Reproductive activity and diet of an urban population of Pallas' free-tailed bats Molossus molossus (Molossidae)

Urban areas offer favorable environments for the occupation by colonies of numerous insectivorous bats, indicating a good supply of resources for their support. Studies have shown that reproductive patterns of Neotropical bats can be seasonal in response to the availability of food resources. For an urban population of insectivorous bats, we studied the annual reproductive activity and the diet of Molossus molossus in Bucaramanga city (Colombia) and its relationship with the precipitation regime of the area. We captured bats monthly using mist nets (October 2016 to September 2017), including dry and wet seasons. The reproductive condition of the males was described by testicular histology and, in females, through the observation of external morphological characters and the analysis of vaginal smears. We also studied the stomach contents of 30 of the captured bats and if they change between seasons. Although not all females were in the same reproductive category each month, at the population level there were two pregnancy peaks in the dry seasons, with parturition at the beginning of the rainy seasons. Cytological analysis of vaginal smears optimized the evaluation of the reproductive stage and indicated that all sampled adult females were reproductive throughout the year. Males were reproductive year-round, showing sperm in seminiferous tubules and ducts. Coleoptera (41.3%) and Hymenoptera (37.7%) were the most important prey; the dietary composition and the amount of food consumed did not change between seasons. Females of this population showed a pattern of bimodal polyestry adjusted to the precipitation pattern of the study area, like other urban and wild populations of the species and other Neotropical insectivorous bats.