The domiciles, reproduction, social organization and sex ratio of the banana bat Pipistrellus nanus (Chiroptera, Vespertilionidae) in Malawi, Central Africa

Investigated were the domiciles, reproduction, social organisation and sex ratios of the Banana Bat, Pipistrellus nanus, in Malawi. The bats were taken from furled banana leaves at fortnightly or monthly intervals from September 1984 to June 1985. The furled leaves were ephemeral domiciles lasting one to three days. A surplus of domiciles was always available. Females were monoestrus with the birth of twins in November and lactation lasted about eight weeks. The testes in males were scrotal from April to October, and attained maximal size in May. During lactation adult males roosted single, while females with their young roosted singly or in maternity groups. Post-lactating females roosted singly or with groups of subadults and/or other post-lactating females, and the adult males continued to roost singly. In April, by which time the testes of all males have become scrotal, all bats were assumed to have reached sexual maturity and they began to live in harems (one adult male with one or more females). An equal number of males and females were born, but females outnumbered males for at least seven months of the year. The data from Malawi are compared with data from Kenya (O’Shea 1980), South Africa (LaVal and LaVal 1977), and elsewhere. Geographical variation in domiciles and reproduction, and the relationships between different aspects of the biology of P. nanus, are discussed.