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


© 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.


© E C O L O G I C AL AU S T R AL I A P T Y LT D iii

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


© E C O L O G I C AL AU S T R AL I A P T Y LT D 1

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.



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.



Figure 1: Study Area



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.



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.



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.



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



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.



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.



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).

.



Figure 2: Growling Grass Frog records



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.



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



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.



• 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.



References

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Heard, G.W., Robertson, P. and Scroggie, M.P. (2006) Assessing detection probabilities for the

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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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