Floodplain amphibian abundance: responses to floodingand habitat type in Barmah Forest, Murray River, Australia

Heather M. McGinnessA,E, Anthony D. ArthurA,D, Keith A. WardB and Paula A. WardC

ACSIRO Ecosystem Sciences, GPO Box 1700, Canberra City, ACT 2601, Australia.BGoulburn-Broken Catchment Management Authority, PO Box 1752, Shepparton, Vic. 3632, Australia.CPrivate consultant, 4 Eyre Court, Kialla, Vic. 3631, Australia.DPresent address: Australian Bureau of Agricultural and Resource Economics and Sciences,Department of Agriculture, Fisheries and Forestry, GPO Box 1563, Canberra, ACT 2601, Australia.

ECorresponding author. Email: Heather.McGinness@csiro.au

AbstractContext. Frog species are now targets for delivery of high-value managed environmental flows on floodplains.

Information on the drivers of frog presence and abundance is required to support adaptive management, includinganalysis of the roles of flood frequency, flood timing and habitat type.

Aims. This paper describes frog species richness and abundance responses to flooding and habitat type in the BarmahForest, part of the largest river red gum forest in the world.

Methods. Surveys were conducted at 22 sites over 6 years, to determine species presence, relative abundance, andevidence of breeding. Data were then used to examine temporal patterns within and between wet and dry years and spatialrelationships with site geomorphology, vegetation form and wetting frequency.

Key results. Six species were common and widespread, and three were rare. The seasonal timing of peak numbers ofcallingmales differedamongspecies.The seasonal patternof calling for each species didnot differ betweenwet anddryyears;however, significantly lower numbers of frogs were recorded calling in dry years. The number of frogs calling wassignificantly higher in well vegetated grassy wetlands. Evidence of a positive relationship between wetting frequencyand numbers of calling males was found for Limnodynastes fletcheri, Crinia signifera and Limnodynastes dumerilii. Theabundance of tadpoles was significantly higher in wet years.

Conclusions. The seasonal timing of flooding in Barmah Forest will influence the breeding success of individual specieswith different preferences. Flooding from September to December is required to cover most preferred breeding seasons, butlonger durations may be required to maximise recruitment. This, together with regular flooding of well vegetated grassywetland habitat, will increase the likelihood of species persistence and maximise diversity. Insufficient flooding frequencywill result in reduced frog species richness and abundance.

Implications.Managed flooding is important for frog abundance and species richness. This study emphasises the valueof key habitats such as well vegetated grassy wetlands and reinforces the need to make their preservation a priority formanagement. It has identified knowledge gaps to drive future data collection for improved modelling, including a need forfurther research on flow-regime change and frog communities.

Additional keywords: Barmah–Millewa Forest, environmental flows, flow regulation, frogs.

Received 4 February 2013, accepted 17 June 2014, published online 10 July 2014

Introduction

Floodplain river landscapes are important for frogs because theyunite a variety of terrestrial, lotic and lentic habitats on whichfrogs depend (Healey et al. 1997; Tockner et al. 2006; Wassensand Maher 2011). They support frog species that have the abilityto exploit flooding when it occurs and survive the dry intervalsbetweenflood events (Healey et al. 1997;Wassens 2010). In turn,frogs are essential components of floodplain ecosystems. Frogsand their tadpoles consume invertebrates, algae, periphyton anddetritus (Pengilley 1971; Emerson 1985; Gillespie 2002), and are

an important food source for other floodplain fauna, includingiconic birds, reptiles and amphibious mammals (Carrick1959; Shine 1977; Woollard et al. 1978; Richardson et al.2001). Recently, frogs have become a group of internationalconservation concern, with documented population declinesand species losses worldwide (Campbell 1999; Hero andMorrison 2004; Murray and Hose 2005). In floodplain riverlandscapes of Australia, frogs are now of particular interestas response indicators and targets for environmental flowmanagement (Wassens 2010; Wassens and Maher 2011).

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However, information on frog species presence and abundanceis required to support adaptive management, including analysisof the roles of flood frequency, flood timing and habitat type.

Flooding directly influences the range and quality of habitatsavailable to frog populations and metapopulations in thelandscape (Wassens 2010). Frog breeding is influenced by arange of flood characteristics, including seasonality, frequency,duration (hydroperiod), and water temperature and water quality(Morand and Joly 1995; Richter and Azous 1995; Parris andMcCarthy 1999; Reid and Brooks 2000; Tockner et al. 2006).In particular, fluctuations in water depth and permanency canaffect frog breeding success in different ways, depending onspecies’ egg-laying technique and the rate of tadpoledevelopment. Insufficient depth and duration of flooding canexpose eggs and young frogs to predation and desiccationand prevent completion of metamorphosis (Anstis 2002;Hazell 2003). The time required to complete metamorphosiscan vary greatly (Anstis 2002) – species that takeseveral months to develop need extended flooding for theirpopulations to persist, whereas species that develop quicklycan take advantage of rain events and will be more likely toremain in areas with reduced flooding frequency and duration.Flood regime may also affect predation of eggs and tadpolesby fish – especially fish species that can exploit the shallow,ephemeral nature of many frog breeding habitats (Healey et al.1997; Hartel et al. 2007; Wassens and Maher 2011).

Frog species have different habitat preferences that arestrongly linked to the effects of geomorphology onhydroperiod and vegetation characteristics, especiallyvegetation type, diversity and density (Healey et al. 1997;Parris and McCarthy 1999; Wassens et al. 2010). Thepresence, absence or complexity of particular vegetation typescan be a primary driver of differences in adult frog distribution,abundance, species richness and assemblage compositionin different wetlands (Hartel et al. 2007; Healey et al. 1997;Hazell et al. 2001;Wassens et al. 2010). For example, complexityof aquatic and fringing vegetation is a key predictor ofhabitat occupancy of the endangered southern bell frog(Litoria raniformis) across inland New South Wales (Wassenset al. 2010). Similarly, species composition of forest frogassemblages in south-eastern Queensland, Australia, issignificantly correlated with species composition ofunderstorey vegetation in the riparian zone and the presence ofpalms (Parris and McCarthy 1999). Because geomorphologyand vegetation type within floodplains are related to flowregime and flow history, if the vegetation preferences ofAustralian frog species were conclusively known, observed orpredicted vegetation change as a consequence of flow-regimechange may serve as a useful factor in modelling change in frogcommunities.

Themales of different frog species are distinguishable by theirspecies-specific advertisement calls during the breeding season.The timing and number of these calls are often used to evaluateand compare species presence and abundance at individual sites.It is generally accepted that calling is positively correlated withbreeding effort, because of the energetic costs and increased riskofmortality during calling – although breeding can occurwithoutcalling, and vice versa (Brook 1980; Lemckert and Mahony2008). Factors affecting calling activity other than flooding in

Australia include temperature, rainfall and local environmentalconditions (Lemckert and Mahony 2008). Although many frogfield guides in Australia describe seasonal calling patterns orpreferences of individual species, very few data have beenpublished in the scientific literature describing calling patternsin the key breeding months over several years in one area. Suchdata are of interest because they may be used by managers toinform the timing and duration of environmental flows, and anychanges in the timing of calling for each species may indicateother environmental or climatic changes.

The core calling season for most floodplain species ofsouth-eastern Australia is September to February (Lemckertand Mahony 2008). However, there is variation among speciesin terms of when calling may begin or end, and some species aremore opportunistic and responsive to short-term rain or floodevents than are others (Brook 1980; Littlejohn 1987; Lemckertand Mahony 2008). For example, Crinia signifera is known tocall in relatively large numbers in all months of the year,provided conditions are suitable (Brook 1980; Littlejohn 1987;Lemckert and Mahony 2008). The timing of breeding defineswhich competitors and predators are likely to be present andwhether the hydroperiod will be sufficient for completion ofmetamorphosis and survival. Species that respond rapidly toinundation may gain an advantage for their tadpoles from theflush of primary productivity that arises from the high levels ofallochthonous nutrients available following flooding (Petersonand Boulton 1999; Anstis 2002). Their tadpoles may also gain asize advantage in competitionwith other species, fish and insects,as well as in terms of their availability to predators and theiryoung. Disadvantages include the risk of slower growth in coldertemperatures and increased exposure to predators because ofshallow depths and longer development periods (Peterson andBoulton 1999; Anstis 2002).

Because frogs in floodplain river ecosystems rely to a greatextent on habitats created by flooding for breeding, and are oftenless mobile than are other vertebrate fauna groups such as birdsand mammals, modelling the links between frog communitiesand flood-related factors is an attractive prospect. In thiscontext, site-specific monitoring information remains essentialfor effective modelling and prediction of responses withinindividual floodplains to management actions such asenvironmental flows. Beginning in the year 2000, managersof the Ramsar-listed Barmah–Millewa Forest added frogs tothe monitoring programs being established in the forest onwaterbirds, forest birds and fish (Maunsell-McIntyre 2000;Bren 2001). Species and numbers of frogs heard calling inBarmah–Millewa Forest fluctuated over time, and possibleexplanations have been reported (Ward 2000–2006), however,no quantitative analysis of the data has previously been conductedto explore or verify links with hydrology or site characteristics.The present paper uses data collected as part of this monitoringprogram over the years 2000–2006, to model floodplain frogspecies richness and abundance associations with flooding andhabitat type. It examines (1) temporal trends in the number offrog species calling and the total number of frogs of individualspecies calling; (2) spatial patterns in the number of frog speciescalling and the total number of frogs of individual speciescalling in association with site commence-to-flow threshold,wetting frequency, geomorphic unit, vegetation form, wetland

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level (primary–secondary or high–low) and water managementarea; and (3) evidence of reproduction over time.

Study area

The Barmah–Millewa Forest is the largest river red gumfloodplain forest in the world, spanning an area of over60 000 ha, straddling the Murray River and the state border ofVictoria andNewSouthWales (NSW) in south-easternAustralia.Barmah is in Victoria, and Millewa is in NSW. The forest isflooded when Murray River flows at the Barmah Choke exceedthe channel capacity of 10 500MLday–1. Flooding naturallyoccurred about once every 2–10 years, in winter or spring, andranged from 1 to 7months in duration. However, since regulationof the Murray River and its tributaries, changes in flow, waterquality and other parameters have directly influenced theBarmah–Millewa Forest. Most of the major creeks feeding thefloodplain have regulated flows. Floods that once occurredevery second year now occur about every 6–8 years, andthose that occurred every 10 years now occur about every25–30 years (MDBC 2005, 2007). Floods are of shorterduration, and sometimes occur in summer rather thanwinter–spring. Consequently, managers of the Murray systemand the Barmah–Millewa Forest are allocating water forimplementation of environmental flows together with otherstrategies to address issues of degradation, biodiversity loss,drought and climate change. Information on flow preferencesof the various ecological components of the system is requiredso as to guide environmental flow decision making and habitatmanagement.

Materials and methodsField surveys

Surveys of floodplain frogs were conducted in the Barmah–Millewa Forest from spring–summer 2000–01 to 2005–06(except 2004–05), at approximately monthly intervals duringthe core mid-Murray breeding season. Additional surveys werecompleted in the cooler months during dry years (Table 1). Thesesurveys spanned the first few years of the severe ‘millenniumdrought’ of 2000–09. Analyses for the present paper focus onthe surveys conducted in the Barmah Forest, Victoria, because of

a lack of suitable descriptive vegetation data and flow-modellingdata in the Millewa (NSW) section of the forest. In the BarmahForest, one primarywetland site was surveyedwithin eachwater-management area (WMA), and one secondary wetland site wassurveyed when feasible within constraints of project time andforest access. Primary wetlands are lower in the floodplain, andflood earlier than do secondary wetlands, which are generallymore elevated,flooding later and draining earlier. In total, 22 coresentinel study sites were used (2 sites� 11 WMAs in BarmahForest).

Sampling comprised the following:

(1) point-based identification of all frog calls heard (Littlejohn1987) and estimates of numbers calling of each speciesconducted for 15min, between 30min after sunset and30min before sunrise;

(2) active spot-light searches of 10min per site, followed bydip-netting, to determine species presence and age of non-vocalising frogs; and

(3) testing of basic water-quality parameters (pH, salinity,turbidity, temperature) in situ, using a calibrated HannaCombo EC/pH/Temp probe (Hann Instruments, RI, USA),and a Waterwatch turbidity tube (Waterwatch, Vic.,Australia).

Count-estimate categories were used where the number offrogs of a species calling exceeded 20, because of the difficulty inaccurately estimating large numbers of calling frogs at a site.Categories of 5 were used where numbers were between 20 and50, followed by categories of 10 between 50 and 100, andcategories of 100 from 100 and higher. In the event that siteswere dry at the time of survey and no frogs were calling, activespotlight searches for frogs were still conducted as normal.Searches were also conducted for individual (rarer) species offrogs, using response to call-playback. Evidence of breedingwas ascertained from observations of amplexus (mating),presence of eggs, and/or tadpoles and metamorphs collectedfrom three random 500-mm dip-net samples, each of 15-sduration in shallow flooded regions. Tadpoles collected werefield identified where possible (Anstis 2002), with stage ofdevelopment documented according to (Gosner 1960). Specieswere assumed to have bred successfully where either tadpoles

Table 1. Timing of floodplain frog surveys�, surveys conducted (shaded); X, no survey

Month Year2000–01 2001–02 2002–03 2003–04 2004–05 2005–06

July X � X X X XAugust X X � X X X

Core breeding season September � X X � X XOctober � � � � X XNovember � � � � X XDecember � � � � X �January � � X � X XFebruary � X � X X �March X � X X X XApril X X � X X XMay X � � X X XJune X X X X X X

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or metamorphs were located. Equipment hygiene protocolbetween study sites was routinely adhered to, including hand-washing, washing of survey vehicles (car, boat and bicycle) andwashing and disinfecting all material associated with directsampling, such as waders, nets and sampling trays.

Hydrological conditions

During 2000–01, there was widespread seasonal flooding fromSeptember to February, followed by environmental flows andadditional natural high flows (Fig. 1). The 2001–02 year wasrelatively dry, with below-average rainfall and above-averagetemperatures in most months and a relatively low incidence offlooding. High irrigation demands coincided with some rainfallevents to produce some early season high flows, spring rain-rejection events and a mid-autumn rain-rejection event. A rain-rejection event is a river flow or flood that is caused by release ofwater from storage to supply irrigators downstream, but whichis not extracted by irrigators because of local rainfall occurringafter the water was ordered (irrigators can cancel their waterorder after thewater has been released into the river fromstorage).The 2002–03 year was very dry, with below-average rainfalloccurring in most months. Extended low-level flooding occurredbetween August and December in most low-lying wetlands ofcentral and western Barmah Forest, because of transfers of largevolumes of water from Hume Reservoir to Lake Victoria. Othersites in the forest not influenced by the water transfers wereeither dry or continued to desiccate. Dry conditions continuedthrough 2003–04, with below-average rainfall occurring inmost months. Natural low-level flooding from the Ovens Riveroccurred from late July to October in low-lying wetlands, withsome replenishment in some sections of the forest from a shortrainfall-rejection event in December. Most wetlands dried out as

the year progressed. The 2005–06 year was marked by an initialseries of natural winter–spring flood peaks driven by high rainfallin the catchment, augmented by the release of an accumulatedenvironmental water allocation in spring–summer (the volumeof which represented the largest volume of water releasedspecifically for the environment in Australia’s history). Thisresulted in widespread medium-level forest flooding; however,monitoring was conducted on only two occasions, namely, inDecember 2005 and February 2006. All sites contained waterwhen surveyed in December, although forest environments athigher elevations remained dry.

Data compilation and analysis

All analyses were carried out in program R (RDCT 2007), usingappropriate packages where required. Temporal patterns inthe number of frogs of each species calling in each monthand year were explored using linear mixed effects models andzero-inflated models with the R packages ‘nlme’ (Pinheiro et al.2013) and pscl (Jackman 2011), restricting the models to theperiod September–February (during which most surveys wereconducted).

Four classes of geomorphic unit and four classes ofvegetation form were derived by aggregation of finer-scaleecological vegetation classes (EVCs) described by theVictorian Environmental Assessment Council (VEAC 2006)and examination of SPOT 5 imagery and aerial photographyin ArcMap (ESRI 2011). These classes (Table 2) were used inanalyses to explore possible broad associations between thenumber of frogs calling of each species and site characteristics.Although patterns and interactions between hydrology,geomorphology and vegetation are complex in this floodplain,the classes used were broadly correlated (Table 2) and related

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Fig. 1. Hydrograph at Yarrawonga gauge upstream of the Barmah–Millewa Forest for the study period, showing timingof frog surveys.

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to hydroperiod, with decreasing hydroperiod from drainageline to wetland to low-elevation floodplain to high-elevationfloodplain.

Site commence-to-flow threshold values were calculatedusing the River Murray floodplain inundation model (RiM–

FIM) 5-m raster map. The commence-to-flow threshold of asite represents the river discharge at which the site begins tobe inundatedwithwater. TheRiM–FIM is a research and decisionsupport tool for environmental flow management in the RiverMurray, developed using a geographical information system(GIS), remote sensing and hydrological modelling (Overtonet al. 2006). Following inspection of the intersecting site, EVCand RiM–FIM layers in ArcMap, a +�90m buffer was appliedto the survey-location polygons, ensuring that each site polygonencompassed the actual area surveyed. Distribution statisticsfor the commence-to-flow values for each site polygon weresubsequently calculated, and the minimum or threshold valueused in analyses. Further modelling of flow regime usingRiM–FIM data was not possible because of limitations of themodel at low-elevation floodplain sites and at low flows, andbecause of insufficient information regarding management offlow regulators within the forest.

Frog associations with site geomorphic unit, vegetation form,commence-to-flow thresholds and frequency of wetting duringthe survey period were tested using general linear models and

analysis of variance in R. The influence of the frequency ofwetting events at each site was tested using the number of timesa site was recorded as ‘wet’ during the survey proportional tonumber of times a sitewas surveyed (2000–06).Datawere pooledto site level, and variables included maximum number of frogspecies calling,maximum total number of frogs calling, presence/absence of any frog species, and the maximum estimated numberof each species calling. The number of frogs calling per site waslog-transformed +1 for analysis.

So as to compare frog community assemblages among sites,non-metric multidimensional scaling ordination was conductedon the ‘maximum estimated number calling’ of each speciesat each site, using the R package ‘vegan’ (Oksanen et al. 2011).Analyses were conducted with and without the ‘rare’ species(species that were recorded infrequently or were uncommon),and separate ordination plots were produced identifying sitegeomorphic units and vegetation form classes.

Results

Site characteristics

The sites surveyed spanned 14 ecological vegetation classes(Table 2), with commence-to-flow minimum thresholdsranging from 4000 to 51 000MLday–1. Turbidity, conductivity,acidity and water temperature recorded were within the normal

Table 2. Vegetation and geomorphic unit classes of each site

Site no. Site name Ecological vegetation class Vegetation form Geomorphic unit

1 Barmah Island Corry Drainage-line Aggregate Drainage line Drainage line2 Barmah Island Isle Tk Drainage-line Aggregate Drainage line Drainage line3 Big Bog Grassy Riverine Forest and Riverine Swamp

Forest ComplexForest, grassland and herbland High-elevation floodplain

4 Black Swamp Riverine Swamp Forest Forest High-elevation floodplain5 Boals Deadwoods Tall Marsh Grassland and herbland Wetland6 Bucks Crossing Floodway Pond Herbland Grassland and herbland Low-elevation floodplain7 Bunyip Gully Floodway Pond Herbland and Riverine

Swamp Forest ComplexForest, grassland and herbland High-elevation floodplain

8 Bunyip Waterhole Drainage-line Aggregate Drainage line Drainage line9 Doctors Point Floodplain Grassy Wetland and Floodway

Pond Herbland MosaicGrassland and herbland Wetland

10 Duck Hole Plain Mosaic of Riverine Swamp Forest andFloodway Pond Herbland-Riverine SwampForest

Forest, grassland and herbland Low-elevation floodplain

11 Goose Neck Floodplain Grassy Wetland Grassland and herbland Wetland12 Hughes Crossing Grassy Riverine Forest and Riverine Swamp

Forest ComplexForest, grassland and herbland Low-elevation floodplain

13 Hut Lake Central Drainage-line Aggregate Drainage line Drainage line14 Island Creek Drainage-line Aggregate Drainage line Drainage line15 Little Rushy Swamp Floodplain Grassy Wetland Grassland and herbland Wetland16 Mannions Drainage-line Aggregate Drainage line Drainage line17 Old Forcing Yards Riverine Swamp Forest Forest Low-elevation floodplain18 Steamer Plain Floodplain Grassy Wetland Grassland and herbland Wetland19 The Rookery Drainage-lineAggregate andRiverine Swamp

Forest MosaicForest Low-elevation floodplain

20 TwoMile Bunyip Mosaic of Riverine Swamp Forest andFloodway Pond Herbland-Riverine SwampForest

Forest High-elevation floodplain

21 TwoMile Sandridge Riverine Grassy Woodland Forest, grassland and herbland High-elevation floodplain22 Whores Creek ‘Sedgy Riverine Forest and Riverine Swamp

Forest ComplexForest Low-elevation floodplain

Floodplain frogs of Barmah Forest, Australia Wildlife Research E

rangeexpected for a lowlandfloodplain system, andweregenerallyregarded as being of acceptable quality for frogs and the majorityof other biota (Shafron et al. 1990; Hart et al. 1991; Bailey andJames 2000).

Species recorded

Nine frog species were recorded in the Barmah Forest over the6 years of survey (Table 3). Frogs were recorded at all of the corestudy sites. Limnodynastes tasmaniensis, Crinia parinsignifera,and Crinia signifera were widespread and recorded at all sites(Table 3). Other species recorded frequently included Litoriaperonii, Limnodynastes dumerilii, and Limnodynastes fletcheri.Crinia sloanei and Neobatrachus sudelli were rarely recorded.Pseudophryne bibroni was recorded only at one opportunisticsite in December 2000 (two males calling). The average numberof species recorded per site was 5� 1, with a maximum of sixspecies recorded at any one site.

The number of frogs calling was highest in late spring, andgenerally declined in late summer to autumn. Themost numerousspecies recorded calling in Barmah Forest were Limnodynastestasmaniensis (43% of total frogs counted), Crinia parinsignifera(23%), and Crinia signifera (18%). Widespread speciesrecorded in lower numbers were Litoria peronii (8% oftotal frogs counted), Limnodynastes dumerilii (5%), andLimnodynastes fletcheri (2%). Crinia sloanei was recorded inBarmahForest on only two occasions. FourNeobatrachus sudelliwere recorded calling at Barmah Island Corry track on 13November 2000. No response occurred at any of the sites inany survey to tape playback of calls of Litoria raniformis,Limnodynastes interioris, Neobatrachis sudelli, Pseudophrynebibroni or Crinia sloanei.

Sufficient information was available to model spatial andtemporal relationships for six species, including Limnodynastestasmaniensis, Crinia parinsignifera, Crinia signifera, Litoriaperonii, Limnodynastes fletcheri and Limnodynastes dumerilii.

Temporal trends

The number of species calling per site and session generallydecreased over time, being highest in late spring and decliningthrough summer, with fewer species being recorded in dry years(Table 3). The greatest number of species was recorded during

2000–01, when nine species were recorded overall, and thenumber of species calling per site decreased rapidly from 3–6early in the season to 0–2. Lower numbers of frogs calling(all species) were recorded in dry years (2001–02 and2002–03) than in wet years (2000–01 and 2003–04). Theseasonal timing of peak numbers calling differed amongspecies (Fig. 2); however, taking into account the effectsof year and site, overall, there was no strong evidence ofdifferences between years in the pattern of calling over time.Across all years surveyed, the only species heard in every monthfrom September to February were Limnodynastes tasmaniensisand Litoria peronii.

There were distinct differences among species in terms ofwhen the greatest numbers were heard calling (Fig. 2). In the2000–01 survey year, Litoria peronii was heard calling inevery month from September to January but, across all yearssurveyed, was most commonly heard in October and December.In general, Limnodynastes fletcheri was heard in greatestnumbers in November and December. The remaining species,Limnodynastes dumerilii, Limnodynastes tasmaniensis, Criniasignifera, and Crinia parinsignifera, were recorded calling insignificantly greater numbers in September than in anyother month. These species were also commonly recorded inOctober.

The most persistent species across all months and yearswas Limnodynastes tasmaniensis, which was generally themost prevalent species from September to February. Criniasignifera dominated the vocalising species in the coolerperiods, and Crinia parinsignifera was heard from late winterthrough to early summer.

Spatial trends

Frog assemblages

Differences between frog assemblages were driven by rarespecies. Following non-metric MDS ordination, the influence ofthe two ‘rare’ species was immediately visible, separating twosites (Bucks Crossing and Doctors Point) from the remaining20 sites in the MDS ordination (Fig. 3a). However, when ‘rare’species were removed from the analyses, no differences betweensites were apparent (Fig. 3b). Geomorphic unit significantly

Table 3. Species recorded, the number of core sites at which they were recorded, and the percent of all frogs counted represented by counts of eachspecies during the period 2000–2006

*Species recorded at non-core sites within the forest. NS, not surveyed

Species Common name No. of coresites (of 22)2000–06

% of all frogscounted2000–06

No. ofcore sites2000–01

No. ofcore sites2001–02

No. ofcore sites2002–03

Number ofcore sites2003–04

No. ofcore sites2004–05

No. ofcore sites2005–06

Limnodynastes tasmaniensis Spotted marsh frog 22 42.9 18 8 16 21 NS 2Crinia parinsignifera Plains froglet 22 23.35 17 9 13 20 NS 0Crinia signifera Common froglet 22 18.24 17 9 14 20 NS 0Litoria peronii Peron’s tree frog 21 8.36 17 2 16 16 NS 3Limnodynastes dumerilii Pobblebonk frog 18 4.84 13 0* 4 13 NS 0Limnodynastes fletcheri Barking marsh frog 17 2.23 4 7 3 11 NS 2Neobatrachus sudelli Common spadefoot 2 0.04 1 0 0 0 NS 0Crinia sloanei Sloane’s froglet 1 0.03 0* 1 0 1 NS 0Pseudophryne bibroni Bibron’s toadlet 0* 0* 0* 0 0 0 NS 0Total number of species recorded in the forest 9 7 6 7 NS 3

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affected species assemblage when rare species were included(ANOSIM: global r= 0.1708, P = 0.05), but not when rarespecies were excluded (ANOSIM: global r= –0.03249,P = 0.73). Vegetation form had no significant effect on species

assemblage in either case. There were also no significantdifferences in species assemblage between wetland site levels(primary–secondary or high–low) or betweenwater managementareas.

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Fig. 2. The mean number of frogs calling during each month of the main breeding season, foreach year of survey and six species. Error bars indicate standard deviation.

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Fig. 3. Multi dimensional scaling ordinations of the 22 sites in four dimensions, basedon the maximum estimated number calling of each frog species, with geomorphic unitsidentified (a) including rare species (stress = 0.06) and (b) excluding rare species(stress = 0.04).

Floodplain frogs of Barmah Forest, Australia Wildlife Research G

Frog species calling

The number of frog species calling did not differ significantlyamong geomorphic units, vegetation forms, wetland site levels(primary–secondary/high–low), or water-management areas.There was no significant relationship with either commence-to-flow threshold or wetting frequency (the number of times asite was recorded as ‘wet’ proportional to number of times a sitewas surveyed 2000–06).

Total number of frogs calling

The total number of frogs calling was significantly higher inwetland sites than in other geomorphic units (P = 0.044; Fig. 4,Table 4). There was no significant relationship with vegetationform, commence-to-flow threshold or wetting frequency. Therewere no significant differences in the total number of frogs callingamong wetland-site levels or among water management areas.

Estimated number calling by frog species

The maximum numbers of Limnodynastes tasmaniensis andLitoria peronii calling were significantly greater in grassywetlands than in other sites (P= 0.035 and P = 0.012,respectively; Fig. 4, Table 4). The maximum numbers callingof all other species were not influenced by either geomorphic unitor vegetation form.

The number of times a site was recorded as ‘wet’ proportionalto the number of times a site was surveyed (2000–06) was relatedto the maximum estimated number of frogs over all surveyscalling at a site for three species. Significant positive relationshipswith wetting frequency were found for Limnodynastes fletcheri(P = 0.025; Fig. 5a) andCrinia signifera (P= 0.011; Fig. 5b), anda borderline positive relationship was found for Limnodynastesdumerilii (P= 0.074; Fig. 5c).

There were no significant differences in the number of frogsof a particular species calling between wetland site levels orbetween water management areas, and there were no significantrelationships with commence-to-flow threshold for any species.

Evidence of reproduction

Evidence of breeding (tadpoles or metamorphs) was found forfive species every year (Table 5). It is difficult to distinguishbetween the closely related Limnodynastes species beforemetamorphosis, and so where one was recorded the othersmay also have bred. Breeding by rare species can be verydifficult to detect and, therefore, for rare species a lack ofrecords does not necessarily reflect a true lack of reproduction.

Discussion

Temporal patterns

(a) Frog species presence in the Barmah Forest floodplain

During the 2000–06 surveys of Barmah Forest, the followingsix frog species were common and widespread: Limnodynastestasmaniensis, Crinia parinsignifera, Crinia signifera, Litoriaperonii, Limnodynastes dumerilii and Limnodynastes fletcheri.In contrast, three species were rarely recorded, including Criniasloanei, Neobatrachus sudelli and Psuedophryne bibroni. Thesespecies have not been formally recorded in the VictorianBiodiversity Atlas as present in Barmah Forest since springand summer 2000 (VBA 2011); however, Crinia sloanei andPsuedophryne bibroniwere last heard during the surveys that arethe subject of this paper in the spring of 2003. At the time ofsurvey, the following two of these species were new formalrecords for the Barmah–Millewa Forest: Neobatrachus sudelliand Psuedophryne bibroni (VBA 2011). These species aregenerally uncommon in the local area; however, Neobatrachussudelli is found throughoutmost ofwesternNewSouthWales andVictoria, burrowing for much of the time and becoming activeafter heavy rain (Hero et al. 1991; Anstis 2002). The only site atwhich Neobatrachus sudelli was recorded was a rain-filleddepression that dried relatively rapidly. Psuedophryne bibroniis a relatively cryptic species that is found in central Victoria andeastern New South Wales (Hero et al. 1991; Anstis 2002).December 2000 was the first month when Pseudophyrnebibroni was recorded, when two individuals were heard to callfrom a single location thatwas opportunistically heard en-route toa fixed survey site. This is a predominantly autumn-breedingspecies and hence most of these surveys would not have detectedit even if it was present. However, the record of this species inBarmah Forest was the first for this area (DCFL 1990; Hero et al.1991; VBA 2011).

The survey period described in this study (2000–06) fallswithin the period of the ‘milleniumdrought’ of 2000–09 in south-eastern Australia. The effects of drought in combination with theeffects of anthropogenic flow-regime change are likely to havebeen significant for frogs in Barmah Forest as in most south-eastern Australian river systems (Gillespie and Hines 1999;Hazell et al. 2003; Murray and Hose 2005). Declines in thenumber of frog species and individuals calling during the‘millennium drought’ of 2000–09 are not unique to BarmahForest. Surveys conducted across box ironbark forests ofnorthern Victoria in 2006–07 found that fewer than half of theanuran species historically known from the region were recorded(Mac Nally et al. 2009). Even relatively common species hadapparently disappeared from many sites, with lower numbers ofremaining ‘resilient and hardy’ species recorded.MacNally et al.

0

50

100

150

200

250

Drainage line High elevationfloodplain

Low elevationfloodplain

Wetland

Num

ber

of fr

ogs

calli

ng fi

tted

mod

el

Geomorphic unit

Litoria peroni

All species total

Limnodynastestasmaniensis

Fig. 4. Fitted model of the predicted maximum number of frogs callingamong floodplain geomorphic units (all species, spotted marsh frogLimnodynastes tasmaniensis, and Peron’s tree frog Litoria peroni)� se.

H Wildlife Research H. M. McGinness et al.

Tab

le4.

Max

imum

s,means

andstan

dard

deviations

ofnu

mbers

offrog

srecorded

calling

ateach

site

forallspecies

combinedan

dthesixmostcommon

individu

alspeciesacross

allsurveys

Site

no.

Vegetation

form

Geomorphic

unit

Allspecies

Lito

riaperonii

Limnodynastes

dumerilii

Limnodyna

stes

fletcheri

Limnodyna

stes

tasm

aniensis

Crinia

parinsignifera

Criniasign

ifera

max

� xsd

max

� xsd

max

� xsd

max

� xsd

max

� xsd

max

� xsd

max

� xsd

1Drainagelin

eDrainagelin

e227

2054

91

22

00

10

0120

826

606

1750

514

2Drainagelin

eDrainagelin

e40

1013

151

35

01

121

210

23

202

520

46

3Forest,grassland

andherbland

High-elevation

floo

dplain

112

825

50

14

01

00

050

411

403

920

14

4Forest

High-elevation

floo

dplain

187

2556

252

713

13

20

010

011

2960

818

253

7

5Grassland

and

herbland

Wetland

310

3977

303

915

08

314

01

200

1745

504

1250

715

6Grassland

and

herbland

Low

-elevatio

nfloo

dplain

676

162

00

50

10

00

202

525

36

151

4

7Forest,grassland

andherbland

High-elevation

floo

dplain

628

1815

24

20

00

00

454

1120

25

40

1

8Drainagelin

eDrainagelin

e116

1834

202

530

27

30

160

817

354

915

14

9Grassland

and

herbland

Wetland

104

1630

302

70

00

00

030

48

304

970

516

10Forest,grassland

andherbland

Low

-elevatio

nfloo

dplain

9019

2925

36

201

41

00

254

850

613

605

13

11Grassland

and

herbland

Wetland

146

2141

71

25

01

10

013

515

3240

410

152

4

12Forest,grassland

andherbland

Low

-elevatio

nfloo

dplain

5510

205

01

10

00

00

305

1120

36

152

4

13Drainagelin

eDrainagelin

e335

3680

201

45

01

353

9200

1745

100

1024

405

1114

Drainagelin

eDrainagelin

e72

1019

201

415

13

00

070

414

252

620

24

15Grassland

and

herbland

Wetland

240

1966

504

140

00

102

410

08

2860

517

202

6

16Drainagelin

eDrainagelin

e166

1938

152

450

210

71

220

25

404

9100

821

17Forest

Low

-elevatio

nfloo

dplain

120

1329

00

01

00

201

550

412

404

1030

48

18Grassland

and

herbland

Wetland

380

7811

380

718

302

625

25

300

4377

100

1224

100

1329

19Forest

Low

-elevatio

nfloo

dplain

105

1428

102

315

14

00

030

59

304

830

27

20Forest

High-elevation

floo

dplain

115

1333

61

20

00

20

060

617

454

1220

25

21Forest,grassland

andherbland

High-elevation

floo

dplain

9510

2430

26

30

10

00

554

1330

38

101

2

22Forest

Low

-elevatio

nfloo

dplain

355

112

01

00

00

00

152

515

25

51

1

Floodplain frogs of Barmah Forest, Australia Wildlife Research I

(2009) suggested that extendeddroughtwas a significant driver ofthese changes as well as a future risk for species persistence in theregion. In theMurrayRiver andBarmahForest, reducedoverbankflooding and unseasonal high-velocity summer irrigation flowshave significantly changed both the riverine and floodplain frogenvironments, particularly during the core frog-breeding season.Changes in flow frequency, magnitude and duration driven byeither drought or anthropogenic factors can affect water quality inboth lotic and lentic frog habitats. Hazell et al. (2003) identifiedturbidity and sedimentation as particular threats in small erodingstreams, because tadpoles are often specialised for suspension orfilter feeding. Increases in sediment load would both reducefeeding efficiency and reduce the production of tadpole foodresources. Blackwater or hypoxic events in floodplain forests canalso reduce survival of aquatic and amphibian fauna (Howitt et al.2007; Hladyz et al. 2011). For example, hypoxic conditions weresuggested to cause adult frogs to become inactive ormove toother

potential breeding sites by Healey et al. (1997) when theseauthors failed to record any adult frogs following a low-oxygen event triggered by a cyanobacterial bloom in a majorbillabong. Although the development of blackwater is a naturalprocess, its occurrence in Barmah Forest is arguably now morecommon, driven by high flows in summer, higher forest treedensity and reduced flooding frequency, allowing for greater leaflitter accumulation.

(b) Timing of calling and breeding

The calling periods recorded during these surveys fit withinthose recorded byothers (Brook 1980;Hero et al. 1991; Lemckertand Mahony 2008); however, the peak or core calling periods ofsome species in Barmah Forest appear to have a tighter span(Table 6). Limited data were available for seasons other thanspring and summer. The dominant calling period formost speciesin Barmah during these surveys was from September to October,except for Litoria peronii and Limnodynastes fletcheri, whichwere most commonly recorded calling later in the season, fromOctober to December.

There was no strong evidence of differences between wet anddry years in the seasonal pattern of calling for each species,suggesting that the calling periods of individual species tendnot to vary with water availability, although more data arerequired to confirm this. However, significantly lower numbersof frogs calling and of tadpoles andmetamorphswere recorded indry years than inwet years, indicating some influence onbreedingsuccess.

Similarly, at the seasonal scale, the number of frog speciescalling and the total number of frogs calling decreased from earlyspring through summer, even when floodwater was availablelate in the season. If the core breeding time for most species isspring, and not all species respond opportunistically to flooding,then this is to be expected. However, river regulation hasreduced the availability of floodwater (and consequentlybreeding habitat) during spring, and has instead increased theavailability of floodwater during summer. This switch is likely tohave negatively influenced frog breeding in this area. A possiblesymptom of this is that overall reproductive effort appeared to below across the floodplain, despite the fact that some evidence ofattempted breeding was found for five (possibly six) speciesin Barmah Forest every year of survey. Another possibleinfluence may have been the severe 2000–09 drought and theconsequent lackof suitable rainfall. Following surveys conductedin northern Victoria during 2006–07, Mac Nally et al. (2009)concluded that frog reproduction had effectively failed overthat period, with fewer than one in four sites showing evidenceof reproduction. However, with a limited dataset of only 5 years,it is difficult to assess seasonal, rainfall or temperature influencesagainst hydrologic conditions because of differences in theoccurrence, timing and extent of inundation events among years.

Spatial relationships

The sites surveyed in Barmah Forest represent a range ofenvironmental conditions (geomorphology, vegetation typesand hydrological regimes) and most frog species arewidespread among these. This is reflected in the relativeuniformity in the number of species recorded calling per site.

Barking marsh frogLimnodynastes fletcheri

(a)

(b)

(c)

0

5

10

15

20

25

30

35

0 0.2 0.4 0.6 0.8 1.0

Common frogletCrinia signifera

0102030405060708090

100

Est

imat

ed n

umbe

r ca

lling

Pobblebonk frogLimnodynastes dumerili

05

101520253035404550

Proportion of times site was recorded wet 2000–2006

Fig. 5. Fitted models of the predicted maximum number of frogs callingin response to the proportion of times a site was recorded wet during surveysfrom 2000 to 2006. (a) Limnodynastes fletcheri; (b) Crinia signifera;(c) Limnodynastes dumerili. Solid line represents the fitted model, dashedlines the standard error, points represent actual maximum number recordedcalling at a site. An outlier (0.7, 150) in plot (c) is represented as ‘X’ for easeof plot interpretation. Note that the y-axis scale is different for each species.

J Wildlife Research H. M. McGinness et al.

There were insufficient data to determine habitat preferencesfor the rare species; however, the significance of the influenceof geomorphic unit on site species assemblage is apparentlydriven by their presence or absence. The association betweenwetlands and the abundance of two common species,Limnodynastes tasmaniensis and Litoria peronei, was stronger.In fact, the abundance of L. tasmaniensis is the main driver ofspatial patterns in overall frog abundance. It is likely that thiseffect is associated with the presence of diverse and densegrassland and herbland vegetation. The sites categorised as

‘wetland’ geomorphic units in the present study are associatedwith grassland, herbland and marsh vegetation communities thatare generally distinct from those in other geomorphic units(VEAC 2006). Well vegetated grassy wetlands are idealbreeding habitat for most frog species, and the availability offringing grassy vegetation is a well known predictor of frogspecies richness and abundance (Hazell 2003; Mac Nally et al.2009; Wassens 2010; Wassens et al. 2010). Shallow ephemeralwetlands are sunnier, warmer, and more likely to have lowpredatory fish abundance than are other habitats, particularly

Table 5. Occurrence of tadpoles and metamorphs in each year and core breeding month sampledOccasionally advanced metamorphs or very young frogs were noted outside of dip-net samples, but they were not counted. 1, present (shaded);

0, not detected

Year Tadpoles or metamorphs Sep Oct Nov Dec Jan Feb

2000–01 Tadpoles 1 1 1 1 0 0Metamorphs 0 1 1 1 0 0Limnodynastes tasmaniensis 1 1 1 1 0 0Limnodynastes fletcheri 1 1 1 0 0 0Limnodynastes dumerilii 1 1 1 1 0 0Crinia signifera 1 1 1 0 0 0Crinia parinsignifera 1 1 1 0 0 0Litoria peronii 0 0 0 0 0 0Crinia sloanei 0 0 0 0 0 0

2001–02 Tadpoles 1 1 1Metamorphs 1 1 1Limnodynastes tasmaniensis 1 1 1Limnodynastes fletcheri 1 1 0Limnodynastes dumerilii 1 1 0Crinia signifera 1 1 0Crinia parinsignifera 1 1 0Litoria peronii 0 1 1Crinia sloanei 0 0 0

2002–03 Tadpoles 1 1 0Metamorphs 1 1 1Limnodynastes tasmaniensis 1 1 1Limnodynastes fletcheri 1 1 1Limnodynastes dumerilii 1 0 1Crinia signifera 1 0 0Crinia parinsignifera 1 1 1Litoria peronii 1 1 1Crinia sloanei 0 0 0

2003–04 Tadpoles 0 1 1 1 1 1Metamorphs 0 1 1 1 1 1Limnodynastes tasmaniensis 0 1 1 1 1 0Limnodynastes fletcheri 0 0 0 1 0 0Limnodynastes dumerilii 0 1 1 1 0 0Crinia signifera 0 1 1 0 0 0Crinia parinsignifera 0 1 0 0 0 0Litoria peronii 0 1 1 1 1 1Crinia sloanei 0 0 0 0 0 0

2005–06 Tadpoles 1 0Metamorphs 1 1Limnodynastes tasmaniensis 1 1Limnodynastes fletcheri 1 1Limnodynastes dumerilii 0 0Crinia signifera 1 1Crinia parinsignifera 0 1Litoria peronii 1 1Crinia sloanei 0 0

Floodplain frogs of Barmah Forest, Australia Wildlife Research K

if they are inundated overland or via rainfall rather than viachannels. In northern Italy, Ficetola and Bernadi (2004,p. 219) found that frog presence ‘depends strongly on habitatquality and isolation: the richest communities live in fish-free,sunny wetlands near to occupied wetlands’. In Barmah Forestduring flood recession, channels and pools that pond water forrelatively long periods of time are almost devoid of submergedaquatic or semi-aquatic vegetation. In contrast, wetlands that areshallow, broad, open and low gradient drain more quickly, butgenerally have more diverse and abundant macrophyte, grass,herb and forb cover. In general, frogs in Barmah Forest appearto prefer freshly inundated ephemeral wetland sites containingaquatic vegetation and/or abundant large woody debris,especially at ephemeral wetland sites. However, observationsmade during these surveys suggested that Limnodynastes speciesprefer reeds or emergent woody debris in deeper water, whereasCrinia species prefer shallow flooded grasses and fine woodydebris (Ward 2000–2006). These sites also contained a greaterdiversity and abundance of invertebrates and small fish speciesthan didwetlands lacking habitat structure or fresh inflows (Ward2000–2006).

Knowledge of positive relationships between wettingfrequency and estimated number of frogs calling forLimnodynastes fletcheri, Crinia signifera and Limnodynastesdumerilii is potentially of use in management of environmentalflows to increase populations of these species. L. fletcheri andL. dumerilii may be species of particular interest for suchmanagement, because, although they occur at many sites, theirpopulations appear to be generally low with occasional spikes,and may be more sensitive to hydrological management.Increased flooding via environmental flows may be beneficialto these and other frog species, particularly those that have longbreeding seasons or that require long periods of inundation fortadpole development and metamorphosis. Several studies havereported sensitivity of amphibians to hydrological characteristicssuch as hydroperiod, duration, or water level (Morand and Joly1995; Richter and Azous 1995; Parris and McCarthy 1999; Reidand Brooks 2000; Tockner et al. 2006; Wassens 2010; Wassensand Maher 2011). Many of these focussed on species richnessrather than population size. Species richness of frog assemblages

in anUpperRhonefloodplain (France) hasbeen linkedwith levelsof ‘disturbance’ by flood events (Morand and Joly 1995), withsites experiencing intermediate levels of flooding and dryinghaving the highest frog species richness. In contrast, a study ofamphibian species richness in the Tagliamento floodplain (Italy)found that even areas experiencing frequent disturbance by floodor drought were valuable habitat for frogs, with assemblagesdisplaying a high degree of nestedness (Tockner et al. 2006).In this case, species richness at a given site was significantlycorrelated with distance from vegetated islands, fish density andwater temperature (Tockner et al. 2006).

Knowledge gaps

Alteration of hydrological regimes has been suggested as apotential threat for several Australian frog species, some ofwhich are listed as Vulnerable or Endangered (e.g. Litoriaraniformis) (Hero et al. 2006). However, researchdocumenting the influence of flow history, long-term flowregime, or landscape-scale flow pattern on amphibianpopulations is rare (Wassens 2010; Wassens and Maher 2011).Despite the obvious links between frog populations and wateravailability, few data exist on interactions among habitat, flowand frog populations, or the effects of changes in floodplainflow regimes on frog populations (Reid and Brooks 2000;Hazell 2003; Wassens 2010; Wassens and Maher 2011). Thechallenge of accurately measuring frog populations has madeassessment of the relative importance of the various drivers offrog diversity and abundance difficult (Healey et al. 1997).However, some frog species appear to be particularly sensitiveto riparian or flow disturbance. For example, lotic frog speciesin Kosciuszko National Park have been found significantly lessoften in streams below impoundments or other structuresaffecting stream flow, than they are in relatively undisturbedstreams (Hunter and Gillespie 1999). Similarly, populations ofMixophes balbus are generally not found in streams withdisturbed riparian vegetation or significant human impacts inthe upper catchment (Mahony et al. 1997). There is clearly a needfor further research on the effects of flow-regime change onAustralian frog populations and communities.

Table 6. Calling periods recorded by the present study in comparison to previous records

Core season NSW(Lemckert andMahony 2008)

Full season NSW(Lemckert andMahony 2008)

Core season Vic.(Brook 1980)

Full season Vic.(Brook 1980)

This study –

most recordsThis study –

all records

Limnodynastes tasmaniensis Sep–Apr All year (very few in June) Aug–Mar July–Mar Sep–Oct Sep–FebCrinia parinsignifera Sep–Apr All year (very few in June) Aug–Dec,

March–MayJuly–Mar Sep–Oct Sep–Dec

Crinia signifera Jul–Apr All year All year All year Sep–Oct Sep–NovLitoria peronii Sep–Mar All year (very few in June) Sep–Dec Sep–Jan Oct–Dec Sep–FebLimnodynastes dumerilii Sep–Mar July–May (very few in July,

Aug, Apr, May)Aug–Apr Aug–Jun Sep–Oct Sep–Dec

Limnodynastes fletcheri Oct–Apr Sep–Apr (very few in Sep,Jan, Feb)

Oct–Nov Sep–Apr Nov–Dec Oct–Dec

Neobatrachus sudelli All year All year Aug–Oct,Mar–May

Aug–Nov,Feb–May

Nov

Crinia sloanei Sep–Jan, Mar Sep–Jan, Mar July–Oct July–Nov, May Sep–NovPseudophryne bibroni Dec–May All year (very few in Sep–Nov) Mar–May Feb–Jun Dec

L Wildlife Research H. M. McGinness et al.

Conclusions

Several Australian frog species that are dependent on floodplainrivers are in decline, and ecological information for mostspecies is inadequate for assessing factors limiting distributionand abundance, or identifying causes of declines (Gillespieand Hines 1999; Murray and Hose 2005; Hero et al. 2006).Because frogs are such sensitive indicators of habitat condition(Healey et al. 1997; Hazell et al. 2001; Jansen and Healey2003; Hartel et al. 2007; Wassens et al. 2010), the spatial andtemporal patterns detected by monitoring of frog communitiesin floodplains are important sources of information for managersand scientists alike. In Barmah Forest, the influence of floodfrequency on frog and tadpole abundance indicates that, in thelong-term, insufficient flooding will result in reduced speciesrichness through changes in habitat availability and quality.The seasonal timing of flooding may also influence thebreeding success of individual species with differentpreferences. Flooding from September to December is requiredto maximise responses in all species recorded, and this will inturn increase the likelihood of species persistence and maximumdiversity. In addition, the preservation and regular floodingof well vegetated grassy wetlands is likely to be of specialimportance for floodplain frog persistence and diversity. Thepresent study has demonstrated the importance of managedflooding for frog abundance, and has informed managementactions for conservation of frog species in Barmah Forest. Inparticular, it has emphasised the value of key habitats such aswell vegetated grassy wetlands and reinforced the need tomake their preservation a priority for management. Finally,it has identified knowledge gaps to drive future field datacollection for improved modelling and prediction, including aneed for further research on the effects of flow-regime change onAustralian frog communities.

Acknowledgements

The field surveys on which this work is based were funded by the Barmah–Millewa Forum, with financial assistance from the Murray–Darling BasinCommission (MDBC) for water-management related activities within theBarmah–Millewa Forest, and directly funded by the MDBC for the final yearof survey (2005–06).Analyseswere fundedby theCSIROWater for aHealthyCountry Flagship. We thank the following people for assistance withcollection or review of the original data: Rolf Weber, Murray Thorson andMichael Caldwell (Department of Sustainability & Environment), JohnKneebone (Parks Victoria), David Leslie, Paul Childs and Andrew Stirling(State Forests of New South Wales), Ian Ward, Tony Fonte, Paul O’Connor,PhillipDwyer,MarionAnstis, andMurrayLittlejohn.NickNicholls (CSIRO)generously assisted with multivariate statistics in ‘R’, while Sue McIntyre(CSIRO) and an anonymous reviewer reviewed the manuscript.

Fieldwork was conducted under the following licences:

(1) Victorian Department of Natural Resource & Environment and ParksVictoria Research Permits (# 10001043, # 10001342, 10001483,# 10001812, # 10003518);

(2) NSW State Forests Special Purposes Permit for Research (# 05603,10252, 28183);

(3) NSW National Parks & Wildlife Service Scientific Investigation Licence(# A2999, # A3232, S10633); and

(4) NSW Animal Care and Ethics Authority Animal Research Approval(# 17/01, # 06/02, 27/05 & 05/03).

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