Use of carrion fly iDNA metabarcoding to monitor invasive and native mammals

Severely fragmented habitats increase the risk of extirpation of native mammal populations through isolation, increased edge effects, and predation. Therefore, monitoring the movement of mammal populations through anthropogenically altered landscapes can inform conservation. We used metabarcoding of invertebrate-derived DNA (iDNA) from carrion flies (Calliphoridae and Sarcophagidae) to track mammal populations in the wheat belt of southwestern Australia, where widespread clearing for agriculture has removed most of the native perennial vegetation and replaced it with an agricultural system. We investigated whether the localization of the iDNA signal reflected the predicted distribution of 4 native species-echidna (Tachyglossus aculeatus), numbat (Myrmecobius fasciatus), woylie (Bettongia penicillata), and chuditch (Dasyurus geoffroii)-and 2 non-native, invasive mammal species-fox (Vulpes vulpes) and feral cat (Felis catus). We collected bulk iDNA samples (n = 150 samples from 3428 carrion flies) at 3 time points from 3 conservation reserves and 35 road edges between them. We detected 14 of the 40 mammal species known from the region, including our target species. Most detections of target taxa were in conservation reserves. There were a few detections from road edges. We detected foxes and feral cats throughout the study area, including all conservation reserves. There was a significant difference between the diversity (F3, 98  = 5.91, p < 0.001) and composition (F3, 43  = 1.72, p < 0.01) of taxa detections on road edges and conservation reserves. Conservation reserves hosted more native biodiversity than road edges. Our results suggest that the signals from iDNA reflect the known distribution of target mammals in this region. The development of iDNA methods shows promise for future noninvasive monitoring of mammals. With further development, iDNA metabarcoding could inform decision-making related to conservation of endangered taxa, invasive species management, and impacts of habitat fragmentation.

Identifying historical and future global change drivers that place species recovery at risk

Ecosystem management in the face of global change requires understanding how co-occurring threats affect species and communities. Such an understanding allows for effective management strategies to be identified and implemented. An important component of this is differentiating between factors that are within (e.g. invasive predators) or outside (e.g. drought, large wildfires) of a local manager's control. In the global biodiversity hotspot of south-western Australia, small- and medium-sized mammal species are severely affected by anthropogenic threats and environmental disturbances, including invasive predators, fire, and declining rainfall. However, the relative importance of different drivers has not been quantified. We used data from a long-term monitoring program to fit Bayesian state-space models that estimated spatial and temporal changes in the relative abundance of four threatened mammal species: the woylie (Bettongia penicillata), chuditch (Dasyurus geoffroii), koomal (Trichosurus vulpecula) and quenda (Isoodon fusciventor). We then use Bayesian structural equation modelling to identify the direct and indirect drivers of population changes, and scenario analysis to forecast population responses to future environmental change. We found that habitat loss or conversion and reduced primary productivity (caused by rainfall declines) had greater effects on species' spatial and temporal population change than the range of fire and invasive predator (the red fox Vulpes vulpes) management actions observed in the study area. Scenario analysis revealed that a greater extent of severe fire and further rainfall declines predicted under climate change, operating in concert are likely to further reduce the abundance of these species, but may be mitigated partially by invasive predator control. Considering both historical and future drivers of population change is necessary to identify the factors that risk species recovery. Given that both anthropogenic pressures and environmental disturbances can undermine conservation efforts, managers must consider how the relative benefit of conservation actions will be shaped by ongoing global change.

Value of information analysis for pandemic response: intensive care unit preparedness at the onset of COVID-19

BACKGROUND

During the early stages of the COVID-19 pandemic, there was considerable uncertainty surrounding epidemiological and clinical aspects of SARS-CoV-2. Governments around the world, starting from varying levels of pandemic preparedness, needed to make decisions about how to respond to SARS-CoV-2 with only limited information about transmission rates, disease severity and the likely effectiveness of public health interventions. In the face of such uncertainties, formal approaches to quantifying the value of information can help decision makers to prioritise research efforts.

METHODS

In this study we use Value of Information (VoI) analysis to quantify the likely benefit associated with reducing three key uncertainties present in the early stages of the COVID-19 pandemic: the basic reproduction number ([Formula: see text]), case severity (CS), and the relative infectiousness of children compared to adults (CI). The specific decision problem we consider is the optimal level of investment in intensive care unit (ICU) beds. Our analysis incorporates mathematical models of disease transmission and clinical pathways in order to estimate ICU demand and disease outcomes across a range of scenarios.

RESULTS

We found that VoI analysis enabled us to estimate the relative benefit of resolving different uncertainties about epidemiological and clinical aspects of SARS-CoV-2. Given the initial beliefs of an expert, obtaining more information about case severity had the highest parameter value of information, followed by the basic reproduction number [Formula: see text]. Resolving uncertainty about the relative infectiousness of children did not affect the decision about the number of ICU beds to be purchased for any COVID-19 outbreak scenarios defined by these three parameters.

CONCLUSION

For the scenarios where the value of information was high enough to justify monitoring, if CS and [Formula: see text] are known, management actions will not change when we learn about child infectiousness. VoI is an important tool for understanding the importance of each disease factor during outbreak preparedness and can help to prioritise the allocation of resources for relevant information.

Use of road underpasses by mammals and a monitor lizard in eastern Australia and consideration of the prey-trap hypothesis

Road networks continue to expand globally with predictable effects on ecological systems. Research into the effectiveness of road underpasses and overpasses for wildlife has been concentrated in North America and Europe. In Australia, most studies of underpasses have been of relatively short duration and without reference sites to give context to the measured rates of use. We studied 5-7 road underpasses at two locations in eastern Australia over 2-3 years, comparing camera trap detections of animals in underpasses with those at nearby forest sites. Three species of large macropod (wallabies and kangaroos) were frequently detected in the underpasses, with some underpasses traversed 1-4 times per week, and in many cases exceeded detections in the forest. The lace monitor (Varanus varius) was detected in all underpasses, often once per week during spring and summer, and infrequently in the forest. At each location, a different small macropod species, including one regionally threatened, showed a higher probability of detection in one underpass compared with several of the forest sites. The vulnerable koala (Phascolarctos cinereus) was detected infrequently in underpasses and in the adjoining forest. The short-beaked echidna (Tachyglossus aculeatus) had a high probability of detection in a single underpass. The "prey-trap hypothesis" postulates that predators will exhibit increased activity at underpasses as a consequence of prey being funneled. We found the red fox (Vulpes vulpes) had high activity in some underpasses. However, its activity coincided less than expected with the activity of the mammals most at risk to it. Our results provide no consistent support for the "prey-trap hypothesis." Instead, our study confirms the generic value of underpasses for a range of medium-large mammals as well as one large reptile. Habitat adjoining underpasses exert a strong influence on their use and require greater consideration to maximize underpass use.

Dietary flexibility and high predator efficacy facilitate coexistence in a novel predator interaction

Predator diet can be influenced by competition and intraguild predation, leading to resource partitioning and/or avoidance. For sympatric, endemic predators, these processes form as predator species coevolve, facilitating coexistence. However, when novel predator interactions occur, significant dietary overlap could create acute levels of competition leading to intraguild predation and population extinction, or accelerated changes in diet and/or spatial and temporal avoidance. We measured diet, intraguild predation, and spatial and temporal overlap in two predator species in a novel predator interaction: the western quoll (Dasyurus geoffroii), a small, native carnivore reintroduced to semi-arid Australia, and the domestic cat (Felis catus), a larger introduced carnivore already resident at the release site. Both species exhibited high dietary overlap and fed on mammals, reptiles, birds, and invertebrates. Cats included quolls in their diet. Quoll diet was broader (including carrion, bats, and plant material) and flexible, changing significantly with age, sex, and season. Introduced rabbit was the most common prey item recorded for both species (frequency of occurrence = 40–50%). However, quolls consumed rabbits in relation to their availability while rabbit consumption in cats was unrelated to availability suggesting a stronger dependence on rabbit prey. Quoll diet did not change over time since release and they did not spatially or temporally avoid cats. However, cats were significantly spatially associated with rabbits while quolls were not, suggesting higher predation efficacy in quolls possibly due to their smaller body size enabling them to catch rabbits inside warrens. Despite high dietary overlap and intraguild predation, the quoll’s broad and flexible diet and high predation efficacy appeared to assist in facilitating coexistence and reducing competition in this novel predator interaction. This dietary flexibility may be harnessed to improve conservation outcomes: reducing introduced rabbits in our study area could naturally reduce feral cat populations while having less impact on native quolls.

A framework of integrated research for managing introduced predators in the Pilbara bioregion, Western Australia

The effective control of wild dogs, feral cats and foxes is of primary interest to land managers, both for biodiversity conservation and for the protection of livestock. Control programs primarily target single species within the context of biodiversity conservation or livestock practices, but their effectiveness in depressing predator densities is unclear because monitoring is limited or not conducted. Here, we review and discuss the outcomes of a workshop to identify research priorities for managing predation on native fauna by introduced predators in the Pilbara bioregion in Western Australia. We suggest that the control of introduced predators will be most effective if it is implemented at a landscape-scale comprising integrated predator management that considers interspecific (predator) interactions combined with standardised monitoring to measure the effectiveness and benefits of control. Four research themes were identified: (1) collation and collection of baseline data, (2) effective monitoring of introduced predators, (3) understanding functional (ecological) roles of introduced predators within the different ecosystem contexts, and (4) identifying novel complementary approaches to protect threatened species. These themes collectively include research areas that invest in foundational, ecological and alternative biological parameters in research to close knowledge gaps related to the functional roles of introduced predators in the landscape. Addressing these research themes will assist land managers to achieve outcomes that address the needs of both biodiversity conservation and pastoral production. This framework is timely given the ongoing investment in offset funding being mobilised in the region.

Numerical response of predators to large variations of grassland vole abundance and long-term community changes

Voles can reach high densities with multiannual population fluctuations of large amplitude, and they are at the base of predator communities in Northern Eurasia and Northern America. This status places them at the heart of management conflicts wherein crop protection and health concerns are often raised against conservation issues. Here, a 20-year survey describes the effects of large variations in grassland vole populations on the densities and the daily theoretical food intakes (TFI) of vole predators based on roadside counts. Our results show how the predator community responded to prey variations of large amplitude and how it reorganized with the increase in a dominant predator, here the red fox, which likely negatively impacted hare, European wildcat, and domestic cat populations. This population increase did not lead to an increase in the average number of predators present in the study area, suggesting compensations among resident species due to intraguild predation or competition. Large variations in vole predator number could be clearly attributed to the temporary increase in the populations of mobile birds of prey in response to grassland vole outbreaks. Our study provides empirical support for more timely and better focused actions in wildlife management and vole population control, and it supports an evidence-based and constructive dialogue about management targets and options between all stakeholders of such socio-ecosystems.

A checklist of attributes for effective monitoring of threatened species and threatened ecosystems

Monitoring of threatened species and threatened ecosystems is critical for determining population trends, identifying urgency of management responses, and assessing the efficacy of management interventions. Yet many threatened species and threatened ecosystems are not monitored and for those that are, the quality of the monitoring is often poor. Here we provide a checklist of factors that need to be considered for inclusion in robust monitoring programs for threatened species and threatened ecosystems. These factors can be grouped under four broad themes - the design of monitoring programs, the structure and governance of monitoring programs, data management and reporting, and appropriate funding and legislative support. We briefly discuss key attributes of our checklist under these themes. Key topics in our first theme of the design of monitoring programs include appropriate objective setting, identification of the most appropriate entities to be measured, consistency in methodology and protocols through time, ensuring monitoring is long-term, and embedding monitoring into management. Under our second theme which focuses on the structure and governance of monitoring programs for threatened species and ecosystems, we touch on the importance of adopting monitoring programs that: test the effectiveness of management interventions, produce results that are relevant to management, and engage with (and are accepted by) the community. Under Theme 3, we discuss why data management is critical and highlight that the costs of data curation, analysis and reporting need to be factored into budgets for monitoring programs. This requires that appropriate levels of funding are made available for monitoring programs, beyond just the cost of data collection - a key topic examined in Theme 4. We provide examples, often from Australia, to highlight the importance of each of the four themes. We recognize that these themes and topics in our checklist are often closely inter-related and therefore provide a conceptual model highlighting these linkages. We suggest that our checklist can help identify the parts of existing monitoring programs for threatened species and threatened ecosystems that are adequate for the purpose or may be deficient and need to be improved.

Body Size and Bite Force of Stray and Feral Cats-Are Bigger or Older Cats Taking the Largest or More Difficult-to-Handle Prey?

As carnivorans rely heavily on their head and jaws for prey capture and handling, skull morphology and bite force can therefore reflect their ability to take larger or more difficult-to-handle prey. For 568 feral and stray cats (Felis catus), we recorded their demographics (sex and age), source location (feral or stray) and morphological measures (body mass, body condition); we estimated potential bite force from skull measurements for n = 268 of these cats, and quantified diet composition from stomach contents for n = 358. We compared skull measurements to estimate their bite force and determine how it varied with sex, age, body mass, body condition. Body mass had the strongest influence of bite force. In our sample, males were 36.2% heavier and had 20.0% greater estimated bite force (206.2 ± 44.7 Newtons, n = 168) than females (171.9 ± 29.3 Newtons, n = 120). However, cat age was the strongest predictor of the size of prey that they had taken, with older cats taking larger prey. The predictive power of this relationship was poor though (r² < 0.038, p < 0.003), because even small cats ate large prey and some of the largest cats ate small prey, such as invertebrates. Cats are opportunistic, generalist carnivores taking a broad range of prey. Their ability to handle larger prey increases as the cats grow, increasing their jaw strength, and improving their hunting skills, but even the smallest cats in our sample had tackled and consumed large and potentially 'dangerous' prey that would likely have put up a defence.

Are red-tailed phascogales (Phascogale calura) at risk from Eradicat® cat baits?

Abstract ContextFeral cats have benefitted from effective control of foxes in south-western Australia and, consequently, their impact on some threatened mammal species has increased. Control of feral cats in the region can be enhanced by use of the Eradicat® cat bait, but its impact on non-target animal populations requires investigation before widespread use. AimsThe aim of the present study was to determine through field trials whether consumption of Eradicat® baits by resident red-tailed phascogales, following a broadscale baiting operation to control feral cats, was sufficiently frequent to cause significant rates of mortality in wild populations of phascogales. MethodsNine radio-tagged red-tailed phascogales were monitored through an Eradicat® baiting event to determine their survival. Removal and consumption of toxic and non-toxic rhodamine B-labelled baits by a range of species were monitored with camera traps and by subsequent trapping of red-tailed phascogales and other mammals to sample whiskers for evidence of rhodamine uptake. Key resultsAlthough some phascogales showed interest in baits and sometimes moved them from the deposition site, all radio-tagged phascogales survived for at least 1 week after baiting, by which time very few or no baits remained. Examination of whiskers sampled from individuals exposed to rhodamine-labelled baits showed that consumption of non-toxic Eradicat® baits by phascogales was negligible; only one phascogale of 62 sampled showed any rhodamine banding. ConclusionsThe present study provided no evidence that red-tailed phascogales in the study region are at risk from an Eradicat® baiting episode in autumn. ImplicationsThe risk to red-tailed phascogale populations through the use of Eradicat® baiting to control cats in their habitat in the Great Southern region of Western Australia is likely to be low. Further research to elucidate any impact of repeated baiting on populations of this species at several locations is recommended.

Birds respond to woodland type, soil and mesic gradients in heterogeneous woodlands at Dryandra

The vast clearance of forest and woodland for agriculture with the removal of more than 93% of the native vegetation has decimated the fauna of what is now known as the Western Australian wheatbelt. This clearing has been particularly severe on wandoo woodlands through the wheatbelt. In order to quantify the usefulness of what has been left, three native woodland types were surveyed for avian abundance and diversity, in a large heterogeneous remnant of old-growth woodland, at Dryandra. Birds were counted at 70 points along seven transects, through three woodland types: powderbark wandoo (Eucalyptus accedens), wandoo (E. wandoo) and a brown mallet (E. astringens) plantation. Greater abundance and species richness were detected in E. wandoo woodland, although this is thought to be related to the more mesic and productive low-lying contours of the landscape on which it is situated.

Living with the enemy: a threatened prey species coexisting with feral cats on a fox-free island

Abstract ContextFeral domestic cats (Felis catus) have contributed to substantial loss of Australian wildlife, particularly small- and medium-sized terrestrial mammals. However, mitigating cat impacts remains challenging. Understanding the factors that facilitate coexistence between native prey and their alien predators could aid better pest management and conservation actions. AimsWe estimated feral cat density, examined the impact of habitat cover on long-nosed potoroos (Potorous tridactylus tridactylus), and assessed the spatial and temporal interactions between cats and potoroos in the ‘Bluegums’ area of French Island, south-eastern Australia. Materials and methodsWe operated 31 camera stations across Bluegums for 99 consecutive nights in each of winter 2018 and summer 2018/19. We used a spatially explicit capture–recapture model to estimate cat density, and two-species single-season occupancy models to assess spatial co-occurrence of cats and potoroos. We assessed the influence of vegetation cover and cat activity on potoroo activity by using a dynamic occupancy model. We also used image timestamps to describe and compare the temporal activities of the two species. Key resultsBluegums had a density of 0.77 cats per km2 across both seasons, although this is a conservative estimate because of the presence of unidentified cats. Cats and long-nosed potoroos were detected at 94% and 77% of camera stations, respectively. Long-nosed potoroo detectability was higher in denser vegetation and this pattern was stronger at sites with high cat activity. Cats and potoroos overlapped in their temporal activity, but their peak activity times differed. Conclusions Feral cat density at Bluegums, French Island, is higher than has been reported for mainland Australian sites, but generally lower than in other islands. Long-nosed potoroos were positively associated with cats, potentially indicating cats tracking potoroos as prey or other prey species that co-occur with potoroos. Temporal activity of each species differed, and potoroos sought more complex habitat, highlighting possible mechanisms potoroos may use to reduce their predation risk when co-occurring with cats. ImplicationsOur study highlighted how predator and prey spatial and temporal interactions, and habitat cover and complexity (ecological refuges), may influence the ability for native prey to coexist with invasive predators. We encourage more consideration and investigation of these factors, with the aim of facilitating more native species to persist with invasive predators or be reintroduced outside of predator-free sanctuaries, exclosures and island safe havens.

Conserving Australia’s threatened native mammals in predator-invaded, fire-prone landscapes

Abstract Inappropriate fire regimes and predation by introduced species each pose a major threat to Australia’s native mammals. They also potentially interact, an issue that is likely to be contributing to the ongoing collapse of native mammal communities across Australia. In the present review, I first describe the mechanisms through which fire could create predation pinch points, exacerbating the impacts of predators, including red foxes, Vulpes vulpes, and feral cats, Felis catus, on their native mammalian prey. These mechanisms include a localised increase in predator activity (a numerically mediated pathway) and higher predator hunting success after fire (a functionally moderated pathway), which could both increase native mammal mortality and limit population recovery in fire-affected landscapes. Evidence for such interactions is growing, although largely based on unreplicated experiments. Improving native mammal resilience to fire in predator-invaded landscapes requires addressing two key questions: how can the impacts of introduced predators on native mammals in fire-affected areas be reduced; and, does a reduction in predation by introduced species result in higher native mammal survival and population recovery after fire? I then examine potential management options for reducing predator impacts post-fire. The most feasible are landscape-scale predator control and the manipulation of fire regimes to create patchy fire scars. However, robust field experiments with adequate statistical power are required to assess the effectiveness of these approaches and preclude null (e.g. compensatory mortality) or adverse (e.g. mesopredator or competitor release) outcomes. Ongoing predator management and prescribed burning programs provide an opportunity to learn through replicated natural experiments as well as experimental manipulations. Standardised reporting protocols and cross-jurisdiction monitoring programs would help achieve necessary spatial and environmental replication, while multi-trophic, spatially explicit simulation models could help synthesise findings from disparate study designs, predict management outcomes and generate new hypotheses. Such approaches will be key to improving management of the complex mechanisms that drive threatened native mammal populations in Australia’s predator-invaded, fire-prone landscapes.

Aerial baiting for feral cats is unlikely to affect survivorship of northern quolls in the Pilbara region of Western Australia

Abstract ContextFeral cats (Felis catus) are known predators of northern quolls (Dasyurus hallucatus). Management to suppress feral cat densities often uses the poison sodium monofluoroacetate (compound 1080) in baits broadcast aerially. Eradicat® baits have demonstrated efficacy at reducing feral cat densities in some environments. However, these are not registered for use in northern Australia because their risk to non-target northern quolls remains unknown. AimsWe investigated the risks of aerially deployed feral cat Eradicat® baits containing 4.5mg of the poison 1080 on the survival of free-ranging northern quolls. MethodsThe study was conducted over a 20000-ha area in the Pilbara bioregion in Western Australia. Twenty-one wild northern quolls from a baited area and 20 quolls from a nearby reference area were fitted with radio-collars, and their survivorship was compared following the aerial deployment of over 9700 feral cat baits. Survivorship of quolls was assessed before and after the baiting campaign. Key resultsFive radio-collared quolls died at the baited area; four mortalities were due to feral cat predation, and the cause of one death was uncertain. At the reference area, seven radio-collared quolls were confirmed dead; three mortalities were due to feral cat predation, two from wild dog predation, and the cause of death of two could not be determined. Evidence for sublethal poison impacts on quolls, inferred by monitoring reproductive output, was lacking; average litter size was higher in quolls from the baited area than in those from the unbaited area, and within range of litters reported elsewhere, suggesting that acute effects of 1080 (if ingested) on reproductive success were unlikely. ConclusionsRadio-collared northern quolls survived the trial using Eradicat® baits, and females showed no acute effects of sublethal poisoning on the basis of reproductive output. A lack of quoll deaths attributed to 1080 poisoning suggests that the use of Eradicat® poses a low risk to northern quolls in the Pilbara. Importantly, the high level of mortalities associated with predation by feral cats, and to a lesser extent, canids, validates the threats of these introduced predators on quolls, suggesting that their control in areas where quolls are present is likely to be beneficial for the recovery of this species. ImplicationsLand managers aiming to conserve northern quolls in the Pilbara would see conservation benefits if they introduced an operational landscape-scale feral cat baiting program using Eradicat® baits, with appropriate monitoring.

Integrating feral cat (Felis catus) control into landscape-scale introduced predator management to improve conservation prospects for threatened fauna: a case study from the south coast of Western Australia

Abstract ContextFeral cat predation has had a significant impact on native Australian fauna in the past 200 years. In the early 2000s, population monitoring of the western ground parrot showed a dramatic decline from the pre-2000 range, with one of three meta-populations declining to very low levels and a second becoming locally extinct. We review 8 years of integrated introduced predator control, which trialled the incorporation of the feral cat bait Eradicat® into existing fox baiting programs. AimsTo test the efficacy of integrating feral cat control into an existing introduced predator control program in an adaptive management framework conducted in response to the decline of native species. The objective was to protect the remaining western ground parrot populations and other threatened fauna on the south coast of Western Australia. MethodsA landscape-scale feral cat and fox baiting program was delivered across south coast reserves that were occupied by western ground parrots in the early 2000s. Up to 500000ha of national parks and natures reserves were baited per annum. Monitoring was established to evaluate both the efficacy of landscape-scale baiting in management of feral cat populations, and the response of several native fauna species, including the western ground parrot, to an integrated introduced predator control program. Key resultsOn average, 28% of radio-collared feral cats died from Eradicat® baiting each year, over a 5-year period. The results varied from 0% to 62% between years. Changes in site occupancy by feral cats, as measured by detection on camera traps, was also variable, with significant declines detected after baiting in some years and sites. Trends in populations of native fauna, including the western ground parrot and chuditch, showed positive responses to integrated control of foxes and cats. ImplicationsLandscape-scale baiting of feral cats in ecosystems on the south coast of Western Australia had varying success when measured by direct knockdown of cats and site occupancy as determined by camera trapping; however, native species appeared to respond favourably to integrated predator control. For the protection of native species, we recommend ongoing baiting for both foxes and feral cats, complemented by post-bait trapping of feral cats. We advocate monitoring baiting efficacy in a well designed adaptive management framework to deliver long-term recovery of threatened species that have been impacted by cats.

DNA persistence in predator saliva from multiple species and methods for optimal recovery from depredated carcasses

Molecular forensics is an important component of wildlife research and management. Using DNA from noninvasive samples collected at predation sites, we can identify predator species and obtain individual genotypes, improving our understanding of predator–prey dynamics and impacts of predators on livestock and endangered species. To improve sample collection strategies, we tested two sample collection methods and estimated degradation rates of predator DNA on the carcasses of multiple prey species. We fed carcasses of calves (Bos taurus) and lambs (Ovis aires) to three captive predator species: wolves (Canis lupus), coyotes (C. latrans), and mountain lions (Puma concolor). We swabbed the carcass in the field, as well as removed a piece of hide from the carcasses and then swabbed it in the laboratory. We swabbed all tissue samples through time and attempted to identify the predator involved in the depredation using salivary DNA. We found the most successful approach for yielding viable salivary DNA was removing hide from the prey and swabbing it in the laboratory. As expected, genotyping error increased through time and our ability to obtain complete genotypes decreased over time, the latter falling below 50% after 24 h. We provide guidelines for sampling salivary DNA from tissues of depredated carcasses for maximum probability of detection.

A moral panic over cats

Some conservationists believe that free-ranging cats pose an enormous risk to biodiversity and public health and therefore should be eliminated from the landscape by any means necessary. They further claim that those who question the science or ethics behind their arguments are science deniers (merchants of doubt) seeking to mislead the public. As much as we share a commitment to conservation of biodiversity and wild nature, we believe these ideas are wrong and fuel an unwarranted moral panic over cats. Those who question the ecological or epidemiological status of cats are not science deniers, and it is a false analogy to compare them with corporate and right-wing special interests that perpetrate disinformation campaigns over issues, such as smoking and climate change. There are good conservation and public-health reasons and evidence to be skeptical that free-ranging cats constitute a disaster for biodiversity and human health in all circumstances. Further, there are significant and largely unaddressed ethical and policy issues (e.g., the ethics and efficacy of lethal management) relative to how people ought to value and coexist with cats and native wildlife. Society is better served by a collaborative approach to produce better scientific and ethical knowledge about free-ranging cats.

Molecular tools for identification of shark species involved in depredation incidents in Western Australian fisheries

Shark depredation is an issue of concern in some Western Australian recreational and commercial fisheries where it can have economic, social and ecological consequences. Knowledge of the shark species involved is fundamental to developing effective management strategies to mitigate the impacts of depredation. Identification of the species responsible is difficult as direct observation of depredation events is uncommon and evaluating bite marks on fish has a high degree of uncertainty. The use of trace DNA techniques has provided an alternative method for species identification. We demonstrate proof of concept for a targeted DNA barcoding approach to identify shark species using trace DNA found at bite marks on recovered remains of hooked fish. Following laboratory validation, forensic analysis of swabs collected from samples of bitten demersal fish, led to the definitive identification of shark species involved in 100% of the incidences of depredation (n = 16).

Prey selectivity by feral cats at central Australian rock-wallaby colonies

Threatened warru, or black-footed rock-wallaby (Petrogale lateralis MacDonnell Ranges race), populations in northern South Australia continued to decline despite baiting for foxes (Vulpes vulpes), which improved their short-term conservation status elsewhere. To investigate whether feral cats (Felis catus) also represent a risk to warru we compared frequencies of prey occurrence in 103 feral cat and 14 fox stomachs shot near warru colonies in northern South Australia during 2001–17 with measures of prey abundance from pitfall trapping and opportunistic searches. We hypothesise that one fresh adult warru kill and the presence of warru remains in four other cats suggests predation by cats on adult and juvenile warru. Small reptiles and invertebrates were the most frequently recorded prey of cats in summer, whereas rodents and small dasyurids were the most frequent prey items in winter. Small mammals, small snakes and pygopodid lizards were over-represented in the diet of cats compared with estimated encounter frequencies, whereas fast-running dragons, knob-tailed geckoes (Nephrurus) and echidnas (Tachyglossus aculeatus) were not recorded from cat stomachs despite being relatively abundant. Rabbits (Oryctolagus cuniculus), rodents and fruits were the most frequently recorded items in fox stomachs. This study reinforces that targeted management of feral cat populations should be considered in concert with control of canids in sustainable recovery programs for warru and other cat-vulnerable species.

How to improve threatened species management: An Australian perspective

Targeted threatened species management is a central component of efforts to prevent species extinction. Despite the development of a range of management frameworks to improve conservation outcomes over the past decade, threatened species management is still commonly characterised as ad hoc. Although there are notable successes, many management programs are ineffective, with relatively few species experiencing improvements in their conservation status. We identify underlying factors that commonly lead to ineffective and inefficient management. Drawing attention to some of the key challenges, and suggesting ways forward, may lead to improved management effectiveness and better conservation outcomes. We highlight six key areas where improvements are needed: 1) stakeholder engagement and communication; 2) fostering strong leadership and the development of achievable long-term goals; 3) knowledge of target species' biology and threats, particularly focusing on filling knowledge gaps that impede management, while noting that in many cases there will be a need for conservation management to proceed initially despite knowledge gaps; 4) setting objectives with measurable outcomes; 5) strategic monitoring to evaluate management effectiveness; and 6) greater accountability for species declines and failure to recover species to ensure timely action and guard against complacency. We demonstrate the importance of these six key areas by providing examples of innovative approaches leading to successful species management. We also discuss overarching factors outside the realm of management influence that can help or impede conservation success. Clear recognition of factors that make species' management more straightforward - or more challenging - is important for setting realistic management objectives, outlining strategic action, and prioritising resources. We also highlight the need to more clearly demonstrate the benefit of current investment, and communicate that the risk of under-investment is species extinctions. Together, improvements in conservation practice, along with increased resource allocation and re-evaluation of the prioritisation of competing interests that threaten species, will help enhance conservation outcomes for threatened species.

Trypanosome co-infections increase in a declining marsupial population

Understanding the impacts of parasites on wildlife is growing in importance as diseases pose a threat to wildlife populations. Woylie (syn. brush-tailed bettong, Bettongia penicillata) populations have undergone enigmatic declines in south-western Western Australia over the past decade. Trypanosomes have been suggested as a possible factor contributing towards these declines because of their high prevalence in the declining population. We asked whether temporal patterns of infection with Trypanosoma spp. were associated with the decline patterns of the host, or if other factors (host sex, body condition, co-infection or rainfall) were more influential in predicting infection patterns. Species-specific nested PCRs were used to detect the two most common trypanosomes (T. copemani and T. vegrandis) from 444 woylie blood samples collected between 2006 and 2012. Time relative to the decline (year) and an interaction with co-infection by the other trypanosome best explained patterns of infection for both trypanosomes. The prevalence of single species infections for both T. copemani and T. vegrandis was lower after the population crash, however, the occurrence of co-infections increased after the crash compared to before the crash. Our results suggest an interaction between the two parasites with the decline of their host, leading to a higher level of co-infection after the decline. We discuss the possible mechanisms that may have led to a higher level of co-infection after the population crash, and highlight the importance of considering co-infection when investigating the role of parasites in species declines.

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Woylie (bettong) populations have declined by >90% over 10 years.

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Prevalence of Trypanosoma copemani and T. vegrandis increased during the decline, and reset to a lower level after the crash.

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Overall prevalence of both Trypanosoma spp. decreased during the decline.

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The proportion of hosts co-infected with both species of Trypanosoma spp. increased after the population crash.

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Highlights the need to consider co-infection and the effects of declining host populations on parasite prevalence.

Invasive predators represent the greatest extinction threat to the endangered northern bettong (Bettongia tropica)

Context Identification of key threats to endangered species is vital for devising effective management strategies, but may be hindered when relevant data is limited. A population viability approach may overcome this problem. Aims We aimed to determine the population viability of endangered northern bettongs (Bettongia tropica) in north-eastern Australia. We also assessed the key threats to the population resilience and how the population viability responds to increases in mortality rates and changes in fire and drought frequency. Methods Using population viability analysis (PVA) we modelled survival probability of B. tropica populations under likely scenarios, including: (1) increased predation; (2) changes in drought and fire frequency predicted with anthropogenic climate change; and (3) synergistic effects of predation, fire and drought. Key results Population viability models suggest that populations are highly vulnerable to increases in predation by feral cats (Felis catus), and potentially red fox (Vulpes vulpes) should they colonise the area, as juvenile mortality is the main age class driving population viability. If B. tropica become more vulnerable to predators during post-fire vegetation recovery, more frequent fires could exacerbate effects of low-level cat predation. In contrast, it was predicted that populations would be resilient to the greater frequency of droughts expected as a result of climate change, with high probabilities of extinctions only predicted under the unprecedented and unlikely scenario of four drought years in 10. However, since drought and fire are interlinked, the impacts of predation could be more severe with climate change should predation and fire interact to increase B. tropica mortality risk. Conclusion Like other Potoroids, B. tropica appear highly vulnerable to predation by introduced mammalian predators such as feral cats. Implications Managers need information allowing them to recognise scenarios when populations are most vulnerable to potential threats, such as drought, fire and predation. PVA modelling can assess scenarios and allow pro-active management based on predicted responses rather than requiring collection of extensive field data before management actions. Our analysis suggests that assessing and controlling predator populations and thereby minimising predation, particularly of juveniles, should assist in maintaining stability of populations of the northern bettong.

Evaluation of risks for two native mammal species from feral cat baiting in monsoonal tropical northern Australia

Context Feral cats are a significant threat to native wildlife and broad-scale control is required to reduce their impacts. Two toxic baits developed for feral cats, Curiosity® and Hisstory®, have been designed to reduce the risk of baiting to certain non-target species. These baits involve encapsulating the toxin within a hard-shelled delivery vehicle (HSDV) and placing it within a meat attractant. Native animals that chew their food more thoroughly are predicted to avoid poisoning by eating around the HSDV. This prediction has not been tested on wild native mammals in the monsoonal wet–dry tropics of the Northern Territory. Aim The aim of this research was to determine whether northern quolls (Dasyurus hallucatus) and northern brown bandicoots (Isoodon macrourus) would take feral cat baits and ingest the HSDV under natural conditions on Groote Eylandt. Methods We hand-deployed 120 non-toxic baits with a HSDV that contained a biomarker, Rhodamine B, which stains animal whiskers when ingested. The species responsible for bait removal was determined with camera traps, and HSDV ingestion was measured by evaluating Rhodamine B in whiskers removed from animals trapped after baiting. Key results During field trials, 95% of baits were removed within 5 days. Using camera-trap images, we identified the species responsible for taking baits on 65 occasions. All 65 confirmed takes were by native species, with northern quolls taking 42 baits and northern brown bandicoots taking 17. No quolls and only one bandicoot ingested the HSDV. Conclusion The use of the HSDV reduces the potential for quolls and bandicoots to ingest a toxin when they consume feral cat baits. However, high bait uptake by non-target species may reduce the efficacy of cat baiting in some areas. Implications The present study highlighted that in the monsoonal wet–dry tropics, encapsulated baits are likely to minimise poisoning risk to certain native species that would otherwise eat meat baits. However, further research may be required to evaluate risks to other non-target species. Given the threat to biodiversity from feral cats, we see it as critical to continue testing Hisstory® and Curiosity® in live-baiting trials in northern Australia.

Degrees of population-level susceptibility of Australian terrestrial non-volant mammal species to predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus)

Context Over the last 230 years, the Australian terrestrial mammal fauna has suffered a very high rate of decline and extinction relative to other continents. Predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus) is implicated in many of these extinctions, and in the ongoing decline of many extant species. Aims To assess the degree to which Australian terrestrial non-volant mammal species are susceptible at the population level to predation by the red fox and feral cat, and to allocate each species to a category of predator susceptibility. Methods We collated the available evidence and complemented this with expert opinion to categorise each Australian terrestrial non-volant mammal species (extinct and extant) into one of four classes of population-level susceptibility to introduced predators (i.e. ‘extreme’, ‘high’, ‘low’ or ‘not susceptible’). We then compared predator susceptibility with conservation status, body size and extent of arboreality; and assessed changes in the occurrence of species in different predator-susceptibility categories between 1788 and 2017. Key results Of 246 Australian terrestrial non-volant mammal species (including extinct species), we conclude that 37 species are (or were) extremely predator-susceptible; 52 species are highly predator-susceptible; 112 species are of low susceptibility; and 42 species are not susceptible to predators. Confidence in assigning species to predator-susceptibility categories was strongest for extant threatened mammal species and for extremely predator-susceptible species. Extinct and threatened mammal species are more likely to be predator-susceptible than Least Concern species; arboreal species are less predator-susceptible than ground-dwelling species; and medium-sized species (35 g–3.5kg) are more predator-susceptible than smaller or larger species. Conclusions The effective control of foxes and cats over large areas is likely to assist the population-level recovery of ~63 species – the number of extant species with extreme or high predator susceptibility – which represents ~29% of the extant Australian terrestrial non-volant mammal fauna. Implications Categorisation of predator susceptibility is an important tool for conservation management, because the persistence of species with extreme susceptibility will require intensive management (e.g. predator-proof exclosures or predator-free islands), whereas species of lower predator susceptibility can be managed through effective landscape-level suppression of introduced predators.

Success criteria not met, but valuable information gained: monitoring a reintroduction of the tammar wallaby

Context Fauna translocations are a tool for improving the conservation status of threatened species. Reviews of translocations undertaken in Australia and globally have reported that many fail because of predation by exotic predators. The outcome of ~40% of translocations was unknown, often owing to inadequate post-release monitoring. Monitoring methods such as global positioning system data-loggers can provide valuable information on survival, habitat use and sociality, and can be particularly useful for cryptic species. Aims The present study used global positioning system (GPS) data-loggers and VHF radio-transmitters to evaluate the success of a reintroduction of the tammar wallaby and measured survival, short-term home-range, habitat use and proximity between reintroduced individuals (as a proxy for association). Methods Sixty-nine tammar wallabies of captive and wild stock were reintroduced to Kalbarri National Park (KNP) following long-term and broad-scale fox control, with nine receiving GPS data-loggers, and 16 receiving VHF radio-transmitters. Wallabies were intensively monitored for up to 11 months post-release. Mortalities were investigated using DNA identification and field necropsies. Key results In total, 16 of the 25 collared wallabies died within 11–319 days of release. Ten of the sixteen deaths were from predation. Home-range areas were larger than those reported elsewhere. Wallabies utilised long-undisturbed vegetation with a dense canopy cover during crepuscular periods. These areas were likely sought as refuge from predation and thermal extremes. During the main feeding period, a mosaic of recently burnt (i.e. ~1 year) and >10 years since last disturbance was important. Conclusions The reintroduction was not considered successful because two-thirds of the collared wallabies died within 1 year of release and, therefore, the success criteria were not met. Implications Despite long-term fox control in KNP, the majority of collared wallaby deaths were a result of fox predation. This highlights the inherent difficulty of establishing populations of some species in the presence of introduced predators. Additional research could assist in determining appropriate control levels for introduced predators, to help ensure the success of future translocations of this species. Consideration should be given to the prey naivety of source animals, prey-switching by introduced predators, and short-term supplementary feeding to assist population establishment.

Mammal conservation and invasive species control in Australia: harnessing a potential extinction machine

The catastrophic declines and extinctions of a unique Gondwana-derived Australian mammalian fauna is a wildlife tragedy of epic proportions that remains to be played out. Four alien species in particular, rabbits (Oryctolagus cuniculus), foxes (Vulpes vulpes), feral cats (Felis catus) and cane toads (Rhinella marina) are recognised as ongoing threats, but protective control protocols consist of holding actions that currently require never-ending ecosystem subsidies (typically, culling and fencing). Recent revolutionary developments in cell biology and gene engineering – the CRISPR invention – has enabled the construction of gene drives that offer the prospect of controlling these species more efficiently indeed, even the possibility of extirpating these species from Australia. The conservation potential of these new technologies is described and recommendations are made.

Mesopredator Management: Effects of Red Fox Control on the Abundance, Diet and Use of Space by Feral Cats

Apex predators are subject to lethal control in many parts of the world to minimize their impacts on human industries and livelihoods. Diverse communities of smaller predators-mesopredators-often remain after apex predator removal. Despite concern that these mesopredators may be 'released' in the absence of the apex predator and exert negative effects on each other and on co-occurring prey, these interactions have been little studied. Here, we investigate the potential effects of competition and intraguild predation between red foxes (Vulpes vulpes) and feral cats (Felis catus) in south-eastern Australia where the apex predator, the dingo (Canis dingo), has been extirpated by humans. We predicted that the larger fox would dominate the cat in encounters, and used a fox-removal experiment to assess whether foxes affect cat abundance, diet, home-range and habitat use. Our results provide little indication that intraguild predation occurred or that cats responded numerically to the fox removal, but suggest that the fox affects some aspects of cat resource use. In particular, where foxes were removed cats increased their consumption of invertebrates and carrion, decreased their home range size and foraged more in open habitats. Fox control takes place over large areas of Australia to protect threatened native species and agricultural interests. Our results suggest that fox control programmes could lead to changes in the way that cats interact with co-occurring prey, and that some prey may become more vulnerable to cat predation in open habitats after foxes have been removed. Moreover, with intensive and more sustained fox control it is possible that cats could respond numerically and alter their behaviour in different ways to those documented herein. Such outcomes need to be considered when estimating the indirect impacts of fox control. We conclude that novel approaches are urgently required to control invasive mesopredators at the same time, especially in areas where apex predators are absent.

Fox control and 1080 baiting conundrums: time to prepare for a CRISPR solution

For many years, managing rock-wallaby colonies (Petrogale lateralis lateralis) in the Western Australian Wheatbelt seemed to be a matter of routinely exposing foxes (Vulpes vulpes) to toxic baits (sodium fluoroacetate, 1080®) laid around their rocky outcrops. Recent research has revealed that 1080 baitings are no longer a viable management option. Baiting is flawed over the long term because it does not erase the wallabies’ pervasive fear of being depredated by foxes, which can still make their menacing presence felt before succumbing to poison bait. Accordingly, a ‘landscape of fear’ exists on all rock-wallaby sites, creating a ‘virtual boundary’ beyond which they fear to forage. Severe overgrazing occurs, ultimately causing population crashes, leaving behind devastated outcrops greatly diminished in carrying capacity. The fallout from this scenario produces a management conundrum. Rock-wallaby populations are unstable in the absence of fox control, and conversely, they are also unstable under long-term fox control. Management is now left with few options, and the future of the colonies remains open. Other conundrums involving bait interference and mesopredator release are described. An alternative to 1080 baiting is clearly needed. Recent developments in gene engineering (CRISPR technology) offer a solution in the foreseeable future.

Native marsupials as egg predators of artificial ground-nests in Australian woodland

Reviews of nest predation call for the identification of nest predators. The identity of nest predators is perhaps most poorly known for ground-nesting birds. Marsupials are not generally regarded as potential nest-predators of these birds, partly because the biology of rare Australian marsupials is not fully understood due to their rarity. This study identified three marsupials – boodie (Bettongia lesueur), woylie (Bettongia penicillata) and brushtail possum (Trichosurus vulpecula) – taking eggs from artificial nests modelled on that of the threatened painted button-quail (Turnix varius). Approximately one-third of the eggs were taken by the two bettongs and another third by the brushtail possum. I present dietary evidence of bettongs consuming vertebrate items including taking live prey to provide external validation for the notion that they may depredate natural nests. I suggest that more research is required on the impacts of reintroductions to avoid deleterious effects on resident species.

Falling apart? Insights and lessons from three recent studies documenting rapid and severe decline in terrestrial mammal assemblages of northern, south-eastern and south-western Australia

Context Since European settlement in 1788, much of the Australian terrestrial mammal fauna has declined or become extinct. The pattern of, and reason for, that decline was little documented, and is now difficult to decipher. Many mammal species are still declining, providing (an unfortunate) opportunity to better document the process, identify the causal factors and attempt to redress the problem. Aim We compare trends in mammal abundance reported in three recent longitudinal studies in conservation reserves in Australia. The studies were not established with the intention of documenting mammal decline, but marked simultaneous decline of co-existing species was the most striking feature of their results. Methods Long-term monitoring in Kakadu National Park, Northern Territory (2001–04 and 2007–09), the Upper Warren region of Western Australia (since 1974) and the Great Otway National Park, Victoria (since 1975) principally relied on trapping, but also some spotlighting and sand plots, to document changes and trends in abundance in their respective mammal assemblages. Key results Decline was reported in most mammal species, across taxonomic groups, diets and size classes, but mostly involved species <5500g. The studies differed in their monitoring protocols and varied in the degree to which potential causal factors were monitored, thereby constraining interpretation of the drivers of declines. Inappropriate fire regimes and predation by feral cats are likely contributing factors in at least two study areas, and periods of markedly below-average rainfall are implicated in two areas. Conclusions We conclude the following: (1) conservation reserves in Australia may be failing to maintain at least some elements of the biodiversity that they were established to protect, and substantially enhanced management is required to redress this problem; (2) with current threats, mammal assemblages in Australia may be highly unstable; (3) substantial increase in effective long-term biodiversity monitoring programs in an adaptive management framework is needed; and (4) such monitoring programs will be more insightful if they also monitor factors driving population change. Implications Native mammal species declines and community disassembly may be occurring elsewhere. Long-term monitoring is critical for assessing trends in biodiversity and if done well, it can guide more effective and efficient management to deliver better conservation outcomes.

Occupancy of the Invasive Feral Cat Varies with Habitat Complexity

The domestic cat (Felis catus) is an invasive exotic in many locations around the world and is thought to be a key factor driving recent mammal declines across northern Australia. Many mammal species native to this region now persist only in areas with high topographic complexity, provided by features such as gorges or escarpments. Do mammals persist in these habitats because cats occupy them less, or despite high cat occupancy? We show that occupancy of feral cats was lower in mammal-rich habitats of high topographic complexity. These results support the idea that predation pressure by feral cats is a factor contributing to the collapse of mammal communities across northern Australia. Managing impacts of feral cats is a global conservation challenge. Conservation actions such as choosing sites for small mammal reintroductions may be more successful if variation in cat occupancy with landscape features is taken into account.

Temporal Patterns in the Abundance of a Critically Endangered Marsupial Relates to Disturbance by Roads and Agriculture

The aim of this study was to investigate how landscape disturbance associated with roads, agriculture and forestry influenced temporal patterns in woylie (Bettongia penicillata) abundance before, during and after periods of rapid population change. Data were collected from an area of approximately 140,000 ha of forest within the Upper Warren region in south-western Australia. Woylie abundance was measured using cage trapping at 22 grid and five transect locations with varying degrees of landscape disturbance between 1994 and 2012. We found evidence that the distribution and abundance of woylies over time appears to be related to the degree of fragmentation by roads and proximity to agriculture. Sites furthest from agriculture supported a greater abundance of woylies and had slower rates of population decline. Sites with fewer roads had a greater abundance of woylies generally and a greater rate of increase in abundance after the implementation of invasive predator control. The results of this study suggest that landscape disturbance is less important at peak population densities, but during times of environmental and population change, sites less dissected by roads and agriculture better support woylie populations. This may be due to the role these factors play in increasing the vulnerability of woylies to introduced predators, population fragmentation, weed species invasion, mortality from road collisions or a reduction in available habitat. Strategies that reduce the impact of disturbance on woylie populations could include the rationalisation of forest tracks and consolidation of contiguous habitat through the acquisition of private property. Reducing the impact of disturbance in the Upper Warren region could improve the resilience of this critically important woylie population during future environmental change.