Postnatal development of vocalization and growthn Scotophilus kuhlii

This study investigated the development patterns of vocalization and growth in the lesser Asiatic yellow house bat, Scotophilus kuhlii. By further controlling the rearing environment of twins, the differences in the development patterns between the maternal-cared and hand-reared juveniles were also examined. The purposes of this study were to investigate the development of echolocation calls and relevant factors, to speculate if the morphology and vocalization of the hand-reared juveniles, abandoned in the wild, could develop the same with those of the maternal-cared juveniles, and finally to quantify the postnatal growth rate which could be applied to determine juveniles’ age in the wild. Results showed that isolation calls of Scotophilus kuhlii were primarily consisted of single notes with multiple harmonics and, in addition, were the main calls emitted by the maternal-cared juveniles until day 12, gradually followed by the precursors of echolocation calls. After the age of 20 days, isolation calls were rarely recorded again. The maximum frequencies of the fundamental and second harmonics of isolation calls increased with age though the minimum frequencies kept consistent. The pulse duration, inter-pulse interval and number of harmonics decreased. On the other hand, the development of precursors of echolocation calls showed increases in both the maximum and minimum frequencies of the fundamental and second harmonics, as well as bandwidth and sweep rate. At the same time, the pulse duration and number of harmonics decreased. Calls of newborn Scotophilus kuhlii revealed individual and family signatures which became more obvious with growth of age. Body mass and forearm length both increased linearly until the age of 21 days; subsequently, the growth rate decreased. At 49 days, mean body mass and forearm length of juveniles were equivalent to 79.44 % and 95.13 %, respectively of those of adult females. Although hand-reared juveniles exhibited faster growth rates and relatively unstable vocalization, the pattern of vocal development was eventually the same with that of mother-cared juveniles. Once hand-reared juveniles were physiologically matured, their echolocation calls became similar to adults’. This study evidenced that genetic influence is one of the major factors in vocal development and individual identity; however, social learning also acts as an important element to facilitate the development.