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To address uncertainties surrounding the impacts of unprecedented 2019–20 bushfires in south-eastern Australia, we convened a symposium on field-measured impacts on biodiversity for the 2020 Ecological Society of Australia conference. Nine presentations covered a range of studies on plant species and communities, and reptiles and mammals. Here, we summarize the presentations and review other field studies from NSW, some of which are currently unpublished. The impacts were extensive, but results also estimated survival rate perhaps higher than first reported in the media. More than half of individual mammal, reptile and threatened rainforest trees may have survived the fire, though small populations remain very vulnerable to second fire in the near future. Comprehensive understanding of the impacts of these fires requires much more field study, and for the results to be interpreted in the context of the broader fire regime. The symposium was an important early step in that understanding.

In the spring and summer of 2019–2020, the ‘Black Summer’ bushfires burned more than 97 000 km2 of predominantly Eucalyptus dominated forest habitat in eastern Australia. The Black Summer bushfires prompted great concern that many species had been imperilled by the fires. Here, we investigate the effects that fire severity had on the habitat and abundance of a cool climate lizard Eulamprus tympanum that was identified as a species of concern because 37% of its habitat was burnt in the Black Summer bushfires. We quantified habitat structure and the abundance of E. tympanum at sites which were unburnt, burnt at low severity and at high severity 10, 15 and 23 months after the fires. Our classification of fire severity based on scorch height and canopy status corresponded well with the Australian Government Google Earth Engine Burnt Area Map (AUS GEEBAM) fire severity layer. Ten months after the fires, sites burnt at high severity had less canopy cover, more bare ground and less fine fuel than sites burnt at low severity or unburnt sites. The abundance of E. tympanum varied with survey occasion and was greatest during the warmest sampling period and lowest during the coolest sampling period. The abundance of E. tympanum was consistently lower on sites burnt at high severity than sites burnt at low severity or unburnt sites. Our findings show that higher severity fires had a greater effect on E. tympanum than low severity fires. Our results suggest that E. tympanum were likely to have persisted in burnt sites, with populations in low severity and unburnt sites facilitating population recovery in areas burnt at high severity. Our results also suggest that wildfire impacts on E. tympanum populations will increase because the frequency and extent of severe fires are expected to increase due to climate change.

The 2019–2020 Australian megafires were unprecedented in their intensity and extent. These wildfires may have caused high mortality of adult broad-headed snakes Hoplocephalus bungaroides which shelter inside tree hollows during summer. We evaluated the impacts of two high-intensity wildfires (2002 Touga Fire and 2020 Morton Fire) on a broad-headed snake population in Morton National Park, south-eastern Australia. We analysed a 29-year mark–recapture data set to estimate survival rates of adults in years with and without wildfires, and with and without human disturbance to rock outcrops. To examine the short-term effects of fire on occupancy, we analysed presence–absence data collected from 25 sites during 2019 and 2020. Estimates of occupancy were higher for 2020 (0.93 ± 0.09) than for 2019 (0.66 ± 0.14), while detection rates were constant (0.40 ± 0.06). Over the period 1992–2020, the best supported Cormack–Jolly–Seber model was one in which adult survival rates were high and stable (0.81 ± 0.04), but were 23% lower in years when humans disturbed rocks (0.63 ± 0.08). A model in which adult mortality was 20% higher in years with human disturbance and 14% higher in years with wildfires was also supported. Estimates of abundance revealed that the population declined by 34% after the Touga Fire, and 26% after the Morton Fire. Over the 29-year study, the population has declined by 60%. Our results highlight how mortality events from wildfires need to be evaluated in the context of other threatening processes. For this population, the removal of snakes and associated habitat disturbance poses a more serious threat to population viability than infrequent wildfires.

In desert ecosystems, some argue that primary productivity controls vertebrate populations while others contend that predators' top-down effects are under-appreciated. While seldom used to explain population dynamics in desert environments, the exploitation ecosystems hypothesis (EEH) unites bottom-up and top-down processes by conceptualizing how the biomass of plants and consumers vary along spatial productivity gradients in the presence and absence of predators. Here, we test predictions from the EEH along temporal primary productivity gradients, by comparing abundances of an apex predator (dingo) and a large omnivorous flightless bird (emu) on either side of Australia's dingo-proof fence over a nine year period. Where dingo populations were not suppressed by humans, their abundance increased with rainfall in the previous 12 months but did not respond to rainfall where their populations were suppressed. Conversely, emu abundance increased in response to antecedent rainfall where dingoes were rare but showed a negligible response to rainfall where dingoes were common. Our results accord with the EEH by suggesting that dingoes' top-down effects can decouple the linkage between emu populations and primary productivity. More generally, our findings show that top-down effects can have primacy over bottom-up effects for both an apex predator and an omnivorous prey species.

Introduced predators threaten prey species worldwide, but strategies to protect vulnerable wildlife from introduced predators can be expensive, time-consuming, and logistically difficult1,2. Novel conservation strategies that reduce predation affordably and efficiently must be explored. ‘Headstarting’ is one such strategy, whereby prey are isolated from predators only during the critical early life stage before being returned to the wild, thus improving juvenile survivorship and recruitment to contribute to an increase in population growth3. Headstarting is a particularly useful conservation strategy for species facing higher levels of a threatening process during only the early part of their life history when mortality rates are higher, and has demonstrably improved conservation outcomes for birds and marine species3,4. Here we report findings from the first known headstarting program for a terrestrial mammal, the endangered bridled nailtail wallaby (Onychogalea fraenata) at Avocet Nature Refuge (henceforth ‘Avocet’) in Queensland, Australia.

Predation is a key factor contributing to the failure of reintroductions of vertebrates but there is variation in predation risk between individuals. Understanding the traits that render some animals less susceptible to predation, and selecting for these traits, may help improve reintroduction success. Here, we test whether prior exposure to predators or specific morphological and/or behavioural attributes explained variation in post-reintroduction survival in a moderate and low predator density environment. We exposed a population of the threatened burrowing bettong (Bettongia lesueur) to controlled densities of feral cats (Felis catus) for ≥3 years. We then conducted two translocations of cat-exposed and control populations that had no exposure to predators to a new site where cats were present at moderate, then low density. Variation in survival of burrowing bettongs was not explained by prior predator exposure to predators or measured individual traits at moderate cat density. At lower cat densities, males died sooner and burrowing bettongs with larger hind feet survived longer. Although prior cat-exposure did not confer a survival advantage at low cat densities, the cat-exposed burrowing bettong population had larger hind feet (n = 44) compared to the control population (n = 45) suggesting that trait divergence between cat-exposed and non-cat-exposed burrowing bettongs may not yet be sufficient for improved survival. Alternatively, prior predator exposure may not confer a survival advantage because they are “outgunned” by evolutionarily novel cats. Predation is a major problem thwarting successful reintroductions world-wide. Exposing populations to predators over longer time periods and periodically testing survival will be required to determine whether pre-release predator exposure prepares animals for life with novel predators. Our study highlights the importance of reducing predator activity at release sites prior to reintroduction to enable any benefits fro

The diets of many animals are influenced by resource availability, competition, and evolutionary selected traits enabling the utilization of palatable foods. Omnivores are species that maintain their macronutrient balance by supplementing highly abundant but poor nutritional quality food items, with sporadically available but high nutritional quality food items. Although there are anecdotal observations of Australian geckos (Lacertilia: Gekkonidae) consuming plant exudates, the consumption of plant material has long been considered to be anomalous behavior among Australian geckos. Here, we test the idea that sap feeding may not be anomalous behavior but instead a dietary niche of geckos that has gone unappreciated due to constraints on the methods used to quantify geckos’ diets. We tested this idea by investigating the consumption of Acacia victoriae gum by the gecko Gehyra versicolor using timed searches and time-lapse photography. We found that geckos frequently consumed gum, and G. versicolor numbers were five times greater on A. victoriae trees that exhibited significant gum bleeds compared to gecko numbers on non-bleeding trees. Taken together, our observations that G. versicolor spp. frequently feed on gum along with anecdotal reports of geckos consuming gum provide compelling evidence that gum/sap feeding is not anomalous behavior and suggest that many Australian gecko species are omnivores whose diets include plant exudates and animal prey.

The 5500 km long dingo barrier fence (DBF) is a boundary at which the goal of dingo control programs shifts from management to elimination. Since 1980 ecologists have used the discrepancies in dingo densities across the DBF to study the ecological role of Australia’s largest terrestrial predator. We used drone imagery, ground based shrub and tree counts, and camera trap footage to test our hypothesis that there are alternate states in plant, bird and mammal assemblages on either side of the DBF. We found that shrubs and trees were twice as dense where dingoes were rare, and 28 % of shrub and tree species, 78 % of mammal species, and 14 % of bird species recorded were significantly more likely to occur on one side of the DBF than the other. We provide the first comprehensive snapshot of how flora and fauna assemblages differ across the DBF. This study adds to literature demonstrating that the removal of the dingo has led to profound shifts in the shrub, mammal and bird assemblages in arid Australia. Any expansion of dingo control in arid Australia must be considered against the far-reaching consequences for ecosystem assembly associated with the removal of a top predator.

Inability to recognise and/or express effective anti-predator behaviour against novel predators as a result of ontogenetic and/or evolutionary isolation is known as ‘prey naiveté’. Natural selection favours prey species that are able to successfully detect, identify and appropriately respond to predators prior to their attack, increasing their probability of escape and/or avoidance of a predator. However, for many prey species, learning and experience are necessary to develop and perform appropriate anti-predator behaviours. Here, we investigate how a remnant population of bilbies (Macrotis lagotis) in south-west Queensland responded to the scents of two predators, native dingoes (Canis familiaris) and introduced feral cats (Felis catus); a procedural control (rabbits; Oryctolagus cuniculus); and an experimental control (no scent). Bilbies in Queensland have shared more than 8000 years of co-evolutionary history with dingoes and less than 140 years with feral cats and less than 130 years with rabbits. Bilbies spent the greatest proportion of time investigating and the least amount of time digging when cat and dingo/dog faeces were present. Our results show that wild-living bilbies displayed anti-predator responses towards the olfactory cues of both a long-term predator (dingoes) and an evolutionary novel predator (cats). Our findings suggest that native species can develop anti-predator responses towards introduced predators, providing support for the idea that predator naiveté can be overcome through learning and natural selection as a result of exposure to introduced predators. Significance statement: Not so naïve—As a result of lifetime and/or evolutionary isolation from predators, some prey species appear to be naïve towards introduced predators. This is particularly the case in Australia, where native mammalian species appear to be naïve towards recently introduced predators such as the feral cat and European red fox. In a study of wild-living bilbies

How to manage hybridization and introgression in wild animals is controversial. Wildlife managers and researchers may often rely upon phenotypic variables such as coat colour to inform on ground management decisions. In Australia, dingoes are typically believed to be ginger in colour, and unusual coat colours such as brindle or sable are widely posited to be evidence of contemporary domestic dog hybridization. We carried out microsatellite‐based genotyping on 1325 wild canids from southeastern Australia of known coat colour to estimate the extent of domestic dog introgression. A key aim of our study was to examine the relationship between coat colour and ancestry in wild dingoes. We observed that 27.4% of our samples were dingoes with no evidence of domestic dog ancestry whilst 72.6% were dingoes with some domestic dog ancestry. Our data confirm that feral dogs, domestic dogs with no dingo ancestry, are rare in the wild, representing less than 1.5% of the population. There was no coat colour that could distinguish dingoes with or without dog ancestry from each other. Contrary to popular belief, colours such as brindle and patchy were positively associated with dingoes with no dog ancestry and were less common in dingoes of mixed ancestry. A key finding of this work is that coat colour should not be used to assess ancestry in dingoes. Further research is needed to uncover the antiquity, origin and potential adaptive value of these genomic regions. It is possible that this is a similar example of adaptive introgression as has been observed in North American wolves with black coat colour. These data add perspective to global debates about how to manage and conserve enigmatic animal populations in the presence of modern or historical introgression.

Relaxation of predation pressure following the removal of mammalian predators has led to the irruption of large herbivores and excessive levels of herbivory in many regions of the Earth. Conservation reserves in dryland regions aim to restore ecological processes and facilitate biodiversity conservation by functioning as refuges from grazing by livestock. However, grazing pressure in conservation reserves may be high and hamper conservation objectives because wild herbivore populations have irrupted in the surrounding landscape due to predator control as well as the absence of hunting and competition with livestock within reserves. Here, we assess the relative abundance of native herbivores (kangaroos) and introduced herbivores (rabbits) using driving transects and dung surveys, and use selective exclosures to assess wild herbivores’ impacts on vegetation and soils in four conservation reserves in semi-arid Australia. Kangaroos were the dominant herbivore in each reserve. Grazing by kangaroos and/or rabbits was linked to reduced complexity of understorey vegetation, grass cover, species richness of grasses, forbs and shrubs, the depletion of soil carbon and phosphorous, and increased soil bulk density. The marked impacts of grazing by wild herbivores, particularly kangaroos, on vegetation and soils that we report are symptomatic of overgrazing. Our study provides evidence that grazing by kangaroos may jeopardize conservation efforts across a large region of semi-arid Australia. We contend that managing the total grazing pressure exerted by wild herbivores is crucial to prevent overgrazing in dryland conservation reserves where herbivore populations are not regulated by predators.

Apex predators can have substantial and complex ecological roles in ecosystems. However, differences in species-specific traits, population densities, and interspecific interactions are likely to determine the strength of apex predators’ roles. Here we report complementary studies examining how interactions between predator per capita metabolic rate and population density influenced the biomass, population energy use, and ecological effects of apex predators on their large mammalian prey. We first investigated how large mammal prey resources and field metabolic rates of terrestrial apex predators, comprising large mammals and the Komodo dragon (Varanus komodoensis), influenced their biomass densities and population energy use requirements. We next evaluated whether Komodo dragons, like apex mammalian predators, exerted top-down regulation of their large mammal prey. Comparison of results from field studies demonstrates that Komodo dragons attain mean population biomass densities that are 5.75−231.82 times higher than that of apex mammalian predator species and their guilds in Africa, Asia, and North America. The high biomass of Komodo dragons resulted in 1.96−108.12 times greater population energy use than that of apex mammalian predators. Nevertheless, substantial temporal and spatial variation in Komodo dragon population energy use did not regulate the population growth rates of either of two large mammal prey species, rusa deer (Rusa timorensis) and wild pig (Sus scrofa). We suggest that multiple processes weaken the capacity of Komodo dragons to regulate large mammal prey populations. For example, a low per capita metabolic rate requiring an infrequent and inactive hunting strategy (including scavenging), would minimize lethal and nonlethal impacts on prey populations. We conclude that Komodo dragons differ in their predatory role from, including not being the ecological analogs of, apex mammalian predators.

Copyright © 2019 Magnolia Press. The taxonomic status and systematic nomenclature of the Australian dingo remain contentious, resulting in decades of inconsistent applications in the scientific literature and in policy. Prompted by a recent publication calling for dingoes to be considered taxonomically as domestic dogs (Jackson et al. 2017, Zootaxa 4317, 201-224), we review the issues of the taxonomy applied to canids, and summarise the main differences between dingoes and other canids. We conclude that (1) the Australian dingo is a geographically isolated (allopatric) species from all other Canis, and is genetically, phenotypically, ecologically, and behaviourally distinct; and (2) the dingo appears largely devoid of many of the signs of domestication, including surviving largely as a wild animal in Australia for millennia. The case of defining dingo taxonomy provides a quintessential example of the disagreements between species concepts (e.g., biological, phylogenetic, ecological, morphological). Applying the biological species concept sensu stricto to the dingo as suggested by Jackson et al. (2017) and consistently across the Canidae would lead to an aggregation of all Canis populations, implying for example that dogs and wolves are the same species. Such an aggregation would have substantial implications for taxonomic clarity, biological research, and wildlife conservation. Any changes to the current nomen of the dingo (currently Canis dingo Meyer, 1793), must therefore offer a strong, evidence-based argument in favour of it being recognised as a subspecies of Canis lupus Linnaeus, 1758, or as Canis familiaris Linnaeus, 1758, and a successful application to the International Commission for Zoological Nomenclature - neither of which can be adequately supported. Although there are many species concepts, the sum of the evidence presented in this paper affirms the classification of the dingo as a distinct taxon, namely Canis dingo.

The interaction of gradual climate trends and extreme weather events since the turn of the century has triggered complex and, in some cases, catastrophic ecological responses around the world. We illustrate this using Australian examples within a press–pulse framework. Despite the Australian biota being adapted to high natural climate variability, recent combinations of climatic presses and pulses have led to population collapses, loss of relictual communities and shifts into novel ecosystems. These changes have been sudden and unpredictable, and may represent permanent transitions to new ecosystem states without adaptive management interventions. The press–pulse framework helps illuminate biological responses to climate change, grounds debate about suitable management interventions and highlights possible consequences of (non-) intervention.