Roosting Requirements of Two Frugivorous Bats (Sturnira lilium and Arbiteus intermedius) in Fragmented Neotropical Forest1

Abstract

As tropical forest fragmentation accelerates, scientists are concerned with the loss of species, particularly those that play important ecological roles. Because bats play a vital role as the primary seed dispersers in cleared areas, maintaining healthy bat populations is critical to natural forest regeneration. Observations of foraging bats suggest that many Neotropical fruit-eating species have fairly general habitat requirements and can forage in many different kinds of disturbed vegetation; however, their roosting requirements may be quite different. To test whether or not general foraging requirements are matched by equally broad roosting requirements, we used radiotelemetry to locate roost sites of two common frugivorous bat species (Sturnira lilium and Artibeus intermedius) in a fragmented forest in southeastern Mexico. Sturnira lilium roosted inside tree cavities and selected large-diameter roost trees in remnant patches of mature forest. Fewer than 2 percent of trees surveyed had a mean diameter equal to or greater than roost trees used by S. lilium. Artibeus intermedius roosted externally on branches and vines and under palm leaves and selected roost trees of much smaller diameter. Compared to random trees, roost trees chosen by A. intermedius were closer to neighboring taller trees and also closer in height to these trees. Such trees likely provide cryptic roosts beneath multiple overlapping crowns, with sufficient shelter from predators and the elements. While males of A. intermedius generally roosted alone in small trees within secondary forest, females roosted in small groups in larger trees within mature forest and commuted more than three times farther than males to reach their roost sites. Loss of mature forest could impair the ability of frugivorous bats to locate suitable roost sites. This could have a negative impact on bat populations, which in turn could decrease forest regeneration in impacted areas.