 They emerge to feed less than an hour after sunset, and fly continuously through a relatively small area, rarely travelling more than from their roost.Echolocation in banana pipistrelles consists of steep, frequency modulated calls lasting four or five milliseconds, with a dominant frequency of about 43 kHz.Males also make longer calls with up to eight syllables when encountering other males; sometimes two individuals may engage in ultrasonic vocal 'duels' lasting up to twenty minutes and concluding with a chase through the air.