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Predators play a critical role in ecosystems; however, when overly abundant, they can disrupt natural processes and cause extinctions of species. In particular, oceanic islands have endured many impacts of introduced mammalian predators. Whereas knowledge and management of introduced mammalian predators on islands is well advanced in natural landscapes, in inhabited landscapes, spanning rural and urban environments, comparatively less is known. We summarise key issues from the natural and social sciences in the management of introduced mammalian predators in inhabited landscapes of Aotearoa–New Zealand. We describe the shift in focus over the past few decades from management of introduced mammalian herbivores to predators in rural environments, and the growth in management of introduced mammalian predators in urban environments, both seeking to emulate conservation gains made in forested landscapes. We discuss the circumstances around companion animal management at the interface of the natural and social sciences. We summarise surveys of attitudes towards introduced mammalian predators, the role of biodiversity comanagement between Ma¯ori and Pakeha, and the importance of also considering non-biodiversity benefits from introduced predator management. We describe the rise of community predator control and large landscape projects aspiring for a ‘Predator Free New Zealand’, and how such an aspiration must be concurrent with habitat restoration. We make recommendations for further research on the basic population biology of predators in inhabited landscapes, and more long-term studies. Such studies should be integrated with examination of the motivations for predator management, as well as the biodiversity and social outcomes of such management. We conclude by remarking that introduced predator management is only one component of a robust national strategy for conservation of native biodiversity in New Zealand.

Eradication of introduced species from inhabited islands requires consideration of both technical and social feasibility. Historically, biologists have struggled to engage successfully in the social components of eradication planning. Island communities have unique features that require consideration in eradication planning. Social impact assessment is a powerful planning tool used widely outside of wildlife management. We outline the core components of a social impact assessment as it could be applied to eradication planning on inhabited islands. We summarise previous experience in social impact assessment and community engagement for introduced predator eradication on inhabited islands, and as an example develop a social profile for inhabited islands of the Hauraki Gulf of New Zealand. We conclude that social impact assessment has great potential to improve eradication feasibility assessment, and should be applied routinely in eradication scoping on inhabited islands.

The eradication of some introduced pests such as rats, stoats and possums in New Zealand seems increasingly feasible with successful action to date in various cities (e.g. Wellington City) and with the government’s national 2050 predator-free goal. Here we specifically detail the potential benefits of urban rat eradication and find these cover a wide range of topics including a potentially reduced risk of infection from at least seven zoonotic diseases (e.g. leptospirosis, toxoplasmosis, trichinellosis, murine typhus; and three enteric diseases). Other potential benefits include: psychological benefits from increased native bird life in cities; reduced damage to food supplies; reduced rat damage to building insulation and to building walls and roofing; and reduced fires in buildings associated with rat damage. However, there is considerable uncertainty on the size of such impacts and so we outline a tentative research agenda as a first step towards quantification of the likely key public health benefits of rat eradication.

Introduced rats (Rattus spp.) can affect island vegetation structure and ecosystem functioning, both directly and indirectly (through the reduction of seabird populations). The extent to which structure and function of islands where rats have been eradicated will converge on uninvaded islands remains unclear. We compared three groups of islands in New Zealand: islands never invaded by rats, islands with rats, and islands on which rats have been controlled. Differences between island groups in soil and leaf chemistry and leaf production were largely explained by burrow densities. Community structure of woody seedlings differed by rat history and burrow density. Plots on islands with high seabird densities had themost non-native plant species. Sincemost impacts of rats were mediated through seabird density, the removal of rats without seabird recolonization is unlikely to result in a reversal of these processes. Even if seabirds return, a novel plant community may emerge.

New Zealand, an archipelago of more than 2000 islands, has a terrestrial fauna especially depauperate in native land mammals. Kiore (Rattus exulans) was the first of four rodent species introduced by people. A project to eradicate invasive rats from Kapiti Island in 1996, represented a turning point in the technology, complexity and scale at which managers of natural heritage on New Zealand islands could operate. This paper includes case studies of some significant projects targeting rodents, sometimes with other introduced mammals, undertaken in the 12 years following Kapiti. Details of the methods, costs, results and outcomes are provided for Kapiti, Whenua Hou, Tuhua, Campbell, Raoul, Hauturu, Taukihepa, and Pomona islands, collectively representing a total of over 23,000 ha of habitat cleared of introduced mammals. Research and trials undertaken in the Kapiti project provided the basis for future environmental risk assessments, allowing other projects to focus on knowledge gaps. New trends in invasive species eradication in New Zealand include more challenging multi-species eradication projects, some of which are undertaken by self- funded community groups. To summarise the lessons of the New Zealand experience: a programmatic approach is recommended which will fit each eradication within a context or framework of goals for those islands; address biosecurity issues at the outset; build capability to attempt the most challenging and rewarding projects; facilitate investment in monitoring and manage expectations of stakeholders to ensure their ongoing support. Success breeds success but is never guaranteed.

New Zealand’s offshore and outlying islands have long been a focus of conservation biology as sites of local endemism and as last refuges for many species. During the c. 730 years since New Zealand has been settled by people, mammalian predators have invaded many islands and caused local and global extinctions. New Zealand has led international efforts in island restoration. By the late 1980s, translocations of threatened birds to predator-free islands were well under way to safeguard against extinction. Non-native herbivores and predators, such as goats and cats, had been eradicated from some islands. A significant development in island restoration in the mid-1980s was the eradication of rats from small forested islands. This eradication technology has been refined and currently at least 65 islands, including large and remote Campbell (11 216 ha) and Raoul (2938 ha) Islands, have been successfully cleared of rats. Many of New Zealand’s offshore islands, especially those without predatory mammals, are home to large numbers of breeding seabirds. Seabirds influence ecosystem processes on islands by enhancing soil fertility and through soil disturbance by burrowing. Predators, especially rats, alter ecosystem processes and cause population reductions or extinctions of native animals and plants. Islands have been promoted as touchstones of a primaeval New Zealand, but we are now increasingly aware that most islands have been substantially modified since human settlement of New Zealand. Archaeological and palaeoecological investigations, together with the acknowledgement that many islands have been important mahinga kai (sources of food) for M?ori, have all led to a better understanding of how people have modified these islands. Restoration technology may have vaulted ahead of our ability to predict the ecosystem consequences of its application on islands. However, research is now being directed to help make better decisions about restoration and management of islands, decisions that take account of island history and key drivers of island ecosystem functioning.