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The recent paper published by Cook and Mulgan [...].

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Population control of invasive mammal pests is an ongoing process in many conservation projects. In New Zealand, introduced wild domestic cats and mustelids have a severe impact on biodiversity, and methods to reduce and maintain predator populations to low levels have been developed involving poisoning and trapping. Such conservation efforts often run on limited funds, so ways to minimize costs while not compromising their effectiveness are constantly being sought. Here we report on a case example in a 150 km2 area in the North Island, New Zealand, where high predator numbers were reduced by 70-80% in an initial 'knockdown' trapping program, using the full set of traps available in the fixed network and frequent checks, and then maintained at low density using maintenance trapping with less frequent checking. We developed and applied a simulation model of predator captures, based on trapping data, to investigate the effect on control efficacy of varying numbers of trap sites and numbers of traps per site. Included in the simulations were captures of other, non-target, introduced mammals. Simulations indicated that there are potentially significant savings to be made, at least in the maintenance phase of a long-term predator control programme, by first reducing the number of traps in large-scale networks without dramatically reducing efficacy, and then, possibly, re-locating traps according to spatial heterogeneity in observed captures of the target species.

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Animal welfare is increasingly important in the understanding of how human activity affects wildlife, but the conservation community is still grappling with meaningful terminology when communicating this aspect of their work. One example is the use of the terms "humane" and "inhumane." These terms are used in scientific contexts, but they also have legal and social definitions. Without reference to a defined technical standard, describing an action or outcome as humane (or inhumane) constrains science communication because the terms have variable definitions; establish a binary (something is either humane or inhumane); and imply underlying values reflecting a moral prescription. Invoking the term "humane," and especially the strong antithesis "inhumane," can infer a normative judgment of how animals ought to be treated (humane) or ought not to be treated (inhumane). The consequences of applying this terminology are not just academic. Publicizing certain practices as humane can create blurred lines around contentious animal welfare questions and, perhaps intentionally, defer scrutiny of actual welfare outcomes. Labeling other practices as inhumane can be used cynically to erode their public support. We suggest that, if this normative language is used in science, it should always be accompanied by a clear, contextual definition of what is meant by humane.

Reconsideración de la Condición Humana Resumen El bienestar animal es cada vez más importante para el entendimiento de cómo la actividad humana afecta a la fauna, pero la comunidad conservacionista todavía lucha con la terminología significativa cuando comunica este aspecto de su trabajo. Un ejemplo es el uso de los términos humano e inhumano. Estos términos se usan dentro de contextos científicos, pero también cuentan con definiciones sociales y legales. Sin la referencia a un estándar técnico definido, la descripción de una acción o resultado como humano (o inhumano) restringe la comunicación de la ciencia pues estos términos tienen definiciones variables; establecen una opción binaria (algo sólo es humano o sólo es inhumano); e implican valores subyacentes que reflejan una prescripción moral. La invocación del término humano, y especialmente su fuerte antítesis inhumano, puede inferir un juicio normativo sobre cómo los animales deberían ser tratados (humano) o no deberían ser tratados (inhumano). Las consecuencias de aplicar esta terminología no son sólo académicas. La divulgación de ciertas prácticas como humanas puede generar confusión entorno a preguntas polémicas sobre el bienestar animal y, tal vez de manera intencional, aplazar el escrutinio de los resultados actuales para el bienestar. Al contrario, la denominación de otras prácticas como inhumanas puede usarse cínicamente para menoscabar el apoyo público que reciben. Sugerimos que, si se utiliza este lenguaje normativo en la ciencia, siempre debería estar acompañado de una definición clara y contextual de a lo que se refiere con el término humano.

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All capture methods impose animal welfare impacts, but these impacts are rarely quantified or reported. We present data from two wildlife capture studies that trialled new methods for capturing Bennett's wallabies (Notamacropus rufogriseus) and red deer (Cervus elaphus) in New Zealand. We used helicopter net-gunning for both species, and compared this method with ground-based netting for wallabies and helicopter darting for red deer, using, for the first time in New Zealand, the fast-acting opioid thiafentanil. Efficacy and animal welfare parameters quantified were duration of handling and recovery, and frequency of adverse events, including escape, injury, and mortality. Cost-effectiveness was quantified for each method. Capture mortalities occurred for all methods for both species. For red deer, chemical immobilisation led to fewer traumatic injuries and fewer mortalities, while for wallabies, net-gunning led to fewer mortalities. Net-gunning was an efficient capture method for deer in open habitat, but led to the escape of 54% of wallabies and one wallaby mortality (4%). Ground-based netting resulted in the mortality of 17% of wallabies at the time of capture, and the capture of non-target species. The cost per captured wallaby was 40% more expensive for net-gunning (NZ$1045) than for ground-based netting (NZ$745), but, once corrected for mortalities at the time of capture and suitability of individuals for GPS-collar deployment, this was reduced to 29% and 12% more expensive, respectively. Net-gunning for red deer resulted in the escape of 13% of animals and mortality of 10% of animals at the time of capture. Helicopter-based darting for red deer using thiafentanil (c. 0.03-0.06 mg/kg) had high capture efficacy (zero escapes), rapid induction times (mean of 3 min), and a low mortality rate at 14 days post-capture (3%), but it was more expensive per deer captured and collared than aerial netting (NZ$2677 and NZ$2234, respectively). We recommend reporting of adverse event data for all wildlife capture techniques to permit continual refinement of field methods.

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Anticoagulant rodenticides are used to manage rodents in domestic, municipal, agricultural, and conservation settings. In mammals and birds, anticoagulant poisoning causes extensive hemorrhagic disruption, with the primary cause of death being severe internal bleeding occurring over days. The combined severity and duration of these effects represent poor welfare outcomes for poisoned animals. Noting a lack of formal estimates of numbers of rodents and nontarget animals killed by anticoagulant poisoning, the ready availability and worldwide use of anticoagulants suggest that very large numbers of animals are affected globally. Scrutiny of this rodent control method from scientific, public, and regulatory perspectives is being driven largely by mounting evidence of environmental transfer of residual anticoagulants resulting in harmful exposure in wild or domestic animals, but there is also nascent concern for the welfare of targeted rodents. Rodent control incurs a cumulative ledger of animal welfare costs over time as target populations reduced by poisoning eventually recover to an extent requiring another reduction. This 'rolling toll' presents a critical contrast to the animal welfare accountancy ledger for eradication scenarios, where rodent populations can be completely removed by methods including anticoagulant use and then kept from coming back (e.g., on islands). Successful eradications remove any future need to control rodents and to incur the associated animal welfare costs.

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Ethical treatment of wildlife and consideration of animal welfare have become important themes in conservation, but ethical perspectives on how best to protect wild animals and promote their welfare are diverse. There are advantages to the consequentialist harms ethical framework applied in managing wild herbivores for conservation purposes. To minimize harms while achieving conservation goals, we argue that overabundant wild herbivores should in many cases be managed through consumptive in situ killing. Advantages of this policy are that the negative welfare states imposed on animals last only a short time; remaining animals are not deprived of positive welfare states (e.g., linked to rearing offspring); poor welfare states of animals in overabundant populations are avoided (e.g., starvation); negative welfare impacts on heterospecifics through resource depletion (i.e., competition) are prevented; harvesting meat reduces the number of (agricultural) animals raised to supply meat; and minimal costs maximize funding for other wildlife management and conservation priorities. Alternative ethical approaches to our consequentialist framework include deontology (containing animal rights) and virtue ethics, some of which underpin compassionate conservation. These alternative ethical approaches emphasize the importance of avoiding intentional killing of animals but, if no population reduction occurs, are likely to impose considerable unintentional harms on overabundant wildlife and indirectly harm heterospecifics through ineffective population reduction. If nonlethal control is used, it is likely that overabundant animals would be deprived of positive welfare states and economic costs would be prohibitive. We encourage conservation stakeholders to consider animal-welfare consequentialism as an ethical approach to minimize harms to the animals under their care as well as other animals that policies may affect while at the same time pursuing conservation goals.

Conservación Compasiva versus Conservación Consecuencialista Resumen El trato ético de la fauna y la consideración por el bienestar animal se han convertido en temas importantes para la conservación, pero las perspectivas éticas sobre cuáles son las mejores maneras para proteger a los animales silvestres y promover su bienestar son diversas. Existen ventajas en el marco de trabajo ético de los daños consecuencialistas aplicados en el manejo de herbívoros silvestres por motivos de conservación. Para minimizar los daños a la vez que se alcanzan los objetivos de conservación argumentamos que los herbívoros silvestres sobreabundantes deberían, en muchos casos, ser manejados por medio de muertes in situ consuntivas. Las ventajas de esta política son que los estados negativos de bienestar impuestos sobre los animales duran muy poco tiempo; a los animales que permanecen no se les priva de un estado positivo de bienestar (p. ej.: conectados a la crianza de descendencia); se evitan los estados pobres de bienestar en las poblaciones sobreabundantes (p. ej.: hambruna); se previenen los impactos negativos de bienestar por medio de la disminución sobre los heteroespecíficos (es decir, competencia); la crianza para carne reduce el número de animales (agrícolas) criados para abastecer de carne; y los costos mínimos maximizan el financiamiento para otras prioridades de manejo y conservación de fauna. Las estrategias éticas alternativas a nuestro marco de trabajo consecuencialista incluyen la deontología (que contiene los derechos de los animales) y la ética de virtudes, algunas de las cuales apoyan la conservación compasiva. Estas estrategias éticas alternativas enfatizan la importancia de evitar la muerte intencional de los animales pero, si no ocurre una reducción de la población, es probable que impongan daños considerables accidentales sobre la fauna sobreabundante y dañen indirectamente a los heteroespecíficos por medio de la reducción infructuosa de la población. Si se utiliza un control no letal, es probable que los animales sobreabundantes quedarían privados de estados positivos de bienestar y los costos económicos serían prohibitivos. Alentamos a los accionistas de la conservación a considerar el consecuencialismo del bienestar animal como una estrategia ética para minimizar los daños que sufren los animales bajo su cuidado así como otros animales que podrían ser afectados por las políticas mientras se busca alcanzar objetivos de conservación.

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Decision support systems are now mostly computer and internet-based information systems designed to support land managers with complex decision-making. However, there is concern that many environmental and agricultural decision support systems remain underutilized and ineffective. Recent efforts to improve decision support systems use have focused on enhancing stakeholder participation in their development, but a mismatch between stakeholders' expectations and the reality of decision support systems outputs continues to limit uptake. Additional challenges remain in problem-framing and evaluation. We propose using an outcomes-based approach called theory of change in conjunction with decision support systems development to support both wider problem-framing and outcomes-based monitoring and evaluation. The theory of change helps framing by placing the decision support systems within a wider context. It highlights how decision support systems use can "contribute" to long-term outcomes, and helps align decision support systems outputs with these larger goals. We illustrate the benefits of linking decision support systems development and application with a theory of change approach using an example of pest rabbit management in Australia. We develop a theory of change that outlines the activities required to achieve the outcomes desired from an effective rabbit management program, and two decision support systems that contribute to specific aspects of decision making in this wider problem context. Using a theory of change in this way should increase acceptance of the role of decision support systems by end-users, clarify their limitations and, importantly, increase effectiveness of rabbit management. The use of a theory of change should benefit those seeking to improve decision support systems design, use and, evaluation.

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European rabbits (Oryctolagus cuniculus) pose a major threat to agricultural production and conservation values in several countries. In New Zealand, population control via poisoning is a frontline method for limiting rabbit damage, with large areas commonly treated using the metabolic toxin sodium fluoroacetate ('1080') delivered in bait via aerial dispersal. However, this method is expensive and the high application rates of the active ingredient cause public antipathy towards it. To guide reductions in cost and toxin usage, we evaluated the economics and efficacy of rabbit control using an experimental approach of sowing 1080-bait in strips instead of the commonly-used broadcast sowing method (i.e. complete coverage). Over a 4-year period we studied aerial delivery of 0.02% 1080 on diced carrot bait over ~3500 ha of rabbit-prone land in the North and South islands. In each case, experimental sowing via strip patterns using 10-15 kg of bait per hectare was compared with the current best practice of aerial broadcast sowing at 30-35 kg/ha. Operational kill rates exceeded 87% in all but one case and averaged 93-94% across a total of 19 treatment replicates under comparable conditions; there was no statistical difference in overall efficacy observed between the two sowing methods. We project that strip-sowing could reduce by two thirds the amount of active 1080 applied per hectare in aerial control operations against rabbits, both reducing the non-target poisoning risk and promoting cost savings to farming operations. These results indicate that, similarly to the recently-highlighted benefits of adopting strip-sowing for poison control of introduced brushtail possums (Trichosurus vulpecula) in New Zealand, aerial strip-sowing of toxic bait could also be considered a best practice method for rabbit control in pest control policy.

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Introduced brushtail possums (Trichosurus vulpecula) and rat species (Rattus spp.) are major vertebrate pests in New Zealand, with impacts on conservation and agriculture being managed largely through poisoning operations. Aerial distribution of baits containing sodium fluoroacetate (1080) has been refined to maximise cost effectiveness and minimise environmental impact, but this method is strongly opposed by some as it is perceived as being indiscriminate. Although ground based control enables precise placement of baits, operations are often more than twice as costly as aerial control, mainly due to the high labour costs. We investigated a new approach to ground based control that combined aerial distribution of non-toxic 'prefeed' baits followed by sparse distribution of toxic baits at regular intervals along the GPS tracked prefeeding flight paths. This approach was tested in two field trials in which both 1080 baits and cholecalciferol baits were used in separate areas. Effectiveness of the approach, assessed primarily using 'chewcards', was compared with that of scheduled aerial 1080 operations that were conducted in outlying areas of both trials. Contractors carrying out ground based control were able to follow the GPS tracks of aerial prefeeding flight lines very accurately, and with 1080 baits achieved very high levels of kill of possums and rats similar to those achieved by aerial 1080 baiting. Cholecalciferol was less effective in the first trial, but by doubling the amount of cholecalciferol bait used in the second trial, few possums or rats survived. By measuring the time taken to complete ground baiting from GPS tracks, we predicted that the method (using 1080 baits) would be similarly cost effective to aerial 1080 operations for controlling possums and rats, and considerably less expensive than typical current costs of ground based control. The main limitations to the use of the method will be access to, and size of, the operational site, along with topography and vegetation density.

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Internationally, invasive vertebrate species pose a significant threat to biodiversity, agricultural production and human health. To manage these species a wide range of tools, including traps, are used. In New Zealand, brushtail possums (Trichosurus vulpecula), stoats (Mustela ermine), and ship rats (Rattus rattus) are invasive and there is an ongoing demand for cost-effective non-toxic methods for controlling these pests. Recently, traps with multiple-capture capability have been developed which, because they do not require regular operator-checking, are purported to be more cost-effective than traditional single-capture traps. However, when pest populations are being maintained at low densities (as is typical of orchestrated pest management programmes) it remains uncertain if it is more cost-effective to use fewer multiple-capture traps or more single-capture traps. To address this uncertainty, we used an individual-based spatially explicit modelling approach to determine the likely maximum animal-captures per trap, given stated pest densities and defined times traps are left between checks. In the simulation, single- or multiple-capture traps were spaced according to best practice pest-control guidelines. For possums with maintenance densities set at the lowest level (i.e. 0.5/ha), 98% of all simulated possums were captured with only a single capacity trap set at each site. When possum density was increased to moderate levels of 3/ha, having a capacity of three captures per trap caught 97% of all simulated possums. Results were similar for stoats, although only two potential captures per site were sufficient to capture 99% of simulated stoats. For rats, which were simulated at their typically higher densities, even a six-capture capacity per trap site only resulted in 80% kill. Depending on target species, prevailing density and extent of immigration, the most cost-effective strategy for pest control in New Zealand might be to deploy several single-capture traps rather than investing in fewer, but more expense, multiple-capture traps.

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Compensating for biodiversity losses in 1 location by conserving or restoring biodiversity elsewhere (i.e., biodiversity offsetting) is being used increasingly to compensate for biodiversity losses resulting from development. We considered whether a form of biodiversity offsetting, enhancement offsetting (i.e., enhancing the quality of degraded natural habitats through intensive ecological management), can realistically secure additional funding to control biological invaders at a scale and duration that results in enhanced biodiversity outcomes. We suggest that biodiversity offsetting has the potential to enhance biodiversity values through funding of invasive species control, but it needs to meet 7 key conditions: be technically possible to reduce invasive species to levels that enhance native biodiversity; be affordable; be sufficiently large to compensate for the impact; be adaptable to accommodate new strategic and tactical developments while not compromising biodiversity outcomes; acknowledge uncertainties associated with managing pests; be based on an explicit risk assessment that identifies the cost of not achieving target outcomes; and include financial mechanisms to provide for in-perpetuity funding. The challenge then for conservation practitioners, advocates, and policy makers is to develop frameworks that allow for durable and effective partnerships with developers to realize the full potential of enhancement offsets, which will require a shift away from traditional preservation-focused approaches to biodiversity management.

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Stoats (Mustela erminea) and ship rats (Rattus rattus) in New Zealand are targeted by trapping to mitigate their predation on native wildlife. Internationally recognized guidelines for assessing the effectiveness and welfare performance of kill traps are supported by New Zealand legislation under the Animal Welfare Act 1999. The Victor® Easy Set® rat trap was tested and passed a similar standard for killing short-tailed weasels in Canada but failed for stoats when tested in New Zealand in 2002 (short-tailed weasels and stoats are the same species). We tested a modified version of the trap in 2011-12, modified by changing the treadle trigger to a pull trigger and adding a plastic shroud to direct and align approach by animals to the front of the trap. These traps, in vertical and horizontal sets, were tested with both stoats and ship rats. During each test the trap had to render 10 of 10 animals irreversibly unconscious within 3 minutes to meet approval requirements. The modified trap passed with both species in both trap sets. All stoats were struck across the cranium whereas rats were struck either on the cranium or neck. We recommend this trap design for use by community conservation groups for targeting stoats and ship rats in New Zealand.

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Practical techniques are required to monitor invasive animals, which are often cryptic and occur at low density. Camera traps have potential for this purpose, but may have problems detecting and identifying small species. A further challenge is how to standardise the size of each camera's field of view so capture rates are comparable between different places and times. We investigated the optimal specifications for a low-cost camera trap for small mammals. The factors tested were 1) trigger speed, 2) passive infrared vs. microwave sensor, 3) white vs. infrared flash, and 4) still photographs vs. video. We also tested a new approach to standardise each camera's field of view. We compared the success rates of four camera trap designs in detecting and taking recognisable photographs of captive stoats (Mustelaerminea), feral cats (Felis catus) and hedgehogs (Erinaceuseuropaeus). Trigger speeds of 0.2-2.1 s captured photographs of all three target species unless the animal was running at high speed. The camera with a microwave sensor was prone to false triggers, and often failed to trigger when an animal moved in front of it. A white flash produced photographs that were more readily identified to species than those obtained under infrared light. However, a white flash may be more likely to frighten target animals, potentially affecting detection probabilities. Video footage achieved similar success rates to still cameras but required more processing time and computer memory. Placing two camera traps side by side achieved a higher success rate than using a single camera. Camera traps show considerable promise for monitoring invasive mammal control operations. Further research should address how best to standardise the size of each camera's field of view, maximise the probability that an animal encountering a camera trap will be detected, and eliminate visible or audible cues emitted by camera traps.

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BACKGROUND: The metabolic toxin sodium fluoroacetate ('compound 1080') is widely used for controlling introduced mammalian pests in New Zealand. For large-scale operations, 1080 is distributed aerially in bait to kill brushtail possums (Trichosurus vulpecula Kerr) and ship rats (Rattus rattus L.). While usually successful in reducing pest populations by > 80%, widespread distribution of toxic bait is relatively expensive and raises concerns from some members of the public. Here, trials with spatial aggregation of baits in forested habitats were conducted to determine whether this can reduce toxin usage while maintaining operational efficacy. RESULTS: When 1080 baits were aggregated into clusters (by hand sowing) or into strips (by precision aerial deployment), indices of possum relative abundance were reduced by 92-100%, compared with 73-100% reductions using conventional aerial broadcasting, while all methods reduced relative abundance indices of rats by 88% or greater. Radio tracking indicated a kill rate of > 90% against possums, regardless of bait distribution method. CONCLUSIONS: Simply by modifying bait distribution patterns, spatial aggregation can be used to maintain the high encounter rate of pests with 1080 bait that is necessary for operational efficacy, while reducing current toxin usage by up to 80%. Aggregated bait delivery could have relevance for other mammalian pest control scenarios internationally.

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New Zealand has a range of carnivorous and herbivorous mammals that were originally introduced for recreational, financial, aesthetic and biocontrol reasons, but which now pose significant threats to conservation and animal health values. Research is undertaken to develop new tools and strategies to manage these pests. Captive trials that are carried out include those to determine the toxicity of poisons, the efficacy of fertility control agents, and welfare impacts of poisons and traps. Field trials are undertaken to test the efficacy of poisons and traps, and large-scale management trials carried out to optimise control strategies. Although this research is aimed at managing animals, including killing them, we believe that there are benefits to both individual animals and animal populations that far exceed any cost of harm to individuals that are managed (often killed). We suggest that there are three levels of beneficiaries: the individuals of the pest species that are killed, the individuals in the surviving population, and the individuals and populations of other species. We provide examples of how wild animals can benefit from vertebrate pesticide and trap research.

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