Comparative Effects of Brodifacoum on Rats and Possums

The anticoagulant brodifacoum is widely used overseas as a rodenticide, and in New Zealand to control rodents and brushtail possums (Trichosurus vulpecula). The efficacy, behavioural and pathological changes and times to death were compared between Norway rats (Rattus norvegicus) and brushtail possums poisoned with brodifacoum. Caged animals were given brodifacoum in wax or cereal baits, observed for signs of toxicosis and changes in behaviour, then autopsied after death. Brodifacoum caused haemorrhaging and death in both species, and although each showed marked changes in behaviour and pathology, they differed in character, time of onset and duration. Results may be explained in part by species differences in behaviour and half-lives of blood clotting factors.