The Argentine ant, Linepithema humile, was found established in New Zealand in 1990. During summer 2001/2002 the spread of Argentine ants from urban environments into native habitats was investigated. During an initial large-scale survey around the northern cities of Auckland and Whangarei, Argentine ants were observed at 35 of 211 sites. Eight sites in Auckland were subsequently surveyed in greater detail to determine the extent of movement by Argentine ants into native habitats.
In 1996 an eradication operation against two species of rats (Rattus norvegicus and R. exulans was conducted on Kapiti Island (1965 ha) and its small offshore islands. Trials with non-toxic baits had been carried out to help determine the risks to non-target species, and research was undertaken to collect baseline data for measuring the response of vegetation, invertebrates, reptiles and birds to the removal of rats.