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         Management Information

    Preventative measures: Research has shown that it can often be difficult to eradicate rats from islands in the early stages of invasion, hence it is better to prevent rodents arriving on islands in the first place. Eliminating a single invading rat can be disproportionately difficult because of atypical behaviour by the rat in the absence of conspecifics, and because bait can be less effective in the absence of competition for food (Russell et al. 2005). Weihong et al. (1999) provide useful information regarding the detection of rodent species using different trapping methods and bait, Dilks and Towns (2002) published by New Zealand’s Department of Conservation discusses how to detect and respond to rodent invasions on islands.

    Physical: Control on mainland sites predominantly consists of snap-trapping.

    Chemical: Over the last fifteen years, Pacific rats (Rattus exulans) have been eradicated from increasingly larger New Zealand offshore islands. To date, the largest eradication has been from Raoul Island (2938 ha), although confirmation of eradication from the larger Little Barrier Island (3083 ha) is due this year. Eradication of R. exulans populations on islands is achieved using chemical poisons. In New Zealand compound 1080 has not proved effective against R. exulans, but they are susceptible to anticoagulant poisons such as brodifacoum and bromadialone. Recent successful eradication campaigns have all sown Talon 20 P baits aerially by helicopter. Talon 20 P is a cereal-based (pollard) pellet of approximately 0.8 g containing the anticoagulant toxin brodifacoum at 20 ppm. Currently this is applied at 15kg/ha at a cost of ~$75US/ha (Atkinson and Towns 2001).

    Fisher et al. (2004) suggest that diphacinone especially, and also coumatetralyl and warfarin, should be evaluated in field studies as alternative rodenticides in New Zealand. Brodifacoum, the most widely used rodenticide in New Zealand currently, can acquire persistent residues in non-target wildlife. Mineau et al. (2004) presented a risk assessment of second generation rodenticides at the 2nd National Invasive Rodent Summit. O'Connor and Eason (2000) discusses the variety of baits which are available for use on offshore islands in New Zealand.

    Biological: Monitor lizards and mongooses were introduced to Pacific islands in early attempts to control R. exulans.
    Contraceptive methods of control are currently experimental, but the potential for effective control using contraceptive methods is promising. National Wildlife Research Center (USA) scientists are working on several possible formulations that may make effective oral immunisation possible (Nash and Miller, 2004).

    Guidelines for the Eradication of Rats From Islands Within the Falklands Group offers guidelines for the eradication of rats from islands, based on the experiences in eradicating rats from the Falklands group. français   



         Location Specific Management Information
    Ahnd (Ant) Atoll
    A proposal has been made by the Conservation Society of Pohnpei (CSP) to eradicate rats from Ahnd Atoll.
    Anchorage Is. (Cook Islands) (Suwarrow (Suvarov) Atoll)
    A Pacific rat (Rattus exulans) eradication programme was conducted in 2003 by Pacific Expeditions Ltd. Bait stations were used almost everywhere, except where the undergrowth was impenetrable, when the bait was hand broadcast. Two applications of brodifacoum (20ppm) were carried out, five days apart, at a rate of 5kg/ha each application. On a return visit in July 2007, Graham Wragg confirmed with John Samuels (the warden) who had been living there for the previous 3 months, that rats were no longer present on Anchorage Island (G. Wragg, pers. comm.).
    Arch Is. (North Island)
    The Pacific rat (Rattus exulans) was eradicated from Arch Rock in the Mokohinau Islands between 1990 and 1991, using bromadiolone (McFadden, 1992).
    Atihau (Trig) Is. (North Island)
    Pacific rats (Rattus exulans) were eradicated from Atihau Island by the Department of Conservation between 1990 and 1991, using bromadiolone (McFadden, 1992b; 1994).
    Bench Is.
    A rat eradication operation commenced on Bench Island (121 ha) in 2005.
    Burgess Is. (North Island)
    The Pacific rat (Rattus exulans) was eradicated from Burgess Island in the Mokohinau Islands by the Department of Conservation between 1990 and 1991, using brodifacoum (McFadden, 1992; 1994).
    Centre (Rarotoka) Is.
    The Pacific rat (Rattus exulans) was eradicated from Rarotoka (Centre) Island between 1997 and 1999, in a programme undertaken by the Department of Conservation (led by P. McClelland). The eradication was achieved with a single aerial application of brodifacoum (Talon 20P). A subsequent trapping programme caught no rats, and in 1999 Pacific rats were declared eradicated. Since then, invertebrate numbers have appeared to be increasing. The recovery of vegetation is slow due to the many years of grazing by cattle and sheep (McClelland, 2002). Rarotoka is uninhabited and relatively easy to access, making it a quarantine risk. The island owners will manage this risk, with advice from DoC (McClelland, 2002).
    Codfish Is.
    The eradication of Pacific rats from Codfish Island was preceded by a number of trials beginning in 1992 on bait and toxin weathering, non-target species risks and ways of minimising these risks. It was found that the Codfish Island fernbird (Bowdleria punctata wilsoni) would be at risk, and a second population was transferred to nearby Putauhinu Island prior to the eradication. The eradication was carried out in August 1998 using two aerial bait drops of brodifacoum (20ppm) (Island Conservation and Ecology Group, 2004). Bait was dropped over the entire island with the exception of the core fernbird area, although the perimeter of this area was double swathed. The interior of the fernbird area was laid out with bait stations. All known kakapo (see Strigops habroptilus in IUCN Red List of Threatened Species ) were transferred off the island during the operation, and short-tailed bats (see Mystacina tuberculata in IUCN Red List of Threatened Species) were held in captivity. In March 2000 a trapping programme caught no rats, and Pacific rats were declared eradicated in December 2000. There have been several possible, although unlikely, sightings of rats on Codfish Island since, but follow-up trapping has not caught any rats. Despite the efforts to protect fernbird, it seems likely that the majority were killed in the poison operation, although the population is rebuilding. The vegetation is recovering, and invertebrate, bird and lizard species appear to be increasing. Quarantine restrictions must be strictly enforced to prevent reinvasion. Following eradication, the survival rate of Cook's petrel (see Pterodroma cookii in IUCN Red List of Threatened Species) chicks increased from 15% to 85% (DoC, 2004b).
    Coppermine Is. (Chicken Islands)
    The Pacific rat (Rattus exulans) was eradicated from Coppermine Island in 1997, after an aerial operation (McFadden, 1997). An attempt was made to eradicate Pacific rats from Coppermine Island (80 ha) in 1992, using brodifacoum bait stations placed on a 100 m grid (McFadden, pers. comm.). This operation failed, although it was unclear if the failure was due to the wider spacing of bait stations or the rugged topography of the island.

    A study (Pierce, 2002) was carried out after the eradication of the Pacific rats, to test the following hypotheses: (1) Breeding success of the two seabird species (Pycroft’s petrel (see Pterodroma pycrofti in IUCN Red List of Threatened Species) and the winter-nesting little shearwater Puffinus assimilis haurakiensis (see Puffinus assimilis in IUCN Red List of Threatened Species) is not limited by Pacific rats presence, (2) breeding success is not limited by the presence of tuatara (see Sphenodon punctatus in IUCN Red List of Threatened Species) an endemic predatory reptile, (3) and the two seabird species are not in competition with each other. The study found that the breeding success was significantly lower when the study islands contained Pacific rats: little shearwaters averaged a 16% breeding success in the presence of Pacific rats and 61% in the absence of Pacific rats, while Pycroft’s petrels averaged a 33% breeding success in the presence of Pacific rats and 57% in the absence of Pacific rats (Thomas and Taylor, 2002).

    Cuvier Is.
    The Pacific rat (Rattus exulans) was eradicated from Cuvier Island between 1993 and 1995, in a programme led by P. Thomson (Towns et al. 1995; Veitch, pers. comm.)
    Double (Moturehu) Is. (Mercury Islands)
    Trials were carried out on Double Island to test the effectiveness of bromadiolone-impregnated grain in silo bait stations on one half of the island with hand distributed Storm rodent pellets on the other half for the eradication of Pacific rats. Both achieved eradication, although the cost of hand broadcasting baits was slightly cheaper.
    Double Is. (Western Australian) (Western Australian Islands)
    The Pacific rat (Rattus exulans) was eradicated from Double Island in 1989 by the Department of Conservation (led by I. McFadden) (McFadden, 1992; Veitch and Bell, 1990). Trials were carried out on Double Island to test the effectiveness of bromadiolone-impregnated grain in silo bait stations on one half of the island with hand distributed Storm rodent pellets on the other half for the eradication of Pacific rats. Both achieved eradication, although the cost of hand broadcasting baits was slightly cheaper (Thomas and Taylor, 2002).
    Ducie Is.
    The Pacific rat (Rattus exulans) was eradicated from Ducie Island in 1997, in a programme undertaken by Wildlife Management International Ltd (led by Brian Bell). The method used was hand broadcast of brodifacoum (20 ppm) (B. Simmons, G. Wragg, pers. comm.).
    Dulcie Is.
    Rats were successfully eradicated from Ducie and Oeno in 1997 (Brooke, 1998 in Varnham, 2006). Action being considered/required includes total eradication from Pitcairn, and to keep Ducie and Oeno rat-free (Brooke, 1998 in Varnham, 2006; Brooke and Trevelyan, 2003 in Varnham, 2006) and eradication from Henderson (Hilton, 2004 in Varnham, 2006).
    East (Whangaokena) Is.
    Restoration of Whangaokena (East Island) is taking place as a cooperative effort between the Department of Conservation and tangata whenua Rattus exulans was eradicated from East/Whangaokena Island (13 ha) in 1997. The eradication attempt was led by D. Peters (McFadden, pers. comm.; D. Veitch, pers. comm.; Atkinson and Taylor, 1991; Bassett, 1999; J. Russell, pers. comm.). Anecdotal reports indicate that since eradication, vegetation has improved and insect numbers have increased (He Atinga, 1998).
    Eniwetok/Enewetak Is.
    Pacific rats may have been exterminated by the thermo-nuclear explosions. Extensive trapping on the islet shows that only R. rattus is now present (Jackson 1969 in SPREP, 2000).
    Fanal (Motukino) Is. (North Island)
    An eradication attempt was made in August 1997, using an aerial drop of Talon 7-20, containing brodifacoum and bitrex (a bittering agent). The programme was undertaken by the Department of Conservation (led by C.R. Veitch) (Veitch, 2002; D. Veitch, pers. comm.; J. Russell, pers. comm.; in Island Conservation and Ecology Group, 2004). Follow-up visits were made in 1998, 1999 and 2000, and no sign of rats was detected. The eradication appears to have been successful, despite heavy rainfall occurring shortly after the aerial drop, and the presence of bitrex in the bait (bitrex has been shown to reduce consumption of baits by Pacific rats in captive trials).
    Flax Is. (North Island)
    Pacific rats (Rattus exulans) were eradicated from Flax Island (Hokoromea) between 1990 and 1991, in a programme undertaken by the Department of Conservation (led by I. McFadden), using brodifacoum (McFadden, 1992; 1994; D. Veitch, pers. comm.; J. Russell, pers. comm.).
    Haszard Islet (Kermadec Islands)
    Greene et al. (2004) recommend that Pacific rats should be eradicated from Haszard Islet and Macauley Island as soon as possible.
    Hawaii
    Management in sugarcane fields:
    Cultural Methods: Advancing harvest from the usual 22 to 24-month schedule would reduce losses. Adoption of a shorter crop cycle, however, would increase planting and harvesting costs and probably would not be feasible considering current economic conditions. Synchronized planting and harvesting of adjacent fields might reduce movements of rats from recently harvested fields into younger fields. Modification or elimination of noncrop vegetation adjacent to sugarcane fields would help reduce invasion from surrounding areas. Cattle grazing or commercial production of trees for energy or timber might reduce the vegetative understory in such areas. Herbicide use probably is not economical or environmentally desirable. Development of sugarcane varieties that are less susceptible to damage by rats is a promising avenue for research.
    Toxicants: Zinc phosphide is the only toxicant registered in the United States for rat control in sugarcane. Baits are formulated either as pellets or on oats and usually are broadcast by fixed-wing aircraft at the rate of 5 pounds per acre (5.6 kg/ha). A maximum of four applications and 20 pounds per acre (22.4 kg/ha) may be applied per crop cycle. Zinc phosphide baits in Hawaii are most effective against Pacific rats and least effective against Norway rats. Because the relative abundances of the two species vary substantially from field to field and may shift as the crop matures, the efficacy of zinc phos-phide baits also varies. Where Norway rat populations increase during the second year of the crop cycle, zinc phosphide baits become progressively less effective.
    Henderson Is.
    Henderson Management Plan suggests research to identify the level of rat predation on the island's seabirds (Brooke et al., 2004 in Varnham, 2006). Action being considered/required includes total eradication from Pitcairn, and to keep Ducie and Oeno rat-free (Brooke, 1998 in Varnham, 2006; Brooke and Trevelyan, 2003 in Varnham, 2006) and eradication from Henderson (Hilton, 2004 in Varnham, 2006).
    Ifaluk Atoll
    The Japanese introduced monitor lizards to help control rats, but they may not have established.
    Kapiti Is.
    The Pacific rat (Rattus exulans) was eradicated from Kapiti Island in 1996, following an aerial application of brodifacoum (Empson et al. 1989; Empson and Miskelly, 1999). By 2001 at least four bird species had increased since eradication. Weka (see Gallirallus australis in IUCN Red List of Threatened Species) were adversely affected by the rat poisoning operation, but recovered to pre-eradication levels by 1999. Non-toxic bait trials revealed that Pacific rats would not use bait stations that Norway rats had used (Cromarty, 2002).
    Korapuki Is. (Mercury Islands)
    The Pacific rat (Rattus exulans) was eradicated from Korapuki Island between 1986 and 1987, in a programme undertaken by the Department of Conservation (led by I. McFadden). The eradication was achieved using brodifacoum (Veitch and Bell, 1990; McFadden and Towns, 1991; J. Russell, pers. comm.). Since then, vegetation has recovered, and the gecko and skink population has expanded significantly (Towns, 2002). Nine previously unreported invertebrate species also appeared (six of which are flightless) (Atkinson and Towns, 2001).
    Kure Atoll
    An eradication attempt was made to remove Rattus exulans from Kure Atoll in 1993, using traps and either brodifacoum or bromethalin (Island Conservation and Ecology Group, 2004). The programme was a joint effort between DLNR and the US Department of Agriculture. Since the eradication there had been a marked increase in the numbers of Christmas shearwaters, Bonin petrels, wedge-tailed shearwaters and red-tailed tropic birds (Wilhelm, 2000).
    Little Barrier (Hauturu) Is. (North Island)
    An eradication programme to remove the Pacific rat (Rattus exulans) from Hauturu (Little Barrier) Island was undertaken in 2004 by the Department of Conservation (led by R. Griffiths), using an aerial application of brodifacoum. Non-target species included some passerines and scavenger species. There is a two-year laydown period before eradication can be declared. Department of Conservation Island Biosecurity SOP is maintained to prevent reinvasion of the island (J. Russell, pers. comm.).

    In June 2006, Little Barrier Island in the Hauraki Gulf was declared rat free. This follows a two-year pest eradication programme by the Department of Conservation and means endangered species will now have a fighting chance of survival there. It is hoped the same success will also be experienced on the island's of Motutapu and Rangitoto where more than NZD 500,000 has been allocated for similar pest eradication programmes. The New Zealand Department of Conservation's Island Biodiversity Manager, Richard Griffiths, says having no rats on Little Barrier island is already making a big difference, with 90% of Cook's petrel (see Pterodroma cookii in IUCN Red List of Threatened Species) now producing chicks. Griffiths, says tuatara (see Sphenodon punctatus in IUCN Red List of Threatened Species), currently held in cages on the island, will be released into the wild at the end of the year (TVNZ, 2006).

    Lizard Is. (North Island)
    An attempt to remove Pacific rats (Rattus exulans) from Lizard Island was carried out in 1978 by the Department of Conservation, led by C.R. Veitch. The attempt used bromadiolone (McCallum, 1986; J. Russell, pers. comm.).
    Long Is. (NZ)
    Rattus exulans was eradicated from Long Island (142 ha) between 1997 and 2000, using brodifacoum (B. Cash, pers. comm.; B. Simmons, pers. comm.; D. Veitch, pers. comm.).
    Macauley Is. (Kermadec Islands)
    Greene et al. (2004) view the eradication of Pacific rats from Macauley Island to be essential to the ecological recovery of the island, despite the risk to the large population of Kermadec red-crowned parakeets Cyanoramphus novaezelandiae cyanurus (see Cyanoramphus novaezelandiae in IUCN Red List of Threatened Species) . Any eradication attempt should be timed to coincide with the period of least risk to the parakeet population (late autumn to winter). An eradication attempt was made in 2005, but the outcome is not yet known (M. Ambrose, pers. Comm.).
    Makapu Is. (Gambier Islands)
    An attempt to eradicate the Pacific rat (Rattus exulans) from Makapu Island was carried out in 2003, in a programme undertaken by Pacific Expeditions Ltd (led by G. Wragg). The eradication attempt used two hand broadcast applications of brodifacoum (20ppm, 2kg/ha), five days apart. Goats were identified as a non-target species, but were not affected by the programme (G. Wragg, pers. comm.). Eradication has not yet been confirmed.
    Maori Bay
    The Pacific rat (Rattus exulans) was eradicated from Maori Bay (11 ha) between 1990 and 1991, in a programme undertaken by the Department of Conservation (led by I. McFadden). The eradication was achieved using brodifacoum (McFadden, 1992; 1994; D. Veitch, pers. comm.; J. Russell, pers. comm.).
    Marotiri (Lady Alice) Is. (Chicken Islands)
    The Pacific rat (Rattus exulans) was eradicated from Marotiri (Lady Alice) Island between 1994 and 1996, using brodifacoum (I. McFadden, pers. comm.). Trials were carried out on Marotiri (Lady Alice) Is. to develop and test bait stations, dispensing silos and forms of bait and attractants (Thomas and Taylor, 2002). A study (Pierce, 2002) was carried out after the eradication of the Pacific rats, to test the following hypotheses: (1) Breeding success of the two seabird species Pycroft’s petrel (see Pterodroma pycrofti in IUCN Red List of Threatened Species) and the winter-nesting little shearwater Puffinus assimilis haurakiensis (see Puffinus assimilis in IUCN Red List of Threatened Species) is not limited by Pacific rats presence, (2) breeding success is not limited by the presence of tuatara (see Sphenodon punctatus in IUCN Red List of Threatened Species) an endemic predatory reptile, (3) and the two seabird species are not in competition with each other. The study found that the breeding success was significantly lower when the study islands contained Pacific rats: little shearwaters averaged a 16% breeding success in the presence of Pacific rats and 61% in the absence of Pacific rats, while Pycroft’s petrels averaged a 33% breeding success in the presence of Pacific rats and 57% in the absence of Pacific rats.Count data from Lady Alice Island from 1992 to 2000 indicate that this population decline has been halted and apparently reversed (Thomas and Taylor, 2002). Increases in ground weta (Hemiandrus sp.) and darkling beetles (Mimopeus opaculus) numbers have been observed following Pacific rat eradication (Atkinson and Towns, 2001).
    Marshall Islands
    Varanus indicus was released to prey upon the rats. According to local Marshallese, they also preyed on chickens as well as other birdlife (Spennemann, 1997).
    Mauipae
    An eradication attempt was made on Mauipae in 1992, but was stopped before eradication could be completed.
    Mayor (Tuhua) Is.
    The Pacific rat (Rattus exulans) was eradicated from Mayor Island (Tuhua, 1277 ha) in 2000. The eradication was achieved using an aerial application of brodifacoum (Williams et al. 2002; www.pestoff.co.nz; D. Veitch, pers. comm.).
    Mekiro Is. (Gambier Islands)
    An attempt to eradicate Rattus exulans from Mekiro Island was carried out in 2003, in a programme undertaken by Pacific Expeditions Ltd (led by G. Wragg). The eradication attempt used two hand broadcast applications of brodifacoum (20ppm, 2kg/ha), five days apart. Goats were identified as a non-target species, but were not affected by the programme (G. Wragg, pers. comm.). Eradication has not yet been confirmed.
    Middle Chain Is. (Alderman Islands)
    The Pacific rat (Rattus exulans) was eradicated from Middle Chain between 1992 and 1994, in a programme led by R. Thorpe (Thorpe, 1997; D. Veitch, pers. comm.).
    Mokinui (Big Moggy) Is. (Moggy Islands)
    An attempt to remove Pacific rats (Rattus exulans) from Mokinui Island (86 ha) has been carried out in 2006 (D. Agnew, pers. comm.).
    Mokohinau Islands (North Island)
    Pacific rats were removed from all islands in this group except Fanal Island in 1990. They were eradicated from Fanal Island in 1997.
    Mokolii is.
    An attempt has been made to eradicate Pacific rats (Rattus exulans) from Mokolii (1.5 ha), using diphacinone.
    Mont Panié
    A three year feasibility project initiated in 2003 by pest control specialists from the Invasive Species Specialist Group (ISSG, IUCN) has focussed on the 5000 hectare Mont Panié Botanical Reserve and has investigated the control of pest mammals in north-eastern New Caledonia. In 2004 the project control techniques focusing on feral pigs and rats were investigated. During September and October 2005 an intensive rat trapping and field trial programme was conducted at a 100 hectare site at Thoven and local people were trained in rat trapping and monitoring. Both the Black rat (Rattus rattus) and the Pacific rat (Rattus exulans) were controlled at target levels. Results from the investigations and trials suggest there is potential to effectively control a range of pest mammals on Mont Panié.
    Motu To'u Is. (Suwarrow (Suvarov) Atoll)
    An eradication programme of Pacific rats (Rattus exulans) was attempted in 2003 by Pacific Expeditions Ltd. The plan was to use a minimum of poison; hence, one hand broadcast application of brodifacoum (20ppm) at a rate of 2kg/ha was conducted. In a return visit in June 2004 rats were observed. It is clear from this experience that one application of such a low amount of bait is not sufficient in an island with such a high coconut crab population (G. Wragg, pers. comm.).
    Motuara Is.
    The Pacific rat (Rattus exulans) was eradicated from Motuara Island (59 ha) between 1991 and 1993. The programme was led by W. Cash, and used brodifacoum (Cash and Gaze, 2000; Thomas and Taylor, 2002; D. Veitch, pers. comm.).
    Motu-o-ari Is.
    An attempt to eradicate the Pacific rat (Rattus exulans) from Mout-o-ari was carried out in 2003, in a programme undertaken by Pacific Expeditions Ltd (led by G. Wragg). The eradication attempt used one hand broadcast application of brodifacoum (20ppm, 3kg/ha). Eradication has not yet been confirmed (G. Wragg, pers. comm.).
    Motuopao Is.
    The Pacific rat (Rattus exulans) was eradicated from Motuopao Island (30 ha) between 1989 and 1992, using brodifacoum (D. McKenzie, pers. comm.; Thomas and Taylor, 2002).
    Motupapa Is. (North Island)
    The Pacific rat (Rattus exulans) was eradicated from Motupapa Island (2 ha) in 1991.
    New Zealand
    The Department of Conservation (New Zealand) has successfully eradicated Pacific rats (and other rodents) from a number of offshore islands and plans to pursue eradication for all fifteen islands under its administration. Various methods have been used to eradicate rodents from offshore islands including trapping, 1080 and talon-type baits. Recent advances, including the development of more effective anticoagulant poisons and new application methods, mean it is now possible to consider rodent eradication operations on larger islands. The Department, health and regional authorities are involved in poisoning operations to ensure risk to humans, the environment and non-target species is minimised (DOC). A strategy for Pacific rats management has been produced (DOC, 1995; in Atkinson and Towns, 2001) which aims to: 1) Eradicate or exclude Pacific rats from islands where there is a need to manage or restore indigenous species or ecosystems, 2.) Further evaluate the impacts of Pacific rats on indigenous flora and fauna, 3.) Consult with tangata whenua, community groups and other interested parties in managing or restoring indigenous species or ecosystems on islands occupied by Pacific rats and 4.) Allow, and where appropriate support, the collection for research purposes of live and/or dead Pacific rats prior to any eradication.

    Towns and Broome (2003) outline the history of rat eradications in New Zealand.

    Nu’ulua
    Both Nu’utele and Nu’ulua have steep terrain which makes manual baiting for rats difficult and dangerous. There has been a proposal to carry out an aerial drop of grain-based baits containing the brodifacoum on both islands with provision to ground-lay extra baits in any gaps and in high rat/crab density areas if required. A project plan is currently being developed by Dave Butler (David Butler Associates Ltd) in consultation with PII (Pacific Invasives Initiative) staff. Opportunities to combine rat and ant management are being considered.
    Nu’utele
    Both Nu’utele and Nu’ulua have steep terrain which makes manual baiting for rats difficult and dangerous. There has been a proposal to carry out an aerial drop of grain-based baits containing the brodifacoum on both islands with provision to ground-lay extra baits in any gaps and in high rat/crab density areas if required. A project plan is currently being developed by Dave Butler (David Butler Associates Ltd) in consultation with PII (Pacific Invasives Initiative) staff. Opportunities to combine rat and ant management are being considered.
    Nukulaelae Is.
    Mongooses were introduced about 1950 (from Fiji) in an attempt to control rats, but they died out.
    Nukuwaiata (Inner Chetwode) Is. (Chetwode Islands)
    The Pacific rat (Rattus exulans) was eradicated from Inner Chetwode between 1993 and 1995. The eradication was achieved using brodifacoum and trapping (Brown, 1997; B. Simmons, pers. comm.); D. Veitch, pers. comm.).
    Oeno Is.
    The Pacific rat (Rattus exulans) was eradicated from Oeno Island in 1997, in a programme undertaken by Wildlife Management International Ltd (led by Brian Bell). The eradication was achieved by hand broadcasting brodifacoum (20 ppm) (B. Simmons, pers. comm.; G. Wragg, pers. comm.).
    Oeno Is.
    Rats were successfully eradicated from Ducie and Oeno in 1997 (Brooke, 1998 in Varnham, 2006). Action being considered/required includes total eradication from Pitcairn, and to keep Ducie and Oeno rat-free (Brooke, 1998 in Varnham, 2006; Brooke and Trevelyan, 2003 in Varnham, 2006) and eradication from Henderson (Hilton, 2004 in Varnham, 2006).
    Ohinau Islands
    An attempt to remove the Pacific rat (Rattus exulans) from Ohinau Island (43 ha) was carried out in 2005 (J. Roxburgh, pers. comm.).
    Patauhinu Is.
    Pacific rats (Rattus exulans) were eradicated from Putauhinu Island in August 1997 to prepare it for the translocation of a fernbird Bowdleria punctata wilsoni (see Bowdleria punctata in IUCN Red List of Threatened Species) population from Codfish Island. The eradication was carried out using a single aerial bait drop of 12 kg/ha of Talon 20P bait containing brodifacoum. It was done during winter as this is when rat numbers are at their lowest. After two years there had been no sign of rats, and the Pacific rats were declared eradicated. The vegetation is recovering, and invertebrate, bird and lizard species appear to be increasing. Quarantine restrictions must be strictly enforced to prevent reinvasion.
    Pearl Is. (Stewart Is.)
    An attempt to remove the Pacific rat (Rattus exulans) was from Pearl Island (512 ha) was carried out in 2005 (B. Beaven, pers. comm.).
    Phoenix Is.
    A PII (Pacific Invasives Initiative) supported project was organised to determine the status and distribution of invasive alien species on selected islands in the Phoenix Island Group. Methods used to assess invasive species numbers included rodent and cat trapping, observation of potential invasives, (eg. mynas) and collection of exotic ants and plants. As a result of this survey priorities have been identified for eradication of the invasive mammals.
    Pitcairn
    An attempt was made to eradicate the Pacific rat (Rattus exulans) from Pitcairn Island between 1997 and 1998, but was not successful. The attempt was undertaken by Wildlife Management International Ltd (led by Brian Bell), and involved hand broadcast of brodifacoum (20ppm) (G. Wragg, pers. comm.).
    Pitcairn
    Two eradication attempts on Pitcairn have failed. A third attempt to eradicate rats from Pitcairn is being considered, using a helicopter to drop bait in less accessible areas (Brooke and Trevelyan, 2003 in Varnham, 2006). Action being considered/required includes total eradication from Pitcairn, and to keep Ducie and Oeno rat-free (Brooke, 1998 in Varnham, 2006; Brooke and Trevelyan, 2003 in Varnham, 2006) and eradication from Henderson (Hilton, 2004 in Varnham, 2006).
    Pribilof Islands
    A prevention programme was set up in 1993 to prevent the accidental introduction of rats. This consists of trap and poison stations, community education, outreach to vessels, local shipwreck response capabilities, and regulations. Several rats have been killed on the St Paul docks but there is no evidence of establishment. Snap traps appear to be more effective than poison, but cause minor loss to non-target species.
    Puangiangi Is.
    The Pacific rat (Rattus exulans) was eradicated from Puangiangi Island (69 ha) in 1999, using brodifacoum. The eradication programme was led by P. Gaze (B. Simmons, pers. comm.; B. Cash, pers. comm.; J. Russell, pers. comm.).
    Putauhinu Is.
    The Pacific rat (Rattus exulans) was eradicated from Putauhinu Island (145 ha) in 1997, in a programme undertaken by the Department of Conservation (led by P. McClelland). Eradication was achieved by an aerial application of brodifacoum (20ppm). Quarantine on Putauhinu is enforced by the island owners. They have a vested interest in it remaining rat-free because they harvest seabirds there (McClelland, 2002; D. Veitch, pers. comm.; J. Russell, pers. comm.).
    Raoul Is. (Kermadec Islands)
    The Pacific rat (Rattus exulans) was eradicated from Raoul Island in 2002, in a programme undertaken by the Department of Conservation (led by M. Ambrose). The eradication was achieved with two aerial applications of brodifacoum, five days apart. DoC's Island Biosecurity SOP remains in place to prevent reinvasion of the island occurring (J. Russell, pers. comm.).
    Rose Atoll
    Pacific rats (Rattus exulans) were considered having a significant impact on the biodiversity and ecosystem of Rose Island, Rose Atoll. Rose Atoll is a nesting site of the 'critically endangered' hawksbill turtle (see Eretmochelys imbricata in IUCN Red List of Threatened Species), the endangered green sea turtle (see Chelonia mydas in IUCN Red List of Threatened Species), and several species of migratory seabirds. An eradictaion programme was undertaken during 1990-91. Talon-G in a product called WeatherBlok was used as bait on Rose Island and proved to be highly successful. A remnant population of rats was a major concern and an eradication operation was planned using bromethalin as bait as a follow up to WeatherBlok. For details on the eradication project please see Ohashi & Oldenburg, 1992.
    An attempt has been made to eradicate the Pacific rat from Rose Atoll (6 ha), using either brodifacoum or bromethalin, and trapping (Island Conservation and Ecology Group, 2004).
    Rurima Is.
    The Pacific rat (Rattus exulans) was eradicated from Rurima Island (4.5 ha) in eradication trials carried out in 1983-1984, in a programme led by I. McFadden (McFadden and Towns, 1991; McFadden, 1992). 1080-impregnated kibbled maize was used dispensed from gravity fed silos, but the rats did not take the bait, perhaps because of the taste of dyes used in manufacture. This was replaced with undyed kibbled maize impregnated with bromadiolone. Eradication was probably achieved within three months (Thomas and Taylor, 2002).
    Stacks B-G, I, J
    The Pacific rat (Rattus exulans) was eradicated from Stacks B-G, I and J in the Mokohinau Group between 1990 and 1991, using bromadiolone (McFadden, 1992; 1994; D. Veitch, pers. comm.; J. Russell, pers. comm.).
    Stanley (Kawhitihu) Is. (Mercury Islands)
    The Pacific rat (Rattus exulans) was eradicated from Stanley Island between 1991 and 1992 in a programme undertaken by the Department of Conservation (led by I. McFadden). The eradication was achieved using an aerial application of brodifacoum (Buckle and Fenn, 1992; Towns et al., 1993; J. Russell, pers. comm.; Atkinson and Taylor, 1991).
    Stewart Is.
    Hickson et al. (1986) describes the use of rat poison at four places near Port Pegasus in southern Stewart Island. These places are visited by fishing boats en route to the Snares Islands, an internationally significant, rodent-free nature reserve in the subantarctic. Controlling rats in remote anchorages is expensive and logistically difficult, so it is important to determine whether or not poisoning significantly reduces the probability of rats boarding boats and how resources should best be deployed.

    Poison was used at remote anchorages of southern Stewart Island in spring and summer of 1984/85 to reduce the likelihood of ship rats (Rattus rattus), Norway rats (R. norvegicus) and kiore (R. exulans) boarding fishing boats heading for the Snares Islands. Poison baits were removed at successively slower rates, probably because poisoning had reduced rat numbers. The effectiveness of poisoning was tested by (i) live-capturing and tracking marked rats at a simulated anchorage near Halfmoon Bay, (ii) poisoning there as in southern Stewart Island, and (Hi) monitoring the survival and responses of the marked population. Population density approximated 2.0-2.5 ship rats per hectare before poisoning. The minimum monthly home range of ship rats averaged 0.54 ha (mean range length 142 m), which is much larger than previously recorded for ship rats in New Zealand. Neither Norway rats nor ship rats were restricted to the shoreline or along creeks. Poisoning caused a 93% reduction in an index of rat numbers in a 0.69 ha poisoning zone over 16 days, and a 76% reduction over the larger 10.4 ha effective trapping area including the poison zone. Poisoning reduces the risk of rats boarding boats, and can protect endangered plants and animals on infested islands (Summary from Hickson et al. 1986).

    Swains Is.
    In 1941 before poisoning it was estimated that 20% of the coconut crop was damaged by rats.
    Teanaone Is. (Gambier Islands)
    An attempt was made to eradicate the Pacific rat (Rattus exulans) from Teanaone and Tepapuri in the Gambier archipelago in 2003. The eradication attempt was undertaken by Pacific Expeditions Ltd (led by Graham Wragg), and involved hand broadcast of brodifacoum (20 ppm) at 3 kg/ha. Non-target impacts included the death of some pigs. Eradication of Rattus exulans is yet to be confirmed (G. Wragg, pers. comm.).
    Tepapuri Is. (Gambier Islands)
    An attempt was made to eradicate Rattus exulans from Teanaone and Tepapuri in the Gambier archipelago in 2003. The eradication attempt was undertaken by Pacific Expeditions Ltd (led by Graham Wragg), and involved hand broadcast of brodifacoum (20 ppm) at 3 kg/ha. Non-target impacts included the death of some pigs. Eradication of Rattus exulans is yet to be confirmed (G. Wragg, pers. comm.).
    Tinui Is. (Rangitoto Group)
    The Pacific rat (Rattus exulans) was eradicated from Tinui Island (95 ha) in 1999, using brodifacoum (led by P. Gaze) (B. Simmons, pers. comm.; B. Cash, pers. comm.; J. Russell, pers. comm.).
    Tiritiri Matangi Is. (North Island)
    Pacific rats were eradicated from Tiritiri Matangi Island in September 1993, using an aerial application of Talon 20P pellets containing brodifacoum. During the bait drop, endangered non-target species such as the North Island takahe (see Porphyrio mantelli in IUCN Red List of Threatened Species) and brown teal or the Auckland Island teal (see Anas aucklandica in IUCN Red List of Threatened Species) were kept in an enclosure. There were some non-target effects on other species such as pukeko (Porphyrio melanotus), but since the eradication these populations have recovered to pre-eradication levels. No rodent sign has been detected since the eradication. 51 Rentokil bait stations containing bromadiolone bait are maintained on the island at potential landing places (Veitch, 2002).
    Since the eradication, there has been a general increase in native bird numbers and an increase in the abundance of ripe fruits and seeds which were previously eaten by rats (Graham and Veitch., 2002). Monitoring carried out post-eradication showed an increase in invertebrate species, especially larger species such as ground weta (Orthoptera: Anostostomatidae) and several species of prowling spider (Araneae: Miturgidae) (Green, 2002).
    Vahanga Atoll (Tuamotu Islands)
    The Société d’Ornithologie de Polynésie (SOP) MANU proposes to eradicate the Pacific rat from Vahanga Atoll with the support of the PII (Pacific Invasives Initiative). In 2000 a rat eradication was attempted on Vahanga but was unsuccessful. The eradication of the Pacific rat from Vahanga will not only provide for the recovery of threatened species, but also provide a buffer to the existing predator-free Tenararo.
    Vanua Levu Is.
    Mongooses were introduced in 1883 to control rats in sugarcane.
    Viti Levu Is.
    Mongooses were introduced in 1883 to control rats in sugarcane.
    Viwa Is.
    The removal of cane toads (Bufo marinus), rats, cats and dogs these invasive species from Viwa Island would benefit a range of other native species, including the banded iguana (see Brachylophus fasciatus in IUCN Red List of Threatened Species), Pacific boa (Candoia bibroni), and several species of gecko and skink. In addition to the biodiversity benefits, this project is expected to have several socio-economic benefits to the people on Viwa. These include an increased agricultural harvest, improved health and sanitation (domestic water supply and disposal), ecotourism and employment opportunities, and finally cultural pride for the Viwa Island people (104 people live on the island).

    The Viwa Stakeholder Committee (made up of local people, government officials and eradication experts) decided the vertebrate pest eradication should be conducted first with progress carefully monitored as the operation proceeds. During the vertebrate eradication, cane toad eradication techniques will be tested and refined. The mammalian eradication operation will help demonstrate eradication techniques to the villagers and will determine if the island eradication team can maintain a long-term eradication project around day-to-day village life and tasks. It will also remove any of potential interference of Pacific rats (Rattus exulans), cats (Felis catus) and dogs (Canis lupus) from the cane toad eradication.

    Whakaterepapanui Is.
    The Pacific rat (Rattus exulans) was eradicated from Whakaterepapanui Island (74 ha) in 1999 (Atkinson and Taylor, 1991). The eradication was led by Peter Gaze, and used brodifacoum (B. Cash, pers. comm.; J. Russell, pers. comm.).
    Whatupuke Is. (Chicken Islands)
    Rattus exulans was eradicated from Whatupuke Island (102 ha) between 1993 and 1997, in a programme led by K. Hawkins (Atkinson and Taylor, 1991; McFadden, pers. comm.).


         Management Resources/Links

    3. Brooke, M. de L. 1995. The breeding biology of the gadfly petrels Pterodroma spp. of the Pitcairn Islands: characteristics, population sizes and controls. Biological Journal of the Linnean Society 56: 213-231.
            Summary: This reference by Mike Brooke describes the total loss of all chicks of Kermedaec petrels on Henderson Island to Pacific rat predation.
    5. Cunningham, D.M. and Moors, P.J., 1993. Guide To The Identification And Collection Of New Zealand Rodents. Department of Conservation, NZ.
            Summary: A Guide To The Identification And Collection Of New Zealand Rodents, information on trapping methods.
    7. Doty, R. E. 1945. Rat control on Hawaiian sugar cane plantations. Hawaiian Planters Record 49(2): 71–241.
    8. Gerber, G. 1997. Nesting Behavior of the Little Cayman rock iguana, Cyclura nubila caymanensis. Joint Annual Meeting, American Society of Ichthyologists and Herpetologists/Herpetologists League/Society for the Study of Amphibians and Reptiles. University of Washington, Seattle, U.S.A.
    10. IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4.
            Summary: The IUCN Red List of Threatened Species provides taxonomic, conservation status and distribution information on taxa that have been globally evaluated using the IUCN Red List Categories and Criteria. This system is designed to determine the relative risk of extinction, and the main purpose of the IUCN Red List is to catalogue and highlight those taxa that are facing a higher risk of global extinction (i.e. those listed as Critically Endangered, Endangered and Vulnerable). The IUCN Red List also includes information on taxa that are categorized as Extinct or Extinct in the Wild; on taxa that cannot be evaluated because of insufficient information (i.e. are Data Deficient); and on taxa that are either close to meeting the threatened thresholds or that would be threatened were it not for an ongoing taxon-specific conservation programme (i.e. are Near Threatened).
    Available from: http://www.iucnredlist.org/ [Accessed 25 May 2011]
    11. IUCN/SSC Invasive Species Specialist Group (ISSG)., 2010. A Compilation of Information Sources for Conservation Managers.
            Summary: This compilation of information sources can be sorted on keywords for example: Baits & Lures, Non Target Species, Eradication, Monitoring, Risk Assessment, Weeds, Herbicides etc. This compilation is at present in Excel format, this will be web-enabled as a searchable database shortly. This version of the database has been developed by the IUCN SSC ISSG as part of an Overseas Territories Environmental Programme funded project XOT603 in partnership with the Cayman Islands Government - Department of Environment. The compilation is a work under progress, the ISSG will manage, maintain and enhance the database with current and newly published information, reports, journal articles etc.
    14. Moors, P. J., Atkinson, I. A. E. and Sherley, G. H. 1992. Reducing the rat threat to island birds. Bird Conservation International 2: 93–114.
    15. Morrell et. al. 1991. Eradication of Polnsin Rat (Rattus exulans) from Rose Atoll Nation Wildlife Refuge, American Samoa. DMWR Biological Report Series No. 20
    23. Tobin, M. E. 1994. Polynesia rats. In Hygnstrom, S. E., Timm, R. M. and Larson, G. E. (eds.) Prevention and Control of Wildlife Damage. USA.
    25. Towns, D. R. 1991. Response of lizard assemblages in the Mercury Islands, New Zealand, to removal of an introduced rodent: the kiore (Rattus exulans). Journal of the Royal Society of New Zealand 21: 119–136.

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