Targeted control of widespread exotic species for biodiversity conservation: The Red Fox (Vulpes vulpes) in New South Wales, Australia

Dogs suppress a pivotal function in the food webs of sandy beaches

Domestic dogs are the most abundant carnivore globally and have demonstrable negative impacts to wildlife; yet, little evidence regarding their functional roles in natural food webs exists. Adding dogs to food webs may result in a net loss (via suppression of naturally occurring species), net gain (via mesopredator release), or no change (via functional replacement) to ecosystem function. Scavenging is a pivotal function in ecosystems, particularly those that are energetically supported by carrion. Dogs also scavenge on animal carcasses, but whether scavenging by dogs influences the structural and functional properties of food webs remains unclear. Here we used camera traps baited with carrion to test the effect of dogs on the composition and diversity of the vertebrate scavenger guild, as well as carrion detection and consumption rates. We conducted this work in sandy beach ecosystems, which rely on the import of marine organic matter (i.e. stranding of dead marine animals). Diversity of the scavenger community was similar on beaches without dogs. Dogs increased the time it took for carcasses to be detected and decreased the proportion of carrion consumed. This ‘dog suppression effect’ on scavenging was stronger for nocturnal mammalian scavengers, presumably being driven by indirect trait-mediated effects, which raises further questions about the broader ecological consequences of domestic dogs in natural systems.

Compassionate Conservation Clashes With Conservation Biology: Should Empathy, Compassion, and Deontological Moral Principles Drive Conservation Practice?

“Compassionate Conservation” is an emerging movement within conservation science that is gaining attention through its promotion of “ethical” conservation practices that place empathy and compassion and the moral principles of “first, do no harm” and “individuals matter” at the forefront of conservation practice. We have articulated elsewhere how Compassionate Conservation, if adopted, could be more harmful for native biodiversity than any other conservation action implemented thus far, while also causing more net harm to individuals than it aims to stop. Here, we examine whether empathy, compassion and inflexible adherence to moral principles form a solid basis upon which to meet the goals of conservation biology as specified by pioneers in the discipline. Specifically, we examine a large empirical literature demonstrating that empathy is subject to significant biases and that inflexible adherence to moral rules can result in a “do nothing” approach. In light of this literature, we argue that our emotional systems have not evolved to provide a reliable basis for making decisions as to how best to ensure the long-term persistence of our planet. Consequently, in its most radical form, the Compassionate Conservation philosophy should not be enshrined as a legalized guiding principle for conservation action.

How influential are squamate reptile traits in explaining population responses to environmental disturbances?

Abstract Context Understanding how organismal attributes influence sensitivity to environmental perturbations is a central theme in ecology and conservation. Certain traits, such as body size, habitat use, dietary preference and reproductive output are considered important determinants of animal species’ responses to the impacts of ecological disturbances. However, the general relationships between functional traits and post-disturbance responses by animals are not fully understood. AimsOur primary aim was to use a meta-analysis to evaluate the influence of species traits on variation in population abundances of squamate reptiles (i.e. lizards and snakes). MethodsWe extracted data from 107 original published studies, from which 1027 mean effect sizes of post-disturbance responses by 298 species were estimated. We examined short-term responses only (i.e. within 3 years since the most recent disturbance). A comprehensive range of disturbances was examined, such as habitat destruction, fragmentation, fire, and exotic-species invasions. We used Bayesian linear mixed-effect modelling (BLMM), utilising the Markov-chain Monte Carlo algorithm (MCMC) for the meta-regression. Specifically, we tested the influence of eight species traits (body size, diet, temporal activity pattern, sociality, reproductive mode, clutch size, habitat selection, and mean body temperature), along with disturbance type, in explaining variation in species-specific abundance responses of squamate reptiles post-disturbance. Key resultsPost-disturbance abundance responses of squamate species were significantly influenced by two parameters, namely, mean body temperature and clutch size. In general, significant positive responses post-disturbance were observed for species with higher mean body temperatures and a greater clutch size. The type of disturbance had no detectable influence on squamate abundances. The influence of random effects (heterogeneity among studies and species, and broad taxonomic identity) accounted for more of the model variation than did the fixed effects (species traits and disturbance type). ConclusionsCertain species traits exerted some influence on the sensitivities of lizards and snakes to ecological disturbances, although the influence of random effects was very strong. Our findings are likely to be a result of the complexity and idiosyncratic nature of natural abundance patterns among animal species, in addition to the potential confounding effect of methodological differences among studies. ImplicationsThe present study is the first major quantitative synthesis of how species traits influence population-level responses of squamate reptiles to ecological disturbances. The findings can be used to guide conservation efforts and ecological management, such as by prioritising the efforts of mitigation on species that reproduce more slowly, and those with lower body temperatures.

The Wily and Courageous Red Fox: Behavioural Analysis of a Mesopredator at Resource Points Shared by an Apex Predator

The red fox (Vulpes vulpes) is a widespread and ecologically significant terrestrial mesopredator, that has expanded its range with human globalisation. Despite this, we know relatively little about their behaviour under the wide range of ecological conditions they experience, particularly how they navigate the risk of encounters with apex predators. We conducted the first ethological study of foxes outside their historic native range, in Australia, where both the foxes and their main predator were protected from human hunting. Using remote camera traps, we recorded foxes visiting key resource points regularly utilised by territorial dingoes (Canis dingo), their local apex predator, in the Painted Desert, South Australia. We constructed an ethogram sensitive to a range of behaviours and attitudes. Since foxes are suppressed by dingoes, we expected that the foxes would primarily be in a cautious state. In contrast, we found that foxes were in a confident state most of the time. Where human hunting is absent, social stability of predators may increase predictability and therefore decrease fear.

Designing a camera trap monitoring program to measure efficacy of invasive predator management

Context Evaluating predator management efficacy is difficult, especially when resources are limited. Carefully designing monitoring programs in advance is critical for data collection that is sufficient to evaluate management success and to inform decisions. Aims The aim was to investigate how the design of camera trap studies can affect the ability to reliably detect changes in red fox (Vulpes vulpes) activity over space and time. Specifically, to examine the effect of study duration, camera cost and detection zone under various environmental and management scenarios, including different fox densities, management impacts, monitoring budgets and levels of spatial and temporal variation. Methods A generalised linear mixed model was used to analyse simulated datasets from control sites and sites with predator management actions implemented, following a before–after or control–impact sampling design. Statistical power analyses were conducted to evaluate whether a change in fox abundance could be detected across various environmental and management scenarios. Key results Results showed that a before–after sampling design is less sensitive than a control–impact sampling design to the number of cameras used for monitoring. However, a before–after sampling design requires a longer monitoring period to achieve a satisfactory level of power, due to higher sensitivity to study duration. Given a fixed budget, there can be a trade-off between purchasing a small number of high quality cameras with large detection zones, or a larger number of cameras with smaller detection zones. In a control-impact design we found that if spatial heterogeneity was high, a larger number of cameras with smaller detection zones provided more power to detect a difference in fox abundance. Conclusion This simulation-based approach demonstrates the importance of exploring various monitoring designs to detect the effect of predator management across plausible environmental and budgetary scenarios. Implications The present study informs the monitoring design of an adaptive management program that aims to understand the role of managing fox predation on malleefowl (Leipoa ocellata), a threatened Australian bird. Furthermore, this approach provides a useful guide for developing cost-effective camera trap monitoring studies to assess efficacy of conservation management programs. Power analyses are an essential step for designing efficient monitoring, and indicate the strength of ecological signals that can realistically be detected through the noise of spatial and temporal heterogeneity under various budgetary constraints.

Variable reptile responses to introduced predator control in southern Australia

Context Australia harbours an immense diversity of reptiles, which are generally expected to have frequent and diverse trophic interactions with introduced mammalian carnivores. Nevertheless, the potential for predatory or competitive interactions is likely to be contingent on multiple processes, including the importance of reptiles in the diet of introduced predators, alongside overlaps in their body sizes and ecological niches that would influence the strength of their interactions. In Australia’s temperate and relatively productive mesic environments there is little understanding of how introduced mammalian predators affect reptile assemblages. Aims The aim was to investigate the effects that a European red fox (Vulpes vulpes; 5–7kg) suppression program had on the abundance and species richness of a reptile community, with species ranging in size from the largest local ectothermic predator, the lace monitor (Varanus varius; 4–7kg), to small terrestrial reptiles (mostly 10–150g). Methods We utilised two sampling designs (baited camera monitoring stations and pitfall trapping) to evaluate the effects of fox suppression and other site-level ecological covariates (fire regime and habitat vegetation characteristics) on the lace monitor and small terrestrial reptiles. Reptile abundance and richness at site level were estimated from count-related abundance models. Key results For lace monitors, significantly higher abundances occurred in poison-baited areas relative to control areas. This suggests that fox suppression can affect the populations of the lace monitor via mesopredator release arising from reduced competition and, possibly, predation. For small terrestrial reptiles, neither abundance nor species richness were influenced by fox suppression. Individual abundances of the three most common small reptile species matched the overall pattern, as only responses to structural parameters of the habitat were detected. Conclusions Fox suppression can have different impacts for different reptile taxa, pending their ecological niche, as only the largest species was affected. Implications Increase in lace monitor abundance may change food web dynamics in fox-suppressed sites, such as by increasing predation pressure on arboreal marsupials.

Control of the red fox in remnant forest habitats

Context The European red fox (Vulpes vulpes) is subject to control by poison baiting in many parts of its range in Australia to protect both native and domestic species. Assessments of baiting programs can improve their effectiveness and help ensure that long-term control outcomes are achieved. Aims We describe spatial and temporal patterns of bait uptake by the red fox in remnant forest within an agricultural matrix, including multiple bait-takes and hotspots of activity over time, and examine the response of foxes to baiting operations. Methods We analysed bait uptake (Foxoff®) from 12 baiting operations over 5 years in the Goonoo forest, a 62 500 ha remnant surrounded by cleared land in central New South Wales, Australia. More than 8000 checks of bait-stations were analysed to provide indices of fox activity per bait-check, patterns of bait removal during bait-checks, and bait uptake at stations within and across operations. Fox activity was also assessed before and after four operations using sand plots. Key results There was no consistent decline in relative fox activity in relation to changes in bait-take; increases in the activity index occurred in successive checks within most operations. Spatial analyses of checks within control operations showed that consecutive baits were removed at more than 70% of bait stations that were visited by foxes. Temporal analyses showed further that within an operation, multiple bait-takes occurred at ~20% of stations and, across all operations, hot spots of activity could be identified. Conclusions A short (2-week) baiting window in standard baiting operations may not be effective in reducing the activity of foxes across the landscape. It is likely that many baits are being cached during each operation, and that foxes move into the baited area from unbaited surrounding areas. Implications More frequent and timely baiting operations are needed to achieve maximum disruption to the fox population in the remnant forest environment, at least as indicated by patterns of bait-take. Increasing the distance between baits, to ~1.5 km, while reducing baiting-gaps at the landscape scale, will also be important to reduce caching and still ensure that baits are encountered.

Assessment of non-target risks from sodium fluoroacetate (1080), para-aminopropiophenone (PAPP) and sodium cyanide (NaCN) for fox-incursion response in Tasmania

Context Access to effective toxicants and delivery systems that target red foxes (Vulpes vulpes) are likely to be required as part of a management strategy in the event of future red fox incursions into Tasmania. Potential toxicants include sodium fluoroacetate (1080), para-aminopropiophenone (PAPP) and sodium cyanide (NaCN). Aims To assess the risk of three toxicants (1080, PAPP and NaCN) to non-target native Tasmanian mammals and birds and domestic dogs and cats. Methods We identified native Tasmanian mammal and bird species that may potentially consume fox baits, by reviewing the ecological traits of native species and by monitoring 180 buried bait stations with video cameras. We also assess the potential risk to non-target species of dying from a single standard dose of each of the three toxicants. Key results Seven native mammal and 20 native bird species have the potential to consume fox bait. All vertebrates would be susceptible to a single dose of NaCN. Consumption of a single fox bait containing 3 mg 1080 may be lethal to five native mammals, three native birds, and the domestic cat (Felis catus) and dog (Canis familiaris). Consumption of a single fox bait containing 226 mg PAPP may be lethal to the spotted-tailed quoll (Dasyurus maculatus) and the domestic cat and dog. Delivery of toxicants via a mechanical ejector would reduce non-target exposure to toxicants. Conclusions It appears that PAPP would provide a useful alternative to 1080 for use in lethal fox control in Tasmania, either in the event of an incursion or in the eradication of an established population. NaCN is not suitable for broadscale use in Tasmania because of the high susceptibility of all vertebrates to this toxicant. Nevertheless, NaCN would be useful in highly restricted areas in the event of an incursion where carcass recovery is important. The use of a mechanical ejector to target delivery of toxicants to red foxes would reduce non-target risks. Implications Our results clarify theoretical non-target risks from any future fox-poisoning programs in Tasmania and highlight the need for further research on the susceptibility of native species to PAPP as a potential alternative to 1080.

The pitfalls of wildlife camera trapping as a survey tool in Australia

Camera trapping is a relatively new addition to the wildlife survey repertoire in Australia. Its rapid adoption has been unparalleled in ecological science, but objective evaluation of camera traps and their application has not kept pace. With the aim of motivating practitioners to think more about selection and deployment of camera trap models in relation to research goals, we reviewed Australian camera trapping studies to determine how camera traps have been used and how their technological constraints may have affected reported results and conclusions. In the 54 camera trapping articles published between 1991 and 2013, mammals (86%) were studied more than birds (10%) and reptiles (3%), with small to medium-sized mammals being most studied. Australian camera trapping studies, like those elsewhere, have changed from more qualitative to more complex quantitative investigations. However, we found that camera trap constraints and limitations were rarely acknowledged, and we identified eight key issues requiring consideration and further research. These are: camera model, camera detection system, camera placement and orientation, triggering and recovery, camera trap settings, temperature differentials, species identification and behavioural responses of the animals to the cameras. In particular, alterations to animal behaviour by camera traps potentially have enormous influence on data quality, reliability and interpretation. The key issues were not considered in most Australian camera trap papers and require further study to better understand the factors that influence the analysis and interpretation of camera trap data and improve experimental design.

Intense predation of non-colonial, ground-nesting bird eggs by corvid and mammalian predators

Context Loss of eggs to predators is a major cause of reproductive failure among birds. It is especially pronounced among ground-nesting birds because their eggs are accessible to a wide range of predators. Few studies document the main causes of clutch fate of ground-nesting birds. Aims The main objective of the present study was to identify the major egg predator of red-capped plovers (Charadrius ruficapillus). We also investigated the effectiveness of the following two primary strategies available to the plovers to avoid egg predation: (1) the placement of clutches under vegetative cover and (2) avoiding predators by nesting outside the peak season of predator occurrence. Methods Remote-sensing cameras were deployed on plover nests to identify egg predators and nests were monitored over four breeding seasons to document reproductive success and fate. An experiment using false clutches with model eggs investigated the influence of nest cover on the risk of egg predation throughout the year. Line-transect surveys were conducted to estimate the abundance of egg predators in and around the wetlands. Key results The little raven (Corvus mellori) was the major egg predator identified in 78.6% of red-capped plover clutches and in 92.4% of false clutches that were camera-monitored. The hatching success of plover eggs was not influenced by nest cover (P = 0.36), but model egg survival in false clutches improved significantly with the presence of nest cover (P = 0.02). The abundance of little ravens increased during the plover breeding season and was highly negatively correlated with false clutch survival (rpearson = –0.768, P = 0.005). Conclusions Little ravens were the major predator of red-capped plover eggs and their abundance increased significantly during the plover breeding season. Any influence of nest cover on hatching success of eggs may have been masked by the extremely high rate of egg loss associated with the increased little raven abundance during the plover breeding season. Implications The high rate of egg predation is likely to have negative consequences on the local red-capped plover population, suggesting management is warranted. Little raven populations have expanded and, thus, their impact as egg predators needs to be investigated especially on threatened species.

Assessing risks to non-target species during poison baiting programs for feral cats

Poison baiting is used frequently to reduce the impacts of pest species of mammals on agricultural and biodiversity interests. However, baiting may not be appropriate if non-target species are at risk of poisoning. Here we use a desktop decision tree approach to assess the risks to non-target vertebrate species in Australia that arise from using poison baits developed to control feral house cats (Felis catus). These baits are presented in the form of sausages with toxicant implanted in the bait medium within an acid-soluble polymer capsule (hard shell delivery vehicle, or HSDV) that disintegrates after ingestion. Using criteria based on body size, diet and feeding behaviour, we assessed 221 of Australia's 3,769 native vertebrate species as likely to consume cat-baits, with 47 of these likely to ingest implanted HSDVs too. Carnivorous marsupials were judged most likely to consume both the baits and HSDVs, with some large-bodied and ground-active birds and reptiles also consuming them. If criteria were relaxed, a further 269 species were assessed as possibly able to consume baits and 343 as possibly able to consume HSDVs; most of these consumers were birds. One threatened species, the Tasmanian devil (Sarcophilus harrisii) was judged as definitely able to consume baits with implanted HSDVs, whereas five threatened species of birds and 21 species of threatened mammals were rated as possible consumers. Amphibia were not considered to be at risk. We conclude that most species of native Australian vertebrates would not consume surface-laid baits during feral cat control programs, and that significantly fewer would be exposed to poisoning if HSDVs were employed. However, risks to susceptible species should be quantified in field or pen trials prior to the implementation of a control program, and minimized further by applying baits at times and in places where non-target species have little access.

Fox baiting in agricultural landscapes: preliminary findings on the importance of bait-site selection

Context Little is known about the importance of bait-site selection during lethal fox-baiting programmes. Improved bait placement may increase the efficacy of baiting and help reduce fox impacts on wildlife and livestock. Aims To determine whether bait uptake by the red fox (Vulpes vulpes) differed among five landscape elements (roadsides, fence lines, open paddocks, creek lines and remnant vegetation) and at sites with high or low habitat (ground cover) complexity. Methods We measured bait uptake at 300 bait stations distributed evenly among the landscape elements in agricultural landscapes in northern Victoria, Australia. Bait uptake was also compared between sites with low and high habitat complexity in districts subject to no fox control and annual fox control. Key results Among landscape elements, bait uptake was significantly higher in roadside vegetation and along vegetated creek lines than it was along fence lines and in open paddocks (P < 0.05 in each case). Within roadside vegetation, bait uptake was significantly (P = 0.001) lower at sites with a high habitat complexity than at sites with low complexity, particularly in areas subject to annual fox control. Conclusions Bait placement influences bait-uptake rates considerably and greater consideration should be placed on bait-site selection during fox-baiting programmes. Habitat complexity limited bait uptake, which may indicate a reduced capacity of foxes to find baits in complex habitats. Implications Our results should help improve bait-site selection in agricultural landscapes and may increase the efficacy of fox baiting to the benefit of native fauna and livestock.

Seven considerations about dingoes as biodiversity engineers: the socioecological niches of dogs in Australia

Australian dingoes have recently been suggested as a tool to aid biodiversity conservation through the reversal or prevention of trophic cascades and mesopredator release. However, at least seven ecological and sociological considerations must be addressed before dog populations are positively managed.Domestication and feralisation of dingoes have resulted in behavioural changes that continue to expose a broad range of native and introduced fauna to predation.Dingoes and other dogs are classic mesopredators, while humans are the apex predator and primary ecosystem engineers in Australia.Anthropogenic landscape changes could prevent modern dingoes from fulfilling their pre-European roles.Dingoes are known to exploit many of the same species they are often presumed to ‘protect’, predisposing them to present direct risks to many threatened species.The assertion that contemporary dog control facilitates the release of mesopredators disregards the realities of effective dog control, which simultaneously reduces fox and dog abundance and is unlikely to enable increases in fox abundance.The processes affecting threatened fauna are likely a combination of both top-down and bottom-up effects, which will not be solved or reversed by concentrating efforts on managing only predator effects.Most importantly, human social and economic niches are highly variable across the ecosystems where dingoes are present or proposed. Human perceptions will ultimately determine acceptance of positive dingo management.Outside of an adaptive management framework, positively managing dingoes while ignoring these seven considerations is unlikely to succeed in conserving native faunal biodiversity but is likely to have negative effects on ecological, social and economic values.

Population and behavioural responses of native prey to alien predation

The introduction of invasive alien predators often has catastrophic effects on populations of naïve native prey, but in situations where prey survive the initial impact a predator may act as a strong selective agent for prey that can discriminate and avoid it. Using two common species of Australian small mammals that have persisted in the presence of an alien predator, the European red fox Vulpes vulpes, for over a century, we hypothesised that populations of both would perform better where the activity of the predator was low than where it was high and that prey individuals would avoid signs of the predator's presence. We found no difference in prey abundance in sites with high and low fox activity, but survival of one species-the bush rat Rattus fuscipes-was almost twofold higher where fox activity was low. Juvenile, but not adult rats, avoided fox odour on traps, as did individuals of the second prey species, the brown antechinus, Antechinus stuartii. Both species also showed reduced activity at foraging trays bearing fox odour in giving-up density (GUD) experiments, although GUDs and avoidance of fox odour declined over time. Young rats avoided fox odour more strongly where fox activity was high than where it was low, but neither adult R. fuscipes nor A. stuartii responded differently to different levels of fox activity. Conservation managers often attempt to eliminate alien predators or to protect predator-naïve prey in protected reserves. Our results suggest that, if predator pressure can be reduced, otherwise susceptible prey may survive the initial impact of an alien predator, and experience selection to discriminate cues to its presence and avoid it over the longer term. Although predator reduction is often feasible, identifying the level of reduction that will conserve prey and allow selection for avoidance remains an important challenge.

The potential for participatory landscape management to reduce the impact of the red fox (Vulpes vulpes) on lamb production

ContextRed fox (Vulpes vulpes) predation has an impact on populations of many species throughout its range worldwide, and as such, the red fox is the target of control programs. AimsWe investigated the potential for participatory landscape management to reduce the impact of fox predation on a major prey species, lambs. MethodsThe present study monitored fox-management programs already operating across 4.5 million hectares of regional New South Wales to compare the impact of varying (frequency and spatial coverage) control effort on lamb survival. Key resultsThe frequency and timing of fox control was correlated with lamb survival. Lamb survival was higher in areas where fox baiting was carried out twice a year, in autumn and late winter/spring. Spatial coverage of the control program was also positively correlated with lamb survival. Properties that had near neighbours (up to 2.5 km away) participating in group fox-control programs had higher survival of lambs than properties that did not. ConclusionsThese results support the development of a high level of group participation in fox-control programs that considers both spatial extent and frequency of baiting programs. They also support a movement away from the reactionary, short-term practice of baiting small areas to protect vulnerable prey. ImplicationsCoordinated group-baiting programs are likely to deliver improved lamb survival and should be promoted in areas where ongoing control programs for foxes are necessary.