fjordland

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.

Eradication of rodent species from some offshore islands has proved to be an effective means of conserving native animal communities and restoring natural ecological processes on the islands. As methods of eradication differ fur different rodent species, a truthful monitoring method to detect species presence and relative density is essential for a successful eradication programme.

Rats were eradicated from Lady Alice Island (Northland, New Zealand) in October 1994, using aerially applied cereal-based bait containing brodifacoum. To determine the fate and non- target impact of brodifacoum, streams, soil, invertebrates, and birds were monitored for 7 months after the baits were applied. No brodifacoum was detected in any of the stream or soil samples. Brodifacoum was detected in cave weta found on baits, and in morepork and red-crowned parakeet liver tissue. Significant contamination of water and soil is unlikely after a single aerial application of brodifacoum baits.

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.