POPULATION-DYNAMICS OF LEPTONYCTERIS-CURASOAE (CHIROPTERA, PHYLLOSTOMIDAE) IN JALISCO, MEXICO

We estimated population size and sex ratio, and recorded mass, levels of fat, and reproductive condition of adults of Leptonycteris curasoae living in a sea cave in Chamela Bay, Jalisco, Mexico, 10 times betwee n October 1992 and February 1994. We used carbon and nitrogen stable-i sotope techniques to determine the general diet of this plant-visiting bat in 1993 and 1994. Size of roost in 1993 varied from ca. 5,000 ind ividuals in March to ca. 75,000 in November. Females were absent from, or uncommon in, the roost from March through September. Beginning in July or August, many males and females migrated to the roost; bats lef t the roost in December. Some of these females migrate north to the So noran Desert to form maternity colonies in spring. Size of testis incr eased markedly from October through December, which we postulate is a mating period in this roost, Bats were lean in April and June (dry sea son) and fat in October and November (end of wet season). Stable-isoto pe analysis revealed that bats fed primarily at nonsucculent (C3) plan ts throughout the year; values for nitrogen were higher in the wet sea son than in the dry season. From a review of data on other roosts of L . curasoae, we conclude that most roosts have a seasonal fluctuation i n size and sexual composition. We also postulate that two reproductive populations of females exist in Mexico; a spring-birth population and a winter-birth population. Seasonal fluctuations in size of roost mea n that the timing of visits to the roost is critical for assessing the population status of this federally listed endangered bat.