New Zealand aims to eradicate possums (Trichosurus vulpecula) and ship rats (Rattus rattus) nationally by 2050. This aim will require more effective tactics for locally eliminating these pests. Therefore, we explored whether possums and rats could be eliminated from large areas using pre-feeding and two applications of sodium fluoroacetate (1080) bait spaced a few months apart.
We used a long-term replicated before-after control-impact (BACI) sampling design to monitor the effect of aerial 1080 possum-control operations on common forest bird populations. Paired treatment and non- treatment sites in the Rolleston Range (East Coast, South Island) and Alexander Range (West Coast, South Island) were monitored once before 1080 treatment during winter 2012 and for three successive summers afterwards. Mammals (possums Trichosurus vulpecula, rats Rattus spp.
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.
Invasive rats can be capable swimmers, able to cross substantial water channels of hundreds of metres to colonise islands. This dispersal capability puts at risk islands close enough to infested areas for rats to reach unassisted. When reinvasion rates are high, biosecurity surveillance on islands might be supported by source population control to prevent re-establishment. However, biosecurity surveillance can only detect reinvading rats when they arrive and the source of reinvading rats might remain unknown.
The ship rat invasion of Big South Cape Island/Taukihepa in the 1960s was an ecological catastrophe that marked a turning point for the management of rodents on offshore islands of New Zealand. Despite the importance of this event in the conservation history of New Zealand, and subsequent major advances in rodent eradication and biosecurity, the source and pathway of the rat invasion of Big South Cape Island has never been identified.
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.
One of the criteria for an effective bird repellent in a pest management context in New Zealand is that possum (Trichosurus vulpecula) and ship rat (Rattus rattus) kills remain high where repellents are used in poison baits. Repellents were used in baits applied within different treatment blocks as part of a large aerial 1080 operation in November 2013 near Haast on the West Coast of the South Island of New Zealand.
New Zealand robins are thought to be vulnerable to poisoning by sodium fluoroacetate (1080), because individual birds found dead after aerial pest control operations have tested positive for 1080. We investigated the impacts of an aerial 1080 operation (preceded by non-toxic prefeeding) to control brushtail possums (Trichosurus vulpecula) on the survival and breeding success of a robin population at Silver Peaks, Dunedin environs, South Island, New Zealand. We monitored the survival of individual marked robins and their nesting success before and after the 1080 application.
Chew-track-cards (CTCs) are potentially a cost-effective way to estimate the relative abundance of invasive rats and possums in New Zealand, but previous research suggested that their high sensitivity may limit use to low-density populations. Using a short two-night deployment period, we compared CTC indices of rat and possum abundance with a footprint tracking rate (RTR) index of rat abundance and a wax tag bite rate index (WTI) of possum abundance in 11 forest remnants that varied widely in rat and possum abundance (RTR and WTI of 0–100% over two nights).
The seasonal diet of ship rats in a stand of lowland podocarp-rata-broadleaf forest in North Island, New Zealand, was studied from analysis of 173 stomachs, 46 fresh droppings and 10 feeding trials. Arthropods, particularly tree wetas (Order Orthoptera), were the main foods in spring and summer, while drupes, berries and nuts predominated in autumn and winter. Birds were not an important food. Seasonal variations in the diet were related to the seasonal abundance of these foods in the forest
