Long-term studies are crucial for the understanding of population dynamics and the evolutionary processes responsible for the diversity of life. The evolutionary responses of populations in the presence of environmental fluctuations can be evaluated by temporal variation in measures of fitness, which represents the integration of the number of descendants produced throughout life, formed by a survival component and a reproduction component. The present project aims to understand the ecological and evolutionary processes involved in the adaptive responses of bats (survival and reproduction), in relation to environmental changes, in the context of a long-term demographic study. To achieve this purpose, we intend to monitor a population of the bat Carollia perspicillata, using a mark and recapture protocol for analysis in an open population model (Cormack-Jolly-Seber), measuring the temporal variation of fitness in terms of survival and reproduction , associated with meteorological variables and the physical condition of the animals. Bats are important model systems in different areas of evolution, ecology and even human health. These animals perform ecosystem services of population control, dispersal and pollination, in addition to regulating emerging diseases, as they are reservoir hosts for the greatest wealth of viruses with zoonotic potential. Increasing our understanding about the population dynamics of this group has potential for theoretical developments (basic science) and practical applications in conservation and health.