Eradication Of Kiore (Rattus Exulans) from Double Island, Mercury Group In Northern New Zealand

Abstract

Kiore were eradicated on Double Island using two different methods. The larger islet was treated with one manual application of STORM 4 g wax block rat baits containing 0.005% by weight Flocoumafen, in October 1989. The smaller islet received one application of toxic kibbled maize (0.005% bromodialone by weight) after 4 nights prefeeding in November 1989. Kibbled maize was dispensed in silos. No sign of kiore has since been found during four visits to both islands. The cost per hectare for both methods were quite comparable. The nett cost for eradication on the larger islet (19 ha) was $310/ha, the smaller islet cost $432/ha. Both methods are considerably cheaper than the technique used to eradicate Norway rats (R. norvegicus) from Hawea Island. For future rodent eradication campaigns it is suggested that aerial applications of poisons may be made on all islands greater than 50 ha, and that size should be no barrier to rodent eradication. However, substantial non-target have been recorded when 1080 baits were broadcast aerially to control possum. Non-target kills of a similar magnitude may be experienced on larger and more sensitive islands.