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Archipelago-wide island restoration in the Galapagos Islands: Reducing costs of invaisve mammal eradication programs and reinvasion risk

Available Online

Campbell, Karl J.

Carrion, Victor

Cruz, Felipe

Donian, C. Josh

Lavoie, Christian

Invasive alien mammals are the major driver of biodiversity loss and ecosystem degradation on islands. Over the past three decades, invasive mammal eradication from islands has become one of society's most powerful tools for preventing extinction of insular endemics and restoring insular ecosystems. As practitioners tackle larger islands for restoration, three factors will heavily influence success and outcomes: the degree of local support, the ability to mitigate for non-target impacts, and the ability to eradicate non-native species more cost-effectively. Investments in removing invasive species, however, must be weighed against the risk of reintroduction. One way to reduce reintroduction risks is to eradicate the target invasive species from an entire archipelago, and thus eliminate readily available sources. We illustrate the costs and benefits of this approach with the efforts to remove invasive goats from the Galápagos Islands. Project Isabela, the world's largest island restoration effort to date, removed > 140,000 goats from > 500,000 ha for a cost of US$10.5 million. Leveraging the capacity built during Project Isabela, and given that goat reintroductions have been common over the past decade, we implemented an archipelago-wide goat eradication strategy. Feral goats remain on three islands in the archipelago, and removal efforts are underway. Efforts on the Galápagos Islands demonstrate that for some species, island size is no longer the limiting factor with respect to eradication. Rather, bureaucratic processes, financing, political will, and stakeholder approval appear to be the new challenges. Eradication efforts have delivered a suite of biodiversity benefits that are in the process of revealing themselves. The costs of rectifying intentional reintroductions are high in terms of financial and human resources. Reducing the archipelago-wide goat density to low levels is a technical approach to reducing reintroduction risk in the short-term, and is being complemented with a longer-term social approach focused on education and governance.

The legacy of Big South Cape: rat irruption to rat eradication

Available Online

Bell, Brian D.

Bell, Elizabeth A.

Merton, Don V.

Big South Cape Island (Taukihepa) is a 1040 ha island, 1.5 km from the southwest coast of Stewart Island/Rakiura, New Zealand. This island was rat-free until the incursion of ship rats (Rattus rattus) in, or shortly before, 1963, suspected to have been accidentally introduced via local fishing boats that moored at the island with ropes to the shore, and were used to transport the mutton birders to the island. This incursion was reported by the muttonbirders local Iwi who harvest the young of titi (sooty shearwater, Puffinus riseus) to the then New Zealand Wildlife Service (via the New Zealand Department of Lands and Survey). Investigation into the reports found ship rats had reached the island and had decimated the local land bird populations. Brian Bell and Don Merton attempted some of the first translocations of South Island saddleback (Philesturnus c. carunculatus), Stewart Island snipe (Coenocorypha aucklandica iredalei) and Steads bush wren (Xenicus longipes variabilis) with only the saddleback being successful. Extinctions of the snipe, wren and greater short-tailed bat (Mystacina robusta) were recorded. This was the first time rats were definitively recognised as the cause of extinction of native land birds and directed further debate into the impacts of rats and how to deal with them.

Christmas Island National Park - Idependent scientific research shows that crazy ant bait does not acccumulate in Christmas Island's environment

Available Online

Cites independent study by CESAR Consultants confirms that Fipronil ant bait has not accumulated in the envrionment on Christmas Island for the control of yellow crazy ant.

Land vertebrates as invasive species on the islands of the South Pacific Regional Environment Programme.

Atkinson, I A E

Atkinson, T J

This review of the invasive land vertebrates present on islands of the South Pacific Regional Environment Programme (SPREP) region is part of a larger review of the invasive plants and animals that have affected these islands adversely.

From small Maria to massive Campbell: forty years of rat eradications from New Zealand islands

Available Online

Broome, Keith G

Towns, David R

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 (Feliscatus) on large islands.

Costs and benefits of rodent eradication on Lord Howe Island Australia

Island and Ocean Ecosystems, BRB

Available Online

Bennett, Jeff

Gillespie, Robert

Invasive species compete with endemic species and if successful can displace native species in the host region (Cororaton et al., 2009).

Prognosis for ecosystem recovery following rodent eradication and seabird restoration in an island archipelago.

Available Online

Holly P. JonES

Invasive species are widespread and can have devastating effects on biota, especially insular biota. Invasive species eradications are increasingly employed to promote island recovery to preinvasion states. However, it remains unclear if additional restoration actions may be required on islands that were once heavily reliant on seabird guano for ecosystem functions. Active seabird augmentation has been suggested as necessary to exact ecosystem recovery on contemporary timescales in some cases. I use two experiments on offshore islands in Cook Strait, New Zealand, to test the hypothesis that seabird restoration will restore island ecosystem functioning following invasive rodent removal. The first is a small-scale single-island fertilization experiment that simulates seabird recovery.

Report on results of rat control trials in the Tokelau Islands from 30 July to 20 September 1970 and recommendations for a comprehensive scheme of rat control

Available Online

Kazimierz Wodzicki

The visit to the Tokelau Islands described below is the third carried out in a study of ecology, rat control and related problems. The first visit in 1966/67 (Wodzicki 1968 A) was devoted primarily to the study of the ecology of the Polynesian rat (Rattus exulans) and the environment, including the animals and the vegetation, of Nukunonu atoll. The main objects of the second expedition in April-June 1968 (Wodzicki 1968 B) were the initiation of a long-term investigation of rat damage on all three atolls and the training of two men from each island as rat control operatives. The present visit was planned with the following tow main objectives in mind: 1. the study of the relationship of rat damage to various coconut varieties growing in the Tokelau Islands; and 2. the conduct of rat control trials with the view of preparing for the Administrator, Tokelau Islands (Mr. Richard B. Taylor) recommendations for a rat control scheme suitable for the Tokelau Islands. The preliminary analysis of data collected during the fifteen months long investigation of rat damage in 1968/69 on the three atolls suggested that palms belonging to some varieties may be more prone to rat damage then others (Wodzicki 1970). It seemed important that we learn more about the character of palms growing on the three atolls. With regard to rat control, trials with various kinds of poisons have been carried out since our first visit to the Tokelaus in 1966/67 (Wodzicki 1968 A). However, during our first two visits knowledge of rat ecology was not sufficiently advanced to allow for more sophisticated tests. Since the author's 1968 visit, the important work on rat control in the Gilbert and Ellice Islands by F.J. Smith (Smith 1969) has become available. This information and our knowledge of rat ecology, gradually acquired since the beginning of the Tokelau Islands rat project, now makes possible a programme that could become the basis of a practical rat control scheme for the three islands. As most of the previous work had been carried out on Nukunonu atoll only, it was felt that half of the time during the visit should be spent on Fakaofo and th remainder on Atafu. Following a brief descrption of these trials is the writer's recommendation of a rat control scheme submitted to the Administrator, Tokelau Islands. Finally, some other observations on plants, animals and related aspects are friefly reported and collections made for the Botany Division, D.S.I.R. and the Dominion Museum are briefly mentioned.

Improving the breeding success of a colonial seabird: a cost-benefit comparison of the eradication and control of its rat predator

Available Online

Bretagnolle, Vincent.

Culioli, Jean-Michel.

Lorvelec, Olivier.

Pascal, Michel Pascal.

Breeding success of 5 Corys shearwater Calonectris diomedea sub-colonies of Lavezzu Island (Lavezzi Archipelago, Corsica) was checked annually for 25 consecutive years from 1979 to 2004. Between 1989 and 1994, 4 ship rat Rattus rattus controls were performed in several subcolonies. In November 2000, rats were eradicated from Lavezzu Island and its 16 peripheral islets (85 ha) using traps then toxic baits. We compare cost (number of person-hours required in the field) and benefit (Corys shearwater breeding success) of control and eradication. The average breeding success doubled when rats were controlled or eradicated (0.82) compared to the situation without rat management (0.45). Moreover, the average breeding success after eradication (0.86) was significantly (11%) higher than after rat controls (0.75). Furthermore, the great variation in breeding success recorded among sub-colonies both with and without rat control declined dramatically after eradication, suggesting that rats had a major impact on breeding success. The estimated effort needed to perform eradication and checking of the permanent bait-station system during the year following eradication was 1360 person-hours. In contrast, rat control was estimated to require 240 or 1440 person-hours per year when implemented by trained and untrained staff, respectively. Within 6 yr, eradication cost is lower than control cost performed by untrained staff and confers several ecological advantages on more ecosystem components than Corys shearwater alone. Improved eradication tools such as hand or aerial broadcasting of toxic baits instead of the fairly labour-intensive eradication strategy we used would dramatically increase the economic advantage of eradication vs. control. Therefore, when feasible, we recommend eradication rather than control of non-native rat populations. Nevertheless, control remains a useful management tool when eradication is not practicable.

The Rangitoto and Motutapu pest eradication - a feasibility study.

Available Online

Griffiths, Richard.

Towns, David.

The eradication of the seven remaining animal pest species remaining on Rangitoto and Motutapu was announced by the Prime Minister and Minister of Conservation in June 2006. With stoats, cats, hedgehogs, rabbits, mice and two species of rats spread across an area of 3842ha, the proposed project is the most challenging and complex island pest eradication the Department of Conservation (DOC) has ever attempted. To better understand the scale and complexity of the project, a feasibility study was undertaken. This study considered the ecological, economic and social context of the project to allow an informed decision to be made on whether or not to commit resources to further eradication planning. This document outlines the findings of the feasibility study and concludes that while a number of contingencies exist within the project, the proposed eradication is not only feasible, but has many significant benefits. No single precedent exists on which this project can be modelled and information from a wide range of sources has been required. Previous eradication and control programmes have been reviewed in conjunction with what is known about the behaviour and biology of the target species. In some cases, where information has not been available and could not be inferred, trials have been undertaken. The document has been reviewed by a number of experts both within New Zealand and overseas including DOCs Island Eradication Advisory Group. Consultation has also been undertaken with all of the islands key stakeholders and communities of interest. Comments from all of these parties have been reflected in the report. Rangitoto is an iconic Scenic Reserve located just 9km from downtown Auckland City. The island is internationally significant both for its ecology and geology and is an extremely popular visitor destination served by regular ferry services. Motutapu, a Recreation Reserve, is connected to and positioned immediately to the east of Rangitoto. The island, currently managed as a pastoral farm, is noted for its extensive archaeological record but retains a diverse range of habitat types and is the focus of a community-led restoration programme. In addressing the question, can it be done? particular attention has been paid to mice, ship rats, hedgehogs and rabbits as eradication of these species on the scale of Rangitoto and Motutapu has never been attempted. Preventing reinvasion on such highly accessible and intensively visited islands is also an enormous undertaking. It is accepted, that of all the target species, mice present the greatest risk of failure. However, while a number of mouse eradications around the world have failed, all ten attempts on islands beyond the swimming range of mice that have followed current Departmental best practice have been successful, providing confidence in the method. Rangitoto and Motutapu are a significant step up from previous operations in terms of scale but are also the logical next step to apply current techniques. Despite the unprecedented elements within the project, it is considered that the key dependencies on which eradication success relies can be met for the species targeted. Preventing reinvasion is perhaps the most important consideration of the feasibility study and the one that will ultimately determine the fate of the project. Achieving an adequate level of protection for the islands hinges heavily on changing the behaviour of all 100,000 visitors that arrive on an annual basis. Without this any investments made in removing pests will be wasted. Bringing these changes about appears possible but is contingent on a number of commitments and actions that must be put in place by both DOC and its key partners. The feasibility study also addresses what the project will take to complete and attempts to identify as many of the planning issues as possible to enable the project to be properly sized. It explores the techniques that must be used, the resources that will be required and the timeframe over which they need to be deployed. While this eradication project is the most challenging and complex to be undertaken by DOC, it also presents a significant opportunity to improve our current understanding of eradication theory and practice. If successful, the project offers outstanding benefits for conservation. The recovery of locally and nationally endangered species, the creation of a stepping stone for wildlife movement between the Hauraki Gulf and the Auckland isthmus, the potential for advocacy and education, and increased recreation and economic opportunities are just some of the likely gains. The study has shown that this project is feasible, but also that there are many significant reasons why it should proceed.

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