ONTOGENY OF TRUE FLIGHT AND OTHER ASPECTS OF GROWTH IN THE BAT PIPISTRELLUS-PIPISTRELLUS

We describe the ontogeny of pipistrelle bats Pipistrellus pipistrellus Schreber (Chiroptera: Vespertilionidae), including for the first time the development of true flapping flight. The study animals were born to a group of 20 adults taken into captivity just before parturition, and allowed free flight and association within a room designed to appr oximate external conditions. All juveniles were aged to within one day and individually marked. All adults were ringed. Comparison to wild s tudies and the application of a set of growth models to forearm and bo dy mass data gave no indication that development had been altered by c aptivity. Forearm data were best fitted by the logistic growth model a nd mass data by the 'Gompertz' growth model. Preliminary flight observ ations were followed, once the bats had become truly volant, by experi ments in a flight enclosure with stroboscopic stereophotogrammetry. As the bats aged they used slower wingbeat frequencies (scaling with age D as D--0.40), but flew faster, speed scaling with age as D-0.65. Win gbeat amplitude did not alter significantly with age, nor did the tota l mechanical power for flight, calculated by using a flight performanc e model, although the cost of transport fell as the bats grew older. T his was probably due to the improving efficiency of the wing; the deve lopment of wingspan, wing area, wing loading, aspect ratio and tip are a ratio are presented, and adaptations for reducing the energy require ments during early flights are discussed. These included a mass recess ion which occurred after the time of first flights. The flight model w as also used to explore the hypothetical flight of bats with the morph ology of neonates, and we discuss the extent of sexual dimorphism in t he young bats and in their mothers.