Use of brodifacoum baits in relation to the development and mitigation of bait-shyness in the brushtail possum

Abstract

Sub-lethal doses (0.25-0.40 mg/kg) of brodifacoum, delivered via pellet bait, did not lead to the subsequent development of bait shyness in possums. The difference, compared with other toxicants, is attributed to the slow mode of action of brodifacoum. Brodifacoum pellet baits were then presented to 1080-bait shy possums to determine if the shyness could be overcome. Although 3 possums (19%) did not eat bait on the first night it was presented, by the second night all possums ate baits. Generally consumption increased nightly until toxicosis began to reduce appetite after 14 days. Nevertheless, possums were unable to associate the illness with the brodifacoum bait, and most possums consumed bait to within 2 days of death, resulting in 75% mortality. To avoid both wasteful use of brodifacoum pellets and risks of environmental contamination, baits should be presented for no longer than 15 days, by which time it would be expected that all possums encountering baits would have consumed a lethal dose.