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1

An experimental test of gating derelict mines to conserve bat roost habitat in southeastern Australia

100%
Slade C. P., Law B. S.
Acta Chiropterologica
|
2008
|
tom 10
|
nr 2
Management of derelict mines to improve subterranean bat habitat and minimise safety risks to the unsuspecting public is occurring more frequently. Many caves and mines around the world have had gates placed at mine and cave entrances as a means of maintaining bat habitat and preventing human access, but there have been few replicated experiments to test their effectiveness. We experimentally tested a staged installation of a template gate at two mines while monitoring another two un-gated derelict mines in southeastern Australia. We recorded changes in numbers, behaviour and the relative species abundance of two bat species (Rhinolophus megaphyllus and Miniopterus schreibersii) before and after the gates were installed. The template gate (20 mm diameter plastic tubing) was installed in three stages, with the initial horizontal bar spacing at 450 mm, followed by a spacing of 300 mm and a final spacing of 125 mm. Bat numbers and behaviour were largely unaffected by bar spacings of 450 mm and 300 mm. The major findings were that immediately after the installation of bars at the final spacing (125 mm gap), numbers of bats declined significantly and a significant increase in the number of aborted exit and entry flights was observed. Detectors proved to be inadequate at quantifying changes in the relative abundance of species. Eleven days after the final installation there were no significant differences between the numbers of bats leaving gated and control mines, suggesting bats had learnt to negotiate the bars after a short period of time. However, flight behaviour was still affected after habituation, especially baulking at the structure when bats attempted to re-enter before dawn. The low replication of mines in the experiment warrants caution in extrapolating this result. Until further gating experiments are carried-out, we recommend site specific monitoring whenever mines are gated.
2

Geographic variation in the echolocation calls of Vespadelus spp. (Vespertilionidae) from New South Wales and Queensland, Australia

81%
Law B. S., Reinhold L., Pennay M.
Acta Chiropterologica
|
2002
|
tom 04
|
nr 2
We investigated the extent of geographic variation in the echolocation calls of five species of microchiropteran Vespadelus in eastern Australia. Bat calls were recorded with Anabat II detectors and computers, and analysed using Analook software. A single call parameter, characteristic frequency (the frequency at the end of the flattest part of the call), was used to document changes in echolocation calls over geographic distance. For V. vulturnus and V. regulus, changes in call frequency were abrupt and sizeable (up to 14 kHz), with two or three frequency groups present within each species. In V. darlingtoni, the changes in frequency were gradual across their range, with an isolated island population resembling the closest region on the mainland. One species examined here, V. troughtoni, had calls that were consistent throughout its range. Calls of V. pumilus were also consistent across geographic regions except for at one site (Chichester State Forest). At this site calls occupied only the upper end of the species frequency range. Body size, measured as forearm length for each species, was significantly smaller at inland sites, but did not vary with latitude or consistently with intraspecific call variation. Broad patterns and possible causes of geographic variation in call frequency are discussed. We conclude that confident identifications of Vespadelus calls from the geographic regions outlined in this paper will only be made with reference calls collected from the relevant regions.
3

Reliable automation of bat call identification for eastern New South Wales, Australia, using classification trees and AnaScheme software

81%
Adams M. D., Law B. S., Gibson M. S.
Acta Chiropterologica
|
2010
|
tom 12
|
nr 1
Accurate and efficient identification of bat (Microchiroptera) echolocation calls has been hampered by poor knowledge of the intraspecific variability in calls (including regional variation), a lack of call parameters for use in separating species and the amount of time required to manually identify individual calls or call sequences. We constructed and tested automated bat call identification keys for three regions in New South Wales, Australia, using over 4,000 reference calls in ≈300 call sequences per region. We used the program AnaScheme to extract time, frequency and shape parameters from calls recorded with the Anabat system. Classification trees were built to separate species using these parameters and provided the decision rules for construction of the keys. An ‘Unknown’ category was included in the keys for sequences that could not be confidently identified to species. The reliability of the keys was tested automatically with AnaScheme, using independent sets of reference call sequences, and keys were refined before further testing on additional test sequences. Regional keys contained 18–19 species or included species groups. We report rates of sequence misidentification (accuracy) and correct identification (detection) relative to all sequences (including ‘unknowns’) used to test each version of a key. Refined versions of the keys were accurate, with total misidentification rates of 0.5–5.3% for the three regions. Additionally, total correct identifications for regions were 56–75% (> 50% for most species), an overall high rate of detection. When ‘unknowns’ were ignored, as is common in many published studies, correct identification for regions increased to 91–99%, rates which compare favourably to the most successful classifiers tested to date. The future use of AnaScheme for automated bat call identification is promising, especially for the large-scale temporal and spatial acoustic sampling to which Anabat is particularly suited.
4

Designing effective habitat studies: quantifying multiple sources of variability in bat activity

71%
Fischer J., Stott J., Law B. S., Adams M. D., Forrester R. I.
Acta Chiropterologica
|
2009
|
tom 11
|
nr 1
Common aims of habitat studies are to differentiate between (i) suitable and unsuitable sites for a given species, and (ii) sites used by different communities of species. To quantify differences between sites, field data of site use must be precise enough that true underlying between-site variability is not masked by within-site measurement error. We designed a pilot study to guide the development of a survey protocol for a habitat study on bats in an agricultural landscape in southeastern Australia. Three woodland sites and two scattered tree sites of 2 ha each were surveyed for nine consecutive nights. At three locations within each site (spaced > 50 m apart) one or two Anabat detectors were mounted 1 m above ground or in a tree (2 m above ground). We used mixed regression models to quantify multiple sources of variability in bat calling activity, and graphical data analysis to visualise how increases in survey effort were likely to affect inference. For the five most active species, we found that typically over 40% of variability in nightly detections occurred at the between-site level; approximately 10% occurred between locations within sites; approximately 20% was explained by night-to-night differences; and approximately 30% of variability was not attributable to systematic variation within experimental units. Differences in community composition between sites were clearly evident when two or more detectors per site were used for four or more nights. We conclude with six general considerations for the design of effective habitat studies. These are to (i) consider key contrasts of interest; (ii) use data from mild, calm, dry nights only; (iii) calibrate detectors; (iv) use multiple detectors where possible, or move a single detector within a site; (v) survey for multiple nights; and (vi) where vertical differentiation in habitat use is likely, mount detectors at different heights. These considerations need to be balanced within the context of financial and logistical constraints.
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