Impact of large scale possum control for TB on North Island kokako populations

Large scale possum control operations — mostly using 1080 poison — in the central North Island should be good for kokako since the possum is potentially a serious competitor for food. But obviously this is true only if no or few kokako are themselves killed during the operation.

After a phase of research with non-toxic baits, we have monitored the survival of a total of 76 kokako through 7 1080 operations in 3 years. Two kokako disappeared during operations in a way so as to conform with criteria we established for accepting death by poisoning, although no corpses were found. The predicted mortality in future operations is 2.6% (95% confidence limits 0.32% - 9.34%). The likely benefit to kokako from the possum control is unknown.

The survival of 40-50 kokako through a cyanide/gin trapping operation is also being monitored this winter. Results may be available by the time of this Conference.