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Insectivorous bat activity over swimming pools retrofitted for wildlife

Report prepared for Ku-ring-gai Council

Published by NSW Department of Industry, Lands & Forestry

Insectivorous bat activity over swimming pools retrofitted for wildlife

First published June 2017.

More information

Leroy Gonsalves and Bradley Law – Department of Industry, Lands & Forestry, Forest Science, Parramatta NSW.

Jacob Sife – Ku-ring-gai Council, Gordon NSW

www.industry.nsw.gov.au

Acknowledgments

This study was funded by Ku-ring-gai Council. We are grateful to residents of Ku-ring-gai LGA who provided access to

converted and non-converted pools for our survey.

Cover image: Jacob Sife

© State of New South Wales through Department of Industry, Skills and Regional Development 2017.

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will need to seek permission from the Department of Industry, Skills and Regional Development.

Disclaimer: The information contained in this publication is based on knowledge and understanding at the time of writing June 2017. However, because of advances in knowledge, users are reminded of the need to ensure that the information upon which they rely is up to date and to check the currency of the information with the appropriate officer of the Department of Industry, Skills and Regional Development or the user’s independent advisor.

Use of swimming pools retrofitted for wildlife by insectivorous bats

NSW Department of Industry i

Executive summary Within the urban matrix, green spaces play a valuable role in mitigating the detrimental impacts

of urbanisation on biodiversity. Swimming pools represent an opportunity to create additional

habitat elements via conversion to wildlife ponds, which may provide a refuge for fauna,

including birds and frogs, but also foraging habitat for bats. We assessed the value of converted

pools to insectivorous bats using acoustic surveys. In all, 25 converted pools that were spread

across the Ku-ring-gai local government area (LGA), nine natural creeks, three non-converted

pools and a single sediment pond were sampled between January and May 2017. Ten bat

species were recorded across all sites, including three threatened species. Nightly bat species

richness and activity were almost two times higher at converted pool sites than natural creeks.

Chalinolobus gouldii, a generalist species, was most frequently recorded, with 12 times as much

activity for the species at converted pools than natural creeks. This is consistent with high

activity previously recorded for the species in urban areas, including backyards without pools.

However, Myotis macropus, a specialist trawling bat species that is closely associated with

waterways was only detected at three natural creeks, highlighting the importance of natural

waterways as habitat for the species. Our study provides a baseline for long-term monitoring of

bats as an indicator of environmental change in the Ku-ring-gai LGA. We suggest that

monitoring sites used in the current study be resurveyed periodically (i.e., annual or biennial

surveys) to track trends in bat populations which will facilitate a long-term assessment of the

value of converted pools to bats in the Ku-ring-gai LGA.


NSW Department of Industry ii

Contents Executive summary ...................................................................................................................... i

Contents ...................................................................................................................................... ii

List of tables ................................................................................................................................ iii

List of figures ............................................................................................................................... iv

Introduction ................................................................................................................................. 1

Methods ...................................................................................................................................... 3

Study area and design ............................................................................................................. 3

Bat surveys .............................................................................................................................. 6

Data analyses .......................................................................................................................... 6

Results ........................................................................................................................................ 8

Comparison among waterbodies ........................................................................................... 10

Relationships between bat activity and environmental variables ............................................ 13

Discussion ................................................................................................................................ 16

The value of wildlife ponds for insectivorous bats .................................................................. 16

Relationships between bat activity and environmental variables ............................................ 17

Management recommendations ............................................................................................ 18

References ............................................................................................................................... 20


NSW Department of Industry iii

List of tables Table 1. Number of sites at which bat species were recorded in the Ku-ring-gai LGA. ................ 9


NSW Department of Industry iv

List of figures Fig. 1. Location of sampling sites in the Ku-ring-gai LGA. ........................................................... 4

Fig. 2. Survey sites for insectivorous bats in the Ku-ring-gai LGA. .............................................. 5

Fig. 3. Nightly bat species richness at natural and constructed waterways in the Ku-ring-gai LGA.

.................................................................................................................................................. 10

Fig. 4. Nightly bat activity at natural and constructed waterways in the Ku-ring-gai LGA.. ......... 11

Fig. 5. Chalinolobus gouldii activity at natural and constructed waterways in the Ku-ring-gai LGA.

.................................................................................................................................................. 12

Fig. 6. Canonical correspondence analysis bi-plot illustrating associations between activity of bat

taxa and environmental variables. ............................................................................................. 14


NSW Department of Industry 1

Introduction A major cause of decline in biodiversity is the loss and fragmentation of habitat resulting from

urban development (Garden et al. 2006). Remnant bushland in urban areas often occurs in

small patches and can be highly fragmented, with a lack of connectivity between these patches

(New and Sands 2002; Stenhouse 2004). However, it is in these remnants that urban-sensitive

species are often restricted (How and Dell 1993, 1994; Garden et al. 2006). Conversely, within

the urban matrix generalist species tend to dominate, while habitat and dietary specialists tend

to decline or become locally extinct (How and Dell 1993, 2000; White & Burgin 2004; Tait et al.

2005; Garden et al. 2006).

Within the urban matrix, green spaces play a valuable role in mitigating the detrimental impacts

of urbanisation on biodiversity (Goddard et al. 2010). Gardens form a major component of green

space in urban areas and can contribute considerable habitat elements, including trees, nest

boxes and ponds (Davies et al. 2009). The structural complexity of gardens is closely associated

with bird (Daniels and Kirkpatrick 2006) and invertebrate (Smith et al. 2006) abundance and

diversity. Consequently supplementing existing gardens with additional habitat elements may be

beneficial for urban biodiversity. However, space required to implement these features can be

scarce, particularly in high density urban areas.

Swimming pools in urban areas represent an opportunity to create an additional habitat element

in gardens, via conversion to wildlife ponds. Maintenance or removal of swimming pools can

require significant time and money. Conversion of swimming pools to wildlife ponds can provide

a refuge for fauna, including frogs, bats and birds. Furthermore, conversion of a pool does not

destroy the asset as it is possible to restore a functioning wildlife pond to a swimming pool if

required in the future. In the Ku-ring-gai local government area (LGA) it is estimated that there

are 16,000 swimming pools. A ‘Pool to Pond’ program has been developed by the Council,

providing residents advice regarding conversion of swimming pools to wildlife ponds as well as

provision of native fish and aquatic plants. In the twelve years of operation, 100 swimming pools

within the LGA have been converted to wildlife ponds through the ‘Pool to Pond’ program.

Insectivorous bats are a diverse fauna group that use echolocation to navigate their habitat and

detect prey (mostly insects such as moths, beetles and flies) (Churchill 2009). Bats occupy high

trophic levels and are considered indicators of environmental change (Jones et al. 2009).

Furthermore, the importance of water to bats is well established (Korine et al. 2016).



Consequently, bats represent key taxa that may respond to the provision of wildlife ponds in

urban gardens. We assessed the value of wildlife ponds to bats in the Ku-ring-gai LGA by

comparing diversity and activity of bats in wildlife ponds, natural pools in creeks and existing

swimming pools.



Methods

Study area and design The study was carried out in the Ku-ring-gai LGA, situated just 16 km North of Sydney’s CBD.

The LGA is moderately large (~8521 ha) and ‘leafy’, extending from Roseville in the south to

Wahroonga in the north, and from St Ives in the east to Lane Cove National Park in the west.

Natural area reserves represent approximately 1,150 ha of the LGA and many of these are

contiguous with National Parks including Ku-ring-gai Chase, Garigal, Lane Cove and Dalrymple-

Hay Nature Reserve (Ku-ring-gai Council 2016). The LGA also spans three of Sydney's major

catchments: Lane Cove River, Middle Harbour and Cowan Creek. These catchments are

drained by approximately 220 km of creek lines that occur in the LGA, with many of these in

semi-natural to natural condition, particularly those that occur in private easements, parkland

and bushland reserves. The LGA has a population of ~116,000 residents within the built area, of

which 95 % is low density housing and 5 % cent used for business (Ku-ring-gai Council 2016).

In all, 38 sites were selected for sampling (Fig. 1). Of these, nine were natural creeks (Fig. 2a).

Creeks were selected to be representative of the three major catchments in the Ku-ring-gai LGA

and to provide a natural reference for bat activity and the activity of Large-footed Myotis (Myotis

macropus). In the built area of the LGA, 25 swimming pools that were converted to wildlife ponds

(hereafter ‘converted pools’; Fig. 2b) and three non-converted pools (Fig. 2c) were selected for

sampling. An additional sediment pond was also sampled. While selection of converted pools

and non-converted pools aimed to be representative of the LGA, availability of converted pools

for sampling was limited. To account for this, particular characteristics of converted and non-

converted pools were recorded in situ during bat sampling or later extracted using spatial data

and ArcGIS (ESRI). These characteristics included distance (m) to nearest natural creek line,

extent of converted pond covered in vegetation (% cover), pool size (m2) and amount of

bushland (ha) within 500 m of the pool. Pools ranged in size from 0.0016-0.15 ha and were 67-

679 m from the nearest natural creek line. Vegetation cover over the pool ranged from 10-100

%, while bushland within 500 m of each site ranged from 9-880 ha.



Fig. 1. Location of sampling sites in the Ku-ring-gai LGA. Squares represent natural creeks, numbers 27, 28

and 30 indicate non-converted and all other numbers represent converted pools. Number 26 represents a

sediment pond.



Fig. 2. Survey sites for insectivorous bats in the Ku-ring-gai LGA: a) Natural creek (Gordon Creek); b)

Converted pool (Site 15); c) Non-converted pool (Site 28).

a

b

c



Bat surveys Bat activity was surveyed for two nights at all natural creek sites, while pools were surveyed for

up to five nights between summer and autumn 2017. At each site, a single AnaBat detector

(AnaBat II with Z-CAIM, AnaBat SD1, AnaBat SD2, AnaBat Express; Titley Scientific, Brendale

QLD) was deployed along the edge of a natural creek or a pool (converted and non-converted).

Detectors were set with microphones facing the water surface from a height of <0.5 m as M.

macropus usually flies 15-100 cm above the surface of water bodies (Churchill 2009). Each

detector recorded bat calls from dusk until dawn. Since bat activity can be significantly reduced

during heavy rain, sampling avoided these conditions. All recorded bat calls were identified to

species using automated call identification software, AnaScheme (Adams et al. 2010), in

association with an identification key for bats of Sydney (unpublished data – B. Law). Bat calls

with fewer than three valid pulses (i.e., minimum of six data points and model quality of ≥0.9)

were not analysed by AnaScheme. Because multiple bat species may call simultaneously, calls

were assigned to a species only if >50 % of pulses within the sequence were attributed to that

species and only passes with a minimum of three pulses classified to the same species were

identified. All bat calls that could not be assigned to a bat taxon were included in counts of total

bat activity, but were labelled as ‘unidentified’. Since linear calls of M. macropus and Long-eared

Bats, Nyctophilus spp., can be difficult to distinguish using automated software, all linear calls

were assigned an identification of ‘linear bat’ and were subsequently manually checked to verify

whether calls were produced by Nyctophilus spp. or M. macropus.

Data analyses The number of bat calls for each species and all species combined (hereafter total bat activity)

was tabulated for each site and night of sampling. Using SPSS version 23.0, Generalised Linear

Models (GLMs) were carried out to test for the effect of waterway type on bat species richness,

bat activity and the activity of individual species. Minimum daily temperature (BOM weather

station: Parramatta North 066124) was used as a covariate as bat activity is known to be

positively correlated with nightly temperature (O’Donnell 2000; Erickson and West 2002). Each

model was run using a normal distribution and scaled identity function in SPSS version 23.

A Canonical Correspondence Analysis (CCA) was undertaken to identify environmental

variables associated with activity of bat taxa. Only species that were recorded at three or more

sites were included in the analysis. Prior to running the CCA, all variables were log10 (x+1)

transformed as suggested by Palmer (1993). Environmental variables included in the analysis

were: local vegetation cover over pools, surrounding bushland cover within 500 m of detector,



distance to nearest drainage line, pool size, the presence or absence of significant water flow

(using active pumps as a proxy for pool and converted pool sites) and the % of sandstone and

shale within 500 m of the sampling site. The CCA was run using PAST (PAleontological

Statistics) version 3.0.

Best subsets regression analyses were undertaken to identify associations between response

variables (nightly bat activity and the activity of commonly recorded taxa) and measured

environmental variables. Analyses were undertaken using SPSS Version 23.



Results In all, 1,320 bat calls were recorded. Of these, 623 (47 %) were identified to one of ten taxa

(Table 1). All other calls were usually poor quality and of short duration, and could not be

assigned a species-level identification.



Table 1. Number of sites at which bat species were recorded in the Ku-ring-gai LGA.

Species Common name Converted pools

(25)

Non-converted pools

(3)

Sediment pond

(1)

Natural Creeks

(9)

Austronomus australis White-striped Freetail Bat 7 1 - -

Chalinolobus gouldii Gould’s Wattled Bat 21 3 - 5

Miniopterus australis* Little Bentwing Bat 1 0 - 1

Miniopterus schreibersii oceanensis* Eastern Bentwing Bat 12 2 - 4

Mormopterus ridei Eastern Freetail Bat 14 3 - 1

Myotis macropus* Large-footed Myotis - - - 3

Nyctophilus spp. Long-eared Bats 2 - - 1

Rhinolophus megaphyllus Eastern Horseshoe Bat 1 - - 3

Scotorepens orion Eastern Broad-nosed Bat - 1 - -

Vespadelus vulturnus Little Forest Bat 6 - - 3

*Indicates species listed on the threatened species schedules of the NSW Biodiversity Conservation Act 2016



Comparison among waterbodies Nightly bat species richness was significantly different among waterbodies (F2,69=3.173,

P=0.029). Species richness at converted pools was approximately double that of natural creeks

(t69=2.617, P=0.033; Fig. 3).

Fig. 3. Nightly bat species richness at natural and constructed waterways in the Ku-ring-gai LGA. Means denoted by different letters are significantly different from each other.

Nightly bat activity (no. passes night-1) differed significantly among waterbodies (F2,69=3.820,

P=0.027). Activity at converted pools was almost two-times greater than natural creeks

(t69=2.691, P=0.027; Fig. 4).



Fig. 4. Nightly bat activity at natural and constructed waterways in the Ku-ring-gai LGA. Means denoted by different letters are significantly different from each other.

Austronomus australis was too infrequently recorded to allow for statistical comparison among

waterway types. The species was recorded over seven converted pools and one non-converted

pool, but was not recorded over natural creeks.

Chalinolobus gouldii activity differed significantly among waterway types (F2,69=7.827, P=0.001).

Activity of C. gouldii was 12-times greater at converted pools than natural creeks (t69=5.606,

P<0.0001; Fig. 5).



Fig. 5. Chalinolobus gouldii activity at natural and constructed waterways in the Ku-ring-gai LGA. Means denoted by different letters are significantly different from each other.

Miniopterus schreibersii oceanensis activity was low (~0.9-3.4 calls night-1) and did not differ

significantly among waterway types (F2,69=2.431, P=0.095). Mormopterus ridei activity was also

low (~0.1-2.7 calls night-1) and did not differ significantly among waterway types (F2,69=0.468,

P=0.628). Miniopterus australis, M. macropus, Nyctophilus spp., Rhinolophus, megaphyllus,

Scotorepens orion and Vespadelus vulturnus were too infrequently recorded to allow for

statistical comparison among waterway types. Myotis macropus was only recorded on three

natural creeks within the LGA, while M. australis was recorded at a single converted pool and

natural creek. Nyctophilus spp. were recorded at two converted pools and one natural creek

within the LGA, while S. orion was recorded at a single site (non-converted pool). Rhinolophus

megaphyllus was recorded on three natural creeks and one converted pool within the LGA, while

V. vulturnus was recorded at six converted pools and three natural creeks.



Relationships between bat activity and

environmental variables A CCA revealed that non-converted pools were on sandstone and were characterised by an

absence of local vegetation cover and low surrounding bushland (Fig. 6). Converted pools were

on soils with more shale than sandstone and were characterised by greater distance to drainage

line, low water flow and greater local vegetation cover than non-converted pools (Fig. 6). Natural

creeks were located in drainage lines on sandstone with larger pool sizes, a moderate level of

surrounding bushland cover and higher water flow than converted and non-converted pools (Fig.

6). Myotis macropus was associated with natural creek sites with low local vegetation cover and

moderate water flow (Fig. 6). Rhinolophus megaphyllus was also associated with natural creeks

with moderate levels of bushland cover (Fig. 6). Austronomus australis, C. gouldii, M. ridei,

Nyctophilus spp. and V. vulturnus were associated with converted pool sites (Fig. 6). Miniopterus

schreibersii oceanensis was associated with low local vegetation cover, low surrounding

bushland cover and sandstone (Fig. 6).



Fig. 6. Canonical correspondence analysis bi-plot illustrating associations between activity of bat taxa and environmental variables. Centroids for the different waterbodies are also plotted.

Best subsets regression revealed four supported models that explained the variability in total

activity. Model-1 (R2=0.044, F=4.265, P=0.043) included local vegetation cover (+ve), while

model-2 (R2=0.042, F=2.545, P=0.086), model-3 (R2=0.04, F=2.491, P=0.090) and model-4

(R2=0.034, F=2.236, P=0.115) also included distance to nearest drainage line (+ve), pool size (-

ve) and surrounding bushland cover (+ve), respectively.

Four supported models explained the variability in C. gouldii activity. Model-1 (R2=0.259,

F=9.285, P<0.0001) included surrounding bushland cover (+ve), pool size (-ve) and local

vegetation cover (+ve), while model-3 (R2=0.2687, F=7.473, P<0.0001) and model-4 (R2=0.259,

F=7.212, P<0.001) also included % sandstone (-ve) and distance to nearest drainage line (+ve),

respectively. Model-2 (R2=0.259, F=9.282, P<0.0001) included surrounding bushland cover

(+ve), pool size (-ve) and % sandstone (-ve)



Five supported models explained the variability in M. ridei activity. Model-1 (R2=0.077, F=6.886,

P=0.011) included pool size (-ve), while model-2 (R2=0.088, F=4.404, P=0.016), model-4

(R2=0.069, F=3.635, P=0.032) and model-5 (R2=0.068, F=3.578, P=0.033 also included

surrounding bushland cover (-ve), distance to nearest drainage line (-ve) and local vegetation

cover (+ve), respectively. Model-3 (R2=0.089, F=3.322, P=0.025) included pool size (-ve),

surrounding bushland cover (-ve) and distance to nearest drainage line (-ve).

Four supported models explained the variability in M. schreibersii oceanensis activity. Model-1

(R2=0.059, F=5.442, P=0.023) included pool size (+ve), while model-2 R2=0.069, F=3.624,

P=0.032) and model-4 (R2=0.050, F=2.857, P=0.064) also included distance to nearest drainage

line (+ve) and surrounding bushland cover (-ve). Model-3 (R2=0.067, F=2.699, P=0.053)

included pool size (+ve), distance to nearest drainage line (+ve) and % sandstone (+ve).

All other taxa were too infrequently recorded to undertake regression analyses.



Discussion This is the first study to investigate the use of constructed wildlife ponds (‘converted pools’) by

insectivorous bats. Nightly bat species richness and activity at converted pools was greater than

natural creeks. Greater activity at converted pools mainly reflected the higher activity of C.

gouldii at these pools. Conversely, M. macropus was only detected on natural creeks. These

results are consistent with high activity previously recorded for generalist bat species in urban

areas, including backyards without pools, but highlight the importance of natural waterways as

habitat for a specialist trawling bat species.

The value of wildlife ponds for insectivorous bats Nightly bat species richness was greater at converted pools (2.1±0.2 species night-1) compared

to natural creeks (1.4±0.3). This level of species richness was comparable to species richness

recorded for backyards in the leafier parts of Sydney (Basham et al. 2010) and backyards in

vegetated landscapes within the Sydney Metropolitan region (Threlfall et al. 2011). Three

species (C. gouldii, ~88 % of sites; M. schreibersii oceanensis, 50 % of sites; M. ridei, 58 % of

sites) were commonly recorded at converted pool sites and at rates higher than at the natural

creek lines. These species were also commonly recorded in backyards without pools in leafier

suburbs of Sydney (Basham et al. 2010).

Nightly bat activity was greater at converted pool sites than natural creeks and non-converted

pools, though not significantly different for the latter. Notwithstanding, activity at converted pools

(23.2±2.8) was similar to activity recorded for backyards in vegetated parts of metropolitan

Sydney (Threlfall et al. 2011), but not northern Sydney where bat activity was approximately four

times greater (Basham et al. 2010). Interestingly, nightly activity at natural creek and non-

converted pool sites was ~40 % lower than converted pools. It is unclear why activity at

converted pools was considerably higher than natural creeks surveyed during this study. Natural

creeks tended to be located deep within sandstone gullies and low activity on small flyways

adjacent to creeks in these areas was also recorded by Basham et al. (2010). Activity at Basham

et al. (2010) gully sites was considerably lower than backyards that were often on shale geology

in this area, highlighting the importance of geology and productivity to bats in the Sydney area

(Threlfall et al. 2012). Activity at non-converted pools was generally low, but highly variable with

a small sample (n=3) of pools surveyed.

Activity of most taxa was very low across the LGA and did not allow for statistical comparison

among waterway types. However, the activity of C. gouldii at converted pools was 12 times



greater than natural creeks. This species is an edge-space bat (Adams et al. 2009) that is able

to forage in open spaces and along edges that are prominent in the urban matrix. Furthermore,

the species is known to tolerate lights and exploit insect concentrations at lights (Kirsten and

Klomp 1998; Adams et al. 2005). It should be acknowledged that unlike converted pool sites,

detectors used to survey natural creeks did not have omni-directional microphones and may

have failed to record some calls of C. gouldii flying above natural creeks, thereby contributing to

the difference between waterway types.

Despite having a close association with waterways, M. macropus was rarely recorded during the

survey. This species was only recorded at three sites, all on natural creeks. Converted pools

tended to have moderate amounts of vegetation cover over pools which represents physical and

acoustic clutter that can affect the ability of trawling bats to locate prey (e.g., Frenckell and

Barclay 1987; Boonman et al. 1998). In a study across metropolitan Sydney, the species was

negatively associated with backyard elements within the urban matrix (Threlfall et al. 2012).

Notwithstanding, the rarity of M. macropus in this survey contrasts with autumn surveys of

waterways in western Sydney, where the species was recorded at ~77 % of sampled sites

(n=26), which included natural and artificial creeks and wetlands situated on shale (Gonsalves

and Law 2016). Elsewhere in the Sydney estuary, the species was also widespread, though with

hotspots of activity identified (Gonsalves and Law in press). However, in freshwater

environments on underlying sandstone, M. macropus was rarely recorded (~38 % of sites, n=24)

(Asplet 2016).

Relationships between bat activity and

environmental variables Best subsets regression revealed four supported models that explained a very small amount (~4

%) of the variability in total activity, indicating that other factors not accounted for in this study

influence bat activity. Nightly bat activity was positively associated with local vegetation cover of

pools, distance to nearest drainage line and surrounding bushland cover, but negatively

associated with pools size. It is unclear why a positive association was found between bat

activity and local vegetation cover over ponds. It is possible that sites with greater cover of

vegetation over ponds had greater habitat structure, which is positively associated with

invertebrate diversity and abundance (Smith et al. 2006). The positive association between bat

activity and distance to nearest drainage line reflects greater activity of C. gouldii recorded at

converted pool sites which were generally situated some distance from drainage lines.

Chalinolobus gouldii activity was also positively associated with distance to nearest drainage

line. This species is able to forage in open spaces and along edges in the urban matrix,



including in well-lit areas (Kirsten and Klomp 1998; Adams et al. 2005). Greater bat and C.

gouldii activity with increasing surrounding bushland cover is consistent with previous findings

for bats in Metropolitan Sydney, with up to 50% less activity in open space and backyard

elements compared to bushland (Threlfall et al. 2012). Surrounding bushland in the Ku-ring-gai

LGA also likely provides more roosting habitat for tree-roosting bat species than backyards in

the matrix, with almost seven times more hollow-bearing trees ha-1 in sandstone gullies than

backyards (Basham et al. 2010). For other taxa, environmental variables measured in this study

only accounted for a small amount (<9 %) of the variability in their activity.

Management recommendations Waterbodies in the Ku-ring-gai LGA were used by a suite of bat taxa, including three threatened

species. Consequently these waterbodies represent important elements in an increasingly

urbanised landscape. Given its close association with waterways, M. macropus is likely to be

most influenced by their management.

Nightly bat activity was positively associated with surrounding bushland cover in the Ku-ring-gai

LGA, although the strength of this association was very weak. This is likely due to much of the

bushland in the LGA occurring on soils on underlying sandstone, which is less productive than

shale (Walker 1960; Benson et al. 1996). A previous study of bats in northern Sydney found a

similar pattern whereby bat activity was significantly higher in bushland on shale soils than

sandstone gully remnants (Basham et al. 2010). Bushland embedded in urban areas underlying

shale soils have high conservation value for bats (Basham et al. 2010) and should be prioritised

for retention.

Myotis macropus was a target species for this survey given its close association with waterways.

The species was rarely recorded and only detected on natural creeks in our survey. The failure

to record the M. macropus at converted pool sites is likely due to the presence of aquatic

vegetation and weeds on the surface of pools, which negative affects the ability of trawling bats

to detect prey (Boonman et al. 1998). On average, aquatic vegetation cover at converted pools

was ~51 %, reducing the area of open water available for prey detection by M. macropus.

Furthermore, two thirds of all converted pools did not have a water pump installed, providing still

water that promoted the development of algal mats. Increasing the area of open water (i.e.,

without aquatic vegetation and algal mats) will make converted pools more suitable for use by M.

macropus.

The detection of M. macropus on natural creeks only, highlights the value of creeks to this

specialised trawling bat species and the need for appropriate management. The rarity of the



species did not allow for any associations with environmental variables to be tested. Other

studies have found that M. macropus is most likely to be recorded on larger streams in the lower

end of catchments (Anderson et al. 2006). Removing riparian weeds on natural creeks may

serve to increase the area available for M. macropus to forage on natural creeks. In the Sydney

estuary, the M. macropus showed no association with surrounding bushland cover (Gonsalves

and Law in press), as was the case for urban streams in Sydney (Threlfall et al. 2012). However,

in western Sydney the species was positively associated with woodland cover, with activity on

natural creeks an order of magnitude higher than urbanised channels (Law and Gonsalves

2016).

Bats occupy high trophic levels and are considered to be good indicators of environmental

change (Jones et al. 2009). Furthermore, they can be cost effectively monitored using acoustic

sensors (Hourigan et al. 2009) with 90 % power to detect upward or downward trends of up to

30 % within 10 years (Law et al. 2015). Our study has provided data that can be used to

establish a baseline for long-term monitoring of bats as an indicator of environmental change.

We suggest that monitoring sites used in the current study be resurveyed periodically (i.e.,

annual or biennial surveys) to track trends in bat populations which will facilitate a long-term

assessment of the value of converted pools to bats in the Ku-ring-gai LGA. In addition to existing

monitoring sites, a selection of backyards without pools should also be surveyed to provide

context for results at pool to pond sites. To reduce variability in the data, future surveys should

use similar monitoring devices among waterbodies and should be undertaken in multiple

seasons (e.g., spring and autumn) to account for seasonal immigration and emigration of bats

into and out of Sydney (e.g., Miniopterus schreibersii oceanensis is most abundant in Sydney in

autumn and winter as it overwinters - (Gonsalves and Law 2014).



References Adams, M.D., Law, B.S. and French, K.O. (2005). Effect of lights on activity levels of forest bats:

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insectivorous bat activity over swimming pools retrofitted ... · use of swimming pools retrofitted...

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