Individual variation in the structure of pup isolation calls in Mexican free-Tailed bats (Tadarida brasiliensis mexicana)

This study investigated the presence of pup vocal signatures and the ability of adult females to recognize individual pup vocalizations in Mexican free-tailed bats, Tadarida brasiliensis mexicana. Female-pup nursing pairs and pregnant females were captured from large maternity colonies in central Texas. Vocalizations of 20 pups were recorded and nine call parameters were measured spectrographically or with a spectrum analyzer. Recordings of fourteen of the pups were played back to females to determine whether females discriminate among pup calls. Univariate and multivariate analyses of the call parameters showed that pup calls are structurally distinct, suggesting that the pups have individual vocal signatures. Calls also possess qualities that suggest they are attractive in nature and easy to locate. Regression analyses show that several call parameters increase in frequency as pups age. G-tests on the vocal responses of adult females to the playbacks of pup calls showed that females did not respond differentially to their own pup's call versus another pup's call or blank tape. Possible explanations for these latter findings are discussed.