poisoning

To establish whether poisoning programs affect non-target density, the null hypothesis that density does not decline on poisoned sites needs to be tested. However, where no statistically significant reduction in density is found, there is some probability that a biologically significant reduction has been overlooked. The probability that such an error has occurred (a Type 2 error) depends on the effect poisoning has on non-target density, the precision with which the reduction is assessed, and the number of poisoning operations sampled.

The density of rabbits (Oryctolagus cuniculus) in the modified tussock grasslands of the Mackenzie Basin, South Island, New Zealand, in August-September 1991 was determined within 26 I-ha quadrats spread over 1000 ha. The area was poisoned with 1080- carrot baits and dead and live rabbits counted. The overall kill rate was 93%. Wide variability in rabbit densities amongst the quadrats was correlated with burrow density, but vegetation was not a significant predictor of rabbit numbers. High density quadrats were not all spatially clumped together.

A 55 ha remnant of coastal native forest at Wenderholm Regional Park (near Auckland) was selected as the site for a pilot experiment to test if rat control could yield measurable benefits in increased productivity of New Zealand pigeons. Talon 50WB poison baits were used to reduce rat numbers over the summer of 1992-93. Pigeon breeding success was significantly higher (5 fledglings from 11 nests) than in preceding summers without rat control (no fledglings from 27 nests).

This paper describes the impact of nine poison operations on ship rats in four areas (35 ha to 3200 ha) of North Island forest. Poisoning with 1080, brodifacoum, or pindone killed 87- 100% of rats, based on trapping and tracking-tunnel indices. Rat populations took 4-5 months to recover. Operations to protect nesting birds should therefore coincide with the onset of nesting and be rePeated each year, although not necessarily with the same methods.

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.

A knowledge of the sensitivity of the brushtail possum (Trichosurus vulpecula) to 1080 poison is important as a basis for planning effective control campaigns. This study assesses the effects that experimental procedure may have on determining the LD50 of 1080 for brushtail possums and reports on the variation in sensitivity within and between different populations of the species in Australia, where it is indigenous. LD50s obtained ranged from 0.39–0.92 mg kg-1, with 95 % confidence limits of from 0.29–1.20 mg kg-1.

The control of introduced mammalian predators has become a standard response to protecting the viability of threatened wildlife species on oceanic islands. However, examples of successful outcomes of integrated pest control in forests are few. We investigated the efficacy of a pest control programme in the Landsborough Valley, New Zealand, during 1998–2009, which used continuous trapping to control mustelids and pulsed aerial application of the toxin 1080 to control rats (Rattus spp.) and brushtail possums (Trichosurus vulpecula).