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Habitat destruction is a key threatening process for amphibians. Modified or anthropogenic waterbodies can be used to compensate for habitat loss, with several amphibian species utilising created or modified waterbodies. We measured usage of anthropogenic/modified waterbodies by adult and tadpole frog species, including threatened species, in coastal wallum habitat in eastern Australia. Nine road trenches/ditches, 8 artificial ‘lakes', 6 golf course waterbodies and 13 natural waterbodies were surveyed for frog adults and tadpoles during the summer/spring period 2011–2012. Additionally, we examined the relationship between frog assemblages and environmental factors (water chemistry, aquatic predators, vegetation types), focusing on Litoria olongburensis and Litoria fallax . Frog species richness differed between waterbody types, with two of three threatened frog species present in both natural and anthropogenic/modified waterbodies. The frog assemblage was influenced by pH, turbidity, salinity and percentage cover of certain vegetation types. Measured abundance of L . olongburensis adults and tadpoles were highest in natural waterbodies with high sedge density and low pH. The measured abundance of adult L . fallax was highest within artificial lakes. We conclude that differences in water chemistry and vegetation density can affect the amphibian assemblage within these environments. Therefore, effective conservation of all frog species would be enhanced by conserving a variety of waterbody types. However, natural waterbodies are more likely to be used by threatened species and the conservation of these waterbodies provides the best conservation outcomes. Where habitat offsets may be required, environmental managers should critically assess the quality of constructed habitat for specialist frog species including those associated with acidic, oligotrophic environments.

More than a third of the world's amphibian species are listed as Threatened or Extinct, with a recent assessment identifying 45 Australian frogs (18.4% of the currently recognised species) as ‘Threatened' based on IUCN criteria. We applied structured expert elicitation to 26 frogs assessed as Critically Endangered and Endangered to estimate their probability of extinction by 2040. We also investigated whether participant experience (measured as a self-assigned categorical score, i.e. ‘expert' or ‘non-expert') influenced the estimates. Collation and analysis of participant opinion indicated that eight species are at high risk (>50% chance) of becoming extinct by 2040, with the disease chytridiomycosis identified as the primary threat. A further five species are at moderate–high risk (30–50% chance), primarily due to climate change. Fourteen of the 26 frog species are endemic to Queensland, with many species restricted to small geographic ranges that are susceptible to stochastic events (e.g. a severe heatwave or a large bushfire). Experts were more likely to rate extinction probability higher for poorly known species (those with in-situ population refuges to alleviate the impacts of disease and climate change.

A review of the current conservation status of Australian amphibians was recently completed as part of a World Conservation Union (IUCN) sponsored Global Amphibian Assessment (GAA). Fifty of 216 amphibian species (23%) in Australia are now recognized as threatened or extinct in accord with IUCN Red List Categories and Criteria. Here we report on the categories and criteria under which individual species qualified for listing and provide a summary of supporting information pertaining to population and distribution declines. Major threatening processes contributing to listing of species are also reviewed.

Rainforest frogs are classified into nine ecological guilds based on features of reproduction, habitat use, temporal activity, microhabitat and body size. The largest ecological differences are between the microhylid frogs and the rest of the frog species. Within the non–microhylids, there are two primary groups consisting of (i) regionally endemic rainforest specialists, and (ii) a more ecologically diverse group of species that are less specialized in their habitat requirements. Most of the regionally endemic rainforest specialists, which includes species in three ecological guilds, have declined or gone missing in recent years. Multivariate analyses of the ecological characteristics of these species show that it is not a single characteristic that isolates those species that have declined from those which have not. The guilds that have undergone significant population declines in the Wet Tropics are all characterized by the combination of low fecundity, a high degree of habitat specialization and reproduction in flowing streams. These results have important implications for the determination of the causal factors in the unexplained global decline of many amphibian species.

AbstractThe relationship between the distribution of predators (fish, odonates and water beetles) and prey assemblages (amphibian larvae) was investigated in the tropical rainforest of central Amazonas, Brasil. The anuran community uses a variety of waterbodies for reproduction, ranging from streams and streamside ponds to isolated forest ponds. Predators in this system include fish in streams and streamside ponds, and invertebrates (primarily odonate naiads and beetles) in forest ponds. Tadpole species richness and assemblage structure were related to fish density and species richness. No relationships between tadpole assemblages and abiotic pond characteristics were detected. The presence offish explained much of the variation in both species composition and species richness within and among ponds. Some species of tadpole were consistently found to coexist with high densities of fish. Path analyses suggest that while fish have a strong direct effect on tadpole associations and species richness, they also have an indirect effect through invertebrate predators (odonate larvae and coleopteran beetles). Prey survival-strategies such as palatability and behaviour may explain how tadpole species composition is affected by predators at the community level. These findings suggest that the observed patterns of habitat use by larval anurans may be structured in response to the distribution of key predators (fish) in this system.

Terrestrial oviposition with free-living aquatic larvae is a common reproductive mode used by amphibians within the central Amazonian rainforest. We investigated the factors presently associated with diversity of microhabitats (waterbodies) that may be maintaining the diversity of reproductive modes. In particular, desiccation, predation by fish, competition with other anurans and water quality were examined in 11 waterbodies as possible forces leading to the evolution of terrestrial oviposition. Predation experiments demonstrated that fish generally do not eat anuran eggs, and that predacious tadpoles and dytiscid beetle larvae are voracious predators of anuran eggs. The percentage of species with terrestrial oviposition was only weakly correlated with the occurrence of pond drying, pH and oxygen concentration, suggesting that anurans in this tropical community are able to use the range of water quality available for egg development. There was a tendency for terrestrial oviposition to be associated with the number of species of tadpoles using the waterbody, but we consider this to be spurious as there was no obvious competitive mechanism that could result in this relationship. The percentage of species with terrestrial oviposition was significantly positively related to our index of egg predation pressure, and negatively related to our index of fish biomass. Egg predation pressure was also negatively related to the index of fish biomass. These results allow us to discount as improbable the hypothesis that predation by fish on anuran eggs was an important selective pressure leading to terrestrial oviposition in this community. The strong positive relationship between terrestrial oviposition and our index of egg predation pressure indicates that these predators have exerted, and are exerting, a significant selective pressure for terrestrial oviposition. The strong negative relationship between the occurrence of fish and the egg predators suggests the surprising conclusion that the presence of fish actually protects aquatic anuran eggs from predation in this tropical system, and allows aquatic oviposition to dominate only in those waterbodies with moderate to high densities of fish. Our results suggest that terrestrial oviposition is a “fixed predator avoidance” trait.

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This investigation showed an ontogenetic shift in the palatability of Bufo marinus tadpoles by measuring consumption of tadpoles at three different developmental stages (newly hatched, intermediate and pre- metamorphic) by an Australian predatory fish, Lates calcarifer (barramundi). A known-palatable tadpole, Limnodynastes ornatus, was used as the control. B. marinus tadpoles at all developmental stages were unpalatable relative to a palatable alternative, with the later stages being the least palatable. Choice experiments further demonstrated that L. calcarifer were able to recognise and choose L. ornatus tadpoles in preference to those of B. marinus. Our experiments demonstrate that at all stages of development, B. marinus tadpoles were unpalatable to L. calcarifer. Contrary to the model proposed by Brodie and Formanowicz (1987), our results suggest an ontogenetic shift in palatability of B. marinus tadpoles to a vertebrate fish predator, with the later stages being less palatable.