Secondary poisoning of stoats (Mustela erminea) at low mouse (Mus musculus) abundance in a New Zealand Nothofagus forest

Abstract

Two different brodifacoum (Talon 20 P™) poisoning regimes effectively killed 100% of resident radio-tagged stoats (Mustela erminea) by secondary poisoning in a New Zealand Nothofagus forest when mice (Mus musculus) were scarce. Resident possums (Trichosurus vulpecula) and ship rats (Rattus rattus) were also killed. The relative importance of different prey species as sources of poison for stoats has not been clearly identified but availability of poisoned prey will determine the efficacy of secondary poisoning in years of low prey abundance. Tracking tunnels did not accurately measure the decline in the stoat population and were probably influenced by immigrant stoats that were kill-trapped and contained high levels of poison. This study corroborates the findings of several other similar studies that secondary poisoning using brodifacoum effectively kills stoats.