REPRODUCTION IN THE BATS VESPADELUS-VULTURNUS, V-REGULUS AND V-DARLINGTONI (MICROCHIROPTERA, VESPERTILIONIDAE) IN COASTAL SOUTH-EASTERN AUSTRALIA

The sequence of reproductive and associated events that occurs in Vesp adelus vulturnus is similar to those that are common to hibernating ve spertilionids and rhinolophids. Females become sexually mature in thei r first year, whereas males do not undergo their first spermatogenesis until their second year. Both sexes accumulate fat deposits in late s ummer and autumn, but females begin to do this earlier and accumulate more than males. These deposits are gradually depleted over the course of winter. In autumn females produce a follicle of hibernation, the r upture of which is delayed until spring, when the resultant secondary oocyte is fertilised by sperm stored in the female reproductive tract. Females are monoestrous. Both ovaries are functional, although implan tation occurs only in the right uterine horn. Males also undergo an an nual cycle. Plasma androgen concentration and seminiferous tubule diam eter reach a peak in late summer, with subsequent release of spermatoz oa, but the accessory sex glands do not reach maximum size until late autumn. Sperm are present in the epididymides of males more than one y ear of age for the duration of winter. Male V. vulturnus arouse from t orpor during winter more frequently than females. It is hypothesised t hat they do this in order to copulate, even though females store sperm and a copulatory plug forms in the vagina after insemination. The beh aviour of the males can be explained by three factors: (1) some first- year females are not in oestrus at the beginning of winter, (2) some f emales with sperm stores depleted or absent are caught flying during w inter and (3) in some females copulatory plugs are voided long before fertilisation occurs, thereby removing the barrier to subsequent insem ination. Vespadelus regulus and V. darlingtoni appear to have a reprod uctive cycle similar to that of V. vulturnus.