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i

Statement of Originality

To the best of my knowledge, the following material has not been published or written by

another person except where due credit is given. This thesis has not been previously submitted

for a degree or diploma in another academic institution.

__________________________

Tamara Osborne

I, as supervisor of the above student, declare this thesis to be the original production of the

aforementioned student. I hereby note my assistance in the preparation of this thesis through

editorial comments.

__________________________

Dr. C. G. Morley

Principle Supervisor

Biology Division

ii

Acknowledgements

This thesis has only come about due to the invaluable assistance of many people. Firstly, to my

sponsors in the initial years – NZAID and USP, I am truly grateful for the opportunity to

undertake this project. To the administrative staff of the Biology division, the staff of the

Personnel and Finance section, and the staff of the Bursary, I extend my apologies for the

constant requests. To my peers who generously volunteered their free time to help out in the

field: Nunia Thomas, Joape Kuruyawa, Isaac Rounds, Jone Nuikula, Taina Mulo, Patrick

Pikacha and Vitali Wocjick – you are all true friends to have waded through mud and stream for

as long as you all did. Also, to Sunil Prasad for his company in the Biology post-graduate

computer lab and his ever-useful tips. I am incredibly grateful to my co-supervisors, Dr. Craig

Morley and Dr. Clare Morrison, for their advice on sampling design and logistics. Dr. Morrison

and Dr. Tim Markwell read through and provided helpful comments on draft manuscripts. Many

thanks to Dr. Linton Winder for taking time out of his busy schedule to look at my data and

statistical analysis. I am also deeply indebted to Conway Pene, GIS Lecturer in the School of

Geography, without whom I would not have been able to map my transect. To the staff of the

Colo-i-Suva forestry station, the PWD gate-keepers to the Savura Valley road, and to the staff of

the Fiji Meteorological Station at Laucala Bay, my gratitude for granting me access to the

reserves and rainfall data respectively. A heartfelt ‘vinaka vaka levu’ to the wonderfully stoic

members of my sampling team that stayed with me through so many late, often wet, and

occasionally cold nights; to Timoci Koliyavu and Alivereti Naikatini, especially to Qase for

being the person you are. Finally, this thesis is dedicated to my family, for their emotional

support, words of encouragement, and, due to the realities of being a fiscally challenged student,

for the occasional monetary aid.

Contents

iii

Statement of Originality i

Acknowledgements ii

Contents iii

List of Figures vi

List of Tables viii

List of Appendices ix

Abstract x

Chapter 1 General Introduction 1

1.1 INTRODUCTION 1

1.2 THE ANURANS OF FIJI 3

1.2.1 Platymantis in the Pacific 3 1.2.2 The Fiji Ground Frog, Platymantis vitianus 4 1.2.3 The Fiji Tree Frog, Platymantis vitiensis 6

1.3 FROG SURVEYS IN THE FIJI ISLANDS 10

1.3.1 Environmental Factors that Influence Frog Distribution 10

1.4 SUMMARY OF STUDY 13

1.4.1 Aims and Objectives 13

Chapter 2 Major habitat preferences of the Fiji tree frog in the Savura area 15

2.1 INTRODUCTION 15

2.2 METHODS 17

2.2.1 Study site 17 2.2.2 Habitat Surveys 17 2.2.3 Data Analysis 18

2.3 RESULTS 19

2.3.1 Results of the Habitat Surveys 19 2.3.2 Weather Data and Analysis 24

Contents continued

iv

2.4 DISCUSSION 28

2.4.1 Habitat Selection 28 2.4.2 Influence of Weather on Survey Results 29

2.5 SUMMARY 30

Chapter 3 Microhabitat selection of Platymantis vitiensis within the Savura area 31

3.1 INTRODUCTION 31

3.2 METHODS 32

3.2.1 Data Collection: Permanent Transect Surveys 32 3.2.2 Microhabitats Occupied in Different Habitats 33 3.2.3 Data Collation 34 3.2.4 Data Analysis 34

3.3 RESULTS 34

3.3.1 Microhabitat Selection along the Transects 343.3.2 Microhabitat Selection within the Three Major Habitats 40 3.3.3 Comparison between Frog Activity along the Stream and Land Transects 40

3.4 DISCUSSION 46

3.5 SUMMARY 48

Chapter 4 Phenology of Platymantis vitiensis along Vago Creek over a one-year period 50

4.1 INTRODUCTION 50

4.2 METHODS 51

4.2.1 Study Site 51 4.2.2 Data from Site and Captured Individuals 52 4.2.3 Data Analysis 55

4.3 RESULTS 56

4.3.1 Phenology of the Fiji tree frog population along Vago Creek 56 4.3.2 Influence of Weather Factors: Rainfall and Temperature 57 4.3.3 Phenology of Fiji Tree Frogs from the Habitat Surveys 58

4.4 DISCUSSION 68

Contents continued

v

4.5 SUMMARY 69

Chapter 5 Conclusions and Recommendations for Future Research 70

5.1 THE SAVURA TREE FROG POPULATION 70

5.1.1 Major Habitat Preferences 70 5.1.2 Microhabitat Selection 71 5.1.3 Phenological Information 72

5.2 RECCOMENDATIONS FOR FUTURE SURVEYS 72

5.2.1 Temporal Variables 73 5.2.2 Spatial Variables 74 5.2.3 Other Factors to Consider 76

5.3 IMPLICATIONS FOR CONSERVATION OF FROGS IN FIJI 77

5.4 SUMMARY 79 Chapter 1

Bibliography 80

Appendices 92

Appendix 1: Original Data from Habitat Surveys 92

Appendix 2: Plant Substrate List 94

Appendix 3: Rainfall Variabilitity in Suva from 2000-2005 96

List of Figures

vi

Figure Legend Page

Figure 1.1 The distribution of the Fiji tree frog (Platymantis vitiensis) throughout the Fiji

archipelago. 2

Figure 1.2 Distribution of Platymantids in South-east Asia and across the Pacific Ocean. 5

Figure 1.3 An adult female Fiji tree frog, Platymantis vitiensis, perched on branches of

riparian shrub, Syzygium seemannii. 8

Figure 1.4 Male Fiji tree frog with uniform pale yellow-green colour, yellow groin flash

and pimply dorsal surface. 9

Figure 1.5 Map of the study site showing general features such as roads, drainage, reserve

boundaries, and pylon lines. 14

Figure 2.1 Map of the study site showing the locations of habitat sites surveyed between June

2004 and May 2005. 20

Figure 2.2 Frog abundance at twelve sites within the three different habitat types and mean

number per habitat type. 22

Figure 2.3 Temporal variation of tree frog abundance in each of the three habitat types from

June 2004 to May 2005. 23

Figure 2.4 The strong relationship relationship between air and stream temperatures recorded

during the habitat surveys. 26

Figure 2.5 The relationship between rainfall and the log-transformed frog abundance in the

three habitats. 27

Figure 3.1 Substrate of perch sites occupied by tree frogs along the two transects on Vago

Creek, Savura. 36

Figure 3.2 Number of tree frogs encountered at different perch heights along both fixed

transects, Vago Creek, Savura. 37

Figure 3.3 The distances of captured tree frogs from the stream transect along Vago Creek. 38

Figure 3.4 Vegetation utilised by tree frogs as perch sites along streams in the three major

habitats. 41

Figure 3.5 Total numbers of tree frogs encountered at different perch heights in three different

habitats types in the Savura area. 42

List of Figures

vii

Figure 3.6 Estimated distances of tree frogs (to nearby streams) captured in three different

habitats in the Savura area. 43

Figure 3.7 Abundance of Fiji tree frogs encountered along the land compared to the stream

transect. 45

Figure 4.1 Schematic diagram depicting the layout of the permanent parallel land and stream

transect along a mid-highland section of Vago Creek, Savura. 53

Figure 4.2 The abundances of the age classes from the fixed transects over the 12-month

period, graphed against average rainfall and air temperatures on the sampling

nights. 59

Figure 4.3 Abundance of gravid females captured along the both land and stream transects

over the 12-month survey period, graphed against average rainfall. 60

Figure 4.4 The significant correlation between log-transformed abundances of adult

P. vitiensis graphed against average rainfall of sampling nights in each month. 61

Figure 4.5 The significant correlation between log-transformed average rainfall and log-

transformed abundances of metamorph Fiji tree frogs. 62

Figure 4.6 The significant correlation between average temperatures and log-transformed

abundances of gravid female tree frogs. 63

Figure 4.7 The significant correlation between log-transformed average rainfall and log-

transformed abundances of adult Fiji tree frogs from the habitat study. 64

Figure 4.8 Abundance of adult Fiji tree frogs captured in the habitat study over the 12-month

survey period, graphed against average rainfall of the sampling days. 65

List of Tables

viii

Table Legend Page

Table 2.1 Descriptive statistics for habitat surveys: standard deviation, variance and standard

error of the mean. 21

Table 2.2 Weather data recorded per month for the habitat surveys in Savura. 25

Table 3.1 Results of univariate ANOVAs on microhabitat data from transects. 39

Table 3.2 Results of two-way ANOVAs on microhabitat data from the habitat surveys. 44

Table 4.1 Field classification system for identifying age/size of captured frogs. 54

Table 4.2 Toe-clipping codes for identifying recaptured frogs. 54

List of Tables

ix

Appendix Legend Page

Appendix 1.1 Map co-ordinates for sampling sites in habitat surveys. 94

Appendix 2.1 Plant species used as substrates by captured frogs. 96

Appendix 3.1 Monthly rainfall variability in Suva over the last five years. 98

Abstract

x

Macro-habitat and microhabitat preferences of the Fiji tree frog, Platymantis vitiensis, were

investigated in the Savura population near Suva, Viti Levu, Fiji. Twelve sites in three habitat

types (primary lowland rainforest, disturbed secondary lowland rainforest, and mahogany

plantations) were surveyed over a twelve-month period. In addition, phenology of the tree frog

was investigated along two permanent transects along Vago Creek, Savura.

Fiji tree frogs were more common in primary lowland rainforest sites than mahogany plantations

and disturbed secondary lowland rainforest sites. The frogs are found more often along stream

sides with Pandanus present, in relatively undisturbed rainforest. Frogs were more common

along streams in the Colo-i-Suva mahogany reserve than the secondary forests and shrub land of

the Vago and Savura reserves. The difference in frog abundance in these habitats is possibly due

to human disturbance, although this was not examined.

Tree frogs selected perch sites based on their height above ground, proximity within open

riparian habitat strips, and the plant substrate’s features. Individuals were commonly found on

Pandanus leaves and fern fronds, as well as the broad-leaved Dilenia. They were often captured

close to the stream on riparian vegetation. The tree frogs were generally found one to two metres

above the ground, and cohorts were observed in different microhabitats.

The phenology of the Vago Creek frog population may be complicated by the inter-annual

fluctuations in rainfall, and other factors such as migration and recruitment. The activity of adult

frogs was significantly negatively influenced by rainfall; however gravid female abundance was

significantly more correlated with changes in air temperature over the year than rainfall. Gravid

females were more active during the wet season and egg-laying primarily occurred during the

months of November to February. Juvenile tree frog phenology contrasts with metamorph

Abstract

xi

activity, as metamorphs were captured more often during the dry season, whereas juvenile

activity peaked early in the wet season. Rainfall was the most important weather variable

influencing Fiji tree frog activity during the 12-month survey period, as indicated by independent

tests of the broad-scale survey data.

Although, Platymantis vitiensis populations in Savura were more abundant in primary lowland

rainforest future surveys should also include secondary vegetation. Time-restricted surveys may

be more effective by sub-sampling along riparian strips in primary forested areas, as tree frogs

showed a strong affinity for stream-side perch sites. Future inventorying and monitoring of Fiji

tree frog populations should be carried out when abundance is highest between late wet season,

to early dry season (March to July).

1

Chapter 1 General Introduction

1.1 INTRODUCTION

The Fiji tree frog, Platymantis vitiensis, is one of two endemic ranid species found in the Fiji

Island archipelago, the other being the Fiji Ground Frog, Platymantis vitianus (Ryan, 2000). The

tree frog’s range is thought to have been more extensive throughout the western and central parts

of the Fiji group before human arrival (Watson, 1960; Gorham, 1968; Pernetta and Goldman,

1977), but its distribution is now restricted to the four of the largest islands (Morrison, 2003):

Viti Levu, Vanua Levu, Taveuni, and Ovalau (Figure 1.1).

Although the Fiji tree frog is not considered endangered, further destruction of its forest habitat

due to increasing urban expansion may cause the small isolated populations on Viti Levu to

decline into extinction vortices. Ryan (1984) previously voiced this concern saying, that if

rainforest continues to be logged and secondary rainforest is continually disturbed by human

activity, the tree frog should be considered at risk. Therefore, it is important that the ecology and

population dynamics of the Fiji tree frog are better understood in order to predict how further

habitat degradation and fragmentation will affect this species.

Many anurans show habitat preferences based on forest canopy cover (Gregory, 1983; Brown

and Rose, 1988; Ovaska, 1991). To date it is believed that Fiji tree frogs are strongly associated

with riparian strips in good rainforest (Gorham, 1971; Pernetta and Watling, 1978; Watling and

Zug, 1998; Morrison, 2003). Within the rainforest habitat, frogs tend to exhibit microhabitat

preferences (Stewart and Pough, 1983; Stewart, 1985; Townsend, 1989). Previous work on Fiji

tree frogs has indicated an affinity for certain plant species as diurnal retreat sites (Gorham,

1971; Morrison, 2003), in particular the riparian pandanus (Pandanus sp.).

2

N

Viti Levu

Vanua Levu

4 7

6

10

11

1413

16 15

12

16 Sº

18 Sº

178 Sº 180 Sº 182 Sº

182 Sº

180 Sº

178 Sº

16 Sº

18 Sº

178 Sº

0 50km

1 2 3

5

9 8

17

Figure 1.1 The known distribution of the Fiji tree frog (Platymantis vitiensis) throughout the

Fiji archipelago. Locations as shown on map are: 1. Nadarivatu 2. Tomaniivi 3.

Nasoqo 4. Monasavu 5. Wabu 6. Sovi 7. Wailatoa 8. Savura 9. Colo-i-Suva

10. Ovalau Island 11. Koro Island 12. Waisali 13. Labasa 14. Navonu

15. Somosomo 16. Bouma 17. Salialevu (Sources: Morrison, 2003; Kuruyawa et

al., 2004; Naikatini et al., In Prep.).

3

One of the most important aspects of the population dynamics of anurans is their phenology or

activity pattern over a year. There has been much work on the phenology of amphibians around

the world (Church, 1961; Caetano and Leclair, 1999), mostly on anurans (Aichinger, 1987;

Crump and Pounds, 1989; Ritke and Gabb, 1991), especially the effect of environmental

variables on anuran phenology (Brown and Rose, 1988; Bridges and Dorgas, 2000; O’Reilly and

Hines, 2002; Oseen and Wassersug, 2002). Although the Fiji tree frog’s ecology is often

described as being correlated with the wet and dry season of the Fiji group (Gorham, 1968;

Ryan, 1984; Morrison, 2003), there has never been a long term survey that investigates changes

in frog activity and the influence of environmental factors such as rainfall and temperature on

either of Fiji’s native frog species.

1.2 THE ANURANS OF FIJI

1.2.1 Platymantis in the Pacific

The genus Platymantis currently consists of 53 described species ranging from the Philippines in

the west, Palau in the north and Fiji to the east. Although the diversity of Philippine species

suggests a Southeast Asian source for Platymantis, there is a possibility that northern and eastern

congeners may have dispersed from the Bismarck Archipelago (Ota and Matsui, 1995). There

are 26 species in Southeast Asia, one in Palau, and 24 in the Papua New Guinea and Solomon

Islands (Kuramoto, 1997; Allison and Kraus, 2001). The two Fiji platymantids represent the

eastern-most limit of the genus’ range (Figure 1.2).

Recent genetic analysis points to a common ancestor for the Fiji frogs, which may have

originated from the Solomon Islands (Brown pers. comm., 2005). Little is known about how this

ancestor got to the Fiji group, although several theories have been suggested (Gorham, 1971;

4

Pernetta and Goldman, 1977; Pernetta and Watling, 1978; Ryan, 1984; Allison, 1996). The two

most pervasive hypotheses are that the founding population of this ancestor either rafted to Fiji

on floating vegetation, or was brought to Fiji as a food item for humans. It may be possible that

the extinct giant ranid fossil found by archaeologists (Worthy, 2001) was the ancestral form of

the extant Fiji platymantids, as several features of its skeleton are similar to features of one or the

other extant forms.

1.2.2 The Fiji Ground Frog, Platymantis vitianus

The Fiji ground frog is listed as endangered under the IUCN classification system (IUCN, 2003),

based on the extent of the loss of its primary forest habitat. The museum record suggests that the

ground frog was once present on the largest island in the Fiji group, Viti Levu (Gorham, 1968).

The species is now reported from the islands of Vanua Levu, Taveuni, Gau, Ovalau, and Viwa

(Morrison, 2003). Viwa Island is the smallest of the ground frog’s island refugia, being only 60

ha in size (Ryan, 1985). The ground frog is thought to have been extirpated from Viti Levu by

introduced predators (small Indian mongoose Herpestes javanicus and rats Rattus spp.),

competitors (cane toads Bufo marinus) and the human-induced modification of its forest habitat.

It is thought that ground frogs lay eggs year-round (Morrison pers. comm., 2003) like other

tropical species (Beebee, 1996), with increased breeding activity occurring during the wetter

months of the year (November-April). Both sexes call and it is has been suggested that the

female advertises for the male frog (Ryan, 2000), however advertisement by the male is still a

possibility (Bishop, pers. comm., 2005). The ground frog is a terrestrial breeder with direct

development in the large yolky eggs, which are laid in low-lying locations (Ryan, 2000).

5

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re 1

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6

1.2.3 The Fiji Tree Frog, Platymantis vitiensis

More is known about the ecology and reproductive biology of the Fiji tree frog than the ground

frog (Gorham, 1971; Gibbons and Guinea, 1983; Ryan, 1984; Morrison, 2003). Tree frogs tend

to be smaller than their ground frog relatives, as females grow to snout-urostyle lengths (SUL) of

47-60 mm, males grow to 32-45 mm, and hatchlings (metamorphs) range between 9-11 mm

(Gorham, 1971; Ryan, 1984; Morrison, 2003). Body weight is proportional to length, with

females reaching weights of ten grams (Ryan, 1984).

Finger discs tend to be larger than toe discs (a distinguishing character between the Fiji

Platymantis species), with the third finger disc being roughly equal in size to the individual’s eye

(Morrison, 2003). Tree frogs are extremely variable in colour, ranging from dark brown-green,

yellow-green, and reddish or bright orange, often with markings such as a medial dorsal cream

stripe or darker stippling. Ryan (1984) identified 22 common colour morphs and 17 rare colour

patterns however, this may be an underestimate. Figures 1.3 and 1.4 show different colour

morphs of male and female tree frogs captured along the Vago Creek study site. In contrast to

the dorsal colouration the ventral surface is less variable in colour and patterning, and is

generally pale yellow-green.

Tree frogs have been found in lowland and highland rainforest, as well as in disturbed habitats

such as plantations (Gorham, 1968; Morrison, 2003). There appears to be a close association

with Pandanus plants (Gorham, 1971; Gibbons and Guinea, 1983; Ryan, 1984; Pernetta and

Goldman, 1977). The frogs can often be found sheltering during the day in the moist leaf litter

that collects between the base of the Pandanus leaves and the plant stem. At night these frogs

climb out onto the leaf surface to catch insects. Other plants in which they have been found at

7

night are on banana (Musa spp.) leaves, on Syzygium saplings, in birds’ nest ferns (Asplenium

nidus), epiphytic ferns, and on streamside vegetation such as ground ferns and Acalypha

rivularis (Gorham, 1968; Ryan, 1984; Morrison, 2003).

Tree frogs are capable of breeding year round but are more reproductively active between

December and March, with a peak in breeding activity occurring in late February to early March

(Gibbons and Guinea, 1983; Ryan, 1984; Morrison, 2003). Eggs are laid at the base of leaves of

Pandanus, lilies and ferns (Morrison, 2003), which tend to retain moisture in their axils for a

relatively longer period of time than other plants in Fiji’s lowland rainforest (Gorham, 1971).

Breeding studies conducted in Wailoku by Gibbons and Guinea (1983), noted an average clutch

height of 0.6 m above ground, and that all clutches found were located close to a small stream.

Clutches are relatively small (30-40 eggs) as the eggs are quite large (7-9 mm wide) to sustain

direct development within the egg (Ryan, 1984). Hatchlings emerge after 4-5 weeks (Gibbons

and Guinea, 1983; Morrison, 2003).

Although it was once thought that only females call (Ryan, 1987), recent work confirms that

both males and females are capable of calling (Boistel and Sueur, 1997). The call is likened to

the sound of a 'dripping tap', and is generally heard more frequently during the breeding season

(Morrison, pers. comm., 2004). Other behavioural traits include evasive jumping, good

swimming ability, and darkening during the day (to blend into the leaf litter). These

characteristics have enabled tree frog populations to persist on islands in the Fiji group where

predators such as mongoose, rats and cats (Felis catus) have been introduced. The reduction of

the overall range of the Fiji tree frog has been attributed to predation by these predators and

habitat fragmentation (Ryan, 1984; Morrison, 2003).

8

Figure 1.3 An adult female Fiji tree frog, Platymantis vitiensis, perched on branches of

riparian shrub, Syzygium seemannii.

9

Figure 1.4 Male Fiji tree frog with uniform pale yellow-green colour, yellow groin flash and

pimply dorsal surface.

10

1.3 FROG SURVEYS IN THE FIJI ISLANDS

The literature concerning tree frog ecology and reproductive phenology is generally anecdotal

with only Gorham's (1968) fieldwork providing some baseline data. No published studies have

systematically recorded abundance and activity patterns in any of the extant Fiji tree frog

populations.

Therefore, an objective of my research is to identify more effective sampling techniques when

surveying tree frogs (as well as the ground frog), particularly when limited by time and finances.

By comparing tree frog populations in three types of habitats, more can be learnt about the types

of microhabitats (retreat sites and forage sites) tree frogs inhabit. This information, in

combination with data on the influence of environmental variables, is essential for the design of

effective surveying and monitoring protocols for anurans (Koch, 2000).

The tree frog’s persistence on mainland Viti Levu has been attributed to its arboreal niche and

evasive behaviour (Ryan, 1984). Previous surveys of tree frogs on Viti Levu have reported

populations in the Wailoku area, Colo-i-Suva, Nasoqo, Tomaniivi, Nadarivatu, Monasavu, Sovi

(Gorham, 1971; Ryan, 1984; Morrison, 2003). More recently, fieldwork in the eastern district of

Viti Levu has reported a small population near Wailotua in the Tailevu province of Viti Levu

Island (Naikatini, Osborne and Morley, In prep.), and a good-sized population in the Waisali

Reserve on Vanua Levu (Morrison et al., 2004).

1.3.1 Environmental Factors that Influence Frog Distribution

It has been shown by several studies (Church, 1961; Heatwole, 1962; Blankenhorn, 1972;

Aichinger, 1987; Brown and Rose, 1988; Fukuyama and Kusano, 1992; Lizana, Marquez and

11

Martin-Sanchez, 1994; Beebee, 1995; Marsh, 2000; Parris, 2004) that environmental conditions

affect amphibian activity. Environmental effects are significant parameters in sampling designs

and need to be better understood when surveying tree frogs with the most important

environmental factors being rainfall/precipitation, air temperature, water temperature, relative

humidity, and the percentage of cloud cover.

Most anurans are active when there is a sufficient amount of moisture in their habitat (Cree,

1989; Marsh, 2000). Rainfall history prior to a survey and the intensity of rainfall events

immediately before and during a survey tend to have differing effects on the activity of an anuran

community. Rainfall is a highly influential variable on breeding activity, particularly in

temperate countries (Gascon, 1991; Marsh, 2000). Fiji is a tropical country however rainfall

varies in distribution and abundance over the year. It has been suggested that the breeding

activity of Fiji’s frogs is correlated with rainfall variability over the year (Kuruyawa et al., 2004).

Air temperature is another factor determining anuran nightly activity, especially when

temperatures are quite low or high (Brattstrom, 1963; Sinsch, 1984). The influence of

temperature on breeding activity has mostly been demonstrated for temperate (Fukuyama and

Kusano, 1992; Reading, 1998) and subtropical anurans (Kam and Chen, 2000), as annual

temperatures vary markedly in these regions. Temperature is likely to have an effect on the

direct development of the Fiji tree frog. The length of the embryonic development period of

Eleutherodactylus coqui, a south-American terrestrial leptodactylid, is retarded by slight

increases (as little as 1�C) in air temperature (Townsend and Stewart, 1986).

12

Environmental factors such as temperature and rainfall are even more important when looking at

long-term patterns. With the global warming trends predicted, there is a concern that future

climatic trends will affect anuran breeding (Beebee, 1995). Several studies have documented

changes in anuran ecology in response to climate change (Laurance, 1996; Pounds, Fogden, and

Campbell, 1999; Beebee, 2002). Responses to past climate change is a field that has only begun

to be investigated by amphibian biologists (Alexander and Eischeid, 2002; Kiesecker et al.,

2001; Pounds, 2001). This is an area of research that is difficult to provide evidence for, as in

most cases past climate change trends are still being debated (Thuiller, 2004; Midgley and

Thuiller, 2005). However, it is a field that requires further investigation as this information

could be used to predict anuran responses to future climate change, a useful tool for the

monitoring and management of anuran populations in the wild (Pounds, 2001).

13

1.4 SUMMARY OF STUDY

This is the first systematic study of the abundance, distribution and phenology of the Fiji tree

frog in a defined area. It will contribute to the knowledge base, especially data concerning

habitat preferences and activity patterns of the tree frog over temporal and spatial scales. This

information will assist future researchers to develop more efficient and effective

surveying/monitoring procedures.

1.4.1 Aims and Objectives

The aim of this study is to record the abundance, distribution, and activity patterns of the Fiji tree

frog over a one-year period in the Savura Forestry Reserve (Figure 1.5), and to determine the

factors that influence these variables. The specific objectives of this study are to: (a) to identify

the habitats in which tree frogs are most prevalent in Savura, (b) to identify microhabitats

occupied by individuals and determine microhabitat preferences, and (c) to identify changes in

activity patterns over a one-year sampling period. Recommendations for the design of effective

surveying of tree frog populations in Fiji, with a focus on environmental conditions and habitat

preferences, will be summarised for any future research on the species.

14

Colo-i-Suva

Colo-i-Suva Mahogany Forest Reserve

PRIN

CESS

ROAD

N

Colo-i-Suva Mahogany Forest Reserve

Forestry Station

Savura Forest Reserve

Vago Forest Reserve

Figure 1.5 Map of the study site showing general features such as roads, hydrology,

reserves, and pylon lines (adapted from Fiji Map Series 31 - Government of Fiji,

1989 and 1992). Note that the tributaries of the Savura Creek are not shown in

the map due to spatial limitations.

0 1km

KEYStream

Main road

Unsealed road

Dirt road

Pylons & cable

Lake

Building

Water tank

15

Chapter 2 Major habitat preferences of the Fiji tree frog in the Savura area.

2.1 INTRODUCTION

Many anuran species display habitat preferences based on forest canopy cover (Gregory, 1983;

Brown and Rose, 1988; Ovaska, 1991; Parris, 2004). Other elements of the vegetation may also

influence anuran activity, such as species composition and structure (Stewart and Pough, 1983).

Although there have been numerous studies investigating anuran habitat preferences, few have

focussed on tropical species (Retallick, Hero, and Alford, 1997; Gillespie et al., 2004). The lack

of such studies is slowly being addressed with more tropical amphibian research being conducted

over the last two decades. The increased interest in this aspect of anuran ecology can be partly

attributed to the growing concern over global amphibian declines.

The issue of global amphibian declines was first highlighted in 1989 after scientists noted

declining trends in several amphibian populations (Alford and Richards, 1999). Blaustein and

Wake (1990) reviewed the wide range of causative agents implicated in the case studies

presented at this initial conference on amphibian declines. Loss of habitat and various forms of

habitat modification were implicated in many species declines (Sih et al., 2000; Young et al.,

2001; Collins and Storfer, 2003; Hero and Morrison, 2004). An area of concern highlighted by

these reviews is the lack of research being conducted on declining tropical species (Young et al.,

2001; Storfer, 2003; Hero and Morrison, 2004). This is alarming considering that tropical

regions are generally amphibian hotspots of biodiversity (Duellman, 1999; Houlahan et al.,

2000; Carey et al., 2001).

Tropical habitats, in particular tropical rainforests, are intricately complex ecosystems that are

home to a large diversity of anurans, such as the platymantids of Fiji. Structural features like the

16

availability of retreat sites and type of canopy cover are important limiting factors within habitats

occupied by herpetofauna (Gregory, 1983; Parris and McCarthy, 1999). Stewart and Pough

(1983) showed that the availability of retreat sites and nest sites act as regulatory factors for

population size and density. The quality and quantity of microhabitats will obviously differ

between habitat types due to differences in structural features. As a result, frog species in

different habitats may have strikingly contrasting life history characteristics (Ovaska, 1991).

The Fiji tree frog (Platymantis vitiensis) is an endemic anuran that has been recorded in areas of

lowland and highland rainforest of the Fiji Islands (Morrison, 2003). Tree frogs are also present

in disturbed habitats such as mahogany plantations (Swietenia macrophylla) and edible root

crops, such as dalo (taro), Collocasia esculenta. The tree frog is thought to exhibit a preference

for riparian strips within intact rainforest (Gorham, 1971; Pernetta and Watling, 1978; Watling

and Zug, 1998). The other endemic anuran, the Fiji ground frog (Platymantis vitianus) shares

many ecological characteristics with its arboreal relative.

Ground frogs are listed as endangered because of habitat loss and the impact of introduced

predators (IUCN, 2004). Recently the tree frog was categorised as near threatened, on the IUCN

Red List due to increasing habitat alteration and loss (IUCN, Conservation International, and

NatureServe, 2004). In order to estimate the threat of habitat loss to extant tree frog populations,

we need to understand the relationship between P. vitiensis and their habitats. This study

investigates the habitat preferences of tree frogs in a forest reserve in Fiji. The aims of this

chapter are to (a) determine the relative abundance of tree frogs in three habitat types within the

Savura area (which includes the Vago, Savura and Colo-i-Suva Forest Reserves), and (b) to

investigate the effect of rainfall and temperature on the abundance of tree frogs at each site.

17

2.2 METHODS

2.2.1 Study site

The Savura and Vago Forestry Reserves are located approximately 10km north of central Suva,

Fiji (Gibbons and Guinea, 1983). Access to the reserves is restricted and the area has never been

logged prior to the establishment of Vago Reserve in 1959, and Savura Reserve in 1963 (Keppel

et al., 2005). The Savura area is a good representative of primary rainforest in the southeast of

Viti Levu Island. The relatively pristine state of the area has allowed a population of Fiji tree

frogs to persist despite close proximity to humans.

The major habitats within Savura are lowland and highland rainforest, with patches of grassland

and mahogany plantations on the periphery of the forest area (Keppel et al., 2005). An unsealed

road runs northeast through the reserve, and several smaller tracks provide access into the forest

and to the streams (Figure 1.5). The climate of Savura is generally warm and wet during the

months of November to April, and cool and dry from May to October. The study area has

undulating ridges (an altitudinal range of 20-400 m), with steep slopes and narrow stream

valleys, in which there are several small fast-flowing streams that drain the catchments into a

tributary of the Rewa River.

2.2.2 Habitat Surveys

Three habitat types were selected for this study based on percent cover in the Savura area. One

site from each habitat type was surveyed once a month, a total of 12 sites per habitat type (Figure

2.1; refer to Appendix 1.1 for the map co-ordinates for each site). Each sampling night was

randomly allocated each month to prevent any possible bias that may occur due to the order in

which the habitats were surveyed. Surveys were conducted along accessible lowland streams

18

within the Vago and Savura Forest Reserves, for two hours each night by three searchers, similar

to the Visual Encounter Survey (VES) method (Heyer et al., 1994). Captured frogs were placed

in plastic click seal bags for processing by the principal researcher.

All individuals encountered were weighed with a 60g Pesola scale (1g accuracy). The SUL of

each frog was measured using a Vernier calliper (0.1mm accuracy). Individuals were sexed

where possible using indicators like weight and SUL, the presence/absence of a yellow groin

flash, and presence/absence of egg masses (observed through slightly transparent abdominal

skin). Adult males were identified as individuals weighing more than 1.5g and displaying the

yellow groin flash. Adult females are reproductively mature at larger sizes and therefore do not

display the yellow groin flash at smaller sizes like male frogs.

Air and stream temperatures were recorded at the beginning and end of each two hour survey

using a standard alcohol thermometer. Rainfall data was obtained from the Fiji Meteorological

station in Laucala Bay. Rainfall for the 24 hour period was measured at the station at

approximately 2100 hours each night.

2.2.3 Data Analyses

The survey data was analysed using a single factor ANOVA with twelve sites (replicates) per

habitat type. The hypothesis was that there is no difference between the total numbers of tree

frogs captured at riparian sites within the three different habitats in the Savura area. This

hypothesis was tested because we predicted that tree frogs are more likely to be found in primary

rainforest than in more disturbed habitats. This is because certain aspects of habitat structure

(e.g. canopy cover) and other factors, such as plant species composition, are thought to play an

important role in site selectivity of amphibians (Stewart-Koster et al., 2003). Canopy cover can

19

limit the amount of sunlight filtering through to sub-canopy and forest floor vegetation,

therefore, influencing air temperature within the rainforest and in retreat sites.

The influence of habitat type had on frog abundance at the 36 sites was determined using a single

factor ANOVA. A Pearson’s correlation between air and stream temperature was used to

confirm the hypothesis that air and stream temperatures are highly correlated. The effect of

rainfall and air temperatures on frog abundance was determined using multiple regressions. The

interaction between the significant weather variables and habitat was analysed in an analysis of

covariance (ANCOVA).

2.3 RESULTS

2.3.1 Results of the Habitat Surveys

A total of 144 frogs were captured in primary lowland rainforest (PlRf) sites, 53 in disturbed

secondary lowland rainforest (DSlRf) sites, and 64 from mahogany plantations (Mhgy) over the

year (a total of 24 hours of survey time per habitat type). The relatively high variance in the total

abundances of frogs found in primary lowland rainforest sites (Table 2.1) is due to an outlier

population at site P12. Tree frog abundance at P12 constitutes 36.1% of the total abundance of

frogs recorded from all primary rainforest sites (Figure 2.2).

The abundances were log transformed to account for the effect of the outlier, and a non-

significant Levene’s test (Levene’s statistic= 0.25, p = 0.78) indicated the variances of the log

data were homogenous between habitats. Habitat type had a weak significant effect on frog

abundance at the 36 sites (F2, 33= 3.43, p = 0.04).

20

VagoCk

Savura

Ck

D1

P10

D9

P2

P8D6

P7

D8

D10

P6

D3

D7

D2D5

D4

P3

P1

P5P4

P7

P9

M1

M5

M7

M4 M6

M3

M9

M8M10

M2

M11

P11

P12

D11

D12

M12

Figure 2.1 Map of the study site showing the locations of habitat sites surveyed between June

2004 and May 2005. Green squares - Primary lowland rainforest sites (P1–P12),

Yellow squares - disturbed secondary lowland rainforest site (D1–D12), and Maroon

squares – mahogany plantation sites (M1–M12).

0 1km

KEYStream

Main road

Unsealed road

Dirt road

Lake

21

Table 2.1 Descriptive statistics of untransformed frog counts: standard deviation, variance and

standard error of the mean.

Habitat Type Total of Counts Mean Standard Deviation Variance S. Error Primary 144 12.00 13.41 179.82 3.87 Secondary 53 4.42 3.60 12.99 1.04 Mahogany 64 5.33 3.82 14.61 1.10

22

8.36

4.75 5.38

0

10

20

30

40

50

60

Primary Secondary Mahogany

Habitat types

Tota

l no.

of f

rogs

cap

ture

d

Figure 2.2 Frog abundance at twelve sites within the three different habitat types and mean

number of frogs per habitat type. Several data points for sites within the same

habitat were coincident and are darker than single data points.

n=12 n=12 n=12

23

05101520

Jun-

04Ju

l-04

Aug

-04

Sep-

04O

ct-0

4N

ov-0

4D

ec-0

4Ja

n-05

Feb-

05M

ar-0

5A

pr-0

5

Mon

th/y

ear

Total No. of Frogs Captured per 2h Survey

Prim

ary

low

land

rain

fore

st

Seco

ndar

y di

stur

bed

low

land

rain

fore

st

Mah

ogan

y pl

anta

tions

Figu

re 2

.3

Tem

pora

l var

iatio

n in

tree

frog

abu

ndan

ce in

eac

h of

the

thre

e ha

bita

t typ

es fr

om J

une

2004

to M

ay 2

005.

The

out

lier

poin

t P12

is re

mov

ed to

redu

ce sk

ew d

ue to

this

poi

nt. C

oinc

iden

t poi

nts a

re d

istin

guis

hed

as u

n-fil

led

sym

bols

.

24

There was no graphical trend in the numbers of tree frogs recorded each month in the different

habitats, to indicate an influence of tree frog phenology on the survey results (Figure 2.3).

2.3.2 Weather Data and Analysis

The average air and water temperatures recorded at each site and the average rainfall of the

sample days in a month are shown in Table 2.2. The result of the Pearson’s correlation between

air temperature and stream temperature was very significant (P.C. = 0.839, p< 0.001, n= 36). As

water temperature was so highly correlated to air temperature (77% of the variation in water

temperature was explained by air temperature; Figure 2.4), water temperature was removed from

further analyses. Log transformed frog abundances were not significantly affected by air

temperature in any habitat (t2, 33= 0.12, p= 0.90). However, rainfall in the 24 hour period prior to

and during sampling exerted a significantly negative effect on the transformed frog abundances

(t2, 33= -3.13, p= 0.004; Figure 2.5).

The analysis of covariance of the log transformed frog abundances in the different habitats with

rainfall as a covariate, suggests that rainfall exerted a greater influence (F1, 32= 8.46, p= 0.007) on

survey results than the habitat (F2, 32=2.70, p= 0.08) at each site. It was observed that on weeks

when it rained every day leading up to the sampling night, fewer tree frogs were found. On

several occasions when diurnal showers were heavy, very few frogs were captured that night.

To investigate the effect high rainfall in the 24-hour period prior to sampling had on frog counts,

results from nights when the 24-hour rainfall exceeded 11 mm were removed from the

ANCOVA. The relationship between rainfall and the log-transformed frog abundances in the

different habitats was non-significant in this analysis (F1, 28= 1.69, p= 0.21). The influence of

habitat type on frog abundance was also non-significant in this analysis (F2, 26= 2.61, p= 0.09).

25

Table 2.2 Weather variables (average values from the three sampling nights) and frog

abundance recorded for the habitat surveys.

Month Frog abundance in all

habitats Average rainfall

(mm) Average air temperature

(ºC) Jun-04 27 1.83 22.08 Jul-04 21 3.53 21.58 Aug-04 12 13.33 22.50 Sep-04 11 11.90 22.33 Oct-04 28 0.23 23.75 Nov-04 9 0.33 23.00 Dec-04 14 20.70 25.67 Jan-05 16 0.73 24.33 Feb-05 23 14.73 25.33 Mar-05 23 2.67 25.47 Apr-05 18 1.77 23.67 May-05 60 0.00 22.00

26

y = 0.99x + 0.33R2 = 0.77

20.00

21.00

22.00

23.00

24.00

25.00

26.00

27.00

21.00 21.50 22.00 22.50 23.00 23.50 24.00 24.50 25.00 25.50 26.00

Air temperature (oC)

Wat

er/s

tream

tem

pera

ture

(o C)

Figure 2.4 The strong relationship between air and stream temperatures recorded during the

habitat surveys.

27

Figure 2.5 The relationship between rainfall and the log-transformed frog abundance in the

three habitats. The equation of the regression line and the regression coefficient

are shown for the significant (F1, 10= 5.42, p=0.04) relationship between rainfall

and frog abundance in secondary habitat.

00.5

11.5

22.5

33.5

44.5

0 2 4 6 8 10 12 14

Rainfall (mm)

Log

of fr

og a

bund

ance

y = -0.03x + 1.77R2 = 0.59

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60 70

Rainfall (mm)

Log

of fr

og a

bund

ance

0

0.5

1

1.5

2

2.5

3

0 5 10 15 20 25

Rainfall (mm)

Log

of fr

og a

bund

ance

Primary forest

Secondary forest

Mahogany plantations

28

2.4 DISCUSSION

2.4.1 Habitat Selection

Frog abundance was slightly greater in primary lowland rainforest habitat, than in the secondary

lowland rainforest and mahogany forest habitat. This suggests Fiji tree frogs can persist even in

disturbed habitat patches. Low frog abundances have been recorded in secondary vegetation in

other studies (Galindo-Leal et al., 2003), which is linked to loss of suitable microhabitat. The

influence of microhabitat variables on frog abundance is discussed in the Chapter 3.

Fiji tree frogs may not be restricted to primary habitat like many threatened species found in the

New World tropics (Streatfield, 1999); however, their distribution may be limited by structural

components of primary rainforest and possibly secondary formations. Canopy cover, species

composition, the density of under-storey vegetation, and food availability, may affect tree frog

distribution patterns, and, as these factors were not investigated in this study, future research

examining these variables is recommended. The large number of tree frogs recorded at P12 is

likely to be due to site-specific habitat features that were not examined in this study.

Additionally, slightly higher numbers of captures are recorded in mahogany forest than in

secondary sites. Forestry staff at Colo-i-Suva rarely enter these mahogany forests/ plantations at

night and little logging has taken place in the reserve over the last few years. The riparian

vegetation that grows along the narrow streams in the mahogany reserve is very similar in

species composition to the primary sites in the Vago and Savura catchments. The absence or

presence of tree frogs along riparian strips may be linked to the presence of certain plant species

(e.g. Pandanus), as indicated for other anurans (Gregory, 1983; Parris, 2004).

29

2.4.2 Influence of Weather on Survey Results

The significantly negative relationship between rainfall and frog abundance at the sites indicates

that rainfall plays an important role when surveying frogs. As we surveyed the 12 sites in each

habitat over twelve months, we reduced the temporal bias that may occur when sampling

intensively within a year. Although the study site is located within the wetter region of Viti Levu

Island, there were marked changes in the amount of rainfall over the sampling period.

It is notable that only a few frogs were ever recorded in the secondary disturbed rainforest sites,

during or after a day of heavy rainfall. Low numbers of frogs observed at such sites are probably

due to heavy rainfall affecting frog activity and detectability, rather than there being an absence

of tree frogs. As the sampling programme was designed with surveys at set times, surveys were

conducted in a range of weather conditions. The effect of rainfall on detectability of the tree

frogs at night and on the activity of tree frogs clearly influences surveys. Sampling should be

conducted on nights when rainfall in the 24-hours prior to a survey is lower than 10mm.

Air temperature at the habitats varied very little throughout the year, and did not have a

significant influence on abundances of tree frogs in any of the habitat types. However, this

weather variable is still important as the effect of altitudinal variation in air temperature on tree

frog activity was not investigated in this study. Altitudinal variation in anuran activity patterns

has been recently demonstrated for many anurans including tropical species (Morrison and Hero,

2003). Therefore, it is recommended that in future, research on Fiji tree frogs should factor in

the effect of weather variability in different habitats at different altitudes to clearly elucidate

patterns in habitat occupation.

30

2.5 SUMMARY

Fiji tree frogs in the Savura area were slightly more abundant in primary lowland rainforest sites

than mahogany plantations and disturbed secondary lowland rainforest sites. Human disturbance

might be a factor influencing the abundance of tree frogs, as they were more common along

streams in the less disturbed mahogany plantations, than the secondary forest sites. Rainfall had a

significantly negative effect on frog numbers recorded in each habitat site, and future research on

tree frogs should be conducted when rainfall during the 24-hour period prior to the survey is

lower than ten millimetres.

31

Chapter 3 Microhabitat selection of Platymantis vitiensis within the Savura area

3.1 INTRODUCTION

Amphibians tend to inhabit only ‘subsets’ of the range of situations within a habitat, to suit their

biological needs (Parris and McCarthy, 1999). These subsets within the total area available are

termed ‘microhabitats’ and are simply the specific locations where individuals may be found.

Understanding microhabitat selection by amphibians allows researchers to have a greater

understanding of how amphibians may respond to habitat modification (Fischer, Lindenmayer

and Cowling, 2003). This is a key concern in the conservation of amphibians as habitat

modification is one of the major threats to global amphibian populations (Zimmerman and

Bierregaard, 1986; Sih et al., 2000; Hero and Morrison, 2004).

Several studies indicate shelter or retreat site selection by anurans is largely influenced by the

quality of the microhabitat (Townsend, 1989; Ovaska, 1991). One of the main factors selected

for is the amount of moisture in the microhabitat (Stewart, 1985; Townsend, 1989; Schwarzkopf

and Alford, 1996; Smith et al., 2003). The microclimate of retreat sites is in turn affected by

structural complexity of the habitat, in particular density of the canopy and the under-storey

vegetation (Gregory, 1983; Parris, 2004). Favourable habitat and microhabitat selection allows

anurans to thermoregulate within optimal temperature ranges (Beebee, 1996).

Microhabitat selection may differ between age/size classes and sexes (Stewart, 1985; Townsend,

1989; Inger, 1994a; Beard et al., 2003). Adult frogs may select microhabitats based on different

prerequisite features to juveniles and metamorphs/hatchlings (Stewart, 1985; Beard,

McCullough, and Eschtruth, 2003). Females tend to be the larger sex among frog species, and

because of their larger size, they may require different microhabitats. Microhabitat selection will

32

also differ between nocturnal activity and diurnal retreat sites (Stewart, 1985). A study of anuran

microhabitat selection must take into account the type of activity being conducted by the species

during surveys (Gillespie et al., 2004). Foraging, reproduction, and retreat for thermoregulatory

and defence purposes are the main reasons for microhabitat selection by amphibians.

Microhabitat studies generally tend to be descriptive in nature (Beard et al., 2003), but more

researchers are attempting to quantify selection by measuring variables such as the height of a

perch above ground, the distance from a water body, and the angle of the perch site (Retallick,

Hero and Alford, 1997). Environmental characteristics such as the features of the stream or

water body (e.g. velocity, depth, and width), riparian vegetation present, leaf litter, and substrate

should also be recorded (Retallick et al., 1997; Gillespie et al., 2004). Since the publication of

Heyer et al. (1994), there has been a standard set of variables used in the description of

microhabitats. Vegetation, horizontal position, vertical position, and substrate are the main

characteristics used for amphibian studies (Inger in Heyer et al., 1994).

This chapter looks at the microhabitat selection of Fiji tree frogs along two permanent transects

on Vago Creek in the Savura area near Suva, Viti Levu, over a 12-month period. I investigated

whether characteristics of the perch site (substrate and height above ground) and proximity to

streams affected perch site selection of tree frogs.

3.2 METHODS

3.2.1 Data collection: permanent transect surveys

A 200m permanent transect line was set up and marked out using rope and flagging tape, along a

major stream where tree frog activity had been previously observed (Morrison, pers. comm.,

2004). A second parallel transect line of the same length was marked out in the rainforest

33

adjacent to the stream using flagging tape and nylon rope, with a 10m buffer zone between the

two transects. The buffer zone was not too wide so that confounding environmental variables

might prevent comparisons between results from the two transects, but was wide enough to

prevent the mixing of individuals sampled on either transect. The research team surveyed both

sides of the 200m transects within a 5m strip along the transect line. The transect surveys were

conducted twice monthly, at the beginning and end of each sampling week.

Frogs were located and processed as described in the Chapter 2. The microhabitat information

recorded for each captured frog included: vegetation/substrate (plant species where possible),

horizontal position (distance from nearest stream), vertical position (position and height above

ground on flora) (Inger in Heyer et al., 1994). Logistical difficulties prevented the samplers

from measuring the actual perch height of each captured frog and its distance from the stream.

3.2.2 Microhabitats occupied in different habitats

Twelve sites in each of the three different habitat types were surveyed over a twelve-month

period (one site per habitat each month). Two-hour nocturnal surveys were conducted along a

stream at each site, as described in Chapter 2. Captured frogs were placed in plastic bags for

processing. All captured individuals were weighed, and their SUL and TL measured.

Individuals were sexed, where possible, using indicators like weight and SUL, the

presence/absence of a yellow groin flash, and the presence/absence of egg masses (Chapter 2).

The microhabitat variables investigated were the same as in Section 3.2.1.

34

3.2.3 Data collation

Microhabitat data from the habitat surveys and the permanent transects was collated separately,

because the methods differed slightly between the habitat surveys and transect surveys. Perch

height, substrate, and distance from the nearby stream for each frog captured in the habitat

surveys were recorded. Perch height, substrate, and distance from stream was also recorded in

the transect surveys, along with the numbers of frogs found along the two transects.

3.2.4 Data analysis

The microhabitats of frogs captured along the two permanent transects were analysed separately

from the habitat survey data. The following variables from the transect data were analysed using

single-factor ANOVAs: the estimated heights above ground (perch heights), the estimated

distances from the stream (only for frog records from the stream transect), and the nature of the

substrate of the perch site. Two-way ANOVAs were used to determine the significance of

habitat type with the three variables above. The abundance of frogs along the stream and land

transect were compared using a paired t-test to determine selectivity for streamside

microhabitats.

3.3 RESULTS

3.3.1 Microhabitat selection along the permanent transects

Frogs were encountered on a great variety of plant species along the stream and within the forest.

The ANOVA results indicate that tree frogs select specific plants for nocturnal perch sites (F12,

273= 46.20, p= <0.001). The most popular choice was Pandanus (Pandanus spp.), followed by

ground ferns (Pteridophytes), and the endemic Dolicholobium biflora (Figure 3.1). A complete

list of plant species on which tree frogs were observed is provided in Appendix 2.1. Tree frogs

35

were commonly found on the leaves of the vegetation, but on Syzygium seemannii and Ficus

bambusifolia, they were always perched on the branches.

S. seemannii and F. bambusifolia were adjacent to the stream and larger frogs were often

observed in these plants, as their dense tangle of branches was ideal foraging sites for the frogs.

Most tree frogs along the Vago transects inhabited perch sites from 0-150 cm above the ground

(F9, 210= 36.493, p= >0.001; Figure 3.2). The significant result of perch heights may also be due

to the significant effect of the plant substrate. As Pandanus plants were the most common

substrate choice for frog perches, tree frogs were more likely to be perched at heights of 1-150

cm above the ground on these shrubs.

Most frogs were found within two metres of the stream (F4, 100= 26.23, p= >0.001). However,

many frogs were captured between four and five metres from the stream (Figure 3.3). The

results of the individual ANOVAs (Table 3.1) for all three microhabitat variables indicate that

tree frogs select perches on certain plant species, close to the ground, and within a few metres

from a stream.

36

2.68

1.73

9.41

3.45

1.00

1.36

4.23

0.23

0.59

0.41

1.45

1.005.

91

024681012141618

Syzyg

ium

Ficus

Panda

nus

Dolich

olobiu

m

Dilenia

Angiop

teris Grou

nd Pter

idoph

tyeGrou

nd O

rchid

Freycin

etia

Acalyp

ha

Barring

tonia

Palm

Other

Subs

trate

of p

erch

site

No of Frogs per Survey

Figu

re 3

.1

Subs

trat

e of

per

ch si

tes o

ccup

ied

by tr

ee fr

ogs a

long

the

two

tran

sect

s on

Vago

Cre

ek, S

avur

a. B

ars r

epre

sent

sam

ple

mea

ns (v

alue

s adj

acen

t to

bars

).

37

6.05

9.36

10.86

3.73

2.05

0.50 0.59 0.05 0.09 0.090

2

4

6

8

10

12

14

16

18

20

22

0-50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 450+

Perch Heights of Frogs (cm)

No

of F

rogs

per

Sur

vey

Figure 3.2 Number of tree frogs encountered at different perch heights along both fixed

transects, Vago Creek, Savura. Bars and values represent mean number of frogs

at each height.

38

7.90

2.81

1.81

1.05

4.90

0

2

4

6

8

10

12

14

16

0 - 1.0 1.1 - 2.0 2.1 - 3.0 3.1 - 4.0 4.1 - 5.0

Distance of Frogs from Stream (m)

No

of F

rogs

per

Sur

vey

Figure 3.3 The distances of captured tree frogs from the stream transect along Vago Creek.

Bars and values represent the mean number of frogs captured during 21 surveys.

39

Table 3.1 Results of Univariate ANOVAs on Microhabitat Data from the Transects.

ANOVA Source of Variation SS df MS F P-value F crit Substrate of microhabitat Between Groups 1845.322 12 153.777 46.202 <0.001 1.788 Within Groups 908.636 273 3.328 Total 2753.958 285

Estimated Perch Heights Between Groups 669.109 9 74.345 36.493 <0.001 1.925 Within Groups 427.818 210 2.037 Total 1096.927 219

Estimated Distances to the stream Between Groups 641.200 4 160.300 26.234 <0.001 2.463 Within Groups 611.048 100 6.110 Total 1252.248 104

40

3.3.2 Microhabitat selection within the three major habitats

In the three different habitats surveyed, Pandanus and Dolicholobium were the main plant

species on which tree frogs were found, followed closely by the ground ferns (Figure 3.4). Tree

frogs in the three habitats significantly selected plant species as perch sites (F2, 11= 4.15, p=

0.002). Plant substrate appears to be a significant microhabitat variable within the three habitat

types investigated (F2, 11= 5.27, p= 0.01). Pandanus are a common species in the lowland

rainforests in Fiji, however these plants tend to form patchy distributions and are not dominant

shrubs in the Savura and Vago Reserves (Keppel et al., 2005).

Tree frogs in the habitat surveys were predominantly perched above the ground between 0-150

cm (F2, 9= 4.07, p= 0.005; Figure 3.5). The majority of tree frogs were encountered less than

two metres from a stream (F2, 4= 4.41, p= 0.04; Figure 3.6). There was no relationship between

perch heights and proximity of the perch site to a stream, and habitat type (Table 3.2).

3.3.3 Comparison between frog activity along the stream and land transects

The number of frogs encountered along the stream each night were significantly greater than the

number of frogs encountered along the land transect with a total of 372 frogs captured (excluding

recaptured individuals) along the stream compared to 276 along the land transect (t21= 3.15, p=

0.002; Figure 3.7).

41

0

5

10

15

20

25

30

35

40

45

50

55

60

Syzygi

um Ficus

Panda

nus

Dolich

olobiu

mDile

nia

Angiop

teris

Ground

Pterido

phtye

Ground

Orch

id

Common

Lily

Chamiss

onis

Freycin

etia

Other

Microhabitat vegetation

Tota

l Num

ber o

f Fro

gs E

ncou

nter

ed in

Mic

roha

bita

t

Mahogany plantations

Disturbed secondary lowland rainforest

Primary lowland rainforest

Figure 3.4 Vegetation utilised by tree frogs as perch sites along streams in the three major

habitats. A total of eight plant species that were uncommonly used as perch sites

are lumped in the “other” category.

42

0

10

20

30

40

50

60

0-50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 450+

Perch height (cm)

Tota

l Num

ber o

f Fro

gs C

aptu

red

Primary lowland rainforestDisturbed secondary lowland rainforestMahogany plantations

Figure 3.5 Total numbers of tree frogs encountered at different perch heights in three

different habitats in the Savura area.

43

0

10

20

30

40

50

60

70

80

0 - 1.0 1.1 - 2.0 2.1 - 3.0 3.1 - 4.0 4.1 - 5.0

Estimated distance from stream (m)

Tota

l Num

ber o

f Fro

gs C

aptu

red

Primary lowland rainforest

Disturbed secondary lowland rainforest

Mahogany plantations

Figure 3.6 Estimated distances of tree frogs (to nearby streams) captured in three different

habitats in the Savura area.

44

Table 3.2 Results of Two-way ANOVAs on Microhabitat Data from the Habitat Surveys.

ANOVA Source of Variation SS df MS F P-value F crit

Substrate selection & habitat type Habitat Types 339.5 2 169.75 5.27 0.01 3.44 Substrate 1469 11 133.55 4.15 0.002 2.26 Error 708.5 22 32.20 Total 2517 35

Perch height & habitat type Habitat Type 407.4 2 203.70 2.89 0.08 3.55 Perch Height 2578.8 9 286.53 4.07 0.005 2.46 Error 1266.6 18 70.37 Total 4252.8 29

Distance from stream & habitat type Habitat Type 654.93 2 327.47 2.46 0.15 4.46 Proximity to Stream 2344.67 4 586.17 4.41 0.04 3.84 Error 1063.73 8 132.97 Total 4063.33 14

45

12.55

16.91

0

5

10

15

20

25

30

35

Land Transect Stream Transect

Transect

Tota

l No.

of F

rogs

Cap

ture

d pe

r Sur

vey

Figure 3.7 Abundance of Fiji tree frogs encountered along the land transect compared to the

stream transect; n=21 surveys (mean values indicated by dashed symbols).

46

3.4 DISCUSSION

The rainforests and secondary forests of the Savura area are very biodiverse habitats and tree

frogs have a wide range of plants to select from for perch sites. However, the tree frogs surveyed

in the three habitats and along the transects were often found on certain vegetation. Tree frogs

appear to be mostly found on Pandanus spp. along streams and in flat marshy areas. Similar

results were previously reported by Gorham (1968), Pernetta and Goldman (1977), and Ryan

(1984). Most of the frogs in this and previous studies were found in the base of the Pandanus

leaf axil, which collects leaf litter and rainwater. Besides Pandanus spp. these included low-

lying ferns and aroids (Alocasia indica), and shrubs (Dilenia biflora, Ficus bambusifolia and

Syzygium seemanii).

In several cases, we found tree frogs on the leaves of creeping epiphytes wound around the

trunks of larger trees (e.g. Derris elliptica). A similar association with specific plant species has

also been indicated for coqui frogs, Eleutherodactylus coqui (Beard et al., 2003). Ficus and

Syzygium flower between December and January, attracting many flying insects during this time,

which we observed attracted many tree frogs.

Individual frogs were generally found between 0–150 cm above the ground during our surveys.

This may be due to sampling bias, i.e.: the sampling team was more likely to see and capture tree

frogs from perch sites between 0-150 cm (body level). Frogs were found perched on vegetation,

except on one occasion where a frog was perched on a rock beside the stream transect.

Generally only one individual was found on each plant, however, on occasion several frogs were

observed on the same plant. These were commonly metamorphs and hatchlings on Pandanus.

Frogs of different age/gender classes may select different plant species and perch heights (Beard

47

et al., 2003). On one occasion a large female and smaller male were captured from the same

plant but at different locations.

Tree frogs showed a strong affinity for streamside sites as most frogs were found within two

metres of the stream in all habitats and along the stream transect. This may be due to the greater

abundance of flying insects in the open space of the riparian strip (Olson, pers. comm., 2002),

where there would be a higher rate of feeding success during nocturnal foraging. As more frogs

on average were recorded along the stream transect than the land transect, Fiji tree frogs appear

to select nocturnal perch sites along forest streams for foraging.

The result that most tree frogs were captured near the stream may also be due to the experimental

design, as the principal researcher and another member of the team searched on either side of the

stream, while a third member searched between three to five metres from the stream.

The possible effect of the sampler bias can be seen in Figure 3.3. However, sampling was

limited by the steep terrain along the stream transect. The left bank (downstream direction) was

steeper with a narrower terrace (mostly bedrock with vegetation growing on the rock). The right

bank was mostly flat with a wider river terrace on which we set up the parallel land transect.

During periods of heavy rainfall, tree frogs may abandon nocturnal streamside activity in favour

of safer perch sites underneath the canopy of the forest (Chapter 4). The influence of weather on

perch and retreat sites of anurans has been reported previously (Ritke and Babb, 1991). Rainfall

was the most significant variable in determining tree frog activity along the transects (refer to

Chapter 4). Rainfall patterns have been found to influence the microclimates of diurnal retreats

and nocturnal perch sites of tree frogs by affecting the moisture levels in leaf litter and the

moisture present on vegetation surfaces (Kam and Chen, 2000). As moisture levels in their

48

environment affect skin-surface respiration (Zug, 1993; Beebee, 1996), it is likely that tree frogs

select arboreal sites that retain some tree-flow (rainfall that is intercepted by vegetation).

Pandanus, Dilenia, and Dolicholobium are good examples of plants that retain tree-flow in leaf

litter, axils, sheathed petioles, and on their leaves.

Feeding in more exposed perch sites increases the likelihood of predation, but no large predators

were observed at the study site with the exception of three rats (Rattus spp.). Only one cane toad

was observed in the first three months of the survey, but no toads were ever observed thereafter.

The only forms of predation observed firsthand were smaller frogs being eaten by larger females,

and the lone record of a spider (Heteropoda sp.) on top of a metamorph-sized tree frog, which

was wound up tightly in web silk. It appeared to be injecting digestive fluids or ingesting

already pre-digested fluids from the dead frog. Ryan (1984) mentions spiders as possible

predators of small P. vitiensis but did not provide any evidence of predation events.

Aichinger (1987) observed that the abundance of large spiders increased with greater anuran

activity during the breeding season. We also noted an increase in the number of spiders over the

last few months of the study (May to August), however, this occurred during the dry season in

contrast with Aichinger’s study.

3.5 SUMMARY

Fiji tree frogs, like other arboreal anurans, were found in microhabitats with specific structural

and ecological features, particularly height above ground and substrate of the perch site. Another

important spatial variable that appears to influence Fiji tree frog activity is proximity to a stream

channel. These features affect the microclimate of the perch site, in particular temperature and

49

moisture, which are factors that directly affect frog activity. Fiji tree frogs were most commonly

found on Pandanus leaves and ferns, as well as the broad-leaved D. biflora. The frogs were

often found on riparian vegetation, and may prefer perch sites near the stream for foraging. It is

speculated that increased risk of desiccation on windy nights with low humidity and cool

temperatures, or increased risk of mortality on nights with heavy rainfall and high stream levels

may result in the frogs abandoning these perch sites.

50

Chapter 4 Phenology of Platymantis vitiensis along Vago Creek over a one-year period.

4.1 INTRODUCTION

The long-term conservation and monitoring of amphibians is dependant on various resources

available to project managers. Arguably the most important information necessary for an

effective monitoring programme is the population dynamics of the species of concern (Biek et

al., 2002). Although, it is thought that Fiji tree frogs breed year round with the majority of

breeding activity between December and March (Gibbons and Guinea, 1983; Ryan, 1984;

Morrison, 2003), the literature to date has largely been based on short-term non-systematic

survey data. Globally, the current understanding of amphibian population dynamics is a result of

long-term phenological studies with a minimum of a twelve-month survey period (Gill, 1985;

Crump and Pounds, 1989; Caetano and Leclair, 1999).

Tree frog reproduction is thought to peak between late February and early March as with the

ground frog but this has yet to be confirmed (Morrison, 2003). Clutches of 13-30 eggs (about 7-

9mm in diameter) have been commonly recorded in the axils of Pandanus plants, where

rainwater and dew collects (Ryan, 1984). Hatchlings leave their egg cases approximately 30

days later following development nourished by large yolk sacs (Gibbons and Guinea, 1983). The

metamorphs usually remain dark brown in colour over the first few weeks (Ryan, 2000) and then

their skin colour begins to lighten and show distinctive skin patterns and colouration. Once

sufficiently developed, metamorphs are active and often found in the safety of Pandanus axils.

Laboratory work with captive individuals and audio-spectrographic analysis confirmed that both

sexes call, a rare phenomenon in anurans (Boistel and Sueur, 1997). The male call is more

vocally complex than the female call, which is thought to be a courtship or ‘advertisement’ call.

51

The frequency of calling behaviour may increase during the breeding season (Morrison, pers.

comm., 2004), with female tree frogs calling in the three months prior to breeding (Boistel and

Sueur, 1997). Calling activity varies in different habitats due to the structure and composition of

the biotic environment (Morton, 1975; Duellman and Pyles, 1983; Brown and Rose, 1988), as

tropical rainforest species have to contend with dense vegetation when calling.

The majority of studies have demonstrated that peaks in amphibian breeding activity occur

during the wetter part of the year in the tropics (Aichinger, 1987; Crump and Pounds, 1989;

Gottsberger and Gruber, 2004). Periodic changes in rainfall appear to be the main weather

variable correlated with reproductive phenology (Church, 1961). However, weather variables

are not always the most influential factors determining anuran breeding. Frog phenology in

Central and South America has recently been linked to episodic fluctuations in the availability of

insect prey (Watling and Donnelly, 2002).

This chapter investigates the phenology of a sub-population of P. vitiensis in the primary

rainforest of Vago Reserve, Savura. Monthly survey data along two permanent transects (a

stream and a parallel land transect) were analysed to identify changes in the abundance of tree

frogs over twelve months. The influence of major weather variables on the phenology of this

sub-population was also determined to account for differences in activity during the study period.

4.2 METHODS

4.2.1 Study Site

Two 200 m parallel transects were set up along Vago Creek, within a narrow stream valley with

steep slopes incised by the stream into the volcanic bedrock (Figure 4.1). The site was between

52

20-60 m in elevation. The riparian vegetation grades into primary lowland slope rainforest.

Vago Creek is a fast flowing stream about five metres wide in its mid-section, and ten metres

wide near the confluence with Savura Creek. The levee is narrow, widening out near the

confluence. The transects were located in one habitat type only to prevent the bias of differential

calling activity that occurs in different habitat types.

4.2.2 Data from Site and Captured Individuals

The transects were surveyed twice a month in alternating order to reduce sampling bias. Surveys

were conducted between 1930 and 0100 hours, with an average transect duration of 1 hour and

41 minutes. Air and stream temperatures were measured on site each night with a pocket alcohol

thermometer. Rainfall data was obtained from the Fiji Meteorological Service’s Laucala Bay

station, which is recorded at 2100 hours daily. The capture and processing of Fiji tree frogs

included weighing captured frogs, measuring SUL and TL, sexing/aging individuals (based on

criteria in Table 4.1), and noting microhabitat. Captured frogs were toe-clipped using monthly

codes to identify recaptured individuals (Table 4.2).

53

Figure 4.1 Schematic diagram depicting the layout of the permanent parallel land and

stream transects along a mid-highland section of Vago Creek, Savura.

54

Table 4.1 Field Classification System for Identifying Age/Size of Captured Frogs.

Category Weight (g) Snout-Urostyle Length (mm)

Hatchlings 0 – 0.3 9.0 – 13.9 Metamorphs 0.5 – 0.9 14.0 – 19.9 Juveniles 1.0 – 1.5 20.0 – 29.9 Adults 1.6 – 3.9 30.0 – 60.0 Gravid females Identified by white egg mass visible through abdominal skin

Table 4.2 Toe-clipping Codes for Identifying Recaptured Frogs.

Month Toe Code Description September L3 Third toe on left foot October L4 Fourth toe on left foot November L5 Fifth toe on left foot December R1 First toe on right foot January R2 Second toe on right foot February R3 Third toe on right foot March R4 Fourth toe on right foot April R5 Fifth toe on right foot May L1 First toe on left foot June L2 First toe on left foot July L3R1 Third toe on left foot, first toe on right foot August L3R2 Third toe on left foot, second toe on right foot

55

4.2.3 Data Analysis

Changes in the abundance of adults, juveniles and metamorphs/hatchlings over the 12-month

study period were graphed and described. Due to the difficulty of clearly separating larger adult

males and younger adult females in the field, adult male and female (non-gravid and gravid)

abundances are combined, as were hatchlings and metamorphs. The influence of air temperature

(�C) and 24-hour rainfall (mm) on the abundances of the three age categories (adults, juveniles

and metamorphs/hatchlings) and gravid females were investigated using separate regression

analyses for each age/sex class. Frog abundances and average rainfall values were log-

transformed (log n + 1 for gravid females and rainfall, log n for adults, juveniles and

metamorphs/hatchlings) for the regressions. ANCOVA analyses were used to determine the

relationship between log-transformed abundances of the four age/sex classes along the two

transects (stream/land), with significant weather variables (from the regressions) as covariates.

To provide an independent test of the relationship between significant weather variables and frog

abundances in the different age classes, the phenology of the broad scale data (Chapter 2) was

examined using similar analyses as above. Regressions of weather data on the log-transformed

abundances of the four age/sex classes from all the habitats were performed. ANCOVA analyses

were used to determine the relationship between log-transformed abundances of the four age/sex

classes in the three habitats, with significant weather variables (to each age/sex class) as

covariate measures.

56

4.3 RESULTS

4.3.1 Phenology of the Fiji tree frog population along Vago Creek

The abundance of adults captured along the transects peaked from September to November 2004,

then decreased from December 2004 to February 2005 (Figure 4.2). Between February and

April 2005 abundance of adults fluctuated, having a noticeable relationship with high rainfall on

the sampling days in February (104 mm) and April (16.8 mm). From May to August 2005, the

abundance of captured adults declined, a period during which rainfall on the sampling days was

low (0-2 mm).

Gravid female abundance increased at the onset of the wet season and peaked in December,

followed by a decline throughout the rest of the wet season till March. There were no gravid

frogs recorded for the last four months of the survey period, from April to July of 2005,

coinciding with the beginning and first three months of the dry season (Figure 4.3).

The abundance of metamorph/hatchling tree frogs was greatest during the dry season months of

May to August 2005 (Figure 4.2). Hatchlings and metamorphs declined in abundance from

October 2004 to February 2005. The lowest number of metamorphs/hatchlings (four

individuals) was recorded in April 2005.

In contrast to metamorph activity, juvenile P. vitiensis abundance peaked during November 2004

and January 2005 (Figure 4.2). This may indicate a period of juvenile recruitment over these

months, as the abundances of juvenile frogs generally remained constant throughout the twelve-

month survey.

57

Only two egg clutches were recorded in the twelve months of surveying in this study. The first

clutch of 18 eggs was recorded in September 2004, in a Pandanus axil at a height of 0.6 metres

above the ground. The second clutch (about 10 eggs) was recorded in January 2005 at a height

of about 1.5 m in the leaf litter at the base of branches of a Crossostylus seemannii sapling. The

lack of clutch data made it impossible to use this information in the phenological analysis.

However, it is notable that one egg clutch was recorded towards the end of the dry season and

the other was recorded mid-wet season. These observations support previous work, which

suggests that Fiji tree frogs breed year round (Ryan, 1984).

4.3.2 Influence of Weather Factors: Rainfall and Temperature

Rainfall had a significantly negative effect (t2, 21= -3.39, p= 0.003) on transformed adult

abundance (Figure 4.4). Two peaks in the amount of rainfall occurred, in February and April

2005. These two peaks coincided with low frog abundance along the stream and land transects

in those months, 25 and 27 frogs respectively (Figure 4.2). April was the wettest month over the

12-month survey period, with a total of 470.1 mm. The wettest period was from October 2004 to

May 2005. It should be noted that the rainfall data was recorded at a meteorological station

about 10km from the survey site, and microhabitat variations in rainfall may affect the analysis.

The lowest number of adult frogs and metamorphs/hatchlings observed, coincided with the

heaviest 24-hour rainfall events (Figure 4.2). In contrast, juvenile frog abundance peaked during

the wetter months of November to January. Metamorphs/hatchlings were most abundant during

the dry season (May to September), which is probably due to the recent hatching of eggs in the

latter months of the wet season. Metamorphs/hatchlings were also significantly correlated with

rainfall (t2, 21= -2.06, p= 0.05) over the twelve months (Figure 4.5).

58

Air temperatures showed some intra-annual variation at the lowland rainforest site along Vago

Creek (~19-27°C). The highest average air temperature was recorded over the sampling nights

in March 2005 (26.8°C) and the lowest in August 2005 (19.6 °C). Tree frogs were observed to

be less active on cool (18-20°C) dry nights than on cool humid nights. Gravid females (t2, 21=

2.06, p= 0.05) were significantly more abundant on nights when air temperatures on the

sampling nights were higher (Figure 4.6).

Adult tree frog abundance on the sampling nights was significantly influenced by transect type

(F1, 21= 19.58, p< 0.001) and rainfall (t1, 21= 25.01, p< 0.001).

4.3.3 Phenology of Fiji Tree Frogs from the Habitat Surveys

The only age category to show a correlation with one of the two weather variables investigated,

were the adults. Adult tree frogs from the habitat surveys were significantly negatively

influenced by rainfall (t2, 33= -2.65, p= 0.01) over the twelve-month survey period (Figure 4.7).

The results of the ANCOVA confirmed that rainfall had a negative effect on adult frog

abundances in the habitats (F1, 33= 6.23, p= 0.02), while habitat type was a non-significant factor

(F2, 33= 0.90, p= 0.42). The relationship between rainfall and adult tree frog abundances is

notably difficult to see in the un-transformed data (Figure 4.8). The lack of clear trends in the

phenology of age/sex classes of tree frogs captured in the macro-habitat study is indicated in the

overall phenology (refer to Section 2.3.1).

59

Figure 4.2 The abundances of the age classes from the fixed transects over the 12-month

period, graphed against average rainfall (mm) and air temperatures (�C) on the

sampling nights.

0

10

20

30

Tota

l num

ber o

f fro

gs

0

10

20

30

40

50

Tota

l num

ber o

f fro

gs

0

10

20

30

40

50

60

Tota

l num

ber o

f fro

gs

0

20

40

60

80

100

120

Sep-04

Oct-04

Nov-04

Dec-04

Jan-05

Feb-05

Mar-05

Apr-05

May-05

Jun-05

Jul-05 Aug-05

Month

Ave

rage

rain

fall

(mm

)

0

5

10

15

20

25

30 Average air tem

perature (C)

RainfallAir temp

Adults

Juveniles

Metamorphs

60

Figure 4.3 Abundance of gravid females captured along the both land and stream transects

over the 12-month survey period, graphed against average rainfall (mm) of the

sampling days.

0.0

20.0

40.0

60.0

80.0

100.0

120.0A

vera

ge ra

infa

ll (m

m)

0

2

4

6

8

Sep-04 Oct-04 Nov-04 Dec-04 Jan-05 Feb-05 Mar-05 Apr-05 May-05 Jun-05 Jul-05 Aug-05

Month

Num

ber o

f gra

vid

fem

ales

cap

ture

d

61

y = -0.39x + 1.56R2 = 0.64

0.50

0.70

0.90

1.10

1.30

1.50

1.70

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00

Log of average rainfall (mm) of sampling nights

Log

of fr

og a

bund

ance

Figure 4.4 The significant correlation (t2, 21= -3.39, p= 0.003) between log-transformed

abundances of adult P. vitiensis graphed against log-transformed average rainfall

of sampling nights (mm) in each month. The equation of the regression line and

the regression coefficient are shown within the graph.

62

y = -0.31x + 1.36R2 = 0.30

0.50

0.70

0.90

1.10

1.30

1.50

1.70

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00

Log of average rainfall (mm) of sampling nights

Log

of fr

og a

bund

ance

Figure 4.5 The significant correlation (t2, 21= -2.06, p= 0.05) between log-transformed

average rainfall (mm) and log-transformed abundances of metamorph Fiji tree

frogs. The equation of the regression line and the regression coefficient are shown

within the graph.

63

y = 0.07x - 1.18R2 = 0.37

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

19 20 21 22 23 24 25 26 27

Log of average air temperatures (°C) of sampling nights

Log

of fr

og a

bund

ance

Figure 4.6 The significant correlation (t2, 21= 2.06, p= 0.05) between average temperatures

(�C) and log-transformed abundances of gravid female tree frogs. The equation of

the regression line and the regression coefficient are shown within the graph.

64

y = -0.26x + 0.63R2 = 0.15

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00

Log-transformed average rainfall (mm) of the sampling nights

Log

abun

danc

e of

frog

s

Figure 4.7 The significant correlation (t2, 33= -2.65, p= 0.01) between log-transformed

average rainfall (mm) and log-transformed abundances of adult Fiji tree frogs

from the habitat study. The equation of the regression line and the regression

coefficient are shown within the graph.

65

Figure 4.8 Abundance of adult Fiji tree frogs captured in the habitat study over the 12-month

survey period, graphed against average rainfall (mm) of the sampling days.

0

2

4

6

8

10

12

14

16

Jun-04 Jul-04 Aug-04 Sep-04 Oct-04 Nov-04 Dec-04 Jan-05 Feb-05 Mar-05 Apr-05 May-05

Month

Tota

l fro

g ab

unda

nce

per m

onth

0.00

5.00

10.00

15.00

20.00

25.00

Jun-04 Jul-04 Aug-04 Sep-04 Oct-04 Nov-04 Dec-04 Jan-05 Feb-05 Mar-05 Apr-05 May-05

Month

Avg

. rai

nfal

l (m

m) p

er m

onth

66

4.4 DISCUSSION

Air temperature did not influence the annual activity patterns of all adult frogs, a pattern

indicated by previous studies on tropical rainforest anurans (Magnusson et al., 1999). Air

temperature influences calling activity as temperature can affect the vocal capabilities of

anurans, and is thought to indirectly influence streamside abundance (Zweifel, 1959; Giacoma et

al., 1997; Luddecke and Sanchez, 2002). However, gravid female Fiji tree frogs were positively

correlated to air temperature on the sampling night, indicating increased breeding activity during

the early wet season months as nocturnal air temperatures rise (November to January).

Smith (1996) demonstrated that the effect of air temperatures on reproductive activity is weaker

than the influence of annual rainfall patterns on a tropical rainforest frog, Littorea xanthomera, in

Australia. Much of the literature suggests that rainfall is the most important meteorological

variable determining intra-annual fluctuations in adult male and female frog activity (Heyer,

1973; Ryan, 1983; Aichinger, 1987; Donnelly and Guyer, 1994; Magnusson et al., 1999). Adult

tree frog activity is significantly negatively correlated with higher rainfall, and more adult frogs

were captured during the dry season months (May – October). The increase in adult activity

during the dry season might be a result of an increase in food availability during this time, which

has been shown in other tropical studies (Moreira and Lima, 1991; Watling and Donnelly, 2002).

The abundance of metamorphs/hatchlings also fluctuated with rainfall, a trend that may represent

decreased activity during short-term high rainfall. The survey team observed fewer

metamorphs/hatchlings on sampling nights when rainfall during the 24-hour period was higher

than on other nights. The correlation between metamorph/hatchling abundance and rainfall may

also be a function of decreased detectability of Fiji tree frogs due to poor visibility in the rain.

67

The abundance of gravid females was observed to have increased during the wet season. Similar

results were found in a study on coqui frogs (Eleutherodactylus spp.) in South America, where

gravid females were mainly found during the wet season (Aichinger, 1987). Reproductive

activity in P. vitiensis along Vago Creek appeared to drop in the drier months, as no gravid

females were captured during April to July.

Juvenile recruitment of the Vago population peaked during the wet season (November to

January), a trend that contrasts with the results from tropical anuran populations in the upper

Amazon where juvenile numbers peaked during the dry season (Aichinger, 1987). The increase

in juvenile tree frog numbers during the wet season may possibly be due to upstream or

downstream immigration of juveniles into the transect site. Increased juvenile recruitment in the

wet season occurs in several anuran species in the Amazon (Moreira and Lima, 1991). The

increased abundance of juveniles during the early dry season (November-January) may reflect

seasonal reproduction in the Fiji tree frog, which ensures new recruits enter populations in the

early wet season when there may be a secondary peak in food items (Galatti, 1992; Hodgkison

and Hero, 2003).

There were no clear indications of phenology in the broad-scale survey data, as suggested

previously in Chapter 2. The significantly negative effect of rainfall on sampling was again

confirmed, and it is suggested that changes in adult numbers over the year in the habitat study

were due to the influence of this meteorological variable on detectability and/or frog activity.

Other environmental factors like relative humidity, moon phase, and wind/ air desiccation were

noted but not tested during this study. These factors have been shown to be influential on

68

amphibian reproductive activity (Cree, 1989; Oseen and Wassersug, 2002). Testing the effect of

these weather variables would enable us to better understand the reproductive phenology of the

Fiji tree frog. However, any further studies on the influence of environmental variables will

need to take into account that both sexes call, and should compare differences between responses

to changes in meteorological variables by male and female frogs (Stewart and Rand, 1991).

Fiji tree frogs are thought to be year-round breeders (Morrison, 2003). Breeding occurs during

both the dry season months of May to October, as well as the wet season months of April to

November, although at lower rate during the dry season. However, the onset and duration of

seasons may differ between years (Alexander and Eischeid, 2001). Consequently, the phenology

patterns of anurans in tropical wet-dry climes will vary from year to year. In addition, not all

the females of reproductive age in any given population may breed every year (Gill, 1985).

Thus, the results of short-term studies of phenological activity of amphibians are ‘snap-shots’ of

a much broader picture.

To gain a better understanding of P. vitiensis’s breeding, further monitoring of the Vago Creek

population would be required over many years to provide a more comprehensive outline of

cyclical changes in annual breeding patterns. The results of this study are the first systematically

collated and analysed population data for P. vitiensis, from a fixed site that was surveyed

monthly for 12 months. The patterns shown by the Vago Creek population are likely to be

representative of tree frog populations in Savura, and possibly elsewhere in their range.

Research into tree frog populations in other sites in the Fiji group is necessary to determine just

how representative is the phenology of the study population.

69

4.5 SUMMARY

The phenology of the Vago Creek population showed complex patterns that may be due to inter-

annual fluctuations in weather, as well as other factors, such as migration and recruitment, which

were not investigated in this study. The abundance of all adult frogs was greatest during the dry

season months (May-June), possibly due to a significantly negative relationship with rainfall.

Greater activity of gravid females during the wet season indicates that egg-laying occurs during

November to February. Juvenile tree frog phenology contrasted with that of metamorphs, as

metamorphs were captured more often during the dry season whereas juvenile abundances were

higher in the wet season. The phenology of tree frogs in the macro-habitat survey was indistinct,

and fluctuations in recorded adult abundances over the sampling period were associated strongly

with changes in rainfall rather than an indication of frog phenology.

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Chapter 5 Conclusions and Recommendations for Future Research

5.1 THE SAVURA TREE FROG POPULATION

Fiji tree frogs in Savura are distributed throughout the area, in both primary and secondary

lowland rainforest of the Vago and Savura forestry reserves, as well as in the mahogany

plantations of Colo-i-Suva. Although sub-populations are more common and larger (Section

2.3) in primary rainforest sites, P. vitiensis is quite capable of inhabiting scrub vegetation, in

addition to secondary disturbed and cultivated forests. The structure and composition of suitable

habitat sites are key factors in determining the presence or absence of tree frogs. However,

unknown past distribution patterns may also affect current patterns. In addition to habitat

preferences, tree frogs appear to select specific microhabitats for foraging and perch sites, as

frogs were more active along the riparian strip than within the adjacent forest (Section 3.3.3).

These factors are essential information when designing sampling programmes for future

monitoring of the species.

5.1.1 Major Habitat Preferences

Tree frogs were slightly significantly more abundant in primary lowland rainforest sites than in

secondary disturbed lowland rainforest or cultivated mahogany forests. This confirms that P.

vitiensis populations are more common in well-forested and generally undisturbed sites (Ryan,

1984; Morrison, 2004). However, when taking into account the connectivity of the habitats

surveyed and the low human disturbance levels throughout much of the Savura area, relative to

adjacent areas, this pattern is not as unlikely as it first seemed. Disturbance due to human

activity is limited to areas accessible by the dirt road and tracks leading off it.

71

The largest populations of frogs were found in sites with very low levels of human and natural

disturbance, dense forest canopies, and an abundance of microhabitats where tree frogs were

encountered during the study (i.e. riparian Pandanus spp. stands). In addition, rainfall variability

greatly influenced the frog counts in the different habitats. These confounding variables need to

be examined more thoroughly to determine their significance in assessing habitat suitability for

P. vitiensis.

5.1.2 Microhabitat Selection

Platymantids have been a part of Fiji’s biota for at least five millennia (Worthy, 2001) and may

have been historically more diverse. It is possible that Fiji’s frogs have evolved associations

with certain plant taxa during this period of co-habitation in the lowland rainforests of the main

islands, as they were more often found on riparian species present in primary and secondary

rainforest, then in mahogany plantations. The long leaves of Pandanus vitiensis were the most

common perch and foraging sites of individuals captured. Other species used as nocturnal

microhabitats were Dolicholobium sp., Dilenia biflora, Syzygium seemannii, and Ficus

bambusifolia.

The majority of captured individuals were found between one and three metres above the ground

on shrubs and tree saplings. Perch sites at these heights render individuals vulnerable to

predation by the introduced mongoose (Herpestes javanicus) and rats (Rattus spp.). Although

there must exist a trade-off between increased visibility to predators and greater feeding

opportunities along streams, P. vitiensis were more abundant along Vago Creek than in the

adjacent rainforest strip, which may be due to a greater abundance of flying insects in open

riparian zones than under the closed canopies of primary rainforest (Olson, pers. comm., 2002).

72

As microhabitats occupied within the major habitat surveys were also significant with respect to

the vegetation of the perch site, proximity to stream, and height above ground, P. vitiensis

displays selectivity for nocturnal foraging and perch sites.

5.1.3 Phenological Information

The phenology of the Vago Creek population showed complex patterns that may not be

representative of annual trends. Records of egg clutches found suggest that P. vitiensis females

lay eggs primarily between November and February, supporting the findings from previous non-

systematic studies. Adult tree frogs were generally more abundant during the dry season

months; however gravid females are more abundant in the wet season. Juvenile recruitment

peaked during the early months of the wet season and metamorphs/hatchlings were more

abundant during the dry season, which may reflect increased breeding activity during the latter

part of the wet season. Temporal variation in abundance during the 12-month period is likely

due to relationships between age classes and meteorological variables, particularly short-term

rainfall events.

5.2 RECCOMENDATIONS FOR FUTURE SURVEYS

From the results of the habitat, microhabitat and phenological analysis, several recommendations

can be made for future surveys of P. vitiensis populations on Viti Levu. These recommendations

may also be applicable for other populations of tree frogs on the islands of Vanua Levu, Tavueni,

Gau, and Ovalau. Several of the recommendations may be extended to the tree frog’s

endangered congener, P. vitianus. Recommendations are subdivided into temporal and spatial

categories.

73

5.2.1 Temporal Variables

As rainfall was the most influential weather variable determining the abundances of tree frogs,

surveys should take into account inter-annual fluctuation in rainfall in Fiji. The distribution of

rainfall over the last five years (September 2000-August 2005) was homogenous (Levene's

statistic= 0.18, p= 0.95; d.f= 4, 55), and rainfall during the study period did not vary

significantly from patterns shown for the last four years (F4, 55= 0.68, p= 0.61; Appendix 3.1b).

The abundance of tree frogs captured showed a bi-modal distribution throughout the 12-month

survey. The first peak occurred between October to December, and the second between May to

July. The first peak in abundance was attributed to greater abundances of juveniles and adult

females. The latter peak occurred during the dry season and is due to an increase in metamorph

abundance. The results of this study suggest that the age and size classes of tree frogs display

differences in temporal patterns of activity. Accordingly, future surveys should clearly separate

the data for these size classes. Overall, Fiji tree frogs were most abundant during the late wet

season to mid-dry season (March-July).

In order to get an estimate of total population size in time-constrained surveys, the best period

during the year to survey the frog population would be between the late wet season and early dry

season. As the onset of these seasons can fluctuate between years, long-term climatic patterns

should be considered when selecting dates to survey Fiji tree frogs. However, if a specific subset

of the population is the focus of surveys, then the temporal pattern in activity will need to be

considered. Adult and juvenile tree frogs are best surveyed during the early wet season, whereas

metamorph activity is best surveyed during the dry season. Likewise, inter-annual fluctuations

74

in the onset and duration of the two seasons in Fiji need to be accounted for in the sampling

design.

Short-term fluctuations in weather may further influence results of sampling. Heavy rainfall in

the 24-hour period prior to sampling may result in a low number of captures, as the smaller sized

individuals are less likely to venture out to forage. Heavy rainfall on the sampling night can

affect visibility as well as deter tree frogs from occupying more exposed microhabitats. The

intensity of short-term rainfall events may be more important than the total amount of rainfall in

the period leading up to sampling. Inter-annual fluctuation in temperature in the tropical

rainforests of Fiji did not influence the survey results as much as rainfall variability. However,

juvenile and gravid female frogs were more active during the warmer months. It is suggested

that sampling will not be as efficient when low nocturnal temperatures coincide with long

periods of dry weather.

5.2.2 Spatial Variables

As the results of this study do not suggest tree frogs exhibit site selectivity determined by general

vegetation formation characteristics, surveys of Fiji’s platymantids may not necessarily be

restricted to good rainforest. Cultivated forestry reserves, such as the Colo-i-Suva mahogany

forests, that have low levels of human disturbance and riparian strips are potential sites for tree

frog surveys. Tree frogs were found in Colo-i-Suva along narrow streams, under mahogany

canopies as close as 30 m to Forestry staff quarters. Several individuals were discovered in quite

exposed perch sites on grass and shrubbery in disturbed vegetation. However, the bulk of

captured individuals were reported from primary lowland rainforests sites, and therefore, primary

75

rainforest is the most suitable habitat for long-term monitoring of demographic variables in P.

vitiensis populations.

The protected status of the sites surveyed is another important variable to consider in the habitat

selectivity of tree frogs. All the sites surveyed were within the boundaries of forest reserves, and

are subjected to lower levels of human disturbance. As a consequence tree frog populations may

be more likely to occur in less primary habitat, within these reserves, than non-protected

secondary habitats elsewhere in Fiji.

Since tree frogs used specific microhabitat selection throughout the Savura area, it is likely that

the species does this elsewhere in its distributional range. The Savura tree frogs were mostly

found on endemic Pandanus and Dolicholobium species, and ground ferns of various species

along streams and in adjacent forests. The leaves and sheathed petioles may protect P. vitiensis

from being dislodged into streams during heavy rainfall. During drier weather, dew and rainfall

is retained in the axils of Pandanus leaves and sheathed petioles of Dolicholobium leaves. Tree

frogs may also select these plants as substrates for foraging and calling activity to reduce the

possibility of desiccation during the dry season.

From these findings, it is recommended that researchers focus sampling efforts on these

microhabitats when projects are restricted by time. Intensive short-term surveys are often “hit-

and-miss” sampling efforts when the area being searched is extensive and heterogeneous (such

as the distributional range of platymantids in the Fiji archipelago). Knowing where to look cuts

down time spent at sites, and factors such as vegetation present can be used as selection criteria

when choosing sites for sampling.

76

5.2.3 Other Factors to Consider

One the major problems encountered in the field was the sexing of individuals greater than three

grams in body weight. The literature suggests that adult males and females are distinguishable

based on several criteria (Gorham, 1971; Pernetta and Goldman, 1977; Ryan, 1984; Morrison,

2003). These include:

1. Adult males are reproductively mature at smaller sizes (between 1.5-

2.0g) than females and exhibit a yellow groin flash that extends from

the groin along the inner thigh to the knee joint.

2. Adult females generally grow much larger than adult males (up to

60mm in SUL, and will, therefore, reproductively mature at a larger

size than males and will not display the yellow groin flash seen at such

small SUL’s as adult males.

3. Adult females over 35mm in SUL are capable of developing ova and

becoming gravid, a condition that is clearly visible through the

transparent skin of the abdomen.

However, it became quite clear during sampling that these criteria do not guarantee accurate

identification in the field. Individuals over 1.5g in body weight and greater than 30mm in SUL

were easier to classify as adult males, as these frogs displayed yellow groin flashes. The sexing

of individuals weighing 3-5g and measuring 35-45mm in SUL was confounded by the fact that

all tree frogs captured greater than 1.5g and 30mm in SUL, displayed the yellow groin flash. In

addition males of Fiji congeners do not have nuptial pads, which many other anurans possess

(Zug, 1993; Beebee, 1996; Morrison, 2003; Kuruyawa et al., 2004). Furthermore, both sexes

77

have similar sounding calls and could not be identified by their calls in the field. This meant that

immature females below 4g and 32mm in SUL could not be same sized males in the field.

5.3 IMPLICATIONS FOR CONSERVATION OF FROGS IN FIJI

Fiji’s tree frogs are generally classified as rainforest frogs even though they are also found in

secondary vegetation. A close association with riparian and rainforest plant species, such as

Pandanus and Dolicholobium has been noted elsewhere throughout their range (Gorham, 1968

and 1971; Ryan, 1984; Morrison, 2003; Naikatini, Osborne, and Morley, In prep.). Degradation

of primary lowland rainforest and pristine watersheds in time may result in the loss of available

habitat with suitable microhabitats for the tree frog. P. vitiensis could therefore, be used as an

umbrella species to help protect areas of primary lowland rainforest where tree frogs are extant

throughout its range.

P. vitiensis is considered ‘near threatened’ and is currently on the IUCN Red List (IUCN,

Conservation International, NatureServe, 2004). However, there have been no recent censuses

throughout the tree frog’s range to determine its actual status. Thus, there is a need to conduct

surveys on the islands where the frog has been reported, to determine the affects of changes to

the extent of primary rainforest on these populations. The arboreal habit of the tree frog is

presumed to be one of the main reasons that the P. vitiensis has persisted on the main islands of

Fiji whereas the ground frog appears to have been extirpated from mainland Viti Levu (Watling

and Zug, 1998). The apparent extirpation of the ground frog on Viti Levu has been linked to the

introduction of the small Indian mongoose, Herpestes javanicus (ibid.).

78

It is assumed that the ground dwelling nature of the ground frog rendered it more vulnerable to

predation by mongoose on Viti Levu and Vanua Levu (Pernetta and Watling, 1978; Watling and

Zug, 1998; Morrison et al., 2004). However, mongoose predation may not be the only factor

that contributed to the extirpation of the ground frog on Viti Levu (Pernetta and Watling, 1987).

Climate change over the last 10,000 years may have reduced primary lowland rainforest

coverage in Viti Levu (Nunn, 1997). The loss of suitable habitat (Gorham, 1968) in addition to

human predation (Worthy, 2001) is likely to have caused extirpations of platymantid populations

in what is now termed the ‘dry zone’ of Viti Levu. Several populations may have become so

small that demographic and stochastic events wiped these relict populations out.

Although ground frogs were recorded in parts of Viti Levu (Nasoqo, near Suva) there may have

only been a few relict populations that persisted at the time of European exploration (Gorham,

1968). Gorham’s (1968) revision of museum specimens suggests that the majority of specimens

labelled as taken from Viti Levu, were probably from Ovalau Island.

Future research into pre-historic vegetation patterns on Viti Levu Island, taking into account both

climatic-induced changes and the affects of early human settlement, may help to understand the

pre-history of Fiji’s platymantids. Geographical Information Systems’ (GIS) software (Carey et

al., 2001) and genetic analysis (Faith et al., 2004) are likely to be the best tools to apply to

elucidating pre-historic changes in distribution and abundance of the tree frog. By determining

probable causes of decline in populations of Fiji’s frogs before the introduction of the mongoose,

we may understand current distributional patterns more clearly.

Understanding the distribution of Fiji’s platymantids is essential to the development of efficient

conservation programmes. Long-term and short-term changes to population size are vital factors

79

to consider when designing conservation projects (Biek et al., 2002). Conservation of both

Platymantis species is needed as they are endemic to Fiji and represent an important branch of

the genus and the generic genome.

5.4 SUMMARY

As Platymantis vitiensis populations in Savura show slight habitat preferences, it is

recommended that future surveys should not be constricted to primary lowland rainforest but

should encompass secondary vegetation with moderate levels of human disturbance. Surveys

that are time constricted may increase efficiency by sub-sampling along riparian strips in

forested areas, focusing on species such as Pandanus and Dolicholobium and ground ferns. In

order to obtain more accurate estimates of adult population size, it is recommended that sampling

be carried out between the late wet season to early dry season (approximately March to July).

Future research on Viti Levu to map extant tree frog populations and to clarify the agents causing

the extirpation of tree and ground frogs is necessary for conservation purposes. In addition, it is

suggested that past distributional patterns and the probable causes for the reduction in range of

both species be investigated to allow for greater understanding of the extirpation events and

enable development of more efficient conservation programmes for Fiji’s Platymantis.

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80

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Appendices

92

Appendices

APPENDIX I

Appendix 1.1 Map Co-ordinates for Sampling Sites in Habitat Surveys.

GPS co-ordinates for each site surveyed for the macro-habitat study. Map co-ordinates are

based on the WGS82 Global Positioning System.

Habitat Type Site Longitude Latitude Primary lowland rainforest P1 18º 04’ 39.45” S 178º 26’ 20.58” E P2 18º 04’ 53.29” S 178º 26’ 41.95” E P3 18º 04’ 47.54” S 178º 26’ 41.50” E P4 18º 05’ 01.20” S 178º 26’ 33.72” E P5 18º 05’ 01.72” S 178º 26’ 44.59” E P6 18º 05’ 10.29” S 178º 26’ 32.66” E P7 18º 03’ 56.96” S 178º 26’ 48.32” E P8 18º 02’54.89” S 178º 26’ 37.74” E P9 18º 03’ 39.72” S 178º 26’ 49.36” E P10 18º 04’ 23.99” S 178º 26’ 54.52” E P11 18º 04’ 19.66” S 178º 26’ 58.63” E P12 18º 04’ 37.75” S 178º 26’ 24.01” E Disturbed secondary D1 18º 03’01.17” S 178º 26’ 30.87” E lowland rainforest D2 18º 03’ 02.15” S 178º 26’ 24.02” E D3 18º 03’ 56.96” S 178º 26’ 48.32” E D4 18º 04’ 58. 32” S 178º 26’ 36.02” E D5 18º 03’ 01. 03” S 178º 26’ 39.45” E D6 18º 02’ 58. 32” S 178º 26’ 30.87” E D7 18º 03’ 00. 34” S 178º 26’ 01.72” E D8 18º 04’ 04.15” S 178º 26’ 49.91” E D9 18º 04’ 56.53” S 178º 26’ 34.32” E D10 18º 04’ 01.92” S 178º 26’ 48.25” E D11 18º 03’ 06. 72” S 178º 26’ 36.06” E D12 18º 05’ 02.54” S 178º 26’ 31.41” E Mahogany plantation M1 18º 03’ 49.74” S 178º 27’ 19.73” E M2 18º 03’ 47.17” S 178º 27’ 20.24” E M3 18º 03’ 51.45” S 178º 27’ 2058” E M4 18º 03’ 02.57” S 178º 27’ 22.29” E M5 18º 03’ 13.72” S 178º 27’ 24. 01” E M6 18º 03’ 03.43” S 178º 27’ 0.87” E M7 18º 03’ 45.45” S 178º 27’ 02.58” E M8 18º 03’ 33.02” S 178º 27’ 16.10” E M9 18º 03’ 37.29” S 178º 27’ 25.56” E

Appendices

93

Appendix 1.1 Continued

Habitat Type Site Longitude Latitude Mahogany plantation M10 18º 03’ 35.58” S 178º 27’ 15.70” E M11 18º 03’ 31.51” S 178º 27’ 23.02” E M12 18º 03’ 56.60” S 178º 27’ 10.29” E

Appendices

94

APPENDIX II

Appendix 2.1 Plant Species used as Substrates by Captured Frogs.

List of plant species used by captured frogs as substrates for perch sites or microhabitats.

Scientific Name Common Name Local Name Acalypha rivularis --- Kadakada Acrostichum aureum --- Vativati Agathis macrophylla --- Dakua Aglaia elegans --- Kaunitoa Alatostema spp. --- Beta Alocasia indica Swamp aroid Via gaga Alyxia spp. --- Vono Angiopteris erecta --- --- Asplenium amboinense Terrestrial fern --- Asplenium nidus Birds nest fern Beluve Astronidium spp. --- Dava Balaka spp. Balaka palm Balaka Barringtonia edulis --- Vutu Blechnum sp. Terrestrial fern --- Callophylum vitiense --- Damanu Canarium sp. --- Kaunigai Clidemia hirta Koster's curse Drau ni siga Collospermum montanum --- Misimisi Cordyline terminalia --- Vasili Culcitta straminea Terrestrial fern Ai vuti Cyathea spp. Tree fern Balabala Cynometra insularis --- Moivi, cibicibi Derris elliptica Derris Duva ni niukini Dilenia biflora --- Kuluva Dolicholobium sp. --- Soso ni ura Dysoxylum richii --- Tarawau kei rakakaEndiandra sp. --- Dirinui Epipremnum pinnatum Tonga plant Yalu Ficus bambusifolia --- Loselose ni wai Ficus spp. Fig trees Baka Freycinetia spp. --- Wa me Garcinia myritifolia --- Laubu Geniostoma vitiense --- Boiboida levu

Appendices

95

Scientific Name Common Name Local Name Geodorum pictum Ground orchid Vavara Gironniera celtidifolia --- Sisisi Gonystylus punctatus --- Mavota Gymnostoma vitiense --- Velau Hedychium spp. Ginger --- Inocarpus fagifer Tahitian chestnut Ivi Macropipersp. --- Yaqoyaqona Marattia smithii --- Dibi Melastoma denticulatum --- Kaunisiga Miscanthus floridus Reed Gasau Musa sp. Banana Jaina Myrsitica spp. --- Kaudamu Nuerbergia corynocarpa --- Bo Palaqium spp. --- Bau Pandanus spp. Pandanus Vadra Plerandra sp. --- Sole Pometia pinnata --- Dawa Psychotria spp. --- Degedege Schizostachyum glaucifolium Native Fiji bamboo Bitu dina Syzygium seemannii --- Yasi ni wai Tapeinosperma clavatum --- Dasia Tectaria spp. Terrestrial fern --- Timonius affinis --- Tiri-ni-vanua Vavaea sp. --- Cevua --- Kitione

Appendices

96

APPENDIX III

Appendix 3.1 Monthly rainfall variability over the last five years.

a) Monthly rainfall recorded at the Fiji Meteorological Services Laucala Bay station from

September 2000 – August 2005

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

SeptemberOctoberNovemberDecemberJanuary February March April May June July August

Month2004-2005Mean (2000-2004)

Rai

nfal

l per

mon

th (m

m)

Appendices

97

b) Results of ANOVA on monthly rainfall from September 2000 – August 2005 to determine how

representative was monthly rainfall during the study period (September 2004- August 2005).

Sum of Squares df Mean Square F Significance Between Groups 5112456.93 4 1278114.23 0.68 0.61

Within Groups 103266073.67 55 1877564.98

Total 108378530.6 59