We studied the population dynamics of the lesser long-nosed bat Leptonycteris curasoae in a cave in central Mexico for a two-year time. The population had substantial seasonal changes in size and composition during this time. Colony size was largest from February to July (22,000 adults) and contained equal numbers of males and females. In June and July, males had enlarged testes and presumably mated with females. In August, the population size began to decline and was mostly composed of pregnant females. Between September and December, the colony was composed exclusively of pregnant and lactating females and their young, and population size decreased to about one-third of the observed maximum size. In January, adult males returned to the roost and the population size increased. We also observed an increase in body mass and fat accumulation in both sexes, apparently related to reproductive activity. This is the first report of the continuous presence of a substantial female population of L. curusoae throughout the year in a single roost in Mexican tropics, indicating that some populations of L. curasoae in central Mexico complete their life cycle without having to migrate. RESUMENSe estudi6 la dinimica poblacional del murciklago nectarivoro Leptonycteris curusoae en una cueva localizada en el centro de MCxico durante dos afios. La poblacibn present6 cambios sustanciales en su tamafio y composicibn durante este periodo. El tamafio mis grande de la poblaci6n se registr6 entre febrero y julio (22,000-27,000 individuos) con una proporci6n similar de hembras y machos. En junio y julio 10s testiculos de 10s machos crecieron y aparentemente se aparearon con las hembras. En agosto, la poblacibn empez6 a disminuir y se encontraron casi exclusivamente hembras preiiadaz. Entre septiembre y diciembre, la colonia estuvo compuesta exclusivamente de hembras preiiadaz o lactantes y de sus crias. La poblaci6n disminuy6 en este periodo hasta equivaler a una tercera parte del tamaiio miximo registrado en el aiio. En enero, la poblaci6n empezo a crecer de nuevo con la incorporacibn de machos adultos. Durante el afio, en ambos sexos se observaron tambiCn cambios en la masa corporal y en la acumulaci6n de grasa aparentemente relacionados con la actividad reproductiva. Este es el primer estudio que reporta la presencia continua de hembras en una colonia de L. curasoae en la misma cueva durante todo el ~o para el centro de M6xico.Nuestros resultados indican que esta poblacibn no es migratoria a diferencia de otras poblaciones de esta especie.

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