it exhibits a trend towards a hemisynanthropic way of life.