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The authors address two commentaries on their paper about the benefits and costs of using lungworm as a biological control agent for invasive toads in Australia. According to them, the commentaries suggest that they are too optimistic about the effectiveness of lungworm dissemination for toad control. The authors argue that lungworm can severely depress survival, endurance and growth in metamorph cane toads even under favorable laboratory conditions.

It is becoming increasingly clear that species of smaller body size tend to be less vulnerable to contemporary extinction threats than larger species, but few studies have examined the mechanisms underlying this pattern. In this paper, data for the Australian terrestrial mammal fauna are used to ask whether higher reproductive output or smaller home ranges can explain the reduced extinction risk of smaller species. Extinct and endangered species do indeed have smaller litters and larger home ranges for their body size than expected under a null model. In multiple regressions, however, only litter size is a significant predictor of extinction risk once body size and phylogeny are controlled for. Larger litters contribute to fast population growth, and are probably part of the reason that smaller species are less extinction-prone. The effect of litter size varies between the mesic coastal regions and the arid interior of Australia, indicating that the environment a species inhabits mediates the effect of biology on extinction risk. These results suggest that predicting extinction risk from biological traits is likely to be a complex task which must consider explicitly interactions between biology and environment. [ABSTRACT FROM AUTHOR]

Refuges play a critical role protecting species against the effects of climate change. Managing high priority refuges could improve species resilience and facilitate dispersal during periods of environmental change. In this study, we identified drought refuges in semi‐arid Australia for a threatened bird, the malleefowl Leipoa ocellata. Using a Poisson regression model, we quantified the effect of remotely sensed vegetation indices, rainfall, soil moisture and site characteristics on malleefowl breeding activity at 144 sites surveyed from 2000 to 2017 during and after drought. We tested the effect of two vegetation productivity indices on malleefowl breeding activity – the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI) – averaged across three temporal and three spatial scales during the mound building and incubation stage of the breeding cycle. We found that NDVI and EVI were better predictors of malleefowl breeding activity than soil moisture and winter rainfall. The model with the lowest Akaike information criterion value contained NDVI averaged over 3 months (June–August) and a 1‐km radius. Malleefowl breeding activity had a strong positive association with NDVI (0.42 ± se 0.03) and a negative association with slope (−0.34 ± se 0.03) and vegetation patch size (−0.23 ± se 0.02). We found the proportion of refugia (top 20% of predicted breeding activity) in protected areas was highly variable, decreasing from 42% in an extreme wet year (2011) to 14% in an extreme drought year (2007). Expanding the reserve network to include refugia predicted to occur in the south of semi‐arid Victoria could improve resilience of malleefowl to climate change. We demonstrate how remotely sensed vegetation indices combined with citizen science data can identify where to protect native vegetation with high, stable productivity. Our approach could be applied to a broad range of species in semi‐arid regions vulnerable to climate change. [ABSTRACT FROM AUTHOR]

The author comments on a paper by L. Pizzatto and R. Shine on the use of lungworm parasite as a biological agent for controling invasive cane toads in Australia. According to him, Pizzatto and Shine show that this parasite of the cane toad can infect native green tree frogs, Litoria caerulea, with no evident detrimental effect on the frogs. He says that this approach is intriguing. He stresses that a truly effective and safe integrated toad management program still seems elusive.

The author comments on a paper the examines the benefits and costs of using a lungworm parasite to control invasive toads in Australia. The author is skeptical about the idea that biocontrol would be effective in this case. According to him, other tree frog species, such as Litoria splendida, is affected by the lungworm, pointing out that spill over of the parasite is a serious concern. He concludes that the lungworm as a biocontrol agent appears to provide little benefit.

Understanding the current population size of small, spatially aggregating populations of species is essential for their conservation. Reliable estimates of the effective population size (Ne) can be used to provide an early warning for conservation managers of the risks to genetic viability of small populations. Critically endangered, migratory swift parrots Lathamus discolor exist in a single panmictic population in Australia. In their Tasmanian breeding range, they are at severe risk of predation by introduced sugar gliders, exacerbated by deforestation. We used three genetic approaches to estimate Ne using DNA samples genotyped by microsatellite markers and existing life‐history data of swift parrots. Based on all samples, we revealed small contemporary Ne estimates across methods (range: 44–140), supporting the need to urgently address threatening processes. Using the 0.5 Ne/N ratio calculated from demographic data suggests that the minimum potential contemporary population size is below 300 individual swift parrots. This is considerably lower than the published estimates derived from expert elicitation, and accords with modeled estimates of extinction risk in this species. Our study has important implications for other threatened species with unknown population sizes and demonstrates that by utilizing available genetic data, reasonable estimates of Ne can be derived. [ABSTRACT FROM AUTHOR]

Vegetation clearing has been implicated as a major contributor to biodiversity loss. It therefore stands to reason that developers should face a regulatory requirement to assess potential impacts and to avoid, mitigate and compensate for loss of vegetation wherever proposed infrastructure developments impact on vegetation considered to be habitat for threatened species. Environmental Impact Assessments (EIA) rely on accurate information to describe the distributions of threatened species within the footprint of proposed infrastructure developments, which is critical to ensuring appropriate mitigation of potentially deleterious impacts on these populations. EIA survey guidelines seek to determine species' presence accurately, while acknowledging the limits imposed by time and budget constraints. As such, the EIA guidelines may recommend: (1) stratifying the landscape based on previous knowledge of habitat variables relevant to a species; and (2) targeting survey effort to strata with high probability of occupancy. Here, we use koala Phascolarctos cinereus surveys as a case study to explore the extent to which application of EIA guidelines result in accurate occupancy estimates. We compared the presence/absence distribution across one landscape survey and three EIA surveys, and found that koala occupancy was not well predicted by koala habitat criteria widely used to inform sampling design. In the context of EIA, we provide an example of how targeting survey effort to strata with high probability of occupancy risks misrepresenting true occurrence patterns. A general issue with survey designs that rely on previous knowledge is that they self‐reinforce erroneous assumptions. Our findings stand as a warning that EIA might neither quantify the impact of proposed infrastructure developments adequately, nor inform the ensuing mitigation measures. Threatened species' protection in the face of infrastructure development will require new approaches to EIAs to ensure that providers are enabled to undertake comprehensive environmental surveys capable of detecting priority species. [ABSTRACT FROM AUTHOR]

The conversion of agricultural land to forest plantations is a major driver of global land-use change, and considering that large portions of the planet are covered by forest plantations, understanding their impact on biodiversity is a research priority. The aim of our study was to quantify the long-term response of two lizard species to the transformation of the matrix surrounding remnant habitat patches (from agricultural land to pine plantations). We used a large-scale (115 sites), long-term (16 years) fully replicated and controlled landscape scale 'natural experiment' (the ' Nanangroe experiment', Australia) to compare the response of lizard populations to plantation establishment. The study entailed detailed surveys of reptiles in 50 eucalypt patches surrounded by maturing pine P inus radiata plantations ( treatments) and populations inhabiting 55 eucalypt patches surrounded by grazing land ( controls). We found that the eastern three-toed earless skink H emiergis talbingoensis was advantaged by the establishment of the pine plantations (increasing colonization of eucalypt patches embedded within plantations). In contrast, we found that the southern rainbow skink C arlia tetradactyla was negatively affected by surrounding areas of maturing plantations. Thus, our results show that plantations acted as a barrier for one species and increased connectivity for the other. We suggest that leaving areas of land devoid of pines between remnant eucalypt patches may enhance the connectivity for species that respond negatively to plantation establishment while maintaining the beneficial increase in connectivity for others. [ABSTRACT FROM AUTHOR]

Invasive cane toads Rhinella marina have had severe ecological impacts in Australia. The toads brought with them a native-range ( New World) parasitic lungworm Rhabdias pseudosphaerocephala that can kill metamorph toads, stunt the growth and reduce the stamina of both metamorph and adult toads. No cases of natural transfer to native frogs have been reported, but experimental studies have shown that metamorphs of one native anuran (the green tree frog Litoria caerulea) are capable of maintaining lungworm infections, without reducing frog survivorship. Thus, we might be able to increase the distribution of the lungworm, and its prevalence in toads, by deliberately infecting green tree frogs. In laboratory studies, we found that the toad lungworm had no detectable effects on growth or survival of adult green tree frogs. Worms that developed in the lungs of the frogs, passed out in the frog's faeces, and were able to infect toads, reducing their stamina. Synthesis and applications: Our results are encouraging for the possibility of using the green tree frog as a Typhoid Mary (to carry parasites to invasive toads without itself suffering any ill effects due to the parasite's presence), but this management approach raises significant issues of statistical power (we can never be sure that lungworms have absolutely no effect on frog viability) and animal welfare (are we justified in infecting the native species to help control the invasive species?). [ABSTRACT FROM AUTHOR]

The mechanisms by which invasive species spread through new areas can influence the spatial scale of their impact. Although previous research has focused on ‘natural’ dispersal rates following initial introductions, human-aided inadvertent dispersal by ‘stowaways’ on commercial and domestic transport is thought to be a major contributor to long-distance dispersal. Few data exist to support this assumption. Cane toads Bufo marinus were introduced to north-eastern Australia in 1935, and have since dispersed rapidly through the tropics. Based on information accumulated by community groups in Sydney, 400 km south of the cane toads' current Australian distribution, we document high rates of translocation (at least 50 toads arriving in Sydney per year). Most toads were translocated on commercial truck transport carrying landscaping and building materials from the current range of the cane toads in New South Wales and Queensland, and resulted in highly clumped locations of toad arrival reflecting primary truck transport destinations. Most introductions involved single toads (68 of 102 translocation events), but some introductions involved two to 19 animals. Adults of both sexes were represented equally but juveniles were rarely detected. High rates of translocation of adult toads of both sexes suggest that the eventual distribution of cane toads in Australia may be limited by the animals' bioclimatic tolerances rather than by an inability to reach suitable habitats, even in areas far distant from the toads' current range. [ABSTRACT FROM AUTHOR]

The cane toad Bufo marinus has been migrating westward across northern Australia since its introduction as a biological control agent in 1935. It has been implicated in the widespread decline of many native frog-eating predators. To investigate the impacts of this invasive species on native predatory reptiles, annual surveys were conducted from 2001 to 2007 to document variation in the relative abundances of three varanid lizards ( Varanus mertensi, Varanus mitchelli and Varanus panoptes) and one crocodile Crocodylus johnstoni species known to consume toads. In addition, the indirect effects of this variation on one agamid lizard Amphibolurus gilberti, a known prey item of V. panoptes, were also examined. Surveys were performed at two sites in northern Australia before and after the arrival of B. marinus. Significant declines in the relative abundances of all three species of varanid lizard were observed following toad arrival. Declines in the abundance of V. panoptes, V. mitchelli and V. mertensi at the two sites ranged 83–96, 71–97 and 87–93%, respectively. In contrast, A. gilberti increased by 23–26%; whereas there were no significant population-level declines in C. johnstoni despite observations of individual effects (i.e. several dead crocodiles with B. marinus in their stomachs). These findings suggest population-level changes in Australian lizards caused by an invasive species. [ABSTRACT FROM AUTHOR]

Interactions between short-beaked common dolphins Delphinus delphis and the fishing industry of South Australia (SA) have lead to serious concerns over the long-term viability of the local dolphin population. Common dolphins are gregarious animals with high vagility and are expected to display limited genetic differentiation over large spatial scales. Here, we investigate population genetic structure of southern Australian common dolphins using mitochondrial DNA control region sequences and seven microsatellite markers. We found unexpected levels of genetic differentiation for short-beaked common dolphins over a distance of ∼1500 km. Although no genetic structure was observed in common dolphins along the coast of SA, we detected marked differentiation between dolphins from SA and south-eastern Tasmania, suggesting a minimum of two genetic populations in southern Australia. We hypothesize that the ephemeral distribution of small pelagic fish enhances movement and dispersal between dolphin groups at a local level. However, clear differences in water temperature, habitat features and fish abundance between SA and Tasmania may contribute to the contemporary isolation observed between dolphin populations. Our findings have important consequences for developing conservation management strategies, because SA has the largest purse-seine fishery by weight in Australia, and substantial numbers of fatal common dolphin interactions have occurred. In 2004/2005 alone, an estimated 1728 common dolphins were encircled and 377 died over a 7-month period. If these impacts lead to a reduction in population size, it is unlikely that dolphins from the adjacent south-eastern Tasmanian population will replace the lost individuals. Recommendations for assessing the impacts of the fishery are presented. The information herein may also have implications for fisheries–marine mammal interactions in coastal and neritic habitats in other areas of the world. Moreover, we demonstrate that a species commonly thought to be wide ranging can show an unexpected degree of genetic differentiation. [ABSTRACT FROM AUTHOR]

Tree cavities are an important shelter site for a variety of vertebrate species, including birds, reptiles and mammals. Studies indicate that in most taxa favoured tree hollows are those in larger trees and higher from the ground, generally thought to be related to decreased predation risk and a more optimal thermal environment. However, neither of these ideas has been tested definitively. Here, we investigate the microclimate of daytime den sites in tree hollows of common brushtail possums in tropical northern Australia. We compare tree and hollow characteristics of dens known to be used by possums, and those not known to be used, to determine whether possums choose trees with microhabitats with a more favourable daytime microclimate. Possums chose to den in tree hollows which were on average 1.6 °C cooler during the day, and were more buffered from temperature extremes, than other potential den locations. Important factors explaining daytime temperatures between hollows included height of the hollow, entrance width and tree diameter. Tropical arboreal marsupials have been identified as being particularly vulnerable to climate change and there are calls to identify and preserve natural refuges, such as tree hollows, which could buffer them from extreme temperatures. Our results highlight the value of older, larger hollow-bearing trees as refuges from extreme temperature, the importance of which may become critical for some temperature-sensitive species under the combined effects of continuing habitat loss and climate change. [ABSTRACT FROM AUTHOR]

Exotic species that invade remote islands, usually following human settlement, have had catastrophic effects on native biota. However, on islands it is increasingly feasible to eradicate key exotic species allowing extant native species to recover in situ or to return naturally. The practice of marooning threatened species on islands where the threat is absent, irrespective of whether the threatened species once occurred on the island, is well established. However, less focus has been given to the ‘island’ as the management unit on which to return extirpated species or related surrogates for extinct species. We use the example of Lord Howe Island as a case study to explore options for island restoration should the remaining critical exotic pests (rodents and perhaps owls in this case) be eradicated as planned. Lord Howe Island, in the south-west Pacific Ocean, is remote, biologically diverse, has a high degree of endemism, and was only discovered by humans in 1778. Consequently, the original and exotic biota and their interactions are all better known than for many islands with a more ancient human history. Two species of plants, nine terrestrial birds, one bat and at least four invertebrates have been lost from the island since 1778. One plant and two invertebrates could be returned as conspecifics. One plant and all the terrestrial birds that are extinct could be replaced by closely related species from elsewhere in the Pacific Ocean. Decisions on replacing extinct species with surrogates should be based on the taxonomic relatedness of the candidates for reintroduction: the same species before subspecies before genera, with functional replacement being a further filter on candidates that are not the same species. In our opinion, taxa with functional equivalence but without taxonomic relatedness would not be acceptable candidates for reintroduction. [ABSTRACT FROM AUTHOR]

The ways in which invasive organisms influence native ecosystems remain poorly understood. For example, feral cane toads Bufo marinus have spread extensively through tropical Australia over the last 70 years, but assessments of their ecological impact remain largely anecdotal. We conducted experimental trials to examine the effect of cane toad presence on invertebrate fauna in relatively small (2.4 × 1.2 m) outdoor enclosures on a floodplain near Darwin in the wet–dry tropics. Toads significantly reduced invertebrate abundance and species richness, but only to about the same degree as did an equivalent biomass of native anurans. Thus, if toads simply replaced native anurans, the offtake of invertebrates might not be substantially different from that due to native anurans before toad invasion. However, our field surveys suggest that toads cause a massive (fourfold) increase in total amphibian biomass. The end result is that cane toads act as a massive nutrient sink in the floodplain ecosystem because they consume vast numbers of invertebrates but (unlike native frogs) are largely invulnerable to predation by frog-eating predators. [ABSTRACT FROM AUTHOR]

In this article, the author discusses reservoir of Batrachochytrium dendrobatidis in Australia. It mentions the use of disease mitigation strategies such as culling, environmental disinfection and immunization, for protection of amphibians from decline. it also mentions importance of amphibian chytridiomycosis as a threat to biodiversity.