The communication sounds of the pallid bat, Antrozous pallidus, wre studied in the laboratory. Adult pallid bats communicate via four main types of sound emissions: directives, squabble notes, irritation buzzes, and FM orientation pulses. Newborn bats emit only isolation calls. These calls evolve into the adult directive by the twentieth day. Ultrasonic orientation pulses do not appear until 7--9 days postnatally. These appear to arise de novo or may be derived from a shortened isolation call. Irritation buzzes and squabble notees are first emitted at one and two weeks of age respectively, without an apparent precursor. Mother bats nurse only their own infants and recognize them on the basis of auditory and olfactory cues. An apparent vocal signature is present in the temporal patterning of frequencies in the isolation call, and this may function in individual recognition.