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Aotearoa—New Zealand has only four rodent species, all introduced. In order of arrival, they are Pacific rat Rattus exulans, brown rat R. norvegicus, house mouse Mus musculus, and black rat R. rattus. Rodent management in New Zealand aims mainly to conserve indigenous biodiversity rather than to protect crops or manage diseases, as is usual elsewhere. We describe four major "regimes" and one major vision for rodent control in New Zealand to meet ecological restoration objectives. Current challenges for island eradications are for large islands that are remote or populated by people. Aerial 1080 is the only large‐scale (tens of thousands of hectares) option for black rat control, but its application requires adjustment to counter subsequent rapid black rat repopulation. Unfenced "ecosanctuaries" (mean 720 ha) use ground‐based traps and poisons to target mainly black rats and face constant reinvasion. Ecosanctuaries with mammal‐resistant fences (up to 3500 ha) limit reinvasion and target more pest species and have enabled the return of previously extirpated taxa to the main islands. Predator Free 2050 aims to eradicate the rat species (but not mice) plus some other introduced mammals from New Zealand by 2050. This vision is not attainable with current tools, but research and experimental management is exploring techniques and technologies. The large scale (to 100 000 ha) at which black rats are now targeted for control to extremely low abundance seems to be unique to New Zealand. [ABSTRACT FROM AUTHOR]

Simple Summary: Restoration of biodiversity in urban green spaces frequently requires eradication or management of invasive species. We aimed to identify fine- and landscape-scale habitat features associated with the presence of five invasive urban mammals (Rattus species, European hedgehogs, mice, and brushtail possums) in three urban green space types (forest fragment, amenity park, residential garden) across three New Zealand cities, and across two seasons, to identify where management effort should be focused. All species were detected in all greenspace types; however, rodents were detected least in residential gardens, possums were detected most often in forest fragments, and hedgehogs least in forest fragments. Proximity of amenity parks to forest patches was positively associated with possum and hedgehog presence and negatively with rats. Conversely, proximity of residential gardens to forest patches was positively associated with rat presence. Management of rats should focus on sites with shrub and lower canopy cover and of mice on sites with herb layer cover, while micro-habitat features were not important for hedgehogs and possums. Rats were most likely to be found in residential gardens with compost heaps. The wide distributions of these species suggest that in order to be successful, ecological restoration must be coordinated, target all green space types, and engage urban residents. A barrier to successful ecological restoration of urban green spaces in many cities is invasive mammalian predators. We determined the fine- and landscape-scale habitat characteristics associated with the presence of five urban predators (black and brown rats, European hedgehogs, house mice, and brushtail possums) in three New Zealand cities, in spring and autumn, in three green space types: forest fragments, amenity parks, and residential gardens. Season contributed to variations in detections for all five taxa. Rodents were detected least in residential gardens; mice were detected more often in amenity parks. Hedgehogs were detected least in forest fragments. Possums were detected most often in forest fragments and least often in residential gardens. Some of this variation was explained by our models. Proximity of amenity parks to forest patches was strongly associated with presence of possums (positively), hedgehogs (positively), and rats (negatively). Conversely, proximity of residential gardens to forest patches was positively associated with rat presence. Rats were associated with shrub and lower canopy cover and mice with herb layer cover. In residential gardens, rat detection was associated with compost heaps. Successful restoration of biodiversity in these cities needs extensive, coordinated predator control programmes that engage urban residents. [ABSTRACT FROM AUTHOR]

Fenced ecosanctuaries may reduce predator presence at reserves by incorporating deterrents into pest management programmes. We quantified rodent visits to the steel hood of ecosanctuary fencing and illuminated our experimental sites to assess whether light could deter ship rats (Rattus rattus) and house mice (Mus musculus). Additionally, we assessed how mice used fencing in the presence and absence of ship rats by utilising two types of fence sections: one accessible to mice alone (along fencing within an ecosanctuary) and one accessible to mice and rats (at perimeter fence sites opposite pasture or forest habitat). We monitored sites using cameras and tracking cards within the fence hood and at tunnels at the fence base. Along the internal fence, mice were never observed within the hood but marked 40% of tunnels at the fence base. Along the perimeter fence, mice made four visits to the hood and marked 28% of tunnels at the fence base. Rats travelled exclusively within the fence hood (n = 42). Light did not reduce rat sightings but adjacent habitat affected their presence (forest > pasture; p ≤ 0.01). Positioning future ecosanctuary fencing alongside pasture and maintaining open corridors opposite fences at current ecosanctuaries may reduce rat presence. [ABSTRACT FROM AUTHOR]

Determining pest mammal impacts and abundance in forests requires an understanding of how target species use vegetation compared with the ground. We used a novel device combining footprint tracking with bite detection to survey for mammals at four levels in New Zealand forests that had house mice (Mus musculus) alone, and all widespread New Zealand mammals, including house mice, ship rats (Rattus rattus) and brushtail possums (Trichosurus vulpecula). When alone, house mice were detected at 93%, 35%, 17% and 0% of devices on the ground, in shrubs, in the subcanopy and canopy, respectively, but in a pilot study at one site were detected 11 m above ground. When all small pest mammals were present, house mice were scarce and none were detected up trees. Ship rats and possums were detected mostly on the ground, but also at all surveyed heights. The study confirms that mice, ship rats and possums are all potential above-ground predators, but suggests that targeting them for control and monitoring can reasonably be undertaken on the ground. [ABSTRACT FROM AUTHOR]

Control operations for invasive ship rats, Rattus rattus, in New Zealand forests are often followed by increased house mouse, Mus musculus, detections suggesting rats suppress mice. A potential mechanism is intraguild predation, either by interference competition or as simple predatory behaviour. If aggression by rats towards mice is mainly competitive, it should include threat and display features associated with, for example, intraspecific fighting. If predatory, it should lack these features and be associated with feeding. In the first of two captive experiments we observed interactions between paired, live rodents, either side of a wire-mesh screen, and found that most rats were aggressive to mice. This aggression lacked threat and display characteristics typical of encounters with conspecifics and was rarely reciprocated by mice. In a second experiment, euthanized mice were drawn by a line through cages occupied by rats fed either a restricted or unrestricted diet. Rats of both groups attacked and restrained the euthanized mice, and all rats that interacted with the mice ate at least part of them, although food-restricted rats tended to eat more. As the aggressive response of ship rats towards mice lacked threat and display features and was related to feeding, we conclude that it resembles predatory behaviour. Our findings provide a better understanding of the interactions between ship rats and house mice, which hinder their management where they coexist as damaging invaders. However, further research is required to determine whether the results of our captive experiments are consistent with wild rat behaviour. [ABSTRACT FROM AUTHOR]

Efforts to eradicate multiple mammal pests from offshore islands and fenced mainland 'habitat islands' often fail to remove mice, and such failures can result in a dramatic change in the food-web whereby the removal of larger mammal pests facilitates a population explosion of mice through predator and competitor release. We investigated the ecological responses of house mice to the removal of mammalian predators from a 500-ha fenced sanctuary at Tawharanui, northern New Zealand. Data on population structure and body condition of mice trapped in 2007, in four habitat types within the sanctuary, were compared with baseline data collected in 2001, before mammal control operations commenced. We hypothesized that: (i) in the absence of mammalian predators mouse densities would increase in all habitat types that provide vegetation cover, and (ii) in the absence of mammalian competitors mice would become heavier due to greater access to food resources. Mouse densities were significantly higher in 2007 than in 2001 in three habitat types. The high density of mice in forest - where none were trapped prior to control - suggests a competitive release, in which mice profited from the removal of ship rats. No mice were caught in the presence of ship rats on a forest trap-line at a control site outside the sanctuary. Mice trapped in 2007 were significantly heavier than those trapped in 2001, and significantly heavier than mice trapped at the control site. Greater access to food in the absence of competing and predatory mammals probably explains the heavier body weight of Tawharanui mice. There has been a significant change in the mammalian food-web at Tawharanui, such that the house mouse is now the primary pest. A rapid and dramatic increase in mouse numbers is likely to adversely impact invertebrates and seedling recruitment, which in turn could affect ecosystem functions. [ABSTRACT FROM AUTHOR]

House mice ( Mus musculus) are a widespread introduced species with major but often overlooked impacts on ecosystems, proportionally greater when they are the only introduced mammal present. Studies conducted on the ecology of mice on Antipodes Island, where they are the only introduced mammal, are presented and compared to previous work over the past four decades. Mice live-trapped on grids were more abundant in dense coastal tussock (147 mice/ha) compared to inland plateau grasslands (59 mice/ha), with a significant effect of age, but not sex, on both capture probability and range size. Body-size of mice has not changed over four decades, providing no evidence of gigantism, which on other Southern Ocean islands has been speculated to increase the predation risk to birds. Over 2,405 invertebrates from fourteen Orders were identified from pitfall traps and litter samples across five sites. Differences in invertebrate communities and taxonomic units attributable to habitat and altitude were detected among sites in both pitfall and litter samples on Antipodes Island. Differences in invertebrate communities were detected from litter samples on a neighbouring mouse-free island, with significantly greater abundance of large Amphipods and Collembola, but fewer Spiders. These data on introduced mouse ecology and invertebrate distribution on Antipodes Island contribute to the body of knowledge on Southern Ocean islands. [ABSTRACT FROM AUTHOR]