Vertical structure of an assemblage of bats (Mammalia: Chiroptera) in a fragment of Atlantic Forest in Southern Brazil

Fernando Carvalho,João O Menegheti,Marta E Fabián

doi:10.1590/s1984-46702013000500004

Abstract

Few studies have focused the vertical structure of bat assemblages, and how it influences community composition. The goal of this study was to analyze the vertical structure of an assemblage of bats in a forest fragment in southern Brazil. Bats were sampled using mist-nets placed at three heights (understory, below-canopy, and canopy). Forest strata were compared with respect to their species richness and diversity. The latter was estimated using the Shannon-Wiener index (H'), and the statistical significance of differences among strata was assessed using t tests. We used an index of Constancy (C) to determine the frequency of a given species in each vegetation stratum, such that a species was considered as (C > 50), less frequent (25 < C < 50) and occasional (C < 25). We captured 485 bats belonging to two families and 24 species. In the understory layer, we captured 173 individuals in 13 species, which resulted in a diversity index of H' = 1.981. In the under-canopy, 153 individuals were caught in 18 species and the resulting diversity index was H' = 2.509. Finally, in the canopy, 159 bats were caught, in 22 species, with the resulting diversity index of H' = 2.442. In the understory and in the canopy, only one species Artibeus lituratus (Olfers, 1818) was classified as frequent. Four species A. lituratus, Sturnira lilium (E. Geoffroy, 1810), Anoura geoffroyi Gray, 1838, and Eptesicus diminutus Osgood, 1915 were classified as less frequent in the under-canopy stratum. All other species recorded in each stratum were classified as occasional. The studied bat assemblage showed vertical stratification, with the higher strata harboring increased diversity. Our study shows how important it is to sample the upper levels of a forest fragment to obtain a more representative understanding of the use of space by a bat assemblage.

Highlights

Chiroptera is the second largest order of mammals (KALKO 1998)
Because of the great ecological importance of bat assemblages, several studies have been conducted focusing on their structure (FLEMING et al 1972, AGUIRRE 2002, ESBÉRARD 2003, BERNARD & FENTON 2007), with the goal of understanding the factors that allow for the coexistence of such a diverse fauna
In the case of bats, studies on vertical stratification demonstrate the existence of differences in richness and abundance among strata, both for Megachiroptera (FRANCIS 1994, ZUBAID 1994, HENRY et al 2004, HODGKISON et al 2004), and in Microchiroptera (BERNARD 2001, LIM & ENGSTROM 2001, SAMPAIO et al 2003, REX et al 2008, PEREIRA et al 2010)

Summary

Introduction

Chiroptera is the second largest order of mammals (KALKO 1998). In tropical forests, this group accounts for nearly 40 to 50% of the total mastofauna, strongly affecting richness and diversity patterns (ESTRADA & COATES-ESTRADA 2001). In the case of bats, studies on vertical stratification demonstrate the existence of differences in richness and abundance among strata, both for Megachiroptera (FRANCIS 1994, ZUBAID 1994, HENRY et al 2004, HODGKISON et al 2004), and in Microchiroptera (BERNARD 2001, LIM & ENGSTROM 2001, SAMPAIO et al 2003, REX et al 2008, PEREIRA et al 2010) These differences allow some species to be classified as canopy, sub-canopy, or understory specialists (FLEMING et al 1972). This division does not imply that these species only use a single stratum (KALKO & HANDLEY 2001), but rather that they show preference for a given one (SAMPAIO et al 2003)

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Conclusion