Reproduction of the spotted-winged fruit bat Balionycteris maculata (Thomas 1893) in Brunei, Borneo (Megachiroptera Pteropodidae)

C. P. Kofron


The spotted-winged fruit bat Balionycteris maculata (Thomas 1893) (Megachiroptera Pteropodidae) is a small fruit bat inhabiting Southeast Asia. I studied its reproduction in Brunei, Borneo, where individuals were captured in rainforest. Adult females (n = 18) had body masses of 10.5 to 17.5 g, with forelimbs 3.97 to 4.33 cm length. Based upon my data, I estimate the following regarding reproduction of B. maculata within the 12-month time frame from October to September: a birthing season for all adult females from approximately October to December; postpartum oestrus and mating; 2 to 4 months of lactation; and a prolonged and delayed embryonic development, with the subsequent parturition during the next birthing season from approximately October to December. In sum, the reproductive cycle is consistent with a pattern of seasonal monoestry. The estimated birthing season occurs during a season of greater rainfall, and it appears not timed to the season of abundant flowering/fruiting (April). Female and male B. maculata appear to attain sexual maturity quickly during the first year after birth, likely within 6 months. Adult males (n = 16) had body masses of 10.5 to 13.5 g, with forelimbs 3.85 to 4.33 cm. Adult males showed seasonal recrudescence of testes: regressed testes from early September to early December, and significantly larger testes from early December to May. The shortest lengths were approximately during the estimated birthing season, after which the testes lengthened. This particular pattern of testis recrudescence does not appear to be correlated to photoperiod.

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