Hen eggs poisoned with sodium monofluoroacetate (1080) for control of stoats (Mustela erminea) in New Zealand

Abstract

Control of stoats (Mustela erminea) using sodium monofluoroacetate (1080) injected into hen eggs was investigated in pen and field trials. For captive stoats, the LD50 of 1080 in hen eggs was 0.49 mg/kg and the LD90 was 0.70 mg/kg. In a field efficacy trial using 1080‐poisoned hen eggs in bait stations, consumption of eggs was reduced by 91.9% in the poison area relative to the non‐poison area within 22 days. Video recordings showed stoats, a possum, and a kea approached bait stations, but only stoats entered and ate eggs. In subsequent live‐trapping, one stoat was caught in 91.5 trap nights (1.09/100TN) in the poison area and eight stoats in 101 trap nights (7.92/100TN) in the non‐poison area. Assuming stoat numbers in the two areas were similar before poison‐baiting (a reasonable assumption based on egg consumption rates), this represents an 86.2% reduction in the number of stoats in the poison area relative to the non‐poison area. Success should be even greater in management operations, because 1080‐poisoned eggs could be left in the field for longer. Further trials using live‐trapping or radio‐telemetry to monitor stoat survival are needed to substantiate these results.