In 2016, the New Zealand Government announced a policy to rid the country of key introduced predators (possums (Trichosurus vulpecula), ship rats (Rattus rattus), Norway rats (R. norvegicus) and mustelids (Mustela spp.)) by 2050. An interim goal under this policy is to remove all mammalian predators (the key species as well as mice (Mus musculus), kiore (R. exulans), cats (Felis catus), pigs (Sus scrofa) and hedgehogs (Erinaceus europaeus)) from island nature reserves by 2025.
In 2003, a review of how introduced mammals were managed as pests in New Zealand was published. Since then trends for the control of these mammals include moves from pest-by-pest prioritisation towards site-based and multiple-pest management, extension of large-scale aerial control of predators to include beech forests, increasing intensive management of sites by private and non-government agencies, and increasing effort by regional councils and managers of vectors of bovine tuberculosis.
Vertebrate pest management on Macquarie Island has removed five vertebrate species since 1988; weka (Gallirallus australis scotti), cats (Felis catus), rabbits (Oryctolagus cuniculus), ship (black) rats (Rattus rattus) and house mice (Mus musculus). The latter three were eradicated in a combined eradication operation that commenced in 2006 and was declared successful in 2014. Eradication planning for removal of rabbits, rats and mice took about five years, with implementation another three years.
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.
Ecological research into rodents in New Zealand commenced in the late 1940s with the creation of the Animal Ecology Section, Department of Scientific and Industrial Research (DSIR). Field surveys of rodents were backed by study skins and skeletal material. Supplemented by specimens from the Wildlife Service and the public, these accrued over the next 45 years laying the foundation for our present knowledge of rodent distribution. In 1951, J. S. Watson joined the DSIR from the Bureau of Animal Population, Oxford, and brought much needed experience in rodent biology and control.
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 by rat eradication. Petrel colony growth is mediated by both positive and negative density dependence, although it is unclear if, or how, density dependence will affect patterns in post-eradication colony recovery.
Invasive species have been identified by the Convention on Biological Diversity as a significant threat to biodiversity. Conservation managers often lack tools for addressing uncertainty about the control intensity required to achieve cost-effective management of invasive species. We describe a modelling approach for informing the spacing of control-device lines given the availability of home-range data. To demonstrate its utility, we used data on stoats (Mustela erminea), an introduced mammalian predator responsible for the decline of endemic birds in New Zealand.
Five-minute bird counts were made on Rangitoto Island in 1998 and 1999, 8 and 9 years after the start, and 1 and 2 years after the completion of a 7-year programme that resulted in eradication of the introduced brushtail possum (Trichosurus vulpecula) and brushtailed rock wallaby (Petrogale penicillata). These were compared with counts made in 1990 (immediately before the start of the programme), to assess whether bird species diversity and abundance had increased as a result of the eradications. The number of bird species detected in 1998/99 was similar to 1990.
Aerial poisoning using Talon(R) 7-20 baits (active ingredient 20 ppm brodifacoum) was carried out on Motuihe Island, Hauraki Gulf, during the winter of 1997. The operation aimed to eradicate Norway rats (Rattus norvegicus) and house mice (iMus musculus) and to reduce rabbit (Oryctolagus cuniculus) numbers significantly. We studied the diet of feral house cats (Felis earns) before the operation, then monitored the impact of the operation on them to determine whether secondary brodifacoum poisoning caused a reduction in their numbers.
Norway rats were eradicated on bush-covered Hawea Island (9 ha) in Breaksea Sound, using the anticoagulant rodenticide "Talon 50 WB" (brodifacoum). The work was done as a conservation measure and to evaluate the feasibility and costs of eradicating rodents quickly from islands. The 50-100 rats present were eradicated in about two weeks by applying a simple strategy that took full account of the characteristics of the poison, he environment, and the behaviour of the target species.