Of the 31 species of exotic mammals that have current wild or feral populations confirmed in New Zealand, at least 25 are actively managed as pests in at least part of their range to reduce their impacts on biodiversity and production values. This paper summarises the current legal status of introduced mammals, the strategic and tactical options to manage them as pests, and their actual management by different agencies, both as pests and as resources. We then discuss some ways in which management agencies might better integrate their actions, record how much is invested in different types of research on the different species, and summarise the main types of problems the research aims to address.

This study aimed to quantify the changes in numbers and diet of stoats, weasels and ferrets following rat and possum poison operations in two podocarp‐hardwood forests between 1989 and 1995. Poison operations were classified according to their success in reducing rat numbers, and if they used an acute toxin (1080) or an anticoagulant (brodifacoum or pindone). Stoat catch rates followed the same seasonal patterns as rat footprint tracking rates, and stoat catch rates were positively correlated with rat catch rates. Rat numbers in spring had no significant relationship with the number of juvenile stoats caught in summer. Stoat catch rates did not vary significantly with poison‐operation type over a six month period, but all three successful anticoagulant operations resulted in lower stoat catch rates than did unsuccessful operations. Brodifacoum in bait stations may have lowered stoat numbers by secondary poisoning for the first 2–3 months, but thereafter there was no apparent effect. The sex ratio of stoats caught varied significantly amongst the poison operations. The fewest females were caught following anticoagulant operations. Stoat stomachs and intestines contained mostly rats, and some birds and mice. Weasels ate mostly mice, while ferrets predominantly ate lagomorphs and invertebrates. Male and female stoats ate similar proportions of rats, but females ate more mice. Both sexes, but particularly females, ate fewer birds in autumn and winter than in spring and summer. Stoats shifted between eating rats and birds, depending upon the abundance of rats. Thus successful rat‐poisoning operations resulted in higher bird consumption than unsuccessful ones. Combining the numerical and functional responses of stoats into a ‘bird predation index’ showed that stoats are likely to have the greatest effect on birds after successful 1080 poison operations. Diet shifts could not be demonstrated in weasels or ferrets because sample sizes were too small for quantitative assessments. The risk of increased predation pressure on birds from diet‐shifting by stoats must be balanced against the predation pressure on birds and other ecological impacts of rats and possums from different poison operations.