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The Pacific is biologically unique, as its isolated islands provide ideal conditions for the evolution of new species. Thus, Pacific islands have high numbers of "endemic"species - species that are restricted to only one or a few islands and found nowhere else in the world.

This article is a study on the dietary shift of black rats on Surprise Island, New Caledonia and their impact on the ecosystem in the presence and absence of breeding seabirds.

Breeding success of 5 Cory’s 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 (Cory’s 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 Cory’s 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 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 DOC’s 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.

It is widely recognized that trophic interactions structure ecological communities, but their effects are usually only demonstrated on a small scale. As a result, landscape-level documentations of trophic cascades that alter entire communities are scarce. Islands invaded by animals provide natural experiment opportunities both to measure general trophic effects across large spatial scales and to etermine the trophic roles of invasive species within native ecosystems. Studies addressing the trophic interactions of invasive species most often focus on their direct effects. To investigate both the presence of a landscape-level trophic cascade and the direct and indirect effects of an invasive species, we examined the impacts of Norway rats (Rattus norvegicus) introduced to the Aleutian Islands on marine bird densities and marine rocky intertidal community structures through surveys conducted on invaded and rat-free islands throughout the entire 1,900-km archipelago. Densities of birds that forage in the intertidal were higher on islands without rats. Marine intertidal invertebrates were more abundant on islands with rats, whereas fleshy algal cover was reduced. Our results demonstrate that invasive rats directly reduce bird densities through predation and significantly affect invertebrate and marine algal abundance in the rocky intertidal indirectly via a cross-community trophic cascade, unexpectedly changing the intertidal community structure from an algae- to an invertebrate-dominated system.

Invasive mammal eradications are a proven, effective method of restoring damaged ecosystems and preserving biodiversity. On most tropical oceanic islands indigenous land crabs compete with targeted alien species for bait and interfere with traps and detection devices. Current eradication practices are inherited from successful termperate or subantarctic campaigns, yet we do not possess trued and tried methods for managing land crab interference. This report is the first organized attempt to address what's now commonly referred to as "the land crab problem." Accounts of land crab interference with eradication projects were sourced from an array of eradication practitioners; the resulting information was sorted into major topics and presented in tables, figures, and text. Major topics include: bait application rates, land crab and rat bait consumption, land crab behaviour, land crab interference with bait-stations, land crab deterring bait masks, and toxin exposure risk for non-target species. The summarized information in this report will guide future investigations into the land crab problem.

In 1989, the kakerori (Pomarea dimidiata) was one of the 10 rarest birds in the world with a declining population of just 29 individuals living in forested hill country in the Takitumu Conservation Area (TCA) of south-eastern Rarotonga, Cook Islands. Following 12 years of rat poisoning, the population had increased to 255 birds in August 2001. The programme then shifted from ‘species recovery’ to ‘sustainable management’ of the Rarotonga population at 250 to 300 birds. The rat poisoning effort was reduced, and an ‘insurance’ population was established on Atiu. By August 2004, following the reduction of poisoning from weekly to fortnightly, and the transfer of 30 youngsters to Atiu in 2001–03, there were 281 birds on Rarotonga and 25 on Atiu. The southern Cook Islands were hit by five tropical cyclones in a four-week period in February–March 2005, and forests on Rarotonga were severely damaged. Kakerori survived the storms remarkably well, but the main effect was observed in the following breeding season (2005/06), when nesting success on Rarotonga was exceptionally poor. Reduced canopy cover caused nests to be exposed to abnormally wet conditions, and lack of fruit meant that rats were exceptionally hungry. Only 31 yearlings were known to be alive in August 2006—about half the expected number—and annual mortality of banded birds (25%) was the highest since management began. The kakerori population on Rarotonga fell 8% from 275 birds in August 2005 to a minimum of 254 birds in August 2006. The situation was better on Atiu, with the population growing from about 32 adult birds in 2005/06 to a minimum of 37 adult birds in 2006/07, and an Atiu-bred pair nested successfully for the first time. The 2006/07 breeding season on Rarotonga was moderately successful, with a minimum of 51 fledglings found. Because the ‘sustainable management’ regime of fortnightly rat poisoning in the TCA was only just adequate in giving protection to adult kakerori, the annual poisoning programme was modified by adding rounds of ‘interim’ poisoning in April and July 2007 aimed at reducing rat and cat numbers before the breeding season.

The study of dispersal processes of small mammals, and especially of rodents, has a wide range of applications and until recent years there were few publications discussing the colonisation of 'oceanic' islands by small mammals (cf. Crowell, 1986; Diamond, 1987; Hanski, 1986;Heany, 1986; Lomolino, 1986). This essay will be concerned with the distribution of rat species in the Marshall Islands and its implications on the interpretation of the settlement and human use of the atolls. It will be argued that in all instances the introduction of rats was caused by people and that accidental transport, such as rafting on drift wood and the like, is as unlikely as introduction by means of ship wrecks. Human transport as well as the rats' own inability to cross great distances of water makes them bad zoogeographical markers, as already pointed out by Braestrup (1956), but it is precisely this trait that is of concern here. This paper will argue that the Polynesian rat (Rattus exulans) was an intentional introduction to the area and that its distribution throughout the Marshall Islands was a deliberate strategy.

Rat control guidelines