PDBFF - Bats

Not so much in a nutshell

Tropical bats represent important components of biodiversity from taxonomic and functional perspectives, and provide vital ecosystem services. Because of their local abundance, richness, and ecological diversity, bats are a promising indicator group for studying responses to landscape fragmentation.

Although a growing number of studies have addressed the effects of forest fragmentation on tropical bat assemblages, these studies generally have had to draw inferences based on sampling that spanned relatively short periods. However, little is known about bat responses to habitat fragmentation over the longer term.

Most of our empirical understanding of tropical fragmentation has been derived from the Biological Dynamics of Forest Fragments Project (BDFFP) in Brazil, the world's largest and longest-running experimental study of habitat fragmentation. The impacts of forest fragmentation on the BDFFP bat fauna were initially assessed in 1996-99. The overall objective of this project is to investigate the temporal dynamics of bat responses to forest fragmentation within the BDFFP landscape. The availability of a data set from 1996-99 provided an unique opportunity for a comparative follow-up study aimed at elucidating temporal changes in the bat fauna and therefore to provide rare insights into the longer-term dynamics of a fragmented tropical bat assemblage.

We are currently resurveying the same forest fragments and control plots in continuous forest first surveyed in 1996-99 (using identical methods, i.e. ground and canopy mist nets for sampling phyllostomid bats and automatic and manual acoustic surveys for aerial insectivorous bats). These data will be used to evaluate temporal changes in population- (abundance), ensemble-, and assemblage-level parameters (e.g. species richness, diversity, species composition) and how they differ among fragments of different size and between fragments and controls.

Little is known about how bats respond to edge effects, particularly in relation to temporal changes in the strength of edge effects associated with matrix regeneration. Data from interior and edge transects in the fragments and controls as well as in the adjoining matrix will be used to assess edge-related responses of bats and to determine temporal variation in those responses.

As fragmentation is a landscape-scale phenomenon, the consequences of fragmentation on biodiversity are most appropriately assessed within a landscape framework. We will determine fragmentation effects within the greater landscape context and assess whether bat responses are related to a range of predictors describing landscape composition and configuration. By evaluating relationships between biotic response variables and landscape metrics both across different spatial scales and across time we will be able to more adequately address the complexity underlying bat responses to fragmentation than in previous studies on this issue.

We will further evaluate whether species responses are associated with particular ecological traits of bat species. Comparing the results with findings from a study in a landbridge island system will allow us to gain insights into which species characteristics determine vulnerability to landscape transformation in systems of different fragment-matrix contrast. So far no study evaluating fragmentation impacts on bats has addressed both the spatial aspects of fragmentation, i.e. the larger landscape context, and temporal effects, as we propose to do. We believe that this approach can greatly advance our understanding of fragmentation effects on bats and that the findings from this study will make an important contribution to the field of fragmentation research in general.

Map from www.pdbff.inpa.gov.br