Growling Grass Frog Assessment · and habitat usage within the study area. ... records recorded...
Transcript of Growling Grass Frog Assessment · and habitat usage within the study area. ... records recorded...
G ro w l i n g G ra s s F ro g As s e s s me n t
© E C O LO G I C AL AU S T R A L I A P T Y L T D i
Growling Grass Frog Assessment
Prepared for
Airservices Australia
21 May 2010
G ro w l i n g G ra s s F ro g As s e s s me n t
© E C O L O G I C AL AU S T R AL I A P T Y LT D ii
Growling Grass Frog Survey PREPARED FOR Airservices Australia
PROJECT NO 09CANENV-0001
DATE May 2010
DOCUMENT TRACKING
ITEM DETAIL
Project Name Growling Grass Frog Survey
Project Number 10CANENV-0001
Prepared by Matthew Dowle
Ross Wellington
Approved by Tom Kaveney
Status Final
Version Number V3
Last saved on 21 May 2010
ACKNOWLEDGEMENTS
This document has been prepared by Eco Logical Australia Pty Ltd with support from Airservices Australia. In particular Eco Logical Australia would like to thank Martin Hayes, Station Commander, ARFF Launceston for his assistance with the field surveys also Terry Soutberg and Ken Owen of Airservices Australia for their advice and review of this report. We would also like to thank Dennis Clayton, Launceston Airport for providing relevant literature, data and arranging access to nearby properties.
Disclaimer
This document may only be used for the purpose for which it was commissioned and in accordance with the contract between
Eco Logical Australia Pty Ltd and Airservices Australia. The scope of services was defined in consultation with Airservices
Australia. Changes to available information, legislation and schedules are made on an ongoing basis and readers should obtain
up to date information.
Eco Logical Australia Pty Ltd accepts no liability or responsibility whatsoever for or in respect of any use of or reliance upon this
report and its supporting material by any third party. Information provided is not intended to be a substitute for site specific
assessment or legal advice in relation to any matter. Unauthorised use of this report in any form is prohibited.
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Contents
1 Introduction .............................................................................................................................. 1
1.1 Background .............................................................................................................................. 1
1.2 Species Description ................................................................................................................. 1
1.3 Study Area ............................................................................................................................... 2
1.4 Study Aims ............................................................................................................................... 2
2 Methodology ............................................................................................................................ 4
2.1 Literature Review ..................................................................................................................... 4
2.2 Desktop Mapping ..................................................................................................................... 4
2.3 Field Survey ............................................................................................................................. 4
3 Results ..................................................................................................................................... 6
3.1 Field Survey ............................................................................................................................. 6
4 Discussion ............................................................................................................................. 12
5 Conclusion ............................................................................................................................. 13
5.1 Managment measures ........................................................................................................... 14
References .............................................................................................................................................. 16
Appendix A – Photos ............................................................................................................................... 18
List of Figures
Figure 1: Study Area .................................................................................................................................. 3
Figure 2: Growling Grass Frog records .................................................................................................... 11
List of Tables
Table 1: Growling Grass Frog (GGF) observations. .................................................................................. 7
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1 Introduction
Eco Logical Australia was commissioned by Airservices Australia to undertake a species and habitat
survey of the EPBC Act listed Litoria raniformis (Growling Grass Frog) within the Launceston Airport
and adjacent properties. This report details the field surveys undertaken to determine the current status
and habitat usage within the study area.
1.1 BACKGROUND
A population of the Growling Grass Frog is known to occupy a waste water lagoon at the Aviation
Rescue and Fire Fighting Services Drill Grounds (ARFFDG) at Launceston Airport. This facility is owned
and managed by Airservices Australia with other components of the Airport being leased and operated
from the Federal Government by Australia Pacific Airports (Launceston) Pty Ltd.
Eco Logical Australia was engaged by Airservices Australia to undertake an ecological study of the
Growling Grass Frog and to determine the current status of the species within the ARFFDG and also
investigate the species use of other potential habitat areas in the vicinity including other parts of the
airport and adjacent private land.
1.2 SPECIES DESCRIPTION
The Growling Grass Frog (Litoria raniformis) is listed as threatened under State and Commonwealth
legislation. It’s listed as vulnerable under the Commonwealth’s Environment Protection and Biodiversity
Conservation Act 1999, Tasmania’s Threatened Species Protection Act 1995 and South Australia’s
Naitonal Parks and Wildlife Act 1972 and listed as endangered under Victoria’s Flora and Fauna
Guarantee Act 1988, and New South Wales Threatened Species Conservation Act 1995.
The Growling Grass Frog is a medium to large sized frog (up to 85mm) that varies from dull olive to
bright emerald-green with irregular gold, brown, black or bronze spotting and a pale green stripe down
the centre of the back. The variation in colour and patterning is natural phenomenon within populations.
Individual colouring can change slightly and may be much darker during cold weather and when frogs
are inactive but just a darker or lighter colour shade of the original patterning.
The Growling Grass Frog usually prefers permanent lagoons, lakes, ponds and dams especially those
with emergent vegetation and are dependent on freshwater for breeding. Breeding occurs during the
warmer months during spring and summer and is triggered by flooding or a significant rise in water
levels. Growling Grass Frogs like most frogs in the bell frog complex are known to overwinter
(hibernation) under logs, rocks and beneath thick vegetation. The Green and Gold Bell Frog, a closely
related species to the Growling Grass Frog as also been recorded overwintering beneath objects
imbedded in mud, however this likely to have been caused by a inundation of water turning the dry
ground to mud.
Dispersal occurs outside the breeding season where animals disperse away from the water and take
shelter beneath ground debris such as fallen timber and bark, rocks, grass clumps and in deep soil
cracks. They generally feed on invertebrates as well as other small frogs, including young of their own
species.
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1.3 STUDY AREA
The ARFFDG is located on the edge of an elevated plateau on the north eastern side of the Launceston
Airports main runway and is accessed via an internal perimeter roadway (Figure 1).
The ARFFDG is currently and has been historically used as a regular fire training and drills site. It
consists of a large concrete platform and mock-up aircraft fuselage which is lit during drills and
extinguished using Aqueous film-forming foam (AFFF). Run-off from the mock-up fuselage and concrete
platform drains into a drill ground separator system to filter the unburnt Hydrocarbons and other
impurities. However, potentially not all impurities are filtered and run-off drains into the retention / water
treatment pond to the south east of the ARFFDG.
The retention pond is approximately 10 metres by 10 metres and 1 metre deep with an embankment on
the eastern, southern and western edges. The pond has a large build up of algae on the surface and
fringing vegetation consisting of pasture grasses, blackberry and a small stand of bulrushes.
Drainage from the airport and other slightly elevated rural and industrial lands is to the north east along
a number of small drainage lines that enter Rose Rivulet 3-4 km to the north east and ultimately the
North Esk River.
1.4 STUDY AIMS
Airservices Australia is cognisant of its obligations under the Environment Protection and Biodiversity
Conservation Act 1999 (EPBC Act), Airports Act 1996 and Launceston Airport Environment Strategy.
Based on these obligations Airservices Australia identified the need to conduct an assessment and
survey of the local Growling Grass Frog population within the Launceston airport grounds and
surrounding area.
This study was aimed at establishing the current status of the species in the area and capture of
population data about the species in the locality and the extent of utilised and potential habitat. This
information being viewed as fundamental to ongoing use and management of the facility and the wider
airport environs.
Specifically Eco Logical Australia was commissioned to conduct an ecological study of the threatened
species Litoria raniformis (Growling Grass frog) at the ARFFDG. The study was designed to provide
specific information on why, when and how the species utilises the Drill Ground (including the waste
water lagoon). A methodology was adopted that would assist in identifying if differences exist between
the structure and morphological traits of the Drill Ground population compared to the other surveyed
populations.
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Figure 1: Study Area
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2 Methodology
This section details the methodology followed for the field survey and literature review
2.1 LITERATURE REVIEW
A literature review of existing relevant information was conducted in order to gain an understanding of
the known and potential ecological values of the Growling Grass Frog and biodiversity values of the site
and broader study area.
Database searches of the Commonwealth Department of the Environment, Water, Heritage and the
Arts’ (DEWHA) Environmental Reporting Tool and the Natural Values Atlas of the Tasmanian
Government Department of Primary Industries and Water were undertaken. A search radius of 5 km
from the boundaries of the study area was used. The searches were carried out on the 14th February
2010. Database records indicated that whilst the area is known to be within the distribution range of the
species, there were no recent (last 10 years) records recorded within the 5km radius of the study area.
Limited literature pertaining to the survey site is available. However, a report conducted by Wapstra
(1999) for the Threatened Species Unit, Parks Wildlife Service and Launceston Airport was conducted
over a decade ago in April 1999. Wapstra also surveyed the Aviation Rescue & Fire Fighting Drill
Ground (ARFFDG), the farm dam 200m east of the ARFFDG (Pond 2) and other drainage lines and
possible habitats within the airport grounds. Wapstra recorded 10 individuals (2 adults and 8 sub-adults)
at the ARFFDG and over 25 individuals at the nearby farm dam. No frogs were recorded elsewhere on
the airport grounds and no tadpoles were found in either pond. Wapstra also identified that the large
ponds further to the east may be possible habitat. These ponds are referred to as Pond 3 and Pond 4 in
this report.
Following the literature review and database searches a range of spatial data sets including aerial
photography were used in order to determine physical attributes of the site prior to field investigations.
This spatial data was used to obtain an idea of potential species habitat outside of the airport and
potential drainage networks likely to link habitats.
2.2 DESKTOP MAPPING
Desktop mapping for the study was informed from the literature review and field investigations. Maps
were produced using ArcMap software with projected data in Australian Map Grid Zone 55.
2.3 FIELD SURVEY
The field surveys conducted used standard techniques for undertaking frog surveys. This included
diurnal inspection of suitable habitat areas and searching beneath potential ground shelter materials
including rocks, logs and other debris. It also included scanning vegetation in the vicinity of water bodies
for basking individuals.
Day time searches for tadpoles were undertaken and included visual scanning of the shallow margins of
waterbodies and the use of a dip net. Large tadpoles were identified visually and smaller individuals
were photographed for later identification from mouth part features.
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Call imitation, using a call playback of pre-recorded Growling Grass Frog calls was conducted at night
to attempt to elicit a call response from inactive individuals sheltering amongst vegetation and where
camouflage makes it difficult for these individuals to be detected.
Nocturnal timed searches (15 minutes) included the use of headlamps and spotlights to search the
margins of water bodies, fringing vegetation of the relevant ponds and of surrounding paddock areas.
Opportunistic searches included random meanders across grassy areas that provide potential foraging
habitat. Counts produced are only considered estimates as it was unlikely that all frogs present were
detected. Many auditory observations of frogs moving into water bodies were likely to be Growling
Grass Frogs so counts are likely to be serious underestimates of numbers at each site.
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3 Results
The principle aim of the field surveys was to determine the baseline population data of Growling Grass
Frogs within the study area. This section describes the results of the field surveys.
3.1 FIELD SURVEY
Eco Logical Australia conducted three field surveys (diurnal and timed nocturnal searches) a month
apart on the 27th-29
th January, 25th February and 31
st March. The water treatment pond associated with
the Aviation Rescue and Fire Fighting Services Drill Grounds was the primary target for frog searches.
Identified potential habitat within and surrounding the Launceston Airport was also targeted. The ponds
surveyed are shown in Figure 2.
Growling Grass Frog specimens varied in colour and patterning from predominantly brown to vivid
green. Some individuals displayed heavily splotched and patterned backs whiles others were plain. Mid-
dorsal vertebral striping was prominent in some but faint and less obvious in others. The variation in
colour and patterning is common within populations of the Growling Grass Frog. There was no
predominance of a particular variant cross a pond or between different ponds.
The labelling of the Ponds and brief description are outlined below and shown in Figure 1.
Approximate position of Growling Grass Frog specimens observed during the field surveys are shown in
Figure 2.
• Pond 1 = Aviation Rescue & Fire Fighting Drill Ground retention / water treatment pond.
• Pond 2 = farm dam - the pond immediately downslope of the drill ground but upslope (west) of
the railway embankment.
• Pond 3 = farm dam downslope (east) of the railway.
• Pond 4 = large farm dam downslope (east) of the railway.
Growling Grass Frogs observed were classified into three size classes:
• Adults – fully grown individuals at approximately 50-80mm.
• Sub-adults – consisted of the majority of observations and ranged from newly emerged frogs to
juveniles to sub-adults at approximately 25-50mm.
• Tadpoles – were considered to be tadpoles and froglets before the metamorphic stage of
becoming a frog.
All animals observed were in a healthy, natural state. No morphological irregularities or unusual forms
or behaviours were observed. A full range of life cycle stages and sizes were observed indicating a
normal breeding population exists in the study area.
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Table 1: Growling Grass Frog (GGF) observations.
Field Survey 1
(27th-29
th Jan 2010)
Field Survey 2
(25th Feb 2010)
Field Survey 3
(31st Mar 2010)
Diurnal Nocturnal Diurnal Nocturnal Diurnal Nocturnal
Pond 1
10GGF
10 sub-adults
200+ tadpoles
82 GGF
7 adults
75 sub-adults
5 GGF
5 sub-adults
50+ tadpoles
72 GGF
High majority of sub-adults
Not surveyed 9 GGF
9 sub-adults
Pond 2 Not surveyed
33 GGF
22 adults
11 sub-adults
3 GGF
3 sub-adults
Many tadpoles
52 GGF
High majority of sub-adults
Not surveyed
35 GGF
High majority of adults
Pond 3 Not surveyed Not surveyed
6 GGF
6 sub-adults
15 GGF
Majority of sub-adults
Not surveyed
17 GGF
1 adult
16 sub-adults
Pond 4 Not surveyed Not surveyed
2 GGF
2 sub-adults Not surveyed Not surveyed
3 GGF
1 adult
2 sub-adults
GGF = Growling Grass Frog (Litoria raniformis).
First Field Survey
Diurnal and nocturnal searches of the ARFFDG lagoon along with other areas of identified potential
habitat within and surrounding Launceston Airport was surveyed on 27th, 28
th and 29
th January 2010.
The water treatment pond was determined to have less than 25% in potential water surface area
currently held and the water margins were 2-4 meters from the fringing vegetation and embankment. At
capacity the dam is estimated to be approximately 18m wide and 45m in length.
On 27th
January 2010 Pond 1 was observed to contain several hundred tadpoles of the Growling Grass
Frog. The tadpoles were all large ca 60-75 mm total length and in advanced stages of development.
Potential frog shelter sites around the perimeter of the pond included pieces of timber and pieces of
concrete and basalt. These shelter sites were searched to reveal 10 sub adult (35-40mm) specimens of
the Growling Grass Frog, two specimens of the Spotted Marsh Frog (Limnodynastes tasmaniensis) and
two very small sub-adults of the Whistling Grass Frog (Litoria ewingii).
The 27th January 2010 nocturnal search took place between 20.30 and 23.30 hours at the same
location and revealed an estimated total of 82 Growling Grass Frogs. Seven of which were classed as
adults and the remaining 75 as sub-adults.
The specimens were generally observed foraging around the perimeter of the pond, the embankment
vegetation of the ponds, drainage pipes and in the grassy swales of the pond area, including in areas
west of the perimeter service road. Many of the frogs were observed emerging from earth cracks that
were prevalent in the deeply cracking soils that typify the area.
On the 28th January 2010 a diurnal reconnaissance of surrounding areas was undertaken to attempt to
locate other potential habitat areas, prioritise sites for subsequent nocturnal searches and also to
determine strategic factors likely to influence dispersal of the species. Farm dams at the ends of
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Trafalgar and Davies Lanes were very briefly searched for evidence of tadpoles and none were
observed. Detailed searches of these potential habitat areas were not undertaken due to access issues.
Nocturnal searches were conducted between 20.30 and 23.00 (28th January) and included searches
undertaken across the grassy areas of the catchment to the north and east of the ARFFDG. These
areas had extensive deeply cracking soils that had a high occupancy by small black crickets which
would are likely a food source for the Growling Grass Frog.
A total of 24 Growling Grass Frogs were observed downslope of the ARFFDG, of which two were sub-
adults (35-40mm) adjacent to the railway embankment. Twenty-two larger adult (60-75mm) individuals
were found in and around the fringing vegetation of Pond 2 and amongst the surrounding grassy areas.
Many individuals were again observed utilising the deep earth cracks as they emerged on dark.
No Growling Grass Frog tadpoles were observed during January in Pond 2 as the water was too deep
and spot lights could not pick up any tadpole activity near the surface at night. Tadpoles of the Growling
Grass Frog have however previously been detected in this farm dam (Wapstra, 1999) (see also second
field survey results below). Two near metamorphosis Whistling Grass Frog specimens were observed
near the surface of the farm dam.
The grassy paddock area adjacent to the farmland just downslope of the ARFFDG revealed 9 sub-adult
Growling Grass Frog individuals. These were all 30-40mm individuals and several were observed
emerging from deep earth cracks.
On the 29th January two storm water culverts and associated detention structures on the eastern side of
the airport were identified as having potential foraging, shelter and connectivity habitat for the Growling
Grass Frog. Both these drainages were searched and show evidence of high velocity flows from storm
event runoff but still retain connectivity and other habitat potential. The significant Cumbungi
swamp/detention area adjacent to the Hertz Car Rentals and Tankworld also has habitat potential.
No frogs were observed during our searches of these areas. This does not rule out their value as
occasional or intermittent use and for migratory movements to and from the established areas of
breeding habitat. Previous contractors operating in the vicinity of the navigational beacon, in the centre
of the airport grounds, had reported seeing a “large green frog” in this area of the airport (Martin Hayes
pers. comm.). This location is approximately midway between the ARFFDG and Cumbungi
swamp/detention area.
Second Field Survey
A diurnal and nocturnal search of the study area was conducted on the 25th February 2010. Surveys
were conducted between 17.30 and 20.00 AEDST and after dark between 21.30 and 23.45 AEDST.
Between the first and second field surveys Pond 1 had further retreated another 20-100cm around its
margins.
The areas visited diurnally include Pond 1 and Pond 2. A further reconnaissance was undertaken
downslope of the railway to Pond 3 and Pond 4. Ponds 1, 2 and 3 were visited nocturnally and timed
counts were undertaken at each pond and opportunistically whilst travelling between ponds.
Diurnal searches around Pond 1 revealed 5 recently metamorphosed and juvenile Growling Grass
Frogs sheltering beneath pieces of concrete, basalt and other debris. Large sheets of crusted algae
were observed across much of the pond surface or just below the surface and around the marginal
metre of the pond. The algae were being used by many soon to emerge or recently metamorphosed
Growling Grass Frog individuals as cover, floatation support or for basking.
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On approach an uncountable number (ca over 100) submerged or jumped from the algal mats.
Growling Grass Frog tadpole sampling in Pond 1 revealed froglets at or very near metamorphosis with
tail buds at various stages of resorption.
A search of Pond 2 revealed three diurnally basking or active individuals but others were heard jumping
into the water on our approach. Tadpole sampling at Pond 2 revealed Spotted Marsh Frog tadpoles. No
Growling Grass Frog tadpoles were collected but recently metamorphosed froglets were observed
active around the margin of Pond 2.
Numerous frogs were heard escaping along the margins of Pond 3 but the dense fringing vegetation of
this pond made visual detection more difficult and the frogs in this pond were more evasive. Only a
small number (6) were observed but actual numbers are likely much higher.
Pond 4 is a much larger water body with extensive areas of shelter and foraging habitat around its
margins. The pond ‘containment wall’ at the eastern end has ironstone boulders along the dam wall.
Two Growling Grass Frog sub-adults were detected sheltering under some of these rocks and some
suspected splashing noises heard were also likely to be this species.
Nocturnal searches on the 25th February revealed 72 Growling Grass Frogs around the margin of Pond
1 and surrounding grassy areas as well as within the drainage pipe beneath the entry track to the drill
ground facility.
A timed search around Pond 2 revealed approximately 52 frogs that were either active around the
margin of the pond, sheltering amongst the fringing sedges or floating in the water near or within the
fringing vegetation. Spotted Marsh Frogs were heard calling around the margins of pond 2 and a foamy
egg mass typical of this species was also observed.
A timed search around Pond 3 produced a count of 15 frogs. However many more were heard eluding
the searches upon approach at various sections of the pond.
Opportunistic observations during the February survey included several Spotted Marsh Frogs beneath
rocks and timber near the electrified fence paddock. Other opportunistic Growling Grass Frog
observations included individuals in the grassy area near the railway crossing gate, in the grassy
paddock approximately half way between pond 3 and the railway gate. Whistling Grass Frogs were also
heard calling at several locations.
Third Field Survey
A nocturnal search of Ponds 1-4 was conducted on the 31st March 2010 during warm and humid
conditions (18 °C) for this time of the year. Surveys were conducted between 19:40 – 21:40 AEDST.
Lower counts across all ponds were observed as expected due to a number of individuals presumably
starting to take refuge for winter. A number of depth earth cracks were evident in the surrounding areas,
but no crickets were evident as in the previous two surveys.
A timed search around Pond 1 revealed 3 sub-adult (25-40mm) Growling Grass Frog individuals active
around the margin of the pond and just below the surface of the pond resting on the crusted algae.
Additionally six adults (ca 50-55mm) were observed in the surrounding grassy swales of the airport land
adjacent to the pond. One individual Whistling Grass Frog was also observed in the grassy swales.
A timed search of Pond 2 revealed 35 Growling Grass Frog individuals either active in the emergent
vegetation of the pond, resting on the fringing vegetation or around the margin of the pond. The majority
of individuals were adults (60-80mm) with the smallest individual observed being 45-50mm.
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Additionally, three Growling Grass Frog individuals were observed on route between Pond 2 and Pond
3 (Figure 2).
A timed search of Pond 3 revealed 17 Growling Grass Frog individuals mostly around the emergent
vegetation of the pond. Most individuals were sub-adults (45-50mm) with one adult (80mm) individual
observed. A number of other individuals were heard jumping into the pond upon approach.
A timed search of the southern bank of Pond 4 revealed 3 Growling Grass Frog individuals. Two sub-
adults (25-30mm) were observed and one adult (65-70mm). The remaining banks of Pond 4 were
inaccessible at the time of the survey.
A search of the drainage channel on the east of the airport grounds was undertaken but failed to find
any frogs. Unlike in previous surveys this area was quite wet and contained standing water.
Opportunistic Herptofauna
A number of other herptofauna was opportunistically observed in the study area over the three surveys.
This included the Common Froglet (Crinia signifera), Whistling Grass Frog / Brown Tree Frog (Litoria
ewingii), Spotted Marsh Frog (Limnodynastes tasmaniensis), Metallic Skink (Carinascincus metallicum),
and Blotched Blue-tongue (Tiliqua nigrolutea).
.
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Figure 2: Growling Grass Frog records
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4 Discussion
The ARFFDG lagoon (Pond 1) is currently utilised as breeding habitat for the Growling Grass Frog and
this is known to have been the case for more than 10 years (Wapstra 1999; M. Hayes pers. comm.).
Wapstra (1999) provides a comparative survey of the lagoon which revealed similar results to the third
survey undertaken as part of this study. The numbers of adults recorded at Pond 1 and Pond 2 were
similar as were the lack of tadpoles which was probably due the time of year (Wapstra; mid April 1999,
Eco Logical Australia: late March 2010). Pond 2 was being utilised as breeding habitat and the lack of
frog presence elsewhere in the airport grounds are also notable similarities between the two studies.
Lastly Wapstra identified the ponds east of the railway line as potential habitat areas, although he did
not conduct surveys of these at the time. Two of these ponds (Ponds 3 and Pond 4) have been
confirmed during the recent surveys as Growling Grass Frogs habitat.
The results of this study indicate strongly that a breeding event during the 2009/2010 breeding season
is likely to have taken place at or around late November and this coincides with a significant wet
episode at about this time. This is based on the stage of development of tadpoles observed (assuming
typical growth rates 12-14 weeks) at Pond 1 and the presence of juvenile frogs in the vicinity.
The February visitation of railway Pond 2 revealed several recently emerged metamorphlings which
would also suggest that a breeding event took place at this location. Similarly, metamorphlings and
small juveniles (~20-25mm size class individuals) were observed around Ponds 3 and 4 which are likely
indicative of breeding in these ponds.
The area surrounding the ARFFDG has characteristic soils that are deeply cracking forming
crevices/fissures that extend for considerable depth. This microhabitat attribute is used by Growling
Grass Frog for shelter by day and is likely to be used for longer periods during unfavourable conditions
and possibly as a source of invertebrate prey that were observed to co-occupy these crevices. Growling
Grass Frogs are generally voracious predators of invertebrates and have been observed feeding on
crickets at other sites and in captivity (pers. obs. R.Wellington).
Movement patterns were not observed however it seems almost certain that given the Growling Grass
Frogs high mobility and the close proximity of the two pond sites to one another that movements
between sites would regularly take place. The number of Growling Grass Frogs observed in the grassy
paddocks on route between each pond, suggests this may be the case. Frogs were found up to 500m
from the nearest pond.
The extensive areas of grass that make up the north eastern side of the airport and grassed ancillary
light aircraft landing field are also likely to provide some potential foraging habitat for the Growling
Grass Frog and a relatively unrestricted movement corridor to the modified drainage lines that lead to
the more highly developed upper parts of the catchment.
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5 Conclusion
The similarities of results between this study and the work of Wapstra show a historical connection and
usage of the relevant ponds as longer-term Growling Grass Frog habitat. However the presence of the
species a decade apart does not necessarily mean that there has been continual occupation of the site
by the species throughout this 11 year period. In fact anecdotal evidence (Martin Hayes pers comm.)
indicates that Airport staff has noted both a presence and absence of the frogs at different times over
the past 5-10 years.
Recent results show that presently there is a large healthy and viable breeding population of Growling
Grass Frogs utilising the ARFFDG lagoon, surrounding grassy areas and the series of down slope
ponds running east of the airport. The numbers, appearance and population structure of the Growling
Grass Frogs surveyed appears to be representative of the type and structure of other known Growling
Grass Frog populations. The frogs appeared to have a physically healthy appearance. They also have
‘rough’ age class cohorts that are indicative of recruitment over a number of seasons (at least three age
class cohorts observed at each pond). There were male and female adults in proportions that were
approximately 50:50 for those adults that were captured and held in hand.
The broader population is estimated to be 300+ in number although this number could vary significantly
during the year following breeding events. A considerable number of larger (potentially breeding size)
adults were recorded and there were extremely high numbers of tadpoles, metamorphlings and juvenile
frogs detected. No obvious variation in morphological traits were observed other than a greater number
of larger size individuals in the downslope dams (Ponds 2-4) which is likely just a factor of movement
away from the major breeding pond (Pond 1) seeking resources, greater cover and less competition
downslope. Longer term recruitment and survival rates for the population cannot be determined from
this study. However, with appropriate ongoing management and preservation of habitat areas it is
expected that the species will persist at this location either permanently or as a cyclic population when
conditions are favourable.
Specifically, the ARFFDG lagoon (water treatment pond – Pond 1) represents what would appear to be
an important breeding and dispersal site for the species. The large numbers of tadpoles observed
during the March and February surveys are an indication that the lagoon plays a potentially vital role in
the recruitment of frogs into the broader population. Equally the other ponds to the east would also
appear to be breeding habitat although tadpole numbers indicate to a lesser extent than the ARFFDG
lagoon.
The surveys revealed a presence of Growling Grass Frog individuals at ponds associated with the
runoff of substances from the ARFFDG ground and an absence of individuals at ponds that receive no
direct anthropogenic substances. The contamination of the water treatment pond from substances and
excess runoff coming from the ARFFDG ground is possibly either ‘warding’ off or attenuating frog
Chytrid.
The results of this survey combined with Wapstra (1999) could be used to compare against future
investigations into the Growling Grass Frog populations within Launceston airport and nearby
surrounds. Within the current study, timed searches of local ponds were conducted and not all frogs at
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each pond were observed or captured nor were all frogs able to be measured. Thus a statistical
analysis using the current results as baseline data is not recommended, however general trends evident
from the results of this report and Wapstra (1999) could be used for basic comparisons in future studies.
The population of Growling Grass Frogs at Launceston Airport and nearby surrounds would likely to be
considered under State (Tasmanian) and Commonwealth criteria as an important population.
Suggested management arrangements and further studies are outlined below.
5.1 MANAGMENT MEASURES
It is understood that Airservices Australia intends to continue to use and manage the ARFFDG
consistent with current arrangements. Current management arrangements do not appear to be having
an adverse impact on the frog population, in fact current operations may be beneficial to the presence
and persistence of frogs at the site.
Airservices Australia has responsibilities and legal (EPBC Act) requirements to ensure that its activities
at Launceston Airport do not have a significant detrimental impact upon this threatened species.
Depending on the type of activities and management actions undertaken there could be an overall
positive or negative impact on the local frog population.
Eco Logical Australia suggests that a separate management plan is not necessary at this time. The
actions undertaken by Airservices Australia staff to date have been sympathetic to the current Growling
Grass Frog population. With careful management the coexistence of a healthy frog population and
active Drill Ground operations should be able to be maintained. However, any major changes to the
management actions and routines may lead to unwanted and unpredictable changes to the Growling
Grass Frog. Should major changes or physical works be proposed for the ARFFDG Airservices
Australia should undertake an assessment of the impacts to Growling Grass Frogs before implementing
the changes.
The following management practices should be sufficient to maintain and enhance the Growling Grass
Frog population within the ARFFDG:
• Mowing in the grassed area around the water treatment pond to avoid periods of high frog
activity and breeding times. This specifically requires caution during the high activity months of
October to April.
• Avoid spraying pesticides and herbicides within close proximity (10m) to the water treatment
ponds where there is a risk of contact with Growling Grass Frog individuals. If the Blackberry
bush surrounding the pond is required to be removed, then an alternative means is
recommended. It is recommended mechanical methods be used, however, if herbicides are
needed, then the spraying of the herbicide should be conducted outside times of high activity
and breeding (periods between October and April).
• Maintain reasonable water levels in the water treatment pond particularly from October to April.
This may be achieved through normal drill operations or deliberate filling.
• Possible placement of habitat materials in and within close proximity to the water treatment
pond, such as logs or rocks to provide shelter and wintering habitat. This would provide
additional shelter for the frogs during summer and over the winter months and encourage
augmentation of the population and individual frogs at the water treatment pond.
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© E C O L O G I C AL AU S T R AL I A P T Y LT D 15
• Co-operation and sympathetic management with adjacent land owners to provide and maintain
suitable habitat for the Growling Grass Frog.
Management practices Airservices Australia could undertake to enhance the understanding and
knowledge base of the local Growling Grass Frog population:
• Future surveys of the Growling Grass Frogs to include:
o Continued and ongoing monitoring from fire station staff to record frogs during
operational activities at the ARFFDG. Monitoring could include general observations
during drill procedures to a detailed 20 minute timed observation of Pond 1 during dusk
at times of optimal activity (October to April). The numbers of frogs and size classes
could be recorded and enter into a database/spreadsheet.
o Annual surveys for 2 to 3 nights during peak activity times, particularly October to April.
Surveys should be conducted in association with the Airport and surrounding property
owners and include suitable habitat within the airport grounds, neighbouring properties
and drainage lines to detect changes in numbers and habitat use.
• Investigate a link between substances present in the ARFFDG water quality control ponds and
the presence and evident successful breeding of the Growling Grass Frog in this habitat.
• Review of management arrangements in 3 year intervals to incorporate the collation of
observations and survey data.
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© E C O L O G I C AL AU S T R AL I A P T Y LT D 16
References
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190
Wapstra, E. (1999) Assessment of the Green and Gold Frog (Litoria raniformis) at the Launceston
Airport. Report to the Threatened Species Unit, Tasmanian Parks and Wildlife Service and Launceston
Airport. April 1999
Department of Environment and Climate Change (2008) Hygiene Protocol for the Control of Disease in
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Bell Frog Key Population Management Plan. DECC 2008/139, August 2008 - Hurstville, NSW
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Frog – Epping/Somerton, Victoria. Report prepared by Ecology Australia Pty Ltd for Victorian
Department of Primary Industries. Project: 06-24
Department of Primary Industries, Water and Environment (2001) Threatened Species Listing
Statement Green and Golden Frog, Litoria raniformis Keferstein 1867. Threatened Species Unit
Tasmanian Department of Primary Industries, Water and Environment, March 2001
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Litoria raniformis (Draft - DSE July 2007)
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Canberra, August 2009.
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G ro w l i n g G ra s s F ro g As s e s s me n t
© E C O L O G I C AL AU S T R AL I A P T Y LT D 17
Heard, G.W., Robertson, P. and Scroggie, M.P. (2006) Assessing detection probabilities for the
endangered Growling Grass Frog (Litoria raniformis) in Southern Victoria. Wildlife Research 33: 557-
564
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Green and Golden Bell Frog Litoria aurea (Lesson, 1829). Hurstville, NSW.
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Australian Zoologist 32(1): 32-48
Robertson, P. (2007) Draft Action Statement for the Growling Grass Frog Litoria raniformis. Flora and
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Victoria
Robertson, P., Heard, G. and Scroggie, M. (2002) The ecology and conservation status of the Growling
Grass Frog (Litoria raniformis) within the Merri Creek Corridor. Interim Report: Distribution, abundance
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Grass Frog Litoria raniformis in the area of proposed drainage works, Benwell-Koondrook Region.
Arthur Rylah Institute for Environmental Research. DSE Heidelberg, Vic, April 2003
Wassens, S. (2008) Review of the past distribution and decline of the Southern Bell Frog Litoria
raniformis in New South Wales. Australian Zoologist 34(3): 446-452
Wassens, S. Watts, R.J., Jansen, A. and Roshier D. (2008) Movement patterns of southern bell frogs
(Litoria raniformis) in response to flooding. Wildlife Research 35: 50-58
White, A.W. and Pyke, G.H. (1999) Past distribution of Litoria aurea and Litoria castenea in the
Bathurst-Orange area of New South Wales. Herpetofauna 29 (1): 2-9
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Appendix A – Photos
Plate 1: Air Rescue Fire Fighting Drill Ground. Plate 2: Pond 1, Water Treatment Pond.
Plate 3: Growling Grass Frog Litoria raniformis. Plate 4: Growling Grass Frog Litoria raniformis.
Plate 5: Growling Grass Frog (Litoria raniformis) & Spotted Marsh Frog (Limnodynastes tasmaniensis).
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