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Dunedin, New Zealand

Russell J.C.,University of Auckland | Broome K.G.,Science and Policy Group
New Zealand Journal of Ecology | Year: 2016

New Zealand has just passed half a century of rodent eradications on islands. Confirmation of the first rat eradication in New Zealand on Maria Island/Ruapuke coincided with the devastating rat invasion on Big South Cape Island/Taukihepa. We review the early history of rodent management in New Zealand leading up to and including the Big South Cape Island/Taukihepa ship rat invasion, and document the development and implementation of rodent eradication technologies on New Zealand islands up to the present day. In the last decade major advances have been made in multi-species eradications including rodents, community engagement, mouse eradication, transferring techniques to mainland eco-sanctuaries, and developing new tools for rodent management. The challenge of rodent biosecurity to prevent reinvasion which loomed large only a decade ago, is now being addressed through a combination of research and robust management procedures. Increased emphasis is now being placed on documenting species and ecosystem recoveries following rodent eradication. We identify the major challenges to further expansion of rodent eradication throughout New Zealand as working with multiple stakeholders on inhabited islands, efficiencies of scale on very large islands, and the implementation of cost-effective barrier technologies on the New Zealand ‘mainland’. © New Zealand Ecological Society.

Towns D.R.,Science and Policy Group | Towns D.R.,Auckland University of Technology | Borrelle S.B.,Auckland University of Technology | Thoresen J.,Auckland University of Technology | And 2 more authors.
New Zealand Journal of Ecology | Year: 2016

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 programmes. The questions are: what is the regional context of the island (biogeography); how does each island ecosystem operate (ecosystem function); how have invasive species changed the ecosystem (response effects); and how can progress towards a restoration goal be defined (outcome measures)? Examples of how these questions influenced restoration in the Mercury Islands are provided with Korapuki Island as a case study. However, unpredicted and subtle responses can eventuate. In the Mercury Islands these included a hitherto unknown honeydew parasite-bird-gecko food web and subtle effects of rats on plant regeneration. Promising outcome measures of restoration progress are now being developed, including indices of marine influence using stable isotopes of nitrogen and the use of network analysis to analyse the composition of invertebrate food webs. © New Zealand Ecological Society.

Tansell J.,Te Anau Office | Edmonds H.K.,Southern Contractors | Robertson H.A.,Science and Policy Group
Notornis | Year: 2016

A 15,000 ha low-intensity stoat (Mustela erminea) trapping network was established in the Murchison Mountains in 2002, primarily to protect the last natural population of the critically endangered takahe (Porphyrio hochsteteri). We compared the productivity and survival of threatened southern brown kiwi or tokoeka (Apteryx australis) living in 3 valleys that were covered by this trapping network with those in a nearby valley that was left untreated. Chick survival to 6 months old was significantly higher in the trapped areas (37%) than in the untrapped area (19%). This doubling of chick survival was sufficient to change the rate of population growth, as derived from Leslie matrix analyses, from a projected decline of 1.6% per annum without management to a projected increase of 1.2% per annum with trapping. © The Ornithological Society of New Zealand Inc.

Cowan P.,Landcare Research | Booth L.,Landcare Research | Crowell M.,Science and Policy Group
New Zealand Journal of Ecology | Year: 2016

Concern about non-target risks to native birds, particularly kea (Nestor notabilis), from aerial poisoning has prompted the evaluation of potential repellent compounds that could be incorporated into the cereal pellet bait used for possum (Trichosurus vulpecula) and rat (Rattus spp.) control. Initial trials of d-pulegone and anthraquinone were not wholly successful, with the former having poor stability in bait and the latter reducing bait uptake by rats. While research to stabilise d-pulegone in bait remains an option, a review of alternative compounds was undertaken to assist with decision-making about future directions for research, including consideration of possible formulation issues and cost. Most of the information reviewed related to use of repellents for crop protection where the aim is to reduce economic loss rather than prevent feeding on the crop, whereas preventing feeding is the primary aim for native bird protection. A further constraint was the lack of information for many compounds on response of rodents and possums. Cinnamamide, tannic acid, caffeine, garlic oil, ortho-aminoacetophenone, and thiram were identified as possible candidates and evaluated in relation to their potential to repel native birds from eating cereal baits without affecting efficacy for possums and rats. Cinnamamide, caffeine, and thiram, while effective as bird repellents, are likely to be repellent to rats at concentrations suitable for use with native birds, including kea. The little information found suggested that garlic oil was repellent to birds; it has not been formally tested on possums and rats, but anecdotal evidence did not suggest strong aversion. Ortho-aminoacetophenone appears effective as a bird repellent, but its repellency for possums and rats requires clarification. Tannic acid has some efficacy as a bird repellent, and is not repellent to possums and rats at lower concentrations. It is not clear if tannic acid exerts its effect solely as a primary repellent or whether it also has secondary repellent effects. In order from most to least promising, tannic acid, ortho-aminoacetophenone, and garlic oil are worthy of further investigation. Because each compound has demonstrated some efficacy as a bird repellent, initial testing should focus on screening against possums and rats. © New Zealand Ecological Society.

Robertson H.,Science and Policy Group
New Zealand Journal of Zoology | Year: 2016

Many mainland populations of kiwi are declining because stoats (Mustela erminea) kill most of their chicks. Stoats are often trapped during conservation programmes, but the long-term effectiveness of trapping has not been measured. During continuous trapping of mammalian predators in the 9800 ha Whangarei Kiwi Sanctuary, the survival of brown kiwi (Apteryx mantelli) chicks declined over time. Following the use of sodium fluoroacetate (1080) to kill rats (Rattus spp.) and possums (Trichosurus vulpecula) and likely secondary poisoning of stoats, chick survival at Riponui increased from 5% to 56%, and the 62% chick survival at Rarewarewa was better than the 20% recorded in a trapped-only area nearby. We suggest that untrappable stoats accumulate in areas subjected to continuous predator trapping. Conservation managers should build into their long-term pest control programmes a periodic pulse of an alternative tool to kill pests that, for whatever reason, actively avoid the primary control tool. © 2016 The Royal Society of New Zealand

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