The Breeding Cycle of an Equatorial Bat (Pteropus Giganteus of Ceylon)

Summary. 1 The fruit-bat Pteropus giganteus, living in the equable tropical climate of Western Ceylon (7° N.), has a sharply denned annual breeding season. 2 The testes increase in weight while the days are growing shorter. They are heaviest in October-November. Their weight decreases sharply about the time the eggs are fertilized and shortly afterwards. Sperms are abundant in the epididymides throughout the year. 3 Conception occurs in December, shortly before the length of day begins to increase. Pregnancy lasts about six months, so that the young are born in May. 4 An analysis of all available data shows that the Pteropidae tend to copulate while the days are growing shorter.