Roosting activity budget of the southern bent-wing bat (Miniopterus schreibersii bassanii)

Abstract

The roosting activity budget of the southern bent-wing bat (Miniopterus schreibersii bassanii) was observed using remote-controlled infrared-illuminated video-cameras. Bat activity was assessed using scan sampling, conducted in 98 two-hour observation blocks, with 605 scan samples (each of ~2.5-min duration) being collected. Activity was divided into three categories: 'at rest', 'grooming', and 'active' (including flying off). Bats spent an average of 62% of their time 'at rest', 16% 'grooming', and 22% 'active'. Bat activity was significantly influenced by time of day, the cave chamber that was occupied, the vertical location of the bats on the cave wall, and the type of cluster formed by the bats. During the day bats spent most time 'at rest' (overall mean 78%) compared with other times (overall means 43–54%). Levels of flight and 'activity' (relative to 'at rest') were significantly lower during the day than at other times. Bats on the walls of the maternity chamber, where the temperature was highest, spent less time 'at rest' (overall mean 51%) than did bats on the walls of cooler chambers (overall means 73–86% of time). Bats in the maternity chamber spent significantly more time 'active' and 'grooming' (relative to 'at rest') than did bats in other chambers. Microclimatic conditions within the cave environment appear to significantly affect the activity of bats whilst at roost.