Reproductive phenology and sex ratio variation of the Thumbless bat Furipterus horrens (Cuvier, 1828) (Furipteridae)

Reproduction is crucial for species survival, influencing population dynamics and fitness. For female small mammals, pregnancy and lactation are energetically costly activities and thus are typically timed to coincide with the season of highest food available. Reproductive phenology of bats varies by species and geographic location and data on Neotropical bats, in particular for non-phyllostomids, is scarce. We examined the reproductive phenology and sex ratio patterns of the aerial insectivorous bat Furipterus horrens (Furipteridae) in the Eastern Brazilian Amazon using monitoring data collected for over 10 years in 100 iron caves distributed in the Serra dos Carajás region of northern Brazil. Annual timing of reproduction of Furipterus horrens was unimodal, with pregnancy rates peaking at the dry season and lactation events spanning the end of the dry season into the early rainy season. Sex ratios averaged 0.75 across years and exhibited no variation between seasons. Understanding the reproductive phenology of species such as F. horrens that rely on specific habitats and rocky shelters, such as caves, is key to development of monitoring programs and actions to protect their populations. Both long-term monitoring and research focusing on the natural history of Neotropical bat species are essential to the development of effective conservation strategies and programs.