Stoats and feral cats are key predators of some of New Zealand's most threatened fauna and landscapescale control tools are urgently needed.A ready-made meat bait is being developed for use in both aerial and ground-based control operations.As part of the development, two trials with non-toxic versions of the bait were undertaken: one targeting stoats in Fiordland in spring 2020 and the other targeting feral cats in the Mackenzie Basin in winter 2021.The trials aimed to assess the palatability of baits to both target and non-target species.Stoats and feral cats ate both rabbit and chicken sausage baits.The only native species found to eat baits during the stoat trial was the South Island robin.No consumption of baits by native species was observed during the feral cat trial.These trials have provided confidence that stoats and feral cats can find baits that are hand-laid at a relatively low density.Adding a toxin which has an odour and taste may affect palatability, so field trials will be required to test toxic versions of the baits.

A resetting toxin device (the "Spitfire") has been designed that delivers a toxic paste to a rat's ventral surface when it passes through a tunnel.The rat grooms off the paste and ingests the toxin.The system was assessed in cage trials and one field trial.The purpose of the cage trials was to investigate whether a range of toxins can be delivered by the Spitfire to rats (Rattus rattus and R. norvegicus), namely 0.55% sodium fluoroacetate (1080), 0.2% brodifacoum, 15% cholecalciferol, and 12.5% zinc phosphide.The trials with 1080, brodifacoum, and zinc phosphide were successful with > 85% of rats ingesting lethal doses.The trials with cholecalciferol were less successful with only 58% of rats dying.A one-month pilot field trial was undertaken using 1080 in the Spitfires.There was a knockdown in rat (and stoat Mustela erminea) abundance, establishing proof of concept for the Spitfire delivery system with this toxin.The long-term, effective control of introduced rats will require a range of toxins with different modes of action.The Spitfire could be a useful additional control tool for rats and is currently being re-engineered to be made more reliable.

Eradication and control methods to limit damage caused to native biota in New Zealand by the stoat (Mustela erminea) rely on effective lures for trapping and detection devices, such as cameras. Long-life semiochemical lures have the potential for targeting stoats in situations where food-based lures are of limited success. The attractiveness of body odours of captive stoats was tested in a series of captive animal and extensive field trials to investigate their potential as trapping and monitoring lures. Stoats approached and spent significantly more time sniffing stoat urine and scats and bedding from oestrous female stoats than a non-treatment control. The bedding odours were attractive in both the breeding and the non-breeding season. Stoats also spent significantly more time sniffing oestrous stoat bedding than female ferret bedding, but the ferret odour also produced a significant response by stoats. In the field trials, there were no significant differences between the number of stoats caught with food lures (long-life rabbit or hen eggs) compared with oestrous female or male stoat bedding lures. These results indicate the potential of both stoat bedding odour and the scent of another mustelid species as stoat trapping lures that likely act as a general odour attractant rather than a specific chemical signal of oestrus.

The house mouse (Mus musculus) is considered the most difficult rodent species to eradicate from islands.Eradication projects require careful planning and execution of an 'over-engineering' approach to ensure every individual of the targeted population is encountered and removed.Aerial broadcasting of rodenticides has been the method of choice for island rodent eradications since the 1990s and the methods and parameters continue to be refined.Mice were recently eradicated from Te Pākeka/Maud Island (318 ha) in winter 2019 using an aerial baiting prescription that was 50% less than the current best-practice baiting prescription.Using a rapid eradication assessment, it was proven that a combination of static and mobile surveillance devices could provide a high level of confidence of eradication success early on (4 months post-bait application).This paper describes the context, methodology, and outcomes of this low-sow rate trial in order to inform future projects.DNA profiling from the most recent mouse population established on Te Pākeka/Maud Island identifies the challenges of maintaining island biosecurity with the current available tools and in a context of increasing invasion pathways.The ability to adopt lower sowing rates for island mouse eradications reduces both financial and logistical barriers thereby allowing wildlife managers to implement mouse eradications on the world's most remote islands.

Primary poisoning is an important method to ensure the successful eradication of cats (Felis catus) from large islands.Poison bait options for feral cat eradications and landscape-scale control in New Zealand are limited at present.As part of the development of a toxic bait for cats that can be aerially distributed, a nontoxic palatability trial was undertaken on Auckland Island to compare three types of prototype meat-based bait and one currently registered fishmeal polymer pellet for their palatability to feral cats and non-target species.Degradation rates of baits over a range of environmental conditions were also estimated by taking photographs of baits at regular intervals and inferring degradation from visual appearance of baits over time.Fourteen individual cats were sighted on 144 occasions with all individuals consuming at least one bait type.Results show that the three prototype meat baits were significantly more palatable than the fishmeal polymer baits.No native non-target animals were observed consuming any of the baits during the trial.Fishmeal polymer baits degraded at a slower rate than the meat-based matrices.Palatability results for the meat-based matrices are encouraging.Further trials of a toxic meat-based bait will be required to assess efficacy in pursuit of a registered product for wider use.

Norbormide[5-(α-hydroxy-α-2-pyridylbenzyl)-7-(α-2-pyridylbenzylidene)-5-norbornene-2,3-dicarboximide] (NRB, 1), an existing but infrequently used rodenticide, is known to be uniquely toxic to rats but relatively harmless to other rodents/mammals.However, as an acute vasoactive, NRB has a rapid onset of action, often leading to sub-lethal uptake/bait shyness.Recently, it was brought to our attention that baits containing two independently sourced batches of NRB (which differed noticeably in their stereochemical composition) displayed markedly different palatability/efficacy profiles in rats.Accordingly, with a view to independently evaluating the individual isomers of NRB in rats by means of a palatability and efficacy bait trial, this research describes the isolation of the individual isomers of endo-NRB (Y, V, W and U) from the parent mixture, by means of a chemical derivatization strategy.

Large-scale monitoring of wild populations in remote areas using traditional live-capturing methods is logistically and financially challenging. Devices that can be used to obtain biological material remotely and store it for an extended period have considerable potential to monitor population densities and health status, but their applicability remains largely unexplored. The present study describes a device that collects trace amounts of DNA from the saliva of small mammals that is deposited on the surface of a collection medium (WaxTags®). The device’s performance was evaluated on Australian brushtail possums ( Trichosurus vulpecula ), an invasive pest species and the most significant vector of bovine tuberculosis infective agent ( Mycobacterium bovis ), under field conditions in Canterbury, New Zealand. The retrieved DNA was used to amplify eight possum-specific microsatellite markers and bacterial 16S rRNA. The design is mechanically robust, and the quality of the recovered DNA was adequate for microsatellite-based identification of individual possums, estimation of population density, and partial reconstruction of their oral microbiomes as a potential indicator of health. Several medically important bacteria, including strains of environmental Mycobacterium sp., were detected. The design can be refined to monitor other animals’ populations proactively and provide different levels of information necessary to manage wild populations.

The wrybill (Anarhynchus frontalis) is an endemic plover that breeds only in braided rivers east of the main divide in the South Island of New Zealand. It is threatened by a range of factors, including loss and degradation of habitat, flooding, and predation. We monitored wrybills in 2 sites in the Tekapo River and 2 in the Tasman River in the Mackenzie Basin, South Canterbury, during 3 breeding seasons (1997/98-1999/2000). We aimed to compare survival and productivity between areas with and without trapping (mammalian predator control) to determine whether predator control was associated with higher survival and/or breeding success of wrybills. In the Tekapo River, results were similar between trapped and un-trapped areas, suggesting that control had little effect. In the Tasman River, there were large differences between the two sites and trapping appeared to be beneficial; in the upper river (un-trapped), productivity and survival were very low and in the lower (trapped) site they were high. Over the whole study, 67.3% of nests hatched, and depredation was the largest cause of nest failure. Fledging success (the proportion of chicks hatched that fledged) averaged 35.4%. Losses at the chick stage were higher than at the egg stage, and there was only a weak correlation between nesting success and overall breeding success; we therefore caution against the use of nesting success as a proxy for overall breeding success. Productivity averaged 0.49 chicks fledged per pair over the whole study; when the very low values from the upper Tasman site were excluded, productivity averaged 0.61. Survival of adult male wrybills was lower than survival of females in all four study sites. Measurement of adult survival is important in determining the full effect of predator control (and in determining population trends) but is often overlooked. At the time of our study, wrybill populations in 3 of our 4 study sites appeared not to be self-sustaining and, in the absence of immigration, were in decline. A number of factors, including depredation by mammals, can affect breeding success. Trapping may be beneficial, but temporal and geographic differences in predator densities, as well as variability in other threats (such as flooding and levels of avian predation) mean that predicting when and where mammalian predator control may benefit wrybills is currently difficult.

Invasive species are the major threat to island biodiversity world-wide. Genetic analyses assist in identifying invasion routes as well as revealing population connectivity, which both represent crucial information for conservation management strategies and risk evaluation. Such information is critical to safeguarding vulnerable species on nearshore islands, which often serve as wildlife sanctuaries. The house mouseMus musculushas invaded islands around the world and is a model species for showcasing how genetic tools can be used to inform biosecurity management. The genetic population structure of 316 mice from 12 locations in the upper South Island of New Zealand was determined, using novel GenePlots and traditional population genetic tools based on 10 microsatellite loci, to identify gene flow and reinvasion pathways among mainland and island populations over a decade. On the mainland, populations remained genetically homogeneous over landscape scales of many tens of kilometres. In contrast, historically established island populations only kilometres offshore had low genetic diversity from prolonged isolation. Two islands were potentially colonized from both the mainland and each other in a hybrid swarm. Islands that had recently been invaded or reinvaded in the past decade had genetic profiles consistent with the adjacent mainland, suggesting failure of biosecurity procedures to prevent reinvasion, rather than eradication survivors. Although two islands were invaded by only a few individuals, on a third island many invaders simultaneously arrived. Synthesis and applications. Assessing the genetic structure and connectivity of mainland and island populations of an invasive species, using a combination of traditional and novel visualization tools, has uncovered a spectrum of invasion mechanisms and pathways. These results have informed ongoing biosecurity measures by revealing the locations and intensities of biosecurity threats, allowing targeted management actions to reduce the likelihood of island reinvasion.

The common brushtail possum (Trichosurus vulpecula), introduced from Australia in the mid-nineteenth century, is an invasive species in New Zealand where it is widespread and forms the largest self-sustained reservoir of bovine tuberculosis (Mycobacterium bovis) among wild populations. Conservation and agricultural authorities regularly apply a series of population control measures to suppress brushtail possum populations. The evolutionary consequence of more than half a century of intensive population control operations on the species' genomic diversity and population structure is hindered by a paucity of available genomic resources. This study is the first to characterise the functional content and diversity of brushtail possum liver and brain cerebral cortex transcriptomes. Raw sequences from hepatic cells and cerebral cortex were assembled into 58,001 and 64,735 transcripts respectively. Functional annotation and polymorphism assignment of the assembled transcripts demonstrated a considerable level of variation in the core metabolic pathways that represent potential targets for selection pressure exerted by chemical toxicants. This study suggests that the brushtail possum population in New Zealand harbours considerable variation in metabolic pathways that could potentially promote the development of tolerance against chemical toxicants.

The endemic fauna of New Zealand evolved in the absence of mammalian predators and their introduction has been devastating.Large-scale aerial applications of cereal baits containing sodium fluoroacetate (1080) are routinely used to control these pests.During one such operation in the Blue Mountains, West Otago, trail cameras were used to monitor the impact of the application on mammalian predators.Both stoats and rats were regularly recorded on cameras throughout the study area before the poison operation, but no stoats or rats were recorded the day after the operation, and none had returned by the time monitoring ended 38 days later.Possum, mouse and hedgehog detections were also significantly reduced.The aerial 1080 operation was therefore effective at controlling pests, and there was no evidence of a decline in bird or deer abundance due to non-target poisoning.Before this study it was not known that hedgehogs could be controlled by aerial 1080; this finding reveals an added benefit from its application.The use of trail cameras was effective at monitoring a range of species and although more labour-intensive than traditional monitoring methods, it provided more detailed information.

All multicellular organisms host a wide diversity of microorganisms in and on their bodies, which are collectively known as their microbiome. Characterising microbial communities that inhabit different body niches in wild animals is critical to better understand the dynamics of microbiome diversityand its functional significance. The current study is the first to apply massively parallel sequencing of 16S rRNA to characterise the microbial diversity and functional content of oral microbiota in two of New Zealand’s most important invasive mammals, the omnivorous common brushtail possum (Trichosurus vulpecula) and the carnivorous stoat (Mustela erminea). In total, strains of bacteria belonging to 19 different phyla, 27 classes, 52 orders, 103 families, 163 genera and 51 known species were identified from the oral cavities of the study species. Strains of the phyla Proteobacteria, Firmicutes, Bacteroidetes, Fusobacteria, and Actinobacteria dominated the core oral microbial diversity in both species, while other taxa were comparatively less abundant. Despite invasive populations typically demonstrating limited genetic variation, intraspecific variation of the core bacterial taxa in the oral microbiota was considerable. This suggests that a complex interaction between genetic, physiological, and environmental factors determines the diversity of the study species’oral microbiome.

The authors declare no conflict of interests.

The New Zealand brushtail possum (Trichosurus vulpecula), introduced from Australia in the 1850s, is an invasive species that is widespread throughout New Zealand and forms the largest self-sustained reservoir of bovine tuberculosis (Mycobacterium bovis) in the wild. Conservation and agricultural authorities regularly apply a series of population control measures to suppress brushtail possum populations. The evolutionary consequence of more than half a century of intensive population control operations on the species genomic diversity and population structure is hindered by a paucity of available genomic resources for the species. This study is the first to characterise the functional content and diversity of brushtail possum liver and brain cerebral cortex transcriptomes. Raw sequences from hepatic cells and cerebral cortex were assembled into 58,001 and 64,735 transcripts in hepatic cells and cerebral cortex, respectively. Functional annotation and polymorphism assignment of the assembled transcripts demonstrated a considerable level of variation in the core metabolic pathways that represent potential targets for selection pressure exerted by chemical toxicants. This study suggests that the brushtail possum population in New Zealand harbours considerable levels of variation in metabolic pathways that could potentially promote the development of tolerance against chemical toxicants.

Whether the behaviors of individuals at low population densities differ from those at higher densities is critically informative for predictions of theoretical and experimental ecology, as well as for the conservation management of endangered or introduced species. The globally widespread house mouse Mus musculus is a frequently invasive species; detailed analyses of its low-density behavior will allow for better understanding of population dynamics at early stages of invasions and for generating clearer designs of timely management interventions. Opposite-sex pairs of house mice were released in a small number of replicates at opposite ends of a small, 6ha island in New Zealand, that had been made experimentally rodent-free, to investigate spatial distributions and ranging behaviors at very low densities by simulating a new invasion of the island with each release trial. Successfully introduced mice (n=15) of both sexes had twofold greater nightly movements, and tenfold larger range sizes, relative to mice trapped and tracked on the same island prior to eradication. This allowed new arrivals to rapidly and reliably overlap with the range of the opposite sex on the island, especially during the breeding season, suggesting that the driver behind increased ranging was mate searching. Despite the study's small total sample size, the dramatically increased ranging behaviors exhibited by new arrivals on a mouse-free island imply that this species may avoid potential Allee effects through success in mate searching even at low density. Such behavioral shifts in ranging could contribute to the pervasive success of house mice in founding invasive populations even at extremely low initial densities.

The endemic fauna of New Zealand evolved in the absence of mammalian predators and the introduction of the latter has been devastating. There have been numerous avian extinctions and 80% of the extant native avian taxa are currently threatened or at risk of extinction. Declines continue, and a fundamental change in predator management is required. In 2016 came the announcement of the ambitious Predator Free 2050 (PF 2050) programme, which aims to eradicate rats, mustelids, and Brushtail Possums from New Zealand by 2050. This paper reviews some of the many techniques being discussed or developed to implement the programme. Existing techniques are being refined and new tools are being developed. Research on new toxins, including those with potentially higher species specificity, is under way, and novel baits and toxin-delivery devices are being developed. Existing trap designs are being refined, and new self-resetting traps capable of multiple kills have been developed. Research is also under way on new lures and repellents. Eradications may be achieved in stages, and barriers (both natural and artificial) will be needed to protect areas already cleared. Current techniques will probably be inadequate to effect nationwide eradications, and new tools (possibly based on genetic technologies) will probably be required. Regulatory hurdles will need to be overcome, and community consultation and support (social licence) will be required throughout the programme. The use of some new technologies may be contentious, and not every new idea will necessarily be adopted. Technical, social, and organisational challenges exist, and national and international collaboration will be required for PF 2050 to succeed.

The diet, population structure and breeding of ship rats (Rattus rattus L.) from Fiordland National Park were assessed from measurements and gut sample analysis of 248 rats trapped between March 2009 and March 2010, following a mast beech seedfall. They consumed many lepidopteran larvae but fewer weta and more vegetative plant matter than in other habitats, as well as beech seed. Birds and mice made up only a relatively small proportion of the diet. A lizard was also confirmed as a prey item of R. rattus, for the first time in New Zealand. The population included a high proportion of young rats and females that were breeding at an early age. A high percentage of females in breeding condition in each season, high uterine scar counts and consistent litter sizes throughout the year indicate high fecundity and year-round breeding. This breeding cycle is consistent with an ample food supply being available for rodents promoting a rat population irruption, which in turn may increase the predation pressure on native biodiversity.

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.

The impacts of house mice (Mus musculus), one of four invasive rodent species in New Zealand, are only clearly revealed on islands and fenced sanctuaries without rats and other invasive predators which suppress mouse populations, infl uence their behaviour, and confound their impacts. When the sole invasive mammal on islands, mice can reach high densities and infl uence ecosystems in similar ways to rats. Eradicating mice from islands is not as diffi cult as previously thought, if best practice techniques developed and refi ned in New Zealand are applied in association with diligent planning and implementation. Adopting this best practice approach has resulted in successful eradication of mice from several islands in New Zealand and elsewhere including some of the largest ever targeted for mice; in multi-species eradications; and where mouse populations were still expanding after recent invasion. Prevention of mice reaching rodent-free islands remains an ongoing challenge as they are inveterate stowaways, potentially better swimmers than currently thought, and prolifi c breeders in predator-free habitat. However, emergent mouse populations can be detected with conventional surveillance tools and eradicated before becoming fully established if decisive action is taken early enough. The invasion and eventual eradication of mice on Maud Island provides a case study to illustrate New Zealand-based lessons around mouse biosecurity and eradication.

Otamahua/Quail Island is an 85 ha Recreation Reserve in Lyttelton Harbour, New Zealand. R is being ecologically restored and cats, hedgehogs, rabbits, mustelids and rats have been eradicated. However, the house mouse (Mus musculus) survived two eradication attempts, a bait station operation in 2002 and an aerial operation in 2009. Data on aerial bait deposition, bait degradation, mouse resurgence and non-target mortalities were collected. Brodifacoum bait deposition in many areas was considerably lower than the prescribed rate of 8 kg/ha. Mouse sign was simultaneously detected at seven sites around the island 6 months after the aerial operation. Tails were collected from trapped mice on Quail Island, the adjacent mainland and on the stepping-stone island (King Billy) to undertake DNA analysis. Little genetic discrimination was observed between samples obtained after the 2009 aerial bait operation, and samples from before or outside of the bait drop. By contrast, samples taken from a location 15 km distant were genetically distinguishable. Intensive trapping was also trialled in a 2 ha area as a possible strategy to regulate the mouse density using two trap designs and three bait types. Mouse trapping data indicated that abundance was highest in May and lowest in January. The results are discussed in terms of mouse eradication and management.