INTRODUCTION Bats use a diversity of roost sites that provide ideal conditions for resting, feeding, and for engag- ing in many social interactions that include rearing young, copulation, allogrooming, and informa- tion transfer. Roosts are also critical for bats’ sur- vival as they protect them from predators and harsh environmental conditions (Kunz, 1982; Kunz and Lumsden, 2003; Altringham, 2011). In fact, as bats leave their roosts, they become significant- ly more vulnerable to predation (Speakman, 1991; Fenton et al., 1994; Rodríguez-Durán et al., 2010), and thus many species spend a significant por- tion of their lives in them. By selecting adequate roosts, bats may additionally increase their fitness by spending less energy in thermoregulation and by reducing the rates of evaporative water loss (Webb et al., 1995; Speakman and Thomas, 2003). The latter advantages are known as major driving forces of roost-site selection, primarily in temperate regions (Kerth et al., 2001; Sedgeley, 2001). In tropical regions, bats use some of the same roost types available in temperate regions, such as caves and tree cavities. These sites are ideal as they provide stable temperatures and high humidi- ty compared to more exposed conditions (Rodrí- guez-Durán, 1995; Lundberg and McFarlane, 2015; Maziarz et al., 2017). However, in the tropics a large proportion of species also roosts in more exposed sites, such as under modified leaves or inside the Acta Chiropterologica, 21(1): 175–181, 2019 PL ISSN 1508-1109 © Museum and Institute of Zoology PAS doi: 10.3161/15081109ACC2019.21.1.014 Microclimate of developing tubular leaves used as roost sites by bats NATHALIA PÉREZ-CÁRDENAS 1 , KATHERINE PORRAS-BRENES 2 , LEYDI V. AUCCACUSI-CHOQUE 3, 4 , JOANNA J. SUÁREZ-TORRES 5 , ROSA M. BROOKS 6 , and GLORIANA CHAVERRI 7, 8, 9 1 Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Morelia, Michoacán, Mexico 2 Escuela de Ciencias Biológicas, Universidad Nacional, Campus Omar Dengo, Heredia, Costa Rica 3 Frankfurt Zoological Society - Perú, Entel Perú C-1, Wanchaq, Cusco, Peru 4 Museo de Historia Natural de la Universidad de San Antonio Abad del Cusco, Paraninfo Universitario (Plaza de Armas s/n), Cusco, Peru 5 Centro Universitario de Ciencias Biológicas y Agropecuarias, Universidad de Guadalajara, Camino Ramón Padilla Sánchez 2100 Nextipac, 45200 Zapopan, Jalisco, Mexico 6 Centro Oriental de Ecosistemas y Biodiversidad, Santiago de Cuba, Cuba 7 Recinto de Golfito, Universidad de Costa Rica, Alamedas, Golfito 60701, Costa Rica 8 Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Panama 9 Corresponding author: E-mail: gloriana.chaverri@ucr.ac.cr Roosts are critical for the reproduction and survival of bats and many species spend a significant portion of their lives in them; thus, individuals should carefully select sites that reduce predation risk while providing ideal microclimatic conditions. Many studies have determined that bats select warmer and more humid roosts in temperate regions, but few studies have determined if roosts selected by tropical species also provide suitable conditions. In this study we compare temperature and humidity within and outside furled tubular leaves of plants in the order Zingiberales, which are used by several tropical species as roost-sites, to determine if these structures provide microclimatic advantages to bats. We found very small differences between the internal and external temperatures of tubular leaves, and the difference further decreased as leaves developed. However, we found large differences in humidity within the tubular leaf compared to external conditions, which were strongly dependent on a leaf’s diameter and genus. The internal humidity was often 20% above the external, particularly when leaves were narrower, and tubular leaves in the genus Heliconia were more humid than those in the genus Calathea. Our findings suggest that, despite being fairly exposed structures, furled tubular leaves provide suitable microclimatic conditions for tropical species. Key words: disc-winged bats, evaporative water loss, humidity, temperature, thermoregulation