Neotropical bats are critical to forest regeneration through dispersal of seeds into deforested areas and to the long-term survival of several plant species reliant on bats for pollination. The ecosystem services provided by frugivorous and nectarivorous bats have received some investigation; however, we know virtually nothing about the impacts and benefits of Neotropical insect-eating bats. I have been investigating the insectivorous bat ensemble in a Mexican shade coffee plantation, with the goal of better understanding the ecosystem service of pest limitation provided by these bats. Southern Chiapas is one of Mexico’s most important coffee growing regions, and the site of multiple studies documenting the ecosystem services of biodiversity in tropical agroecosystems. In this talk, I bring together evidence from captures, acoustic monitoring, exclosure studies, and dietary studies carried out in this region, to provide a more holistic view of the ecosystem services that these bats provide coffee growers.
Insectivorous bats are abundant and diverse in shade coffee plantations, and approximately 30 insectivore species are found in the coffee plantations in southern Mexico. This diverse ensemble includes aerial-hawking bats adapted to foraging above the canopy, hawkers adapted to foraging in high-clutter environments, and foliage gleaning bats that take prey directly from substrates. Exclosure experiments quantifying the impact of the latter demonstrated an 84% increase in arthropod numbers on coffee plants from which bats were excluded. The gleaning bats (subfamily Phyllostominae) are particularly important in the limitation of arthropod pests, and we amplified DNA from several major coffee pests directly from their feces. We have also amplified DNA of coffee pests from the feces of other commonly captured non-phyllostomid bats; mormoopids are also apparently an important group of bats in coffee pest limitation. Bats in this area feed on a wide variety of insects, and their value lie particularly in their ability to suppress outbreaks of any number of arthropod pests. While these data do not allow me to assign a dollar value to the amount of crop damage prevented by bats in shade coffee plantations, they underscore the importance of bats as generalist predators in this agroecosystem. This ecosystem service is threatened by intensification of coffee agriculture, since the abundance and foraging activity of bats declines in plantations with low shade cover, even though these plantations have a higher abundance of some coffee pests.