David R Towns

New Zealand Department of Conservation

Islands are biodiversity hotspots, but their native inhabitants are vulnerable to predation from exotic predators. Conservation of island endemics has often involved translocating captive‐reared populations to predator‐free refugia. However, the long‐term success of these translocations has rarely been assessed. We investigated the traits that maxi...

Global biodiversity loss is accelerating at an alarming rate. While considerable effort and resources have gone into conservation management for many threatened species in New Zealand (NZ), some species are still ‘losing the battle’ despite much effort, and others have been ignored altogether. Here, we present seven case studies to illustrate the b...

Identifying stakeholders and analysing the pattern of relationships among them are important steps toward collaborating with individuals and groups for collective action. The process of stakeholders’ communication can be understood by interpreting the structure of the network in which stakeholders operate. Our study attempted to identify stakeholde...

Burrowing seabirds that nest on islands transfer nutrients from the sea, disturb the soil through burrowing, damage tree foliage when landing, and thereby modify the surface litter. However, seabirds are in decline worldwide, as are their community- and ecosystem-level impacts, primarily due to invasive predatory mammals. The direct and indirect ef...

Protecting seabirds is a global conservation priority given that 29% of seabird species are threatened with extinction. One of the most acute threats to seabirds is the presence of introduced predators, which depredate seabirds at all life stages, from eggs to adults. Consequently, eradication of invasive predators has been identified as an effecti...

Public participation theory assumes that empowering communities leads to enduring support for new initiatives. The New Zealand Biodiversity Strategy, approved in 2000, embraces this assumption and includes goals for community involvement in resolving threats to native flora and fauna. Over the last 20 years, community-based ecological restoration g...

The current distribution of New Zealand lizards has been influenced by past geological events, habitat destruction and introduced predators. Perhaps as a reflection of long isolation, and at least 20 million years of climatic and geological change, the proportion of lizard species that are habitat generalists is relatively low, and high levels of s...

Conservation actions are heavily influenced by value judgements and cultural perceptions. The huge lizard fauna of New Zealand played a prominent role in the worldview of the first people (Māori), but appeared to be poorly appreciated by European settlers. Early legislation to protect native fauna explicitly excluded lizards, which remained unprote...

One of the most acute threats to seabirds is introduced predators, which depredate seabirds at all life stages from eggs to adults. Consequently, predator eradication has been identified as an effective and commonly used seabird conservation method. Global monitoring of seabird responses to eradication includes measures of what drives passive seabi...

Globally, one in five reptile species is threatened with extinction, with invasive species a leading cause of extinction risk. Translocations could alleviate the risk of extinction through the establishment of populations in locations from which invasive predators have been removed. But do translocations represent a viable strategy for reptile cons...

Predator eradication on New Zealand’s offshore islands is an effective tool for seabird conservation. However, limited resources and the remoteness and number of these islands pose considerable challenges to achieving long-term monitoring and research objectives. Therefore, economical and effective monitoring tools are needed. Advances in remote se...

Following the removal of an introduced species, island restoration can follow two general approaches: passive, where no further intervention occurs and the island is assumed to recover naturally, and; active, where recovery of key taxa (e.g. seabirds) is enhanced by manipulating movement and demography. Steps for deciding between these techniques a...

More than US$21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of w...

The progressive removal of invasive mammals from the Mercury Islands has led to over 25 years of field study designed to test the processes of restoration and natural recovery of these seabird-driven island ecosystems. Resulting from this work, four key restoration questions can now be identified as fundamental to designing island restoration progr...

A pluralist and cross-cultural approach that accommodates differing values while encouraging the collaboration and social cohesion necessary for the complex task of ecological restoration is needed. We used qualitative and quantitative analyses to investigate value assigned to biocultural restoration of coastal forests in northern New Zealand by 26...

More than half (53%) of Procellariiforme seabirds (tube-nosed seabirds) are experiencing rapid population declines due to reduced fledgling survival rates and adult mortality. Seabirds are vulnerable to multiple threats on land; introduced predators and habitat loss, and at sea; plastic pollution ingestion, fisheries interactions, prey distribution...

Vertebrate consumers can be important drivers of the structure and functioning of ecosystems, including the soil and litter invertebrate communities that drive many ecosystem processes. Burrowing seabirds, as prevalent vertebrate consumers, have the potential to impact consumptive effects via adding marine nutrients to soil (i.e. resource subsidies...

The size and distribution of colonies of burrow-nesting petrels is thought to be limited partly by the availability of suitable breeding habitat and partly by predation. Historically, the availability of safe nesting habitat was restricted in New Zealand, due to the introduction of rats by humans. More recently, however, habitat has been restored b...

Despite calls to better link research and practice, the gap between knowing and doing continues to limit conservation success. Here we report on the outcomes from a workshop at the Society for Conservation Biology Oceania Conference 2014 on bridging the research–implementation gap. The workshop highlighted how the gap is still very real in conserva...

Given that 29% of seabird species are threatened with extinction, protecting seabird colonies on offshore islands is a global conservation priority. Seabirds are vulnerable to non-native predator invasions, which reduce or eliminate colonies. Accordingly, conservation efforts have focused on predator eradication. However, affected populations are o...

In many ecosystems food-web dynamics are driven by spatial and temporal variation in the availability of sugar resources, which form the primary or even exclusive dietary constituents for many species. Scale insects (Hemiptera) produce sugar-rich honeydew, which can be a keystone sugar source in honeydew ecosystems worldwide. In New Zealand, most p...

Translocations are an important conservation tool used to restore at-risk species to their historical range. Unavoidable procedures during translocations, such as habitat disturbance, capture, handling, processing, captivity, transport and release to a novel environment, have the potential to be stressful for most species. In this study, we examine...

Eradication of introduced mammalian predators from islands has become increasingly common, with over 800 successful projects around the world. Historically, introduced predators extirpated or reduced the size of many seabird populations, changing the dynamics of entire island ecosystems. Although the primary outcome of many eradication projects is...

Many conservation decisions rely on the assumption that multiple populations will respond similarly to management. However, few attempts have been made to evaluate indicators of population trends (i.e. population indicator species). Eradication of introduced mammals from offshore islands is a commonly used management technique for conservation of n...

Traditional food web organisation has been taxonomically based, which can make the webs complicated and difficult to interpret using simple statistical methods. Ecological network research has potential to assist such analyses, but also emphasises complexity rather than capacity to understand the patterns involved. Using social network analysis it...

Interdisciplinary approaches to conservation science remain limited, and there is often little understanding of the ways different social, cultural and political systems are intertwined with the environment. However, understanding interactions within these systems is often crucial to the acceptability and success of long-term conservation managemen...

Context. Invasive mammals have been removed from at least 100 offshore islands around New Zealand, covering a total area of around 45 000 ha. Aims. To review the outcomes of eradications, the statutory and social environment in which the eradications were conducted, and the lessons provided for future work. Methods. Native species to benefit from t...

New Zealand's offshore islands are refuges for many threatened species, a high proportion of vertebrate diversity, and the world's most diverse fauna of seabirds. We present key issues and questions that can be used to guide research on the conservation of biodiversity on these islands. Four global reviews formed a basis from which we identified re...

This chapter investigates the direct impacts of introduced seabird predators on the terrestrial plants and other animals that inhabit seabird islands. It discusses the direct effects of seabird predators on arthropods, mollusks, amphibians, reptiles, land birds, mammals, and plants. It analyzes various studies that look into what determines species...

This chapter demonstrates solutions to damages done to island ecosystems. It cites David Cameron Duffy's 1994 study where he observed that feral animals, diseases, and forest destruction had greatly modified island ecosystems that most were unrecognizable. It highlights how most island management projects focus only on the restoration of single or...

This chapter focuses on the impacts of seabird predators on seabirds and describes the ways to measure these impacts. It identifies the most damaging of these invasive species and assesses which species of seabirds are the most vulnerable to them. It evaluates the predators in terms of their global distribution and efficacy in reducing seabird popu...

This chapter explores the techniques, limitations, and ethical frameworks of eradicating introduced predators of seabirds. It addresses ethical concerns that should inform eradication decisions, and the essential need to engage to multiple stakeholder groups in eradication and restoration decisions. It describes how the public and other institution...

This chapter considers the roles of various stakeholder groups in conservation, eradication, restoration, and monitoring efforts of seabird island ecosystems. It describes the range of roles of groups from engagement through public education to direct participation in efforts on the islands. It explains the pivotal role of public involvement in a r...

Islands with large colonies of seabirds are found throughout the globe. Seabird islands provide nesting and roosting sites for birds that forage at sea, deposit marine nutrients on land, and physically alter these islands. Habitats for numerous endemic and endangered animal and plant species, seabird islands are therefore biodiversity hotspots with...

The current primary threats to biodiversity on a global scale are species invasions and habitat modification. Management of vulnerable populations often involves a lengthy sequence of 1) research to identify threats and recommend management strategies, 2) active management, and 3) results monitoring to assess effectiveness of management. The last m...

Reintroduced populations of threatened species are often founded by a small number of individuals, but maximising genetic diversity is often a criterion for founder selection. Reintroduction of pregnant females has been proposed as a means of maximising productivity and genetic diversity, but it is unclear whether the release of pregnant females in...

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 eff...

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...

The consequences of inbreeding in small isolated populations are well documented, yet populations are often managed in isolation to avoid irreversibly mixing genetic lineages and to maintain the historic integrity of each population. Three remaining populations of Whitaker's skink (Cyclodina whitakeri) in New Zealand, remnants of a once wider distr...

Invasive species are a global problem but most studies have focused on their direct rather than indirect ecological effects. We studied litter and soil-inhabiting invertebrate communities on 18 islands off northern New Zealand, to better understand the indirect ecological consequences of rat (Rattus) invasion. Nine islands host high densities of bu...

Eradications of kiore or Pacific rats (Rattus exulans) from islands around New Zealand have been followed by responses from resident species of coastal plants, invertebrates, reptiles and seabirds. These responses are compared with an invasion by ship rats (Rattus rattus), which devastated populations of invertebrates, birds and bats. Post-eradicat...

Rats continue to invade rat-free islands around the world, and it remains difficult to successfully intercept them before they establish populations. Successful biosecurity methods should intercept rats rapidly, before they can establish a population. Current island biosecurity practice employs techniques used for high-density rat eradication, assu...

In this paper, we review and analyse how three species of invasive rat (Rattus rattus, R. norvegicus and R. exulans) disperse to and invade New Zealand offshore islands. We also discuss the methods used to detect and prevent the arrival of rats on islands. All species of invasive rat can be transported by ship. However, rats can also swim to island...

Invasive mammalian predators such as rats are now widespread on islands, but hypotheses about their effects have rarely been tested. Circumstantial evidence from New Zealand indicates that, when introduced to islands, Pacific rats (Rattus exulans) have negative effects on endemic plants, invertebrates, birds, and reptiles, including the tuatara (Sp...

Invasive rats continue to colonize rat-free island s around the world. To prevent rats from establishing on rat-free islands, especially follow ing their eradication, biosecurity actions are requ ired to enable early detection and elimination. Rats arrive at islands by both human transportation and by swi mming. There are very little data on the ra...

First records of terrestrial oviposition by Leptoceridae are provided for 2 Australian species: Lectrides varians Mosely (Triplectidinae) and Leptorussa darlingtoni (Banks) (Leptocerinae). Egg masses of both species were deposited above a permanent pool in an intermittent section of Brownhill Creek, a stream near Adelaide, South Australia. L. darli...

Predators often exert multi-trophic cascading effects in terrestrial ecosystems. However, how such predation may indirectly impact interactions between above- and below-ground biota is poorly understood, despite the functional importance of these interactions. Comparison of rat-free and rat-invaded offshore islands in New Zealand revealed that pred...

Introduced rats are now being eradicated from many islands. Increasingly, these eradications are contested by activists claiming moral, legal, cultural, historic or scientific reasons and poorly documented evidence of effects. We reviewed the global literature on the effects of rats on island flora and fauna. We then used New Zealand as a case stud...

The macro-invertebrate fauna of Waitakere River and its tributaries, a northern New Zealand kauri forest stream, was surveyed in January 1974 and January and June 1975, as part of a study on stream community dynamics. This survey and regular samples in the study area provided 144 taxa, almost three times the maximum number previously recorded from...

1. Brown Hill Creck, a small intermittent stream in dry sclernphyll forest in South Australia, flows for about 6 months during winter and spring. When flow ceases the stream dries to isolated pools which receive high summer inputs of Eucalyptus obliqua litter. Decomposition of this material in remnant pools causes extremely dark waters and depresse...

Habitat use of the endangered chevron skink (Oligosoma homalonotum) was investigated between 1997 and 2002 at three sites on Great Barrier Island, New Zealand. Habitat preferences were determined by pitfall trapping and radio-tracking studies, and a comparison of catchments with and without chevron skinks. Over the course of the research, 88 skinks...

A single Norway rat released on to a rat-free island was not caught for more than four months, despite intensive efforts to trap it. The rat first explored the 9.5-hectare island and then swam 400 metres across open water to another rat-free island, evading capture for 18 weeks until an aggressive combination of detection and trapping methods were...

Over the last four decades the eradication of rats from islands around New Zealand has moved from accidental eradication following the exploratory use of baits for rat control to carefully planned complex eradications of rats and cats (Felis catus) on large islands. Introduced rodents have now been eradicated from more than 90 islands. Of these suc...

The coast-inhabiting Suter's skink ( Oligosoma suteri ) has a fragmented distribution on islands around northern New Zealand, which has been attributed to the effects of introduced predators. We used classification trees to assess a range of factors that might influence the distribution of Suter's skinks. We then assessed the vulnerability to preda...

Insular environments, ranging from oceanic islands to fragments of once-contiguous natural systems, have long been used by biologists to test basic principles of ecology, evolution and biogeography. More recently, insular environments have figured prominently in conservation ecology, where the aim has usually been to conserve species or assemblages...

Aim Success with eradicating invasive species from islands around New Zealand raises the prospect of reversing the loss of species by restoring biotic communities on modified islands. I seek to identify methods that can be used to clarify restoration targets on Korapuki Island, which was modified by introduced mammals until 1987. Location Korapuki...

The native terrestrial reptile fauna of New Zealand comprises the last representatives of the Sphenodontida — two species of tuatara (Sphenodon) — and about 60 species of lizards in four endemic genera: Hoplodactylus and Naultinus (Gekkonidae), Cyclodina and Oligosoma (Scincidae). The entire fauna is strictly protected by legislation, but both spec...

The successful removal of rodents from islands around New Zealand has enabled translocation of rare species of lizards to new sites within their former range. Four species of skinks were translocated to Korapuki Island, Mercury Islands, New Zealand: Cyclodina alani, C. oliveri, C. whitakeri and Oligosoma suteri. Responses of three of the lizard spe...

Aspects of reproduction and condition in northern tuatara (Sphenodon punctatus punctatus) were examined in the presence and absence of an introduced rat, the kiore (Rattus exulans), between 1996 and 1998. Female tuatara from five northern islands showed significant differences in gravidity rate, clutch size and body size. However, none of the varia...

Introduced species of mammals have now been removed from many islands around New Zealand, thus providing singular opportunities for ecological restoration. If island restoration is to be attempted, the way island biota originate and the precise effects of introduced organisms must be identified. Plants introduced to the New Zealand archipelago may...

On Korapuki Island (Mercury Islands group, northeastern New Zealand) lizard capture frequencies increased following the removal of Pacific Rats Rattus exulans in 1986 and rabbits Oryctolagus cuniculus in 1987. This increase was dominated by diurnal Shore Skinks Oligosoma smithi. Increases in Shore Skink captures were proportionally greatest where b...

A programme to improve the conservation status if C. whitakeri is described. The programme involved eradication of introduced Pacific rats Rattus exulans from Korapuki Island (Mercury Islands, N-E New Zealand), documentation of the response of five species of resident lizards to release from the effects of rats, and transfer of 28 Whitaker's kinks...

Evidence from subfossils and from present distributions confirming range contractions and extinctions of New Zealand amphibians and reptiles is consistent with that from New Zealand landbirds, in which 40% of the fauna, including the largest species, has become extinct in the 1000 years since human arrival. The largest extant species of all higher...

An ecological collapse has precipitated pioneering conservation initiatives in New Zealand. Many terrestrial communities in t he New Zealand archipelago have been devastated by over-exploitation, introduced mammals and habitat destruction. More recently, marine ecosystems have been depleted by over-harvesting. To mitigate against these losses, cons...

We summarise the magnitude of New Zealand's species conservation problems, seek a guiding philosophy from which to approach these problems, outline several ways by which species can be treated in a conservation context, and examine various approaches to species-oriented conservation. Using definitions in the Conservation Act 1987 we derive a goal s...

Predation by kiore (Rattus exulans) has long been assumed to reduce the abundance and species diversity of lizards on islands around New Zealand. However, proof of this is hard to find, partly because it is difficult to compare lizard populations on different islands. In this paper I review methods for obtaining contemporaneous samples of lizard po...

During surveys of mayfly assemblages in streams on the northern and southern blocks, Great Barrier Island, 24 species were recorded, 20 of them Leptophlebiidae. Except for the absence of Baetidae and some Siphlonuridae, this fauna is similar in size and composition to that found in forested streams at equivalent latitudes on the mainland. No endemi...

During a survey of the herpetofauna of the northern and southern blocks, Great Barrier Island, one species of frog and 11 species of lizard were recorded. This faupa includes three species listed in the “New Zealand Red Data Book”: the frog {itLeiopelma hochstetteri}, and the skinks {itLeiolopisma homalonotum} and {itLeiolopisma striatum}. The pres...

Selected physicochemical features, litter input rates and the abundance and distribution of common invertebrates were studied in Brown Hill Creek, a small intermittent stream that flows annually for about 6 months near Adelaide, South Australia. Permanent pools had very highly coloured waters and long-term low oxygen levels in summer, apparently re...

For some species present-day distributions are relictual because of recent local extinctions, particularly on the mainland. Ecological divergence and species diversity of lizards within selected biogeographic elements are described and compared with ecological and morphological divergence found New Zealand wide. Genetic relationships of some identi...

Influences contributing to the restricted distribution and low numbers of the 3 species are outlined and each species' status and future prospects for conservation are discussed. -from Author

Nymphal life histories of six sympatric species of Leptophlebiidae (Ephemeroptera) were studied in Waitakere River and its tributary, Cascade Stream, a kauri forest stream system in northern New Zealand. Species examined were Neozephlebia scita (Walker), Austroclima jollyae Towns & Peters, Deleatidium myzobranchia Phillips, D. lillii Eaton, Deleati...

Zephlebia Penniket is redescribed and the status of subgenera previously recognised is assessed. The subgenus Neozephlebia Penniket is raised to generic rank. The only species of Neozephlebia recognised is N. scita (Walker). A new genus, Acanthophlebia, is established for Zephlebia (Zephlebia) cruentata (Hudson). Two subgenera of Zephlebia are reco...

The association between abundance of invertebrates and presence of extensive periphyton cover in the Waitakere River (36° 28′S, 174° 31′E), northern New Zealand, was studied from October 1974 to June 1975. A black polythene canopy (44 m) was placed across the stream, and the quantity of algal material and numbers of invertebrates in shaded and unsh...

Life histories of the following 12 benthic invertebrate species were investigated at four sites in the Waitakere River: Potamopyrgus antipodarum (Gastropoda : Hydrobiidae); Paracalliope fiuviatilis (Amphipoda : Eusiridae), Zephlebia (Neozephlebia) sp. and Deleatidium spp. (Ephemeroptera : Leptophlebiidae), Hydora nitida (Coleoptera : Elmidae), Maor...

The leptophlebiid mayfly fauna of New Zealand at present consists of three named genera, of which two are clearly polyphyletic. Analysis of these elements and addition of undescribed genera indicate the presence of at least 14 genera. The genera can be divided into five lineages which exhibit varying degrees of radiation within New Zealand and whic...

New genera Isothraulus, Arachnocolus, and Penniketellus are established for three species of leptophlebiid mayfly from New Zealand. Each genus is monotypic and endemic to New Zealand. Isothraulus and Arachnocolus are known only from the northern North Island, and Penniketellus is known only from the Arthur's Pass area of the central South Island. T...