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The history of discoveries in rodenticide development and control technology as well as current and future-focused research are explored. Traps and older poisons such as red squill, arsenic, and cyanide have been used for hundreds if not thousands of years. Between 1940 and 1980 there was a period of innovation with the discovery of new molecules, including acute toxins and slower acting anticoagulants. The period 1980 to 2018 has been a time for improved utilization of individual tools and research to retain registrations, develop new toxins and delivery systems, and explore non-lethal control options. However, despite these advances, decades old broad-spectrum toxins and traplines are still the mainstay of pest control. Technological leaps are needed to achieve much more precise, affordable, and socially acceptable pest control. The period 2018 to 2050 should be a time for accelerated innovation. There are exciting opportunities for transformational change based on the integration of existing and new tools, such as advances in automated species recognition systems, new self-resetting traps, and species-specific toxin-delivery systems. Over-reliance on 'silver bullet' technologies for small mammal pest control is the wrong approach to biodiversity conservation. This has been demonstrated through two decades of challenging research on viral vectored immunocontraception, and would apply if all pest control research focused on a single toxin, one new engineering-based technology, or on gene editing, which has potential, but will not be a panacea for all mammal pests. Balance is important, with research supporting the skill of pest control practitioners and supporting emerging technologies, as well as novel biocontrol or genetic research. There has been no focused research aimed at integrating a broad suite of new tools, and incorporating disruptive technologies from completely different fields. We believe that science and technology have now advanced such that automated, online, and real-time systems for monitoring and managing pests are achievable in the next decade.

Internationally, over the last 20 years the number of tools available for the control of small mammals has declined. Through the efforts of research we have bucked this trend and retained and developed new tools. Three new toxins have been extensively researched and registered, namely para-aminopropiophenone (PAPP) in 2011 for stoats and feral cats; zinc phosphide for possums in 2012; and encapsulated sodium nitrite (ESN) in 2013, for possums and feral pigs. The development of PAPP and ESN, coined red blood cell toxins, developed for humaneness, represent the first new vertebrate pesticides registered for field control of mammalian pests anywhere in the world for >30 years. Research on rodenticides including diphacinone with the additive cholecalciferol (D+C) and a palatable form of norbormide continues. A New Zealand EPA application for D+C was filed in June 2015. More effective killing systems are being researched, and the first successful field trials of resetting toxin delivery devices for possum and stoat control were completed in 2013 and 2014. Improved deployment strategies, integration of humane and selective toxins, lures of greater potency, and improved killing devices aided by species’ recognition will transform ground control for endangered species protection. Sodium fluoroacetate (1080) and other important tools have been retained as new tools are emerging from a research and development pipeline. It is important for the future of New Zealand’s biodiversity that this focused research continues and we continue to learn and advance new technologies. Our goals are shifting to enable reduction in density of rat, stoat, and possum populations to zero over large scales (i.e., elimination at landscape scale), and to hold these at zero through detection and response, including the use of new technologies for perimeter control as part of barrier systems for conservation.

Feral cat and stoat control is conducted in New Zealand to protect a number of threatened native species, including kiwi, from predation. Para-aminopropiophenone (PAPP) is being developed for predator control. Previously reported cage trials have shown PAPP presented in a meat bait was palatable and effective, while symptoms observed demonstrated PAPP to be humane. Subsequent field trials on stoats were undertaken in two blocks of native forest and achieved 83% and 87% reductions in the stoat abundance index, and a field trial on a population of radio-collared feral cats had an 84% kill. PAPP represents one compound from a new class of active ingredients, which we are calling red blood cell toxins. These vertebrate pesticides have humaneness, and low secondary and non-target poisoning risks, as their primary consideration. The dose is optimised to be effective in the field and reduces oxygen supply to the brain such that animals become lethargic, sleepy and unconscious prior to death within 1-2 hours. Results from these field trials on stoats and feral cats indicate that PAPP will be a useful additional tool for predator control.

In New Zealand, sodium fluoroacetate (1080) has been used for vertebrate pest control for several decades. Since the 1990s, some 1080 users have switched to brodifacoum for possum and rodent control because of its ready availability and ease of use. An awareness that field use of brodifacoum results in persistent residues provides the impetus to develop alternatives and provide new tools and greater flexibility. Looking to the future, we seek toxins which increasingly combine “low-residue” characteristics with humaneness, and more selective bait and delivery systems enabling better and more acceptable control of possums, wallabies, mustelids, rodents, feral cats, and rabbits. Experience gained in the 1990s with the introduction of cholecalciferol (Feracol®) and a cyanide pellet (Feratox®), which both kill possums without secondary poisoning, underpins the extension in 2009 of the Feratox® registration to include introduced Dama wallabies. To date, zinc phosphide has not been registered in NZ, despite its field use in Australia and the U.S. and low secondary poisoning risk compared with 1080. Research and registration dossiers are being assessed in 2009-10 for zinc phosphide containing products for possum and rodent control. Registration documents are also being prepared for a combination of cholecalciferol and coumatetralyl to provide a slow-acting alternative to brodifacoum for the field control of possums, rodents, and rabbits with low risk of bio-accumulation. Anticipated timelines for product availability are 2010 (zinc phosphide) and 2011-13 (cholecalciferol and coumatetralyl). Our intention now is to move beyond these conventional rodenticides and develop new vertebrate pesticides. For example, we are pursuing the registration of para-aminopropiophenone (PAPP) for humane control of stoats and feral cats, and a series of related novel toxins and other compounds that target the red blood cell for other pest species including rodents. PAPP products should be available in 2010, subject to registration approvals. New research initiatives in 2010 will increasingly result in a shift in focus to the development of novel rodenticides aided by new international research collaborations.

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.

The brushtail possum, introduced to New Zealand in 1858, is a significant conservation pest and a major vector of bovine tuberculosis. Previous control-simulation studies have suggested that aerial delivery of bait containing sodium fluoroacetate (1080) is the most cost effective (large scale) possum control strategy. Over the past decade, considerable improvements in groundcontrol techniques have been developed by private contractors and bait manufacturers. These techniques are not reliant on 1080, and there have been major cost reductions as the new baits and delivery mechanisms have been optimized. In addition to this, our research team (in collaboration with Connovation Research Ltd.) have recently developed a new bait station design that has the potential to be left out in the field for up to 5 years without the need for servicing. These devices are self setting and have the ability to deliver gel or liquid spray, and ‘target-specific’ toxicants. Preliminary cost analysis suggests that this new bait station design has the potential to save NZ$21 million per annum from the amount currently spent on possum ground control.

The use of infrared-flash camera traps has increased dramatically over the past ten years particularly for capturerecapture population studies of distinctly-marked species. However, to use capture-recapture with the more inconspicuous species, high-quality colour imaging (and therefore white flash) is required. A potential problem with white flash is that it may negatively affect behaviour, in this case at bait stations, therefore causing results that do not truly represent possum activity. Possums were used in this study to compare two different types of camera trap: infrared and white flash. Camera traps were placed to take images of possums visiting bait stations, and the number of possum visits was used to determine if white-flash cameras gave different results to infrared-flash cameras. The white-flash cameras had slightly higher possum visits than infrared-flash cameras but the difference was not significant (P=0.437). Over time, the number of possum events (P=0.62) and the amount of time possums spent at the stations did not differ significantly (P=0.81). There was also no difference in the amount of bait taken by possums at white flash compared to infrared stations (P=0.61). Results show possums are not likely to be affected by white-flash cameras compared to infrared-flash cameras. This study therefore showed that there is unlikely to be any behavioural disadvantage in using white flash over infrared, allowing white-flash cameras to be investigated for their potential in identifying individual possums, and as a monitoring tool in control operations.

Considerable effort has been put into retaining older vertebrate pesticides and improving the effectiveness and safety of pest control. Nevertheless, conventional control targeting single species is sometimes still associated with non-target impacts, bioaccumulation of toxins, fluctuating pest numbers, and unexpected ecological consequences. To counter this, we are developing multi-species bait types for sustained field use that are more palatable to vertebrate pest species. We are incorporating “low-residue” toxicants, namely zinc phosphide, cholecalciferol, diphacinone, and a combination of coumatetralyl and cholecalciferol, in new bait formulations. Looking to the future, we seek to increasingly combine “low-residue” characteristics with humaneness. New humane formulations of cyanide are being developed for a variety of pest species, and para-aminopropiophenone is being introduced for predator control in New Zealand as part of the product development and registration pipeline.

The kereru (New Zealand pigeon) is a threatened endemic species. Predation of eggs, chicks, and adults at nests by mammalian predators is considered to be a major potential threat. The impact of mammalian predators on kereru populations was studied on three remnant native bush areas on Banks Peninsula, New Zealand, from February 2004 to March 2005. In this study, 15 kereru were fitted with radio-transmitters and intensely monitored for survival. Three radio-tagged kereru were lost at the beginning of this study and their transmitters were redeployed, so a total of 18 radio-tagged kereru were monitored for predator-induced mortality. Five adult kereru died, 3 as a result of predation. A cat was recorded on video preying on one adult. It is hypothesised that cats were responsible for preying on other kereru during this study. Rat and possum predation limited nesting success; however, this could have been offset by replacement nesting after nest failures. Cats preyed on chicks and adult kereru, which impacted the breeding viability of the adult population. Kereru may be able to withstand some nest predation pressure if the pair is able to re-nest in the same season. However, the ability of kereru to re-nest is reliant on them having an adequate food source, so this may not be possible in poor seasons. These assertions require population modelling to determine their relative importance. Nesting success would benefit from rat and possum control during good breeding seasons. Adult survival would benefit from the control of predators such as cats and stoats. However, as kereru have integrated into urban habitat, managers must consult with the community before conducting predator control.

The successful management of vertebrate wildlife populations can be dependent on the availability of reliable monitoring methods, and, depending on the status of the species in question, effective methods of conservation or control. The brushtail possum, introduced to New Zealand from Australia, is considered New Zealand’s number one vertebrate pest. We assessed possum preferences for 3 types of visual lures and the potential use of this information for enhancing existing possum control technologies. Significantly more lures were interfered with by possums when the lures were associated with a luminescent strip, compared to lures that were plain white or UV-enhanced (P < 0.01 in both cases). In addition, more possums were killed when luminescent lures were attached to kill traps and bags of bait than when these devices were deployed without lures. This study has highlighted new information showing that luminescent lures could be a valuable new tool in the management of nocturnal marsupials, be they species considered pests (such as the brushtail possum in New Zealand), or species of conservation concern, such as many of Australia’s marsupial species.

Although Talon® baits containing brodifacoum have been used successfully in eradicating rats from some of New Zealand's offshore islands, little is known about any environmental effects of this toxin. Invertebrates, blackbirds, soil, and water at intervals of two days to nine months were sampled to determine whether brodifacoum residues were present after aerial distribution of Talon 20P cereal pellets on Red Mercury Island and after bait-station use of Talon 50WB wax-coated cereal blocks on Coppermine Island. No brodifacoum residues were found in soil, water, or most (99%) invertebrate samples. Low concentrations (0.12 µg/g) were found in one sample of slugs collected two days after aerial sowing. Liver tissues from all birds (n=4) and rats (n=3) found dead, and from all six birds collected alive eight months after aerial baiting, also contained low-to-moderate concentrations of brodifacoum (0.004 to 11.0 µg/g). These preliminary results suggest that invertebrates are not likely to accumulate brodifacoum as a result of Talon baiting. Laboratory studies showed that, although some invertebrates may eat Talon baits, it appears that the brodifacoum is metabolized and/or excreted within a few days. The dead blackbirds found were, therefore, more likely to have been killed by primary rather than by secondary poisoning. Further monitoring for brodifacoum residues after Talon operations should be undertaken to confirm that contamination of invertebrates, soil, and water is unlikely. Some bird species may be at risk from eating Talon baits. Likely effects on population levels of such species should be assessed to help weigh the risk and benefits of Talon use in rodent eradication.

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]

New Zealand has many introduced mammalian species that are managed as pests of conservation and/or economic importance, including four rodent species. Vertebrate pesticides are the most important rodent management tool, largely dominated by anticoagulants such as brodifacoum, and by the metabolic disruptor, Compound 1080. There has been considerable opposition to these pesticides, primarily based on concerns about environmental persistence and non-target effects; Maori have been particularly vocal in opposition. Maori have place-based knowledge about naturally-occurring plant toxins that could be used as culturally-acceptable alternatives to existing rodenticides. In the context of the research presented here, the term 'culturally-acceptable' refers to new pest control options that have been co-designed with Matauranga Maori experts that inherently include Maori ways of thinking, being, and acting. Tuhoe researchers in our study wanted to pursue the most promising natural toxic compound found in native plants as a suitable alternative to current vertebrate pesticides. Therefore, we undertook an oral gavage trial to assess the toxicity of tutin, the toxin active in tutu (Coriaria arborea), to the Norway rat, (Rattus norvegicus). Tutin was toxic to this species at a dose of 55 mg kg-1, with a quick, humane death compared to other existing rodenticides. At a dose rate of 55 mg kg-1, all animals of both sexes died within an hour, and once neurological poisoning symptoms commenced these animals were unconscious within 5-10 minutes. We conclude it is warranted to take the next logical research step, which is to prove whether this dose rate would be technically attainable in the field. Although for now New Zealand remains reliant on 1080 and anti-coagulants for mammalian pest control, efforts should continue to develop more targeted toxins and delivery systems. We recommend incorporating Matauranga Maori to identify alternative control tools that could lead to more culturally acceptable pest control. [ABSTRACT FROM AUTHOR]

BACKGROUND Invasive mammalian pests have inflicted substantial environmental and economic damage on a worldwide scale. RESULTS Over the last 30 years there has been minimal innovation in the development of new control tools. The development of new vertebrate pesticides, for example, has been largely restricted due to the costly and time-consuming processes associated with testing and registration. CONCLUSION In this article we discuss recent progress and trends in a number of areas of research aimed to achieve long-term population suppression or eradication of mammalian pest species. The examples discussed here are emerging from research being conducted in New Zealand, where invasive mammalian pests are one of the greatest threats facing the national environment and economy. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]