2016

SOUTHERN CROSS UNIVERSITY

SCHOOL OF ENVIRONMENT, SCIENCE AND ENGINEERING

POPULATION MONITORING OF GREEN AND GOLDEN BELL FROG

(L. AUREA)

AT THE NORTHERN EXTENT OF ITS RANGE.

JENINE DEMPSTER

1

This report has been prepared by an undergraduate student and may not have been

corrected according to the comments of University staff. The report should be cited in

the following format: Dempster, J.A. (2016). Population monitoring of Green and

Golden Bell Frog (L. Aurea) At the northern extent of its range. Unpublished Third

Year Undergraduate Report. School of Environment, Science and Engineering,

Southern Cross University, Lismore.

2

POPULATION MONITORING OF GREEN AND GOLDEN BELL FROG

(L. AUREA)

AT THE NORTHERN EXTENT OF ITS RANGE.

Prepared by Jenine Dempster

Integrated Project prepared as partial fulfilment of the requirements

of the Bachelor of Environmental Science

Southern Cross University

2016

Copyright

3

I, Jenine Dempster, consent to this report being made available for photocopying and

loan, provided that my work is fully acknowledged and that the granting of such a

licence in no way inhibits me from exercising any of my exclusive rights under the

Copyright Act 1968. I understand this licence is granted in the interests of education and

research and that no royalties are payable.

Jenine Dempster 10th

June 2016

4

Acknowledgements

I wish to thank my supervisors David Newell and Ross Goldingay for their wealth of

knowledge on the subject, patience in the field, and support during the write up. I am

also extremely grateful to Jonathan Parkyn for his help with the data analysis and

additional advice he provided. Special thanks also to Craig Taylor for organising and

supplying gear for the field work, but more importantly for some great guidance at the

start of the project. Finally to my mother Judith and my partner Mark who went above

and beyond to provide me with the support and encouragement to believe in myself.

5

Abstract The green and golden bell frog (Litoria aurea) has experienced a

considerable range reduction and population decline over the last 20 years

in NSW. Once ranging from Victoria to Byron Bay, L. aurea has now

contracted from its northern range limits. The most northern extent of L.

aurea currently exists within Yuraygir National Park NSW. These northern

populations are small and therefore prone to extinction through inbreeding,

genetic drift and other environmental factors. Consequently the populations

of L. aurea in Yuraygir National Park are considered to be of high

conservation significance. The most prominent threats to L. aurea include

predation by the plague minnow (Gambusia) and loss of breeding habitat.

The aim of this study was to continue monitoring of L. aurea populations at

the northern extent of their range. Nocturnal surveys conducted over six

night’s recorded 133 individuals, however only the 70 adult males were used

for POPAN analysis which determined abundance at 116. This is the same

estimate as previous studies; however the survey area and number of

occasions was less for this project suggesting the population has increased.

A long-term monitoring strategy is still required as there is too little

information available on life history parameters to ascertain if the numbers

observed can be interpreted as a viable population.

Key Words: Bell Frog, Litoria aurea, amphibian decline, population monitoring.

6

Contents Acknowledgements .............................................................................................................. 4

Abstract ................................................................................................................................ 5

1. Literature review .......................................................................................................... 8

1.1 Taxonomy of L. aurea ................................................................................................... 9

1.2 Biology and Physiology ................................................................................................. 9

1.3 Diet ................................................................................................................................ 10

1.4 Reproduction and Behaviour ..................................................................................... 10

1.5 Habitat requirements .................................................................................................. 10

1.6 Major threats to L. aurea ............................................................................................ 11

1.6.1 Predation by Gambusia holbrooki ............................................................................. 11

1.6.2 Pathogens ................................................................................................................... 11

1.6.3 Habitat loss and disturbance ...................................................................................... 12

1.6.4 Small Population ........................................................................................................ 12

1.6.5 Increased levels of ultraviolet radiation .................................................................... 12

2. Aims and Objectives ...................................................................................................... 13

3. Methods .......................................................................................................................... 13

3.1 Study area .................................................................................................................... 13

3.2 Climate and Rainfall ................................................................................................... 16

3.3 Survey Design .............................................................................................................. 16

3.4 Data analysis ................................................................................................................ 17

3.5 Additional Field work ................................................................................................. 17

4. Results ............................................................................................................................ 17

5. Discussion ....................................................................................................................... 19

5.1 Population stability ..................................................................................................... 19

5.2 Management options ................................................................................................... 20

References .......................................................................................................................... 22

Appendices ......................................................................................................................... 27

7

List of Tables and Figures

Figure 1. Blue Lake, Yuraygir National Park, NSW. Photo: J. Dempster. ................................. 15

Figure 2. Southern Swamp, Yuraygir National Park, NSW. Photo: J. Dempster. ...................... 15

Figure 3. Rainfall for 2014-2015 compared to mean. (BoM, 2016). .......................................... 16

Figure 4. Capture results for male, female and sub-adult L. aurea over six nights .................... 18

Figure 5. Colourmorphs of Yuraygir. Photos: D. Newell & R. Goldingay. ................................ 27

Figure 6. Male L. aurea on M. quinquinervia tree. Photo: R. Goldingay. .................................. 27

Table 1. POPAN model ............................................................................................................... 18

Table 2. Survivorship (phi), capture (p) and probability of entry (PENT) estimates. ................. 19

Table 3. Population estimate derived from POPAN 6 model. .................................................... 19

Map 1. Location of Yuraygir National Park and Station Creek Camping area. Source: Google

Earth, 2015. ................................................................................................................................. 14

Map 2. Location of Sampling sites, Blue Lake and Southern Swamp. Source: Google Earth,

2015. ............................................................................................................................................ 14

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1. Literature review

The decline in abundance and diversity of amphibians is considered to be a global

phenomenon, which began in the 1970’s (Stuart et al. 2004) with the simultaneous

disappearance of frog and toad species from points widely distributed across the globe.

It was initially thought there was a single cause or that it was purely coincidental and

that local environmental factors were to blame (Barinaga, 1990). There was insufficient

data on many species to ascertain if these population declines were simply normal

fluctuations (Lewis & Goldingay, 2005) or something of more concern. It was

recognised that declines and disappearances of amphibian populations over the last two

decades however, represented a distinct phenomenon that exceeded the problematic

issue of biodiversity loss and researchers began to try and discover the cause. There are

numerous hypotheses implicated in the decline, including global warming and increased

UV-B radiation, habitat destruction, and disease (Belden & Blaustein, 2002, Pyke &

White 2001, Kriger et al. 2007). Additional factors which may contribute to localised

frog declines include pollution, salinisation and predation by introduced species (Polo-

Cavia, et al. 2016; Stockwell, 2012; Pyke & White, 2001). However, researchers have

also investigating confirmed frog declines in apparently pristine, undisturbed habitats

(Eisemberg et al. 2016; Neckel-Oliveira et al 2013). Frogs are unique in that they have

a biphasic lifecycle making them vulnerable to impacts in both aquatic and terrestrial

environments (Tinto, 2015)

Populations of Australian frogs have followed the trend of global decline with fifty of

216 (23%) amphibian species now recognised as threatened or extinct in accord with

IUCN Red List Categories and Criteria (Hero et al. 2004). Worldwide, researchers have

confirmed frog declines in abundance and diversity in both pristine and disturbed

habitats (Blaustein, et al. 2011; Skerratt et al. 2007; Stuart, et al. 2004). Stuart et al.

(2004) have stated that Australia has significantly more enigmatic declines than the

world average. The causal agents proposed at the time of amphibian declines provided

no explanation for the disappearance of species including the Mt Glorious Torrent

Frog (Taudactylus diurnal), and the Gastric Brooding Frog, (Rheobatrachus silus). It is

important to note that frogs were not even recognised as fauna in Australia until 1991

when the Endangered Fauna (Interim Protection) Act amended the National Parks and

Wildlife Act 1974 (White, 1995).

Since the mid-1970s the Green and Golden Bell Frog (L. aurea) has experienced an

extensive reduction along the south east coast of Australia, and the species is now listed

as endangered in the New South Wales Threatened Species Conservation Act 1995

(TSC) and as vulnerable in the Commonwealth’s Environmental Protection and

Biodiversity Conservation Act 1999 (EPBC). The Green and Golden Bell Frog once

occupied 134 locations ranging from Byron Bay in northern NSW, to East Gippsland,

Victoria, and west to Bathurst and Tumut (White and Pyke, 1996) this number has now

been reduced to 47 known locations. Victorian populations appear stable, however,

Gillespie et al. (2011) question the certainty of some conservation assessments that may

at times underestimate the threats to populations.

9

Consequently, the populations of L. aurea in Yuraygir National Park are of great

significance in relation to the conservation of the species. Due to the decline in regional

populations, combined with the apparent isolation of the known populations in Yuraygir

these populations may be amongst the most threated of all known populations of the

species (Frankham, 2015; Luquet, 2015; Goldingay, 2008). The small size of these

populations indicates that L aurea will be particularly vulnerable to local extinction.

Further to this, MtDNA and microsatellite data collected by Burns et al. (2007) has

shown that more isolated northern populations of L aurea are highly differentiated from

those in the south demonstrating some genetic divergence. This may indicate that the

Yuraygir population is significant management unit. Colourmorphs of the Yuraygir

population certainly suggest some genetic variation from those populations located in

the south (Appendix 1). Further studies are required throughout Yuraygir NP to confirm

results of previous studies and to provide continued monitoring of the L aurea

populations in YNP to conserve all viable populations throughout the extent of their

geographic range (Goldingay 2008).

1.1 Taxonomy of L. aurea

Bell frogs are a distinct group within the Australo-Papuan hylid genus Litoria. There

are seven species within the group listed in Pyke and White (2001) comprising of

Southern Bell Frog (L. raniformis), Yellow Spotted Tree Frog (L. castanea); Moore’s

Frog (L. moorei), Dahl’s Aquatic Frog (L. dahlia), Striped Burrowing Frog (L.

alboguttata), Spotted Thighed Frog (L. cyclorhynchus). Litoria aurea can be

distinguished from similar species by its granular free skin, conspicuous toe and finger

disc and absence of spotting or marbling on the hide side of the thigh, with colouration

on its back being a distinctive feature.

1.2 Biology and Physiology

Green and golden bell frogs are one of the largest frogs in Australia with adult females

growing between 70- 85mm snout-vent length (SVL) whereas adult males reach 55-

70mm (White and Pyke 2001). The dorsal colouration of L. aurea ranges from

chocolate brown to dull olive to bright emerald green or brown, with coppery-gold

blotches on the back. The dorsal surface is smooth with a yellow dorso-lateral fold

extending from the eye to the groin. The belly and ventral surfaces of the thighs are

white and coarsely granulated. There is a pale or cream stripe which runs from above

the nostril over the eye and tympanum. The tympanum is distinct and gold in colour.

There is a distinctive area of blue-green colouration surrounding the groin and upper

thighs. Webbing is absent in the fingers, whereas the toes are almost entirely webbed.

Reproductively mature males have swollen thumbs, as a result of the development of

dark nuptial pads, which are used to clasp females during amplexis.

Green and golden bell frogs are possible the most highly fecund species of Australian

Frog with egg spawn masses averaging 3773 eggs (Pyke and White 2001). Tadpoles

hatch in approximately two days with development from tadpole to metamorphling

occurring between 2-12 months depending on climate. Tadpoles are not easily

characterised, as descriptions vary considerably from green with golden streaks

(Fletcher, cited in Pyke and White, 2001)), dull brown or dirty yellow (White 1995).

10

pinkish grey with yellowish fins (Frogs of Victoria, 2015) or a metallic golden lustre

(Hamer, cited in Pyke and White, 2001). Obviously this is not a reliable method for

identification, therefore body markings are usually used such as a distinctive canthal

stripe which flanks tadpoles > 1cm SVL. Other identifying features include a dorsal fin

extending nearly halfway up the back, lateral eyes and the mouth disc has to rows of

upper labial teeth, with three rows of teeth in the lower labium.

1.3 Diet

The diet of tadpoles varies with age, consisting of algae, organic detritus and bacteria,

progressing to a more carnivorous diet as they mature. Adult bell frogs are known to eat

a variety of invertebrates and small vertebrates with White (1995) suggesting that adults

will consume any moving prey that will fit in its mouth, including conspecifics and

other frog species. Frogs have been found to consume more during the warmer months,

however this corresponds with breeding season which Humphries (cited in Pyke and

White, 2001) states reduces foraging behaviour. Clearly more research is required in

this area if management plans are to be designed effectively.

1.4 Reproduction and Behaviour

Breeding occurs in the warmer months from Oct-Mar with male bell frogs calling to

attract females, while partly submerged in water. These vocalisations play an integral

part in the social and mating behaviour of frogs (Bleach, et al. 2015), as calls may not

only be intended to attract females, but also alert other males of their presence (Pyke

and Osborne, 1999).

In the event that amplexus between male and female L. aurea has occurred, egg spawn

masses become evident within 72hours. Breeding is generally restricted to ephemeral

ponds, which contain submergent and emergent aquatic vegetation.

1.5 Habitat requirements

Green and Golden Bell Frogs can be found in almost every type of still to slow moving

fresh water body, including farm dams, wetlands, swamps, creeks, lakes, lagoons,

constructed ponds and ephemeral ponds. Social cues such as the scent of conspecifics

may also play a key role in habitat selection in this species with not all of the above

habitats utilised when available (Pizzatto et al. 2016). Bell frogs have been known to

inhabit a vast range of heavily disturbed and moderately disturbed habitats. A

requirement is the presence of diurnal basking habitat which generally consists of

emergent aquatic vegetation or rocks. Litoria aurea are generally an aquatic species,

despite its classification as a Hylid; however male bell frogs were observed calling

whilst sitting in small trees (Appendix 2) and Typha orientalis during this study in

Yuraygir National Park, supporting the Hylid classification.

Bell frogs may seek shelter during the day amongst vegetation adjacent to or within the

vicinity of permanent water-bodies, for foraging. Over wintering habitat generally

consists of piles of rocks, vegetation or litter in which bell frogs can seek shelter for

hibernation during the colder months of the year (White and Pyke, 2015).

11

One of the largest known extant populations of L aurea in NSW occurs in the Greater

Sydney region and inhabits sites of high levels of disturbance (White and Pyke 1996).

Many of the largest populations can be found in these disturbed sites and this has led

some to postulate that this may be preferred habitat rather than no other habitat is

available and the frogs are forced to live in these areas due to loss of suitable habitat.

Research by Kearney et al. (2012) has also found that Green and Golden Bell Frogs

have a greater tolerance to salinity than other Australian anuran species with an 85%

larval survival rate in sodium concentrations of 16%. This may help the GGBF to

colonise habitats as refuges from competition and predation.

1.6 Major threats to L. aurea

1.6.1 Predation by Gambusia holbrooki

Listed as a key threatening process which has known or likely implications for the

Green and Golden Bell Frog under the Threatened Species Conservation Act 1995 is

predation by Gambusia holbrooki or the Plague Minnow. Gambusi holbrooki is a

voracious predator that feeds on both eggs and young tadpoles, while also preying on

tadpoles at later stages in their development (NPWS, 2003). Although White and Pyke

(2001) stipulate that the breeding success of L. aurea requires the water body to be free

of Gambusia and other predatory fish, there have been observations of successful

breeding in the presence of Gambusia (Hamer, et al. 2002; Goldingay and Lewis, 1999).

The size of the water body and the presence of aquatic and emergent vegetation in

addition to the density of fish, will determine the level of impact Gambusia has on Bell

Frog breeding efforts.

1.6.2 Pathogens

Chytrid fungus (Batrachochytrium dendrobatidis) possibly the most well-known of frog

pathogens implicated as one possibly cause for the decline of amphibian species across

the globe (Goldingay, 2008; Newell et al. 2013). In Australia it has caused the

extinction or decline of up to 17 frog species (Department of the Environment, 2012)

and this trend does not appear to be slowing. Batrachochytrium dendrobatidis which

causes chytridiomycosis was listed as a key threatening process in 2002 under the

Environmental Protection and Biodiversity Conservation Act 1999 (EPBC Act). The

bacteria effects the keratinised epithelia such as the skin of frogs and mouthparts of

tadpoles causing the skin to become tough and less permeable to water and essential

salts leading to eventual death.

Salinity levels may offer some benefits in precluding the fungus (Osbourne cited in

Goldingay, 2008) with Threlfall et al. (2008) suggesting fluctuating salinity in addition

to heavy metals copper and zinc may provide fungicidal benefits. This is supported by

Stockwell et al. (2015) who revealed that exposure to sodium chloride concentrations

>2ppt significantly reduced chytrid infection loads in Bell Frogs. Additionally it has

been suggested that antimicrobial peptides from skin glands on the bell frog may help to

control infection (Rollins-Smith et al. 2011).

12

Myxosporean parasites have been found in the liver and brain of Green and Golden Bell

Frogs (Hartigan et al. 2011). Originally thought to have been introduced with the Cane

Toad (Bufo marinus) it has since been discovered that the parasite carried by our native

frogs was not introduced by the toads but rather it is a native strain that has been

amplified by the susceptible invasive host species. The parasite has been found to cause

axonal lesions which interfere with neurological function and result in behavioural

changes such as lethargy and failure to breed in the Green and Golden Bell frogs

(Hartigan et al. 2011).

Ranaviruses while not frequently encountered in Australia are listed on the World

Organisation for Animal Health (OIE) as a notifiable disease which may help control

the introduction of pathogenic strains to the country.

1.6.3 Habitat loss and disturbance

Habitat loss and disturbance has been identified as one of the major threats facing the

Green and Golden Bell Frog (Goldingay, 2008; White and Pyke, 2008). Development

along the east coast of NSW has removed and fragmented up to 60 per cent of

freshwater wetlands (OEH, 2016), which are the frogs preferred habitat. Pyke and

White (2001) have reported that the majority of populations are now found in highly

disturbed areas possibly because these sites are all that remains of former breeding

habitats. Fragmentation can isolate frog populations, increasing the impacts of

inbreeding, limiting evolutionary potential and predispose populations to extinction

(DEC, 2005)

The site selected for this study was historically used for sand mining and cattle grazing

which has seen the development of sand blowouts in the area and trampling of aquatic

edge vegetation. The gazetting of the area as a National Park in 1980 (Australian

National Parks 2016) has seen the gradual regeneration of vegetation, however cattle

continue to occupy the site. The site has been protected from farming and development

that has occurred along the east coast due to its distance from major roads and towns.

This may have protected the population from threats such as disturbance and pollution

which affect other populations.

1.6.4 Small Population

Small populations created through habitat disturbance are subject to rapid demographic

fluctuations resulting from variations in birth and death rates. Environmental

fluctuations that cause a variation in food supplies, predation, disease, or competition,

combined with natural catastrophes such as fires, floods, storms or droughts can result

in the complete extinction of small populations that simply do not have the numbers or

genetic variability to withstand such events (Williams, Nichols, & Conroy, 2001)

1.6.5 Increased levels of ultraviolet radiation

Exposure to ultraviolet-B (UV-B) radiation has been implicated as a contributing factor

in the global decline of amphibians (Belden & Blaustein, 2001). Increased levels of

13

UV-B due to ozone depletion has been found to cause damage to DNA and reduce

photolyase levels which can repair such damage (Goldingay, 2008). Bell Frogs appear

to be less vulnerable to the harmful effects as eggs do not remain on the surface of the

water and hatch within about 3 days therefore receiving limited exposure to the

radiation (van de Mortel & Buttemer, 1996).

.

2. Aims and Objectives The aim of this study is to continue monitoring of the known L. aurea populations to aid

the conservation and population recovery of the species

Continued monitoring of previously known habitat of L. aurea to conduct

population surveys

Conduct nocturnal surveys at previously identified sites (Blue Lake and southern

swamp) during breeding season

Mark recapture method using PIT tagging and processing (measurements of

snout-urostyle length, weight, and sex determined)

.

3. Methods

3.1 Study area

The study was conducted in Yuraygir National Park (YNP) in North-eastern Australia

between November and December 2015. YNP occupies 21500 ha which extends 70km

along the coastline between the Corindi and Clarence Rivers and is one of the largest

undeveloped stretches of coastline in NSW (NPWS, 2016). The study area included

known L. aurea habitat at Station Creek which had previously identified by Goldingay

and Newell (2005). The rationale behind the selection of these sites was to continuing

monitoring of L. aurea populations at the most northern limit of their geographic range.

Two water bodies were surveyed using SM2 sound meters (Wildlife acoustics, 2016)

whilst Blue Lake and the southern swamp were surveyed using active search utilising

mark recapture methods.

The first documented report of L. aurea in YNP were from observations made by

Clancy in 1980 (Clancy, 1996) when a single individual was sighted. Later surveys

(Lewis and Goldingay, 1999) observed 10 or less individuals. The most recent study by

Goldingay and Newell (2005) identified >100 male frogs from two sites. For this study,

surveys were confined to these same two sites, Blue Lake and the Southern Swamp

(Map 1 & 2), with casual observations of ephemeral ponds.

14

Map 1. Location of Yuraygir National Park and Station Creek Camping area. Source: Google

Earth, 2015.

Map 2. Location of Sampling sites, Blue Lake and Southern Swamp. Source: Google Earth, 2015.

Blue lake (Figure 1) is a large coastal lagoon situated within a dunal complex with

Paperbark forest (Melaleuca quinquinervia) dominating the western boundary of the

lake. The eastern side of Blue Lake generally consists of swamp She-oak (Casuarina

glauca) forest. The perimeter of Blue Lake consists of emergent vegetation including

cumbungi (T. orientalis), common reed (Phragmites australis) and Sawsedge (Gahnia

15

clarkei), a sparse distribution of spikerush (Eleocharis acuta) and Blue water lily

(Nympaea capensis). Submergent vegetation identified consists of stonewort (Nitella

sp.) and yellow Bladderwort (Utricularia australis).

Figure 1. Blue Lake, Yuraygir National Park, NSW. Photo: J. Dempster.

Southern Swamp (Figure 2) connects to Blue Lake at its southern end when there is

sufficient rainfall and is ~ 0.3 ha in area to a depth of ~ 1metre. The western edge

vegetation consists of G. clarkei with M. quinquinervia. Aquatic vegetation is similar to

that found in Blue Lake.

Figure 2. Southern Swamp, Yuraygir National Park, NSW. Photo: J. Dempster.

16

3.2 Climate and Rainfall

The annual mean rainfall the Mid North Coast is 1669.5 mm, most of which falls during

the summer months. Summer temperatures are warm, averaging between 19 and 27°C

and winter temperatures range from minimums of seven to daily maximums of 19°C

(Bureau of Meteorology, 2016). The previous summer’s rainfall was above average

(Figure 3) which may have influenced numbers observed during sampling.

Figure 3. Rainfall for 2014-2015 compared to mean. (BoM, 2016).

3.3 Survey Design

The sampling design was structured into three sessions between 2 November 2015 and

8 December 2015, with three consecutive nights surveyed within each session. The

sessions were selected on the basis of suitable weather conditions and the availability of

staff. Minimal rainfall (2.8mm) was experienced in the five days preceding the survey.

Surveys were separated by intervals of 7- 27 days so that gains and losses to the

population could occur, although the period between the initial and second survey was

insufficient to demonstrate this. The population was assessed as closed at the time of

sampling. Catch Mark Recapture (CMR) data was obtained using the methods of

Goldingay and Newell (2005). The lake and swamp including adjacent vegetation were

traversed just after nightfall, both on foot and with kayaks. Pre-recorded calls of L.

aurea and mimicry were used to elicit responses from unseen males, and frogs were

then located by eye-shine from head torches.

Frogs were captured by hand and nets in separate plastic bags and their GPS location

documented and also placed in the bag. Frogs were then taken back to a central location

nearby for processing. Individuals were implanted subcutaneously with a passive

integrated transponder (PIT) tag and the entry site sealed with medical grade

cyanoacrylate (Vetbond) adhesive (3M, 2016). The PIT tag number, sex, weight, snout–

vent length and capture location for all individuals was recorded before release at their

0

50

100

150

200

250

300

350

400

450

500

Rai

nfa

ll (m

m)

Month

Woolgoolga Rainfall

Rainfall

Mean

17

initial capture location. Sex was determined on the basis of the presence of dark nuptial

pads in males. Surveys took between 2.5 and 5.5 h per night depending on the number

of captured frogs.

All bell frogs captured were handled in coherence with frog hygiene protocols (NPWS,

2003).

3.4 Data analysis

Program MARK was used to analyse the data collected from six nights of nocturnal

surveys. MARK provides parameter estimates from marked animals when they are re-

captured at a later time and tests models of the variables that influence these parameters

(Colorado State University, 2016). These parameters include; apparent survival (phi),

which is the probability of individuals surviving between capture and recapture,

captures (p), the availability of capture, probability of recapture (c), probability of entry

(PENT) the probability of individuals entering into the population for this occasion and

finally abundance (N) which is the total number of animals entering the site during the

sampling period that survive until the next sample time. N is sometimes referred to as

the super population or hypothetical/theoretical population.

The Akaike Information Criterion (AICc) was used to compare models and corrected

for small sample size (Burnham and Anderson 2002). Models were ranked from

smallest to largest AICc value with the top ranked model showing the best fit to the

data.

Only adult male Bell Frog data was used in the analysis.

3.5 Additional Field work

Songmeters were installed at the sampling sites in addition to two meters which were

placed at a nearby artificial dam which was previously identified as habitat and an

adjacent wetland to obtain population estimates and possible identification of new

habitat. Surveying of fish species in the Lake and swamp were also undertaken to

establish the abundance of fish species in the study site that may impact on tadpole

survival. Ephemeral Ponds in the vicinity were also assessed for presence of Green and

Golden Bell Frogs as they have been utilised for breeding there in the past. During the

sampling period no evidence of breeding was detected at any of the ponds. This may be

due to insufficient rainfall required to maintain water in the ponds. Further surveys are

required to establish if GGBF are still using these ephemeral ponds as breeding habitat.

4. Results Overall a total of 133 frogs (70 males, 9 females, 54 sub-adults) were captured on six

occasions. Across the study, 34 frogs were captured on the first occasion, 57 on the

second and 42 on the last. Fifteen sub-adults were not tagged due to their small size

<40mm

18

Figure 4. Capture results for male, female and sub-adult L. aurea over six nights

Overall 133 frogs were captured, however, only the 70 adult males were used for this

analysis.

POPAN design

Analysis with the POPAN design showed that the best-fitting model was that in which

survival (phi) and capture (p) were constant over time and the probability of entry (Pent)

was time varying (Table 1). Model averaging was applied to estimate parameters.

Survival was estimated at 0.69, capture as 0.49, and the probability of entry varied from

0.11to 0.41(Table 2). Abundance was estimated for the six survey occasions at 116

individuals (Table 3).

Table 1. POPAN model

Model AICc Delta AICc AICc

Weight

Model

likelihood

No. par Deviance

{p(.)phi(.)pent(t)} 190.3996 0.0000 0.9991 1.0000 8 -123.0975

{p(t)phi(t)pent(t)} 208.9427 18.5431 0.00009 0.0001 17 -128.8280

{p(.)phi(.)pent(.)} 9921.3953 9730.9957 0.00000 0.0000 4 9617.1282

{p(.)phi(t)pent(t)} 10028.3489 9837.9493 0.00000 0.0000 12 9704.7209

0

5

10

15

20

25

2/11/2015 3/11/2015 11/11/2015 12/11/2015 7/12/2015 8/12/2015

Fro

gs c

aptu

red

Sampling Date

Males

Females

Sub-adults

19

Table 2. Survivorship (phi), capture (p) and probability of entry (PENT) estimates.

Real Function Parameters of {p(.) phi(.) pent(t)} 95% Confidence Interval

Parameter Estimate Standard Error Lower Upper

1:Phi 0.6894977 0.0627640 0.5555613 0.7977639

2:p 0.4901386 0.0768582 0.3447374 0.6372278

3:pent 0.1136285 0.0600647 0.0383060 0.2920777

4:pent 0.3316840 0.0722907 0.2075477 0.4846585

5:pent 0.4105663E-010 0.3938780E-008 -0.7678953E-008 0.7761067E-008

6:pent 0.3196601E-008 0.7849900E-005 -0.1538261E-004 0.1538900E-004

7:pent 0.4110918 0.2848553 0.0692998 0.5502291

8:N 99.166886 12.981581 81.453955 134.85557

Table 3. Population estimate derived from POPAN 6 model.

Gross Population Estimates of {p(.) phi(.) pent(t)} 95% Confidence Interval

Grp. Occ. N*-hat Standard

Error

Lower Upper

1 0 115.93050 15.424874 89.420565 150.29967

5. Discussion

5.1 Population stability

Surveying and continued monitoring of population abundance is important to

comprehend exactly what is being lost and for the design and implementation of

management plans to conserve species throughout a species geographic range. This is

especially important for small and disjunct populations such as the one in Yuraygir

National Park, which may be genetically different and at risk from inbreeding

depression, genetic drift and other environmental conditions (Luquet, et al. 2013;

Goldingay and Newell, 2005).

We sampled a population of Green and Golden Bell Frogs at Yuraygir National Park in

northern NSW to establish if the population has increased, decreased or remained stable

during the 12 years since the last study. This study follows on from surveys conducted

20

by Goldingay and Newell between 1998 and 2004 at the same site. Abundance

estimates by Goldingay and Newell was calculated using the Peterson method at <100

adult male Bell Frogs. This method uses the assumption the population being closed at

the time of sampling and that and that individuals have an equal chance of being

captured. These assumptions may over estimate numbers and should be taken with

caution. For this study abundance was estimated using Program MARK using the

POPAN design and compared the estimated abundance to previous CMR data. Initial

results revealed the population has remained the same as 2005 abundance estimates and

is therefore stable, however, the size of the sampling area during this period was half

that previously surveyed and the number of sampling occasions was substantially less,

with only six survey nights compared to the 31 of Goldingay and Newell in 2005. When

considering these limitations we may confidently say that the population has increased

over the past 12 years, possibly doubling in size.

Sub-adult numbers increased from three (Goldingay and Newell, 2005) to 42. This may

be explained by higher than average rainfall during the previous summer breeding

period. The increase in rainfall decreases the chance of ephemeral ponds, which are

preferred breeding habitat, drying out before metamorphosis of tadpoles. Substantially

less females were tagged, with only nine adult females captured over the six survey

nights. These findings are consistent with previous work, from multiple sites, that

identified an apparent skewed sex ratio in Green and Golden Bell Frog populations

(Goldingay & Newell, 2005).

5.2 Management options

The population of L. aurea at Yuraygir National Park appears to have increased over 12

years. Continued monitoring should be undertaken, as the populations may still be at

risk of future declines and here we present a method that would allow this to occur at

intervals such as once every 5-6 yrs

There is too little information available on life history parameters to ascertain if the

numbers observed can be interpreted as a viable population. Putative suggestions of a

population increase, recommend that monitoring should continue every 5-10years.

Although the sampling method demonstrated here would be adequate to assess further

population fluctuations, this was part of a larger CMR study being conducted and the

extended sampling timeframe used by these researchers would be more a more

representative example of the population.

Unlike most Green and Golden Bell Frog populations, the population in YNP is located

in a relatively undisturbed site which could be used for comparable studies with other

populations. Increases in abundance found here may not be representative of a species

increase in other areas and the success of the YNP population may be used to determine

habitat requirements for L. aurea at other sites.

The likely incidence of Chytrid fungus (Batrachochytrium dendrobatidis) present in the

YNP population is also worth further investigation to determine the impact on survival.

As the site is affected by ocean salt spray future research may focus on findings by

21

Stockwell et al. (2015), which suggest an increase in salinity provides fungicidal

benefits to the species.

One approach to increase breeding success at the site would be the installation of

artificial ponds adjacent to the study sites which may overcome future decreases in

breeding success when ephemeral ponds do not retain sufficient water during dry

periods, which are expected to increase with the impacts of climate change.

22

References

3M. (2016). 3M™ Vetbond™ Tissue Adhesive. Retrieved from

http://solutions.3m.com/wps/portal/3M/en_US/AnimalCareNA/Home/Product

Catalog/~/3M-Vetbond-Tissue-Adhesive?N=7578309+3294397973&rt=rud

Australian Government Department of Environment and Heritage (2006). Threat

abatement plan: infection of amphibians with chytrid fungus resulting in

chytridiomycosis. Canberra: Department of Environment and Heritage.

Australian National Parks. (2016). Yuraygir National Park. Retrieved from

http://www.australiannationalparks.com/newsouthwales/Yuraygir/default.htm

Barinaga, M. (1990). Where have all the froggies gone? Science, 247, 1033-1034.

Belden, L.K., and Blaustein, A.R. (2002). Exposure of red-legged frog embryos to UV-

B radiation in the field negatively affects larval growth and development.

Population Ecology, 130, 551-554.

Blaustein, A. R., Han, B.A., Relyea, R.A., Johnson, P.T.J., Buck, J.C., Gervasi, S.S., &

Kats, L.B. (2011). The complexity of amphibian population declines:

understanding the role of cofactors in driving amphibian losses. Annals of the

New York Academy of Sciences 1223, 108–119.

Bleach, I.T., Beckmann, C., Both, C., Brown, G.P., & Shine, R. (2015). Noisy

neighbours at the frog pond: effects of invasive cane toads on the calling

behaviour of native Australian frogs. Behavioural Ecology Sociobiology, 69,

675–683

Bureau of Meteorology. (2016). Woolgoolga climate data. Retrieved from http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=136&p_

display_type=dailyDataFile&p_startYear=&p_c=&p_stn_num=059039

Burns, E.L., Eldridge, M.D., and Houlden, B.A. (2004). Microsatellite variation and

population structure in a declining Australian Hylid L. aurea. Molecular

Ecology, 13, 1745–1757.

Clancy, G.P. (1996). The Green and Golden Bell Frog L. aurea in the Station Creek

area of Yuraygir National Park. Australian Zoologist, 30 (2), 214-217.

Colorado State University. (2016). Program MARK. Downloaded from http://program-

mark.sharewarejunction.com/

Department of the Environment. (2012). Disease Strategy Chytridiomycosis (Infection

with Batrachochytrium dendrobatidis) Version 1. Retrieved from

http://www.environment.gov.au/system/files/resources/387d3e66-3cdc-4676-

8fed-759328277da4/files/chytrid-fungus-manual.pdf

23

Eisemberg, C. C., & Bertoluci, J. (2016). Fluctuating asymmetry in populations of the South

American frog Physalaemus cuvieri (Leptodactylidae) in areas with different degrees

of disturbance. Journal of Natural History, 1-9.

Environmental Protection & Biodiversity Conservation Act (1999). Retrieved from

www.environment.gov.au/topics/about-us/legislation/ environment-protection-

and-biodiversity-conservation-act-1999.

Frankham, R. (2015). Genetic rescue of small inbred populations: metaanalysis reveals

large and consistent benefits of gene flow. Molecular Ecology 24, 2610–2618

Frogs of Victoria. (2015). L. aurea: Green and Golden Bell Frog. Retrieved from

http://frogs.org.au/frogs/fov.php?frog_id=1

Gillespie, G.R., Scroggie, M.P., Roberts, J.D., Cogger, H.G., Mahoney, M.J., and

McDonald, K.R. (2011). The influence of uncertainty on conservation

assessments: Australian frogs as a case study. Biological Conservation, 144

(5), 1516-1525.

Goldingay, R. (2008). Conservation of the endangered Green and Golden Bell Frog:

what contribution has ecological research made since 1996? Australian

Zoologist, 34 (3).

Goldingay, R., & Lewis, B. (1999). Development of a conservation strategy for the

green and golden bell frog in the Illawarra Region of NSW. Australian

Zoologist, 31, 376-87.

Goldingay, R.L., and Newell, D.A. (2005). Aspects of the population ecology of the

Green and Golden Bell Frog L. aurea at the northern end of its range.

Australian Zoologist, 33 (1), 49-59.

Hamer, A.J., Makings, J.A., Lane, S.J. and Mahony, M.J. (2004). Amphibian decline

and fertilizers used on agricultural land in south-eastern Australia. Agriculture

Ecosystems & Environment 102: 299-305.

Hartigan, A., Fiala, I., Dykova, I., Jirku, M., Okimoto, B., Rose, K., Phalen, D., &

Slapeta, J. (2011) A Suspected Parasite Spill-Back of Two Novel Myxidium

spp. (Myxosporea) Causing Disease in Australian Endemic Frogs Found in the

Invasive Cane Toad. PLoS ONE 6(4): e18871.

doi:10.1371/journal.pone.0018871

Hero, J., Morrison, C., Gillespie, G., Roberts, J.D., Newell, D., Meyer, E., McDonald, K.,

Lemckert, F., Mahony, M., Osborne, W., Hines, H., Richards, S., Hoskini, C., Clarke,

J., Doaki, N., & Shoo, L. (2006). Overview of the conservation status of Australian

frogs. Pacific Conservation Biology, 12(4), 313 -320.

Kearney, B.D., Byrne, P.G., and Reinal, R.D. (2012). Larval Tolerance to Salinity in

Three Species of Australian Anuran: An Indication of Saline Specialisation in

L. aurea. PLoS ONE, 7 (8), 1-7.

24

Kriger, K.M., Pereoglou, F., and Hero, J. (2007). Latitudinal variation in the prevalence

and intensity of Chytrid (Batrachochytrium dendrobatidis) infection in eastern

Australia. Conservation Biology, 21 (5), 1280-1290.

Lewis, B. D., & Goldingay, R. L. (2005). Population monitoring of the vulnerable

wallum sedge frog (Litoria olongburensis) in north-eastern New South

Wales. Australian Journal of Zoology, 53(3), 185-194.

Lewis, B. and Goldingay, R. (1999). Preliminary assessment of the status of the green

and golden bell frog in north-eastern New South Wales. Pp. 94-98 in Declines

and Disappearances of Australian Frogs. Ed. by A. Campbell. Environment

Australia, Canberra.

Luquet, E., Lena, J. P., David, P., Prunier, J., Joly, P., Lengagne, T., & Plénet, S.

(2013). Within-and among-population impact of genetic erosion on adult

fitness-related traits in the European tree frog Hyla arborea. Heredity, 110(4),

347-354.

National Parks and Wildlife Service. (2003). Environmental Impact Assessment

Guidelines: Green and Golden Bell Frog (L. aurea). Retrieved from

http://www.environment.nsw.gov.au/resources/nature/GAndGbellfrogEia0703.

pdf

National Parks and Wildlife Service. (2016). Yuraygir National Park. Retrieved from

http://www.nationalparks.nsw.gov.au/visit-a-park/parks/Yuraygir-National-

Park

Neckel-Oliveira, S., Galatti, U., Faveri, S. B., Albareli, L. P., & Nascimento, H. E.

(2013). Ecological correlates in Brazilian Amazonian anurans: implications for

conservation. Amphibia-Reptilia, 34(2), 217-232.

Newell DA, Goldingay RL, Brooks LO (2013) Population Recovery following Decline

in an Endangered Stream-Breeding Frog (Mixophyes fleayi) from Subtropical

Australia. PLoS ONE 8(3): e58559. doi:10.1371/journal.pone.0058559

Office of Environment and Heritage. (2016). Threats to Wetlands. Retrieved from

http://www.environment.nsw.gov.au/wetlands/ThreatsToWetlands.htm

Pizzatto, L., Stockwell, M., Clulow, S., Clulow, J. & Mahoney, M. (2016). Finding a

place to live: conspecific attraction affects habitat selection in juvenile green

and golden bell frogs. Acta Ethologica, 19, 1–8.

Polo-Cavia, N., Burraco, P., & Gomez-Mestre, I. (2016). Low levels of chemical

anthropogenic pollution may threaten amphibians by impairing predator

recognition. Aquatic Toxicology, 172, 30-35.

Pyke, G. H. and Osborne, W. S. (eds) 1999. The Green and Golden Bell Frog L. aurea:

Biology and Conservation. Australian Zoologist 30(2), 130-258.

25

Pyke, G.H., and White, A.W. (2001). A review of the biology of the Green and Golden

Bell Frog L. aurea. Australian Zoologist, 31 (4), 563-598.

Pyke, G.H. and White, A.W. (1996). Habitat requirements for the Green and Golden

Bell Frog L. aurea (Anura: Hylidae). Australian Zoologist, 30 (2), 224-232.

Rollins-Smith, L.A., Ramsey, J.P., Pask, J.D., Reinert, L.K., Woodhams, D.C. (2011).

Amphibian immune defenses against chytridiomycosis: impacts of changing

environments. Integ Comp Biol, 1-11.

Skerratt, L.F., Berger, L., Speare, R., Cashins, S., McDonald, K.R., Phillott, A.D.,

Hines, H.B., and Kenyon, N. (2007) Spread of chytridiomycosis has caused the

rapid global decline and extinction of frogs. EcoHealth, 4, 125–134.

Stockwell, M.P., Clulow, J., and Mahony, M.J. (2015). Evidence of a salt refuge:

chytrid infection loads are suppressed in hosts exposed to salt. Oecologia, 177,

901-910.

Stuart, S.N., Chanson, J.S., Cox, N.A., Young, B.E., Rodrigues, A.S.L., Fischman, D.L

and Waller, R.W. (2004). Status and Trends of Amphibian Declines and

Extinctions Worldwide. Science, 306, 1783-1786.

Threatened Species Conservation Act. (1995). Retrieved from

http://www.environment.nsw.gov.au/threatenedspecies.

Threlfall, C., Jolley, D. F., Evershed, N., Goldingay, R. & Buttemer, W. A. (2008). Do

Green and Golden Bell Frogs L. aurea occupy habitats with fungicidal

properties? Australian Zoologist, 34 (3), 350-360.

Tinto, R. (2015). Specialist amphibian report for Red List frog species and mitigation

recommendations for Richard’s Bay Minerals: Zulti South Mining Lease Area.

Cell, 83(254), 9563.

Van de Mortel, T & Goldingay, R. (1998). Population assessment of the endangered

Green and golden bell frog at Port Kembla, New South Wales. Australian

Zoologist, 31, 48-54.

White, A.W. (1995). Disappearing Frogs. Australian Zoologist, 30 (1), 48-56.

White, A.W. (1995). The Green and Golden Bell Frog. Frog Facts 5, 1-4.

White, A.W., and Pyke, G.H. (2015). Vegetation mounds as over-winter Habitat for

Green and Golden Bell frogs Litoria aurea. Australian Zoologist, 37(4), 510-

516.

White, A.W. and Pyke, G.H. (2008). Green and Golden Bell Frogs in New South

Wales: current status and future prospects. Australian Zoologist, 34(3), 319-

333.

26

White, A. W. and Pyke, G. H. (1996). Distribution and conservation status of the Green

and Golden Bell Frog L. aurea in New South Wales. Australian

Zoologist 30(2) 177-189.

Wildlife Acoustics. (2016). Wildlife acoustics: Bioacoustic Monitoring Systems.

Retrieved from http://www.wildlifeacoustics.com/

Williams, B.K., Nichols, J.D., and Conroy, M.J. (2001). Analysis and Management of

Animal Populations. San Diego, CA: Academic Press.

27

Appendices

Appendix 1.

Figure 5. Colourmorphs of Yuraygir. Photos: D. Newell & R. Goldingay.

Appendix 2.

Figure 6. Male L. aurea on M. quinquinervia tree. Photo: R. Goldingay.

28

Estimates of Derived Parameters

Gross Birth+Immigration Estimates of {p(.) phi(.) pent(t)}

95% Confidence Interval

Grp. Occ. B*-hat Standard Error Lower Upper

---- ---- -------------- -------------- -------------- --------------

1 1 13.492395 7.2457751 5.0303326 36.189400

1 2 39.384596 9.0126917 25.293901 61.324916

1 3 0.4875118E-008 0.4677067E-006 0.1307099E-010 0.1818285E-005

1 4 0.3795686E-006 0.9321208E-003 0.1644067E-009 0.8763165E-003

1 5 48.813578 11.895892 30.484798 78.162415

Net Birth+Immigration Estimates of {p(.) phi(.) pent(t)}

95% Confidence Interval

Grp. Occ. B-hat Standard Error Lower Upper

---- ---- -------------- -------------- -------------- --------------

1 1 11.268183 6.0257856 4.2165719 30.112603

1 2 32.892074 7.1582635 21.576489 50.142010

1 3 0.4071458E-008 0.3906056E-006 0.1091624E-010 0.1518542E-005

1 4 0.3169970E-006 0.7784614E-003 0.1373044E-009 0.7318564E-003

1 5 40.766695 10.075962 25.294626 65.702631

Population Estimates of {p(.) phi(.) pent(t)}

95% Confidence Interval

Grp. Occ. N-hat Standard Error Lower Upper

---- ---- -------------- -------------- -------------- --------------

1 1 14.239934 5.6518841 6.7287546 30.135698

1 2 21.086584 6.2868991 11.901510 37.360304

1 3 47.431224 7.0001976 35.572345 63.243539

1 4 32.703717 6.0395225 22.841026 46.825091

1 5 22.549137 5.6597709 13.890939 36.603974

1 6 56.314272 11.882475 37.407743 84.776493

Gross Population Estimates of {p(.) phi(.) pent(t)}

95% Confidence Interval

Grp. Occ. N*-hat Standard Error Lower Upper

---- ---- -------------- -------------- -------------- --------------

29

1 0 115.93050 15.424874 89.420565 150.29967