Bell Frog Research Articles

Meal or mate: Exploring the evidence of sexual cannibalism among amphibians.

Active forms of cannibalism that involve predation of live conspecifics occur widely among amphibians, most notably by tadpoles that feed on each other and adults that feed on juveniles. In contrast, cannibalism among amphibian adults (adult-adult cannibalism) is less often reported and there have been no investigations on the occurrence of sexual cannibalism in this group to date. In this study, we present an observation of potential sexual cannibalism involving an adult female green and golden bell frog, Litoria aurea, preying on a conspecific adult male during the species' breeding season. By comparing our observation to the available literature, we show that adult-adult cannibalism among amphibians is rare but tends to be committed by females against their male counterparts. We thus suggest that the occurrence of sexual cannibalism should be extended to include this group, where sexual size dimorphism occurs widely among adults that congregate spatially during breeding periods, both predictors of intra-specific predation. We hypothesise that amphibian females may be able to exploit male advertisement calls to differentiate suitable partners from potential prey and that male individuals are vulnerable to sexual cannibalism as they must risk attracting and physically exposing themselves to females in order to reproduce. Our findings reveal the complex dynamics that exist within adult amphibian populations, suggesting that females may have a choice when deciding how to interact with and utilise their male counterparts. As our findings are preliminary, based on a small sample size of records, including several from captive individuals, we encourage authors to publish their observations of cannibalism in the field, including unsuccessful attempts, to confirm the presence of sexual cannibalism in this group.

It's not easy being green: Comparing typical skin colouration among amphibians with colour abnormalities associated with chromatophore deficits.

Amphibians can obtain their colour from a combination of several different pigment and light reflecting cell types called chromatophores, with defects in one or several of the cells leading to colour abnormalities. There is a need for better recording of colour abnormalities within wild amphibian populations, as this may provide baseline data that can be used to determine changes in environmental conditions and population dynamics, such as inbreeding. In this study, we provide records of several types of chromatophore deficiencies, including those involving iridophores, xanthophores and melanophores, among two Australian tree frog species; the green and golden bell frog, Litoria aurea, and the eastern dwarf tree frog, L. fallax. We explore these colour abnormalities in terms of the chromatophores that have likely been affected and associated with their expression, in combination with typical colour phenotypes, colour variations and colour changes for these species. We intend for our photographs to be used as a visual guide that addresses the need for more accessible information regarding the physical manifestation of different chromatophore defects among amphibians.

The only way is down: placing amphibian ponds on plateaux protects against Gambusia colonization

Invasive species pose a significant threat to global biodiversity, prompting the need for novel management strategies. We investigated the effect of pond placement in preventing colonization by Gambusia holbrooki, an invasive fish impacting amphibians, including the threatened green and golden bell frog (Litoria aurea). Because Gambusia moves between aquatic systems during surface flow events, we aimed to determine whether constructing ponds on elevated plots devoid of fish was less likely to be colonized due to the absence of two‐way water connectivity with sources from below. Over eight consecutive years, we monitored Gambusia presence at 50 ponds within an industrialized area of Kooragang Island, New South Wales, Australia, home to one of the largest extant subpopulations of L. aurea. This included 24 constructed ponds, 19 of which were on elevated plots, along with 26 historic ponds already present prior to the study. None of the ponds constructed on elevated plots were ever colonized by Gambusia during the study period, while most (three out of five) constructed at lower elevation and historical ponds (25 out of 26) were. Our findings indicate that the elevated plots acted as plateau safe havens, with elevation difference rather than proximity to Gambusia sources the key driver preventing colonization. These plateaus are now functioning as some of the only Gambusia‐free breeding habitat for L. aurea in this area. This research highlights the role of landscape topography and intentional pond placement in safeguarding newly constructed wetlands from invasive fish, providing insights for wetland conservation and biodiversity protection.

Lovers in strange places: amphibian calling and amplexus detected in tidal mangrove creeks after rainfall

Temporary freshwater lenses can form in saline environments after rainfall, providing essential resources for species including drinking water and dispersal routes. However, there is limited indication that these lenses can also be used for breeding. Herein, we provide evidence of the green and golden bell frog, Litoria aurea, performing breeding activities, including calling and amplexus, in tidal mangrove creeks on Kooragang Island, NSW, Australia. Our findings suggest that these creeks intermittently phase into a low salinity state after the influx of fresh water from rainfall, forming temporary freshwater lenses that can be exploited before the creeks revert to a saline state. These lenses had salinities (1.4 ppt and 4.5 ppt) within the tolerance limit of L. aurea tadpoles, although we are unsure whether oviposition took place and offspring survival to metamorphosis was achieved. It is possible that anthropogenic disturbances to hydrology on Kooragang Island have benefited L. aurea by restricting tidal influences in mangrove creeks, prolonging the duration of freshwater lenses.

Modelling the sustainable harvest of wild populations for the conservation of a threatened amphibian

AbstractHarvesting wild populations is increasingly used to support conservation initiatives, including translocations, captive assurance colonies, and breeding programs. Best‐practice guidelines recommend that population viability analyses should be developed to assess the potential impact of harvest on source populations, allowing quantification of the risk incurred by the conservation programme. We developed a stochastic population model to assess the relative impact of harvesting southern bell frogs (Litoria raniformis) from three well‐studied populations. We compared the probability of local extinction when harvesting from three life stages (spawn, tadpoles, and adults) and at 21 harvest proportions (from 0 to 1, in 0.05 increments). Source populations with an estimated average of 100 adult frogs and with three or fewer breeding opportunities every 5 years showed increased risk of local extinction and lower minimum adult populations from all harvest strategies. Sources with an estimated average population >600 adult frogs and breeding opportunities in at least eight out of every 10 years were more resilient to harvest. For these populations, harvesting up to 25% of spawning masses or late‐stage tadpoles had a negligible impact on the probability of local extinction and caused a slight decrease in the minimum adult population. Harvesting adults impacted source populations more strongly than harvesting spawn or tadpoles. Our model highlights the importance of frequent breeding opportunities to offset the effects of harvesting L. raniformis. Populations sustained by environmental water delivery should be prioritized for the two consecutive breeding seasons following harvest in the absence of natural wetland inundation. We demonstrate a tractable approach to assess and compare the relative risk of wild harvest for threatened amphibians, with implications for the conservation of our focal species, L. raniformis. We encourage conservation practitioners to implement population viability analyses prior to wild harvest, whenever sufficient demographic information is available to build the requisite models.

Stochastic metapopulation dynamics of a threatened amphibian to improve water delivery

AbstractWater extraction and climate change are altering the availability of surface water globally, thereby contributing to amphibian population declines. The managed delivery of water to benefit environmental values (environmental watering) is a promising conservation technique that can support amphibian recruitment and maintain viable populations. Environmental water can be delivered in various spatial patterns and with different frequencies, but comparing the effectiveness of competing strategies is complicated by variable and interactive environmental processes. We built a spatially explicit, stochastic, hydroecological metapopulation model to compare the effects of five environmental‐watering scenarios on the probability of persistence of threatened southern bell frogs (Litoria raniformis) in a major river reach in southern Australia. We compared a no‐intervention control to two managed watering frequencies (moderate and frequent) delivered in two spatial designs (managed wetlands grouped or spread across the reach). More frequent water provision to intervention sites improved the reach‐wide (metapopulation) probability of persistence, and spreading intervention sites across the reach improved persistence more than grouping intervention sites together. When re‐examined under severe drought conditions, L. raniformis had a 0.04 probability of persistence without intervention, which improved to 0.56 with high watering frequency. Model‐guided environmental water provision can improve reach‐wide persistence of amphibian metapopulations by guiding spatial and temporal delivery patterns to reduce the risk of extinction.

Don't take my trees: Re‐evaluating the importance of trees when it comes to managing green and golden bell frog, Litoria aurea, habitat

AbstractIt is vital to identify habitats used by each life stage of a species to formulate effective conservation management and restoration guidelines. For the threatened green and golden bell frog, Litoria aurea, it is currently recommended that, to prevent waterbody shading, managed or constructed habitat for the species should not include trees. Shading has been reported to prevent adults from sun basking, reduce breeding activity, and lower water temperatures, which may impede tadpole growth and development and provide optimum conditions for the amphibian chytrid pathogen, Batrachochytrium dendrobatidis. However, the complete exclusion of trees, which are naturally present in L. aurea habitat, warrants evidence that supports this recommendation. In the present study, we used a multi‐year dataset on an L. aurea population on Kooragang Island, NSW, Australia to determine the occurrence of tree use by post‐metamorphic individuals. These data included information on nearly 12 500 individuals captured from 86 waterbodies across 8 consecutive breeding seasons. We found that tree use by juveniles, adult males, and adult females was widespread and common, occurring both during the day and night, with more than one out of every 20 individuals captured in trees. Our findings suggest that trees are a potentially important attribute of the terrestrial component of wetland habitats occupied by L. aurea. We hypothesize that trees may (i) create microhabitat for foraging and/or increased diversity of prey species, (ii) provide refuge from predators, and (iii) allow sun basking off the ground, thereby offering protection against the chytrid fungus while removing them from chytrid‐prevalent environments such as water and moist soils. We call for the careful reconsideration of tree exclusion within L. aurea habitat and further research into the benefits of allowing trees to grow near waterbodies to accommodate the ecological needs of this threatened species.

Moved frogs don’t settle: Evaluating the impact of translocation on the movement behaviour of a threatened frog

The deliberate movement of wildlife is an accepted mitigation measure to manage the impact of anthropogenic activities. A presumption is that moved individuals settle at recipient sites that possess appropriate habitat. However, translocations have a low rate of success, with many projects unable to identify the cause of failure. We studied the translocation of a threatened amphibian, the green and golden bell frog, Litoria (=Ranoidea) aurea, over short distances within a metapopulation in Australia. Individuals were removed from a fenced area of contaminated habitat earmarked for remediation (donor site) and translocated to nearby ponds (recipient sites) to maintain the breeding population in-situ and allow future natural recolonisation once remediation was completed. The distance between recipient and donor site significantly influenced the chance of translocated frogs being detected back at the fenceline, with the return rate dropping from 35 % to 5 % when the recipient site was moved from 50 to 400 m away. Additionally, translocated frogs exhibited heightened movement from the recipient site when compared to non-translocated frogs. This is one of only a few artificial movement studies of amphibians, with implications for the management of populations undergoing translocation. Our work shows the potential dangers of using translocation to remove individuals from land development and presuming this avoids impacts to threatened species. We recommend monitoring the return of translocated amphibians to donor sites and disturbances to movement behaviour induced by translocation, in order to predict the likely effectiveness of amphibian translocations for mitigating the ecological impacts associated with land development.

Monitoring the Green and Golden Bell Frog Litoria aurea on the Crookhaven floodplain at Nowra, New South Wales from 2016-2022 and implications for conservation

ABSTRACT Systematic (time constrained) and targeted surveys were conducted for the Green and Golden Bell Frog Litoria aurea from 2016-2022 on the Crookhaven River - Shoalhaven River floodplains, on the south coast of New South Wales. Systematic nocturnal surveys were conducted at 30-34 sites, three to four times between October and March. Litoria aurea were observed at 20 sites and males were heard calling at five of these. The majority of detections during the breeding season (January - February) were in flooded areas of Terara Swamp and Brundee Swamp, while outside the breeding season more frogs were seen in the catchment of Rotten Creek, the largest tributary of Brundee Swamp. Ten of the systematic sites were ponds constructed for the species as offsets for various developments. Breeding activity (calling males) was detected at two of these offset ponds, but no tadpoles or juveniles were found. The number of frogs detected during systematic surveys varied from eight to forty-four per season, while the number found during diurnal surveys of 136-175 sites annually ranged from zero to thirty-three. Although recruitment occurred in most years the population did not recover to that previously found in 2010-2012. The lack of recovery was influenced by drought, wildfire and a continual loss of habitat from urban developments. Large adult females were seen each survey beside Rotten Creek or nearby ponds suggesting the adult population overwinters within the catchment of this creek and disperse down this catchment to Brundee Swamp to breed in spring. The results from six years monitoring indicate the Crookhaven L. aurea population has not recovered in abundance and distribution since 2010-2012. The three most abundant species of frog Litoria fallax, Litoria peroni and Limnodynastes peroni were also analysed for site preference and population variations over the survey.

The Sound of Water: sensing a wetland intervention through interactive environmental audio

The Sound of Water ( https://flow-mer.org.au/napnap ) microsite documents an environmental intervention at Nap Nap Swamp, a wetland in the western reaches of Australia’s Murrumbidgee River. A collaboration between a designer (Whitelaw) and an ecologist (Wassens), it was supported by the Commonwealth Environmental Water Office. We use audiovisual data storytelling to engage audiences with Nap Nap as it transitions from a dry to wet state. Focusing on a 9-day period in mid-2020, we combine audio and hydrological data to show the ecosystem’s response to a managed environmental flow, narrating this change through the wetland’s charismatic frog species, including the threatened Southern Bell Frog. In this paper we reflect on the technical and creative contributions of the project in visualising environmental audio, as well as its significance for wider practice. We highlight the value of creatively re-purposing ecological data and the importance of multi-stakeholder networks, and we argue that our celebration in this project of environmental management, intervention and care should be a key concern for future digital ecologies practices.

Deteriorating waterways: The effect of nitrate pollution on the development and physiology of the endangered southern bell frog (Litoria raniformis)

Nitrogen-based fertilizers can increase agricultural yields and crop quality, but this comes at the risk of contaminating nearby waterways. Nitrate is the most stable and abundant form of inorganic nitrogen in the environment and chronic exposure can impair performance and fitness in aquatically respiring species. But it remains unknown if these impairments are linked to disruptions in energy homeostasis. Here, we investigated the energetic cost of living in nitrate contaminated waters during early, energy-limited, larval life stages in the endangered southern bell frog (Litoria raniformis). We hypothesised that chronic nitrate exposure during development would increase energetic costs, evidenced by reductions in growth rates and body sizes, and elevations in routine heart rate (RHR) and routine metabolic rate (RMR). Following hatching, larvae were exposed to one of three nitrate treatments (0, 25 and 50 mg NO3−L−1) for 12 weeks, and survival, growth, RHR, and RMR were measured. Survival rates were similar across all treatments. Nitrate exposure caused a reduction in growth rates, resulting in larvae with significantly smaller body sizes. Compared to controls, nitrate-exposed larvae were 12% and 18% smaller in total length in the 25 and 50 mgNO3−L−1 treatments, respectively. However, RHR and RMR were independent of nitrate exposure, indicating that the ‘cost of living’ was similar across treatments. Observed growth reductions were therefore independent of RHR and RMR, suggesting other mechanisms were involved. Taken together, these results highlight the vulnerability of L. raniformis to nitrate during early life and suggest that the application of nitrogen-based fertilizers near critical aquatic habitats will be harmful.

A Novel Strategy for the Design of Aurein 1.2 Analogs with Enhanced Bioactivities by Conjunction of Cell-Penetrating Regions.

The rational design modification of membrane-active peptide structures by introducing additional membrane-penetrating regions has become a good strategy for the improvement of action and potency. Aurein 1.2 (GLFDIIKKIAESF-NH2) is a multifunctional antimicrobial peptide isolated from the green and golden bell frog, Litoria aurea, and the southern bell frog Litoria raniformis skin secretions. Its bio-functionality has been widely investigated. However, its lack of a potent action failed to provide aurein 1.2 with a competitive edge for further development as a therapeutic agent for clinical use. Herein, aurein 1.2 was chosen as a template for rational modification to achieve a more potent bio-functionality. KLA-2 (GLFDIIKKLAKLAESF-NH2), which a double KLA region inserted into the sequence, presented a 2-16-fold enhancement of antimicrobial activity, a 2-8-fold greater anti-biofilm activity (including biofilm prevention and eradication), and a 7-fold more potent anti-proliferation activity and hence was regarded as the most broad-spectrum active peptide. Additionally, with respect to antimicrobial activity, the IIKK-modified analog, IK-3 (GLFDIIKKIIKKIIKKI-NH2), also demonstrated a potent enhancement of activity against various pathogens, exhibiting a 2-8-fold enhanced activity compared to the parent peptide. Moreover, the selectivities of KLA-1 and KLA-2 were enhanced significantly. In conclusion, peptide modification, through the introduction of additional membrane penetrating regions, can increase both the potency and activity spectra of natural template peptides, making them suitable candidates for new drug development.

Fluorescence correlation spectroscopy studies of antimicrobial peptide binding to phospholipid vesicles.

Antimicrobial peptides (AMPs) perform an essential part of the innate immune defence of all organisms and are potential candidates for last-resort antibiotics. Aurein 1.2 is a natural AMP from the skin secretions of the Australian bell frog. The molecular details underpinning the mechanism of action, specificity and selectivity of this AMP are mostly unknown. We used fluorescence correlation spectroscopy (FCS) to assess the binding and membrane modulating properties of fluorescently labeled Aurein 1.2 and its specific mutants with lipid vesicles of different physicochemical characteristics. Our results indicate that aurein 1.2 binds non-specifically to all kinds of membranes; however, the presence of specific lipid species can prevent membrane disruption. We note the general absence of “carpet-like” disruption patterns; instead, a strong membrane modulating activity was observed. We confirmed that the FCS technique produces accurate binding measurements for nanomolar peptide concentrations, which is almost impossible with other techniques for studying the interaction of AMPs with lipid membranes. We suggest that our results could guide the design of membrane-active AMPs.

Tadpole fingerprinting: Using tail venation patterns to photo‐identify tadpole individuals of a threatened frog

AbstractTraditional methods for identifying individual amphibians in capture–mark–recapture (CMR) studies have been primarily confined to post‐metamorphic stages, using artificial markers that come with a variety of limitations. An alternative that may open CMR studies to earlier life stages involves the use of a species' natural external markers in photo‐based identification. In this study, we investigated whether it was possible to distinguish tadpoles of the threatened green and golden bell frog (Litoria aurea) at the individual level based on tail venation patterns. We collected photographs of the tails of captive‐raised tadpoles using a smartphone over a 4‐week period. This photo‐library was used to create an electronic survey where participants were asked to detect matches for query tadpoles from small image pools. We found that most participants agreed on a match for each query, with perfect consensus achieved for most queries (83%). We detected a 14% decline in perfect consensus when participants were asked to match images of tadpoles separated by longer time intervals, suggesting that it is more difficult to visually identify recapture events of L. aurea tadpoles over extended periods due to changes to tail appearance. However, consensus was obtained by participants for all queries, with all matches verified as being correct by the primary researcher. The strength of agreement among participants with no prior experience in matching tadpole tails suggests that there is sufficient inter‐individual variation in this feature for individuals to be manually identified. We thus propose that photo‐identification is likely to be a valid, non‐invasive technique that can be used for short‐term studies on tadpole populations that display tail venation. This offers an alternative to artificial markers that may not allow for individual identification, while also opening up tadpole monitoring programmes to citizen scientists who can be recruited online to process image data from home.

Molecular systematic analysis demonstrates that the threatened southern bell frog, Litoria raniformis (Anura: Pelodryadidae) of eastern Australia, comprises two sub-species

In south-eastern Australia, the pelodryadid Litoria aurea Group (sensu Tyler & Davies 1978) comprises three species: Litoria aurea (Lesson, 1829), Litoria raniformis (Keferstein, 1867), and Litoria castanea (Steindachner, 1867). All three species have been subject to declines over recent decades and taxonomic uncertainty persists among populations on the tablelands in New South Wales. We address the systematics of the Group by analysing mitochondrial and nuclear DNA sequences to assess divergence in the Litoria raniformis from across its current range in New South Wales (NSW), Victoria, South Australia (SA) and Tasmania. We also included samples of Litoria castanea from a recently rediscovered population in the southern tablelands of NSW. Our phylogenetic and population genetic analyses show that Litoria raniformis comprises northern and southern lineages, showing deep mitochondrial DNA sequence divergence (7% net average sequence divergence) and can be diagnosed by fixed allelic differences at more than 4,000 SNP loci. Samples of the northern lineage were collected from the Murray-Darling Basin while those of the southern lineage were collected from south-eastern South Australia, southern and south-eastern Victoria and Tasmania. Analysis of the morphology and bioacoustics did not unequivocally delineate the two lineages. The presence of a hybrid backcross individual in western Victoria at the northern margin of the southern lineage, leads us to assign sub-species status to the two lineages, L. r. raniformis for the northern lineage and L. r. major for the southern lineage. Our data do not unequivocally resolve the taxonomic status of L. castanea which will require molecular genetic analyses of museum vouchers from those parts of the range where L. castanea and L. raniformis are no longer extant. Our data also suggest that human mediated movement of frogs may have occurred over the past 50 years. Our genotyping of vouchers collected in the 1970s from the Mount Lofty Ranges in South Australia detected mitochondrial haplotypes of both sub-species and SNP analysis showed that a single Tasmanian specimen was a backcross with L. r. raniformis ancestry. Movement of L. r. raniformis into Tasmania and both sub-species into the Mount Lofty Ranges are not likely due to passive movements of animals through agricultural commerce, but due to the attractiveness of the species as pets and subsequent escapes or releases, potentially of the larval life stage.

Modeling the effects of water regulation on the population viability of a threatened amphibian

AbstractThe regulation of river systems alters hydrodynamics and often reduces lateral connectivity between river channels and floodplains. For taxa such as frogs that rely on floodplain wetlands to complete their life cycle, decreasing inundation frequency can reduce recruitment and increase the probability of local extinction. We virtually reconstructed the inundation patterns of wetlands under natural and regulated flow conditions and built stochastic population models to quantify the probability of local extinction under different inundation scenarios. Specifically, we explored the interplay of habitat size, inundation frequency, and successive dry years on the local extinction probability of the threatened southern bell frog Litoria raniformis in the Murray River floodplains of South Australia. We hypothesized that the changes to wetland inundation resulting from river regulation are driving L. raniformis declines in this semiarid system. Regulation has reduced the inundation frequency of essential habitats below critical thresholds for the persistence of many fresh water‐dependent species. Successive dry years raise the probability of local extinction, and these effects are strongest in smaller wetlands. Larger wetlands and those with more frequent average inundation are less susceptible to these effects. Elucidating these trends informs the prioritization of intervention sites and the frequency of conservation interventions. Environmental water provision (through pumping or the operation of flow‐regulating structures) is a promising tool to reduce the probability of breeding failure and local extinction. Our modeling approach can be used to prioritize the delivery of environmental water to L. raniformis and potentially many other frog species.

Pump my wetland: potential benefits of using water pumps fitted with large-mesh screens to conserve anurans in regulated floodplain environments

Context Water pumps fitted with filtering screens are effective for delivering water to floodplain environments and excluding large-bodied exotic fish; yet, the benefits to wetland fish and anurans are unknown. Aims To quantify fish and tadpole responses to refilling wetlands with water pumps fitted with large-mesh screens following drawdown v. overland reconnections in the mid-Murrumbidgee region of New South Wales. Methods Frog and fish communities were compared between wetlands under managed inundation and overland reconnections by using PERMANOVA, and non-metric multidimensional scaling was used to evaluate community divergence between watering strategies. Classification and regression trees were used to identify thresholds in explanatory variables and predicted threshold responses in fish and tadpole abundance. Key results Fish and tadpole communities differed in relation to watering strategies. Managed inundation resulted in a higher abundance of tadpole species and one native fish, whereas overland reconnections resulted in a high abundance of exotic fish species and fewer tadpoles. Water depth was a driver of tadpole abundance in two species, including the threatened southern bell frog (Litoria raniformis). Conclusions and implications Using filtered pumps with large-mesh screens to deliver water to wetlands of high conservation value may be an effective strategy for reducing large-bodied exotic fish and enhancing frog and fish populations in regulated floodplain systems.

Frog Reproduction and Community Structure in relation to Water Attributes: Setting the stage to understand effects of Climatic Variables and Climate Change

ABSTRACT As amphibians have declined more than other vertebrates and are important environmental bio-indicators for aquatic ecosystems, we must understand how attributes of such ecosystems affect individual frogs, populations, and multi-species communities. For aquatic-breeding frogs, pond physical/chemical properties influence all life-stages and therefore populations, species, and communities. However, studies have focussed on tadpoles, considered few water variables, and not considered relationships between water attributes and frog populations or communities. Inter-specific differences in how water attributes affect tadpole populations, and hence possibly adult choice of breeding site, should reflect habitats where different species occur, but has been little investigated. We studied the only frog species on Broughton Island, off the east coast of Australia: the threatened Green and Golden Bell Frog Litoria aurea (GGBF); and the widespread and abundant Striped Marsh Frog Limnodynastes peronii (SMF). Suitability of pond breeding habitat, measured by encounter rates during 57 visits over 17 years with different life stages, depended on depth, salinity, pH and temperature, with responses by the two species in essentially opposite directions. For both species, encounter rates increased with increasing depth and with decreasing salinity. Encounter rates peaked at neutral to alkaline pH for GGBF (i.e., 6.8 to 8.0 or higher) and acidic pH for SMF (i.e., 5.5 to 6.0). As water temperature increased, encounter rates increased for GGBF and decreased for SMF. Frog community structure depended on average pond temperature and how it changed over time. If recorded temperature, averaged over the year, was less than 22°C or declined to below this level, the GGBF population, as indexed by numbers of adults observed and occurrences of earlier life stages, was low or declined, while the SMF population was high or increased. This threshold yearly average temperature translates into a required temperature at onset of spring breeding for the GGBF of about 20°C. The GGBF population on the island has declined since 1998, when our study began, due to increased aquatic vegetation and consequent decline in water temperature in major breeding ponds. As ponds are small, manual vegetation removal should reverse the trend. A comprehensive understanding of the biological effects of climate change, past and future, can now be pursued.

Genetic evidence for polyandry in the threatened green and golden bell frog.

Identifying which species exhibit polyandry may lead to further insights into evolutionary biology and social behaviour. However, confirming polyandry can be difficult. High-resolution genetics provides a useful means to gain evidence. Although the threatened Pelodryadid frog, the green and golden bell frog Litoria aurea, has been subject to numerous ecological studies, there is uncertainty surrounding its reproductive ecology. Polyandry has not been formally identified in L. aurea or any species within the Pelodryadidae family. We aimed to identify if there was genetic evidence of polyandry in a population occurring in a wetland complex on Kooragang Island, New South Wales. To accomplish this, we collected genetic samples of tadpoles within the same size cohort about 20-30days after explosive breeding events. Genotypes of 14 females, nine males and 70 tadpoles were analysed with COLONY (1988 single nucleotide polymorphisms after filtering) to identify parentage, full-siblings and half-siblings. We found support for the hypothesis that L. aurea is polyandrous. Based on previous observations of multi-male matings and the narrow time periods that breeding occurred in, it is likely this species exhibits simultaneous polyandry. We discuss these results in regards to behavioural adaptive processes and avenues for further research.

Improving breed‐and‐release programmes in the face of a threatening pathogen, Batrachochytrium dendrobatidis

Abstract As the proportion of threatened species increases, so too does the need for effective conservation strategies. In response, captive breed‐and‐release and habitat mitigation programmes are two conservation actions that are increasing in use and effectiveness. Success of these programmes is frequently hampered by the continued presence of threatening processes. In the case of amphibian reintroductions, a key threatening process that is difficult to eliminate is the deadly fungal pathogen, Batrachochytrium dendrobatidis (Bd). This pathogen is the proximate cause of decline for the threatened green and golden bell frog, Litoria aurea, and has contributed to the failure of previous breed‐and‐release programmes of this amphibian. To investigate whether is it possible to establish a captive‐bred population of L. aurea that could persist in the presence of Bd, a breed‐and‐release programme was conducted in a created habitat that included increased salinity to inhibit fungal growth rates, exclusion of potential reservoir hosts and source animals bred from parents ‘experienced’ with the strain of Bd present in the release environment. The population persisted in the created habitat for more than 4 years (the timescale of monitoring) but suffered higher infection levels compared with nearby extant populations of L. aurea. These infections significantly reduced apparent survival. Infection dynamics were linked to temperature, host density in the previous season, and size and age of the host, and these factors differed from those in extant populations and are likely to have contributed to the high levels of Bd infection at the created site. This article discusses how it may be possible to manipulate these factors to improve the success of future breed‐and‐release programmes, and recommends the construction of warm water bodies and a strategy of prioritizing the release of fewer, large propagules of high body condition and mixed‐age class, over large numbers of younger, smaller animals.