Fox‐baiting in agricultural landscapes in south‐eastern Australia: a case‐study appraisal and suggestions for improvement

Summary In south‐eastern Australia, the introduced Red Fox (Vulpes vulpes) is a major predator of native wildlife and livestock. Fox control in agricultural landscapes is heavily reliant on the laying of poisoned baits by private landholders, yet there have been few assessments of the application or success of landholder‐baiting practices. We evaluated a community‐based fox‐baiting campaign, typical of programs employed throughout the agricultural regions of south‐eastern Australia to control foxes. We recorded the spatial coverage of 1080 baits deployed by landholders, assessed baiting procedures, monitored the survival of six radio‐collared foxes during and after baiting, and compared the spatial coverage and likely effectiveness of the baiting program with two alternative (theoretical) baiting strategies. Relative to other baiting programs, coordination among neighbours was reasonably high, with 37.5% of baited properties (n = 40) adjoining ≥3 neighbouring properties that also contained baits. Nevertheless, the maximum distance from the centre of a baited property to the nearest edge of an unbaited property was <750 m (mean = 380 m ± 147 m SD). On average, 33% (±17% SD) of each fox’s home range overlapped with baited properties, but only two foxes died during the baiting program. The remaining four foxes were still alive 10 weeks after baiting ceased. Modelling of simulated fox home ranges showed that 13.5% contained no bait stations based on the community baiting program, whereas alternative roadside‐ and grid‐baiting strategies (theoretically) delivered baits to all simulated home ranges. Some landholders employed practices that could reduce the effectiveness of baiting programs such as not removing decayed baits before deploying new ones or placing bait stations too close together. Our research illustrates the difficulties of managing a coordinated baiting program on private land that effectively controls foxes. Alternative baiting strategies such as roadside baiting need to be considered to improve fox control in agricultural landscapes.     

Lethal 1080 baiting continues to reduce European Red Fox (Vulpes vulpes) abundance after more than 25 years of continuous use in south‐west Western Australia

European Red Fox (Vulpes vulpes) baiting with 1080 poison (sodium fluoroacetate) is undertaken in many Australian sites to reduce fox abundance and to protect vulnerable native species from predation. The longest continuous use of fox baiting for fauna conservation commenced in south‐west Western Australia in the 1980s and includes baiting Dryandra Woodland and Tutanning Nature Reserve. The trap success of the Woylie (Bettongia penicillata) in these two reserves initially increased more than 20‐fold after the commencement of baiting and was maintained until 2000. Woylie captures then decreased rapidly, despite ongoing fox baiting, so the long‐term efficacy of 1080 baiting was questioned. Here, fox density and probabilities of detection, re‐detection and survival between replicated baited and unbaited sites were compared by modelling capture–recapture of individual foxes. These were identified from microsatellite DNA genotypes obtained non‐invasively from hair, scat and saliva samples. The frequency and duration of fox residencies were also quantified. Remote cameras were used to determine the fate of baits but uptake by foxes was low, whereas nontarget species' bait uptake was high. Nevertheless, foxes inhabiting baited reserves had significantly higher mortality, shorter residency times, and 80% lower density than foxes inhabiting unbaited reserves. Baiting continues to significantly reduce fox abundance after more than 25 years of continuous use. This has positive implications for fox control programmes throughout Australia but reduced fox abundance may facilitate increased predation by feral Cats (Felis catus).     

Poisoning for production: how effective is fox baiting in south‐eastern Australia?

• 1 The European red fox Vulpes vulpes represents a continuing threat to both livestock and native vertebrates in Australia, and is commonly managed by setting ground‐level baits impregnated with 1080 (sodium fluoroacetate) poison. However, the long‐term effectiveness of such control campaigns is likely to be limited due to the ability of foxes to disperse over considerable distances and to swiftly recolonize areas from where they had been removed.
• 2 To investigate the effectiveness of fox baiting in a production landscape, we assessed the potential for foxes to reinvade baited farm property areas within the jurisdiction of the Molong Rural Lands Protection Board (RLPB), an area of 815 000 ha on the central tablelands of New South Wales, Australia. The spatial distribution and timing of fox baiting campaigns between 1998 and 2002 was estimated from RLPB records and mapped using Geographical Information System software. The effectiveness of the control campaign was assessed on the basis of the likely immigration of foxes from non‐baited farms using immigration distances calculated from published relationships between dispersal distance and home range size.
• 3 Few landholders undertook baiting campaigns in any given year, and the area baited was always so small that no baited property would have been sufficiently far from an unbaited property to have been immune from immigrating individuals. It is likely, therefore, that immigration onto farms negated any long‐term effects of baiting operations. This study highlights some of the key deficiencies in current baiting practices in south‐eastern Australia and suggests that pest management programmes should be monitored using such methods to ensure they achieve their goals.

     

Rapid recolonisation by the European red fox: how effective are uncoordinated and isolated control programs?

Uncoordinated and isolated control programs are often used by land managers, property owners and recreational hunters to control numbers and reduce the impacts of European red foxes (Vulpes vulpes). However, decades of such attempts to eradicate this significant agricultural and biodiversity pest in many countries have failed. We investigated the effectiveness of an uncoordinated and isolated shooting program to determine if it caused any change in red fox population density. We also determined whether shooting is more cost effective than poison baiting for fox control. First, we estimated the density of foxes on an agricultural study property using distance sampling and rates of bait uptake before and after a control program. Second, we estimated the costs associated with undertaking the control program and compared it to the estimated costs of undertaking poison baiting. Prior to control, we estimated a density of 4.18 foxes per square kilometre. After the control exercise, which removed 47 individuals in 12 nights, we estimated a density of 3.26 foxes per square kilometre. Our results provide evidence that one-off control programs are not effective in greatly reducing red fox density, even if the control effort is intensive. Where large-scale control programs cannot be coordinated, isolated programs should therefore involve follow-up campaigns to reduce population recovery. On a local scale, combinations of shooting and baiting may also provide maximum control impact at minimal cost.     

Genetic tagging reveals a significant impact of poison baiting on an invasive species

Globally, invasive predators are major pests of agriculture and biodiversity and are the focus of comprehensive control programs. Because these species are typically elusive, wary of traps, and occur at low densities, their fundamental population dynamics are difficult to determine and quantitative evaluations of control programs are rarely conducted. Noninvasive DNA analysis has the potential to resolve this long-standing limitation to pest management. We carried out a landscape-scale experiment to quantify reduction in the abundance of a red fox (Vulpes vulpes) population when baited with sodium fluoroacetate (1080) poison (the most widely used method of fox control in Australia). We collected fox hairs with hair snares during 4 4-day sessions over the course of 6 months at a site in semi-arid Western Australia. The first session took place in late summer just prior to when juvenile foxes typically disperse, and the final session followed aerial baiting with 1080 poison. We obtained consensus microsatellite genotypes from 196 samples, and used them to conduct both spatially explicit and open model capture–recapture analysis. Twenty-eight percent of trap nights yielded hair samples suitable for identification of individual foxes, which is more than an order of magnitude greater than trapping rates reported with conventional techniques. Fox density changed little during 3 pre-baiting sessions and averaged 0.73 foxes/km² (±0.33 SE), which is less than most previous trap-based estimates for Australian foxes. Density dropped significantly in response to baiting to 0.004 foxes/km². Prior to baiting, the apparent survival of foxes remained static (0.72 ± 0.14 SE), but in response to baiting it dropped precipitously and was effectively zero. This experiment provides the first quantitative assessment of the effectiveness of 1080 poison baiting for reducing fox density, and in this case demonstrates it to be a highly effective method for culling foxes from a region. Further, it demonstrates that noninvasive DNA analysis will provide significantly more data than conventional trapping methods. This method is likely to provide greater precision and accuracy than conventional methods and therefore result in more robust evaluations of management strategies for the fox in Australia, and for cryptic species elsewhere. © 2011 The Wildlife Society.     

Recording fox baiting effort across the landscape using geographic information systems: Facilitating more effective management

Predation on native vertebrates and livestock by the European Red Fox (Vulpes vulpes) remains a significant problem in many parts of Australia. Coordinated approaches to fox control are most effective in protecting these assets and involve placement of baits across the landscape by private and public land managers. However, participation in such programmes varies seasonally and the spatial coverage of baiting is often difficult to determine. Here, we describe a geographic information systems‐based system that assists land managers to collect and use spatial information, minimizing gaps in bait coverage and maximizing bait encounters by foxes to increase the effectiveness of pest control. The coordination of data collection and reporting between land managers should facilitate more effective adaptive management by allowing better strategic planning and increasing landholder involvement, which should, in turn, improve the programme's efficacy, provided other critical conditions and resources are met.     

Not all predators are equal: a continent‐scale analysis of the effects of predator control on Australian mammals

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Did ‘precautionary’ 1080 baiting have a realistic potential to eradicate Red Fox (Vulpes vulpes) in Tasmania without in situ monitoring data?

Anecdotal reports in 2001 suggested that the European Red Fox (Vulpes vulpes) had been deliberately released in Tasmania and thereafter an eradication programme using buried fluoroacetic acid (1080) baits was believed to be a necessary precautionary action until mid‐2013. Prerequisites for the successful eradication of foxes relate to the scale of the undertaking and the ability to collect in situ data such as the distribution and abundance of the target population and measures of the efficacy of the control technique. Previously, 1080 baiting has demonstrated only limited potential as a fox eradication technique on islands when used on a scale between 685 and 2141 times smaller than Tasmania. In the absence of empirical monitoring data confirming the distribution or abundance of extant foxes, buried baiting was targeted to specific landscapes believed to be preferred by foxes. No empirical data was collected concerning the in situ effectiveness of baiting in Tasmania, yet an a priori assumption of lethal efficacy was extrapolated from four heterogeneous mainland studies to suggest that foxes would have only a 0.23 probability of surviving each bait treatment. We show that these studies were unrepresentative of Tasmanian baiting methods used and influenced by imprecise fox population surveys and misreported data. Overall, in the absence of key population monitoring and efficacy data, the ‘precautionary’ baiting strategy adopted did not have a realistic potential to eradicate fox incursions in Tasmania, nor is it an appropriate risk management strategy for other large offshore Australian islands. Contingency plans to counter fox incursions on offshore islands must address the currently inadequate technical capacity to reliably detect and monitor low‐density fox populations, which is an essential component of successful fox eradication.     

Influence of revegetation on predation rates by introduced red foxes (Vulpes vulpes) in south‐eastern Australian farmland

Interactions between wild carnivore abundance and landscape composition in agricultural landscapes are poorly understood despite their importance to both production and conservation. In Australia, introduced red foxes (Vulpes vulpes) prey on both native species and lambs in the temperate agricultural regions. Historically these areas were extensively cleared of native vegetation. Recently revegetation programmes have been implemented, but there is concern that this may benefit foxes and hence increase their impacts. We used an artificial prey placed in eight revegetated (6–12% cover) and 10 cleared (0–1.5% cover) landscapes of ～700 ha to assess how these landscapes influenced fox predation rates. In June and August 2006 (winter) when we expect fox populations to be relatively stable following juvenile dispersal, predation rates were 1.5–2 times higher in revegetated landscapes than in cleared landscapes. We found no evidence of microhabitat effects on predation rates suggesting these landscape‐level differences were probably due to differences in fox population density. In April 2007 (autumn) the results were more variable, possibly indicating more transient populations including dispersing juveniles at this time. Our results suggest that the impact of foxes on highly vulnerable prey could increase with revegetation. However, the benefits of revegetation to prey may offset negative impacts of foxes and future work is required to assess the likely net effects.     

Integrated-baiting concept against Echinococcus multilocularis in foxes is successful in southern Bavaria, Germany

This paper describes the design and the preliminary evaluation of an integrated approach to the control of Echinococcus multilocularis in foxes using praziquantel bait. Air distribution of bait in agricultural and recreational areas was combined with distribution of bait by hand in towns and villages to cover the entire fox population in the 213-km² baiting area. Bait distribution density was 50/km², and bait was distributed once every 4 weeks. Pre-baiting prevalence was 35% (22–50% CI 95%). During a 1-year period following the first 4 months of bait distribution, only one positive fox was found (prevalence 1%; 0–4% CI 95%). No significant change had occurred in the unbaited control area. This prevalence decline is far more pronounced than in previous fox-baiting studies, which is likely to be due to the increased bait distribution density and baiting frequency, and the inclusion of the ‘urban’ fox population.     

Can shooting be an effective management tool for foxes? Preliminary insights from a management programme

Historically, shooting has been a popular method for controlling foxes in Australia, but past research has shown it to be an ineffective method for significantly reducing fox population numbers. These past studies investigated shooting when conducted in isolated, one‐off programmes. In more recent years large, coordinated group fox management programmes has become popular in both agricultural and conservation areas. These landscape scale programmes give more chance of long‐term respite from predation damage by slowing down the immigration rates of foxes into the culled area. Studies have been conducted investigating the effectiveness of large‐scale group fox management programmes that primarily used 1080 baiting as the method of control to protect vulnerable livestock and small animal. This study investigated the potential of a large‐scale group programme that used shooting as the main form of control to reduce the impact of fox predation.     

Predation by red foxes limits recruitment in populations of eastern grey kangaroos

We investigated the impact of red fox (Vulpes vulpes Linnaeus 1758) predation on juvenile eastern grey kangaroos (Macropus giganteus Shaw 1790) using a replicated predator removal experiment. In two sites in Namadgi National Park, south‐eastern Australia, a persistent 1080 poisoning campaign over 18 months reduced fox density by more than 85%, and to less than 10% of the fox density in two other sites with no fox baiting. Changes in the mother : young ratios and densities of kangaroo populations were monitored twice monthly along 2‐km transects in each site from July 1993 to February 1995. Compared to nonremoval sites, where foxes were controlled, 25–40% more females retained juveniles over the period when these young became emergent from the pouch. This higher survival of emergent pouch young resulted in a significantly higher proportion of juveniles in kangaroo populations at fox control sites, which resulted in a significantly higher annual growth rate. We conclude that predation upon juveniles is an important limiting factor for kangaroo populations in Namadgi NP.     

Ecology of wildlife rabies in Europe

• 1 The number of wildlife rabies cases has increased in Europe in recent years. We review the epizootiology of wildlife rabies in Europe, paying special attention to recent changes to the situation of two important vector species: the red fox and the raccoon dog. Red fox Vulpes vulpes has been the main vector of rabies since 1945, but the number and proportion of raccoon dog Nyctereutes procyonoides cases has rapidly increased during the past few years, particularly in north‐eastern Europe.
• 2 The transmission rate (average number of susceptible animals infected by each rabid animal) is critical for rabies spread and is partly determined by population density. Both raccoon dogs and foxes live in pairs. Foxes also live in family groups. Pairs and groups share their territories. Home range size usually correlates negatively with population density. Fox home ranges are 50–1500 ha, those of raccoon dogs 150–700 ha. The threshold value for rabies spread among foxes is estimated to be 0.63 individuals/km². Although fox density in eastern and northern Europe may be lower than this, the pooled density of foxes and raccoon dogs exceeds the threshold density.
• 3 Animal movements, especially dispersal of young, pose a risk for rabies spread. Although the likelihood of an epizootic is highest where fox and raccoon dog densities are highest, rabies may spread fastest where population densities are lower, because dispersal distances tend to correlate negatively with population density.
• 4 Oral vaccinations have been more effective in rabies control than culling foxes. Where two vector species exist, vaccination should be conducted twice a year, because most raccoon dogs disperse in autumn but some foxes do not disperse before mid‐ or late winter.
• 5 New rabies models, based on two vector species and their interaction, and which take into account the hibernation period of raccoon dogs, are needed for north‐eastern Europe.

     

Conventional wisdom on roosting behavior of Australian flying‐foxes—A critical review,and evaluation using new data

1. Fruit bats (Family: Pteropodidae) are animals of great ecological and economic importance, yet their populations are threatened by ongoing habitat loss and human persecution. A lack of ecological knowledge for the vast majority of Pteropodid species presents additional challenges for their conservation and management.
2. In Australia, populations of flying‐fox species (Genus: Pteropus) are declining and management approaches are highly contentious. Australian flying‐fox roosts are exposed to management regimes involving habitat modification, through human–wildlife conflict management policies, or vegetation restoration programs. Details on the fine‐scale roosting ecology of flying‐foxes are not sufficiently known to provide evidence‐based guidance for these regimes, and the impact on flying‐foxes of these habitat modifications is poorly understood.
3. We seek to identify and test commonly held understandings about the roosting ecology of Australian flying‐foxes to inform practical recommendations and guide and refine management practices at flying‐fox roosts.
4. We identify 31 statements relevant to understanding of flying‐fox roosting structure and synthesize these in the context of existing literature. We then contribute a contemporary, fine‐scale dataset on within‐roost structure to further evaluate 11 of these statements. The new dataset encompasses 13‐monthly repeat measures from 2,522 spatially referenced roost trees across eight sites in southeastern Queensland and northeastern New South Wales.
5. We show evidence of sympatry and indirect competition between species, including spatial segregation of black and grey‐headed flying‐foxes within roosts and seasonal displacement of both species by little red flying‐foxes. We demonstrate roost‐specific annual trends in occupancy and abundance and provide updated demographic information including the spatial and temporal distributions of males and females within roosts.
6. Insights from our systematic and quantitative study will be important to guide evidence‐based recommendations on restoration and management and will be crucial for the implementation of priority recovery actions for the preservation of these species in the future.

     

Bait Uptake and Caching by Red Foxes and Nontarget Species in Urban Reserves

Abstract: The management of biodiversity in urban areas provides a challenge for conservation managers who are interested in the recovery of native species by controlling exotic species. Exotic-animal control programs using poisons can be contentious in terms of the health and safety of nontarget species, including people. Managing exotic predators in urban areas must be effective at 2 levels: controlling the target species and minimizing impacts to nontarget species. We investigated the feasibility of instigating a poison-baiting program to control nonindigenous European red foxes (Vulpes vulpes) in city conservation reserves (Perth, Australia). We selected 3 reserves to assess the safety and efficacy of baiting for foxes by maximizing bait uptake by the target species, and minimizing uptake by nontarget species. We tested 2 types of meat bait using 4 bait presentation methods (untethered, uncovered; untethered, covered; tethered, uncovered; tethered, covered). Bait uptake by foxes was highest in urban reserves compared to that in a peri-urban reserve. Bait type and presentation method equally explained bait uptake by foxes. Untethered and uncovered baits were removed 10% more often by foxes, and untethered baits had been cached more often than tethered baits. Baits cached by foxes for up to 1 week were not removed by species other than foxes. Domestic dogs and native birds were common nontarget species to remove baits. Dogs showed no aversion to removing any bait type, nor did bait presentation method influence bait removal. Birds removed fewer baits that had been tethered and covered. We provide an evidence base to demonstrate that bait uptake by nontarget species can be minimized, although we suggest that a fox control program is likely to be more of an organizational challenge to change public attitudes toward responsible dog ownership rather than a technical challenge to poison foxes.     

Recent invasion of European red foxes (Vulpes vulpes) on to Fraser Island (K'gari) and South Stradbroke Island

Invasive predators are globally significant drivers of threatened fauna population decline and extinction, and the early detection of new incursions is critical to the chances of successful predator eradication and fauna conservation. Here, we provide evidence of the recent invasion of European red foxes (Vulpes vulpes) on to two large and internationally significant islands off the southeast coast of Queensland, Australia – Fraser Island (K'gari) and South Stradbroke Island. From camera trap footage collected on Fraser Island since 2009, foxes have now been observed on seven different occasions between 2012 and 2016. Two scats collected on South Stradbroke Island in 2013 and 2014 tested positive for fox DNA (and negative for Canis spp. DNA), with fox presence confirmed by subsequent camera trap footage in 2016. These data confirm the recent incursion of foxes on to these islands and suggest that small populations now exist there. Fraser Island and South Stradbroke Island represent key RAMSAR wetland areas of refuge for populations of multiple threatened fauna that have never been previously been exposed to foxes. Fox impacts on these fauna can only be expected to increase without management intervention to eradicate them before they become widespread.     

Does Fire Influence the Landscape-Scale Distribution of an Invasive Mesopredator?

Predation and fire shape the structure and function of ecosystems globally. However, studies exploring interactions between these two processes are rare, especially at large spatial scales. This knowledge gap is significant not only for ecological theory, but also in an applied context, because it limits the ability of landscape managers to predict the outcomes of manipulating fire and predators. We examined the influence of fire on the occurrence of an introduced and widespread mesopredator, the red fox (Vulpes vulpes), in semi-arid Australia. We used two extensive and complimentary datasets collected at two spatial scales. At the landscape-scale, we surveyed red foxes using sand-plots within 28 study landscapes – which incorporated variation in the diversity and proportional extent of fire-age classes – located across a 104 000 km² study area. At the site-scale, we surveyed red foxes using camera traps at 108 sites stratified along a century-long post-fire chronosequence (0–105 years) within a 6630 km² study area. Red foxes were widespread both at the landscape and site-scale. Fire did not influence fox distribution at either spatial scale, nor did other environmental variables that we measured. Our results show that red foxes exploit a broad range of environmental conditions within semi-arid Australia. The presence of red foxes throughout much of the landscape is likely to have significant implications for native fauna, particularly in recently burnt habitats where reduced cover may increase prey species’ predation risk.     

Toward reliable population density estimates of partially marked populations using spatially explicit mark–resight methods

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Ineffectiveness of plastic mesh for protecting artificial freshwater turtle nests from red fox (Vulpes vulpes) predation

Invasive mammalian predators are efficient at driving native animal declines. The red fox (Vulpes vulpes) kills millions of endemic reptiles in Australia each year. In areas of south-eastern Australia, the eastern long-necked turtle (Chelodina longicollis) and Murray River turtle (Emydura macquarii) have declined by more than 50%. High rates of nest predation by foxes limit the recruitment of young turtles in these populations, but previous methods of fox control have been ineffective at protecting turtle nests. Here, we tested the effectiveness of plastic mesh for protecting artificial turtle nests from predation by foxes, in the mid-Murray catchment, Victoria. We also tested whether protecting a large number of artificial nests in a given area encourages foxes to give up foraging following predictions from giving-up density theory. We made a series of plots, each containing 32 artificial turtle nests. In each plot, we covered a percentage (0%, 25%, 50%, 81% or 100%) of the nests with either 1 or 2 sheets of plastic mesh. We used remote cameras to photograph and identify any predator that attacked nests in the plots. The cameras also allowed us to estimate the amount of time a fox was visible on each plot, as a metric of how much effort foxes expended on protected nests. Nest survival rate was not increased by either 1 or 2 sheets of mesh, and increasing the number of protected nests on a plot did not reveal a giving-up density (GUD) value for fox foraging behaviour. Our study demonstrates that plastic mesh is not effective for protecting artificial turtle nests from foxes in this region.     

Does culling reduce fox (Vulpes vulpes) density in commercial forests in Wales, UK?

Forests within agricultural landscapes can act as safe harbourages for species that conflict with neighbouring landowners’ interests, including mammalian predators. The agency responsible for the management of forests in upland Wales, UK, has permitted the killing of foxes (Vulpes vulpes) on their land as a “good neighbour policy” with the aim of reducing fox numbers. The principal method used was the use of dogs to drive foxes to a line of waiting shooters; a small number of foxes were also killed by shooting at night with a rifle. However, it has been postulated that recent restrictions on the use of dogs to kill foxes in Britain could lead to an increase in fox numbers in plantations. The aim of this study was to determine whether over-winter culling (i.e. driving foxes to guns using dogs and rifle shooting) in these forests acted to reduce fox density. Fox faecal density counts were conducted in commercial forests in Wales in autumn 2003 and spring 2004. Data were analysed from 29 sites (21 individual forests and 8 forest blocks, the latter consisting of pooled data from 20 individual forests). The over-winter change in faecal density was negatively related to the proportion of felled land and the proportion of land more than 400 m altitude, these associations probably reflecting reduced food availability. Over-winter change was positively associated with culling pressure (i.e. more foxes were killed where more foxes were present, or vice versa), but this was not significant. The number of foxes killed was large relative to the estimated resident population, but losses appeared to be negated (most likely) by immigration. Pre-breeding (spring) faecal density counts were significantly positively related to culling pressure, i.e. more foxes were killed with increased fox density or vice versa. Overall, there was no evidence to suggest that culling reduced fox numbers. Consequently, restrictions on the use of dogs to control foxes are unlikely to result in an increase in fox numbers in commercial forests.