In New Zealand, five of the six endemic bird species that breed primarily in South Island braided river beds are classed as threatened. A major cause of decline for these species is predation by introduced mammals, and predator-trapping programs are undertaken in the braided rivers of the Mackenzie Basin to protect them. Trapping programs carried out between September 1997 and April 2001 provided the opportunity to investigate predator diet from the gut contents of 375 cats (Felis catus), 371 ferrets (Mustela furo) and 86 stoats (Mustela erminea). As a percentage frequency of occurrence of the main prey items, cat diet consisted of lagomorphs (present in 70% of guts), birds (in 47%), lizards (30%) and invertebrates (36%). Ferret diet consisted of lagomorphs (69%) and birds (28%). Stoat diet consisted of lagomorphs (50%), birds (51%), lizards (21%) and invertebrates (23%). The frequency of occurrence of birds in all three predators was higher in the spring/summer of 1997 – immediately after rabbit haemorrhagic disease (RHD) was introduced – than in any other previous diet study on these braided rivers. This suggests that RHD did lead to increased predation pressure on birds, at least in the short term.

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An intensive predator trapping programme was implemented in the upper Waitaki Basin, New Zealand from October 1997 to January 1998. The aim of the programme was to prevent increased predation on vulnerable braided river fauna following decline in rabbits due to rabbit haemorrhagic disease (RHD). Fourteen sites were trapped using a standardised method, and trap catch results provided a relative index of predator abundance. In 101 650 trapnights, 1067 hedgehogs, 328 ferrets, 196 cats, 96 rats and 69 stoats were caught. Predator guilds varied among sites and guild composition tended to change through time; for example, stoat and rat catch rates increased. Cat and ferret catch rates increased in the last month of trapping, which suggested that juvenile dispersal and immigration by adult predators from surrounding areas were high. This study provides baseline information on predator abundance and predator guilds in the upper Waitaki Basin against which future trapping programmes can be compared, in order to assess changes in predator populations since the introduction of RHD.