Abstract

The activity and reproductive cycles of free-living and captive Nyctophilus gouldi were monitored over four breeding seasons. They deposited body fats in late summer and autumn, and hibernated from April until September. Spermatogenesis took place during the summer, spermatozoa being stored in the epididymides throughout the hibernation season. Matings were first observed in the captive colony in April each year. Males were seen to copulate with torpid females during the winter. A copulatory plug formed in the vagina following mating, and sperm were stored in the oviducts and uterine glands. Females were seen to expel the vaginal plug when arousing from torpor. Females were sexually active at 7-9 months old, and males at 12-1 5 months old. During the prolonged winter oestrus, ovaries contained large antral follicles. Ovulation occurred in September or early October and one or two young were born in late October or November. The twinning rate in captive N. gouldi was 54.5%. The young were weaned at 6 weeks old and first appeared in the free-living population in January. In an experimental group acclimated to 22°C in midwinter, breeding was initiated early, the first young being born 67 days before those in an outdoor colony.