AUTOMATIC REGISTRATION OF BAT ACTIVITY THROUGH THE YEAR AT MONSTED LIMESTONE MINE, DENMARK

Bat activity was recorded automatically the year round with a double l ight barrier al the exit of the mine. The method yields quantitative d ata without interference on the natural behaviour of the bats. Four pe riods are defined: 1) Hibernation period (November-late March), with v ery low activity. 2) Departure period (late March-mid May), with a mar ked peak in April, and a second small period of departure in the first half of May, representing the departure of Myotis brandtii. 3) Summer activity period (mid May-mid June), when a large number of M. daubent oni males use the mine as some sort of transitional roost. 4) Arrival period (late July-November), consisting of two periods with a gradual transition: End of July through August with a balance between in- and outflights, and September-November with a net flux into the mine indic ating the start of hibernation. The species could not be separated, bu t this was a minor drawback as the gross number and behaviour of the d ifferent species was known in outline, studied by other methods. 80-90 % are M. daubentoni.