Abstract:
We surveyed bats at 30 localities in the Soutpansberg and Blouberg Mountains within the
newly proclaimed Vhembe Biosphere Reserve (VBR) of northern South Africa, based
on ANABAT acoustic recordings (63 nights) conducted in parallel with captures of
260 individuals from harp traps (29 trap-nights) and mist nets (54 trap-nights), and searches
of ten day-roosts and two night-roosts. Twenty-four species of bats were captured, or
positively identified from roosts, out of 44 species previously recorded for the VBR. For
those species captured during the study and one additional commonly recorded species,
Chaerephon ansorgei, which was not captured, we compiled a library of ANABAT call
parameters for reference calls,based on released bats or bats emerging fromknown-species
roosts. Reference calls were obtained from the study area where possible, or from the
closest possible site in the savanna region of southeastern Africa. Using principal
component analysis and plots of frequency histograms of selected parameters, we investigated
the extent to which reference calls of different species could be distinguished on call
parameters. Complete separation was obtained for most species but certain species-pairs
or trios showed overlap, particularly amongst molossid bats. Accurate identification of
unknown calls was complicated by natural intraspecific variation in echolocation call structure
due to habitat and behaviour in our species-rich study area.We advocate a conservative
approach whereby species-pairs or groups with overlapping calls are treated as single
‘species’. Such underestimation can be partly corrected using rarefaction approaches, as
illustrated by data collected from Blouberg Nature Reserve. Particularly when surveying
bats in species-rich areas such as the eastern savannas of southern Africa, both acoustic
and capture-based surveys are necessary to accurately estimate true species richness.
From our capture data and roost searches,we recorded nine to 14 species at four west–east,
grouped localities defined by this study. Adding acoustic data using a conservative approach
to classify overlapping species-pairs or trios,we obtained minimumrichness estimates of 15
to 21 species, values which were close to those predicted by a recent macro-ecological model.We found no evidence for a west–east increase in richness with increasing precipitation
as predicted by coarse-scale macroecological predictions.
