Appendix D Terrestrial and Aquatic Biodiversity - Environment ...

SZ247: Bat survey from the Western Desert Resources Towns River project area, NT
5.0 DISCUSSION
5.1 Bat diversity
A total of 22 species are likely to be present in the Roper River – Limmen – Borroloola region
based on compiled records and derived distribution limits in Milne and Pavey (2011) (Table 1).
Within any one locality, the species assemblage is likely to contain fewer species than this
regional total, on the basis of the habitats present. In the case of the MLA – Towns River
project area, the absence of cave roosting bats such as Hipposideros ater, Rhinonicteris
aurantia, Vespadelus caurinus and V. finlaysoni may be explained by the absence of
significant rocky outcrop and rock types prone to cave development within a few kilometres of
the locality, while the presence of Taphozous georgianus is explained by their relatively large
capacity for long distance flight based on wing morphology (e.g. Bullen and McKenzie 2002).
In addition, the absence of species such as Mormopterus loriae cobourgiana, Pipistrellus
westralis and Nyctophilus arnhemensis is not surprising given the distance from coastal
habitats, which these species appear to prefer (e.g. Churchill 2008).
In the case of haul road sites (Limmen River, Rosie Creek), there were more species detected,
with the additional species roosting in caves during the day: Rhinonicteris aurantia and
Vespadelus caurinus. The addition of cave forming rock promotes biodiversity and
increases the habitat value of those localities. In the case of the proposed port site at Bing
Bong, bat richness was relatively low compared to other sites (acoustic records available only,
and bearing in mind relative acoustic sampling effort), but further future effort might detect
species that prefer mangal and other coastal habitats such as Mormopterus loriae,
Nyctophilus arnhemensis and Pipistrellus westralis.
Overall bat diversity in the MLA – Towns River project area was moderate, with only eight
species detected. Most of these were tree-roosting species, with the exception of
Taphozous georgianus, which roosts in caves and could have reached the project area from
roosts located several kilometres away, given the observed lack of significant cave-forming
rocky outcrop in the project area. The combination of both acoustic recordings and trapping
was valuable in terms of maximising the detection of species for two reasons: 1. most species
could be identified from multiple sites (=habitat types) within the project area with minimal
effort and based on reference acoustic signatures described by Milne (2002); and 2. for
situations where two species could not be differentiated from each other because of their very
similar echolocation call characteristics, trapping was able to confirm the presence of both
candidates in the project area (e.g. Chalinolobus nigrogriseus and Scotorepens greyii) or
indicate which of several candidates could be confirmed at a minimum (e.g. Nyctophilus
geoffroyi).
Bats captured in mist nets and harp traps could be identified reliably to genus level based on
descriptions in field guides such as Churchill (2008), however there was some potential for
both misidentification or the presence of cryptic taxa at the species level. DNA barcoding
was used to verify the putative species level identifications. While publically available
genetic context data from Australian bat species is generally lacking, which prevented the
association of the DNA barcodes with reference genetic sequences from known species (at
least within the timeframe of this study), the amount of genetic variation within clades (= main
branches) of each phylogram was relatively small, indicating that only one species was
present per genus. However, in the case of small vespertilionids putatively attributable to
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