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The Australian brushtail possum (Trichosurus vulpecula) is adapted to a wide range of food plants across its range and is exposed to numerous physiological challenges. Populations that are resistant to the plant toxin sodium fluoroacetate are of particular interest as this compound has been used since the 1940s for vertebrate pest management around the world. Candidate gene identification is an important first step in understanding how spatial populations have responded to local selection resulting in local physiological divergence. We employ differential gene expression of liver samples from wild-caught brushtail possums from toxin-resistant and toxin-susceptible populations to identify candidate genes that might be involved in metabolic pathways associated with toxin-resistance. This allowed us to identify genetic pathways involved in resistance to the plant toxin sodium fluoroacetate in Western Australian possums but not those originally from south eastern Australia. We identified differentially expressed genes in the liver that are associated with cell signalling, encapsulating structure, cell mobility, and tricarboxylic acid cycle. The gene expression differences detected indicate which metabolic pathways are most likely to be associated with sodium fluoroacetate resistance in these marsupials and we provide a comprehensive list of candidate genes and pathways to focus on for future studies. [ABSTRACT FROM AUTHOR]

Context: Feral cats (Felis catus) have an impact on native wildlife populations around the world but are difficult to control because of their neophobic behaviours and preference for live prey over scavenging poisoned baits. Felixers™ address these challenges by squirting poison-gel directly onto feral cats, exploiting their fastidious oral grooming tendencies to facilitate poison ingestion. Aims: This study trialled Felixers in a landscape-scale arid-ecosystem site to assess their capacity to sustainably manage cat populations in a semi-bounded in situ predator training area and to eradicate cat incursions into a feral-free safe haven. Specifically, the aims were to determine target specificity and firing rates; optimise installation sites to exploit cat behaviour and landscape features; assess the fate of individuals following Felixer interaction; and assess the overall cost, performance and efficacy of Felixers compared with conventional cat control methods. Methods: Up to nine Felixers were simultaneously deployed across three trial periods, spanning 30 months (4,642 trap nights) in Sturt National Park in the Strzelecki Desert dunefields of Australia. Felixers were deployed within and outside of feral-free safe havens, at varying cat densities, with populations monitored through camera-trap activity indices and individual behaviour monitored through satellite tracking. Key results: Felixers fired at 20.3–43.9% of cats that passed in front (292 of 1,144 cats), with the remainder failing to satisfy the discriminatory algorithm's target criteria. The devices had 99.93% target specificity from 17,425 interactions with moving animals and objects. Overall cat activity was lower in a semi-bounded 10,400 ha landscape-scale area where Felixers were intensively used, relative to an adjacent unbounded area where no cat control was occurring, over a 12-month subset of the 30-month trial. Felixers also resolved one of two incursions by cats into a 2,000 ha safe haven. Optimisation of Felixer placement and upgrading of software drove improvements in technical reliability and target identification during the trial. Shortcomings included cost and high incidence of technical faults, causing significant downtime and requiring regular investment of field staff time for monitoring and resolution. Conclusions: Felixers provide a safe tool for cat management and eradication at intensively managed conservation sites. Efficacy could be improved through reductions in cost and improvements in reliability. Implications: Overall Felixers appear to be an effective tool for cat management, when used in an integrated approach. Feral cats are a key threat to biodiversity globally, and particularly in Australia, but effective control is complex because of their broadscale distribution and behaviour. Felixer grooming traps were evaluated at a mammal reintroduction site in the Strzelecki Desert, Australia. Felixers showed extremely high target specificity, low incidence of non-target firing events and appear to have supressed cat activity in a semi-bounded area relative to an adjacent unbounded area where no cat control was occurring. The devices had high cost and incidence of technical faults, but showed promise as highly targeted feral cat control tools. Photograph by Reece Pedler. [ABSTRACT FROM AUTHOR]

Context: Toxic meat baits are the most effective broadscale method used for reducing the densities and impacts of feral cats (Felis catus) on vulnerable Australian native fauna when alternative prey is minimal. Aims: Our aim was to assess the efficiency (proportion of baits removed by target animals) and effectiveness (proportion of target animals removed) of Eradicat ® baits and to identify how their use may be improved in Southern Jarrah Forest ecosystems of Western Australia. We sought to determine how, when, and where best to deploy baits using the current Eradicat ® bait prescriptions to maximise the reduction of feral cats. Methods: Eradicat ® uptake trials were conducted over a 15-month period using remote sensor cameras (RSCs) to observe animals interacting with the baits at 40 sites. Ten successive baiting trials were conducted, each involving four randomly selected sites (two replicates for each of two bait deployment methods: clusters and transects). Key results: The fate of 5658 Eradicat® baits at 2000 bait locations was recorded during 54,361 camera trap nights. Despite occupancy rates being high for cat and fox (Vulpes vulpes), (92% and 84%, respectively), the efficiency and effectiveness of Eradicat ® baits was low for both introduced predators (cat: 0.1% and 10–12%, respectively; and fox: <0.6% and 8–20%, respectively). There were no major differences in baiting efficiency in relation to bait deployment method or time of year. More than half (56–58%) of the baits were removed by non-target animals prior to an introduced predator being observed on camera at the bait location. Along transects, there were more cat and fox visits closer to tracks and surface water features. Foxes were also more likely to visit bait locations closer to private property. Younger cats appeared to be more interested and more likely to eat a bait than older cats. Conclusions: Substantial improvements could be made by increasing bait availability (reducing non-target interference), detectability and attractiveness to cats. Implications: Additional introduced predator threat abatement methods may be needed for the conservation and recovery of many threatened native mammals in the Southern Jarrah Forests and elsewhere in Australia. Feral cat baiting should be conducted within an integrated and holistic invasive animal management system. Improving the management of feral cats is paramount for the conservation and recovery of many threatened Australian mammals. This study found that the efficiency and effectiveness of Eradicat ® baits in the Southern Jarrah Forests of Western Australia were low. We provide recommendations for improvements within an integrated and holistic invasive animal management framework to deliver better biodiversity conservation outcomes. Photograph by Marika Maxwell/DBCA. [ABSTRACT FROM AUTHOR]

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Sodium fluoroacetate (1080) is a vertebrate pesticide principally used to control unwanted introduced mammals in New Zealand and Australia. For 1080, over 260 publications during the last ten years supplement a body of scientific information regarding its mode of action, natural occurrence, toxicology, antidotes, metabolism, and fate in the environment. Multi-year studies have explored long-term outcomes for multiple native bird species. Numerous reviews on community attitudes stimulated by the Predator Free New Zealand (PFNZ) 2050 campaign conclude that 1080 use for conservation remains controversial. Further effort is needed to increase target specificity, avoid game species, and employ approaches with the highest public acceptance, including hunting, trapping, and species-specific toxins. Greater acceptance of the large-scale use of any pest control is likely when long-term goals and strategies for ecosystem recovery employ toxins as one-off treatments for eradicating pests versus continued applications.

Context: The introduced red fox has driven the decline or extinction of numerous wildlife species in Australia, yet little information exists on the population densities of foxes in most ecosystems. Fox monitoring programs will differ widely depending on the goals of management, which, in turn, will determine whether the appropriate metric is a density estimate, or some proxy thereof, and the time and resources required. Aims: This study aims to assist wildlife managers to design fit-for-purpose monitoring programs for foxes by providing a better understanding of the utility and precision of various monitoring methods. Methods: We surveyed foxes monthly over four consecutive years in a semi-arid region of Australia by using sand plots, camera traps and GPS telemetry. The resultant data were used to produce population estimates from one count-based method, two spatially explicit methods, and two activity indices. Key results: The incorporation of GPS-collar data into the spatial capture–recapture approaches greatly reduced uncertainty in estimates of abundance. Activity indices from sand plots were generally higher and more variable than were indices derived from camera traps, whereas estimates from N-mixture models appeared to be biased high. Conclusions: Our study indicated that the Allen–Engeman index derived from camera-trap data provided an accurate reflection of change in the underlying fox density, even as density declined towards zero following introduction of lethal control. This method provides an efficient means to detect large shifts in abundance, whether up or down, which may trigger a change to more laborious, but precise, population monitoring methods. If accuracy is paramount (e.g. for reintroduction programs) spatially explicit methods augmented with GPS data provide robust estimates, albeit at a greater cost in resources and expertise than does an index. Implications: Our study demonstrated that the shorter the survey period is, the greater is the likelihood that foxes are present but not detected. As such, if limited resources are available, longer monitoring periods conducted less frequently will provide a more accurate reflection of the underlying fox population than do shorter monitoring periods conducted more often. Foxes threaten the survival of many Australian wildlife species, yet little is known about their population numbers. We monitored a fox population for four consecutive years and compared a variety of monitoring methods and analytical techniques. Our findings will help land managers design fit-for-purpose monitoring programs to better understand the threat posed by foxes and the efficacy of efforts to manage their populations. Photograph by Andrew Carter. [ABSTRACT FROM AUTHOR]

Efforts to mitigate the effects of feral cats through the management of remnant or reintroduced populations of threatened species, are often unsuccessful due to predation by control-averse feral cats, or 'problem individuals'. In order to target these animals, we have developed the Population Protecting Implant (PPI). PPIs are designed to be implanted subcutaneously in a native animal. If the animal is preyed upon, and the implant ingested by a feral cat, release of a toxic payload is triggered in the acidic stomach environment and the problem individual is eliminated. We introduce the first toxic implant incorporating the poison sodium fluoroacetate. Manufactured via fluidised-bed spray coating, toxic implants exhibited uniform reverse enteric coatings and low intra-batch variation. Toxic implants were found to exhibit favourable stability at subcutaneous pH in vitro, and rapidly release their toxic payload in vitro at gastric pH. However, limited stability was demonstrated in rats in vivo (~39–230 d), due to the use of a filament scaffold to enable coating and was likely exacerbated by metachromatic interactions caused by 1080. This work highlights that future development of the PPIs should primarily focus on removal of the filament scaffold, to afford implants with increased in vivo stability. [ABSTRACT FROM AUTHOR]

Public support is crucial to the widespread application of pest control methods both in the form of political support and, where people have direct agency in control methods, compliance with the demands of the methods. It is commonplace for personal behaviours reflecting political support for public policies to be presumed to depend on relevant attitudes, beliefs and values of the person. The finite amount of attention and cognitive effort each person possesses implies that attention and effort are rationed, indicating that changing behaviour requires that the targeted individual is attentive and willing to invest the required cognitive effort; that is, they are motivated to consider new information and, subsequently, to reviewing their attitudes and behaviour. We examine whether attitudes and involvement (a measure of motivation) together provide better predictions of public support for pest control methods than attitudes alone, using the distribution of baits containing sodium fluoroacetate (1080) in New Zealand to control invasive, non-native rats and possums as a case study. We found the novel combination of involvement and attitudes did provide significantly better predictions of an individual's support for using 1080 for the purpose of environmental conservation, and their pest control behaviour, than did attitudes alone. [ABSTRACT FROM AUTHOR]

A 2014 carcass search survey confirmed that Tiakina Ngā Manu aerial 1080 operations, undertaken to protect resident mohua (Mohoua ochrocephala) from increases to predator populations following substantial beech (Nothofagus sp.) mast events, cause mortality for Wakatipu white-tailed deer. Non-target by-kill of deer generates significant public opposition to predator control operations. We assessed if a current deer repellent (EDR) and a repellent in development (Pestex-DR) were effective at repelling captive white-tailed deer from consumption of nontoxic baits, commonly used in Tiakina Ngā Manu operations. Both repellents were found to significantly decrease bait consumption, and we observed clear displays of aversion to repellent baits by captive deer. Ten GPS collared wild white-tailed deer were then monitored following a Tiakina Ngā Manu operation using EDR in 2016. One collared deer was poisoned following the operation, confirming that EDR is not 100% effective. We recommend the most effective available deer repellent be used for future Tiakina Ngā Manu operations over the Wakatipu white-tailed deer habitat to minimise public opposition to these predator control operations. In addition, our results suggest that differences in the boundary size and shape of operations may account for some of the variability in non-target by-kill observed between studies. [ABSTRACT FROM AUTHOR]

The ongoing use of 1080 toxin for the control of mammal pests in New Zealand remains highly contentious. Several reviews over the last 25 years identified information gaps and areas of concern, both social and scientific. In this paper these areas of concern are discussed and the extensive scientific and social research that has been undertaken to clarify and address them is reviewed. Although there has been a major national investment in research aimed at finding an alternative to 1080, that has not yet been fully achieved because of low or inconsistent efficacy and/or low cost-effectiveness of alternatives, regulatory difficulties in obtaining approval for aerial delivery of any alternative, and toxic residue concerns. Finding an alternative that has similar efficacy while satisfying the demands for species-selectivity, no residues, and humaneness is a continuing challenge. The most promising prospect appears to be through understanding the genome of the target animals and opportunities for genetic manipulation, either by developing species-specific designer lethal toxicants based on genome mining, or by gene editing to develop non-lethal technologies. Both will require considerable time and funding for research, and considerable effort and engagement to address social and regulatory hurdles. [ABSTRACT FROM AUTHOR]

Stoats are implicated in the severe decline of certain iconic endemic species in New Zealand. Stoats are notoriously difficult to control, as they are highly cryptic and often neophobic around control techniques such as traps and poison baits in tunnels. Stoats are often killed through secondary poisoning in both aerial and hand-lay operations targeting other mammalian pests. We prototype trialled a novel approach to poisoning of stoats: wild-caught ship rats that had consumed (and subsequently died from) a lethal dose of 1080 cereal baits in a captive facility. Stoats in the treatment area were targeted at food-lured (egg mayonnaise) camera trap sites that had multiple stoat visitations prior to baiting with toxic rat carcasses. Stoats were recorded taking toxic rat carcass baits from 7 out of 15 hand-laid sites. No other species were observed taking toxic rat carcasses during the study. The number of cameras in the treatment area that detected stoats was significantly reduced for 30 days after toxic baiting. There was no significant difference in number of cameras that detected stoats during this period in the non-treatment area. These results suggest that 94% of the stoats in the treatment area were poisoned using toxin-laced rat carcasses within one week of baiting. Toxic rat carcass baits placed at locations of known stoat activity may be a highly successful method of eliminating individual stoats at very low density. [ABSTRACT FROM AUTHOR]

Feral cats (Felis catus) pose a significant threat to wildlife, agriculture, and human health through predation, disease transmission, and competition with native animals. Controlling feral cats and their impacts, however, is challenging. New and emerging 1080‐based feral cat baits have shown promising results in western and central Australia; however, the safety of these new baits for nontarget species in eastern Australia, where many native animals are more sensitive to compound 1080 (sodium fluoroacetate) than their western conspecifics, has not been assessed. We investigated the uptake of 499 toxic Eradicat® baits by nontarget animals across five different eastern Australian environs and the uptake of nontoxic Eradicat and Hisstory® baits at an additional two sites. Using field‐based observations of species eating or removing baits, we determined that 13 nontarget species (eight mammals, four birds, and one reptile) were at high risk of individual mortality, with individuals of 11 of those 13 species (seven mammals, four birds) observed consuming enough toxic Eradicat in a single visit to ingest a lethal dose of 1080. Feral cats (the target species) consumed only 3.1% of monitored baits, which was only 52% of the 31 baits they encountered. We recommend undertaking targeted population monitoring of species identified at high risk of individual mortality, to determine whether Eradicat baits present a population‐level risk to these species. Our findings suggest that the small‐sized Eradicat baits present a greater risk to nontarget species in eastern Australia than the larger traditional 1080‐based meat baits used for the control of wild dogs and foxes. Our study highlights the importance of performing risk assessments for different bait types, even when the same toxin is used, and of performing site‐specific nontarget risk assessments of new baits such as Eradicat to assist developing guidelines for their safe and effective use in different environs. Integr Environ Assess Manag 2022;18:224–244. © 2021 State of Queensland. Integrated Environmental Assessment and Management © 2021 SETAC. KEY POINTS: New feral cat baits have shown promising results in western and central Australia and are considered safe for many non‐target native species in those regions due to a long‐term evolutionary exposure to fluoroacetate‐bearing plants, giving them an increased tolerance to the toxin used in baits. We present a comprehensive field assessment of the risk of Eradicat® feral cat baits to non‐target species in eastern Australian environs, where native animals do not share the same evolutionary exposure and tolerance to the toxin as their western conspecifics. Most baits were swiftly removed by non‐target native mammals, birds and reptiles, 13 of which were at high risk of individual mortality, with most species consuming more than enough toxic bait in a single visit to ingest a lethal dose. Our findings will help inform operational risk assessments, thereby enabling land managers to adapt control programs to manage non‐target risks to local faunal communities on a site‐by‐site basis in accordance with local management requirements and objectives. [ABSTRACT FROM AUTHOR]

Introduced rats continue to have a major impact on biodiversity around the world, and improved control techniques are required to avoid further extinctions. We are trialing re-setting toxin-delivery systems (Spitfires) targeting a range of predators, including rats. The rat Spitfire works by firing 800 mg of a toxic paste onto the belly of the rat as it passes through a tunnel; the device then resets. When the rats groom the paste from their fur, they ingest the toxin. Each Spitfire is capable of approximately 100 doses and is fitted with a counter and a delay mechanism. We trialed 0.55% 1080 paste in the Spitfire and 15 of 15 wild Norway rats and 14 of 15 black rats died. Further trials are planned with a range of toxins to allow flexibility of use. Resetting devices that are expected to work for long periods without being serviced also require long-life lures. Preliminary trials showed urine and scats from female Norway rats were attractive to both male and female Norway rats. The volatile components from these and further trials will be identified to aid in developing a long-life lure. The long-term, effective control of introduced rats will require a range of toxins with different modes of action, a number of different delivery systems, and long-life lures.

Intensive ground-based searches for white-tailed deer carcasses were conducted in the Dart Valley/Routeburn catchments following the aerial application of 1080 (sodium fluoroacetate) cereal pellets as part of the 'Battle for the Birds'/ Tiakina Ngā Manu predator control program in August 2014. Four 100 ha areas were searched over four days. The detection rate of simulated carcasses allowed an estimation of the success rate for finding deer carcasses. All white-tailed deer carcasses located were confirmed to have muscle tissue containing traces of 1080 (range: 0.41–1.06 mg/kg). The detection rate of simulated carcasses was 78% (312/400). The adjusted number of dead white-tailed deer was 3.85 ± 0.85 (95% CI) over the 400 ha (0.96 deer/km2) suggesting a potential mortality of 146 ± 32 (95% CI) white-tailed deer in the predator control area of 15,215 ha. These results suggest that recurrent predator control operations may have implications for sustainable hunting of white-tailed deer. [ABSTRACT FROM AUTHOR]

We assessed the effect of aerial 1080 control of possums (Trichosurus vulpecula), ship rats (Rattus rattus) and stoats (Mustela erminea) on the survival and nest success of South Island robins (Petroica australis) at Tennyson Inlet, Marlborough Sounds, from 2012-2017. Cereal baits containing 1080 were applied in 2013 when rat and stoat numbers were low, and again in 2014 after a beech mast when rat numbers were high. Survival rates of 134 banded adult South Island (SI) robins and 209 SI robin nests were monitored. Ship rats were the main predator of eggs and chicks, with stoats, possums and ruru (Ninox novaeseelandiae) also preying on nests. Rats were the only predator identified killing adult females on the nest. Nest success was negatively affected by rat abundance and increased when 1080 reduced rat abundance. Our study did not detect a measurable negative effect of aerial 1080 use on nest success or adult survival, although over the course of the study two nests failed and two adults disappeared while 1080 was present in the forest. The positive effect of aerial 1080 pest control was short-lived, with rat numbers increasing rapidly in subsequent years. To achieve long-term population benefits in small beech forest blocks, future pest control operations will need to achieve higher rat kills in beech mast years, and/or be undertaken at roughly three yearly intervals. [ABSTRACT FROM AUTHOR]

A field-based experiment was carried out to determine if watercress, commonly harvested by Māori, the indigenous people of New Zealand, could take up the vertebrate pesticide sodium fluoroacetate (Compound 1080), often applied aerially in New Zealand for the control of introduced vertebrate pests. Single toxic baits were placed within seven watercress stands, while three stands received non-toxic controls. Water and plant tissue samples were taken out to 17 days after bait placement, and samples analysed for 1080 content. 1080 was recorded from treatment watercress samples, with a maximum concentration of 63 ppb recorded on Day 7. Subsequent sampling did not show any 1080 in watercress tissue. It is concluded that there is a negligible secondary poisoning risk to humans via consumption of watercress after exposure to 1080.

Compound 1080® is a man-made sodium salt of fluoroacetic acid or fluoroacetate, which occurs in nature as the toxin in many species of poisonous plants. The toxicity of such plants had long been recognized, but the toxic agent was not identified as fluoroacetate until 1944. By that time, the pesticidal potential of synthesized sodium fluoroacetate (code number 1080-44) was being explored in the United States in wartime, crash program aimed at finding new rodenticides. Compound 1080, the main product of that program, proved to be the best rodenticide known up to that time. It was found to be even more toxic to canids than to rodents, so was used experimentally for coyote control beginning in November 1944. Compound 1080 was authorized for operational use in governmental predator control in 1946. Large meat baits, or bait stations, injected with 1080 solution and placed on livestock ranges in winter quickly became a preferred method for reducing coyote populations that preyed on sheep and cattle. The use of 1080 bait stations peaked in Fiscal Year (FY) 1963, when over 16,000 stations were placed by the U.S. Fish and Wildlife Service Predator and Rodent Control program. After 1963, numbers of 1080 stations declined year by year to 1972 when the use of 1080 and other predacides on Federal lands and in Federal programs was stopped by President Nixon’s Executive Order 11643, followed by Environmental Protection Agency suspension and cancellation of registrations for 1080 and other predacides. The 1080 cancellation was based partly on high potential hazard to humans, even though no human had ever been killed or seriously injured in connection with the use of this toxicant in coyote control. Paradoxically, most of the political agitation over Compound 1080 focused on its use in predator control, even though much greater amounts were used for rodent control. The total amount of 1080 sold in the U.S. during 1968-1972, the last 5 years in which 1080 bait stations were used, was approximately 10,003 lb. Only 1.3% (129 lb) of that amount was used for predator control. The largest amount of 1080 used for coyote control in the United States in any one year was about 42.4 lb, in FY 1963.

It was hypothesised that reintroduction of Australian native mammals, currently being severely impacted by feral cat predation, would be more successful if these mammals could have a retained toxicity as discussed in historical accounts. Seeds from the Australian genus Gastrolobium (Fabaceae: Mirbelieae) were analysed in the search for a toxicant that would explain historical accounts of toxic wildlife. Numerous accounts referring to bronzewing pigeons having toxic bones were specifically noted. Analysis of this seed found no evidence for rapidly toxic alkaloids previously reported as being extracted from the leaves of York Road poison and box poison. However, evidence for the presence of organo-fluorine compounds in addition to the reported fluoroacetate (Compound 1080) was discovered. A limited cat dosing trial found that a highly fluorinated box poison seed caused a cat to cease respiration in 82 minutes, but its chloroform extract produced no adverse physiological response. In addition, citrate accumulation appeared more rapid and acute with increasing seed ‘total fluorine.’

Feral pigs occupy 40% of Australia along with numerous other countries. They cost Australian agriculture greater than AUD$100 M annually through stock predation and crop, pasture, and infrastructure damage. Broad-scale, integrated poisoning campaigns, predominantly using Compound 1080, are the most practical and cost-effective control method in Australia. However, the lack of a target-specific toxicant and bait for feral pigs means that baiting campaigns can place non-target species at risk. Confounding this is the wide distribution and diet of feral pigs in Australia, which means that no current single bait is effective for all feral pigs. A potential solution to this problem is to use the known ecology, genetics, and socio-biology of feral pigs in different habitats to design bait(s) with increased target specificity, then combine this with habitat-specific operating procedures inferred from ecological and genetic studies to reduce non-target exposure. This process is currently underway in Australia. Habitat-independent characteristics of feral pigs that can be used to develop target-specific baits are their large size and strong jaws, their keen sense of smell, their poor vision, their omnivorous diet, and their nocturnal and fossorial nature. Producing large, tough, odorous, dyed (to deter birds), meat and vegetable (to deter obligatory carnivores or herbivores) baits that are laid at night and buried where possible will make feral pig baits more target specific and reduce non-target exposure. Current pen and field trials of bait prototypes in a range of habitats are confirming this. Appropriate baiting regimes for feral pigs in different habitats, as determined through ecology and genetics and subsequent field trials, are presently being determined and transformed into standard operating procedures to lessen non-target exposure. The planned incorporation of more target-specific toxins or ‘Achilles Heel’ approaches in the future should further increase the target specificity and humaneness of broad-scale feral pig control. This protocol can potentially improve target-specificity of baits and baiting procedures for other pest animals.

Around NZ$76 million per annum is presently spent on controlling and researching the introduced brushtail possum in New Zealand. The national control effort is likely to be further increased over the next decade in an attempt to eradicate bovine tuberculosis and to arrest the degradation of key conservation areas. There is a risk that repeated control operations using toxic baits could result in widespread development of learned “bait-shyness,” behavior that develops when sublethally poisoned animals are able to link the experience of an illness with the memory of the bait eaten. Four studies are reviewed that aimed to determine the likelihood of possums becoming shy after sublethal doses imparted by different types of toxic bait, and to find solutions to the problem. Captive possums were presented with baits containing sublethal doses of the 4 vertebrate pesticides commonly used. Following a recovery period, possums were presented with lethal baits and their response compared with that of naive possums. Between 15% and 90% of possums previously dosed with sublethal doses of cyanide, 1080, or cholecalciferol developed bait-shyness, the proportion being dose and toxicant dependent. Although cholecalciferol induces toxicosis more slowly (i.e., >24 h) than cyanide (5 min) and 1080 (1 h), possums were nevertheless able to associate the effects of this toxicant with consumption of the bait in which it was delivered and avoid eating further baits. However, brodifacoum acts very slowly (1-4 weeks), and possums did not become shy towards baits containing this toxicant after first eating sublethal baits. Shyness induced by either 1080 or cyanide persisted for at least 12 and 24 months respectively, thus jeopardizing the effectiveness of “maintenance” control operations, which can be required every 12 months or less. The persistence of bait-shyness to cholecalciferol remains untested. Use of alternative baits (bait-switching) proved an effective solution for eliminating cyanide- and 1080-induced bait-shyness. Baits containing brodifacoum can also be used very effectively to “mop up” bait-shy populations, but care must be taken to minimize environmental contamination by this persistent compound.

Bennett’s wallaby (Macropus rufogriseus) was introduced to South Canterbury in New Zealand’s South Island in 1974. The species rapidly increased in numbers, and by the 1940s had increased to levels where it had become a significant agricultural pest. In 1947, a coordinated wallaby control program employing teams of shooters commenced. However, wallaby numbers stayed high, and it was not until the early 1960s when aerially sown 1080 baits were used that a significant reduction in wallaby numbers was achieved. However, the need to de-stock areas prior to application of the baits prompted fanners to demand control by shooting teams rather than poison in order to achieve ongoing control. Wallaby control in South Canterbury is managed under a Regional Pest Management Strategy, relying on shooting as the primary form of control, but using aerially distributed 1080 baits and 1080 gel applied to broadleaf foliage to a limited extent when and where necessary. Wallabies are continuing to expand their range into the central alpine region adjacent to South Canterbury where they are becoming a conservation threat on public lands. In this study, we re-analyzed 13 years of detailed hunting return data in order to derive a synoptic model of wallaby population growth relative to density and prevailing rainfall. We also estimated cost-effectiveness models for control employing shooting teams, aerially distributed 1080 baits, and 1080 gel applied to foliage. We then explored the cost-effectiveness of alternative strategies for wallaby control by combining the models predicting wallaby population growth with those predicting variation in the cost-effectiveness of available techniques. The implications of this study for ongoing wallaby control for mitigation of agricultural and conservation impacts are discussed.

Fox predation has long been suspected as a major cause of lamb death in southern Australia. The response of farmers has been to poison foxes using sodium monofluoroacetate (compound 1080). This has become more widespread in recent years due to a number of factors including the reduced returns from sale of skins which has made shooting foxes unprofitable. In a replicated experiment we investigated the effect of fox control on lamb survival. Fox baiting was implemented at three levels; no baiting, baiting once a year before lambing (the recommended practice), and baiting three times a year. This was carried out on sheep properties with ultrasounded flocks over three years. The experiment was conducted in central New South Wales, Australia, in an area where wild dogs and native dingoes had been eradicated. Foxes, an introduced species, were the major mammalian predators of lambs in the district, as estimated from previous post-mortems of lamb carcasses. No significant difference was detected in lambing, as measured by the number of lambs per ewe at lamb marking 8 to 10 weeks after birth, however, there was a significant effect of fox control on the number of healthy lambs killed by foxes assessed by lamb post-mortems. The possible reasons for this result are discussed including features of the experimental design and the level of replication.

Dingoes and other wild dogs cause substantial damage and control expense in many Australian environments. The main methods of control are exclusion fencing, poisoning with 1080, and trapping. Strategies to mitigate livestock predation by wild dogs include; enterprise substitution, the reduction of wild dog populations, and baited buffer zones between wild dog country and sheep country. Damage functions show significant positive relationships between density indices and the losses caused by predation for both sheep and cattle enterprises. However, descriptive and explanatory models fitted the data poorly. A strategic approach to the management of wild dogs that aims to reduce predation on livestock while allowing the conservation of wild living dingoes is also outlined.

The fundamental assumption in the management of predators is that reducing predator numbers will reduce their predation impact on livestock. Research on dingoes (Canis lupus dingo) has shown this assumption to be incorrect in beef production areas in northern and western Queensland. Aerial and ground baiting with 1080 (fluoroacetate) is the principal dingo-control method used in extensive pastoral areas of Australia. This paper compares four approaches to measure the effectiveness of these control programs. Dingo abundance was reduced in 11 of 13 baiting campaigns monitored with almost two-thirds of these producing >50% reduction. However, concurrent decline in dingo abundance occurred in non-baited areas due to seasonal changes in dingo populations. When this was taken into account, less than half of the control programs produced >50% reduction. The time taken for dingoes to recolonize baited areas is also an important measure of effectiveness. In two-thirds of the control programs, conducted in the first nine months of the year, dingoes recolonized prior to the period of peak calving (November/December) when the biggest threat to calves existed. The timing and the scale of control programs affect the rate of re-colonization. Calf loss was subsequently higher and occurred more frequently in baited areas compared to non-baited areas. Seasonal conditions, the status of prey populations, and the impact of control programs on social organization and prey selection, are key factors affecting calf predation. Control programs should be assessed by measuring impact rather than changes in predator numbers. The assumption that a direct relationship exists between predator numbers and impact is not valid for dingoes in beef production areas in northern Australia.

Information concerning hispid pocket gopher (Orthogeomys hispidus hispidus) damage to sugarcane and the efficacy of sodium monofluroacetate (Compound 1080) treatments for control of this pest were obtained for the State of Veracruz, Mexico. Pocket gophers represent one of the major vertebrate pests based on the severity of economic losses caused to the sugarcane industry in this state. Pocket gophers cause significant damage in over 200,000 ha of sugarcane fields. In this study, a total of 66,560 stalks were examined for damage. Total percentage damaged was 20.67. Economic loss caused by pocket gopher was estimated at approximately $951 in one grower processor’s crop based on the 1998-99 price for raw sugar ($25 dollars/ton). Losses due to this pest species are probably underestimated because many sugarcane industries could not or did not provide loss estimates.

Worldwide, introduced pest species create significant challenges to native biodiversity and individual health. New Zealand has an extensive history of attempting to protect biodiversity from introduced pests such as the Brushtail possum (Trichosurus vulpecula [Diprotodontia: Phalangeridae]). Success has been achieved on a small scale, but the transition to the whole country management poses new issues. Therefore, this review uses the framework of 'Predator Free 2050' to summarize current practices and scrutinize new technologies. Importantly, we include a toxicology focus to the discussion, providing detail on the mechanism(s) of action that inform decisions regarding the pros and cons for the use of various chemical agents. Currently, the New Zealand government supports the use of sodium fluoroacetate (1080) for predator control on a mass scale, but this comes with a social opposition that is not always reflective of the underlying science. Understanding this controversy is vital if new strategies are to be deployed to achieve large-scale pest management. We use New Zealand as a case study in this area because its unique and isolated ecosystem provides a global opportunity for understanding new technologies and best practice. [ABSTRACT FROM AUTHOR]

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Recreational hunters are concerned that aerial 1080 operations in New Zealand's forests may adversely affect deer hunting, but data are rarely gathered in a way that enables such effects to be assessed. Between 2011 and 2015, we recorded two relevant indicators of the recreational hunting experience -- number of red deer (Cervus elaphus) encounters, and number of individual red deer seen -- in 865 person days of quarterly surveys across seven blocks of native forest in South Westland, New Zealand. Four blocks were treated with aerial 1080 before and during the study, and three were untreated. Generalised linear mixed effects models provide no evidence that aerial 1080 treatments reduced numbers of red deer encounters or numbers of individual red deer seen over time. There were no overall trends in numbers of deer encounters and deer seen per person day in either treated or untreated blocks over the study period, and average numbers of deer encounters and deer seen in treated and untreated blocks were similar. Models fitted to data from the 1080-treated forest blocks alone showed that numbers of deer encounters and numbers of deer seen per person day were highest in the period immediately following an aerial 1080 operation and declined over the following 2-3 years. This pattern is likely to result from a change in deer behaviour rather than in deer numbers, and its cause is unknown. [ABSTRACT FROM AUTHOR]

New Zealand currently has large scale possum and rabbit operations being carried out on about 103 of its land area. Education and training are integral to possum control in New Zealand because of the heavy reliance that the control agencies in New Zealand place on toxic baiting with 1080 (sodium monofluoroacetate). Education of the general public is treated as a high priority since without their approval many of the operations would not be carried out. It is equally important that school children are advised on what toxic baits look like and why pest control operations are required. Training of pest control staff is also considered important as it is vital that all staff are well trained in the latest technology and at the same time can answer inquiries with the latest results of research.

To determine the risk of secondary poisoning for animals preying on sub-lethally poisoned brushtail possums, captive possums were treated with near-lethal doses of sodium monofluoroacetate (1080) or brodifacoum, and toxicant concentrations in blood and tissue were monitored over time. Sodium monofluoroacetate was rapidly eliminated from the blood (within three days). Brodifacoum was retained in the liver and, to a lesser extent, the muscle of possums for eight months after dosing. To determine the potential risk for animals scavenging on the carcasses of possums poisoned with cholecalciferol, cats were fed poisoned carcasses for six days. No changes in behavior, appetite, or body weight were observed. Serum calcium concentrations increased slightly, but remained within the normal range for cats.

The Levant vole, Microtus guentheri, is a pest of most of the field crops in Israel. It lives in gallery systems, the openings of which are clearly visible, and is active above ground mainly at night. Its activity was assessed by plugging the burrow openings (holes) and, after three nights, counting the number of reopened holes. The efficacy of control by whole wheat toxic baits was determined by counting the number of reopened holes before and after the treatment in random squares. Three chemicals were tested: sodium fluoroacetate, zinc phosphide and brodifacoum. The bait was applied either by hand, airplane, or centrifugal spreader. The period between treatment and post-treatment count was one week for the two acute rodenticides, and at least two weeks for the anticoagulant baits. Satisfactory results were obtained: 1) by a 2% zinc phosphide bait, with 0.7 g inserted manually into the voles' holes, or distributed at rates between 4.2 to 12.2 kg/ha; 2) by a 0.05% sodium fluoroacetate bait, with 0.2 g being inserted manually into the holes, or distributed at rates of 1.6 to 4.0 kg/ha; and 3) by 0.005 % brodifacoum bait, with 3 g being inserted manually into the burrows, or broadcast at rates of 5.8 and 8.7 kg/ha.

Aerial delivery of 1080 (sodium monofluoroacetate) baits is the main technique for reducing populations of New Zealand's foremost vertebrate pest, the Australian brushtail possum, in large areas of inaccesible country. Surveys after pilot-controlled aerial sowing of baits in seven operations in forests showed that inaccurate navigation along the swaths left up to half the target zone untreated. Kill was estimated to average 75%. Inadequate coverage with baits was therefore believed to be a major factor in the survival of possums during aerial control operations. This was confirmed in field trials using rhodamine B as a biomarker to reveal acceptance of non-toxic baits. More possums were unmarked in partially treated blocks than in completely treated blocks. After a large-scale aerial control operation, proportionally more possums survived in untreated gaps than in treated areas. Six operations that used navigation guidance systems (Decca Flying Flagman and GPS) yielded complete coverage and high levels of kill (mean of 92%) in five. Precision sowing of possum baits prevents survival of possums by failure to encounter baits, and enables lower rates of bait application. This will give large cost savings and improved environmental safety. A small proportion of a population may still not be targeted because of individual dislike of bait or failure to encounter baits because animals stayed in the forest canopy during operations. Development of more palatable and longer lived baits may facilitate local extermination of possums.

Many vertebrate pesticides used by the Bureau of Biological Survey at the turn of the century were registered by the U.S. Fish and Wildlife Service (USFWS) beginning in 1960 with the U.S. Department of Agriculture (USDA). A review of archives and other documents at the Denver Wildlife Research Center (DWRC) has shown that a total of 72 federal registrations were established by the USFWS between 1960 and 1985. Because of increased regulation by the U.S. Environmental Protection Agency (EPA), selective transfers from USFWS to USDA, voluntary cancellations, conversions to state local need registrations, and a reduced development pace, there are now only 21 federal vertebrate pesticide registrations. They are maintained by the Animal and Plant Health Inspection Service (APHIS) for the Animal Damage Control (ADC) program. As a result of a 1988 Amendment to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA 88), DWRC initiated in 1989 an extensive reregistration program for ADC's vertebrate pesticides. In the past three years, DWRC and its cooperators have submitted 188 studies in support of the reregistration of products containing strychnine, sodium cyanide, zinc phosphide, compound 1080, sodium nitrate, carbon, DRC-1339, and PA-14. Since 1989, the reregistration of these 8 active ingredients has taken priority over the development of new vertebrate pesticides at DWRC in order to concentrate on gathering data for these chemicals of the past. New tools to mitigate human and wildlife conflicts must continue to be the goal of present and future federal research.

Possum control in New Zealand is dependent on the use of sodium monofluoroacetate (1080) and cyanide. Although 1080 is highly effective, its use is restricted to government staff. Cyanide is available for a wider group of licensed operators, but cyanide "shyness" reduces its effectiveness. An acute toxicity programme has been set up to identify non-anticoagulant toxins that could be used safely by farmers. Dose-ranging studies showed that possums are susceptible to cholecalciferol, calciferol, gliftor, alpha-chloralose, and nicotine, but not to bromethalin. As lethal doses for these toxins have been ascertained, which of them are likely to be cost-effective and safe alternatives to 1080 now needs to be established. Bait palatability and field studies will then be undertaken with the most promising candidates.

Animals in Australia vary greatly in their sensitivity to 1080 poison, with known LD50's ranging from 0.11 to over 800 mg kg-1. Many native species, particularly in western Australia, have evolved tolerances to 1080 through ingestion of native plants that contain fluoroacetate or prey that consume those plants. Despite this, some native species, particularly a few herbivorous mammals, birds and rodents, could be poisoned during control campaigns against vertebrate pests. Field studies indicate that poisoning campaigns are not significantly affecting populations of common non-target animals, but further impact studies are required on vulnerable, rare, endangered, or uncommon species.

To improve feral cat control we developed a dry pelleted toxic bait and evaluated the potential of lures. A polymer fish meal bait was preferred by cats from a range of bait types tested. L-alanine further increased bait acceptance by cats in pen trials and catnip may have the potential to increase field acceptance and target specificity. An oral LD90 of 0.38 mg/kg was established for sodium monofluoroacetate (1080) in feral cats voluntarily eating surface-loaded baits. Acute toxicity to cats of warfarin, cholecalciferol, and gliftor was tested. However, because the cat proved highly sensitive to 1080, we recommend its use at a dose of 2 mg per cat bait. In preliminary field trials of bait acceptance using non-toxic polymer bait (without flavours or attractants), marked with the plasma marker iophenoxic acid, 50% of 39 cats caught within 3 weeks of laying the baits were marked. Subsequently polymer bait, surface coated with 1080 was used in the successful eradication of feral cats from Matakohe Island (37 ha), Whangarei Harbour, New ZeaJand.

The acute oral LD50 of Compound 1080 to magpies was estimated at 1.78 mg/kg indoors, 1.91 mg/kg outdoors in summer, and 2.30 mg/kg outdoors in winter. Postmortem 1080 residues were detected in 75 of76 treated birds. Higher doses yielded higher 1080 residues. Within dose levels, birds surviving longer carried lower residues. In a separate test, an average residue of 0.09 ppm was found in 8 birds treated at 1.59 mg/kg and euthanized 24 h post dosing. The adjusted dietary LC50 of Compound 1080 to magpies tested indoors was estimated at 16 ppm. During LC50 tests, the influence of 1080 on food consumption and bird weight varied. Birds receiving low doses were unaffected and those receiving high doses died quickly. Birds that were affected but did not die quickly, usually lost weight but only slightly reduced food intake. All birds that died had detectable 1080 residue in breast muscle. Birds fed higher 1080 dietary concentrations probably exhibited higher residues postmortem. Our adjusted average LD50 (2.12 mg/kg) appeared somewhat higher than reported in the literature; nonetheless, magpies are very sensitive to 1080. No sex differences were noted. Age, metabolic influences, or cold temperatures might explain the high LD50 value estimated for winter. The detection of 1080 residue in tissue samples is a useful tool for assessing 1080 exposure in magpies−but it might not be unequivocal.

Vomiting is a characteristic, although undesirable effect when using Compound 1080 (sodium monofluoroacetate) as a method of predator control for coyotes. Compound 1080 meat baits with (treatment) and without (control) an antiemetic, metoclopramide hydrochloride (MH), were fed to captive coyotes to determine whether MH would prevent vomiting. All treatment and control animals died as a result of consuming the 1080 bait with no difference between the groups in time from bait consumption to death. There was no significant difference between the number of treatment and control animals that vomited after consuming the baits. Likewise there was no difference between the treatment and control groups in the time from consuming 1080 to vomiting, the duration of the vomiting period, or the number of times each animal vomited. Despite indications in the literature to the contrary, MH did not prevent 1080-induced vomiting in coyotes.