Departure dynamics of Myotis daubentonii (Kuhl, 1817) (Mammalia, Chiroptera) from their hibernaculum

Bats were netted four times a week over a period of 3 years (1992-1994). Ea ch evening, for 5 hours, beginning at sunset in March and April they were n etted in the entrance of a bunker of Fort I in Poznan (western Poland). Ind ividuals that wintered for the first time in their lives (subadults) were d istinguished from the older ones (adults) on the basis of the black chin sp ot. For each day of observation the frequency coeficient (number of individ uals from certain class/all individuals) was calculated. In all seasons onl y adult females showed a similar pattern of decreasing frequency coefficien t from the beginning up to the end of the departure (significant correlatio n only in 1992). In adult males, subadult females and suadult males, the pa ttern changed during each season. In each research season the percentage of larger body mass individuals in group of adult females increased while app roaching the end of the time of departure (significant correlation in 1993 and 1994). In adult males such a significant increase of body mass was obse rved in 1994.