Six years of intensive pest mammal control at Trounson Kauri Park, a Department of Conservation “mainland island”, June 1996—July 2002

Abstract

Trounson Kauri Park is a 445‐ha fragment of kauri‐podocarp forest located in western Northland, New Zealand, and is one of a series of “mainland island” ecosystem restoration projects managed by the Department of Conservation. One of the main objectives at Trounson is to reduce introduced mammalian pest numbers to a level that would allow recovery of those native species still present in the park and allow the reintroduction of local or regionally extinct species. Brushtail possums (Trichosurus vulpecula) and rodents (ship rats, Rattus rattus, Norway rats, R. norvegicus, and mice, Mus musculus) were targeted in poison baiting operations using 1080, various anticoagulants, cholecalciferol or cyanide pellets laid in bait stations within the park. These operations suppressed possum and rat numbers to low levels, but mouse numbers were reduced only for short periods. The reduction in possum and rat numbers allowed significant seasonal increases in kukupa (New Zealand wood pigeon, Hemiphaga novaeseelandiae) abundance. Feral cats (Felis catus) and mustelids (stoats, Mustela erminea, weasels, M. nivalis, and ferrets, M.furo) were trapped around the forest boundaries and at key locations within and around the park. The predator trapping consistently provided predation relief for North Island brown kiwi (Apteryx australis mantelli) chicks, which are extremely vulnerable to predation by stoats, such that enough survived in order to sustain and increase the size of the adult population. Attempts were made to reestablish breeding populations of North Island robins (Petroica australis longipes), North Island kokako (Callaeas cinerea wilsoni), and brown teal (Anas aucklandica chlorotis) (three species of locally extinct native birds) to Trounson, but these were only partially successful at best.