INTRASPECIFIC RESPONSES TO DISTRESS CALLS OF THE PIPISTRELLE BAT, PIPISTRELLUS-PIPISTRELLUS

Responses of the vespertilionid bat Pipistrellus pipistrellus to five recently caught conspecifics confined to a wire-mesh cage, at distance s of 50 and 5 m from their roosts, were recorded on 12 separate evenin gs at three roosts during pregnancy and lactation. When bats were conf ined 50 m from their roost, an almost 20-fold increase in the number o f bats that passed across an open site around the cage was recorded an d the strength of response (number of bat passes) increased with time. When the bats were 5 m from the roost there was an 80-fold increase i n bat activity above the cage. Playbacks of recorded distress calls pr oduced by single hand-held bats resulted in a more than three-fold inc rease in bat passes, but the response waned rapidly. The distress call s of recently caught P. pipistrellus were generally similar to those o f individuals from the same colony held for longer in captivity, and d ifferences in distress calls between two of the three colonies studied probably reflect differences in the physiological states of recorded bats, rather than the existence of colony-specific vocalizations. Dist ress calls probably function in attracting conspecifics which perform mobbing behaviour as an anti-predator response. (C) 1998 The Associati on for the study of Animal Behaviour.