Daily activity of stoats (Mustela erminea), feral ferrets (Mustela furo) and feral house cats (Felis catus) in coastal grassland, Otago Peninsula, New Zealand

This radio-tracking study reports the daily activity rhythms in autumn and spring of 11 stoats (Mustela erminea) (9 male, 2 female), 20 ferrets (M.furo) (8 m, 12 f) and 11 feral house cats (Felis catus) (7 m, 4 f) resident on coastal grassland, Otago Peninsula, New Zealand. Activity rhythms differed markedly amongst individual stoats in autumn, but little amongst individual cats and ferrets in either season. Stoats were equally active day and night in autumn, but were more active at day than at night in spring. Cats showed moderate day activity, but were mainly active at night in both seasons. Ferrets showed low activity during daylight in autumn and were entirely nocturnal in spring. Overall, stoats were more active during daylight than cats or ferrets; and cats were more active during daylight than ferrets. Therefore, cats and especially stoats may pose the main predation threat to diurnal native species in New Zealand. Effective biological control of rabbits (Oryctolagus cuniculus) may effect the absolute abundance and daily activity of the predators, so is impossible to predict the overall impact of predation on diurnal and nocturnal native species.