Aspects of the ecology of serotine bats (Eptesicus serotinus, Schreber 1774) in contrasting landscapes in southwest Germany and Luxembourg
Aspects of the ecology of the serotine bat (Eptesicus serotinus) were studied at colonies in Southwest Germany and Luxembourg. Maternity roosts of serotines were situated in slate-covered roof-spaces of buildings, offering a wide variety of microclimates which allow the bats to remain there throughout the period of pregnancy and lactation. The inferred gestation length was on average 52 days. Gestation length was not directly related to the temperature inside or outside the roost. The average data of birth in the study region is 17th June with a mean birth period of 14 days. The juveniles emerge from the roost for the first time after a mean of 36 days. The dispersal of the colony starts with this event and the last bats were observed to emerge in the first week of October. The number of emerging juveniles never corresponded to the number of emerging females. This fact and the repeated observation of more serotines re-entering the roost during the night than previously emerging, lead to the conclusion that a colony is part of a metapopulation. The mean emergencies time of the bats is closely related to sunset. Emergence time is adjusted to the availability of preferred prey taxa and to light intensity. Mortality of juveniles is increased by lasting inclement weather. Although habitat availability differed markedly between the study areas, habitat use by the two colonies was very similar. The most important habitat type used was woodland and its edges adjacent to grassland, followed by permanent grassland, then settlement areas. Calculation of habitat selection by means of compositional analysis revealed a preference for settlement areas over woodland and over grassland. Arable land was always significantly avoided. Radio-tracked serotine bats of both colonies flew similar maximum distances to foraging sites (4.5 km) and had similar average home range sizes (4.6 km2).