Foraging Patterns and Resource Utilization in Seven Species of Bats in a Seasonal Tropical Forest

Abstract

Many tropical bats eat fruit, nectar, and pollen, and many tropical plants are pollinated or dispersed by bats. These groups make up a coevolved system that illustrates the effects plants can have on animal populations, and conversely, the effects animals can have on plant populations. This paper reports a 2—yr intensivie study of one bat—plant community in a seasonal Costa Rican forest. Seven common phyllostomatid bat species visited flowers or fruits. These were Glossophaga soricina, Phyllostomus discolor, Artibeus jamaicensis, Artibeus lituratus, Sturnira lilium, and Carollia perspecillata. The incidence of nectar ivory was high among these species, even among the species previously considered to be frugivores. Flora resources were seasonally abundant and competition for these resources appeared minimal during the period of peak abundance, but only G. ssoricina was nectarivorous during the period of low flower abundance. Fruit resources were more evenly available through the year and were more finely divided among the species of bats. There was a correlation between size of bat and the average size of fruits eaten. To the extent that competition for food has influenced the structure of this bat community, competition for fruits was more important than competition for nectar and pollen in determining species diversity. Resource distributions through space and time also infuenced bat foraging and reproductive behaviors. Small species of bats feed on resources of high abundance, whereas large species utilize resources that are patchy in time and space. The latter species probably forage in groups to maximize foraging efficiency. Reproductive behavior is seasonal and correlated with resource abundance. The flowering periods of plant species tend to be displaced, suggesting competition among plants for bat—pollinator services. A combination of the timing of plant—reproductive behavior and bat foraging characteristics promotes long—distance outcrossing and seed dispersal. These are critical factors in determining the low—density propulations characteristic of many tropical plant species.