Abstract
Ferrets (Mustela furo) are introduced pests in New Zealand, and there is an urgent need for an effective toxic bait for their control. Fish paste was identified as a potential bait, and sodium mono‐fluoroacetate (1080) and diphacinone as potential toxicants. The acute oral LD50 of 1080 was already known. The acute oral LD50 of diphacinone in fish paste to ferrets was determined as 21.4 mg/kg. In a field trial with 0.015% 1080 in fish paste, in February (late summer) 1997, all four radio‐collared ferrets detected in the poison area more than 20% of the time died, and their muscle tissue contained 0.20–1.86 mg/kg of 1080. In a field trial with 0.03% diphacinone in fish paste, in March (early autumn) 1997, all 19 radio‐collared ferrets detected in the poison area more than 20% of the time died. The livers of 17 ferrets analysed contained 2.0–46.0 mg/kg of diphacinone. In a second field trial with 0.03% diphacinone in fish paste, in July (mid winter) 1997, only five (29%) of 17 radio‐collared ferrets died. The livers of four ferrets analysed contained 3.8–10.0 mg/kg of diphacinone. It was not possible to determine whether the lower success in the second diphacinone field trial was a result of season or site differences because the trials were unreplicated. Nevertheless, as a consequence of these results, fish‐paste bait containing 0.03% diphacinone is now commercially available in New Zealand.