Influence of Environmental Parameters on the Breeding of an Endemic Malagasy Fruit Bat, Rousettus madagascariensis (Pteropodidae)

The breeding biology of bats is in part regulated by environmental parameters, which in certain cases result in considerable intraspecific variation in reproduction periods. Few details are available on the reproductive behavior of Malagasy bats and this study focuses on parameters related to the mating and parturition periods in the endemic frugivorous and cave-roosting Rousettus madagascariensis (Pteropodidae). The birth period was estimated based on observations of mating behavior and presence of neonates in video recordings made at Ankarana (northern Madagascar) during different seasonal periods in 2017 and 2018. Based on animals captured in the same cave between 2014 and 2022, we also estimated the age of neonates in order to evaluate annual variation in parturition periodicity. Based on video recordings, mating was mainly observed (ordered based on highest frequency) in September, July, and January. This behavior, which generally took place during the dry season, was negatively correlated with temperature and rainfall, and had a low positive correlation with cave relative humidity. With most mating taking place between July and September, one parturition period occurs just before or during the wet season (between December and February), the period of highest fruit abundance in Ankarana. For cases of mating in January, excluding the possibility of sperm storage or delayed implantation, another parturition would occur in mid-April, a time of low fruit availability; however, no neonate was filmed or trapped in April and video recording data indicated that neonates were present between July and September, suggesting a parturition taking place from July to September. Parturition periods show some annual variation and appear to be mainly regulated by climatic aspects including rainfall and principally temperature; however, this variation was less pronounced as compared to other non-Malagasy pteropodid species. Further research on Malagasy fruit bats should focus on possible sperm storage or delayed embryonic development and, if found, associated correlations with environmental parameters.